1 //===- CorrelatedValuePropagation.cpp - Propagate CFG-derived info --------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the Correlated Value Propagation pass.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
14 #include "llvm/ADT/DepthFirstIterator.h"
15 #include "llvm/ADT/Optional.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/Statistic.h"
18 #include "llvm/Analysis/DomTreeUpdater.h"
19 #include "llvm/Analysis/GlobalsModRef.h"
20 #include "llvm/Analysis/InstructionSimplify.h"
21 #include "llvm/Analysis/LazyValueInfo.h"
22 #include "llvm/IR/Attributes.h"
23 #include "llvm/IR/BasicBlock.h"
24 #include "llvm/IR/CFG.h"
25 #include "llvm/IR/Constant.h"
26 #include "llvm/IR/ConstantRange.h"
27 #include "llvm/IR/Constants.h"
28 #include "llvm/IR/DerivedTypes.h"
29 #include "llvm/IR/Function.h"
30 #include "llvm/IR/IRBuilder.h"
31 #include "llvm/IR/InstrTypes.h"
32 #include "llvm/IR/Instruction.h"
33 #include "llvm/IR/Instructions.h"
34 #include "llvm/IR/IntrinsicInst.h"
35 #include "llvm/IR/Operator.h"
36 #include "llvm/IR/PassManager.h"
37 #include "llvm/IR/Type.h"
38 #include "llvm/IR/Value.h"
39 #include "llvm/InitializePasses.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Support/Casting.h"
42 #include "llvm/Support/CommandLine.h"
43 #include "llvm/Support/Debug.h"
44 #include "llvm/Support/raw_ostream.h"
45 #include "llvm/Transforms/Scalar.h"
46 #include "llvm/Transforms/Utils/Local.h"
47 #include <cassert>
48 #include <utility>
49
50 using namespace llvm;
51
52 #define DEBUG_TYPE "correlated-value-propagation"
53
54 STATISTIC(NumPhis, "Number of phis propagated");
55 STATISTIC(NumPhiCommon, "Number of phis deleted via common incoming value");
56 STATISTIC(NumSelects, "Number of selects propagated");
57 STATISTIC(NumMemAccess, "Number of memory access targets propagated");
58 STATISTIC(NumCmps, "Number of comparisons propagated");
59 STATISTIC(NumReturns, "Number of return values propagated");
60 STATISTIC(NumDeadCases, "Number of switch cases removed");
61 STATISTIC(NumSDivSRemsNarrowed,
62 "Number of sdivs/srems whose width was decreased");
63 STATISTIC(NumSDivs, "Number of sdiv converted to udiv");
64 STATISTIC(NumUDivURemsNarrowed,
65 "Number of udivs/urems whose width was decreased");
66 STATISTIC(NumAShrs, "Number of ashr converted to lshr");
67 STATISTIC(NumSRems, "Number of srem converted to urem");
68 STATISTIC(NumSExt, "Number of sext converted to zext");
69 STATISTIC(NumAnd, "Number of ands removed");
70 STATISTIC(NumNW, "Number of no-wrap deductions");
71 STATISTIC(NumNSW, "Number of no-signed-wrap deductions");
72 STATISTIC(NumNUW, "Number of no-unsigned-wrap deductions");
73 STATISTIC(NumAddNW, "Number of no-wrap deductions for add");
74 STATISTIC(NumAddNSW, "Number of no-signed-wrap deductions for add");
75 STATISTIC(NumAddNUW, "Number of no-unsigned-wrap deductions for add");
76 STATISTIC(NumSubNW, "Number of no-wrap deductions for sub");
77 STATISTIC(NumSubNSW, "Number of no-signed-wrap deductions for sub");
78 STATISTIC(NumSubNUW, "Number of no-unsigned-wrap deductions for sub");
79 STATISTIC(NumMulNW, "Number of no-wrap deductions for mul");
80 STATISTIC(NumMulNSW, "Number of no-signed-wrap deductions for mul");
81 STATISTIC(NumMulNUW, "Number of no-unsigned-wrap deductions for mul");
82 STATISTIC(NumShlNW, "Number of no-wrap deductions for shl");
83 STATISTIC(NumShlNSW, "Number of no-signed-wrap deductions for shl");
84 STATISTIC(NumShlNUW, "Number of no-unsigned-wrap deductions for shl");
85 STATISTIC(NumAbs, "Number of llvm.abs intrinsics removed");
86 STATISTIC(NumOverflows, "Number of overflow checks removed");
87 STATISTIC(NumSaturating,
88 "Number of saturating arithmetics converted to normal arithmetics");
89 STATISTIC(NumNonNull, "Number of function pointer arguments marked non-null");
90 STATISTIC(NumMinMax, "Number of llvm.[us]{min,max} intrinsics removed");
91
92 namespace {
93
94 class CorrelatedValuePropagation : public FunctionPass {
95 public:
96 static char ID;
97
CorrelatedValuePropagation()98 CorrelatedValuePropagation(): FunctionPass(ID) {
99 initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
100 }
101
102 bool runOnFunction(Function &F) override;
103
getAnalysisUsage(AnalysisUsage & AU) const104 void getAnalysisUsage(AnalysisUsage &AU) const override {
105 AU.addRequired<DominatorTreeWrapperPass>();
106 AU.addRequired<LazyValueInfoWrapperPass>();
107 AU.addPreserved<GlobalsAAWrapperPass>();
108 AU.addPreserved<DominatorTreeWrapperPass>();
109 AU.addPreserved<LazyValueInfoWrapperPass>();
110 }
111 };
112
113 } // end anonymous namespace
114
115 char CorrelatedValuePropagation::ID = 0;
116
117 INITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
118 "Value Propagation", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)119 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
120 INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
121 INITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
122 "Value Propagation", false, false)
123
124 // Public interface to the Value Propagation pass
125 Pass *llvm::createCorrelatedValuePropagationPass() {
126 return new CorrelatedValuePropagation();
127 }
128
processSelect(SelectInst * S,LazyValueInfo * LVI)129 static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
130 if (S->getType()->isVectorTy()) return false;
131 if (isa<Constant>(S->getCondition())) return false;
132
133 Constant *C = LVI->getConstant(S->getCondition(), S);
134 if (!C) return false;
135
136 ConstantInt *CI = dyn_cast<ConstantInt>(C);
137 if (!CI) return false;
138
139 Value *ReplaceWith = CI->isOne() ? S->getTrueValue() : S->getFalseValue();
140 S->replaceAllUsesWith(ReplaceWith);
141 S->eraseFromParent();
142
143 ++NumSelects;
144
145 return true;
146 }
147
148 /// Try to simplify a phi with constant incoming values that match the edge
149 /// values of a non-constant value on all other edges:
150 /// bb0:
151 /// %isnull = icmp eq i8* %x, null
152 /// br i1 %isnull, label %bb2, label %bb1
153 /// bb1:
154 /// br label %bb2
155 /// bb2:
156 /// %r = phi i8* [ %x, %bb1 ], [ null, %bb0 ]
157 /// -->
158 /// %r = %x
simplifyCommonValuePhi(PHINode * P,LazyValueInfo * LVI,DominatorTree * DT)159 static bool simplifyCommonValuePhi(PHINode *P, LazyValueInfo *LVI,
160 DominatorTree *DT) {
161 // Collect incoming constants and initialize possible common value.
162 SmallVector<std::pair<Constant *, unsigned>, 4> IncomingConstants;
163 Value *CommonValue = nullptr;
164 for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
165 Value *Incoming = P->getIncomingValue(i);
166 if (auto *IncomingConstant = dyn_cast<Constant>(Incoming)) {
167 IncomingConstants.push_back(std::make_pair(IncomingConstant, i));
168 } else if (!CommonValue) {
169 // The potential common value is initialized to the first non-constant.
170 CommonValue = Incoming;
171 } else if (Incoming != CommonValue) {
172 // There can be only one non-constant common value.
173 return false;
174 }
175 }
176
177 if (!CommonValue || IncomingConstants.empty())
178 return false;
179
180 // The common value must be valid in all incoming blocks.
181 BasicBlock *ToBB = P->getParent();
182 if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
183 if (!DT->dominates(CommonInst, ToBB))
184 return false;
185
186 // We have a phi with exactly 1 variable incoming value and 1 or more constant
187 // incoming values. See if all constant incoming values can be mapped back to
188 // the same incoming variable value.
189 for (auto &IncomingConstant : IncomingConstants) {
190 Constant *C = IncomingConstant.first;
191 BasicBlock *IncomingBB = P->getIncomingBlock(IncomingConstant.second);
192 if (C != LVI->getConstantOnEdge(CommonValue, IncomingBB, ToBB, P))
193 return false;
194 }
195
196 // All constant incoming values map to the same variable along the incoming
197 // edges of the phi. The phi is unnecessary. However, we must drop all
198 // poison-generating flags to ensure that no poison is propagated to the phi
199 // location by performing this substitution.
200 // Warning: If the underlying analysis changes, this may not be enough to
201 // guarantee that poison is not propagated.
202 // TODO: We may be able to re-infer flags by re-analyzing the instruction.
203 if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
204 CommonInst->dropPoisonGeneratingFlags();
205 P->replaceAllUsesWith(CommonValue);
206 P->eraseFromParent();
207 ++NumPhiCommon;
208 return true;
209 }
210
processPHI(PHINode * P,LazyValueInfo * LVI,DominatorTree * DT,const SimplifyQuery & SQ)211 static bool processPHI(PHINode *P, LazyValueInfo *LVI, DominatorTree *DT,
212 const SimplifyQuery &SQ) {
213 bool Changed = false;
214
215 BasicBlock *BB = P->getParent();
216 for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
217 Value *Incoming = P->getIncomingValue(i);
218 if (isa<Constant>(Incoming)) continue;
219
220 Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB, P);
221
222 // Look if the incoming value is a select with a scalar condition for which
223 // LVI can tells us the value. In that case replace the incoming value with
224 // the appropriate value of the select. This often allows us to remove the
225 // select later.
226 if (!V) {
227 SelectInst *SI = dyn_cast<SelectInst>(Incoming);
228 if (!SI) continue;
229
230 Value *Condition = SI->getCondition();
231 if (!Condition->getType()->isVectorTy()) {
232 if (Constant *C = LVI->getConstantOnEdge(
233 Condition, P->getIncomingBlock(i), BB, P)) {
234 if (C->isOneValue()) {
235 V = SI->getTrueValue();
236 } else if (C->isZeroValue()) {
237 V = SI->getFalseValue();
238 }
239 // Once LVI learns to handle vector types, we could also add support
240 // for vector type constants that are not all zeroes or all ones.
241 }
242 }
243
244 // Look if the select has a constant but LVI tells us that the incoming
245 // value can never be that constant. In that case replace the incoming
246 // value with the other value of the select. This often allows us to
247 // remove the select later.
248 if (!V) {
249 Constant *C = dyn_cast<Constant>(SI->getFalseValue());
250 if (!C) continue;
251
252 if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
253 P->getIncomingBlock(i), BB, P) !=
254 LazyValueInfo::False)
255 continue;
256 V = SI->getTrueValue();
257 }
258
259 LLVM_DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
260 }
261
262 P->setIncomingValue(i, V);
263 Changed = true;
264 }
265
266 if (Value *V = SimplifyInstruction(P, SQ)) {
267 P->replaceAllUsesWith(V);
268 P->eraseFromParent();
269 Changed = true;
270 }
271
272 if (!Changed)
273 Changed = simplifyCommonValuePhi(P, LVI, DT);
274
275 if (Changed)
276 ++NumPhis;
277
278 return Changed;
279 }
280
processMemAccess(Instruction * I,LazyValueInfo * LVI)281 static bool processMemAccess(Instruction *I, LazyValueInfo *LVI) {
282 Value *Pointer = nullptr;
283 if (LoadInst *L = dyn_cast<LoadInst>(I))
284 Pointer = L->getPointerOperand();
285 else
286 Pointer = cast<StoreInst>(I)->getPointerOperand();
287
288 if (isa<Constant>(Pointer)) return false;
289
290 Constant *C = LVI->getConstant(Pointer, I);
291 if (!C) return false;
292
293 ++NumMemAccess;
294 I->replaceUsesOfWith(Pointer, C);
295 return true;
296 }
297
298 /// See if LazyValueInfo's ability to exploit edge conditions or range
299 /// information is sufficient to prove this comparison. Even for local
300 /// conditions, this can sometimes prove conditions instcombine can't by
301 /// exploiting range information.
processCmp(CmpInst * Cmp,LazyValueInfo * LVI)302 static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
303 Value *Op0 = Cmp->getOperand(0);
304 auto *C = dyn_cast<Constant>(Cmp->getOperand(1));
305 if (!C)
306 return false;
307
308 LazyValueInfo::Tristate Result =
309 LVI->getPredicateAt(Cmp->getPredicate(), Op0, C, Cmp,
310 /*UseBlockValue=*/true);
311 if (Result == LazyValueInfo::Unknown)
312 return false;
313
314 ++NumCmps;
315 Constant *TorF = ConstantInt::get(Type::getInt1Ty(Cmp->getContext()), Result);
316 Cmp->replaceAllUsesWith(TorF);
317 Cmp->eraseFromParent();
318 return true;
319 }
320
321 /// Simplify a switch instruction by removing cases which can never fire. If the
322 /// uselessness of a case could be determined locally then constant propagation
323 /// would already have figured it out. Instead, walk the predecessors and
324 /// statically evaluate cases based on information available on that edge. Cases
325 /// that cannot fire no matter what the incoming edge can safely be removed. If
326 /// a case fires on every incoming edge then the entire switch can be removed
327 /// and replaced with a branch to the case destination.
processSwitch(SwitchInst * I,LazyValueInfo * LVI,DominatorTree * DT)328 static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
329 DominatorTree *DT) {
330 DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Lazy);
331 Value *Cond = I->getCondition();
332 BasicBlock *BB = I->getParent();
333
334 // Analyse each switch case in turn.
335 bool Changed = false;
336 DenseMap<BasicBlock*, int> SuccessorsCount;
337 for (auto *Succ : successors(BB))
338 SuccessorsCount[Succ]++;
339
340 { // Scope for SwitchInstProfUpdateWrapper. It must not live during
341 // ConstantFoldTerminator() as the underlying SwitchInst can be changed.
342 SwitchInstProfUpdateWrapper SI(*I);
343
344 for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
345 ConstantInt *Case = CI->getCaseValue();
346 LazyValueInfo::Tristate State =
347 LVI->getPredicateAt(CmpInst::ICMP_EQ, Cond, Case, I,
348 /* UseBlockValue */ true);
349
350 if (State == LazyValueInfo::False) {
351 // This case never fires - remove it.
352 BasicBlock *Succ = CI->getCaseSuccessor();
353 Succ->removePredecessor(BB);
354 CI = SI.removeCase(CI);
355 CE = SI->case_end();
356
357 // The condition can be modified by removePredecessor's PHI simplification
358 // logic.
359 Cond = SI->getCondition();
360
361 ++NumDeadCases;
362 Changed = true;
363 if (--SuccessorsCount[Succ] == 0)
364 DTU.applyUpdatesPermissive({{DominatorTree::Delete, BB, Succ}});
365 continue;
366 }
367 if (State == LazyValueInfo::True) {
368 // This case always fires. Arrange for the switch to be turned into an
369 // unconditional branch by replacing the switch condition with the case
370 // value.
371 SI->setCondition(Case);
372 NumDeadCases += SI->getNumCases();
373 Changed = true;
374 break;
375 }
376
377 // Increment the case iterator since we didn't delete it.
378 ++CI;
379 }
380 }
381
382 if (Changed)
383 // If the switch has been simplified to the point where it can be replaced
384 // by a branch then do so now.
385 ConstantFoldTerminator(BB, /*DeleteDeadConditions = */ false,
386 /*TLI = */ nullptr, &DTU);
387 return Changed;
388 }
389
390 // See if we can prove that the given binary op intrinsic will not overflow.
willNotOverflow(BinaryOpIntrinsic * BO,LazyValueInfo * LVI)391 static bool willNotOverflow(BinaryOpIntrinsic *BO, LazyValueInfo *LVI) {
392 ConstantRange LRange = LVI->getConstantRange(BO->getLHS(), BO);
393 ConstantRange RRange = LVI->getConstantRange(BO->getRHS(), BO);
394 ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
395 BO->getBinaryOp(), RRange, BO->getNoWrapKind());
396 return NWRegion.contains(LRange);
397 }
398
setDeducedOverflowingFlags(Value * V,Instruction::BinaryOps Opcode,bool NewNSW,bool NewNUW)399 static void setDeducedOverflowingFlags(Value *V, Instruction::BinaryOps Opcode,
400 bool NewNSW, bool NewNUW) {
401 Statistic *OpcNW, *OpcNSW, *OpcNUW;
402 switch (Opcode) {
403 case Instruction::Add:
404 OpcNW = &NumAddNW;
405 OpcNSW = &NumAddNSW;
406 OpcNUW = &NumAddNUW;
407 break;
408 case Instruction::Sub:
409 OpcNW = &NumSubNW;
410 OpcNSW = &NumSubNSW;
411 OpcNUW = &NumSubNUW;
412 break;
413 case Instruction::Mul:
414 OpcNW = &NumMulNW;
415 OpcNSW = &NumMulNSW;
416 OpcNUW = &NumMulNUW;
417 break;
418 case Instruction::Shl:
419 OpcNW = &NumShlNW;
420 OpcNSW = &NumShlNSW;
421 OpcNUW = &NumShlNUW;
422 break;
423 default:
424 llvm_unreachable("Will not be called with other binops");
425 }
426
427 auto *Inst = dyn_cast<Instruction>(V);
428 if (NewNSW) {
429 ++NumNW;
430 ++*OpcNW;
431 ++NumNSW;
432 ++*OpcNSW;
433 if (Inst)
434 Inst->setHasNoSignedWrap();
435 }
436 if (NewNUW) {
437 ++NumNW;
438 ++*OpcNW;
439 ++NumNUW;
440 ++*OpcNUW;
441 if (Inst)
442 Inst->setHasNoUnsignedWrap();
443 }
444 }
445
446 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI);
447
448 // See if @llvm.abs argument is alays positive/negative, and simplify.
449 // Notably, INT_MIN can belong to either range, regardless of the NSW,
450 // because it is negation-invariant.
processAbsIntrinsic(IntrinsicInst * II,LazyValueInfo * LVI)451 static bool processAbsIntrinsic(IntrinsicInst *II, LazyValueInfo *LVI) {
452 Value *X = II->getArgOperand(0);
453 bool IsIntMinPoison = cast<ConstantInt>(II->getArgOperand(1))->isOne();
454
455 Type *Ty = X->getType();
456 Constant *IntMin =
457 ConstantInt::get(Ty, APInt::getSignedMinValue(Ty->getScalarSizeInBits()));
458 LazyValueInfo::Tristate Result;
459
460 // Is X in [0, IntMin]? NOTE: INT_MIN is fine!
461 Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_ULE, X, IntMin, II,
462 /*UseBlockValue=*/true);
463 if (Result == LazyValueInfo::True) {
464 ++NumAbs;
465 II->replaceAllUsesWith(X);
466 II->eraseFromParent();
467 return true;
468 }
469
470 // Is X in [IntMin, 0]? NOTE: INT_MIN is fine!
471 Constant *Zero = ConstantInt::getNullValue(Ty);
472 Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_SLE, X, Zero, II,
473 /*UseBlockValue=*/true);
474 assert(Result != LazyValueInfo::False && "Should have been handled already.");
475
476 if (Result == LazyValueInfo::Unknown) {
477 // Argument's range crosses zero.
478 bool Changed = false;
479 if (!IsIntMinPoison) {
480 // Can we at least tell that the argument is never INT_MIN?
481 Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_NE, X, IntMin, II,
482 /*UseBlockValue=*/true);
483 if (Result == LazyValueInfo::True) {
484 ++NumNSW;
485 ++NumSubNSW;
486 II->setArgOperand(1, ConstantInt::getTrue(II->getContext()));
487 Changed = true;
488 }
489 }
490 return Changed;
491 }
492
493 IRBuilder<> B(II);
494 Value *NegX = B.CreateNeg(X, II->getName(), /*HasNUW=*/false,
495 /*HasNSW=*/IsIntMinPoison);
496 ++NumAbs;
497 II->replaceAllUsesWith(NegX);
498 II->eraseFromParent();
499
500 // See if we can infer some no-wrap flags.
501 if (auto *BO = dyn_cast<BinaryOperator>(NegX))
502 processBinOp(BO, LVI);
503
504 return true;
505 }
506
507 // See if this min/max intrinsic always picks it's one specific operand.
processMinMaxIntrinsic(MinMaxIntrinsic * MM,LazyValueInfo * LVI)508 static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
509 CmpInst::Predicate Pred = CmpInst::getNonStrictPredicate(MM->getPredicate());
510 LazyValueInfo::Tristate Result = LVI->getPredicateAt(
511 Pred, MM->getLHS(), MM->getRHS(), MM, /*UseBlockValue=*/true);
512 if (Result == LazyValueInfo::Unknown)
513 return false;
514
515 ++NumMinMax;
516 MM->replaceAllUsesWith(MM->getOperand(!Result));
517 MM->eraseFromParent();
518 return true;
519 }
520
521 // Rewrite this with.overflow intrinsic as non-overflowing.
processOverflowIntrinsic(WithOverflowInst * WO,LazyValueInfo * LVI)522 static bool processOverflowIntrinsic(WithOverflowInst *WO, LazyValueInfo *LVI) {
523 IRBuilder<> B(WO);
524 Instruction::BinaryOps Opcode = WO->getBinaryOp();
525 bool NSW = WO->isSigned();
526 bool NUW = !WO->isSigned();
527
528 Value *NewOp =
529 B.CreateBinOp(Opcode, WO->getLHS(), WO->getRHS(), WO->getName());
530 setDeducedOverflowingFlags(NewOp, Opcode, NSW, NUW);
531
532 StructType *ST = cast<StructType>(WO->getType());
533 Constant *Struct = ConstantStruct::get(ST,
534 { UndefValue::get(ST->getElementType(0)),
535 ConstantInt::getFalse(ST->getElementType(1)) });
536 Value *NewI = B.CreateInsertValue(Struct, NewOp, 0);
537 WO->replaceAllUsesWith(NewI);
538 WO->eraseFromParent();
539 ++NumOverflows;
540
541 // See if we can infer the other no-wrap too.
542 if (auto *BO = dyn_cast<BinaryOperator>(NewOp))
543 processBinOp(BO, LVI);
544
545 return true;
546 }
547
processSaturatingInst(SaturatingInst * SI,LazyValueInfo * LVI)548 static bool processSaturatingInst(SaturatingInst *SI, LazyValueInfo *LVI) {
549 Instruction::BinaryOps Opcode = SI->getBinaryOp();
550 bool NSW = SI->isSigned();
551 bool NUW = !SI->isSigned();
552 BinaryOperator *BinOp = BinaryOperator::Create(
553 Opcode, SI->getLHS(), SI->getRHS(), SI->getName(), SI);
554 BinOp->setDebugLoc(SI->getDebugLoc());
555 setDeducedOverflowingFlags(BinOp, Opcode, NSW, NUW);
556
557 SI->replaceAllUsesWith(BinOp);
558 SI->eraseFromParent();
559 ++NumSaturating;
560
561 // See if we can infer the other no-wrap too.
562 if (auto *BO = dyn_cast<BinaryOperator>(BinOp))
563 processBinOp(BO, LVI);
564
565 return true;
566 }
567
568 /// Infer nonnull attributes for the arguments at the specified callsite.
processCallSite(CallBase & CB,LazyValueInfo * LVI)569 static bool processCallSite(CallBase &CB, LazyValueInfo *LVI) {
570
571 if (CB.getIntrinsicID() == Intrinsic::abs) {
572 return processAbsIntrinsic(&cast<IntrinsicInst>(CB), LVI);
573 }
574
575 if (auto *MM = dyn_cast<MinMaxIntrinsic>(&CB)) {
576 return processMinMaxIntrinsic(MM, LVI);
577 }
578
579 if (auto *WO = dyn_cast<WithOverflowInst>(&CB)) {
580 if (WO->getLHS()->getType()->isIntegerTy() && willNotOverflow(WO, LVI)) {
581 return processOverflowIntrinsic(WO, LVI);
582 }
583 }
584
585 if (auto *SI = dyn_cast<SaturatingInst>(&CB)) {
586 if (SI->getType()->isIntegerTy() && willNotOverflow(SI, LVI)) {
587 return processSaturatingInst(SI, LVI);
588 }
589 }
590
591 bool Changed = false;
592
593 // Deopt bundle operands are intended to capture state with minimal
594 // perturbance of the code otherwise. If we can find a constant value for
595 // any such operand and remove a use of the original value, that's
596 // desireable since it may allow further optimization of that value (e.g. via
597 // single use rules in instcombine). Since deopt uses tend to,
598 // idiomatically, appear along rare conditional paths, it's reasonable likely
599 // we may have a conditional fact with which LVI can fold.
600 if (auto DeoptBundle = CB.getOperandBundle(LLVMContext::OB_deopt)) {
601 for (const Use &ConstU : DeoptBundle->Inputs) {
602 Use &U = const_cast<Use&>(ConstU);
603 Value *V = U.get();
604 if (V->getType()->isVectorTy()) continue;
605 if (isa<Constant>(V)) continue;
606
607 Constant *C = LVI->getConstant(V, &CB);
608 if (!C) continue;
609 U.set(C);
610 Changed = true;
611 }
612 }
613
614 SmallVector<unsigned, 4> ArgNos;
615 unsigned ArgNo = 0;
616
617 for (Value *V : CB.args()) {
618 PointerType *Type = dyn_cast<PointerType>(V->getType());
619 // Try to mark pointer typed parameters as non-null. We skip the
620 // relatively expensive analysis for constants which are obviously either
621 // null or non-null to start with.
622 if (Type && !CB.paramHasAttr(ArgNo, Attribute::NonNull) &&
623 !isa<Constant>(V) &&
624 LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
625 ConstantPointerNull::get(Type), &CB,
626 /*UseBlockValue=*/false) == LazyValueInfo::False)
627 ArgNos.push_back(ArgNo);
628 ArgNo++;
629 }
630
631 assert(ArgNo == CB.arg_size() && "sanity check");
632
633 if (ArgNos.empty())
634 return Changed;
635
636 NumNonNull += ArgNos.size();
637 AttributeList AS = CB.getAttributes();
638 LLVMContext &Ctx = CB.getContext();
639 AS = AS.addParamAttribute(Ctx, ArgNos,
640 Attribute::get(Ctx, Attribute::NonNull));
641 CB.setAttributes(AS);
642
643 return true;
644 }
645
isNonNegative(Value * V,LazyValueInfo * LVI,Instruction * CxtI)646 static bool isNonNegative(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
647 Constant *Zero = ConstantInt::get(V->getType(), 0);
648 auto Result = LVI->getPredicateAt(ICmpInst::ICMP_SGE, V, Zero, CxtI,
649 /*UseBlockValue=*/true);
650 return Result == LazyValueInfo::True;
651 }
652
isNonPositive(Value * V,LazyValueInfo * LVI,Instruction * CxtI)653 static bool isNonPositive(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
654 Constant *Zero = ConstantInt::get(V->getType(), 0);
655 auto Result = LVI->getPredicateAt(ICmpInst::ICMP_SLE, V, Zero, CxtI,
656 /*UseBlockValue=*/true);
657 return Result == LazyValueInfo::True;
658 }
659
660 enum class Domain { NonNegative, NonPositive, Unknown };
661
getDomain(Value * V,LazyValueInfo * LVI,Instruction * CxtI)662 Domain getDomain(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
663 if (isNonNegative(V, LVI, CxtI))
664 return Domain::NonNegative;
665 if (isNonPositive(V, LVI, CxtI))
666 return Domain::NonPositive;
667 return Domain::Unknown;
668 }
669
670 /// Try to shrink a sdiv/srem's width down to the smallest power of two that's
671 /// sufficient to contain its operands.
narrowSDivOrSRem(BinaryOperator * Instr,LazyValueInfo * LVI)672 static bool narrowSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
673 assert(Instr->getOpcode() == Instruction::SDiv ||
674 Instr->getOpcode() == Instruction::SRem);
675 if (Instr->getType()->isVectorTy())
676 return false;
677
678 // Find the smallest power of two bitwidth that's sufficient to hold Instr's
679 // operands.
680 unsigned OrigWidth = Instr->getType()->getIntegerBitWidth();
681
682 // What is the smallest bit width that can accomodate the entire value ranges
683 // of both of the operands?
684 std::array<Optional<ConstantRange>, 2> CRs;
685 unsigned MinSignedBits = 0;
686 for (auto I : zip(Instr->operands(), CRs)) {
687 std::get<1>(I) = LVI->getConstantRange(std::get<0>(I), Instr);
688 MinSignedBits = std::max(std::get<1>(I)->getMinSignedBits(), MinSignedBits);
689 }
690
691 // sdiv/srem is UB if divisor is -1 and divident is INT_MIN, so unless we can
692 // prove that such a combination is impossible, we need to bump the bitwidth.
693 if (CRs[1]->contains(APInt::getAllOnesValue(OrigWidth)) &&
694 CRs[0]->contains(
695 APInt::getSignedMinValue(MinSignedBits).sextOrSelf(OrigWidth)))
696 ++MinSignedBits;
697
698 // Don't shrink below 8 bits wide.
699 unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MinSignedBits), 8);
700
701 // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
702 // two.
703 if (NewWidth >= OrigWidth)
704 return false;
705
706 ++NumSDivSRemsNarrowed;
707 IRBuilder<> B{Instr};
708 auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
709 auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
710 Instr->getName() + ".lhs.trunc");
711 auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
712 Instr->getName() + ".rhs.trunc");
713 auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
714 auto *Sext = B.CreateSExt(BO, Instr->getType(), Instr->getName() + ".sext");
715 if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
716 if (BinOp->getOpcode() == Instruction::SDiv)
717 BinOp->setIsExact(Instr->isExact());
718
719 Instr->replaceAllUsesWith(Sext);
720 Instr->eraseFromParent();
721 return true;
722 }
723
724 /// Try to shrink a udiv/urem's width down to the smallest power of two that's
725 /// sufficient to contain its operands.
processUDivOrURem(BinaryOperator * Instr,LazyValueInfo * LVI)726 static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
727 assert(Instr->getOpcode() == Instruction::UDiv ||
728 Instr->getOpcode() == Instruction::URem);
729 if (Instr->getType()->isVectorTy())
730 return false;
731
732 // Find the smallest power of two bitwidth that's sufficient to hold Instr's
733 // operands.
734
735 // What is the smallest bit width that can accomodate the entire value ranges
736 // of both of the operands?
737 unsigned MaxActiveBits = 0;
738 for (Value *Operand : Instr->operands()) {
739 ConstantRange CR = LVI->getConstantRange(Operand, Instr);
740 MaxActiveBits = std::max(CR.getActiveBits(), MaxActiveBits);
741 }
742 // Don't shrink below 8 bits wide.
743 unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MaxActiveBits), 8);
744
745 // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
746 // two.
747 if (NewWidth >= Instr->getType()->getIntegerBitWidth())
748 return false;
749
750 ++NumUDivURemsNarrowed;
751 IRBuilder<> B{Instr};
752 auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
753 auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
754 Instr->getName() + ".lhs.trunc");
755 auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
756 Instr->getName() + ".rhs.trunc");
757 auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
758 auto *Zext = B.CreateZExt(BO, Instr->getType(), Instr->getName() + ".zext");
759 if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
760 if (BinOp->getOpcode() == Instruction::UDiv)
761 BinOp->setIsExact(Instr->isExact());
762
763 Instr->replaceAllUsesWith(Zext);
764 Instr->eraseFromParent();
765 return true;
766 }
767
processSRem(BinaryOperator * SDI,LazyValueInfo * LVI)768 static bool processSRem(BinaryOperator *SDI, LazyValueInfo *LVI) {
769 assert(SDI->getOpcode() == Instruction::SRem);
770 if (SDI->getType()->isVectorTy())
771 return false;
772
773 struct Operand {
774 Value *V;
775 Domain D;
776 };
777 std::array<Operand, 2> Ops;
778
779 for (const auto I : zip(Ops, SDI->operands())) {
780 Operand &Op = std::get<0>(I);
781 Op.V = std::get<1>(I);
782 Op.D = getDomain(Op.V, LVI, SDI);
783 if (Op.D == Domain::Unknown)
784 return false;
785 }
786
787 // We know domains of both of the operands!
788 ++NumSRems;
789
790 // We need operands to be non-negative, so negate each one that isn't.
791 for (Operand &Op : Ops) {
792 if (Op.D == Domain::NonNegative)
793 continue;
794 auto *BO =
795 BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
796 BO->setDebugLoc(SDI->getDebugLoc());
797 Op.V = BO;
798 }
799
800 auto *URem =
801 BinaryOperator::CreateURem(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
802 URem->setDebugLoc(SDI->getDebugLoc());
803
804 Value *Res = URem;
805
806 // If the divident was non-positive, we need to negate the result.
807 if (Ops[0].D == Domain::NonPositive)
808 Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
809
810 SDI->replaceAllUsesWith(Res);
811 SDI->eraseFromParent();
812
813 // Try to simplify our new urem.
814 processUDivOrURem(URem, LVI);
815
816 return true;
817 }
818
819 /// See if LazyValueInfo's ability to exploit edge conditions or range
820 /// information is sufficient to prove the signs of both operands of this SDiv.
821 /// If this is the case, replace the SDiv with a UDiv. Even for local
822 /// conditions, this can sometimes prove conditions instcombine can't by
823 /// exploiting range information.
processSDiv(BinaryOperator * SDI,LazyValueInfo * LVI)824 static bool processSDiv(BinaryOperator *SDI, LazyValueInfo *LVI) {
825 assert(SDI->getOpcode() == Instruction::SDiv);
826 if (SDI->getType()->isVectorTy())
827 return false;
828
829 struct Operand {
830 Value *V;
831 Domain D;
832 };
833 std::array<Operand, 2> Ops;
834
835 for (const auto I : zip(Ops, SDI->operands())) {
836 Operand &Op = std::get<0>(I);
837 Op.V = std::get<1>(I);
838 Op.D = getDomain(Op.V, LVI, SDI);
839 if (Op.D == Domain::Unknown)
840 return false;
841 }
842
843 // We know domains of both of the operands!
844 ++NumSDivs;
845
846 // We need operands to be non-negative, so negate each one that isn't.
847 for (Operand &Op : Ops) {
848 if (Op.D == Domain::NonNegative)
849 continue;
850 auto *BO =
851 BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
852 BO->setDebugLoc(SDI->getDebugLoc());
853 Op.V = BO;
854 }
855
856 auto *UDiv =
857 BinaryOperator::CreateUDiv(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
858 UDiv->setDebugLoc(SDI->getDebugLoc());
859 UDiv->setIsExact(SDI->isExact());
860
861 Value *Res = UDiv;
862
863 // If the operands had two different domains, we need to negate the result.
864 if (Ops[0].D != Ops[1].D)
865 Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
866
867 SDI->replaceAllUsesWith(Res);
868 SDI->eraseFromParent();
869
870 // Try to simplify our new udiv.
871 processUDivOrURem(UDiv, LVI);
872
873 return true;
874 }
875
processSDivOrSRem(BinaryOperator * Instr,LazyValueInfo * LVI)876 static bool processSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
877 assert(Instr->getOpcode() == Instruction::SDiv ||
878 Instr->getOpcode() == Instruction::SRem);
879 if (Instr->getType()->isVectorTy())
880 return false;
881
882 if (Instr->getOpcode() == Instruction::SDiv)
883 if (processSDiv(Instr, LVI))
884 return true;
885
886 if (Instr->getOpcode() == Instruction::SRem)
887 if (processSRem(Instr, LVI))
888 return true;
889
890 return narrowSDivOrSRem(Instr, LVI);
891 }
892
processAShr(BinaryOperator * SDI,LazyValueInfo * LVI)893 static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
894 if (SDI->getType()->isVectorTy())
895 return false;
896
897 if (!isNonNegative(SDI->getOperand(0), LVI, SDI))
898 return false;
899
900 ++NumAShrs;
901 auto *BO = BinaryOperator::CreateLShr(SDI->getOperand(0), SDI->getOperand(1),
902 SDI->getName(), SDI);
903 BO->setDebugLoc(SDI->getDebugLoc());
904 BO->setIsExact(SDI->isExact());
905 SDI->replaceAllUsesWith(BO);
906 SDI->eraseFromParent();
907
908 return true;
909 }
910
processSExt(SExtInst * SDI,LazyValueInfo * LVI)911 static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
912 if (SDI->getType()->isVectorTy())
913 return false;
914
915 Value *Base = SDI->getOperand(0);
916
917 if (!isNonNegative(Base, LVI, SDI))
918 return false;
919
920 ++NumSExt;
921 auto *ZExt =
922 CastInst::CreateZExtOrBitCast(Base, SDI->getType(), SDI->getName(), SDI);
923 ZExt->setDebugLoc(SDI->getDebugLoc());
924 SDI->replaceAllUsesWith(ZExt);
925 SDI->eraseFromParent();
926
927 return true;
928 }
929
processBinOp(BinaryOperator * BinOp,LazyValueInfo * LVI)930 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
931 using OBO = OverflowingBinaryOperator;
932
933 if (BinOp->getType()->isVectorTy())
934 return false;
935
936 bool NSW = BinOp->hasNoSignedWrap();
937 bool NUW = BinOp->hasNoUnsignedWrap();
938 if (NSW && NUW)
939 return false;
940
941 Instruction::BinaryOps Opcode = BinOp->getOpcode();
942 Value *LHS = BinOp->getOperand(0);
943 Value *RHS = BinOp->getOperand(1);
944
945 ConstantRange LRange = LVI->getConstantRange(LHS, BinOp);
946 ConstantRange RRange = LVI->getConstantRange(RHS, BinOp);
947
948 bool Changed = false;
949 bool NewNUW = false, NewNSW = false;
950 if (!NUW) {
951 ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
952 Opcode, RRange, OBO::NoUnsignedWrap);
953 NewNUW = NUWRange.contains(LRange);
954 Changed |= NewNUW;
955 }
956 if (!NSW) {
957 ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
958 Opcode, RRange, OBO::NoSignedWrap);
959 NewNSW = NSWRange.contains(LRange);
960 Changed |= NewNSW;
961 }
962
963 setDeducedOverflowingFlags(BinOp, Opcode, NewNSW, NewNUW);
964
965 return Changed;
966 }
967
processAnd(BinaryOperator * BinOp,LazyValueInfo * LVI)968 static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
969 if (BinOp->getType()->isVectorTy())
970 return false;
971
972 // Pattern match (and lhs, C) where C includes a superset of bits which might
973 // be set in lhs. This is a common truncation idiom created by instcombine.
974 Value *LHS = BinOp->getOperand(0);
975 ConstantInt *RHS = dyn_cast<ConstantInt>(BinOp->getOperand(1));
976 if (!RHS || !RHS->getValue().isMask())
977 return false;
978
979 // We can only replace the AND with LHS based on range info if the range does
980 // not include undef.
981 ConstantRange LRange =
982 LVI->getConstantRange(LHS, BinOp, /*UndefAllowed=*/false);
983 if (!LRange.getUnsignedMax().ule(RHS->getValue()))
984 return false;
985
986 BinOp->replaceAllUsesWith(LHS);
987 BinOp->eraseFromParent();
988 NumAnd++;
989 return true;
990 }
991
992
getConstantAt(Value * V,Instruction * At,LazyValueInfo * LVI)993 static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
994 if (Constant *C = LVI->getConstant(V, At))
995 return C;
996
997 // TODO: The following really should be sunk inside LVI's core algorithm, or
998 // at least the outer shims around such.
999 auto *C = dyn_cast<CmpInst>(V);
1000 if (!C) return nullptr;
1001
1002 Value *Op0 = C->getOperand(0);
1003 Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
1004 if (!Op1) return nullptr;
1005
1006 LazyValueInfo::Tristate Result = LVI->getPredicateAt(
1007 C->getPredicate(), Op0, Op1, At, /*UseBlockValue=*/false);
1008 if (Result == LazyValueInfo::Unknown)
1009 return nullptr;
1010
1011 return (Result == LazyValueInfo::True) ?
1012 ConstantInt::getTrue(C->getContext()) :
1013 ConstantInt::getFalse(C->getContext());
1014 }
1015
runImpl(Function & F,LazyValueInfo * LVI,DominatorTree * DT,const SimplifyQuery & SQ)1016 static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
1017 const SimplifyQuery &SQ) {
1018 bool FnChanged = false;
1019 // Visiting in a pre-order depth-first traversal causes us to simplify early
1020 // blocks before querying later blocks (which require us to analyze early
1021 // blocks). Eagerly simplifying shallow blocks means there is strictly less
1022 // work to do for deep blocks. This also means we don't visit unreachable
1023 // blocks.
1024 for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
1025 bool BBChanged = false;
1026 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
1027 Instruction *II = &*BI++;
1028 switch (II->getOpcode()) {
1029 case Instruction::Select:
1030 BBChanged |= processSelect(cast<SelectInst>(II), LVI);
1031 break;
1032 case Instruction::PHI:
1033 BBChanged |= processPHI(cast<PHINode>(II), LVI, DT, SQ);
1034 break;
1035 case Instruction::ICmp:
1036 case Instruction::FCmp:
1037 BBChanged |= processCmp(cast<CmpInst>(II), LVI);
1038 break;
1039 case Instruction::Load:
1040 case Instruction::Store:
1041 BBChanged |= processMemAccess(II, LVI);
1042 break;
1043 case Instruction::Call:
1044 case Instruction::Invoke:
1045 BBChanged |= processCallSite(cast<CallBase>(*II), LVI);
1046 break;
1047 case Instruction::SRem:
1048 case Instruction::SDiv:
1049 BBChanged |= processSDivOrSRem(cast<BinaryOperator>(II), LVI);
1050 break;
1051 case Instruction::UDiv:
1052 case Instruction::URem:
1053 BBChanged |= processUDivOrURem(cast<BinaryOperator>(II), LVI);
1054 break;
1055 case Instruction::AShr:
1056 BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
1057 break;
1058 case Instruction::SExt:
1059 BBChanged |= processSExt(cast<SExtInst>(II), LVI);
1060 break;
1061 case Instruction::Add:
1062 case Instruction::Sub:
1063 case Instruction::Mul:
1064 case Instruction::Shl:
1065 BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);
1066 break;
1067 case Instruction::And:
1068 BBChanged |= processAnd(cast<BinaryOperator>(II), LVI);
1069 break;
1070 }
1071 }
1072
1073 Instruction *Term = BB->getTerminator();
1074 switch (Term->getOpcode()) {
1075 case Instruction::Switch:
1076 BBChanged |= processSwitch(cast<SwitchInst>(Term), LVI, DT);
1077 break;
1078 case Instruction::Ret: {
1079 auto *RI = cast<ReturnInst>(Term);
1080 // Try to determine the return value if we can. This is mainly here to
1081 // simplify the writing of unit tests, but also helps to enable IPO by
1082 // constant folding the return values of callees.
1083 auto *RetVal = RI->getReturnValue();
1084 if (!RetVal) break; // handle "ret void"
1085 if (isa<Constant>(RetVal)) break; // nothing to do
1086 if (auto *C = getConstantAt(RetVal, RI, LVI)) {
1087 ++NumReturns;
1088 RI->replaceUsesOfWith(RetVal, C);
1089 BBChanged = true;
1090 }
1091 }
1092 }
1093
1094 FnChanged |= BBChanged;
1095 }
1096
1097 return FnChanged;
1098 }
1099
runOnFunction(Function & F)1100 bool CorrelatedValuePropagation::runOnFunction(Function &F) {
1101 if (skipFunction(F))
1102 return false;
1103
1104 LazyValueInfo *LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
1105 DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1106
1107 return runImpl(F, LVI, DT, getBestSimplifyQuery(*this, F));
1108 }
1109
1110 PreservedAnalyses
run(Function & F,FunctionAnalysisManager & AM)1111 CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
1112 LazyValueInfo *LVI = &AM.getResult<LazyValueAnalysis>(F);
1113 DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
1114
1115 bool Changed = runImpl(F, LVI, DT, getBestSimplifyQuery(AM, F));
1116
1117 PreservedAnalyses PA;
1118 if (!Changed) {
1119 PA = PreservedAnalyses::all();
1120 } else {
1121 PA.preserve<DominatorTreeAnalysis>();
1122 PA.preserve<LazyValueAnalysis>();
1123 }
1124
1125 // Keeping LVI alive is expensive, both because it uses a lot of memory, and
1126 // because invalidating values in LVI is expensive. While CVP does preserve
1127 // LVI, we know that passes after JumpThreading+CVP will not need the result
1128 // of this analysis, so we forcefully discard it early.
1129 PA.abandon<LazyValueAnalysis>();
1130 return PA;
1131 }
1132