1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis ----------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the implementation of the scalar evolution analysis
11 // engine, which is used primarily to analyze expressions involving induction
12 // variables in loops.
13 //
14 // There are several aspects to this library. First is the representation of
15 // scalar expressions, which are represented as subclasses of the SCEV class.
16 // These classes are used to represent certain types of subexpressions that we
17 // can handle. We only create one SCEV of a particular shape, so
18 // pointer-comparisons for equality are legal.
19 //
20 // One important aspect of the SCEV objects is that they are never cyclic, even
21 // if there is a cycle in the dataflow for an expression (ie, a PHI node). If
22 // the PHI node is one of the idioms that we can represent (e.g., a polynomial
23 // recurrence) then we represent it directly as a recurrence node, otherwise we
24 // represent it as a SCEVUnknown node.
25 //
26 // In addition to being able to represent expressions of various types, we also
27 // have folders that are used to build the *canonical* representation for a
28 // particular expression. These folders are capable of using a variety of
29 // rewrite rules to simplify the expressions.
30 //
31 // Once the folders are defined, we can implement the more interesting
32 // higher-level code, such as the code that recognizes PHI nodes of various
33 // types, computes the execution count of a loop, etc.
34 //
35 // TODO: We should use these routines and value representations to implement
36 // dependence analysis!
37 //
38 //===----------------------------------------------------------------------===//
39 //
40 // There are several good references for the techniques used in this analysis.
41 //
42 // Chains of recurrences -- a method to expedite the evaluation
43 // of closed-form functions
44 // Olaf Bachmann, Paul S. Wang, Eugene V. Zima
45 //
46 // On computational properties of chains of recurrences
47 // Eugene V. Zima
48 //
49 // Symbolic Evaluation of Chains of Recurrences for Loop Optimization
50 // Robert A. van Engelen
51 //
52 // Efficient Symbolic Analysis for Optimizing Compilers
53 // Robert A. van Engelen
54 //
55 // Using the chains of recurrences algebra for data dependence testing and
56 // induction variable substitution
57 // MS Thesis, Johnie Birch
58 //
59 //===----------------------------------------------------------------------===//
60
61 #define DEBUG_TYPE "scalar-evolution"
62 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
63 #include "llvm/Constants.h"
64 #include "llvm/DerivedTypes.h"
65 #include "llvm/GlobalVariable.h"
66 #include "llvm/GlobalAlias.h"
67 #include "llvm/Instructions.h"
68 #include "llvm/LLVMContext.h"
69 #include "llvm/Operator.h"
70 #include "llvm/Analysis/ConstantFolding.h"
71 #include "llvm/Analysis/Dominators.h"
72 #include "llvm/Analysis/LoopInfo.h"
73 #include "llvm/Analysis/ValueTracking.h"
74 #include "llvm/Assembly/Writer.h"
75 #include "llvm/Target/TargetData.h"
76 #include "llvm/Support/CommandLine.h"
77 #include "llvm/Support/ConstantRange.h"
78 #include "llvm/Support/Debug.h"
79 #include "llvm/Support/ErrorHandling.h"
80 #include "llvm/Support/GetElementPtrTypeIterator.h"
81 #include "llvm/Support/InstIterator.h"
82 #include "llvm/Support/MathExtras.h"
83 #include "llvm/Support/raw_ostream.h"
84 #include "llvm/ADT/Statistic.h"
85 #include "llvm/ADT/STLExtras.h"
86 #include "llvm/ADT/SmallPtrSet.h"
87 #include <algorithm>
88 using namespace llvm;
89
90 STATISTIC(NumArrayLenItCounts,
91 "Number of trip counts computed with array length");
92 STATISTIC(NumTripCountsComputed,
93 "Number of loops with predictable loop counts");
94 STATISTIC(NumTripCountsNotComputed,
95 "Number of loops without predictable loop counts");
96 STATISTIC(NumBruteForceTripCountsComputed,
97 "Number of loops with trip counts computed by force");
98
99 static cl::opt<unsigned>
100 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
101 cl::desc("Maximum number of iterations SCEV will "
102 "symbolically execute a constant "
103 "derived loop"),
104 cl::init(100));
105
106 INITIALIZE_PASS(ScalarEvolution, "scalar-evolution",
107 "Scalar Evolution Analysis", false, true);
108 char ScalarEvolution::ID = 0;
109
110 //===----------------------------------------------------------------------===//
111 // SCEV class definitions
112 //===----------------------------------------------------------------------===//
113
114 //===----------------------------------------------------------------------===//
115 // Implementation of the SCEV class.
116 //
117
~SCEV()118 SCEV::~SCEV() {}
119
dump() const120 void SCEV::dump() const {
121 print(dbgs());
122 dbgs() << '\n';
123 }
124
isZero() const125 bool SCEV::isZero() const {
126 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
127 return SC->getValue()->isZero();
128 return false;
129 }
130
isOne() const131 bool SCEV::isOne() const {
132 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
133 return SC->getValue()->isOne();
134 return false;
135 }
136
isAllOnesValue() const137 bool SCEV::isAllOnesValue() const {
138 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
139 return SC->getValue()->isAllOnesValue();
140 return false;
141 }
142
SCEVCouldNotCompute()143 SCEVCouldNotCompute::SCEVCouldNotCompute() :
144 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
145
isLoopInvariant(const Loop * L) const146 bool SCEVCouldNotCompute::isLoopInvariant(const Loop *L) const {
147 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
148 return false;
149 }
150
getType() const151 const Type *SCEVCouldNotCompute::getType() const {
152 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
153 return 0;
154 }
155
hasComputableLoopEvolution(const Loop * L) const156 bool SCEVCouldNotCompute::hasComputableLoopEvolution(const Loop *L) const {
157 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
158 return false;
159 }
160
hasOperand(const SCEV *) const161 bool SCEVCouldNotCompute::hasOperand(const SCEV *) const {
162 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
163 return false;
164 }
165
print(raw_ostream & OS) const166 void SCEVCouldNotCompute::print(raw_ostream &OS) const {
167 OS << "***COULDNOTCOMPUTE***";
168 }
169
classof(const SCEV * S)170 bool SCEVCouldNotCompute::classof(const SCEV *S) {
171 return S->getSCEVType() == scCouldNotCompute;
172 }
173
getConstant(ConstantInt * V)174 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
175 FoldingSetNodeID ID;
176 ID.AddInteger(scConstant);
177 ID.AddPointer(V);
178 void *IP = 0;
179 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
180 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
181 UniqueSCEVs.InsertNode(S, IP);
182 return S;
183 }
184
getConstant(const APInt & Val)185 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
186 return getConstant(ConstantInt::get(getContext(), Val));
187 }
188
189 const SCEV *
getConstant(const Type * Ty,uint64_t V,bool isSigned)190 ScalarEvolution::getConstant(const Type *Ty, uint64_t V, bool isSigned) {
191 const IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
192 return getConstant(ConstantInt::get(ITy, V, isSigned));
193 }
194
getType() const195 const Type *SCEVConstant::getType() const { return V->getType(); }
196
print(raw_ostream & OS) const197 void SCEVConstant::print(raw_ostream &OS) const {
198 WriteAsOperand(OS, V, false);
199 }
200
SCEVCastExpr(const FoldingSetNodeIDRef ID,unsigned SCEVTy,const SCEV * op,const Type * ty)201 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
202 unsigned SCEVTy, const SCEV *op, const Type *ty)
203 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
204
dominates(BasicBlock * BB,DominatorTree * DT) const205 bool SCEVCastExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
206 return Op->dominates(BB, DT);
207 }
208
properlyDominates(BasicBlock * BB,DominatorTree * DT) const209 bool SCEVCastExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
210 return Op->properlyDominates(BB, DT);
211 }
212
SCEVTruncateExpr(const FoldingSetNodeIDRef ID,const SCEV * op,const Type * ty)213 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
214 const SCEV *op, const Type *ty)
215 : SCEVCastExpr(ID, scTruncate, op, ty) {
216 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
217 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
218 "Cannot truncate non-integer value!");
219 }
220
print(raw_ostream & OS) const221 void SCEVTruncateExpr::print(raw_ostream &OS) const {
222 OS << "(trunc " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
223 }
224
SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,const SCEV * op,const Type * ty)225 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
226 const SCEV *op, const Type *ty)
227 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
228 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
229 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
230 "Cannot zero extend non-integer value!");
231 }
232
print(raw_ostream & OS) const233 void SCEVZeroExtendExpr::print(raw_ostream &OS) const {
234 OS << "(zext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
235 }
236
SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,const SCEV * op,const Type * ty)237 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
238 const SCEV *op, const Type *ty)
239 : SCEVCastExpr(ID, scSignExtend, op, ty) {
240 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
241 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
242 "Cannot sign extend non-integer value!");
243 }
244
print(raw_ostream & OS) const245 void SCEVSignExtendExpr::print(raw_ostream &OS) const {
246 OS << "(sext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
247 }
248
print(raw_ostream & OS) const249 void SCEVCommutativeExpr::print(raw_ostream &OS) const {
250 const char *OpStr = getOperationStr();
251 OS << "(";
252 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I) {
253 OS << **I;
254 if (llvm::next(I) != E)
255 OS << OpStr;
256 }
257 OS << ")";
258 }
259
dominates(BasicBlock * BB,DominatorTree * DT) const260 bool SCEVNAryExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
261 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
262 if (!(*I)->dominates(BB, DT))
263 return false;
264 return true;
265 }
266
properlyDominates(BasicBlock * BB,DominatorTree * DT) const267 bool SCEVNAryExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
268 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
269 if (!(*I)->properlyDominates(BB, DT))
270 return false;
271 return true;
272 }
273
isLoopInvariant(const Loop * L) const274 bool SCEVNAryExpr::isLoopInvariant(const Loop *L) const {
275 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
276 if (!(*I)->isLoopInvariant(L))
277 return false;
278 return true;
279 }
280
281 // hasComputableLoopEvolution - N-ary expressions have computable loop
282 // evolutions iff they have at least one operand that varies with the loop,
283 // but that all varying operands are computable.
hasComputableLoopEvolution(const Loop * L) const284 bool SCEVNAryExpr::hasComputableLoopEvolution(const Loop *L) const {
285 bool HasVarying = false;
286 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I) {
287 const SCEV *S = *I;
288 if (!S->isLoopInvariant(L)) {
289 if (S->hasComputableLoopEvolution(L))
290 HasVarying = true;
291 else
292 return false;
293 }
294 }
295 return HasVarying;
296 }
297
hasOperand(const SCEV * O) const298 bool SCEVNAryExpr::hasOperand(const SCEV *O) const {
299 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I) {
300 const SCEV *S = *I;
301 if (O == S || S->hasOperand(O))
302 return true;
303 }
304 return false;
305 }
306
dominates(BasicBlock * BB,DominatorTree * DT) const307 bool SCEVUDivExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
308 return LHS->dominates(BB, DT) && RHS->dominates(BB, DT);
309 }
310
properlyDominates(BasicBlock * BB,DominatorTree * DT) const311 bool SCEVUDivExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
312 return LHS->properlyDominates(BB, DT) && RHS->properlyDominates(BB, DT);
313 }
314
print(raw_ostream & OS) const315 void SCEVUDivExpr::print(raw_ostream &OS) const {
316 OS << "(" << *LHS << " /u " << *RHS << ")";
317 }
318
getType() const319 const Type *SCEVUDivExpr::getType() const {
320 // In most cases the types of LHS and RHS will be the same, but in some
321 // crazy cases one or the other may be a pointer. ScalarEvolution doesn't
322 // depend on the type for correctness, but handling types carefully can
323 // avoid extra casts in the SCEVExpander. The LHS is more likely to be
324 // a pointer type than the RHS, so use the RHS' type here.
325 return RHS->getType();
326 }
327
isLoopInvariant(const Loop * QueryLoop) const328 bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
329 // Add recurrences are never invariant in the function-body (null loop).
330 if (!QueryLoop)
331 return false;
332
333 // This recurrence is variant w.r.t. QueryLoop if QueryLoop contains L.
334 if (QueryLoop->contains(L))
335 return false;
336
337 // This recurrence is invariant w.r.t. QueryLoop if L contains QueryLoop.
338 if (L->contains(QueryLoop))
339 return true;
340
341 // This recurrence is variant w.r.t. QueryLoop if any of its operands
342 // are variant.
343 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
344 if (!(*I)->isLoopInvariant(QueryLoop))
345 return false;
346
347 // Otherwise it's loop-invariant.
348 return true;
349 }
350
351 bool
dominates(BasicBlock * BB,DominatorTree * DT) const352 SCEVAddRecExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
353 return DT->dominates(L->getHeader(), BB) &&
354 SCEVNAryExpr::dominates(BB, DT);
355 }
356
357 bool
properlyDominates(BasicBlock * BB,DominatorTree * DT) const358 SCEVAddRecExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
359 // This uses a "dominates" query instead of "properly dominates" query because
360 // the instruction which produces the addrec's value is a PHI, and a PHI
361 // effectively properly dominates its entire containing block.
362 return DT->dominates(L->getHeader(), BB) &&
363 SCEVNAryExpr::properlyDominates(BB, DT);
364 }
365
print(raw_ostream & OS) const366 void SCEVAddRecExpr::print(raw_ostream &OS) const {
367 OS << "{" << *Operands[0];
368 for (unsigned i = 1, e = NumOperands; i != e; ++i)
369 OS << ",+," << *Operands[i];
370 OS << "}<";
371 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
372 OS << ">";
373 }
374
deleted()375 void SCEVUnknown::deleted() {
376 // Clear this SCEVUnknown from ValuesAtScopes.
377 SE->ValuesAtScopes.erase(this);
378
379 // Remove this SCEVUnknown from the uniquing map.
380 SE->UniqueSCEVs.RemoveNode(this);
381
382 // Release the value.
383 setValPtr(0);
384 }
385
allUsesReplacedWith(Value * New)386 void SCEVUnknown::allUsesReplacedWith(Value *New) {
387 // Clear this SCEVUnknown from ValuesAtScopes.
388 SE->ValuesAtScopes.erase(this);
389
390 // Remove this SCEVUnknown from the uniquing map.
391 SE->UniqueSCEVs.RemoveNode(this);
392
393 // Update this SCEVUnknown to point to the new value. This is needed
394 // because there may still be outstanding SCEVs which still point to
395 // this SCEVUnknown.
396 setValPtr(New);
397 }
398
isLoopInvariant(const Loop * L) const399 bool SCEVUnknown::isLoopInvariant(const Loop *L) const {
400 // All non-instruction values are loop invariant. All instructions are loop
401 // invariant if they are not contained in the specified loop.
402 // Instructions are never considered invariant in the function body
403 // (null loop) because they are defined within the "loop".
404 if (Instruction *I = dyn_cast<Instruction>(getValue()))
405 return L && !L->contains(I);
406 return true;
407 }
408
dominates(BasicBlock * BB,DominatorTree * DT) const409 bool SCEVUnknown::dominates(BasicBlock *BB, DominatorTree *DT) const {
410 if (Instruction *I = dyn_cast<Instruction>(getValue()))
411 return DT->dominates(I->getParent(), BB);
412 return true;
413 }
414
properlyDominates(BasicBlock * BB,DominatorTree * DT) const415 bool SCEVUnknown::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
416 if (Instruction *I = dyn_cast<Instruction>(getValue()))
417 return DT->properlyDominates(I->getParent(), BB);
418 return true;
419 }
420
getType() const421 const Type *SCEVUnknown::getType() const {
422 return getValue()->getType();
423 }
424
isSizeOf(const Type * & AllocTy) const425 bool SCEVUnknown::isSizeOf(const Type *&AllocTy) const {
426 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
427 if (VCE->getOpcode() == Instruction::PtrToInt)
428 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
429 if (CE->getOpcode() == Instruction::GetElementPtr &&
430 CE->getOperand(0)->isNullValue() &&
431 CE->getNumOperands() == 2)
432 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
433 if (CI->isOne()) {
434 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
435 ->getElementType();
436 return true;
437 }
438
439 return false;
440 }
441
isAlignOf(const Type * & AllocTy) const442 bool SCEVUnknown::isAlignOf(const Type *&AllocTy) const {
443 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
444 if (VCE->getOpcode() == Instruction::PtrToInt)
445 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
446 if (CE->getOpcode() == Instruction::GetElementPtr &&
447 CE->getOperand(0)->isNullValue()) {
448 const Type *Ty =
449 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
450 if (const StructType *STy = dyn_cast<StructType>(Ty))
451 if (!STy->isPacked() &&
452 CE->getNumOperands() == 3 &&
453 CE->getOperand(1)->isNullValue()) {
454 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
455 if (CI->isOne() &&
456 STy->getNumElements() == 2 &&
457 STy->getElementType(0)->isIntegerTy(1)) {
458 AllocTy = STy->getElementType(1);
459 return true;
460 }
461 }
462 }
463
464 return false;
465 }
466
isOffsetOf(const Type * & CTy,Constant * & FieldNo) const467 bool SCEVUnknown::isOffsetOf(const Type *&CTy, Constant *&FieldNo) const {
468 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
469 if (VCE->getOpcode() == Instruction::PtrToInt)
470 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
471 if (CE->getOpcode() == Instruction::GetElementPtr &&
472 CE->getNumOperands() == 3 &&
473 CE->getOperand(0)->isNullValue() &&
474 CE->getOperand(1)->isNullValue()) {
475 const Type *Ty =
476 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
477 // Ignore vector types here so that ScalarEvolutionExpander doesn't
478 // emit getelementptrs that index into vectors.
479 if (Ty->isStructTy() || Ty->isArrayTy()) {
480 CTy = Ty;
481 FieldNo = CE->getOperand(2);
482 return true;
483 }
484 }
485
486 return false;
487 }
488
print(raw_ostream & OS) const489 void SCEVUnknown::print(raw_ostream &OS) const {
490 const Type *AllocTy;
491 if (isSizeOf(AllocTy)) {
492 OS << "sizeof(" << *AllocTy << ")";
493 return;
494 }
495 if (isAlignOf(AllocTy)) {
496 OS << "alignof(" << *AllocTy << ")";
497 return;
498 }
499
500 const Type *CTy;
501 Constant *FieldNo;
502 if (isOffsetOf(CTy, FieldNo)) {
503 OS << "offsetof(" << *CTy << ", ";
504 WriteAsOperand(OS, FieldNo, false);
505 OS << ")";
506 return;
507 }
508
509 // Otherwise just print it normally.
510 WriteAsOperand(OS, getValue(), false);
511 }
512
513 //===----------------------------------------------------------------------===//
514 // SCEV Utilities
515 //===----------------------------------------------------------------------===//
516
517 namespace {
518 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
519 /// than the complexity of the RHS. This comparator is used to canonicalize
520 /// expressions.
521 class SCEVComplexityCompare {
522 const LoopInfo *const LI;
523 public:
SCEVComplexityCompare(const LoopInfo * li)524 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
525
526 // Return true or false if LHS is less than, or at least RHS, respectively.
operator ()(const SCEV * LHS,const SCEV * RHS) const527 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
528 return compare(LHS, RHS) < 0;
529 }
530
531 // Return negative, zero, or positive, if LHS is less than, equal to, or
532 // greater than RHS, respectively. A three-way result allows recursive
533 // comparisons to be more efficient.
compare(const SCEV * LHS,const SCEV * RHS) const534 int compare(const SCEV *LHS, const SCEV *RHS) const {
535 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
536 if (LHS == RHS)
537 return 0;
538
539 // Primarily, sort the SCEVs by their getSCEVType().
540 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
541 if (LType != RType)
542 return (int)LType - (int)RType;
543
544 // Aside from the getSCEVType() ordering, the particular ordering
545 // isn't very important except that it's beneficial to be consistent,
546 // so that (a + b) and (b + a) don't end up as different expressions.
547 switch (LType) {
548 case scUnknown: {
549 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
550 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
551
552 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
553 // not as complete as it could be.
554 const Value *LV = LU->getValue(), *RV = RU->getValue();
555
556 // Order pointer values after integer values. This helps SCEVExpander
557 // form GEPs.
558 bool LIsPointer = LV->getType()->isPointerTy(),
559 RIsPointer = RV->getType()->isPointerTy();
560 if (LIsPointer != RIsPointer)
561 return (int)LIsPointer - (int)RIsPointer;
562
563 // Compare getValueID values.
564 unsigned LID = LV->getValueID(),
565 RID = RV->getValueID();
566 if (LID != RID)
567 return (int)LID - (int)RID;
568
569 // Sort arguments by their position.
570 if (const Argument *LA = dyn_cast<Argument>(LV)) {
571 const Argument *RA = cast<Argument>(RV);
572 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
573 return (int)LArgNo - (int)RArgNo;
574 }
575
576 // For instructions, compare their loop depth, and their operand
577 // count. This is pretty loose.
578 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
579 const Instruction *RInst = cast<Instruction>(RV);
580
581 // Compare loop depths.
582 const BasicBlock *LParent = LInst->getParent(),
583 *RParent = RInst->getParent();
584 if (LParent != RParent) {
585 unsigned LDepth = LI->getLoopDepth(LParent),
586 RDepth = LI->getLoopDepth(RParent);
587 if (LDepth != RDepth)
588 return (int)LDepth - (int)RDepth;
589 }
590
591 // Compare the number of operands.
592 unsigned LNumOps = LInst->getNumOperands(),
593 RNumOps = RInst->getNumOperands();
594 return (int)LNumOps - (int)RNumOps;
595 }
596
597 return 0;
598 }
599
600 case scConstant: {
601 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
602 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
603
604 // Compare constant values.
605 const APInt &LA = LC->getValue()->getValue();
606 const APInt &RA = RC->getValue()->getValue();
607 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
608 if (LBitWidth != RBitWidth)
609 return (int)LBitWidth - (int)RBitWidth;
610 return LA.ult(RA) ? -1 : 1;
611 }
612
613 case scAddRecExpr: {
614 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
615 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
616
617 // Compare addrec loop depths.
618 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
619 if (LLoop != RLoop) {
620 unsigned LDepth = LLoop->getLoopDepth(),
621 RDepth = RLoop->getLoopDepth();
622 if (LDepth != RDepth)
623 return (int)LDepth - (int)RDepth;
624 }
625
626 // Addrec complexity grows with operand count.
627 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
628 if (LNumOps != RNumOps)
629 return (int)LNumOps - (int)RNumOps;
630
631 // Lexicographically compare.
632 for (unsigned i = 0; i != LNumOps; ++i) {
633 long X = compare(LA->getOperand(i), RA->getOperand(i));
634 if (X != 0)
635 return X;
636 }
637
638 return 0;
639 }
640
641 case scAddExpr:
642 case scMulExpr:
643 case scSMaxExpr:
644 case scUMaxExpr: {
645 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
646 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
647
648 // Lexicographically compare n-ary expressions.
649 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
650 for (unsigned i = 0; i != LNumOps; ++i) {
651 if (i >= RNumOps)
652 return 1;
653 long X = compare(LC->getOperand(i), RC->getOperand(i));
654 if (X != 0)
655 return X;
656 }
657 return (int)LNumOps - (int)RNumOps;
658 }
659
660 case scUDivExpr: {
661 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
662 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
663
664 // Lexicographically compare udiv expressions.
665 long X = compare(LC->getLHS(), RC->getLHS());
666 if (X != 0)
667 return X;
668 return compare(LC->getRHS(), RC->getRHS());
669 }
670
671 case scTruncate:
672 case scZeroExtend:
673 case scSignExtend: {
674 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
675 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
676
677 // Compare cast expressions by operand.
678 return compare(LC->getOperand(), RC->getOperand());
679 }
680
681 default:
682 break;
683 }
684
685 llvm_unreachable("Unknown SCEV kind!");
686 return 0;
687 }
688 };
689 }
690
691 /// GroupByComplexity - Given a list of SCEV objects, order them by their
692 /// complexity, and group objects of the same complexity together by value.
693 /// When this routine is finished, we know that any duplicates in the vector are
694 /// consecutive and that complexity is monotonically increasing.
695 ///
696 /// Note that we go take special precautions to ensure that we get deterministic
697 /// results from this routine. In other words, we don't want the results of
698 /// this to depend on where the addresses of various SCEV objects happened to
699 /// land in memory.
700 ///
GroupByComplexity(SmallVectorImpl<const SCEV * > & Ops,LoopInfo * LI)701 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
702 LoopInfo *LI) {
703 if (Ops.size() < 2) return; // Noop
704 if (Ops.size() == 2) {
705 // This is the common case, which also happens to be trivially simple.
706 // Special case it.
707 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
708 if (SCEVComplexityCompare(LI)(RHS, LHS))
709 std::swap(LHS, RHS);
710 return;
711 }
712
713 // Do the rough sort by complexity.
714 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
715
716 // Now that we are sorted by complexity, group elements of the same
717 // complexity. Note that this is, at worst, N^2, but the vector is likely to
718 // be extremely short in practice. Note that we take this approach because we
719 // do not want to depend on the addresses of the objects we are grouping.
720 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
721 const SCEV *S = Ops[i];
722 unsigned Complexity = S->getSCEVType();
723
724 // If there are any objects of the same complexity and same value as this
725 // one, group them.
726 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
727 if (Ops[j] == S) { // Found a duplicate.
728 // Move it to immediately after i'th element.
729 std::swap(Ops[i+1], Ops[j]);
730 ++i; // no need to rescan it.
731 if (i == e-2) return; // Done!
732 }
733 }
734 }
735 }
736
737
738
739 //===----------------------------------------------------------------------===//
740 // Simple SCEV method implementations
741 //===----------------------------------------------------------------------===//
742
743 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
744 /// Assume, K > 0.
BinomialCoefficient(const SCEV * It,unsigned K,ScalarEvolution & SE,const Type * ResultTy)745 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
746 ScalarEvolution &SE,
747 const Type* ResultTy) {
748 // Handle the simplest case efficiently.
749 if (K == 1)
750 return SE.getTruncateOrZeroExtend(It, ResultTy);
751
752 // We are using the following formula for BC(It, K):
753 //
754 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
755 //
756 // Suppose, W is the bitwidth of the return value. We must be prepared for
757 // overflow. Hence, we must assure that the result of our computation is
758 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
759 // safe in modular arithmetic.
760 //
761 // However, this code doesn't use exactly that formula; the formula it uses
762 // is something like the following, where T is the number of factors of 2 in
763 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
764 // exponentiation:
765 //
766 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
767 //
768 // This formula is trivially equivalent to the previous formula. However,
769 // this formula can be implemented much more efficiently. The trick is that
770 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
771 // arithmetic. To do exact division in modular arithmetic, all we have
772 // to do is multiply by the inverse. Therefore, this step can be done at
773 // width W.
774 //
775 // The next issue is how to safely do the division by 2^T. The way this
776 // is done is by doing the multiplication step at a width of at least W + T
777 // bits. This way, the bottom W+T bits of the product are accurate. Then,
778 // when we perform the division by 2^T (which is equivalent to a right shift
779 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
780 // truncated out after the division by 2^T.
781 //
782 // In comparison to just directly using the first formula, this technique
783 // is much more efficient; using the first formula requires W * K bits,
784 // but this formula less than W + K bits. Also, the first formula requires
785 // a division step, whereas this formula only requires multiplies and shifts.
786 //
787 // It doesn't matter whether the subtraction step is done in the calculation
788 // width or the input iteration count's width; if the subtraction overflows,
789 // the result must be zero anyway. We prefer here to do it in the width of
790 // the induction variable because it helps a lot for certain cases; CodeGen
791 // isn't smart enough to ignore the overflow, which leads to much less
792 // efficient code if the width of the subtraction is wider than the native
793 // register width.
794 //
795 // (It's possible to not widen at all by pulling out factors of 2 before
796 // the multiplication; for example, K=2 can be calculated as
797 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
798 // extra arithmetic, so it's not an obvious win, and it gets
799 // much more complicated for K > 3.)
800
801 // Protection from insane SCEVs; this bound is conservative,
802 // but it probably doesn't matter.
803 if (K > 1000)
804 return SE.getCouldNotCompute();
805
806 unsigned W = SE.getTypeSizeInBits(ResultTy);
807
808 // Calculate K! / 2^T and T; we divide out the factors of two before
809 // multiplying for calculating K! / 2^T to avoid overflow.
810 // Other overflow doesn't matter because we only care about the bottom
811 // W bits of the result.
812 APInt OddFactorial(W, 1);
813 unsigned T = 1;
814 for (unsigned i = 3; i <= K; ++i) {
815 APInt Mult(W, i);
816 unsigned TwoFactors = Mult.countTrailingZeros();
817 T += TwoFactors;
818 Mult = Mult.lshr(TwoFactors);
819 OddFactorial *= Mult;
820 }
821
822 // We need at least W + T bits for the multiplication step
823 unsigned CalculationBits = W + T;
824
825 // Calculate 2^T, at width T+W.
826 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
827
828 // Calculate the multiplicative inverse of K! / 2^T;
829 // this multiplication factor will perform the exact division by
830 // K! / 2^T.
831 APInt Mod = APInt::getSignedMinValue(W+1);
832 APInt MultiplyFactor = OddFactorial.zext(W+1);
833 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
834 MultiplyFactor = MultiplyFactor.trunc(W);
835
836 // Calculate the product, at width T+W
837 const IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
838 CalculationBits);
839 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
840 for (unsigned i = 1; i != K; ++i) {
841 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
842 Dividend = SE.getMulExpr(Dividend,
843 SE.getTruncateOrZeroExtend(S, CalculationTy));
844 }
845
846 // Divide by 2^T
847 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
848
849 // Truncate the result, and divide by K! / 2^T.
850
851 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
852 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
853 }
854
855 /// evaluateAtIteration - Return the value of this chain of recurrences at
856 /// the specified iteration number. We can evaluate this recurrence by
857 /// multiplying each element in the chain by the binomial coefficient
858 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
859 ///
860 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
861 ///
862 /// where BC(It, k) stands for binomial coefficient.
863 ///
evaluateAtIteration(const SCEV * It,ScalarEvolution & SE) const864 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
865 ScalarEvolution &SE) const {
866 const SCEV *Result = getStart();
867 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
868 // The computation is correct in the face of overflow provided that the
869 // multiplication is performed _after_ the evaluation of the binomial
870 // coefficient.
871 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
872 if (isa<SCEVCouldNotCompute>(Coeff))
873 return Coeff;
874
875 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
876 }
877 return Result;
878 }
879
880 //===----------------------------------------------------------------------===//
881 // SCEV Expression folder implementations
882 //===----------------------------------------------------------------------===//
883
getTruncateExpr(const SCEV * Op,const Type * Ty)884 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
885 const Type *Ty) {
886 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
887 "This is not a truncating conversion!");
888 assert(isSCEVable(Ty) &&
889 "This is not a conversion to a SCEVable type!");
890 Ty = getEffectiveSCEVType(Ty);
891
892 FoldingSetNodeID ID;
893 ID.AddInteger(scTruncate);
894 ID.AddPointer(Op);
895 ID.AddPointer(Ty);
896 void *IP = 0;
897 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
898
899 // Fold if the operand is constant.
900 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
901 return getConstant(
902 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
903 getEffectiveSCEVType(Ty))));
904
905 // trunc(trunc(x)) --> trunc(x)
906 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
907 return getTruncateExpr(ST->getOperand(), Ty);
908
909 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
910 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
911 return getTruncateOrSignExtend(SS->getOperand(), Ty);
912
913 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
914 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
915 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
916
917 // If the input value is a chrec scev, truncate the chrec's operands.
918 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
919 SmallVector<const SCEV *, 4> Operands;
920 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
921 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
922 return getAddRecExpr(Operands, AddRec->getLoop());
923 }
924
925 // As a special case, fold trunc(undef) to undef. We don't want to
926 // know too much about SCEVUnknowns, but this special case is handy
927 // and harmless.
928 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
929 if (isa<UndefValue>(U->getValue()))
930 return getSCEV(UndefValue::get(Ty));
931
932 // The cast wasn't folded; create an explicit cast node. We can reuse
933 // the existing insert position since if we get here, we won't have
934 // made any changes which would invalidate it.
935 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
936 Op, Ty);
937 UniqueSCEVs.InsertNode(S, IP);
938 return S;
939 }
940
getZeroExtendExpr(const SCEV * Op,const Type * Ty)941 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
942 const Type *Ty) {
943 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
944 "This is not an extending conversion!");
945 assert(isSCEVable(Ty) &&
946 "This is not a conversion to a SCEVable type!");
947 Ty = getEffectiveSCEVType(Ty);
948
949 // Fold if the operand is constant.
950 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
951 return getConstant(
952 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
953 getEffectiveSCEVType(Ty))));
954
955 // zext(zext(x)) --> zext(x)
956 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
957 return getZeroExtendExpr(SZ->getOperand(), Ty);
958
959 // Before doing any expensive analysis, check to see if we've already
960 // computed a SCEV for this Op and Ty.
961 FoldingSetNodeID ID;
962 ID.AddInteger(scZeroExtend);
963 ID.AddPointer(Op);
964 ID.AddPointer(Ty);
965 void *IP = 0;
966 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
967
968 // If the input value is a chrec scev, and we can prove that the value
969 // did not overflow the old, smaller, value, we can zero extend all of the
970 // operands (often constants). This allows analysis of something like
971 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
972 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
973 if (AR->isAffine()) {
974 const SCEV *Start = AR->getStart();
975 const SCEV *Step = AR->getStepRecurrence(*this);
976 unsigned BitWidth = getTypeSizeInBits(AR->getType());
977 const Loop *L = AR->getLoop();
978
979 // If we have special knowledge that this addrec won't overflow,
980 // we don't need to do any further analysis.
981 if (AR->hasNoUnsignedWrap())
982 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
983 getZeroExtendExpr(Step, Ty),
984 L);
985
986 // Check whether the backedge-taken count is SCEVCouldNotCompute.
987 // Note that this serves two purposes: It filters out loops that are
988 // simply not analyzable, and it covers the case where this code is
989 // being called from within backedge-taken count analysis, such that
990 // attempting to ask for the backedge-taken count would likely result
991 // in infinite recursion. In the later case, the analysis code will
992 // cope with a conservative value, and it will take care to purge
993 // that value once it has finished.
994 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
995 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
996 // Manually compute the final value for AR, checking for
997 // overflow.
998
999 // Check whether the backedge-taken count can be losslessly casted to
1000 // the addrec's type. The count is always unsigned.
1001 const SCEV *CastedMaxBECount =
1002 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1003 const SCEV *RecastedMaxBECount =
1004 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1005 if (MaxBECount == RecastedMaxBECount) {
1006 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1007 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1008 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1009 const SCEV *Add = getAddExpr(Start, ZMul);
1010 const SCEV *OperandExtendedAdd =
1011 getAddExpr(getZeroExtendExpr(Start, WideTy),
1012 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1013 getZeroExtendExpr(Step, WideTy)));
1014 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
1015 // Return the expression with the addrec on the outside.
1016 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1017 getZeroExtendExpr(Step, Ty),
1018 L);
1019
1020 // Similar to above, only this time treat the step value as signed.
1021 // This covers loops that count down.
1022 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1023 Add = getAddExpr(Start, SMul);
1024 OperandExtendedAdd =
1025 getAddExpr(getZeroExtendExpr(Start, WideTy),
1026 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1027 getSignExtendExpr(Step, WideTy)));
1028 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
1029 // Return the expression with the addrec on the outside.
1030 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1031 getSignExtendExpr(Step, Ty),
1032 L);
1033 }
1034
1035 // If the backedge is guarded by a comparison with the pre-inc value
1036 // the addrec is safe. Also, if the entry is guarded by a comparison
1037 // with the start value and the backedge is guarded by a comparison
1038 // with the post-inc value, the addrec is safe.
1039 if (isKnownPositive(Step)) {
1040 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1041 getUnsignedRange(Step).getUnsignedMax());
1042 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1043 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1044 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1045 AR->getPostIncExpr(*this), N)))
1046 // Return the expression with the addrec on the outside.
1047 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1048 getZeroExtendExpr(Step, Ty),
1049 L);
1050 } else if (isKnownNegative(Step)) {
1051 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1052 getSignedRange(Step).getSignedMin());
1053 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1054 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1055 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1056 AR->getPostIncExpr(*this), N)))
1057 // Return the expression with the addrec on the outside.
1058 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1059 getSignExtendExpr(Step, Ty),
1060 L);
1061 }
1062 }
1063 }
1064
1065 // The cast wasn't folded; create an explicit cast node.
1066 // Recompute the insert position, as it may have been invalidated.
1067 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1068 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1069 Op, Ty);
1070 UniqueSCEVs.InsertNode(S, IP);
1071 return S;
1072 }
1073
getSignExtendExpr(const SCEV * Op,const Type * Ty)1074 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1075 const Type *Ty) {
1076 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1077 "This is not an extending conversion!");
1078 assert(isSCEVable(Ty) &&
1079 "This is not a conversion to a SCEVable type!");
1080 Ty = getEffectiveSCEVType(Ty);
1081
1082 // Fold if the operand is constant.
1083 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1084 return getConstant(
1085 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1086 getEffectiveSCEVType(Ty))));
1087
1088 // sext(sext(x)) --> sext(x)
1089 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1090 return getSignExtendExpr(SS->getOperand(), Ty);
1091
1092 // Before doing any expensive analysis, check to see if we've already
1093 // computed a SCEV for this Op and Ty.
1094 FoldingSetNodeID ID;
1095 ID.AddInteger(scSignExtend);
1096 ID.AddPointer(Op);
1097 ID.AddPointer(Ty);
1098 void *IP = 0;
1099 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1100
1101 // If the input value is a chrec scev, and we can prove that the value
1102 // did not overflow the old, smaller, value, we can sign extend all of the
1103 // operands (often constants). This allows analysis of something like
1104 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1105 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1106 if (AR->isAffine()) {
1107 const SCEV *Start = AR->getStart();
1108 const SCEV *Step = AR->getStepRecurrence(*this);
1109 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1110 const Loop *L = AR->getLoop();
1111
1112 // If we have special knowledge that this addrec won't overflow,
1113 // we don't need to do any further analysis.
1114 if (AR->hasNoSignedWrap())
1115 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1116 getSignExtendExpr(Step, Ty),
1117 L);
1118
1119 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1120 // Note that this serves two purposes: It filters out loops that are
1121 // simply not analyzable, and it covers the case where this code is
1122 // being called from within backedge-taken count analysis, such that
1123 // attempting to ask for the backedge-taken count would likely result
1124 // in infinite recursion. In the later case, the analysis code will
1125 // cope with a conservative value, and it will take care to purge
1126 // that value once it has finished.
1127 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1128 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1129 // Manually compute the final value for AR, checking for
1130 // overflow.
1131
1132 // Check whether the backedge-taken count can be losslessly casted to
1133 // the addrec's type. The count is always unsigned.
1134 const SCEV *CastedMaxBECount =
1135 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1136 const SCEV *RecastedMaxBECount =
1137 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1138 if (MaxBECount == RecastedMaxBECount) {
1139 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1140 // Check whether Start+Step*MaxBECount has no signed overflow.
1141 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1142 const SCEV *Add = getAddExpr(Start, SMul);
1143 const SCEV *OperandExtendedAdd =
1144 getAddExpr(getSignExtendExpr(Start, WideTy),
1145 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1146 getSignExtendExpr(Step, WideTy)));
1147 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1148 // Return the expression with the addrec on the outside.
1149 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1150 getSignExtendExpr(Step, Ty),
1151 L);
1152
1153 // Similar to above, only this time treat the step value as unsigned.
1154 // This covers loops that count up with an unsigned step.
1155 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1156 Add = getAddExpr(Start, UMul);
1157 OperandExtendedAdd =
1158 getAddExpr(getSignExtendExpr(Start, WideTy),
1159 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1160 getZeroExtendExpr(Step, WideTy)));
1161 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1162 // Return the expression with the addrec on the outside.
1163 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1164 getZeroExtendExpr(Step, Ty),
1165 L);
1166 }
1167
1168 // If the backedge is guarded by a comparison with the pre-inc value
1169 // the addrec is safe. Also, if the entry is guarded by a comparison
1170 // with the start value and the backedge is guarded by a comparison
1171 // with the post-inc value, the addrec is safe.
1172 if (isKnownPositive(Step)) {
1173 const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
1174 getSignedRange(Step).getSignedMax());
1175 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
1176 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
1177 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
1178 AR->getPostIncExpr(*this), N)))
1179 // Return the expression with the addrec on the outside.
1180 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1181 getSignExtendExpr(Step, Ty),
1182 L);
1183 } else if (isKnownNegative(Step)) {
1184 const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
1185 getSignedRange(Step).getSignedMin());
1186 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
1187 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
1188 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
1189 AR->getPostIncExpr(*this), N)))
1190 // Return the expression with the addrec on the outside.
1191 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1192 getSignExtendExpr(Step, Ty),
1193 L);
1194 }
1195 }
1196 }
1197
1198 // The cast wasn't folded; create an explicit cast node.
1199 // Recompute the insert position, as it may have been invalidated.
1200 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1201 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1202 Op, Ty);
1203 UniqueSCEVs.InsertNode(S, IP);
1204 return S;
1205 }
1206
1207 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1208 /// unspecified bits out to the given type.
1209 ///
getAnyExtendExpr(const SCEV * Op,const Type * Ty)1210 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1211 const Type *Ty) {
1212 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1213 "This is not an extending conversion!");
1214 assert(isSCEVable(Ty) &&
1215 "This is not a conversion to a SCEVable type!");
1216 Ty = getEffectiveSCEVType(Ty);
1217
1218 // Sign-extend negative constants.
1219 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1220 if (SC->getValue()->getValue().isNegative())
1221 return getSignExtendExpr(Op, Ty);
1222
1223 // Peel off a truncate cast.
1224 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1225 const SCEV *NewOp = T->getOperand();
1226 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1227 return getAnyExtendExpr(NewOp, Ty);
1228 return getTruncateOrNoop(NewOp, Ty);
1229 }
1230
1231 // Next try a zext cast. If the cast is folded, use it.
1232 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1233 if (!isa<SCEVZeroExtendExpr>(ZExt))
1234 return ZExt;
1235
1236 // Next try a sext cast. If the cast is folded, use it.
1237 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1238 if (!isa<SCEVSignExtendExpr>(SExt))
1239 return SExt;
1240
1241 // Force the cast to be folded into the operands of an addrec.
1242 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1243 SmallVector<const SCEV *, 4> Ops;
1244 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1245 I != E; ++I)
1246 Ops.push_back(getAnyExtendExpr(*I, Ty));
1247 return getAddRecExpr(Ops, AR->getLoop());
1248 }
1249
1250 // As a special case, fold anyext(undef) to undef. We don't want to
1251 // know too much about SCEVUnknowns, but this special case is handy
1252 // and harmless.
1253 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
1254 if (isa<UndefValue>(U->getValue()))
1255 return getSCEV(UndefValue::get(Ty));
1256
1257 // If the expression is obviously signed, use the sext cast value.
1258 if (isa<SCEVSMaxExpr>(Op))
1259 return SExt;
1260
1261 // Absent any other information, use the zext cast value.
1262 return ZExt;
1263 }
1264
1265 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1266 /// a list of operands to be added under the given scale, update the given
1267 /// map. This is a helper function for getAddRecExpr. As an example of
1268 /// what it does, given a sequence of operands that would form an add
1269 /// expression like this:
1270 ///
1271 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1272 ///
1273 /// where A and B are constants, update the map with these values:
1274 ///
1275 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1276 ///
1277 /// and add 13 + A*B*29 to AccumulatedConstant.
1278 /// This will allow getAddRecExpr to produce this:
1279 ///
1280 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1281 ///
1282 /// This form often exposes folding opportunities that are hidden in
1283 /// the original operand list.
1284 ///
1285 /// Return true iff it appears that any interesting folding opportunities
1286 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1287 /// the common case where no interesting opportunities are present, and
1288 /// is also used as a check to avoid infinite recursion.
1289 ///
1290 static bool
CollectAddOperandsWithScales(DenseMap<const SCEV *,APInt> & M,SmallVector<const SCEV *,8> & NewOps,APInt & AccumulatedConstant,const SCEV * const * Ops,size_t NumOperands,const APInt & Scale,ScalarEvolution & SE)1291 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1292 SmallVector<const SCEV *, 8> &NewOps,
1293 APInt &AccumulatedConstant,
1294 const SCEV *const *Ops, size_t NumOperands,
1295 const APInt &Scale,
1296 ScalarEvolution &SE) {
1297 bool Interesting = false;
1298
1299 // Iterate over the add operands. They are sorted, with constants first.
1300 unsigned i = 0;
1301 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1302 ++i;
1303 // Pull a buried constant out to the outside.
1304 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1305 Interesting = true;
1306 AccumulatedConstant += Scale * C->getValue()->getValue();
1307 }
1308
1309 // Next comes everything else. We're especially interested in multiplies
1310 // here, but they're in the middle, so just visit the rest with one loop.
1311 for (; i != NumOperands; ++i) {
1312 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1313 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1314 APInt NewScale =
1315 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1316 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1317 // A multiplication of a constant with another add; recurse.
1318 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1319 Interesting |=
1320 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1321 Add->op_begin(), Add->getNumOperands(),
1322 NewScale, SE);
1323 } else {
1324 // A multiplication of a constant with some other value. Update
1325 // the map.
1326 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1327 const SCEV *Key = SE.getMulExpr(MulOps);
1328 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1329 M.insert(std::make_pair(Key, NewScale));
1330 if (Pair.second) {
1331 NewOps.push_back(Pair.first->first);
1332 } else {
1333 Pair.first->second += NewScale;
1334 // The map already had an entry for this value, which may indicate
1335 // a folding opportunity.
1336 Interesting = true;
1337 }
1338 }
1339 } else {
1340 // An ordinary operand. Update the map.
1341 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1342 M.insert(std::make_pair(Ops[i], Scale));
1343 if (Pair.second) {
1344 NewOps.push_back(Pair.first->first);
1345 } else {
1346 Pair.first->second += Scale;
1347 // The map already had an entry for this value, which may indicate
1348 // a folding opportunity.
1349 Interesting = true;
1350 }
1351 }
1352 }
1353
1354 return Interesting;
1355 }
1356
1357 namespace {
1358 struct APIntCompare {
operator ()__anon776f352a0211::APIntCompare1359 bool operator()(const APInt &LHS, const APInt &RHS) const {
1360 return LHS.ult(RHS);
1361 }
1362 };
1363 }
1364
1365 /// getAddExpr - Get a canonical add expression, or something simpler if
1366 /// possible.
getAddExpr(SmallVectorImpl<const SCEV * > & Ops,bool HasNUW,bool HasNSW)1367 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1368 bool HasNUW, bool HasNSW) {
1369 assert(!Ops.empty() && "Cannot get empty add!");
1370 if (Ops.size() == 1) return Ops[0];
1371 #ifndef NDEBUG
1372 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1373 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1374 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1375 "SCEVAddExpr operand types don't match!");
1376 #endif
1377
1378 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1379 if (!HasNUW && HasNSW) {
1380 bool All = true;
1381 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1382 E = Ops.end(); I != E; ++I)
1383 if (!isKnownNonNegative(*I)) {
1384 All = false;
1385 break;
1386 }
1387 if (All) HasNUW = true;
1388 }
1389
1390 // Sort by complexity, this groups all similar expression types together.
1391 GroupByComplexity(Ops, LI);
1392
1393 // If there are any constants, fold them together.
1394 unsigned Idx = 0;
1395 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1396 ++Idx;
1397 assert(Idx < Ops.size());
1398 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1399 // We found two constants, fold them together!
1400 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1401 RHSC->getValue()->getValue());
1402 if (Ops.size() == 2) return Ops[0];
1403 Ops.erase(Ops.begin()+1); // Erase the folded element
1404 LHSC = cast<SCEVConstant>(Ops[0]);
1405 }
1406
1407 // If we are left with a constant zero being added, strip it off.
1408 if (LHSC->getValue()->isZero()) {
1409 Ops.erase(Ops.begin());
1410 --Idx;
1411 }
1412
1413 if (Ops.size() == 1) return Ops[0];
1414 }
1415
1416 // Okay, check to see if the same value occurs in the operand list more than
1417 // once. If so, merge them together into an multiply expression. Since we
1418 // sorted the list, these values are required to be adjacent.
1419 const Type *Ty = Ops[0]->getType();
1420 bool FoundMatch = false;
1421 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1422 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1423 // Scan ahead to count how many equal operands there are.
1424 unsigned Count = 2;
1425 while (i+Count != e && Ops[i+Count] == Ops[i])
1426 ++Count;
1427 // Merge the values into a multiply.
1428 const SCEV *Scale = getConstant(Ty, Count);
1429 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1430 if (Ops.size() == Count)
1431 return Mul;
1432 Ops[i] = Mul;
1433 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1434 --i; e -= Count - 1;
1435 FoundMatch = true;
1436 }
1437 if (FoundMatch)
1438 return getAddExpr(Ops, HasNUW, HasNSW);
1439
1440 // Check for truncates. If all the operands are truncated from the same
1441 // type, see if factoring out the truncate would permit the result to be
1442 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1443 // if the contents of the resulting outer trunc fold to something simple.
1444 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1445 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1446 const Type *DstType = Trunc->getType();
1447 const Type *SrcType = Trunc->getOperand()->getType();
1448 SmallVector<const SCEV *, 8> LargeOps;
1449 bool Ok = true;
1450 // Check all the operands to see if they can be represented in the
1451 // source type of the truncate.
1452 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1453 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1454 if (T->getOperand()->getType() != SrcType) {
1455 Ok = false;
1456 break;
1457 }
1458 LargeOps.push_back(T->getOperand());
1459 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1460 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1461 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1462 SmallVector<const SCEV *, 8> LargeMulOps;
1463 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1464 if (const SCEVTruncateExpr *T =
1465 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1466 if (T->getOperand()->getType() != SrcType) {
1467 Ok = false;
1468 break;
1469 }
1470 LargeMulOps.push_back(T->getOperand());
1471 } else if (const SCEVConstant *C =
1472 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1473 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1474 } else {
1475 Ok = false;
1476 break;
1477 }
1478 }
1479 if (Ok)
1480 LargeOps.push_back(getMulExpr(LargeMulOps));
1481 } else {
1482 Ok = false;
1483 break;
1484 }
1485 }
1486 if (Ok) {
1487 // Evaluate the expression in the larger type.
1488 const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
1489 // If it folds to something simple, use it. Otherwise, don't.
1490 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1491 return getTruncateExpr(Fold, DstType);
1492 }
1493 }
1494
1495 // Skip past any other cast SCEVs.
1496 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1497 ++Idx;
1498
1499 // If there are add operands they would be next.
1500 if (Idx < Ops.size()) {
1501 bool DeletedAdd = false;
1502 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1503 // If we have an add, expand the add operands onto the end of the operands
1504 // list.
1505 Ops.erase(Ops.begin()+Idx);
1506 Ops.append(Add->op_begin(), Add->op_end());
1507 DeletedAdd = true;
1508 }
1509
1510 // If we deleted at least one add, we added operands to the end of the list,
1511 // and they are not necessarily sorted. Recurse to resort and resimplify
1512 // any operands we just acquired.
1513 if (DeletedAdd)
1514 return getAddExpr(Ops);
1515 }
1516
1517 // Skip over the add expression until we get to a multiply.
1518 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1519 ++Idx;
1520
1521 // Check to see if there are any folding opportunities present with
1522 // operands multiplied by constant values.
1523 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1524 uint64_t BitWidth = getTypeSizeInBits(Ty);
1525 DenseMap<const SCEV *, APInt> M;
1526 SmallVector<const SCEV *, 8> NewOps;
1527 APInt AccumulatedConstant(BitWidth, 0);
1528 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1529 Ops.data(), Ops.size(),
1530 APInt(BitWidth, 1), *this)) {
1531 // Some interesting folding opportunity is present, so its worthwhile to
1532 // re-generate the operands list. Group the operands by constant scale,
1533 // to avoid multiplying by the same constant scale multiple times.
1534 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1535 for (SmallVector<const SCEV *, 8>::const_iterator I = NewOps.begin(),
1536 E = NewOps.end(); I != E; ++I)
1537 MulOpLists[M.find(*I)->second].push_back(*I);
1538 // Re-generate the operands list.
1539 Ops.clear();
1540 if (AccumulatedConstant != 0)
1541 Ops.push_back(getConstant(AccumulatedConstant));
1542 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1543 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1544 if (I->first != 0)
1545 Ops.push_back(getMulExpr(getConstant(I->first),
1546 getAddExpr(I->second)));
1547 if (Ops.empty())
1548 return getConstant(Ty, 0);
1549 if (Ops.size() == 1)
1550 return Ops[0];
1551 return getAddExpr(Ops);
1552 }
1553 }
1554
1555 // If we are adding something to a multiply expression, make sure the
1556 // something is not already an operand of the multiply. If so, merge it into
1557 // the multiply.
1558 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1559 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1560 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1561 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1562 if (isa<SCEVConstant>(MulOpSCEV))
1563 continue;
1564 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1565 if (MulOpSCEV == Ops[AddOp]) {
1566 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1567 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1568 if (Mul->getNumOperands() != 2) {
1569 // If the multiply has more than two operands, we must get the
1570 // Y*Z term.
1571 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1572 Mul->op_begin()+MulOp);
1573 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1574 InnerMul = getMulExpr(MulOps);
1575 }
1576 const SCEV *One = getConstant(Ty, 1);
1577 const SCEV *AddOne = getAddExpr(One, InnerMul);
1578 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1579 if (Ops.size() == 2) return OuterMul;
1580 if (AddOp < Idx) {
1581 Ops.erase(Ops.begin()+AddOp);
1582 Ops.erase(Ops.begin()+Idx-1);
1583 } else {
1584 Ops.erase(Ops.begin()+Idx);
1585 Ops.erase(Ops.begin()+AddOp-1);
1586 }
1587 Ops.push_back(OuterMul);
1588 return getAddExpr(Ops);
1589 }
1590
1591 // Check this multiply against other multiplies being added together.
1592 for (unsigned OtherMulIdx = Idx+1;
1593 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1594 ++OtherMulIdx) {
1595 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1596 // If MulOp occurs in OtherMul, we can fold the two multiplies
1597 // together.
1598 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1599 OMulOp != e; ++OMulOp)
1600 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1601 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1602 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1603 if (Mul->getNumOperands() != 2) {
1604 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1605 Mul->op_begin()+MulOp);
1606 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1607 InnerMul1 = getMulExpr(MulOps);
1608 }
1609 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1610 if (OtherMul->getNumOperands() != 2) {
1611 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1612 OtherMul->op_begin()+OMulOp);
1613 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
1614 InnerMul2 = getMulExpr(MulOps);
1615 }
1616 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1617 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1618 if (Ops.size() == 2) return OuterMul;
1619 Ops.erase(Ops.begin()+Idx);
1620 Ops.erase(Ops.begin()+OtherMulIdx-1);
1621 Ops.push_back(OuterMul);
1622 return getAddExpr(Ops);
1623 }
1624 }
1625 }
1626 }
1627
1628 // If there are any add recurrences in the operands list, see if any other
1629 // added values are loop invariant. If so, we can fold them into the
1630 // recurrence.
1631 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1632 ++Idx;
1633
1634 // Scan over all recurrences, trying to fold loop invariants into them.
1635 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1636 // Scan all of the other operands to this add and add them to the vector if
1637 // they are loop invariant w.r.t. the recurrence.
1638 SmallVector<const SCEV *, 8> LIOps;
1639 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1640 const Loop *AddRecLoop = AddRec->getLoop();
1641 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1642 if (Ops[i]->isLoopInvariant(AddRecLoop)) {
1643 LIOps.push_back(Ops[i]);
1644 Ops.erase(Ops.begin()+i);
1645 --i; --e;
1646 }
1647
1648 // If we found some loop invariants, fold them into the recurrence.
1649 if (!LIOps.empty()) {
1650 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1651 LIOps.push_back(AddRec->getStart());
1652
1653 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1654 AddRec->op_end());
1655 AddRecOps[0] = getAddExpr(LIOps);
1656
1657 // Build the new addrec. Propagate the NUW and NSW flags if both the
1658 // outer add and the inner addrec are guaranteed to have no overflow.
1659 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
1660 HasNUW && AddRec->hasNoUnsignedWrap(),
1661 HasNSW && AddRec->hasNoSignedWrap());
1662
1663 // If all of the other operands were loop invariant, we are done.
1664 if (Ops.size() == 1) return NewRec;
1665
1666 // Otherwise, add the folded AddRec by the non-liv parts.
1667 for (unsigned i = 0;; ++i)
1668 if (Ops[i] == AddRec) {
1669 Ops[i] = NewRec;
1670 break;
1671 }
1672 return getAddExpr(Ops);
1673 }
1674
1675 // Okay, if there weren't any loop invariants to be folded, check to see if
1676 // there are multiple AddRec's with the same loop induction variable being
1677 // added together. If so, we can fold them.
1678 for (unsigned OtherIdx = Idx+1;
1679 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1680 ++OtherIdx)
1681 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1682 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
1683 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1684 AddRec->op_end());
1685 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1686 ++OtherIdx)
1687 if (const SCEVAddRecExpr *OtherAddRec =
1688 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1689 if (OtherAddRec->getLoop() == AddRecLoop) {
1690 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
1691 i != e; ++i) {
1692 if (i >= AddRecOps.size()) {
1693 AddRecOps.append(OtherAddRec->op_begin()+i,
1694 OtherAddRec->op_end());
1695 break;
1696 }
1697 AddRecOps[i] = getAddExpr(AddRecOps[i],
1698 OtherAddRec->getOperand(i));
1699 }
1700 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1701 }
1702 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop);
1703 return getAddExpr(Ops);
1704 }
1705
1706 // Otherwise couldn't fold anything into this recurrence. Move onto the
1707 // next one.
1708 }
1709
1710 // Okay, it looks like we really DO need an add expr. Check to see if we
1711 // already have one, otherwise create a new one.
1712 FoldingSetNodeID ID;
1713 ID.AddInteger(scAddExpr);
1714 ID.AddInteger(Ops.size());
1715 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1716 ID.AddPointer(Ops[i]);
1717 void *IP = 0;
1718 SCEVAddExpr *S =
1719 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1720 if (!S) {
1721 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1722 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1723 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1724 O, Ops.size());
1725 UniqueSCEVs.InsertNode(S, IP);
1726 }
1727 if (HasNUW) S->setHasNoUnsignedWrap(true);
1728 if (HasNSW) S->setHasNoSignedWrap(true);
1729 return S;
1730 }
1731
1732 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1733 /// possible.
getMulExpr(SmallVectorImpl<const SCEV * > & Ops,bool HasNUW,bool HasNSW)1734 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1735 bool HasNUW, bool HasNSW) {
1736 assert(!Ops.empty() && "Cannot get empty mul!");
1737 if (Ops.size() == 1) return Ops[0];
1738 #ifndef NDEBUG
1739 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1740 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1741 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1742 "SCEVMulExpr operand types don't match!");
1743 #endif
1744
1745 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1746 if (!HasNUW && HasNSW) {
1747 bool All = true;
1748 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1749 E = Ops.end(); I != E; ++I)
1750 if (!isKnownNonNegative(*I)) {
1751 All = false;
1752 break;
1753 }
1754 if (All) HasNUW = true;
1755 }
1756
1757 // Sort by complexity, this groups all similar expression types together.
1758 GroupByComplexity(Ops, LI);
1759
1760 // If there are any constants, fold them together.
1761 unsigned Idx = 0;
1762 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1763
1764 // C1*(C2+V) -> C1*C2 + C1*V
1765 if (Ops.size() == 2)
1766 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1767 if (Add->getNumOperands() == 2 &&
1768 isa<SCEVConstant>(Add->getOperand(0)))
1769 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1770 getMulExpr(LHSC, Add->getOperand(1)));
1771
1772 ++Idx;
1773 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1774 // We found two constants, fold them together!
1775 ConstantInt *Fold = ConstantInt::get(getContext(),
1776 LHSC->getValue()->getValue() *
1777 RHSC->getValue()->getValue());
1778 Ops[0] = getConstant(Fold);
1779 Ops.erase(Ops.begin()+1); // Erase the folded element
1780 if (Ops.size() == 1) return Ops[0];
1781 LHSC = cast<SCEVConstant>(Ops[0]);
1782 }
1783
1784 // If we are left with a constant one being multiplied, strip it off.
1785 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1786 Ops.erase(Ops.begin());
1787 --Idx;
1788 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1789 // If we have a multiply of zero, it will always be zero.
1790 return Ops[0];
1791 } else if (Ops[0]->isAllOnesValue()) {
1792 // If we have a mul by -1 of an add, try distributing the -1 among the
1793 // add operands.
1794 if (Ops.size() == 2)
1795 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1796 SmallVector<const SCEV *, 4> NewOps;
1797 bool AnyFolded = false;
1798 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1799 I != E; ++I) {
1800 const SCEV *Mul = getMulExpr(Ops[0], *I);
1801 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1802 NewOps.push_back(Mul);
1803 }
1804 if (AnyFolded)
1805 return getAddExpr(NewOps);
1806 }
1807 }
1808
1809 if (Ops.size() == 1)
1810 return Ops[0];
1811 }
1812
1813 // Skip over the add expression until we get to a multiply.
1814 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1815 ++Idx;
1816
1817 // If there are mul operands inline them all into this expression.
1818 if (Idx < Ops.size()) {
1819 bool DeletedMul = false;
1820 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1821 // If we have an mul, expand the mul operands onto the end of the operands
1822 // list.
1823 Ops.erase(Ops.begin()+Idx);
1824 Ops.append(Mul->op_begin(), Mul->op_end());
1825 DeletedMul = true;
1826 }
1827
1828 // If we deleted at least one mul, we added operands to the end of the list,
1829 // and they are not necessarily sorted. Recurse to resort and resimplify
1830 // any operands we just acquired.
1831 if (DeletedMul)
1832 return getMulExpr(Ops);
1833 }
1834
1835 // If there are any add recurrences in the operands list, see if any other
1836 // added values are loop invariant. If so, we can fold them into the
1837 // recurrence.
1838 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1839 ++Idx;
1840
1841 // Scan over all recurrences, trying to fold loop invariants into them.
1842 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1843 // Scan all of the other operands to this mul and add them to the vector if
1844 // they are loop invariant w.r.t. the recurrence.
1845 SmallVector<const SCEV *, 8> LIOps;
1846 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1847 const Loop *AddRecLoop = AddRec->getLoop();
1848 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1849 if (Ops[i]->isLoopInvariant(AddRecLoop)) {
1850 LIOps.push_back(Ops[i]);
1851 Ops.erase(Ops.begin()+i);
1852 --i; --e;
1853 }
1854
1855 // If we found some loop invariants, fold them into the recurrence.
1856 if (!LIOps.empty()) {
1857 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1858 SmallVector<const SCEV *, 4> NewOps;
1859 NewOps.reserve(AddRec->getNumOperands());
1860 const SCEV *Scale = getMulExpr(LIOps);
1861 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1862 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1863
1864 // Build the new addrec. Propagate the NUW and NSW flags if both the
1865 // outer mul and the inner addrec are guaranteed to have no overflow.
1866 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop,
1867 HasNUW && AddRec->hasNoUnsignedWrap(),
1868 HasNSW && AddRec->hasNoSignedWrap());
1869
1870 // If all of the other operands were loop invariant, we are done.
1871 if (Ops.size() == 1) return NewRec;
1872
1873 // Otherwise, multiply the folded AddRec by the non-liv parts.
1874 for (unsigned i = 0;; ++i)
1875 if (Ops[i] == AddRec) {
1876 Ops[i] = NewRec;
1877 break;
1878 }
1879 return getMulExpr(Ops);
1880 }
1881
1882 // Okay, if there weren't any loop invariants to be folded, check to see if
1883 // there are multiple AddRec's with the same loop induction variable being
1884 // multiplied together. If so, we can fold them.
1885 for (unsigned OtherIdx = Idx+1;
1886 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1887 ++OtherIdx)
1888 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1889 // F * G, where F = {A,+,B}<L> and G = {C,+,D}<L> -->
1890 // {A*C,+,F*D + G*B + B*D}<L>
1891 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1892 ++OtherIdx)
1893 if (const SCEVAddRecExpr *OtherAddRec =
1894 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1895 if (OtherAddRec->getLoop() == AddRecLoop) {
1896 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1897 const SCEV *NewStart = getMulExpr(F->getStart(), G->getStart());
1898 const SCEV *B = F->getStepRecurrence(*this);
1899 const SCEV *D = G->getStepRecurrence(*this);
1900 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1901 getMulExpr(G, B),
1902 getMulExpr(B, D));
1903 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1904 F->getLoop());
1905 if (Ops.size() == 2) return NewAddRec;
1906 Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
1907 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1908 }
1909 return getMulExpr(Ops);
1910 }
1911
1912 // Otherwise couldn't fold anything into this recurrence. Move onto the
1913 // next one.
1914 }
1915
1916 // Okay, it looks like we really DO need an mul expr. Check to see if we
1917 // already have one, otherwise create a new one.
1918 FoldingSetNodeID ID;
1919 ID.AddInteger(scMulExpr);
1920 ID.AddInteger(Ops.size());
1921 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1922 ID.AddPointer(Ops[i]);
1923 void *IP = 0;
1924 SCEVMulExpr *S =
1925 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1926 if (!S) {
1927 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1928 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1929 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
1930 O, Ops.size());
1931 UniqueSCEVs.InsertNode(S, IP);
1932 }
1933 if (HasNUW) S->setHasNoUnsignedWrap(true);
1934 if (HasNSW) S->setHasNoSignedWrap(true);
1935 return S;
1936 }
1937
1938 /// getUDivExpr - Get a canonical unsigned division expression, or something
1939 /// simpler if possible.
getUDivExpr(const SCEV * LHS,const SCEV * RHS)1940 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
1941 const SCEV *RHS) {
1942 assert(getEffectiveSCEVType(LHS->getType()) ==
1943 getEffectiveSCEVType(RHS->getType()) &&
1944 "SCEVUDivExpr operand types don't match!");
1945
1946 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
1947 if (RHSC->getValue()->equalsInt(1))
1948 return LHS; // X udiv 1 --> x
1949 // If the denominator is zero, the result of the udiv is undefined. Don't
1950 // try to analyze it, because the resolution chosen here may differ from
1951 // the resolution chosen in other parts of the compiler.
1952 if (!RHSC->getValue()->isZero()) {
1953 // Determine if the division can be folded into the operands of
1954 // its operands.
1955 // TODO: Generalize this to non-constants by using known-bits information.
1956 const Type *Ty = LHS->getType();
1957 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
1958 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
1959 // For non-power-of-two values, effectively round the value up to the
1960 // nearest power of two.
1961 if (!RHSC->getValue()->getValue().isPowerOf2())
1962 ++MaxShiftAmt;
1963 const IntegerType *ExtTy =
1964 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
1965 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
1966 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
1967 if (const SCEVConstant *Step =
1968 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
1969 if (!Step->getValue()->getValue()
1970 .urem(RHSC->getValue()->getValue()) &&
1971 getZeroExtendExpr(AR, ExtTy) ==
1972 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
1973 getZeroExtendExpr(Step, ExtTy),
1974 AR->getLoop())) {
1975 SmallVector<const SCEV *, 4> Operands;
1976 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
1977 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
1978 return getAddRecExpr(Operands, AR->getLoop());
1979 }
1980 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
1981 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
1982 SmallVector<const SCEV *, 4> Operands;
1983 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
1984 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
1985 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
1986 // Find an operand that's safely divisible.
1987 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
1988 const SCEV *Op = M->getOperand(i);
1989 const SCEV *Div = getUDivExpr(Op, RHSC);
1990 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
1991 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
1992 M->op_end());
1993 Operands[i] = Div;
1994 return getMulExpr(Operands);
1995 }
1996 }
1997 }
1998 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
1999 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
2000 SmallVector<const SCEV *, 4> Operands;
2001 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
2002 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
2003 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2004 Operands.clear();
2005 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2006 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2007 if (isa<SCEVUDivExpr>(Op) ||
2008 getMulExpr(Op, RHS) != A->getOperand(i))
2009 break;
2010 Operands.push_back(Op);
2011 }
2012 if (Operands.size() == A->getNumOperands())
2013 return getAddExpr(Operands);
2014 }
2015 }
2016
2017 // Fold if both operands are constant.
2018 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2019 Constant *LHSCV = LHSC->getValue();
2020 Constant *RHSCV = RHSC->getValue();
2021 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2022 RHSCV)));
2023 }
2024 }
2025 }
2026
2027 FoldingSetNodeID ID;
2028 ID.AddInteger(scUDivExpr);
2029 ID.AddPointer(LHS);
2030 ID.AddPointer(RHS);
2031 void *IP = 0;
2032 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2033 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2034 LHS, RHS);
2035 UniqueSCEVs.InsertNode(S, IP);
2036 return S;
2037 }
2038
2039
2040 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2041 /// Simplify the expression as much as possible.
getAddRecExpr(const SCEV * Start,const SCEV * Step,const Loop * L,bool HasNUW,bool HasNSW)2042 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
2043 const SCEV *Step, const Loop *L,
2044 bool HasNUW, bool HasNSW) {
2045 SmallVector<const SCEV *, 4> Operands;
2046 Operands.push_back(Start);
2047 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2048 if (StepChrec->getLoop() == L) {
2049 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2050 return getAddRecExpr(Operands, L);
2051 }
2052
2053 Operands.push_back(Step);
2054 return getAddRecExpr(Operands, L, HasNUW, HasNSW);
2055 }
2056
2057 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2058 /// Simplify the expression as much as possible.
2059 const SCEV *
getAddRecExpr(SmallVectorImpl<const SCEV * > & Operands,const Loop * L,bool HasNUW,bool HasNSW)2060 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2061 const Loop *L,
2062 bool HasNUW, bool HasNSW) {
2063 if (Operands.size() == 1) return Operands[0];
2064 #ifndef NDEBUG
2065 const Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2066 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2067 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2068 "SCEVAddRecExpr operand types don't match!");
2069 #endif
2070
2071 if (Operands.back()->isZero()) {
2072 Operands.pop_back();
2073 return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0} --> X
2074 }
2075
2076 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2077 // use that information to infer NUW and NSW flags. However, computing a
2078 // BE count requires calling getAddRecExpr, so we may not yet have a
2079 // meaningful BE count at this point (and if we don't, we'd be stuck
2080 // with a SCEVCouldNotCompute as the cached BE count).
2081
2082 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
2083 if (!HasNUW && HasNSW) {
2084 bool All = true;
2085 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2086 E = Operands.end(); I != E; ++I)
2087 if (!isKnownNonNegative(*I)) {
2088 All = false;
2089 break;
2090 }
2091 if (All) HasNUW = true;
2092 }
2093
2094 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2095 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2096 const Loop *NestedLoop = NestedAR->getLoop();
2097 if (L->contains(NestedLoop) ?
2098 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2099 (!NestedLoop->contains(L) &&
2100 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2101 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2102 NestedAR->op_end());
2103 Operands[0] = NestedAR->getStart();
2104 // AddRecs require their operands be loop-invariant with respect to their
2105 // loops. Don't perform this transformation if it would break this
2106 // requirement.
2107 bool AllInvariant = true;
2108 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2109 if (!Operands[i]->isLoopInvariant(L)) {
2110 AllInvariant = false;
2111 break;
2112 }
2113 if (AllInvariant) {
2114 NestedOperands[0] = getAddRecExpr(Operands, L);
2115 AllInvariant = true;
2116 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2117 if (!NestedOperands[i]->isLoopInvariant(NestedLoop)) {
2118 AllInvariant = false;
2119 break;
2120 }
2121 if (AllInvariant)
2122 // Ok, both add recurrences are valid after the transformation.
2123 return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
2124 }
2125 // Reset Operands to its original state.
2126 Operands[0] = NestedAR;
2127 }
2128 }
2129
2130 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2131 // already have one, otherwise create a new one.
2132 FoldingSetNodeID ID;
2133 ID.AddInteger(scAddRecExpr);
2134 ID.AddInteger(Operands.size());
2135 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2136 ID.AddPointer(Operands[i]);
2137 ID.AddPointer(L);
2138 void *IP = 0;
2139 SCEVAddRecExpr *S =
2140 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2141 if (!S) {
2142 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2143 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2144 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2145 O, Operands.size(), L);
2146 UniqueSCEVs.InsertNode(S, IP);
2147 }
2148 if (HasNUW) S->setHasNoUnsignedWrap(true);
2149 if (HasNSW) S->setHasNoSignedWrap(true);
2150 return S;
2151 }
2152
getSMaxExpr(const SCEV * LHS,const SCEV * RHS)2153 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2154 const SCEV *RHS) {
2155 SmallVector<const SCEV *, 2> Ops;
2156 Ops.push_back(LHS);
2157 Ops.push_back(RHS);
2158 return getSMaxExpr(Ops);
2159 }
2160
2161 const SCEV *
getSMaxExpr(SmallVectorImpl<const SCEV * > & Ops)2162 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2163 assert(!Ops.empty() && "Cannot get empty smax!");
2164 if (Ops.size() == 1) return Ops[0];
2165 #ifndef NDEBUG
2166 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2167 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2168 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2169 "SCEVSMaxExpr operand types don't match!");
2170 #endif
2171
2172 // Sort by complexity, this groups all similar expression types together.
2173 GroupByComplexity(Ops, LI);
2174
2175 // If there are any constants, fold them together.
2176 unsigned Idx = 0;
2177 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2178 ++Idx;
2179 assert(Idx < Ops.size());
2180 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2181 // We found two constants, fold them together!
2182 ConstantInt *Fold = ConstantInt::get(getContext(),
2183 APIntOps::smax(LHSC->getValue()->getValue(),
2184 RHSC->getValue()->getValue()));
2185 Ops[0] = getConstant(Fold);
2186 Ops.erase(Ops.begin()+1); // Erase the folded element
2187 if (Ops.size() == 1) return Ops[0];
2188 LHSC = cast<SCEVConstant>(Ops[0]);
2189 }
2190
2191 // If we are left with a constant minimum-int, strip it off.
2192 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2193 Ops.erase(Ops.begin());
2194 --Idx;
2195 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2196 // If we have an smax with a constant maximum-int, it will always be
2197 // maximum-int.
2198 return Ops[0];
2199 }
2200
2201 if (Ops.size() == 1) return Ops[0];
2202 }
2203
2204 // Find the first SMax
2205 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2206 ++Idx;
2207
2208 // Check to see if one of the operands is an SMax. If so, expand its operands
2209 // onto our operand list, and recurse to simplify.
2210 if (Idx < Ops.size()) {
2211 bool DeletedSMax = false;
2212 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2213 Ops.erase(Ops.begin()+Idx);
2214 Ops.append(SMax->op_begin(), SMax->op_end());
2215 DeletedSMax = true;
2216 }
2217
2218 if (DeletedSMax)
2219 return getSMaxExpr(Ops);
2220 }
2221
2222 // Okay, check to see if the same value occurs in the operand list twice. If
2223 // so, delete one. Since we sorted the list, these values are required to
2224 // be adjacent.
2225 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2226 // X smax Y smax Y --> X smax Y
2227 // X smax Y --> X, if X is always greater than Y
2228 if (Ops[i] == Ops[i+1] ||
2229 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2230 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2231 --i; --e;
2232 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2233 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2234 --i; --e;
2235 }
2236
2237 if (Ops.size() == 1) return Ops[0];
2238
2239 assert(!Ops.empty() && "Reduced smax down to nothing!");
2240
2241 // Okay, it looks like we really DO need an smax expr. Check to see if we
2242 // already have one, otherwise create a new one.
2243 FoldingSetNodeID ID;
2244 ID.AddInteger(scSMaxExpr);
2245 ID.AddInteger(Ops.size());
2246 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2247 ID.AddPointer(Ops[i]);
2248 void *IP = 0;
2249 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2250 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2251 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2252 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2253 O, Ops.size());
2254 UniqueSCEVs.InsertNode(S, IP);
2255 return S;
2256 }
2257
getUMaxExpr(const SCEV * LHS,const SCEV * RHS)2258 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2259 const SCEV *RHS) {
2260 SmallVector<const SCEV *, 2> Ops;
2261 Ops.push_back(LHS);
2262 Ops.push_back(RHS);
2263 return getUMaxExpr(Ops);
2264 }
2265
2266 const SCEV *
getUMaxExpr(SmallVectorImpl<const SCEV * > & Ops)2267 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2268 assert(!Ops.empty() && "Cannot get empty umax!");
2269 if (Ops.size() == 1) return Ops[0];
2270 #ifndef NDEBUG
2271 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2272 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2273 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2274 "SCEVUMaxExpr operand types don't match!");
2275 #endif
2276
2277 // Sort by complexity, this groups all similar expression types together.
2278 GroupByComplexity(Ops, LI);
2279
2280 // If there are any constants, fold them together.
2281 unsigned Idx = 0;
2282 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2283 ++Idx;
2284 assert(Idx < Ops.size());
2285 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2286 // We found two constants, fold them together!
2287 ConstantInt *Fold = ConstantInt::get(getContext(),
2288 APIntOps::umax(LHSC->getValue()->getValue(),
2289 RHSC->getValue()->getValue()));
2290 Ops[0] = getConstant(Fold);
2291 Ops.erase(Ops.begin()+1); // Erase the folded element
2292 if (Ops.size() == 1) return Ops[0];
2293 LHSC = cast<SCEVConstant>(Ops[0]);
2294 }
2295
2296 // If we are left with a constant minimum-int, strip it off.
2297 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2298 Ops.erase(Ops.begin());
2299 --Idx;
2300 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2301 // If we have an umax with a constant maximum-int, it will always be
2302 // maximum-int.
2303 return Ops[0];
2304 }
2305
2306 if (Ops.size() == 1) return Ops[0];
2307 }
2308
2309 // Find the first UMax
2310 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2311 ++Idx;
2312
2313 // Check to see if one of the operands is a UMax. If so, expand its operands
2314 // onto our operand list, and recurse to simplify.
2315 if (Idx < Ops.size()) {
2316 bool DeletedUMax = false;
2317 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2318 Ops.erase(Ops.begin()+Idx);
2319 Ops.append(UMax->op_begin(), UMax->op_end());
2320 DeletedUMax = true;
2321 }
2322
2323 if (DeletedUMax)
2324 return getUMaxExpr(Ops);
2325 }
2326
2327 // Okay, check to see if the same value occurs in the operand list twice. If
2328 // so, delete one. Since we sorted the list, these values are required to
2329 // be adjacent.
2330 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2331 // X umax Y umax Y --> X umax Y
2332 // X umax Y --> X, if X is always greater than Y
2333 if (Ops[i] == Ops[i+1] ||
2334 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2335 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2336 --i; --e;
2337 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2338 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2339 --i; --e;
2340 }
2341
2342 if (Ops.size() == 1) return Ops[0];
2343
2344 assert(!Ops.empty() && "Reduced umax down to nothing!");
2345
2346 // Okay, it looks like we really DO need a umax expr. Check to see if we
2347 // already have one, otherwise create a new one.
2348 FoldingSetNodeID ID;
2349 ID.AddInteger(scUMaxExpr);
2350 ID.AddInteger(Ops.size());
2351 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2352 ID.AddPointer(Ops[i]);
2353 void *IP = 0;
2354 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2355 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2356 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2357 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2358 O, Ops.size());
2359 UniqueSCEVs.InsertNode(S, IP);
2360 return S;
2361 }
2362
getSMinExpr(const SCEV * LHS,const SCEV * RHS)2363 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2364 const SCEV *RHS) {
2365 // ~smax(~x, ~y) == smin(x, y).
2366 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2367 }
2368
getUMinExpr(const SCEV * LHS,const SCEV * RHS)2369 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2370 const SCEV *RHS) {
2371 // ~umax(~x, ~y) == umin(x, y)
2372 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2373 }
2374
getSizeOfExpr(const Type * AllocTy)2375 const SCEV *ScalarEvolution::getSizeOfExpr(const Type *AllocTy) {
2376 // If we have TargetData, we can bypass creating a target-independent
2377 // constant expression and then folding it back into a ConstantInt.
2378 // This is just a compile-time optimization.
2379 if (TD)
2380 return getConstant(TD->getIntPtrType(getContext()),
2381 TD->getTypeAllocSize(AllocTy));
2382
2383 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2384 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2385 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2386 C = Folded;
2387 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2388 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2389 }
2390
getAlignOfExpr(const Type * AllocTy)2391 const SCEV *ScalarEvolution::getAlignOfExpr(const Type *AllocTy) {
2392 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2393 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2394 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2395 C = Folded;
2396 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2397 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2398 }
2399
getOffsetOfExpr(const StructType * STy,unsigned FieldNo)2400 const SCEV *ScalarEvolution::getOffsetOfExpr(const StructType *STy,
2401 unsigned FieldNo) {
2402 // If we have TargetData, we can bypass creating a target-independent
2403 // constant expression and then folding it back into a ConstantInt.
2404 // This is just a compile-time optimization.
2405 if (TD)
2406 return getConstant(TD->getIntPtrType(getContext()),
2407 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2408
2409 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2410 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2411 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2412 C = Folded;
2413 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2414 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2415 }
2416
getOffsetOfExpr(const Type * CTy,Constant * FieldNo)2417 const SCEV *ScalarEvolution::getOffsetOfExpr(const Type *CTy,
2418 Constant *FieldNo) {
2419 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2420 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2421 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2422 C = Folded;
2423 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2424 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2425 }
2426
getUnknown(Value * V)2427 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2428 // Don't attempt to do anything other than create a SCEVUnknown object
2429 // here. createSCEV only calls getUnknown after checking for all other
2430 // interesting possibilities, and any other code that calls getUnknown
2431 // is doing so in order to hide a value from SCEV canonicalization.
2432
2433 FoldingSetNodeID ID;
2434 ID.AddInteger(scUnknown);
2435 ID.AddPointer(V);
2436 void *IP = 0;
2437 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
2438 assert(cast<SCEVUnknown>(S)->getValue() == V &&
2439 "Stale SCEVUnknown in uniquing map!");
2440 return S;
2441 }
2442 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
2443 FirstUnknown);
2444 FirstUnknown = cast<SCEVUnknown>(S);
2445 UniqueSCEVs.InsertNode(S, IP);
2446 return S;
2447 }
2448
2449 //===----------------------------------------------------------------------===//
2450 // Basic SCEV Analysis and PHI Idiom Recognition Code
2451 //
2452
2453 /// isSCEVable - Test if values of the given type are analyzable within
2454 /// the SCEV framework. This primarily includes integer types, and it
2455 /// can optionally include pointer types if the ScalarEvolution class
2456 /// has access to target-specific information.
isSCEVable(const Type * Ty) const2457 bool ScalarEvolution::isSCEVable(const Type *Ty) const {
2458 // Integers and pointers are always SCEVable.
2459 return Ty->isIntegerTy() || Ty->isPointerTy();
2460 }
2461
2462 /// getTypeSizeInBits - Return the size in bits of the specified type,
2463 /// for which isSCEVable must return true.
getTypeSizeInBits(const Type * Ty) const2464 uint64_t ScalarEvolution::getTypeSizeInBits(const Type *Ty) const {
2465 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2466
2467 // If we have a TargetData, use it!
2468 if (TD)
2469 return TD->getTypeSizeInBits(Ty);
2470
2471 // Integer types have fixed sizes.
2472 if (Ty->isIntegerTy())
2473 return Ty->getPrimitiveSizeInBits();
2474
2475 // The only other support type is pointer. Without TargetData, conservatively
2476 // assume pointers are 64-bit.
2477 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2478 return 64;
2479 }
2480
2481 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2482 /// the given type and which represents how SCEV will treat the given
2483 /// type, for which isSCEVable must return true. For pointer types,
2484 /// this is the pointer-sized integer type.
getEffectiveSCEVType(const Type * Ty) const2485 const Type *ScalarEvolution::getEffectiveSCEVType(const Type *Ty) const {
2486 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2487
2488 if (Ty->isIntegerTy())
2489 return Ty;
2490
2491 // The only other support type is pointer.
2492 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2493 if (TD) return TD->getIntPtrType(getContext());
2494
2495 // Without TargetData, conservatively assume pointers are 64-bit.
2496 return Type::getInt64Ty(getContext());
2497 }
2498
getCouldNotCompute()2499 const SCEV *ScalarEvolution::getCouldNotCompute() {
2500 return &CouldNotCompute;
2501 }
2502
2503 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2504 /// expression and create a new one.
getSCEV(Value * V)2505 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2506 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2507
2508 ValueExprMapType::const_iterator I = ValueExprMap.find(V);
2509 if (I != ValueExprMap.end()) return I->second;
2510 const SCEV *S = createSCEV(V);
2511
2512 // The process of creating a SCEV for V may have caused other SCEVs
2513 // to have been created, so it's necessary to insert the new entry
2514 // from scratch, rather than trying to remember the insert position
2515 // above.
2516 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2517 return S;
2518 }
2519
2520 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2521 ///
getNegativeSCEV(const SCEV * V)2522 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2523 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2524 return getConstant(
2525 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2526
2527 const Type *Ty = V->getType();
2528 Ty = getEffectiveSCEVType(Ty);
2529 return getMulExpr(V,
2530 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2531 }
2532
2533 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
getNotSCEV(const SCEV * V)2534 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2535 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2536 return getConstant(
2537 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2538
2539 const Type *Ty = V->getType();
2540 Ty = getEffectiveSCEVType(Ty);
2541 const SCEV *AllOnes =
2542 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2543 return getMinusSCEV(AllOnes, V);
2544 }
2545
2546 /// getMinusSCEV - Return a SCEV corresponding to LHS - RHS.
2547 ///
getMinusSCEV(const SCEV * LHS,const SCEV * RHS)2548 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
2549 const SCEV *RHS) {
2550 // Fast path: X - X --> 0.
2551 if (LHS == RHS)
2552 return getConstant(LHS->getType(), 0);
2553
2554 // X - Y --> X + -Y
2555 return getAddExpr(LHS, getNegativeSCEV(RHS));
2556 }
2557
2558 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2559 /// input value to the specified type. If the type must be extended, it is zero
2560 /// extended.
2561 const SCEV *
getTruncateOrZeroExtend(const SCEV * V,const Type * Ty)2562 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V,
2563 const Type *Ty) {
2564 const Type *SrcTy = V->getType();
2565 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2566 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2567 "Cannot truncate or zero extend with non-integer arguments!");
2568 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2569 return V; // No conversion
2570 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2571 return getTruncateExpr(V, Ty);
2572 return getZeroExtendExpr(V, Ty);
2573 }
2574
2575 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2576 /// input value to the specified type. If the type must be extended, it is sign
2577 /// extended.
2578 const SCEV *
getTruncateOrSignExtend(const SCEV * V,const Type * Ty)2579 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2580 const Type *Ty) {
2581 const Type *SrcTy = V->getType();
2582 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2583 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2584 "Cannot truncate or zero extend with non-integer arguments!");
2585 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2586 return V; // No conversion
2587 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2588 return getTruncateExpr(V, Ty);
2589 return getSignExtendExpr(V, Ty);
2590 }
2591
2592 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2593 /// input value to the specified type. If the type must be extended, it is zero
2594 /// extended. The conversion must not be narrowing.
2595 const SCEV *
getNoopOrZeroExtend(const SCEV * V,const Type * Ty)2596 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, const Type *Ty) {
2597 const Type *SrcTy = V->getType();
2598 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2599 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2600 "Cannot noop or zero extend with non-integer arguments!");
2601 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2602 "getNoopOrZeroExtend cannot truncate!");
2603 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2604 return V; // No conversion
2605 return getZeroExtendExpr(V, Ty);
2606 }
2607
2608 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2609 /// input value to the specified type. If the type must be extended, it is sign
2610 /// extended. The conversion must not be narrowing.
2611 const SCEV *
getNoopOrSignExtend(const SCEV * V,const Type * Ty)2612 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, const Type *Ty) {
2613 const Type *SrcTy = V->getType();
2614 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2615 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2616 "Cannot noop or sign extend with non-integer arguments!");
2617 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2618 "getNoopOrSignExtend cannot truncate!");
2619 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2620 return V; // No conversion
2621 return getSignExtendExpr(V, Ty);
2622 }
2623
2624 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2625 /// the input value to the specified type. If the type must be extended,
2626 /// it is extended with unspecified bits. The conversion must not be
2627 /// narrowing.
2628 const SCEV *
getNoopOrAnyExtend(const SCEV * V,const Type * Ty)2629 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, const Type *Ty) {
2630 const Type *SrcTy = V->getType();
2631 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2632 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2633 "Cannot noop or any extend with non-integer arguments!");
2634 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2635 "getNoopOrAnyExtend cannot truncate!");
2636 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2637 return V; // No conversion
2638 return getAnyExtendExpr(V, Ty);
2639 }
2640
2641 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2642 /// input value to the specified type. The conversion must not be widening.
2643 const SCEV *
getTruncateOrNoop(const SCEV * V,const Type * Ty)2644 ScalarEvolution::getTruncateOrNoop(const SCEV *V, const Type *Ty) {
2645 const Type *SrcTy = V->getType();
2646 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2647 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2648 "Cannot truncate or noop with non-integer arguments!");
2649 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2650 "getTruncateOrNoop cannot extend!");
2651 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2652 return V; // No conversion
2653 return getTruncateExpr(V, Ty);
2654 }
2655
2656 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2657 /// the types using zero-extension, and then perform a umax operation
2658 /// with them.
getUMaxFromMismatchedTypes(const SCEV * LHS,const SCEV * RHS)2659 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2660 const SCEV *RHS) {
2661 const SCEV *PromotedLHS = LHS;
2662 const SCEV *PromotedRHS = RHS;
2663
2664 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2665 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2666 else
2667 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2668
2669 return getUMaxExpr(PromotedLHS, PromotedRHS);
2670 }
2671
2672 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2673 /// the types using zero-extension, and then perform a umin operation
2674 /// with them.
getUMinFromMismatchedTypes(const SCEV * LHS,const SCEV * RHS)2675 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2676 const SCEV *RHS) {
2677 const SCEV *PromotedLHS = LHS;
2678 const SCEV *PromotedRHS = RHS;
2679
2680 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2681 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2682 else
2683 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2684
2685 return getUMinExpr(PromotedLHS, PromotedRHS);
2686 }
2687
2688 /// PushDefUseChildren - Push users of the given Instruction
2689 /// onto the given Worklist.
2690 static void
PushDefUseChildren(Instruction * I,SmallVectorImpl<Instruction * > & Worklist)2691 PushDefUseChildren(Instruction *I,
2692 SmallVectorImpl<Instruction *> &Worklist) {
2693 // Push the def-use children onto the Worklist stack.
2694 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2695 UI != UE; ++UI)
2696 Worklist.push_back(cast<Instruction>(*UI));
2697 }
2698
2699 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2700 /// instructions that depend on the given instruction and removes them from
2701 /// the ValueExprMapType map if they reference SymName. This is used during PHI
2702 /// resolution.
2703 void
ForgetSymbolicName(Instruction * PN,const SCEV * SymName)2704 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2705 SmallVector<Instruction *, 16> Worklist;
2706 PushDefUseChildren(PN, Worklist);
2707
2708 SmallPtrSet<Instruction *, 8> Visited;
2709 Visited.insert(PN);
2710 while (!Worklist.empty()) {
2711 Instruction *I = Worklist.pop_back_val();
2712 if (!Visited.insert(I)) continue;
2713
2714 ValueExprMapType::iterator It =
2715 ValueExprMap.find(static_cast<Value *>(I));
2716 if (It != ValueExprMap.end()) {
2717 // Short-circuit the def-use traversal if the symbolic name
2718 // ceases to appear in expressions.
2719 if (It->second != SymName && !It->second->hasOperand(SymName))
2720 continue;
2721
2722 // SCEVUnknown for a PHI either means that it has an unrecognized
2723 // structure, it's a PHI that's in the progress of being computed
2724 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2725 // additional loop trip count information isn't going to change anything.
2726 // In the second case, createNodeForPHI will perform the necessary
2727 // updates on its own when it gets to that point. In the third, we do
2728 // want to forget the SCEVUnknown.
2729 if (!isa<PHINode>(I) ||
2730 !isa<SCEVUnknown>(It->second) ||
2731 (I != PN && It->second == SymName)) {
2732 ValuesAtScopes.erase(It->second);
2733 ValueExprMap.erase(It);
2734 }
2735 }
2736
2737 PushDefUseChildren(I, Worklist);
2738 }
2739 }
2740
2741 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2742 /// a loop header, making it a potential recurrence, or it doesn't.
2743 ///
createNodeForPHI(PHINode * PN)2744 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2745 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2746 if (L->getHeader() == PN->getParent()) {
2747 // The loop may have multiple entrances or multiple exits; we can analyze
2748 // this phi as an addrec if it has a unique entry value and a unique
2749 // backedge value.
2750 Value *BEValueV = 0, *StartValueV = 0;
2751 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2752 Value *V = PN->getIncomingValue(i);
2753 if (L->contains(PN->getIncomingBlock(i))) {
2754 if (!BEValueV) {
2755 BEValueV = V;
2756 } else if (BEValueV != V) {
2757 BEValueV = 0;
2758 break;
2759 }
2760 } else if (!StartValueV) {
2761 StartValueV = V;
2762 } else if (StartValueV != V) {
2763 StartValueV = 0;
2764 break;
2765 }
2766 }
2767 if (BEValueV && StartValueV) {
2768 // While we are analyzing this PHI node, handle its value symbolically.
2769 const SCEV *SymbolicName = getUnknown(PN);
2770 assert(ValueExprMap.find(PN) == ValueExprMap.end() &&
2771 "PHI node already processed?");
2772 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2773
2774 // Using this symbolic name for the PHI, analyze the value coming around
2775 // the back-edge.
2776 const SCEV *BEValue = getSCEV(BEValueV);
2777
2778 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2779 // has a special value for the first iteration of the loop.
2780
2781 // If the value coming around the backedge is an add with the symbolic
2782 // value we just inserted, then we found a simple induction variable!
2783 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2784 // If there is a single occurrence of the symbolic value, replace it
2785 // with a recurrence.
2786 unsigned FoundIndex = Add->getNumOperands();
2787 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2788 if (Add->getOperand(i) == SymbolicName)
2789 if (FoundIndex == e) {
2790 FoundIndex = i;
2791 break;
2792 }
2793
2794 if (FoundIndex != Add->getNumOperands()) {
2795 // Create an add with everything but the specified operand.
2796 SmallVector<const SCEV *, 8> Ops;
2797 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2798 if (i != FoundIndex)
2799 Ops.push_back(Add->getOperand(i));
2800 const SCEV *Accum = getAddExpr(Ops);
2801
2802 // This is not a valid addrec if the step amount is varying each
2803 // loop iteration, but is not itself an addrec in this loop.
2804 if (Accum->isLoopInvariant(L) ||
2805 (isa<SCEVAddRecExpr>(Accum) &&
2806 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2807 bool HasNUW = false;
2808 bool HasNSW = false;
2809
2810 // If the increment doesn't overflow, then neither the addrec nor
2811 // the post-increment will overflow.
2812 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2813 if (OBO->hasNoUnsignedWrap())
2814 HasNUW = true;
2815 if (OBO->hasNoSignedWrap())
2816 HasNSW = true;
2817 }
2818
2819 const SCEV *StartVal = getSCEV(StartValueV);
2820 const SCEV *PHISCEV =
2821 getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
2822
2823 // Since the no-wrap flags are on the increment, they apply to the
2824 // post-incremented value as well.
2825 if (Accum->isLoopInvariant(L))
2826 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2827 Accum, L, HasNUW, HasNSW);
2828
2829 // Okay, for the entire analysis of this edge we assumed the PHI
2830 // to be symbolic. We now need to go back and purge all of the
2831 // entries for the scalars that use the symbolic expression.
2832 ForgetSymbolicName(PN, SymbolicName);
2833 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2834 return PHISCEV;
2835 }
2836 }
2837 } else if (const SCEVAddRecExpr *AddRec =
2838 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2839 // Otherwise, this could be a loop like this:
2840 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2841 // In this case, j = {1,+,1} and BEValue is j.
2842 // Because the other in-value of i (0) fits the evolution of BEValue
2843 // i really is an addrec evolution.
2844 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2845 const SCEV *StartVal = getSCEV(StartValueV);
2846
2847 // If StartVal = j.start - j.stride, we can use StartVal as the
2848 // initial step of the addrec evolution.
2849 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2850 AddRec->getOperand(1))) {
2851 const SCEV *PHISCEV =
2852 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
2853
2854 // Okay, for the entire analysis of this edge we assumed the PHI
2855 // to be symbolic. We now need to go back and purge all of the
2856 // entries for the scalars that use the symbolic expression.
2857 ForgetSymbolicName(PN, SymbolicName);
2858 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2859 return PHISCEV;
2860 }
2861 }
2862 }
2863 }
2864 }
2865
2866 // If the PHI has a single incoming value, follow that value, unless the
2867 // PHI's incoming blocks are in a different loop, in which case doing so
2868 // risks breaking LCSSA form. Instcombine would normally zap these, but
2869 // it doesn't have DominatorTree information, so it may miss cases.
2870 if (Value *V = PN->hasConstantValue(DT)) {
2871 bool AllSameLoop = true;
2872 Loop *PNLoop = LI->getLoopFor(PN->getParent());
2873 for (size_t i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
2874 if (LI->getLoopFor(PN->getIncomingBlock(i)) != PNLoop) {
2875 AllSameLoop = false;
2876 break;
2877 }
2878 if (AllSameLoop)
2879 return getSCEV(V);
2880 }
2881
2882 // If it's not a loop phi, we can't handle it yet.
2883 return getUnknown(PN);
2884 }
2885
2886 /// createNodeForGEP - Expand GEP instructions into add and multiply
2887 /// operations. This allows them to be analyzed by regular SCEV code.
2888 ///
createNodeForGEP(GEPOperator * GEP)2889 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
2890
2891 // Don't blindly transfer the inbounds flag from the GEP instruction to the
2892 // Add expression, because the Instruction may be guarded by control flow
2893 // and the no-overflow bits may not be valid for the expression in any
2894 // context.
2895
2896 const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
2897 Value *Base = GEP->getOperand(0);
2898 // Don't attempt to analyze GEPs over unsized objects.
2899 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
2900 return getUnknown(GEP);
2901 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
2902 gep_type_iterator GTI = gep_type_begin(GEP);
2903 for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
2904 E = GEP->op_end();
2905 I != E; ++I) {
2906 Value *Index = *I;
2907 // Compute the (potentially symbolic) offset in bytes for this index.
2908 if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
2909 // For a struct, add the member offset.
2910 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
2911 const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
2912
2913 // Add the field offset to the running total offset.
2914 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
2915 } else {
2916 // For an array, add the element offset, explicitly scaled.
2917 const SCEV *ElementSize = getSizeOfExpr(*GTI);
2918 const SCEV *IndexS = getSCEV(Index);
2919 // Getelementptr indices are signed.
2920 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
2921
2922 // Multiply the index by the element size to compute the element offset.
2923 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize);
2924
2925 // Add the element offset to the running total offset.
2926 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
2927 }
2928 }
2929
2930 // Get the SCEV for the GEP base.
2931 const SCEV *BaseS = getSCEV(Base);
2932
2933 // Add the total offset from all the GEP indices to the base.
2934 return getAddExpr(BaseS, TotalOffset);
2935 }
2936
2937 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
2938 /// guaranteed to end in (at every loop iteration). It is, at the same time,
2939 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
2940 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
2941 uint32_t
GetMinTrailingZeros(const SCEV * S)2942 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
2943 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2944 return C->getValue()->getValue().countTrailingZeros();
2945
2946 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
2947 return std::min(GetMinTrailingZeros(T->getOperand()),
2948 (uint32_t)getTypeSizeInBits(T->getType()));
2949
2950 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
2951 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2952 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2953 getTypeSizeInBits(E->getType()) : OpRes;
2954 }
2955
2956 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
2957 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2958 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2959 getTypeSizeInBits(E->getType()) : OpRes;
2960 }
2961
2962 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
2963 // The result is the min of all operands results.
2964 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2965 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2966 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2967 return MinOpRes;
2968 }
2969
2970 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
2971 // The result is the sum of all operands results.
2972 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
2973 uint32_t BitWidth = getTypeSizeInBits(M->getType());
2974 for (unsigned i = 1, e = M->getNumOperands();
2975 SumOpRes != BitWidth && i != e; ++i)
2976 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
2977 BitWidth);
2978 return SumOpRes;
2979 }
2980
2981 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
2982 // The result is the min of all operands results.
2983 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2984 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2985 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2986 return MinOpRes;
2987 }
2988
2989 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
2990 // The result is the min of all operands results.
2991 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2992 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2993 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2994 return MinOpRes;
2995 }
2996
2997 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
2998 // The result is the min of all operands results.
2999 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3000 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3001 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3002 return MinOpRes;
3003 }
3004
3005 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3006 // For a SCEVUnknown, ask ValueTracking.
3007 unsigned BitWidth = getTypeSizeInBits(U->getType());
3008 APInt Mask = APInt::getAllOnesValue(BitWidth);
3009 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3010 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
3011 return Zeros.countTrailingOnes();
3012 }
3013
3014 // SCEVUDivExpr
3015 return 0;
3016 }
3017
3018 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
3019 ///
3020 ConstantRange
getUnsignedRange(const SCEV * S)3021 ScalarEvolution::getUnsignedRange(const SCEV *S) {
3022
3023 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3024 return ConstantRange(C->getValue()->getValue());
3025
3026 unsigned BitWidth = getTypeSizeInBits(S->getType());
3027 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3028
3029 // If the value has known zeros, the maximum unsigned value will have those
3030 // known zeros as well.
3031 uint32_t TZ = GetMinTrailingZeros(S);
3032 if (TZ != 0)
3033 ConservativeResult =
3034 ConstantRange(APInt::getMinValue(BitWidth),
3035 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3036
3037 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3038 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3039 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3040 X = X.add(getUnsignedRange(Add->getOperand(i)));
3041 return ConservativeResult.intersectWith(X);
3042 }
3043
3044 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3045 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3046 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3047 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3048 return ConservativeResult.intersectWith(X);
3049 }
3050
3051 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3052 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3053 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3054 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3055 return ConservativeResult.intersectWith(X);
3056 }
3057
3058 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3059 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3060 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3061 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3062 return ConservativeResult.intersectWith(X);
3063 }
3064
3065 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3066 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3067 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3068 return ConservativeResult.intersectWith(X.udiv(Y));
3069 }
3070
3071 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3072 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3073 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
3074 }
3075
3076 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3077 ConstantRange X = getUnsignedRange(SExt->getOperand());
3078 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
3079 }
3080
3081 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3082 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3083 return ConservativeResult.intersectWith(X.truncate(BitWidth));
3084 }
3085
3086 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3087 // If there's no unsigned wrap, the value will never be less than its
3088 // initial value.
3089 if (AddRec->hasNoUnsignedWrap())
3090 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3091 if (!C->getValue()->isZero())
3092 ConservativeResult =
3093 ConservativeResult.intersectWith(
3094 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3095
3096 // TODO: non-affine addrec
3097 if (AddRec->isAffine()) {
3098 const Type *Ty = AddRec->getType();
3099 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3100 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3101 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3102 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3103
3104 const SCEV *Start = AddRec->getStart();
3105 const SCEV *Step = AddRec->getStepRecurrence(*this);
3106
3107 ConstantRange StartRange = getUnsignedRange(Start);
3108 ConstantRange StepRange = getSignedRange(Step);
3109 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3110 ConstantRange EndRange =
3111 StartRange.add(MaxBECountRange.multiply(StepRange));
3112
3113 // Check for overflow. This must be done with ConstantRange arithmetic
3114 // because we could be called from within the ScalarEvolution overflow
3115 // checking code.
3116 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3117 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3118 ConstantRange ExtMaxBECountRange =
3119 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3120 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3121 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3122 ExtEndRange)
3123 return ConservativeResult;
3124
3125 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3126 EndRange.getUnsignedMin());
3127 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3128 EndRange.getUnsignedMax());
3129 if (Min.isMinValue() && Max.isMaxValue())
3130 return ConservativeResult;
3131 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
3132 }
3133 }
3134
3135 return ConservativeResult;
3136 }
3137
3138 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3139 // For a SCEVUnknown, ask ValueTracking.
3140 APInt Mask = APInt::getAllOnesValue(BitWidth);
3141 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3142 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3143 if (Ones == ~Zeros + 1)
3144 return ConservativeResult;
3145 return ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
3146 }
3147
3148 return ConservativeResult;
3149 }
3150
3151 /// getSignedRange - Determine the signed range for a particular SCEV.
3152 ///
3153 ConstantRange
getSignedRange(const SCEV * S)3154 ScalarEvolution::getSignedRange(const SCEV *S) {
3155
3156 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3157 return ConstantRange(C->getValue()->getValue());
3158
3159 unsigned BitWidth = getTypeSizeInBits(S->getType());
3160 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3161
3162 // If the value has known zeros, the maximum signed value will have those
3163 // known zeros as well.
3164 uint32_t TZ = GetMinTrailingZeros(S);
3165 if (TZ != 0)
3166 ConservativeResult =
3167 ConstantRange(APInt::getSignedMinValue(BitWidth),
3168 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3169
3170 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3171 ConstantRange X = getSignedRange(Add->getOperand(0));
3172 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3173 X = X.add(getSignedRange(Add->getOperand(i)));
3174 return ConservativeResult.intersectWith(X);
3175 }
3176
3177 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3178 ConstantRange X = getSignedRange(Mul->getOperand(0));
3179 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3180 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3181 return ConservativeResult.intersectWith(X);
3182 }
3183
3184 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3185 ConstantRange X = getSignedRange(SMax->getOperand(0));
3186 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3187 X = X.smax(getSignedRange(SMax->getOperand(i)));
3188 return ConservativeResult.intersectWith(X);
3189 }
3190
3191 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3192 ConstantRange X = getSignedRange(UMax->getOperand(0));
3193 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3194 X = X.umax(getSignedRange(UMax->getOperand(i)));
3195 return ConservativeResult.intersectWith(X);
3196 }
3197
3198 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3199 ConstantRange X = getSignedRange(UDiv->getLHS());
3200 ConstantRange Y = getSignedRange(UDiv->getRHS());
3201 return ConservativeResult.intersectWith(X.udiv(Y));
3202 }
3203
3204 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3205 ConstantRange X = getSignedRange(ZExt->getOperand());
3206 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
3207 }
3208
3209 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3210 ConstantRange X = getSignedRange(SExt->getOperand());
3211 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
3212 }
3213
3214 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3215 ConstantRange X = getSignedRange(Trunc->getOperand());
3216 return ConservativeResult.intersectWith(X.truncate(BitWidth));
3217 }
3218
3219 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3220 // If there's no signed wrap, and all the operands have the same sign or
3221 // zero, the value won't ever change sign.
3222 if (AddRec->hasNoSignedWrap()) {
3223 bool AllNonNeg = true;
3224 bool AllNonPos = true;
3225 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3226 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3227 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3228 }
3229 if (AllNonNeg)
3230 ConservativeResult = ConservativeResult.intersectWith(
3231 ConstantRange(APInt(BitWidth, 0),
3232 APInt::getSignedMinValue(BitWidth)));
3233 else if (AllNonPos)
3234 ConservativeResult = ConservativeResult.intersectWith(
3235 ConstantRange(APInt::getSignedMinValue(BitWidth),
3236 APInt(BitWidth, 1)));
3237 }
3238
3239 // TODO: non-affine addrec
3240 if (AddRec->isAffine()) {
3241 const Type *Ty = AddRec->getType();
3242 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3243 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3244 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3245 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3246
3247 const SCEV *Start = AddRec->getStart();
3248 const SCEV *Step = AddRec->getStepRecurrence(*this);
3249
3250 ConstantRange StartRange = getSignedRange(Start);
3251 ConstantRange StepRange = getSignedRange(Step);
3252 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3253 ConstantRange EndRange =
3254 StartRange.add(MaxBECountRange.multiply(StepRange));
3255
3256 // Check for overflow. This must be done with ConstantRange arithmetic
3257 // because we could be called from within the ScalarEvolution overflow
3258 // checking code.
3259 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3260 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3261 ConstantRange ExtMaxBECountRange =
3262 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3263 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3264 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3265 ExtEndRange)
3266 return ConservativeResult;
3267
3268 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3269 EndRange.getSignedMin());
3270 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3271 EndRange.getSignedMax());
3272 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3273 return ConservativeResult;
3274 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
3275 }
3276 }
3277
3278 return ConservativeResult;
3279 }
3280
3281 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3282 // For a SCEVUnknown, ask ValueTracking.
3283 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3284 return ConservativeResult;
3285 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3286 if (NS == 1)
3287 return ConservativeResult;
3288 return ConservativeResult.intersectWith(
3289 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3290 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1));
3291 }
3292
3293 return ConservativeResult;
3294 }
3295
3296 /// createSCEV - We know that there is no SCEV for the specified value.
3297 /// Analyze the expression.
3298 ///
createSCEV(Value * V)3299 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3300 if (!isSCEVable(V->getType()))
3301 return getUnknown(V);
3302
3303 unsigned Opcode = Instruction::UserOp1;
3304 if (Instruction *I = dyn_cast<Instruction>(V)) {
3305 Opcode = I->getOpcode();
3306
3307 // Don't attempt to analyze instructions in blocks that aren't
3308 // reachable. Such instructions don't matter, and they aren't required
3309 // to obey basic rules for definitions dominating uses which this
3310 // analysis depends on.
3311 if (!DT->isReachableFromEntry(I->getParent()))
3312 return getUnknown(V);
3313 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3314 Opcode = CE->getOpcode();
3315 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3316 return getConstant(CI);
3317 else if (isa<ConstantPointerNull>(V))
3318 return getConstant(V->getType(), 0);
3319 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3320 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3321 else
3322 return getUnknown(V);
3323
3324 Operator *U = cast<Operator>(V);
3325 switch (Opcode) {
3326 case Instruction::Add: {
3327 // The simple thing to do would be to just call getSCEV on both operands
3328 // and call getAddExpr with the result. However if we're looking at a
3329 // bunch of things all added together, this can be quite inefficient,
3330 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3331 // Instead, gather up all the operands and make a single getAddExpr call.
3332 // LLVM IR canonical form means we need only traverse the left operands.
3333 SmallVector<const SCEV *, 4> AddOps;
3334 AddOps.push_back(getSCEV(U->getOperand(1)));
3335 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
3336 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
3337 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
3338 break;
3339 U = cast<Operator>(Op);
3340 const SCEV *Op1 = getSCEV(U->getOperand(1));
3341 if (Opcode == Instruction::Sub)
3342 AddOps.push_back(getNegativeSCEV(Op1));
3343 else
3344 AddOps.push_back(Op1);
3345 }
3346 AddOps.push_back(getSCEV(U->getOperand(0)));
3347 return getAddExpr(AddOps);
3348 }
3349 case Instruction::Mul: {
3350 // See the Add code above.
3351 SmallVector<const SCEV *, 4> MulOps;
3352 MulOps.push_back(getSCEV(U->getOperand(1)));
3353 for (Value *Op = U->getOperand(0);
3354 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
3355 Op = U->getOperand(0)) {
3356 U = cast<Operator>(Op);
3357 MulOps.push_back(getSCEV(U->getOperand(1)));
3358 }
3359 MulOps.push_back(getSCEV(U->getOperand(0)));
3360 return getMulExpr(MulOps);
3361 }
3362 case Instruction::UDiv:
3363 return getUDivExpr(getSCEV(U->getOperand(0)),
3364 getSCEV(U->getOperand(1)));
3365 case Instruction::Sub:
3366 return getMinusSCEV(getSCEV(U->getOperand(0)),
3367 getSCEV(U->getOperand(1)));
3368 case Instruction::And:
3369 // For an expression like x&255 that merely masks off the high bits,
3370 // use zext(trunc(x)) as the SCEV expression.
3371 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3372 if (CI->isNullValue())
3373 return getSCEV(U->getOperand(1));
3374 if (CI->isAllOnesValue())
3375 return getSCEV(U->getOperand(0));
3376 const APInt &A = CI->getValue();
3377
3378 // Instcombine's ShrinkDemandedConstant may strip bits out of
3379 // constants, obscuring what would otherwise be a low-bits mask.
3380 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3381 // knew about to reconstruct a low-bits mask value.
3382 unsigned LZ = A.countLeadingZeros();
3383 unsigned BitWidth = A.getBitWidth();
3384 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3385 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3386 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3387
3388 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3389
3390 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3391 return
3392 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3393 IntegerType::get(getContext(), BitWidth - LZ)),
3394 U->getType());
3395 }
3396 break;
3397
3398 case Instruction::Or:
3399 // If the RHS of the Or is a constant, we may have something like:
3400 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3401 // optimizations will transparently handle this case.
3402 //
3403 // In order for this transformation to be safe, the LHS must be of the
3404 // form X*(2^n) and the Or constant must be less than 2^n.
3405 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3406 const SCEV *LHS = getSCEV(U->getOperand(0));
3407 const APInt &CIVal = CI->getValue();
3408 if (GetMinTrailingZeros(LHS) >=
3409 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3410 // Build a plain add SCEV.
3411 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3412 // If the LHS of the add was an addrec and it has no-wrap flags,
3413 // transfer the no-wrap flags, since an or won't introduce a wrap.
3414 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3415 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3416 if (OldAR->hasNoUnsignedWrap())
3417 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoUnsignedWrap(true);
3418 if (OldAR->hasNoSignedWrap())
3419 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoSignedWrap(true);
3420 }
3421 return S;
3422 }
3423 }
3424 break;
3425 case Instruction::Xor:
3426 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3427 // If the RHS of the xor is a signbit, then this is just an add.
3428 // Instcombine turns add of signbit into xor as a strength reduction step.
3429 if (CI->getValue().isSignBit())
3430 return getAddExpr(getSCEV(U->getOperand(0)),
3431 getSCEV(U->getOperand(1)));
3432
3433 // If the RHS of xor is -1, then this is a not operation.
3434 if (CI->isAllOnesValue())
3435 return getNotSCEV(getSCEV(U->getOperand(0)));
3436
3437 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3438 // This is a variant of the check for xor with -1, and it handles
3439 // the case where instcombine has trimmed non-demanded bits out
3440 // of an xor with -1.
3441 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3442 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3443 if (BO->getOpcode() == Instruction::And &&
3444 LCI->getValue() == CI->getValue())
3445 if (const SCEVZeroExtendExpr *Z =
3446 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3447 const Type *UTy = U->getType();
3448 const SCEV *Z0 = Z->getOperand();
3449 const Type *Z0Ty = Z0->getType();
3450 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3451
3452 // If C is a low-bits mask, the zero extend is serving to
3453 // mask off the high bits. Complement the operand and
3454 // re-apply the zext.
3455 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3456 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3457
3458 // If C is a single bit, it may be in the sign-bit position
3459 // before the zero-extend. In this case, represent the xor
3460 // using an add, which is equivalent, and re-apply the zext.
3461 APInt Trunc = APInt(CI->getValue()).trunc(Z0TySize);
3462 if (APInt(Trunc).zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3463 Trunc.isSignBit())
3464 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3465 UTy);
3466 }
3467 }
3468 break;
3469
3470 case Instruction::Shl:
3471 // Turn shift left of a constant amount into a multiply.
3472 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3473 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3474
3475 // If the shift count is not less than the bitwidth, the result of
3476 // the shift is undefined. Don't try to analyze it, because the
3477 // resolution chosen here may differ from the resolution chosen in
3478 // other parts of the compiler.
3479 if (SA->getValue().uge(BitWidth))
3480 break;
3481
3482 Constant *X = ConstantInt::get(getContext(),
3483 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3484 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3485 }
3486 break;
3487
3488 case Instruction::LShr:
3489 // Turn logical shift right of a constant into a unsigned divide.
3490 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3491 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3492
3493 // If the shift count is not less than the bitwidth, the result of
3494 // the shift is undefined. Don't try to analyze it, because the
3495 // resolution chosen here may differ from the resolution chosen in
3496 // other parts of the compiler.
3497 if (SA->getValue().uge(BitWidth))
3498 break;
3499
3500 Constant *X = ConstantInt::get(getContext(),
3501 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3502 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3503 }
3504 break;
3505
3506 case Instruction::AShr:
3507 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3508 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3509 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3510 if (L->getOpcode() == Instruction::Shl &&
3511 L->getOperand(1) == U->getOperand(1)) {
3512 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3513
3514 // If the shift count is not less than the bitwidth, the result of
3515 // the shift is undefined. Don't try to analyze it, because the
3516 // resolution chosen here may differ from the resolution chosen in
3517 // other parts of the compiler.
3518 if (CI->getValue().uge(BitWidth))
3519 break;
3520
3521 uint64_t Amt = BitWidth - CI->getZExtValue();
3522 if (Amt == BitWidth)
3523 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3524 return
3525 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3526 IntegerType::get(getContext(),
3527 Amt)),
3528 U->getType());
3529 }
3530 break;
3531
3532 case Instruction::Trunc:
3533 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3534
3535 case Instruction::ZExt:
3536 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3537
3538 case Instruction::SExt:
3539 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3540
3541 case Instruction::BitCast:
3542 // BitCasts are no-op casts so we just eliminate the cast.
3543 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3544 return getSCEV(U->getOperand(0));
3545 break;
3546
3547 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3548 // lead to pointer expressions which cannot safely be expanded to GEPs,
3549 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3550 // simplifying integer expressions.
3551
3552 case Instruction::GetElementPtr:
3553 return createNodeForGEP(cast<GEPOperator>(U));
3554
3555 case Instruction::PHI:
3556 return createNodeForPHI(cast<PHINode>(U));
3557
3558 case Instruction::Select:
3559 // This could be a smax or umax that was lowered earlier.
3560 // Try to recover it.
3561 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3562 Value *LHS = ICI->getOperand(0);
3563 Value *RHS = ICI->getOperand(1);
3564 switch (ICI->getPredicate()) {
3565 case ICmpInst::ICMP_SLT:
3566 case ICmpInst::ICMP_SLE:
3567 std::swap(LHS, RHS);
3568 // fall through
3569 case ICmpInst::ICMP_SGT:
3570 case ICmpInst::ICMP_SGE:
3571 // a >s b ? a+x : b+x -> smax(a, b)+x
3572 // a >s b ? b+x : a+x -> smin(a, b)+x
3573 if (LHS->getType() == U->getType()) {
3574 const SCEV *LS = getSCEV(LHS);
3575 const SCEV *RS = getSCEV(RHS);
3576 const SCEV *LA = getSCEV(U->getOperand(1));
3577 const SCEV *RA = getSCEV(U->getOperand(2));
3578 const SCEV *LDiff = getMinusSCEV(LA, LS);
3579 const SCEV *RDiff = getMinusSCEV(RA, RS);
3580 if (LDiff == RDiff)
3581 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3582 LDiff = getMinusSCEV(LA, RS);
3583 RDiff = getMinusSCEV(RA, LS);
3584 if (LDiff == RDiff)
3585 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3586 }
3587 break;
3588 case ICmpInst::ICMP_ULT:
3589 case ICmpInst::ICMP_ULE:
3590 std::swap(LHS, RHS);
3591 // fall through
3592 case ICmpInst::ICMP_UGT:
3593 case ICmpInst::ICMP_UGE:
3594 // a >u b ? a+x : b+x -> umax(a, b)+x
3595 // a >u b ? b+x : a+x -> umin(a, b)+x
3596 if (LHS->getType() == U->getType()) {
3597 const SCEV *LS = getSCEV(LHS);
3598 const SCEV *RS = getSCEV(RHS);
3599 const SCEV *LA = getSCEV(U->getOperand(1));
3600 const SCEV *RA = getSCEV(U->getOperand(2));
3601 const SCEV *LDiff = getMinusSCEV(LA, LS);
3602 const SCEV *RDiff = getMinusSCEV(RA, RS);
3603 if (LDiff == RDiff)
3604 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3605 LDiff = getMinusSCEV(LA, RS);
3606 RDiff = getMinusSCEV(RA, LS);
3607 if (LDiff == RDiff)
3608 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3609 }
3610 break;
3611 case ICmpInst::ICMP_NE:
3612 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3613 if (LHS->getType() == U->getType() &&
3614 isa<ConstantInt>(RHS) &&
3615 cast<ConstantInt>(RHS)->isZero()) {
3616 const SCEV *One = getConstant(LHS->getType(), 1);
3617 const SCEV *LS = getSCEV(LHS);
3618 const SCEV *LA = getSCEV(U->getOperand(1));
3619 const SCEV *RA = getSCEV(U->getOperand(2));
3620 const SCEV *LDiff = getMinusSCEV(LA, LS);
3621 const SCEV *RDiff = getMinusSCEV(RA, One);
3622 if (LDiff == RDiff)
3623 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3624 }
3625 break;
3626 case ICmpInst::ICMP_EQ:
3627 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3628 if (LHS->getType() == U->getType() &&
3629 isa<ConstantInt>(RHS) &&
3630 cast<ConstantInt>(RHS)->isZero()) {
3631 const SCEV *One = getConstant(LHS->getType(), 1);
3632 const SCEV *LS = getSCEV(LHS);
3633 const SCEV *LA = getSCEV(U->getOperand(1));
3634 const SCEV *RA = getSCEV(U->getOperand(2));
3635 const SCEV *LDiff = getMinusSCEV(LA, One);
3636 const SCEV *RDiff = getMinusSCEV(RA, LS);
3637 if (LDiff == RDiff)
3638 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3639 }
3640 break;
3641 default:
3642 break;
3643 }
3644 }
3645
3646 default: // We cannot analyze this expression.
3647 break;
3648 }
3649
3650 return getUnknown(V);
3651 }
3652
3653
3654
3655 //===----------------------------------------------------------------------===//
3656 // Iteration Count Computation Code
3657 //
3658
3659 /// getBackedgeTakenCount - If the specified loop has a predictable
3660 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3661 /// object. The backedge-taken count is the number of times the loop header
3662 /// will be branched to from within the loop. This is one less than the
3663 /// trip count of the loop, since it doesn't count the first iteration,
3664 /// when the header is branched to from outside the loop.
3665 ///
3666 /// Note that it is not valid to call this method on a loop without a
3667 /// loop-invariant backedge-taken count (see
3668 /// hasLoopInvariantBackedgeTakenCount).
3669 ///
getBackedgeTakenCount(const Loop * L)3670 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3671 return getBackedgeTakenInfo(L).Exact;
3672 }
3673
3674 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3675 /// return the least SCEV value that is known never to be less than the
3676 /// actual backedge taken count.
getMaxBackedgeTakenCount(const Loop * L)3677 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3678 return getBackedgeTakenInfo(L).Max;
3679 }
3680
3681 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3682 /// onto the given Worklist.
3683 static void
PushLoopPHIs(const Loop * L,SmallVectorImpl<Instruction * > & Worklist)3684 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3685 BasicBlock *Header = L->getHeader();
3686
3687 // Push all Loop-header PHIs onto the Worklist stack.
3688 for (BasicBlock::iterator I = Header->begin();
3689 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3690 Worklist.push_back(PN);
3691 }
3692
3693 const ScalarEvolution::BackedgeTakenInfo &
getBackedgeTakenInfo(const Loop * L)3694 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3695 // Initially insert a CouldNotCompute for this loop. If the insertion
3696 // succeeds, proceed to actually compute a backedge-taken count and
3697 // update the value. The temporary CouldNotCompute value tells SCEV
3698 // code elsewhere that it shouldn't attempt to request a new
3699 // backedge-taken count, which could result in infinite recursion.
3700 std::pair<std::map<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3701 BackedgeTakenCounts.insert(std::make_pair(L, getCouldNotCompute()));
3702 if (Pair.second) {
3703 BackedgeTakenInfo BECount = ComputeBackedgeTakenCount(L);
3704 if (BECount.Exact != getCouldNotCompute()) {
3705 assert(BECount.Exact->isLoopInvariant(L) &&
3706 BECount.Max->isLoopInvariant(L) &&
3707 "Computed backedge-taken count isn't loop invariant for loop!");
3708 ++NumTripCountsComputed;
3709
3710 // Update the value in the map.
3711 Pair.first->second = BECount;
3712 } else {
3713 if (BECount.Max != getCouldNotCompute())
3714 // Update the value in the map.
3715 Pair.first->second = BECount;
3716 if (isa<PHINode>(L->getHeader()->begin()))
3717 // Only count loops that have phi nodes as not being computable.
3718 ++NumTripCountsNotComputed;
3719 }
3720
3721 // Now that we know more about the trip count for this loop, forget any
3722 // existing SCEV values for PHI nodes in this loop since they are only
3723 // conservative estimates made without the benefit of trip count
3724 // information. This is similar to the code in forgetLoop, except that
3725 // it handles SCEVUnknown PHI nodes specially.
3726 if (BECount.hasAnyInfo()) {
3727 SmallVector<Instruction *, 16> Worklist;
3728 PushLoopPHIs(L, Worklist);
3729
3730 SmallPtrSet<Instruction *, 8> Visited;
3731 while (!Worklist.empty()) {
3732 Instruction *I = Worklist.pop_back_val();
3733 if (!Visited.insert(I)) continue;
3734
3735 ValueExprMapType::iterator It =
3736 ValueExprMap.find(static_cast<Value *>(I));
3737 if (It != ValueExprMap.end()) {
3738 // SCEVUnknown for a PHI either means that it has an unrecognized
3739 // structure, or it's a PHI that's in the progress of being computed
3740 // by createNodeForPHI. In the former case, additional loop trip
3741 // count information isn't going to change anything. In the later
3742 // case, createNodeForPHI will perform the necessary updates on its
3743 // own when it gets to that point.
3744 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(It->second)) {
3745 ValuesAtScopes.erase(It->second);
3746 ValueExprMap.erase(It);
3747 }
3748 if (PHINode *PN = dyn_cast<PHINode>(I))
3749 ConstantEvolutionLoopExitValue.erase(PN);
3750 }
3751
3752 PushDefUseChildren(I, Worklist);
3753 }
3754 }
3755 }
3756 return Pair.first->second;
3757 }
3758
3759 /// forgetLoop - This method should be called by the client when it has
3760 /// changed a loop in a way that may effect ScalarEvolution's ability to
3761 /// compute a trip count, or if the loop is deleted.
forgetLoop(const Loop * L)3762 void ScalarEvolution::forgetLoop(const Loop *L) {
3763 // Drop any stored trip count value.
3764 BackedgeTakenCounts.erase(L);
3765
3766 // Drop information about expressions based on loop-header PHIs.
3767 SmallVector<Instruction *, 16> Worklist;
3768 PushLoopPHIs(L, Worklist);
3769
3770 SmallPtrSet<Instruction *, 8> Visited;
3771 while (!Worklist.empty()) {
3772 Instruction *I = Worklist.pop_back_val();
3773 if (!Visited.insert(I)) continue;
3774
3775 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3776 if (It != ValueExprMap.end()) {
3777 ValuesAtScopes.erase(It->second);
3778 ValueExprMap.erase(It);
3779 if (PHINode *PN = dyn_cast<PHINode>(I))
3780 ConstantEvolutionLoopExitValue.erase(PN);
3781 }
3782
3783 PushDefUseChildren(I, Worklist);
3784 }
3785 }
3786
3787 /// forgetValue - This method should be called by the client when it has
3788 /// changed a value in a way that may effect its value, or which may
3789 /// disconnect it from a def-use chain linking it to a loop.
forgetValue(Value * V)3790 void ScalarEvolution::forgetValue(Value *V) {
3791 Instruction *I = dyn_cast<Instruction>(V);
3792 if (!I) return;
3793
3794 // Drop information about expressions based on loop-header PHIs.
3795 SmallVector<Instruction *, 16> Worklist;
3796 Worklist.push_back(I);
3797
3798 SmallPtrSet<Instruction *, 8> Visited;
3799 while (!Worklist.empty()) {
3800 I = Worklist.pop_back_val();
3801 if (!Visited.insert(I)) continue;
3802
3803 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3804 if (It != ValueExprMap.end()) {
3805 ValuesAtScopes.erase(It->second);
3806 ValueExprMap.erase(It);
3807 if (PHINode *PN = dyn_cast<PHINode>(I))
3808 ConstantEvolutionLoopExitValue.erase(PN);
3809 }
3810
3811 PushDefUseChildren(I, Worklist);
3812 }
3813 }
3814
3815 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
3816 /// of the specified loop will execute.
3817 ScalarEvolution::BackedgeTakenInfo
ComputeBackedgeTakenCount(const Loop * L)3818 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
3819 SmallVector<BasicBlock *, 8> ExitingBlocks;
3820 L->getExitingBlocks(ExitingBlocks);
3821
3822 // Examine all exits and pick the most conservative values.
3823 const SCEV *BECount = getCouldNotCompute();
3824 const SCEV *MaxBECount = getCouldNotCompute();
3825 bool CouldNotComputeBECount = false;
3826 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
3827 BackedgeTakenInfo NewBTI =
3828 ComputeBackedgeTakenCountFromExit(L, ExitingBlocks[i]);
3829
3830 if (NewBTI.Exact == getCouldNotCompute()) {
3831 // We couldn't compute an exact value for this exit, so
3832 // we won't be able to compute an exact value for the loop.
3833 CouldNotComputeBECount = true;
3834 BECount = getCouldNotCompute();
3835 } else if (!CouldNotComputeBECount) {
3836 if (BECount == getCouldNotCompute())
3837 BECount = NewBTI.Exact;
3838 else
3839 BECount = getUMinFromMismatchedTypes(BECount, NewBTI.Exact);
3840 }
3841 if (MaxBECount == getCouldNotCompute())
3842 MaxBECount = NewBTI.Max;
3843 else if (NewBTI.Max != getCouldNotCompute())
3844 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, NewBTI.Max);
3845 }
3846
3847 return BackedgeTakenInfo(BECount, MaxBECount);
3848 }
3849
3850 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the backedge
3851 /// of the specified loop will execute if it exits via the specified block.
3852 ScalarEvolution::BackedgeTakenInfo
ComputeBackedgeTakenCountFromExit(const Loop * L,BasicBlock * ExitingBlock)3853 ScalarEvolution::ComputeBackedgeTakenCountFromExit(const Loop *L,
3854 BasicBlock *ExitingBlock) {
3855
3856 // Okay, we've chosen an exiting block. See what condition causes us to
3857 // exit at this block.
3858 //
3859 // FIXME: we should be able to handle switch instructions (with a single exit)
3860 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
3861 if (ExitBr == 0) return getCouldNotCompute();
3862 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
3863
3864 // At this point, we know we have a conditional branch that determines whether
3865 // the loop is exited. However, we don't know if the branch is executed each
3866 // time through the loop. If not, then the execution count of the branch will
3867 // not be equal to the trip count of the loop.
3868 //
3869 // Currently we check for this by checking to see if the Exit branch goes to
3870 // the loop header. If so, we know it will always execute the same number of
3871 // times as the loop. We also handle the case where the exit block *is* the
3872 // loop header. This is common for un-rotated loops.
3873 //
3874 // If both of those tests fail, walk up the unique predecessor chain to the
3875 // header, stopping if there is an edge that doesn't exit the loop. If the
3876 // header is reached, the execution count of the branch will be equal to the
3877 // trip count of the loop.
3878 //
3879 // More extensive analysis could be done to handle more cases here.
3880 //
3881 if (ExitBr->getSuccessor(0) != L->getHeader() &&
3882 ExitBr->getSuccessor(1) != L->getHeader() &&
3883 ExitBr->getParent() != L->getHeader()) {
3884 // The simple checks failed, try climbing the unique predecessor chain
3885 // up to the header.
3886 bool Ok = false;
3887 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
3888 BasicBlock *Pred = BB->getUniquePredecessor();
3889 if (!Pred)
3890 return getCouldNotCompute();
3891 TerminatorInst *PredTerm = Pred->getTerminator();
3892 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
3893 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
3894 if (PredSucc == BB)
3895 continue;
3896 // If the predecessor has a successor that isn't BB and isn't
3897 // outside the loop, assume the worst.
3898 if (L->contains(PredSucc))
3899 return getCouldNotCompute();
3900 }
3901 if (Pred == L->getHeader()) {
3902 Ok = true;
3903 break;
3904 }
3905 BB = Pred;
3906 }
3907 if (!Ok)
3908 return getCouldNotCompute();
3909 }
3910
3911 // Proceed to the next level to examine the exit condition expression.
3912 return ComputeBackedgeTakenCountFromExitCond(L, ExitBr->getCondition(),
3913 ExitBr->getSuccessor(0),
3914 ExitBr->getSuccessor(1));
3915 }
3916
3917 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
3918 /// backedge of the specified loop will execute if its exit condition
3919 /// were a conditional branch of ExitCond, TBB, and FBB.
3920 ScalarEvolution::BackedgeTakenInfo
ComputeBackedgeTakenCountFromExitCond(const Loop * L,Value * ExitCond,BasicBlock * TBB,BasicBlock * FBB)3921 ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
3922 Value *ExitCond,
3923 BasicBlock *TBB,
3924 BasicBlock *FBB) {
3925 // Check if the controlling expression for this loop is an And or Or.
3926 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
3927 if (BO->getOpcode() == Instruction::And) {
3928 // Recurse on the operands of the and.
3929 BackedgeTakenInfo BTI0 =
3930 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3931 BackedgeTakenInfo BTI1 =
3932 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3933 const SCEV *BECount = getCouldNotCompute();
3934 const SCEV *MaxBECount = getCouldNotCompute();
3935 if (L->contains(TBB)) {
3936 // Both conditions must be true for the loop to continue executing.
3937 // Choose the less conservative count.
3938 if (BTI0.Exact == getCouldNotCompute() ||
3939 BTI1.Exact == getCouldNotCompute())
3940 BECount = getCouldNotCompute();
3941 else
3942 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3943 if (BTI0.Max == getCouldNotCompute())
3944 MaxBECount = BTI1.Max;
3945 else if (BTI1.Max == getCouldNotCompute())
3946 MaxBECount = BTI0.Max;
3947 else
3948 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3949 } else {
3950 // Both conditions must be true at the same time for the loop to exit.
3951 // For now, be conservative.
3952 assert(L->contains(FBB) && "Loop block has no successor in loop!");
3953 if (BTI0.Max == BTI1.Max)
3954 MaxBECount = BTI0.Max;
3955 if (BTI0.Exact == BTI1.Exact)
3956 BECount = BTI0.Exact;
3957 }
3958
3959 return BackedgeTakenInfo(BECount, MaxBECount);
3960 }
3961 if (BO->getOpcode() == Instruction::Or) {
3962 // Recurse on the operands of the or.
3963 BackedgeTakenInfo BTI0 =
3964 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3965 BackedgeTakenInfo BTI1 =
3966 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3967 const SCEV *BECount = getCouldNotCompute();
3968 const SCEV *MaxBECount = getCouldNotCompute();
3969 if (L->contains(FBB)) {
3970 // Both conditions must be false for the loop to continue executing.
3971 // Choose the less conservative count.
3972 if (BTI0.Exact == getCouldNotCompute() ||
3973 BTI1.Exact == getCouldNotCompute())
3974 BECount = getCouldNotCompute();
3975 else
3976 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3977 if (BTI0.Max == getCouldNotCompute())
3978 MaxBECount = BTI1.Max;
3979 else if (BTI1.Max == getCouldNotCompute())
3980 MaxBECount = BTI0.Max;
3981 else
3982 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3983 } else {
3984 // Both conditions must be false at the same time for the loop to exit.
3985 // For now, be conservative.
3986 assert(L->contains(TBB) && "Loop block has no successor in loop!");
3987 if (BTI0.Max == BTI1.Max)
3988 MaxBECount = BTI0.Max;
3989 if (BTI0.Exact == BTI1.Exact)
3990 BECount = BTI0.Exact;
3991 }
3992
3993 return BackedgeTakenInfo(BECount, MaxBECount);
3994 }
3995 }
3996
3997 // With an icmp, it may be feasible to compute an exact backedge-taken count.
3998 // Proceed to the next level to examine the icmp.
3999 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
4000 return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
4001
4002 // Check for a constant condition. These are normally stripped out by
4003 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
4004 // preserve the CFG and is temporarily leaving constant conditions
4005 // in place.
4006 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
4007 if (L->contains(FBB) == !CI->getZExtValue())
4008 // The backedge is always taken.
4009 return getCouldNotCompute();
4010 else
4011 // The backedge is never taken.
4012 return getConstant(CI->getType(), 0);
4013 }
4014
4015 // If it's not an integer or pointer comparison then compute it the hard way.
4016 return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4017 }
4018
4019 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of times the
4020 /// backedge of the specified loop will execute if its exit condition
4021 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4022 ScalarEvolution::BackedgeTakenInfo
ComputeBackedgeTakenCountFromExitCondICmp(const Loop * L,ICmpInst * ExitCond,BasicBlock * TBB,BasicBlock * FBB)4023 ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
4024 ICmpInst *ExitCond,
4025 BasicBlock *TBB,
4026 BasicBlock *FBB) {
4027
4028 // If the condition was exit on true, convert the condition to exit on false
4029 ICmpInst::Predicate Cond;
4030 if (!L->contains(FBB))
4031 Cond = ExitCond->getPredicate();
4032 else
4033 Cond = ExitCond->getInversePredicate();
4034
4035 // Handle common loops like: for (X = "string"; *X; ++X)
4036 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4037 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4038 BackedgeTakenInfo ItCnt =
4039 ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
4040 if (ItCnt.hasAnyInfo())
4041 return ItCnt;
4042 }
4043
4044 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4045 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4046
4047 // Try to evaluate any dependencies out of the loop.
4048 LHS = getSCEVAtScope(LHS, L);
4049 RHS = getSCEVAtScope(RHS, L);
4050
4051 // At this point, we would like to compute how many iterations of the
4052 // loop the predicate will return true for these inputs.
4053 if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) {
4054 // If there is a loop-invariant, force it into the RHS.
4055 std::swap(LHS, RHS);
4056 Cond = ICmpInst::getSwappedPredicate(Cond);
4057 }
4058
4059 // Simplify the operands before analyzing them.
4060 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4061
4062 // If we have a comparison of a chrec against a constant, try to use value
4063 // ranges to answer this query.
4064 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4065 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4066 if (AddRec->getLoop() == L) {
4067 // Form the constant range.
4068 ConstantRange CompRange(
4069 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4070
4071 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4072 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4073 }
4074
4075 switch (Cond) {
4076 case ICmpInst::ICMP_NE: { // while (X != Y)
4077 // Convert to: while (X-Y != 0)
4078 BackedgeTakenInfo BTI = HowFarToZero(getMinusSCEV(LHS, RHS), L);
4079 if (BTI.hasAnyInfo()) return BTI;
4080 break;
4081 }
4082 case ICmpInst::ICMP_EQ: { // while (X == Y)
4083 // Convert to: while (X-Y == 0)
4084 BackedgeTakenInfo BTI = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
4085 if (BTI.hasAnyInfo()) return BTI;
4086 break;
4087 }
4088 case ICmpInst::ICMP_SLT: {
4089 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, true);
4090 if (BTI.hasAnyInfo()) return BTI;
4091 break;
4092 }
4093 case ICmpInst::ICMP_SGT: {
4094 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4095 getNotSCEV(RHS), L, true);
4096 if (BTI.hasAnyInfo()) return BTI;
4097 break;
4098 }
4099 case ICmpInst::ICMP_ULT: {
4100 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, false);
4101 if (BTI.hasAnyInfo()) return BTI;
4102 break;
4103 }
4104 case ICmpInst::ICMP_UGT: {
4105 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4106 getNotSCEV(RHS), L, false);
4107 if (BTI.hasAnyInfo()) return BTI;
4108 break;
4109 }
4110 default:
4111 #if 0
4112 dbgs() << "ComputeBackedgeTakenCount ";
4113 if (ExitCond->getOperand(0)->getType()->isUnsigned())
4114 dbgs() << "[unsigned] ";
4115 dbgs() << *LHS << " "
4116 << Instruction::getOpcodeName(Instruction::ICmp)
4117 << " " << *RHS << "\n";
4118 #endif
4119 break;
4120 }
4121 return
4122 ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4123 }
4124
4125 static ConstantInt *
EvaluateConstantChrecAtConstant(const SCEVAddRecExpr * AddRec,ConstantInt * C,ScalarEvolution & SE)4126 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
4127 ScalarEvolution &SE) {
4128 const SCEV *InVal = SE.getConstant(C);
4129 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
4130 assert(isa<SCEVConstant>(Val) &&
4131 "Evaluation of SCEV at constant didn't fold correctly?");
4132 return cast<SCEVConstant>(Val)->getValue();
4133 }
4134
4135 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
4136 /// and a GEP expression (missing the pointer index) indexing into it, return
4137 /// the addressed element of the initializer or null if the index expression is
4138 /// invalid.
4139 static Constant *
GetAddressedElementFromGlobal(GlobalVariable * GV,const std::vector<ConstantInt * > & Indices)4140 GetAddressedElementFromGlobal(GlobalVariable *GV,
4141 const std::vector<ConstantInt*> &Indices) {
4142 Constant *Init = GV->getInitializer();
4143 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
4144 uint64_t Idx = Indices[i]->getZExtValue();
4145 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
4146 assert(Idx < CS->getNumOperands() && "Bad struct index!");
4147 Init = cast<Constant>(CS->getOperand(Idx));
4148 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
4149 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
4150 Init = cast<Constant>(CA->getOperand(Idx));
4151 } else if (isa<ConstantAggregateZero>(Init)) {
4152 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
4153 assert(Idx < STy->getNumElements() && "Bad struct index!");
4154 Init = Constant::getNullValue(STy->getElementType(Idx));
4155 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
4156 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4157 Init = Constant::getNullValue(ATy->getElementType());
4158 } else {
4159 llvm_unreachable("Unknown constant aggregate type!");
4160 }
4161 return 0;
4162 } else {
4163 return 0; // Unknown initializer type
4164 }
4165 }
4166 return Init;
4167 }
4168
4169 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
4170 /// 'icmp op load X, cst', try to see if we can compute the backedge
4171 /// execution count.
4172 ScalarEvolution::BackedgeTakenInfo
ComputeLoadConstantCompareBackedgeTakenCount(LoadInst * LI,Constant * RHS,const Loop * L,ICmpInst::Predicate predicate)4173 ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
4174 LoadInst *LI,
4175 Constant *RHS,
4176 const Loop *L,
4177 ICmpInst::Predicate predicate) {
4178 if (LI->isVolatile()) return getCouldNotCompute();
4179
4180 // Check to see if the loaded pointer is a getelementptr of a global.
4181 // TODO: Use SCEV instead of manually grubbing with GEPs.
4182 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4183 if (!GEP) return getCouldNotCompute();
4184
4185 // Make sure that it is really a constant global we are gepping, with an
4186 // initializer, and make sure the first IDX is really 0.
4187 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4188 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4189 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4190 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4191 return getCouldNotCompute();
4192
4193 // Okay, we allow one non-constant index into the GEP instruction.
4194 Value *VarIdx = 0;
4195 std::vector<ConstantInt*> Indexes;
4196 unsigned VarIdxNum = 0;
4197 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4198 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4199 Indexes.push_back(CI);
4200 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4201 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4202 VarIdx = GEP->getOperand(i);
4203 VarIdxNum = i-2;
4204 Indexes.push_back(0);
4205 }
4206
4207 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4208 // Check to see if X is a loop variant variable value now.
4209 const SCEV *Idx = getSCEV(VarIdx);
4210 Idx = getSCEVAtScope(Idx, L);
4211
4212 // We can only recognize very limited forms of loop index expressions, in
4213 // particular, only affine AddRec's like {C1,+,C2}.
4214 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4215 if (!IdxExpr || !IdxExpr->isAffine() || IdxExpr->isLoopInvariant(L) ||
4216 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4217 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4218 return getCouldNotCompute();
4219
4220 unsigned MaxSteps = MaxBruteForceIterations;
4221 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4222 ConstantInt *ItCst = ConstantInt::get(
4223 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4224 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4225
4226 // Form the GEP offset.
4227 Indexes[VarIdxNum] = Val;
4228
4229 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4230 if (Result == 0) break; // Cannot compute!
4231
4232 // Evaluate the condition for this iteration.
4233 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4234 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4235 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4236 #if 0
4237 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4238 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4239 << "***\n";
4240 #endif
4241 ++NumArrayLenItCounts;
4242 return getConstant(ItCst); // Found terminating iteration!
4243 }
4244 }
4245 return getCouldNotCompute();
4246 }
4247
4248
4249 /// CanConstantFold - Return true if we can constant fold an instruction of the
4250 /// specified type, assuming that all operands were constants.
CanConstantFold(const Instruction * I)4251 static bool CanConstantFold(const Instruction *I) {
4252 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4253 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
4254 return true;
4255
4256 if (const CallInst *CI = dyn_cast<CallInst>(I))
4257 if (const Function *F = CI->getCalledFunction())
4258 return canConstantFoldCallTo(F);
4259 return false;
4260 }
4261
4262 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4263 /// in the loop that V is derived from. We allow arbitrary operations along the
4264 /// way, but the operands of an operation must either be constants or a value
4265 /// derived from a constant PHI. If this expression does not fit with these
4266 /// constraints, return null.
getConstantEvolvingPHI(Value * V,const Loop * L)4267 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4268 // If this is not an instruction, or if this is an instruction outside of the
4269 // loop, it can't be derived from a loop PHI.
4270 Instruction *I = dyn_cast<Instruction>(V);
4271 if (I == 0 || !L->contains(I)) return 0;
4272
4273 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4274 if (L->getHeader() == I->getParent())
4275 return PN;
4276 else
4277 // We don't currently keep track of the control flow needed to evaluate
4278 // PHIs, so we cannot handle PHIs inside of loops.
4279 return 0;
4280 }
4281
4282 // If we won't be able to constant fold this expression even if the operands
4283 // are constants, return early.
4284 if (!CanConstantFold(I)) return 0;
4285
4286 // Otherwise, we can evaluate this instruction if all of its operands are
4287 // constant or derived from a PHI node themselves.
4288 PHINode *PHI = 0;
4289 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4290 if (!isa<Constant>(I->getOperand(Op))) {
4291 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4292 if (P == 0) return 0; // Not evolving from PHI
4293 if (PHI == 0)
4294 PHI = P;
4295 else if (PHI != P)
4296 return 0; // Evolving from multiple different PHIs.
4297 }
4298
4299 // This is a expression evolving from a constant PHI!
4300 return PHI;
4301 }
4302
4303 /// EvaluateExpression - Given an expression that passes the
4304 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4305 /// in the loop has the value PHIVal. If we can't fold this expression for some
4306 /// reason, return null.
EvaluateExpression(Value * V,Constant * PHIVal,const TargetData * TD)4307 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4308 const TargetData *TD) {
4309 if (isa<PHINode>(V)) return PHIVal;
4310 if (Constant *C = dyn_cast<Constant>(V)) return C;
4311 Instruction *I = cast<Instruction>(V);
4312
4313 std::vector<Constant*> Operands(I->getNumOperands());
4314
4315 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4316 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4317 if (Operands[i] == 0) return 0;
4318 }
4319
4320 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4321 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4322 Operands[1], TD);
4323 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4324 &Operands[0], Operands.size(), TD);
4325 }
4326
4327 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4328 /// in the header of its containing loop, we know the loop executes a
4329 /// constant number of times, and the PHI node is just a recurrence
4330 /// involving constants, fold it.
4331 Constant *
getConstantEvolutionLoopExitValue(PHINode * PN,const APInt & BEs,const Loop * L)4332 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4333 const APInt &BEs,
4334 const Loop *L) {
4335 std::map<PHINode*, Constant*>::const_iterator I =
4336 ConstantEvolutionLoopExitValue.find(PN);
4337 if (I != ConstantEvolutionLoopExitValue.end())
4338 return I->second;
4339
4340 if (BEs.ugt(MaxBruteForceIterations))
4341 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4342
4343 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4344
4345 // Since the loop is canonicalized, the PHI node must have two entries. One
4346 // entry must be a constant (coming in from outside of the loop), and the
4347 // second must be derived from the same PHI.
4348 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4349 Constant *StartCST =
4350 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4351 if (StartCST == 0)
4352 return RetVal = 0; // Must be a constant.
4353
4354 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4355 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4356 !isa<Constant>(BEValue))
4357 return RetVal = 0; // Not derived from same PHI.
4358
4359 // Execute the loop symbolically to determine the exit value.
4360 if (BEs.getActiveBits() >= 32)
4361 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4362
4363 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4364 unsigned IterationNum = 0;
4365 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4366 if (IterationNum == NumIterations)
4367 return RetVal = PHIVal; // Got exit value!
4368
4369 // Compute the value of the PHI node for the next iteration.
4370 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4371 if (NextPHI == PHIVal)
4372 return RetVal = NextPHI; // Stopped evolving!
4373 if (NextPHI == 0)
4374 return 0; // Couldn't evaluate!
4375 PHIVal = NextPHI;
4376 }
4377 }
4378
4379 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute a
4380 /// constant number of times (the condition evolves only from constants),
4381 /// try to evaluate a few iterations of the loop until we get the exit
4382 /// condition gets a value of ExitWhen (true or false). If we cannot
4383 /// evaluate the trip count of the loop, return getCouldNotCompute().
4384 const SCEV *
ComputeBackedgeTakenCountExhaustively(const Loop * L,Value * Cond,bool ExitWhen)4385 ScalarEvolution::ComputeBackedgeTakenCountExhaustively(const Loop *L,
4386 Value *Cond,
4387 bool ExitWhen) {
4388 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4389 if (PN == 0) return getCouldNotCompute();
4390
4391 // If the loop is canonicalized, the PHI will have exactly two entries.
4392 // That's the only form we support here.
4393 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4394
4395 // One entry must be a constant (coming in from outside of the loop), and the
4396 // second must be derived from the same PHI.
4397 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4398 Constant *StartCST =
4399 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4400 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4401
4402 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4403 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4404 !isa<Constant>(BEValue))
4405 return getCouldNotCompute(); // Not derived from same PHI.
4406
4407 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4408 // the loop symbolically to determine when the condition gets a value of
4409 // "ExitWhen".
4410 unsigned IterationNum = 0;
4411 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4412 for (Constant *PHIVal = StartCST;
4413 IterationNum != MaxIterations; ++IterationNum) {
4414 ConstantInt *CondVal =
4415 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4416
4417 // Couldn't symbolically evaluate.
4418 if (!CondVal) return getCouldNotCompute();
4419
4420 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4421 ++NumBruteForceTripCountsComputed;
4422 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4423 }
4424
4425 // Compute the value of the PHI node for the next iteration.
4426 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4427 if (NextPHI == 0 || NextPHI == PHIVal)
4428 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4429 PHIVal = NextPHI;
4430 }
4431
4432 // Too many iterations were needed to evaluate.
4433 return getCouldNotCompute();
4434 }
4435
4436 /// getSCEVAtScope - Return a SCEV expression for the specified value
4437 /// at the specified scope in the program. The L value specifies a loop
4438 /// nest to evaluate the expression at, where null is the top-level or a
4439 /// specified loop is immediately inside of the loop.
4440 ///
4441 /// This method can be used to compute the exit value for a variable defined
4442 /// in a loop by querying what the value will hold in the parent loop.
4443 ///
4444 /// In the case that a relevant loop exit value cannot be computed, the
4445 /// original value V is returned.
getSCEVAtScope(const SCEV * V,const Loop * L)4446 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4447 // Check to see if we've folded this expression at this loop before.
4448 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4449 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4450 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4451 if (!Pair.second)
4452 return Pair.first->second ? Pair.first->second : V;
4453
4454 // Otherwise compute it.
4455 const SCEV *C = computeSCEVAtScope(V, L);
4456 ValuesAtScopes[V][L] = C;
4457 return C;
4458 }
4459
computeSCEVAtScope(const SCEV * V,const Loop * L)4460 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4461 if (isa<SCEVConstant>(V)) return V;
4462
4463 // If this instruction is evolved from a constant-evolving PHI, compute the
4464 // exit value from the loop without using SCEVs.
4465 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4466 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4467 const Loop *LI = (*this->LI)[I->getParent()];
4468 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4469 if (PHINode *PN = dyn_cast<PHINode>(I))
4470 if (PN->getParent() == LI->getHeader()) {
4471 // Okay, there is no closed form solution for the PHI node. Check
4472 // to see if the loop that contains it has a known backedge-taken
4473 // count. If so, we may be able to force computation of the exit
4474 // value.
4475 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4476 if (const SCEVConstant *BTCC =
4477 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4478 // Okay, we know how many times the containing loop executes. If
4479 // this is a constant evolving PHI node, get the final value at
4480 // the specified iteration number.
4481 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4482 BTCC->getValue()->getValue(),
4483 LI);
4484 if (RV) return getSCEV(RV);
4485 }
4486 }
4487
4488 // Okay, this is an expression that we cannot symbolically evaluate
4489 // into a SCEV. Check to see if it's possible to symbolically evaluate
4490 // the arguments into constants, and if so, try to constant propagate the
4491 // result. This is particularly useful for computing loop exit values.
4492 if (CanConstantFold(I)) {
4493 SmallVector<Constant *, 4> Operands;
4494 bool MadeImprovement = false;
4495 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4496 Value *Op = I->getOperand(i);
4497 if (Constant *C = dyn_cast<Constant>(Op)) {
4498 Operands.push_back(C);
4499 continue;
4500 }
4501
4502 // If any of the operands is non-constant and if they are
4503 // non-integer and non-pointer, don't even try to analyze them
4504 // with scev techniques.
4505 if (!isSCEVable(Op->getType()))
4506 return V;
4507
4508 const SCEV *OrigV = getSCEV(Op);
4509 const SCEV *OpV = getSCEVAtScope(OrigV, L);
4510 MadeImprovement |= OrigV != OpV;
4511
4512 Constant *C = 0;
4513 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
4514 C = SC->getValue();
4515 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
4516 C = dyn_cast<Constant>(SU->getValue());
4517 if (!C) return V;
4518 if (C->getType() != Op->getType())
4519 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4520 Op->getType(),
4521 false),
4522 C, Op->getType());
4523 Operands.push_back(C);
4524 }
4525
4526 // Check to see if getSCEVAtScope actually made an improvement.
4527 if (MadeImprovement) {
4528 Constant *C = 0;
4529 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4530 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4531 Operands[0], Operands[1], TD);
4532 else
4533 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4534 &Operands[0], Operands.size(), TD);
4535 if (!C) return V;
4536 return getSCEV(C);
4537 }
4538 }
4539 }
4540
4541 // This is some other type of SCEVUnknown, just return it.
4542 return V;
4543 }
4544
4545 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4546 // Avoid performing the look-up in the common case where the specified
4547 // expression has no loop-variant portions.
4548 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4549 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4550 if (OpAtScope != Comm->getOperand(i)) {
4551 // Okay, at least one of these operands is loop variant but might be
4552 // foldable. Build a new instance of the folded commutative expression.
4553 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4554 Comm->op_begin()+i);
4555 NewOps.push_back(OpAtScope);
4556
4557 for (++i; i != e; ++i) {
4558 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4559 NewOps.push_back(OpAtScope);
4560 }
4561 if (isa<SCEVAddExpr>(Comm))
4562 return getAddExpr(NewOps);
4563 if (isa<SCEVMulExpr>(Comm))
4564 return getMulExpr(NewOps);
4565 if (isa<SCEVSMaxExpr>(Comm))
4566 return getSMaxExpr(NewOps);
4567 if (isa<SCEVUMaxExpr>(Comm))
4568 return getUMaxExpr(NewOps);
4569 llvm_unreachable("Unknown commutative SCEV type!");
4570 }
4571 }
4572 // If we got here, all operands are loop invariant.
4573 return Comm;
4574 }
4575
4576 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4577 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4578 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4579 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4580 return Div; // must be loop invariant
4581 return getUDivExpr(LHS, RHS);
4582 }
4583
4584 // If this is a loop recurrence for a loop that does not contain L, then we
4585 // are dealing with the final value computed by the loop.
4586 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4587 // First, attempt to evaluate each operand.
4588 // Avoid performing the look-up in the common case where the specified
4589 // expression has no loop-variant portions.
4590 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4591 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
4592 if (OpAtScope == AddRec->getOperand(i))
4593 continue;
4594
4595 // Okay, at least one of these operands is loop variant but might be
4596 // foldable. Build a new instance of the folded commutative expression.
4597 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
4598 AddRec->op_begin()+i);
4599 NewOps.push_back(OpAtScope);
4600 for (++i; i != e; ++i)
4601 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
4602
4603 AddRec = cast<SCEVAddRecExpr>(getAddRecExpr(NewOps, AddRec->getLoop()));
4604 break;
4605 }
4606
4607 // If the scope is outside the addrec's loop, evaluate it by using the
4608 // loop exit value of the addrec.
4609 if (!AddRec->getLoop()->contains(L)) {
4610 // To evaluate this recurrence, we need to know how many times the AddRec
4611 // loop iterates. Compute this now.
4612 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4613 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4614
4615 // Then, evaluate the AddRec.
4616 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4617 }
4618
4619 return AddRec;
4620 }
4621
4622 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4623 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4624 if (Op == Cast->getOperand())
4625 return Cast; // must be loop invariant
4626 return getZeroExtendExpr(Op, Cast->getType());
4627 }
4628
4629 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4630 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4631 if (Op == Cast->getOperand())
4632 return Cast; // must be loop invariant
4633 return getSignExtendExpr(Op, Cast->getType());
4634 }
4635
4636 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4637 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4638 if (Op == Cast->getOperand())
4639 return Cast; // must be loop invariant
4640 return getTruncateExpr(Op, Cast->getType());
4641 }
4642
4643 llvm_unreachable("Unknown SCEV type!");
4644 return 0;
4645 }
4646
4647 /// getSCEVAtScope - This is a convenience function which does
4648 /// getSCEVAtScope(getSCEV(V), L).
getSCEVAtScope(Value * V,const Loop * L)4649 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4650 return getSCEVAtScope(getSCEV(V), L);
4651 }
4652
4653 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4654 /// following equation:
4655 ///
4656 /// A * X = B (mod N)
4657 ///
4658 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4659 /// A and B isn't important.
4660 ///
4661 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
SolveLinEquationWithOverflow(const APInt & A,const APInt & B,ScalarEvolution & SE)4662 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4663 ScalarEvolution &SE) {
4664 uint32_t BW = A.getBitWidth();
4665 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4666 assert(A != 0 && "A must be non-zero.");
4667
4668 // 1. D = gcd(A, N)
4669 //
4670 // The gcd of A and N may have only one prime factor: 2. The number of
4671 // trailing zeros in A is its multiplicity
4672 uint32_t Mult2 = A.countTrailingZeros();
4673 // D = 2^Mult2
4674
4675 // 2. Check if B is divisible by D.
4676 //
4677 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4678 // is not less than multiplicity of this prime factor for D.
4679 if (B.countTrailingZeros() < Mult2)
4680 return SE.getCouldNotCompute();
4681
4682 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4683 // modulo (N / D).
4684 //
4685 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4686 // bit width during computations.
4687 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4688 APInt Mod(BW + 1, 0);
4689 Mod.set(BW - Mult2); // Mod = N / D
4690 APInt I = AD.multiplicativeInverse(Mod);
4691
4692 // 4. Compute the minimum unsigned root of the equation:
4693 // I * (B / D) mod (N / D)
4694 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4695
4696 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4697 // bits.
4698 return SE.getConstant(Result.trunc(BW));
4699 }
4700
4701 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4702 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4703 /// might be the same) or two SCEVCouldNotCompute objects.
4704 ///
4705 static std::pair<const SCEV *,const SCEV *>
SolveQuadraticEquation(const SCEVAddRecExpr * AddRec,ScalarEvolution & SE)4706 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4707 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4708 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4709 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4710 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4711
4712 // We currently can only solve this if the coefficients are constants.
4713 if (!LC || !MC || !NC) {
4714 const SCEV *CNC = SE.getCouldNotCompute();
4715 return std::make_pair(CNC, CNC);
4716 }
4717
4718 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4719 const APInt &L = LC->getValue()->getValue();
4720 const APInt &M = MC->getValue()->getValue();
4721 const APInt &N = NC->getValue()->getValue();
4722 APInt Two(BitWidth, 2);
4723 APInt Four(BitWidth, 4);
4724
4725 {
4726 using namespace APIntOps;
4727 const APInt& C = L;
4728 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4729 // The B coefficient is M-N/2
4730 APInt B(M);
4731 B -= sdiv(N,Two);
4732
4733 // The A coefficient is N/2
4734 APInt A(N.sdiv(Two));
4735
4736 // Compute the B^2-4ac term.
4737 APInt SqrtTerm(B);
4738 SqrtTerm *= B;
4739 SqrtTerm -= Four * (A * C);
4740
4741 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4742 // integer value or else APInt::sqrt() will assert.
4743 APInt SqrtVal(SqrtTerm.sqrt());
4744
4745 // Compute the two solutions for the quadratic formula.
4746 // The divisions must be performed as signed divisions.
4747 APInt NegB(-B);
4748 APInt TwoA( A << 1 );
4749 if (TwoA.isMinValue()) {
4750 const SCEV *CNC = SE.getCouldNotCompute();
4751 return std::make_pair(CNC, CNC);
4752 }
4753
4754 LLVMContext &Context = SE.getContext();
4755
4756 ConstantInt *Solution1 =
4757 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
4758 ConstantInt *Solution2 =
4759 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
4760
4761 return std::make_pair(SE.getConstant(Solution1),
4762 SE.getConstant(Solution2));
4763 } // end APIntOps namespace
4764 }
4765
4766 /// HowFarToZero - Return the number of times a backedge comparing the specified
4767 /// value to zero will execute. If not computable, return CouldNotCompute.
4768 ScalarEvolution::BackedgeTakenInfo
HowFarToZero(const SCEV * V,const Loop * L)4769 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
4770 // If the value is a constant
4771 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4772 // If the value is already zero, the branch will execute zero times.
4773 if (C->getValue()->isZero()) return C;
4774 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4775 }
4776
4777 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
4778 if (!AddRec || AddRec->getLoop() != L)
4779 return getCouldNotCompute();
4780
4781 if (AddRec->isAffine()) {
4782 // If this is an affine expression, the execution count of this branch is
4783 // the minimum unsigned root of the following equation:
4784 //
4785 // Start + Step*N = 0 (mod 2^BW)
4786 //
4787 // equivalent to:
4788 //
4789 // Step*N = -Start (mod 2^BW)
4790 //
4791 // where BW is the common bit width of Start and Step.
4792
4793 // Get the initial value for the loop.
4794 const SCEV *Start = getSCEVAtScope(AddRec->getStart(),
4795 L->getParentLoop());
4796 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1),
4797 L->getParentLoop());
4798
4799 if (const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step)) {
4800 // For now we handle only constant steps.
4801
4802 // First, handle unitary steps.
4803 if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
4804 return getNegativeSCEV(Start); // N = -Start (as unsigned)
4805 if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
4806 return Start; // N = Start (as unsigned)
4807
4808 // Then, try to solve the above equation provided that Start is constant.
4809 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
4810 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
4811 -StartC->getValue()->getValue(),
4812 *this);
4813 }
4814 } else if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
4815 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
4816 // the quadratic equation to solve it.
4817 std::pair<const SCEV *,const SCEV *> Roots = SolveQuadraticEquation(AddRec,
4818 *this);
4819 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
4820 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
4821 if (R1) {
4822 #if 0
4823 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
4824 << " sol#2: " << *R2 << "\n";
4825 #endif
4826 // Pick the smallest positive root value.
4827 if (ConstantInt *CB =
4828 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
4829 R1->getValue(), R2->getValue()))) {
4830 if (CB->getZExtValue() == false)
4831 std::swap(R1, R2); // R1 is the minimum root now.
4832
4833 // We can only use this value if the chrec ends up with an exact zero
4834 // value at this index. When solving for "X*X != 5", for example, we
4835 // should not accept a root of 2.
4836 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
4837 if (Val->isZero())
4838 return R1; // We found a quadratic root!
4839 }
4840 }
4841 }
4842
4843 return getCouldNotCompute();
4844 }
4845
4846 /// HowFarToNonZero - Return the number of times a backedge checking the
4847 /// specified value for nonzero will execute. If not computable, return
4848 /// CouldNotCompute
4849 ScalarEvolution::BackedgeTakenInfo
HowFarToNonZero(const SCEV * V,const Loop * L)4850 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
4851 // Loops that look like: while (X == 0) are very strange indeed. We don't
4852 // handle them yet except for the trivial case. This could be expanded in the
4853 // future as needed.
4854
4855 // If the value is a constant, check to see if it is known to be non-zero
4856 // already. If so, the backedge will execute zero times.
4857 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4858 if (!C->getValue()->isNullValue())
4859 return getConstant(C->getType(), 0);
4860 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4861 }
4862
4863 // We could implement others, but I really doubt anyone writes loops like
4864 // this, and if they did, they would already be constant folded.
4865 return getCouldNotCompute();
4866 }
4867
4868 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
4869 /// (which may not be an immediate predecessor) which has exactly one
4870 /// successor from which BB is reachable, or null if no such block is
4871 /// found.
4872 ///
4873 std::pair<BasicBlock *, BasicBlock *>
getPredecessorWithUniqueSuccessorForBB(BasicBlock * BB)4874 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
4875 // If the block has a unique predecessor, then there is no path from the
4876 // predecessor to the block that does not go through the direct edge
4877 // from the predecessor to the block.
4878 if (BasicBlock *Pred = BB->getSinglePredecessor())
4879 return std::make_pair(Pred, BB);
4880
4881 // A loop's header is defined to be a block that dominates the loop.
4882 // If the header has a unique predecessor outside the loop, it must be
4883 // a block that has exactly one successor that can reach the loop.
4884 if (Loop *L = LI->getLoopFor(BB))
4885 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
4886
4887 return std::pair<BasicBlock *, BasicBlock *>();
4888 }
4889
4890 /// HasSameValue - SCEV structural equivalence is usually sufficient for
4891 /// testing whether two expressions are equal, however for the purposes of
4892 /// looking for a condition guarding a loop, it can be useful to be a little
4893 /// more general, since a front-end may have replicated the controlling
4894 /// expression.
4895 ///
HasSameValue(const SCEV * A,const SCEV * B)4896 static bool HasSameValue(const SCEV *A, const SCEV *B) {
4897 // Quick check to see if they are the same SCEV.
4898 if (A == B) return true;
4899
4900 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
4901 // two different instructions with the same value. Check for this case.
4902 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
4903 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
4904 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
4905 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
4906 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
4907 return true;
4908
4909 // Otherwise assume they may have a different value.
4910 return false;
4911 }
4912
4913 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
4914 /// predicate Pred. Return true iff any changes were made.
4915 ///
SimplifyICmpOperands(ICmpInst::Predicate & Pred,const SCEV * & LHS,const SCEV * & RHS)4916 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
4917 const SCEV *&LHS, const SCEV *&RHS) {
4918 bool Changed = false;
4919
4920 // Canonicalize a constant to the right side.
4921 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
4922 // Check for both operands constant.
4923 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
4924 if (ConstantExpr::getICmp(Pred,
4925 LHSC->getValue(),
4926 RHSC->getValue())->isNullValue())
4927 goto trivially_false;
4928 else
4929 goto trivially_true;
4930 }
4931 // Otherwise swap the operands to put the constant on the right.
4932 std::swap(LHS, RHS);
4933 Pred = ICmpInst::getSwappedPredicate(Pred);
4934 Changed = true;
4935 }
4936
4937 // If we're comparing an addrec with a value which is loop-invariant in the
4938 // addrec's loop, put the addrec on the left. Also make a dominance check,
4939 // as both operands could be addrecs loop-invariant in each other's loop.
4940 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
4941 const Loop *L = AR->getLoop();
4942 if (LHS->isLoopInvariant(L) && LHS->properlyDominates(L->getHeader(), DT)) {
4943 std::swap(LHS, RHS);
4944 Pred = ICmpInst::getSwappedPredicate(Pred);
4945 Changed = true;
4946 }
4947 }
4948
4949 // If there's a constant operand, canonicalize comparisons with boundary
4950 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
4951 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
4952 const APInt &RA = RC->getValue()->getValue();
4953 switch (Pred) {
4954 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
4955 case ICmpInst::ICMP_EQ:
4956 case ICmpInst::ICMP_NE:
4957 break;
4958 case ICmpInst::ICMP_UGE:
4959 if ((RA - 1).isMinValue()) {
4960 Pred = ICmpInst::ICMP_NE;
4961 RHS = getConstant(RA - 1);
4962 Changed = true;
4963 break;
4964 }
4965 if (RA.isMaxValue()) {
4966 Pred = ICmpInst::ICMP_EQ;
4967 Changed = true;
4968 break;
4969 }
4970 if (RA.isMinValue()) goto trivially_true;
4971
4972 Pred = ICmpInst::ICMP_UGT;
4973 RHS = getConstant(RA - 1);
4974 Changed = true;
4975 break;
4976 case ICmpInst::ICMP_ULE:
4977 if ((RA + 1).isMaxValue()) {
4978 Pred = ICmpInst::ICMP_NE;
4979 RHS = getConstant(RA + 1);
4980 Changed = true;
4981 break;
4982 }
4983 if (RA.isMinValue()) {
4984 Pred = ICmpInst::ICMP_EQ;
4985 Changed = true;
4986 break;
4987 }
4988 if (RA.isMaxValue()) goto trivially_true;
4989
4990 Pred = ICmpInst::ICMP_ULT;
4991 RHS = getConstant(RA + 1);
4992 Changed = true;
4993 break;
4994 case ICmpInst::ICMP_SGE:
4995 if ((RA - 1).isMinSignedValue()) {
4996 Pred = ICmpInst::ICMP_NE;
4997 RHS = getConstant(RA - 1);
4998 Changed = true;
4999 break;
5000 }
5001 if (RA.isMaxSignedValue()) {
5002 Pred = ICmpInst::ICMP_EQ;
5003 Changed = true;
5004 break;
5005 }
5006 if (RA.isMinSignedValue()) goto trivially_true;
5007
5008 Pred = ICmpInst::ICMP_SGT;
5009 RHS = getConstant(RA - 1);
5010 Changed = true;
5011 break;
5012 case ICmpInst::ICMP_SLE:
5013 if ((RA + 1).isMaxSignedValue()) {
5014 Pred = ICmpInst::ICMP_NE;
5015 RHS = getConstant(RA + 1);
5016 Changed = true;
5017 break;
5018 }
5019 if (RA.isMinSignedValue()) {
5020 Pred = ICmpInst::ICMP_EQ;
5021 Changed = true;
5022 break;
5023 }
5024 if (RA.isMaxSignedValue()) goto trivially_true;
5025
5026 Pred = ICmpInst::ICMP_SLT;
5027 RHS = getConstant(RA + 1);
5028 Changed = true;
5029 break;
5030 case ICmpInst::ICMP_UGT:
5031 if (RA.isMinValue()) {
5032 Pred = ICmpInst::ICMP_NE;
5033 Changed = true;
5034 break;
5035 }
5036 if ((RA + 1).isMaxValue()) {
5037 Pred = ICmpInst::ICMP_EQ;
5038 RHS = getConstant(RA + 1);
5039 Changed = true;
5040 break;
5041 }
5042 if (RA.isMaxValue()) goto trivially_false;
5043 break;
5044 case ICmpInst::ICMP_ULT:
5045 if (RA.isMaxValue()) {
5046 Pred = ICmpInst::ICMP_NE;
5047 Changed = true;
5048 break;
5049 }
5050 if ((RA - 1).isMinValue()) {
5051 Pred = ICmpInst::ICMP_EQ;
5052 RHS = getConstant(RA - 1);
5053 Changed = true;
5054 break;
5055 }
5056 if (RA.isMinValue()) goto trivially_false;
5057 break;
5058 case ICmpInst::ICMP_SGT:
5059 if (RA.isMinSignedValue()) {
5060 Pred = ICmpInst::ICMP_NE;
5061 Changed = true;
5062 break;
5063 }
5064 if ((RA + 1).isMaxSignedValue()) {
5065 Pred = ICmpInst::ICMP_EQ;
5066 RHS = getConstant(RA + 1);
5067 Changed = true;
5068 break;
5069 }
5070 if (RA.isMaxSignedValue()) goto trivially_false;
5071 break;
5072 case ICmpInst::ICMP_SLT:
5073 if (RA.isMaxSignedValue()) {
5074 Pred = ICmpInst::ICMP_NE;
5075 Changed = true;
5076 break;
5077 }
5078 if ((RA - 1).isMinSignedValue()) {
5079 Pred = ICmpInst::ICMP_EQ;
5080 RHS = getConstant(RA - 1);
5081 Changed = true;
5082 break;
5083 }
5084 if (RA.isMinSignedValue()) goto trivially_false;
5085 break;
5086 }
5087 }
5088
5089 // Check for obvious equality.
5090 if (HasSameValue(LHS, RHS)) {
5091 if (ICmpInst::isTrueWhenEqual(Pred))
5092 goto trivially_true;
5093 if (ICmpInst::isFalseWhenEqual(Pred))
5094 goto trivially_false;
5095 }
5096
5097 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
5098 // adding or subtracting 1 from one of the operands.
5099 switch (Pred) {
5100 case ICmpInst::ICMP_SLE:
5101 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
5102 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5103 /*HasNUW=*/false, /*HasNSW=*/true);
5104 Pred = ICmpInst::ICMP_SLT;
5105 Changed = true;
5106 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
5107 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5108 /*HasNUW=*/false, /*HasNSW=*/true);
5109 Pred = ICmpInst::ICMP_SLT;
5110 Changed = true;
5111 }
5112 break;
5113 case ICmpInst::ICMP_SGE:
5114 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
5115 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5116 /*HasNUW=*/false, /*HasNSW=*/true);
5117 Pred = ICmpInst::ICMP_SGT;
5118 Changed = true;
5119 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
5120 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5121 /*HasNUW=*/false, /*HasNSW=*/true);
5122 Pred = ICmpInst::ICMP_SGT;
5123 Changed = true;
5124 }
5125 break;
5126 case ICmpInst::ICMP_ULE:
5127 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
5128 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5129 /*HasNUW=*/true, /*HasNSW=*/false);
5130 Pred = ICmpInst::ICMP_ULT;
5131 Changed = true;
5132 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
5133 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5134 /*HasNUW=*/true, /*HasNSW=*/false);
5135 Pred = ICmpInst::ICMP_ULT;
5136 Changed = true;
5137 }
5138 break;
5139 case ICmpInst::ICMP_UGE:
5140 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
5141 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5142 /*HasNUW=*/true, /*HasNSW=*/false);
5143 Pred = ICmpInst::ICMP_UGT;
5144 Changed = true;
5145 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
5146 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5147 /*HasNUW=*/true, /*HasNSW=*/false);
5148 Pred = ICmpInst::ICMP_UGT;
5149 Changed = true;
5150 }
5151 break;
5152 default:
5153 break;
5154 }
5155
5156 // TODO: More simplifications are possible here.
5157
5158 return Changed;
5159
5160 trivially_true:
5161 // Return 0 == 0.
5162 LHS = RHS = getConstant(Type::getInt1Ty(getContext()), 0);
5163 Pred = ICmpInst::ICMP_EQ;
5164 return true;
5165
5166 trivially_false:
5167 // Return 0 != 0.
5168 LHS = RHS = getConstant(Type::getInt1Ty(getContext()), 0);
5169 Pred = ICmpInst::ICMP_NE;
5170 return true;
5171 }
5172
isKnownNegative(const SCEV * S)5173 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
5174 return getSignedRange(S).getSignedMax().isNegative();
5175 }
5176
isKnownPositive(const SCEV * S)5177 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5178 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5179 }
5180
isKnownNonNegative(const SCEV * S)5181 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5182 return !getSignedRange(S).getSignedMin().isNegative();
5183 }
5184
isKnownNonPositive(const SCEV * S)5185 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5186 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5187 }
5188
isKnownNonZero(const SCEV * S)5189 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5190 return isKnownNegative(S) || isKnownPositive(S);
5191 }
5192
isKnownPredicate(ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS)5193 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5194 const SCEV *LHS, const SCEV *RHS) {
5195 // Canonicalize the inputs first.
5196 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5197
5198 // If LHS or RHS is an addrec, check to see if the condition is true in
5199 // every iteration of the loop.
5200 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5201 if (isLoopEntryGuardedByCond(
5202 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5203 isLoopBackedgeGuardedByCond(
5204 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5205 return true;
5206 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5207 if (isLoopEntryGuardedByCond(
5208 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5209 isLoopBackedgeGuardedByCond(
5210 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5211 return true;
5212
5213 // Otherwise see what can be done with known constant ranges.
5214 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5215 }
5216
5217 bool
isKnownPredicateWithRanges(ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS)5218 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5219 const SCEV *LHS, const SCEV *RHS) {
5220 if (HasSameValue(LHS, RHS))
5221 return ICmpInst::isTrueWhenEqual(Pred);
5222
5223 // This code is split out from isKnownPredicate because it is called from
5224 // within isLoopEntryGuardedByCond.
5225 switch (Pred) {
5226 default:
5227 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5228 break;
5229 case ICmpInst::ICMP_SGT:
5230 Pred = ICmpInst::ICMP_SLT;
5231 std::swap(LHS, RHS);
5232 case ICmpInst::ICMP_SLT: {
5233 ConstantRange LHSRange = getSignedRange(LHS);
5234 ConstantRange RHSRange = getSignedRange(RHS);
5235 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5236 return true;
5237 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5238 return false;
5239 break;
5240 }
5241 case ICmpInst::ICMP_SGE:
5242 Pred = ICmpInst::ICMP_SLE;
5243 std::swap(LHS, RHS);
5244 case ICmpInst::ICMP_SLE: {
5245 ConstantRange LHSRange = getSignedRange(LHS);
5246 ConstantRange RHSRange = getSignedRange(RHS);
5247 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5248 return true;
5249 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5250 return false;
5251 break;
5252 }
5253 case ICmpInst::ICMP_UGT:
5254 Pred = ICmpInst::ICMP_ULT;
5255 std::swap(LHS, RHS);
5256 case ICmpInst::ICMP_ULT: {
5257 ConstantRange LHSRange = getUnsignedRange(LHS);
5258 ConstantRange RHSRange = getUnsignedRange(RHS);
5259 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5260 return true;
5261 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5262 return false;
5263 break;
5264 }
5265 case ICmpInst::ICMP_UGE:
5266 Pred = ICmpInst::ICMP_ULE;
5267 std::swap(LHS, RHS);
5268 case ICmpInst::ICMP_ULE: {
5269 ConstantRange LHSRange = getUnsignedRange(LHS);
5270 ConstantRange RHSRange = getUnsignedRange(RHS);
5271 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5272 return true;
5273 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5274 return false;
5275 break;
5276 }
5277 case ICmpInst::ICMP_NE: {
5278 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5279 return true;
5280 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5281 return true;
5282
5283 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5284 if (isKnownNonZero(Diff))
5285 return true;
5286 break;
5287 }
5288 case ICmpInst::ICMP_EQ:
5289 // The check at the top of the function catches the case where
5290 // the values are known to be equal.
5291 break;
5292 }
5293 return false;
5294 }
5295
5296 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5297 /// protected by a conditional between LHS and RHS. This is used to
5298 /// to eliminate casts.
5299 bool
isLoopBackedgeGuardedByCond(const Loop * L,ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS)5300 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5301 ICmpInst::Predicate Pred,
5302 const SCEV *LHS, const SCEV *RHS) {
5303 // Interpret a null as meaning no loop, where there is obviously no guard
5304 // (interprocedural conditions notwithstanding).
5305 if (!L) return true;
5306
5307 BasicBlock *Latch = L->getLoopLatch();
5308 if (!Latch)
5309 return false;
5310
5311 BranchInst *LoopContinuePredicate =
5312 dyn_cast<BranchInst>(Latch->getTerminator());
5313 if (!LoopContinuePredicate ||
5314 LoopContinuePredicate->isUnconditional())
5315 return false;
5316
5317 return isImpliedCond(Pred, LHS, RHS,
5318 LoopContinuePredicate->getCondition(),
5319 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
5320 }
5321
5322 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
5323 /// by a conditional between LHS and RHS. This is used to help avoid max
5324 /// expressions in loop trip counts, and to eliminate casts.
5325 bool
isLoopEntryGuardedByCond(const Loop * L,ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS)5326 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
5327 ICmpInst::Predicate Pred,
5328 const SCEV *LHS, const SCEV *RHS) {
5329 // Interpret a null as meaning no loop, where there is obviously no guard
5330 // (interprocedural conditions notwithstanding).
5331 if (!L) return false;
5332
5333 // Starting at the loop predecessor, climb up the predecessor chain, as long
5334 // as there are predecessors that can be found that have unique successors
5335 // leading to the original header.
5336 for (std::pair<BasicBlock *, BasicBlock *>
5337 Pair(L->getLoopPredecessor(), L->getHeader());
5338 Pair.first;
5339 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
5340
5341 BranchInst *LoopEntryPredicate =
5342 dyn_cast<BranchInst>(Pair.first->getTerminator());
5343 if (!LoopEntryPredicate ||
5344 LoopEntryPredicate->isUnconditional())
5345 continue;
5346
5347 if (isImpliedCond(Pred, LHS, RHS,
5348 LoopEntryPredicate->getCondition(),
5349 LoopEntryPredicate->getSuccessor(0) != Pair.second))
5350 return true;
5351 }
5352
5353 return false;
5354 }
5355
5356 /// isImpliedCond - Test whether the condition described by Pred, LHS,
5357 /// and RHS is true whenever the given Cond value evaluates to true.
isImpliedCond(ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS,Value * FoundCondValue,bool Inverse)5358 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
5359 const SCEV *LHS, const SCEV *RHS,
5360 Value *FoundCondValue,
5361 bool Inverse) {
5362 // Recursively handle And and Or conditions.
5363 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
5364 if (BO->getOpcode() == Instruction::And) {
5365 if (!Inverse)
5366 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5367 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5368 } else if (BO->getOpcode() == Instruction::Or) {
5369 if (Inverse)
5370 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5371 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5372 }
5373 }
5374
5375 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
5376 if (!ICI) return false;
5377
5378 // Bail if the ICmp's operands' types are wider than the needed type
5379 // before attempting to call getSCEV on them. This avoids infinite
5380 // recursion, since the analysis of widening casts can require loop
5381 // exit condition information for overflow checking, which would
5382 // lead back here.
5383 if (getTypeSizeInBits(LHS->getType()) <
5384 getTypeSizeInBits(ICI->getOperand(0)->getType()))
5385 return false;
5386
5387 // Now that we found a conditional branch that dominates the loop, check to
5388 // see if it is the comparison we are looking for.
5389 ICmpInst::Predicate FoundPred;
5390 if (Inverse)
5391 FoundPred = ICI->getInversePredicate();
5392 else
5393 FoundPred = ICI->getPredicate();
5394
5395 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
5396 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
5397
5398 // Balance the types. The case where FoundLHS' type is wider than
5399 // LHS' type is checked for above.
5400 if (getTypeSizeInBits(LHS->getType()) >
5401 getTypeSizeInBits(FoundLHS->getType())) {
5402 if (CmpInst::isSigned(Pred)) {
5403 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
5404 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
5405 } else {
5406 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
5407 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
5408 }
5409 }
5410
5411 // Canonicalize the query to match the way instcombine will have
5412 // canonicalized the comparison.
5413 if (SimplifyICmpOperands(Pred, LHS, RHS))
5414 if (LHS == RHS)
5415 return CmpInst::isTrueWhenEqual(Pred);
5416 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
5417 if (FoundLHS == FoundRHS)
5418 return CmpInst::isFalseWhenEqual(Pred);
5419
5420 // Check to see if we can make the LHS or RHS match.
5421 if (LHS == FoundRHS || RHS == FoundLHS) {
5422 if (isa<SCEVConstant>(RHS)) {
5423 std::swap(FoundLHS, FoundRHS);
5424 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
5425 } else {
5426 std::swap(LHS, RHS);
5427 Pred = ICmpInst::getSwappedPredicate(Pred);
5428 }
5429 }
5430
5431 // Check whether the found predicate is the same as the desired predicate.
5432 if (FoundPred == Pred)
5433 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
5434
5435 // Check whether swapping the found predicate makes it the same as the
5436 // desired predicate.
5437 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
5438 if (isa<SCEVConstant>(RHS))
5439 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
5440 else
5441 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
5442 RHS, LHS, FoundLHS, FoundRHS);
5443 }
5444
5445 // Check whether the actual condition is beyond sufficient.
5446 if (FoundPred == ICmpInst::ICMP_EQ)
5447 if (ICmpInst::isTrueWhenEqual(Pred))
5448 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
5449 return true;
5450 if (Pred == ICmpInst::ICMP_NE)
5451 if (!ICmpInst::isTrueWhenEqual(FoundPred))
5452 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
5453 return true;
5454
5455 // Otherwise assume the worst.
5456 return false;
5457 }
5458
5459 /// isImpliedCondOperands - Test whether the condition described by Pred,
5460 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
5461 /// and FoundRHS is true.
isImpliedCondOperands(ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS,const SCEV * FoundLHS,const SCEV * FoundRHS)5462 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
5463 const SCEV *LHS, const SCEV *RHS,
5464 const SCEV *FoundLHS,
5465 const SCEV *FoundRHS) {
5466 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
5467 FoundLHS, FoundRHS) ||
5468 // ~x < ~y --> x > y
5469 isImpliedCondOperandsHelper(Pred, LHS, RHS,
5470 getNotSCEV(FoundRHS),
5471 getNotSCEV(FoundLHS));
5472 }
5473
5474 /// isImpliedCondOperandsHelper - Test whether the condition described by
5475 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
5476 /// FoundLHS, and FoundRHS is true.
5477 bool
isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,const SCEV * LHS,const SCEV * RHS,const SCEV * FoundLHS,const SCEV * FoundRHS)5478 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
5479 const SCEV *LHS, const SCEV *RHS,
5480 const SCEV *FoundLHS,
5481 const SCEV *FoundRHS) {
5482 switch (Pred) {
5483 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5484 case ICmpInst::ICMP_EQ:
5485 case ICmpInst::ICMP_NE:
5486 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5487 return true;
5488 break;
5489 case ICmpInst::ICMP_SLT:
5490 case ICmpInst::ICMP_SLE:
5491 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5492 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5493 return true;
5494 break;
5495 case ICmpInst::ICMP_SGT:
5496 case ICmpInst::ICMP_SGE:
5497 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5498 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5499 return true;
5500 break;
5501 case ICmpInst::ICMP_ULT:
5502 case ICmpInst::ICMP_ULE:
5503 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5504 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5505 return true;
5506 break;
5507 case ICmpInst::ICMP_UGT:
5508 case ICmpInst::ICMP_UGE:
5509 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5510 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5511 return true;
5512 break;
5513 }
5514
5515 return false;
5516 }
5517
5518 /// getBECount - Subtract the end and start values and divide by the step,
5519 /// rounding up, to get the number of times the backedge is executed. Return
5520 /// CouldNotCompute if an intermediate computation overflows.
getBECount(const SCEV * Start,const SCEV * End,const SCEV * Step,bool NoWrap)5521 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5522 const SCEV *End,
5523 const SCEV *Step,
5524 bool NoWrap) {
5525 assert(!isKnownNegative(Step) &&
5526 "This code doesn't handle negative strides yet!");
5527
5528 const Type *Ty = Start->getType();
5529 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
5530 const SCEV *Diff = getMinusSCEV(End, Start);
5531 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5532
5533 // Add an adjustment to the difference between End and Start so that
5534 // the division will effectively round up.
5535 const SCEV *Add = getAddExpr(Diff, RoundUp);
5536
5537 if (!NoWrap) {
5538 // Check Add for unsigned overflow.
5539 // TODO: More sophisticated things could be done here.
5540 const Type *WideTy = IntegerType::get(getContext(),
5541 getTypeSizeInBits(Ty) + 1);
5542 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5543 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5544 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5545 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5546 return getCouldNotCompute();
5547 }
5548
5549 return getUDivExpr(Add, Step);
5550 }
5551
5552 /// HowManyLessThans - Return the number of times a backedge containing the
5553 /// specified less-than comparison will execute. If not computable, return
5554 /// CouldNotCompute.
5555 ScalarEvolution::BackedgeTakenInfo
HowManyLessThans(const SCEV * LHS,const SCEV * RHS,const Loop * L,bool isSigned)5556 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5557 const Loop *L, bool isSigned) {
5558 // Only handle: "ADDREC < LoopInvariant".
5559 if (!RHS->isLoopInvariant(L)) return getCouldNotCompute();
5560
5561 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5562 if (!AddRec || AddRec->getLoop() != L)
5563 return getCouldNotCompute();
5564
5565 // Check to see if we have a flag which makes analysis easy.
5566 bool NoWrap = isSigned ? AddRec->hasNoSignedWrap() :
5567 AddRec->hasNoUnsignedWrap();
5568
5569 if (AddRec->isAffine()) {
5570 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5571 const SCEV *Step = AddRec->getStepRecurrence(*this);
5572
5573 if (Step->isZero())
5574 return getCouldNotCompute();
5575 if (Step->isOne()) {
5576 // With unit stride, the iteration never steps past the limit value.
5577 } else if (isKnownPositive(Step)) {
5578 // Test whether a positive iteration can step past the limit
5579 // value and past the maximum value for its type in a single step.
5580 // Note that it's not sufficient to check NoWrap here, because even
5581 // though the value after a wrap is undefined, it's not undefined
5582 // behavior, so if wrap does occur, the loop could either terminate or
5583 // loop infinitely, but in either case, the loop is guaranteed to
5584 // iterate at least until the iteration where the wrapping occurs.
5585 const SCEV *One = getConstant(Step->getType(), 1);
5586 if (isSigned) {
5587 APInt Max = APInt::getSignedMaxValue(BitWidth);
5588 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5589 .slt(getSignedRange(RHS).getSignedMax()))
5590 return getCouldNotCompute();
5591 } else {
5592 APInt Max = APInt::getMaxValue(BitWidth);
5593 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5594 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5595 return getCouldNotCompute();
5596 }
5597 } else
5598 // TODO: Handle negative strides here and below.
5599 return getCouldNotCompute();
5600
5601 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5602 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5603 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5604 // treat m-n as signed nor unsigned due to overflow possibility.
5605
5606 // First, we get the value of the LHS in the first iteration: n
5607 const SCEV *Start = AddRec->getOperand(0);
5608
5609 // Determine the minimum constant start value.
5610 const SCEV *MinStart = getConstant(isSigned ?
5611 getSignedRange(Start).getSignedMin() :
5612 getUnsignedRange(Start).getUnsignedMin());
5613
5614 // If we know that the condition is true in order to enter the loop,
5615 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5616 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5617 // the division must round up.
5618 const SCEV *End = RHS;
5619 if (!isLoopEntryGuardedByCond(L,
5620 isSigned ? ICmpInst::ICMP_SLT :
5621 ICmpInst::ICMP_ULT,
5622 getMinusSCEV(Start, Step), RHS))
5623 End = isSigned ? getSMaxExpr(RHS, Start)
5624 : getUMaxExpr(RHS, Start);
5625
5626 // Determine the maximum constant end value.
5627 const SCEV *MaxEnd = getConstant(isSigned ?
5628 getSignedRange(End).getSignedMax() :
5629 getUnsignedRange(End).getUnsignedMax());
5630
5631 // If MaxEnd is within a step of the maximum integer value in its type,
5632 // adjust it down to the minimum value which would produce the same effect.
5633 // This allows the subsequent ceiling division of (N+(step-1))/step to
5634 // compute the correct value.
5635 const SCEV *StepMinusOne = getMinusSCEV(Step,
5636 getConstant(Step->getType(), 1));
5637 MaxEnd = isSigned ?
5638 getSMinExpr(MaxEnd,
5639 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5640 StepMinusOne)) :
5641 getUMinExpr(MaxEnd,
5642 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5643 StepMinusOne));
5644
5645 // Finally, we subtract these two values and divide, rounding up, to get
5646 // the number of times the backedge is executed.
5647 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5648
5649 // The maximum backedge count is similar, except using the minimum start
5650 // value and the maximum end value.
5651 const SCEV *MaxBECount = getBECount(MinStart, MaxEnd, Step, NoWrap);
5652
5653 return BackedgeTakenInfo(BECount, MaxBECount);
5654 }
5655
5656 return getCouldNotCompute();
5657 }
5658
5659 /// getNumIterationsInRange - Return the number of iterations of this loop that
5660 /// produce values in the specified constant range. Another way of looking at
5661 /// this is that it returns the first iteration number where the value is not in
5662 /// the condition, thus computing the exit count. If the iteration count can't
5663 /// be computed, an instance of SCEVCouldNotCompute is returned.
getNumIterationsInRange(ConstantRange Range,ScalarEvolution & SE) const5664 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5665 ScalarEvolution &SE) const {
5666 if (Range.isFullSet()) // Infinite loop.
5667 return SE.getCouldNotCompute();
5668
5669 // If the start is a non-zero constant, shift the range to simplify things.
5670 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5671 if (!SC->getValue()->isZero()) {
5672 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5673 Operands[0] = SE.getConstant(SC->getType(), 0);
5674 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop());
5675 if (const SCEVAddRecExpr *ShiftedAddRec =
5676 dyn_cast<SCEVAddRecExpr>(Shifted))
5677 return ShiftedAddRec->getNumIterationsInRange(
5678 Range.subtract(SC->getValue()->getValue()), SE);
5679 // This is strange and shouldn't happen.
5680 return SE.getCouldNotCompute();
5681 }
5682
5683 // The only time we can solve this is when we have all constant indices.
5684 // Otherwise, we cannot determine the overflow conditions.
5685 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5686 if (!isa<SCEVConstant>(getOperand(i)))
5687 return SE.getCouldNotCompute();
5688
5689
5690 // Okay at this point we know that all elements of the chrec are constants and
5691 // that the start element is zero.
5692
5693 // First check to see if the range contains zero. If not, the first
5694 // iteration exits.
5695 unsigned BitWidth = SE.getTypeSizeInBits(getType());
5696 if (!Range.contains(APInt(BitWidth, 0)))
5697 return SE.getConstant(getType(), 0);
5698
5699 if (isAffine()) {
5700 // If this is an affine expression then we have this situation:
5701 // Solve {0,+,A} in Range === Ax in Range
5702
5703 // We know that zero is in the range. If A is positive then we know that
5704 // the upper value of the range must be the first possible exit value.
5705 // If A is negative then the lower of the range is the last possible loop
5706 // value. Also note that we already checked for a full range.
5707 APInt One(BitWidth,1);
5708 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
5709 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
5710
5711 // The exit value should be (End+A)/A.
5712 APInt ExitVal = (End + A).udiv(A);
5713 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
5714
5715 // Evaluate at the exit value. If we really did fall out of the valid
5716 // range, then we computed our trip count, otherwise wrap around or other
5717 // things must have happened.
5718 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
5719 if (Range.contains(Val->getValue()))
5720 return SE.getCouldNotCompute(); // Something strange happened
5721
5722 // Ensure that the previous value is in the range. This is a sanity check.
5723 assert(Range.contains(
5724 EvaluateConstantChrecAtConstant(this,
5725 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
5726 "Linear scev computation is off in a bad way!");
5727 return SE.getConstant(ExitValue);
5728 } else if (isQuadratic()) {
5729 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
5730 // quadratic equation to solve it. To do this, we must frame our problem in
5731 // terms of figuring out when zero is crossed, instead of when
5732 // Range.getUpper() is crossed.
5733 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
5734 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
5735 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
5736
5737 // Next, solve the constructed addrec
5738 std::pair<const SCEV *,const SCEV *> Roots =
5739 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
5740 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5741 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5742 if (R1) {
5743 // Pick the smallest positive root value.
5744 if (ConstantInt *CB =
5745 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
5746 R1->getValue(), R2->getValue()))) {
5747 if (CB->getZExtValue() == false)
5748 std::swap(R1, R2); // R1 is the minimum root now.
5749
5750 // Make sure the root is not off by one. The returned iteration should
5751 // not be in the range, but the previous one should be. When solving
5752 // for "X*X < 5", for example, we should not return a root of 2.
5753 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
5754 R1->getValue(),
5755 SE);
5756 if (Range.contains(R1Val->getValue())) {
5757 // The next iteration must be out of the range...
5758 ConstantInt *NextVal =
5759 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
5760
5761 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5762 if (!Range.contains(R1Val->getValue()))
5763 return SE.getConstant(NextVal);
5764 return SE.getCouldNotCompute(); // Something strange happened
5765 }
5766
5767 // If R1 was not in the range, then it is a good return value. Make
5768 // sure that R1-1 WAS in the range though, just in case.
5769 ConstantInt *NextVal =
5770 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
5771 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5772 if (Range.contains(R1Val->getValue()))
5773 return R1;
5774 return SE.getCouldNotCompute(); // Something strange happened
5775 }
5776 }
5777 }
5778
5779 return SE.getCouldNotCompute();
5780 }
5781
5782
5783
5784 //===----------------------------------------------------------------------===//
5785 // SCEVCallbackVH Class Implementation
5786 //===----------------------------------------------------------------------===//
5787
deleted()5788 void ScalarEvolution::SCEVCallbackVH::deleted() {
5789 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5790 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
5791 SE->ConstantEvolutionLoopExitValue.erase(PN);
5792 SE->ValueExprMap.erase(getValPtr());
5793 // this now dangles!
5794 }
5795
allUsesReplacedWith(Value * V)5796 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
5797 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5798
5799 // Forget all the expressions associated with users of the old value,
5800 // so that future queries will recompute the expressions using the new
5801 // value.
5802 Value *Old = getValPtr();
5803 SmallVector<User *, 16> Worklist;
5804 SmallPtrSet<User *, 8> Visited;
5805 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
5806 UI != UE; ++UI)
5807 Worklist.push_back(*UI);
5808 while (!Worklist.empty()) {
5809 User *U = Worklist.pop_back_val();
5810 // Deleting the Old value will cause this to dangle. Postpone
5811 // that until everything else is done.
5812 if (U == Old)
5813 continue;
5814 if (!Visited.insert(U))
5815 continue;
5816 if (PHINode *PN = dyn_cast<PHINode>(U))
5817 SE->ConstantEvolutionLoopExitValue.erase(PN);
5818 SE->ValueExprMap.erase(U);
5819 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
5820 UI != UE; ++UI)
5821 Worklist.push_back(*UI);
5822 }
5823 // Delete the Old value.
5824 if (PHINode *PN = dyn_cast<PHINode>(Old))
5825 SE->ConstantEvolutionLoopExitValue.erase(PN);
5826 SE->ValueExprMap.erase(Old);
5827 // this now dangles!
5828 }
5829
SCEVCallbackVH(Value * V,ScalarEvolution * se)5830 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
5831 : CallbackVH(V), SE(se) {}
5832
5833 //===----------------------------------------------------------------------===//
5834 // ScalarEvolution Class Implementation
5835 //===----------------------------------------------------------------------===//
5836
ScalarEvolution()5837 ScalarEvolution::ScalarEvolution()
5838 : FunctionPass(ID), FirstUnknown(0) {
5839 }
5840
runOnFunction(Function & F)5841 bool ScalarEvolution::runOnFunction(Function &F) {
5842 this->F = &F;
5843 LI = &getAnalysis<LoopInfo>();
5844 TD = getAnalysisIfAvailable<TargetData>();
5845 DT = &getAnalysis<DominatorTree>();
5846 return false;
5847 }
5848
releaseMemory()5849 void ScalarEvolution::releaseMemory() {
5850 // Iterate through all the SCEVUnknown instances and call their
5851 // destructors, so that they release their references to their values.
5852 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
5853 U->~SCEVUnknown();
5854 FirstUnknown = 0;
5855
5856 ValueExprMap.clear();
5857 BackedgeTakenCounts.clear();
5858 ConstantEvolutionLoopExitValue.clear();
5859 ValuesAtScopes.clear();
5860 UniqueSCEVs.clear();
5861 SCEVAllocator.Reset();
5862 }
5863
getAnalysisUsage(AnalysisUsage & AU) const5864 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
5865 AU.setPreservesAll();
5866 AU.addRequiredTransitive<LoopInfo>();
5867 AU.addRequiredTransitive<DominatorTree>();
5868 }
5869
hasLoopInvariantBackedgeTakenCount(const Loop * L)5870 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
5871 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
5872 }
5873
PrintLoopInfo(raw_ostream & OS,ScalarEvolution * SE,const Loop * L)5874 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
5875 const Loop *L) {
5876 // Print all inner loops first
5877 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
5878 PrintLoopInfo(OS, SE, *I);
5879
5880 OS << "Loop ";
5881 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5882 OS << ": ";
5883
5884 SmallVector<BasicBlock *, 8> ExitBlocks;
5885 L->getExitBlocks(ExitBlocks);
5886 if (ExitBlocks.size() != 1)
5887 OS << "<multiple exits> ";
5888
5889 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
5890 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
5891 } else {
5892 OS << "Unpredictable backedge-taken count. ";
5893 }
5894
5895 OS << "\n"
5896 "Loop ";
5897 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5898 OS << ": ";
5899
5900 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
5901 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
5902 } else {
5903 OS << "Unpredictable max backedge-taken count. ";
5904 }
5905
5906 OS << "\n";
5907 }
5908
print(raw_ostream & OS,const Module *) const5909 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
5910 // ScalarEvolution's implementation of the print method is to print
5911 // out SCEV values of all instructions that are interesting. Doing
5912 // this potentially causes it to create new SCEV objects though,
5913 // which technically conflicts with the const qualifier. This isn't
5914 // observable from outside the class though, so casting away the
5915 // const isn't dangerous.
5916 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
5917
5918 OS << "Classifying expressions for: ";
5919 WriteAsOperand(OS, F, /*PrintType=*/false);
5920 OS << "\n";
5921 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
5922 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
5923 OS << *I << '\n';
5924 OS << " --> ";
5925 const SCEV *SV = SE.getSCEV(&*I);
5926 SV->print(OS);
5927
5928 const Loop *L = LI->getLoopFor((*I).getParent());
5929
5930 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
5931 if (AtUse != SV) {
5932 OS << " --> ";
5933 AtUse->print(OS);
5934 }
5935
5936 if (L) {
5937 OS << "\t\t" "Exits: ";
5938 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
5939 if (!ExitValue->isLoopInvariant(L)) {
5940 OS << "<<Unknown>>";
5941 } else {
5942 OS << *ExitValue;
5943 }
5944 }
5945
5946 OS << "\n";
5947 }
5948
5949 OS << "Determining loop execution counts for: ";
5950 WriteAsOperand(OS, F, /*PrintType=*/false);
5951 OS << "\n";
5952 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
5953 PrintLoopInfo(OS, &SE, *I);
5954 }
5955
5956