1 //===- llvm/Analysis/ScalarEvolutionExpressions.h - SCEV Exprs --*- C++ -*-===// 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 defines the classes used to represent and build scalar expressions. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H 14 #define LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H 15 16 #include "llvm/ADT/DenseMap.h" 17 #include "llvm/ADT/FoldingSet.h" 18 #include "llvm/ADT/SmallPtrSet.h" 19 #include "llvm/ADT/SmallVector.h" 20 #include "llvm/ADT/iterator_range.h" 21 #include "llvm/Analysis/ScalarEvolution.h" 22 #include "llvm/IR/Constants.h" 23 #include "llvm/IR/Value.h" 24 #include "llvm/IR/ValueHandle.h" 25 #include "llvm/Support/Casting.h" 26 #include "llvm/Support/ErrorHandling.h" 27 #include <cassert> 28 #include <cstddef> 29 30 namespace llvm { 31 32 class APInt; 33 class Constant; 34 class ConstantRange; 35 class Loop; 36 class Type; 37 38 enum SCEVTypes : unsigned short { 39 // These should be ordered in terms of increasing complexity to make the 40 // folders simpler. 41 scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr, 42 scUDivExpr, scAddRecExpr, scUMaxExpr, scSMaxExpr, scUMinExpr, scSMinExpr, 43 scPtrToInt, scUnknown, scCouldNotCompute 44 }; 45 46 /// This class represents a constant integer value. 47 class SCEVConstant : public SCEV { 48 friend class ScalarEvolution; 49 50 ConstantInt *V; 51 SCEVConstant(const FoldingSetNodeIDRef ID,ConstantInt * v)52 SCEVConstant(const FoldingSetNodeIDRef ID, ConstantInt *v) : 53 SCEV(ID, scConstant, 1), V(v) {} 54 55 public: getValue()56 ConstantInt *getValue() const { return V; } getAPInt()57 const APInt &getAPInt() const { return getValue()->getValue(); } 58 getType()59 Type *getType() const { return V->getType(); } 60 61 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)62 static bool classof(const SCEV *S) { 63 return S->getSCEVType() == scConstant; 64 } 65 }; 66 computeExpressionSize(ArrayRef<const SCEV * > Args)67 inline unsigned short computeExpressionSize(ArrayRef<const SCEV *> Args) { 68 APInt Size(16, 1); 69 for (auto *Arg : Args) 70 Size = Size.uadd_sat(APInt(16, Arg->getExpressionSize())); 71 return (unsigned short)Size.getZExtValue(); 72 } 73 74 /// This is the base class for unary cast operator classes. 75 class SCEVCastExpr : public SCEV { 76 protected: 77 std::array<const SCEV *, 1> Operands; 78 Type *Ty; 79 80 SCEVCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, const SCEV *op, 81 Type *ty); 82 83 public: getOperand()84 const SCEV *getOperand() const { return Operands[0]; } getOperand(unsigned i)85 const SCEV *getOperand(unsigned i) const { 86 assert(i == 0 && "Operand index out of range!"); 87 return Operands[0]; 88 } 89 using op_iterator = std::array<const SCEV *, 1>::const_iterator; 90 using op_range = iterator_range<op_iterator>; 91 operands()92 op_range operands() const { 93 return make_range(Operands.begin(), Operands.end()); 94 } getNumOperands()95 size_t getNumOperands() const { return 1; } getType()96 Type *getType() const { return Ty; } 97 98 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)99 static bool classof(const SCEV *S) { 100 return S->getSCEVType() == scPtrToInt || S->getSCEVType() == scTruncate || 101 S->getSCEVType() == scZeroExtend || 102 S->getSCEVType() == scSignExtend; 103 } 104 }; 105 106 /// This class represents a cast from a pointer to a pointer-sized integer 107 /// value. 108 class SCEVPtrToIntExpr : public SCEVCastExpr { 109 friend class ScalarEvolution; 110 111 SCEVPtrToIntExpr(const FoldingSetNodeIDRef ID, const SCEV *Op, Type *ITy); 112 113 public: 114 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)115 static bool classof(const SCEV *S) { 116 return S->getSCEVType() == scPtrToInt; 117 } 118 }; 119 120 /// This is the base class for unary integral cast operator classes. 121 class SCEVIntegralCastExpr : public SCEVCastExpr { 122 protected: 123 SCEVIntegralCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, 124 const SCEV *op, Type *ty); 125 126 public: 127 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)128 static bool classof(const SCEV *S) { 129 return S->getSCEVType() == scTruncate || 130 S->getSCEVType() == scZeroExtend || 131 S->getSCEVType() == scSignExtend; 132 } 133 }; 134 135 /// This class represents a truncation of an integer value to a 136 /// smaller integer value. 137 class SCEVTruncateExpr : public SCEVIntegralCastExpr { 138 friend class ScalarEvolution; 139 140 SCEVTruncateExpr(const FoldingSetNodeIDRef ID, 141 const SCEV *op, Type *ty); 142 143 public: 144 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)145 static bool classof(const SCEV *S) { 146 return S->getSCEVType() == scTruncate; 147 } 148 }; 149 150 /// This class represents a zero extension of a small integer value 151 /// to a larger integer value. 152 class SCEVZeroExtendExpr : public SCEVIntegralCastExpr { 153 friend class ScalarEvolution; 154 155 SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID, 156 const SCEV *op, Type *ty); 157 158 public: 159 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)160 static bool classof(const SCEV *S) { 161 return S->getSCEVType() == scZeroExtend; 162 } 163 }; 164 165 /// This class represents a sign extension of a small integer value 166 /// to a larger integer value. 167 class SCEVSignExtendExpr : public SCEVIntegralCastExpr { 168 friend class ScalarEvolution; 169 170 SCEVSignExtendExpr(const FoldingSetNodeIDRef ID, 171 const SCEV *op, Type *ty); 172 173 public: 174 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)175 static bool classof(const SCEV *S) { 176 return S->getSCEVType() == scSignExtend; 177 } 178 }; 179 180 /// This node is a base class providing common functionality for 181 /// n'ary operators. 182 class SCEVNAryExpr : public SCEV { 183 protected: 184 // Since SCEVs are immutable, ScalarEvolution allocates operand 185 // arrays with its SCEVAllocator, so this class just needs a simple 186 // pointer rather than a more elaborate vector-like data structure. 187 // This also avoids the need for a non-trivial destructor. 188 const SCEV *const *Operands; 189 size_t NumOperands; 190 SCEVNAryExpr(const FoldingSetNodeIDRef ID,enum SCEVTypes T,const SCEV * const * O,size_t N)191 SCEVNAryExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T, 192 const SCEV *const *O, size_t N) 193 : SCEV(ID, T, computeExpressionSize(makeArrayRef(O, N))), Operands(O), 194 NumOperands(N) {} 195 196 public: getNumOperands()197 size_t getNumOperands() const { return NumOperands; } 198 getOperand(unsigned i)199 const SCEV *getOperand(unsigned i) const { 200 assert(i < NumOperands && "Operand index out of range!"); 201 return Operands[i]; 202 } 203 204 using op_iterator = const SCEV *const *; 205 using op_range = iterator_range<op_iterator>; 206 op_begin()207 op_iterator op_begin() const { return Operands; } op_end()208 op_iterator op_end() const { return Operands + NumOperands; } operands()209 op_range operands() const { 210 return make_range(op_begin(), op_end()); 211 } 212 213 NoWrapFlags getNoWrapFlags(NoWrapFlags Mask = NoWrapMask) const { 214 return (NoWrapFlags)(SubclassData & Mask); 215 } 216 hasNoUnsignedWrap()217 bool hasNoUnsignedWrap() const { 218 return getNoWrapFlags(FlagNUW) != FlagAnyWrap; 219 } 220 hasNoSignedWrap()221 bool hasNoSignedWrap() const { 222 return getNoWrapFlags(FlagNSW) != FlagAnyWrap; 223 } 224 hasNoSelfWrap()225 bool hasNoSelfWrap() const { 226 return getNoWrapFlags(FlagNW) != FlagAnyWrap; 227 } 228 229 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)230 static bool classof(const SCEV *S) { 231 return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr || 232 S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr || 233 S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr || 234 S->getSCEVType() == scAddRecExpr; 235 } 236 }; 237 238 /// This node is the base class for n'ary commutative operators. 239 class SCEVCommutativeExpr : public SCEVNAryExpr { 240 protected: SCEVCommutativeExpr(const FoldingSetNodeIDRef ID,enum SCEVTypes T,const SCEV * const * O,size_t N)241 SCEVCommutativeExpr(const FoldingSetNodeIDRef ID, 242 enum SCEVTypes T, const SCEV *const *O, size_t N) 243 : SCEVNAryExpr(ID, T, O, N) {} 244 245 public: 246 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)247 static bool classof(const SCEV *S) { 248 return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr || 249 S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr || 250 S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr; 251 } 252 253 /// Set flags for a non-recurrence without clearing previously set flags. setNoWrapFlags(NoWrapFlags Flags)254 void setNoWrapFlags(NoWrapFlags Flags) { 255 SubclassData |= Flags; 256 } 257 }; 258 259 /// This node represents an addition of some number of SCEVs. 260 class SCEVAddExpr : public SCEVCommutativeExpr { 261 friend class ScalarEvolution; 262 263 Type *Ty; 264 SCEVAddExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)265 SCEVAddExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N) 266 : SCEVCommutativeExpr(ID, scAddExpr, O, N) { 267 auto *FirstPointerTypedOp = find_if(operands(), [](const SCEV *Op) { 268 return Op->getType()->isPointerTy(); 269 }); 270 if (FirstPointerTypedOp != operands().end()) 271 Ty = (*FirstPointerTypedOp)->getType(); 272 else 273 Ty = getOperand(0)->getType(); 274 } 275 276 public: getType()277 Type *getType() const { return Ty; } 278 279 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)280 static bool classof(const SCEV *S) { 281 return S->getSCEVType() == scAddExpr; 282 } 283 }; 284 285 /// This node represents multiplication of some number of SCEVs. 286 class SCEVMulExpr : public SCEVCommutativeExpr { 287 friend class ScalarEvolution; 288 SCEVMulExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)289 SCEVMulExpr(const FoldingSetNodeIDRef ID, 290 const SCEV *const *O, size_t N) 291 : SCEVCommutativeExpr(ID, scMulExpr, O, N) {} 292 293 public: getType()294 Type *getType() const { return getOperand(0)->getType(); } 295 296 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)297 static bool classof(const SCEV *S) { 298 return S->getSCEVType() == scMulExpr; 299 } 300 }; 301 302 /// This class represents a binary unsigned division operation. 303 class SCEVUDivExpr : public SCEV { 304 friend class ScalarEvolution; 305 306 std::array<const SCEV *, 2> Operands; 307 SCEVUDivExpr(const FoldingSetNodeIDRef ID,const SCEV * lhs,const SCEV * rhs)308 SCEVUDivExpr(const FoldingSetNodeIDRef ID, const SCEV *lhs, const SCEV *rhs) 309 : SCEV(ID, scUDivExpr, computeExpressionSize({lhs, rhs})) { 310 Operands[0] = lhs; 311 Operands[1] = rhs; 312 } 313 314 public: getLHS()315 const SCEV *getLHS() const { return Operands[0]; } getRHS()316 const SCEV *getRHS() const { return Operands[1]; } getNumOperands()317 size_t getNumOperands() const { return 2; } getOperand(unsigned i)318 const SCEV *getOperand(unsigned i) const { 319 assert((i == 0 || i == 1) && "Operand index out of range!"); 320 return i == 0 ? getLHS() : getRHS(); 321 } 322 323 using op_iterator = std::array<const SCEV *, 2>::const_iterator; 324 using op_range = iterator_range<op_iterator>; operands()325 op_range operands() const { 326 return make_range(Operands.begin(), Operands.end()); 327 } 328 getType()329 Type *getType() const { 330 // In most cases the types of LHS and RHS will be the same, but in some 331 // crazy cases one or the other may be a pointer. ScalarEvolution doesn't 332 // depend on the type for correctness, but handling types carefully can 333 // avoid extra casts in the SCEVExpander. The LHS is more likely to be 334 // a pointer type than the RHS, so use the RHS' type here. 335 return getRHS()->getType(); 336 } 337 338 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)339 static bool classof(const SCEV *S) { 340 return S->getSCEVType() == scUDivExpr; 341 } 342 }; 343 344 /// This node represents a polynomial recurrence on the trip count 345 /// of the specified loop. This is the primary focus of the 346 /// ScalarEvolution framework; all the other SCEV subclasses are 347 /// mostly just supporting infrastructure to allow SCEVAddRecExpr 348 /// expressions to be created and analyzed. 349 /// 350 /// All operands of an AddRec are required to be loop invariant. 351 /// 352 class SCEVAddRecExpr : public SCEVNAryExpr { 353 friend class ScalarEvolution; 354 355 const Loop *L; 356 SCEVAddRecExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N,const Loop * l)357 SCEVAddRecExpr(const FoldingSetNodeIDRef ID, 358 const SCEV *const *O, size_t N, const Loop *l) 359 : SCEVNAryExpr(ID, scAddRecExpr, O, N), L(l) {} 360 361 public: getType()362 Type *getType() const { return getStart()->getType(); } getStart()363 const SCEV *getStart() const { return Operands[0]; } getLoop()364 const Loop *getLoop() const { return L; } 365 366 /// Constructs and returns the recurrence indicating how much this 367 /// expression steps by. If this is a polynomial of degree N, it 368 /// returns a chrec of degree N-1. We cannot determine whether 369 /// the step recurrence has self-wraparound. getStepRecurrence(ScalarEvolution & SE)370 const SCEV *getStepRecurrence(ScalarEvolution &SE) const { 371 if (isAffine()) return getOperand(1); 372 return SE.getAddRecExpr(SmallVector<const SCEV *, 3>(op_begin()+1, 373 op_end()), 374 getLoop(), FlagAnyWrap); 375 } 376 377 /// Return true if this represents an expression A + B*x where A 378 /// and B are loop invariant values. isAffine()379 bool isAffine() const { 380 // We know that the start value is invariant. This expression is thus 381 // affine iff the step is also invariant. 382 return getNumOperands() == 2; 383 } 384 385 /// Return true if this represents an expression A + B*x + C*x^2 386 /// where A, B and C are loop invariant values. This corresponds 387 /// to an addrec of the form {L,+,M,+,N} isQuadratic()388 bool isQuadratic() const { 389 return getNumOperands() == 3; 390 } 391 392 /// Set flags for a recurrence without clearing any previously set flags. 393 /// For AddRec, either NUW or NSW implies NW. Keep track of this fact here 394 /// to make it easier to propagate flags. setNoWrapFlags(NoWrapFlags Flags)395 void setNoWrapFlags(NoWrapFlags Flags) { 396 if (Flags & (FlagNUW | FlagNSW)) 397 Flags = ScalarEvolution::setFlags(Flags, FlagNW); 398 SubclassData |= Flags; 399 } 400 401 /// Return the value of this chain of recurrences at the specified 402 /// iteration number. 403 const SCEV *evaluateAtIteration(const SCEV *It, ScalarEvolution &SE) const; 404 405 /// Return the value of this chain of recurrences at the specified iteration 406 /// number. Takes an explicit list of operands to represent an AddRec. 407 static const SCEV *evaluateAtIteration(ArrayRef<const SCEV *> Operands, 408 const SCEV *It, ScalarEvolution &SE); 409 410 /// Return the number of iterations of this loop that produce 411 /// values in the specified constant range. Another way of 412 /// looking at this is that it returns the first iteration number 413 /// where the value is not in the condition, thus computing the 414 /// exit count. If the iteration count can't be computed, an 415 /// instance of SCEVCouldNotCompute is returned. 416 const SCEV *getNumIterationsInRange(const ConstantRange &Range, 417 ScalarEvolution &SE) const; 418 419 /// Return an expression representing the value of this expression 420 /// one iteration of the loop ahead. 421 const SCEVAddRecExpr *getPostIncExpr(ScalarEvolution &SE) const; 422 423 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)424 static bool classof(const SCEV *S) { 425 return S->getSCEVType() == scAddRecExpr; 426 } 427 }; 428 429 /// This node is the base class min/max selections. 430 class SCEVMinMaxExpr : public SCEVCommutativeExpr { 431 friend class ScalarEvolution; 432 isMinMaxType(enum SCEVTypes T)433 static bool isMinMaxType(enum SCEVTypes T) { 434 return T == scSMaxExpr || T == scUMaxExpr || T == scSMinExpr || 435 T == scUMinExpr; 436 } 437 438 protected: 439 /// Note: Constructing subclasses via this constructor is allowed SCEVMinMaxExpr(const FoldingSetNodeIDRef ID,enum SCEVTypes T,const SCEV * const * O,size_t N)440 SCEVMinMaxExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T, 441 const SCEV *const *O, size_t N) 442 : SCEVCommutativeExpr(ID, T, O, N) { 443 assert(isMinMaxType(T)); 444 // Min and max never overflow 445 setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)); 446 } 447 448 public: getType()449 Type *getType() const { return getOperand(0)->getType(); } 450 classof(const SCEV * S)451 static bool classof(const SCEV *S) { 452 return isMinMaxType(S->getSCEVType()); 453 } 454 negate(enum SCEVTypes T)455 static enum SCEVTypes negate(enum SCEVTypes T) { 456 switch (T) { 457 case scSMaxExpr: 458 return scSMinExpr; 459 case scSMinExpr: 460 return scSMaxExpr; 461 case scUMaxExpr: 462 return scUMinExpr; 463 case scUMinExpr: 464 return scUMaxExpr; 465 default: 466 llvm_unreachable("Not a min or max SCEV type!"); 467 } 468 } 469 }; 470 471 /// This class represents a signed maximum selection. 472 class SCEVSMaxExpr : public SCEVMinMaxExpr { 473 friend class ScalarEvolution; 474 SCEVSMaxExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)475 SCEVSMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N) 476 : SCEVMinMaxExpr(ID, scSMaxExpr, O, N) {} 477 478 public: 479 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)480 static bool classof(const SCEV *S) { 481 return S->getSCEVType() == scSMaxExpr; 482 } 483 }; 484 485 /// This class represents an unsigned maximum selection. 486 class SCEVUMaxExpr : public SCEVMinMaxExpr { 487 friend class ScalarEvolution; 488 SCEVUMaxExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)489 SCEVUMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N) 490 : SCEVMinMaxExpr(ID, scUMaxExpr, O, N) {} 491 492 public: 493 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)494 static bool classof(const SCEV *S) { 495 return S->getSCEVType() == scUMaxExpr; 496 } 497 }; 498 499 /// This class represents a signed minimum selection. 500 class SCEVSMinExpr : public SCEVMinMaxExpr { 501 friend class ScalarEvolution; 502 SCEVSMinExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)503 SCEVSMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N) 504 : SCEVMinMaxExpr(ID, scSMinExpr, O, N) {} 505 506 public: 507 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)508 static bool classof(const SCEV *S) { 509 return S->getSCEVType() == scSMinExpr; 510 } 511 }; 512 513 /// This class represents an unsigned minimum selection. 514 class SCEVUMinExpr : public SCEVMinMaxExpr { 515 friend class ScalarEvolution; 516 SCEVUMinExpr(const FoldingSetNodeIDRef ID,const SCEV * const * O,size_t N)517 SCEVUMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N) 518 : SCEVMinMaxExpr(ID, scUMinExpr, O, N) {} 519 520 public: 521 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)522 static bool classof(const SCEV *S) { 523 return S->getSCEVType() == scUMinExpr; 524 } 525 }; 526 527 /// This means that we are dealing with an entirely unknown SCEV 528 /// value, and only represent it as its LLVM Value. This is the 529 /// "bottom" value for the analysis. 530 class SCEVUnknown final : public SCEV, private CallbackVH { 531 friend class ScalarEvolution; 532 533 /// The parent ScalarEvolution value. This is used to update the 534 /// parent's maps when the value associated with a SCEVUnknown is 535 /// deleted or RAUW'd. 536 ScalarEvolution *SE; 537 538 /// The next pointer in the linked list of all SCEVUnknown 539 /// instances owned by a ScalarEvolution. 540 SCEVUnknown *Next; 541 SCEVUnknown(const FoldingSetNodeIDRef ID,Value * V,ScalarEvolution * se,SCEVUnknown * next)542 SCEVUnknown(const FoldingSetNodeIDRef ID, Value *V, 543 ScalarEvolution *se, SCEVUnknown *next) : 544 SCEV(ID, scUnknown, 1), CallbackVH(V), SE(se), Next(next) {} 545 546 // Implement CallbackVH. 547 void deleted() override; 548 void allUsesReplacedWith(Value *New) override; 549 550 public: getValue()551 Value *getValue() const { return getValPtr(); } 552 553 /// @{ 554 /// Test whether this is a special constant representing a type 555 /// size, alignment, or field offset in a target-independent 556 /// manner, and hasn't happened to have been folded with other 557 /// operations into something unrecognizable. This is mainly only 558 /// useful for pretty-printing and other situations where it isn't 559 /// absolutely required for these to succeed. 560 bool isSizeOf(Type *&AllocTy) const; 561 bool isAlignOf(Type *&AllocTy) const; 562 bool isOffsetOf(Type *&STy, Constant *&FieldNo) const; 563 /// @} 564 getType()565 Type *getType() const { return getValPtr()->getType(); } 566 567 /// Methods for support type inquiry through isa, cast, and dyn_cast: classof(const SCEV * S)568 static bool classof(const SCEV *S) { 569 return S->getSCEVType() == scUnknown; 570 } 571 }; 572 573 /// This class defines a simple visitor class that may be used for 574 /// various SCEV analysis purposes. 575 template<typename SC, typename RetVal=void> 576 struct SCEVVisitor { visitSCEVVisitor577 RetVal visit(const SCEV *S) { 578 switch (S->getSCEVType()) { 579 case scConstant: 580 return ((SC*)this)->visitConstant((const SCEVConstant*)S); 581 case scPtrToInt: 582 return ((SC *)this)->visitPtrToIntExpr((const SCEVPtrToIntExpr *)S); 583 case scTruncate: 584 return ((SC*)this)->visitTruncateExpr((const SCEVTruncateExpr*)S); 585 case scZeroExtend: 586 return ((SC*)this)->visitZeroExtendExpr((const SCEVZeroExtendExpr*)S); 587 case scSignExtend: 588 return ((SC*)this)->visitSignExtendExpr((const SCEVSignExtendExpr*)S); 589 case scAddExpr: 590 return ((SC*)this)->visitAddExpr((const SCEVAddExpr*)S); 591 case scMulExpr: 592 return ((SC*)this)->visitMulExpr((const SCEVMulExpr*)S); 593 case scUDivExpr: 594 return ((SC*)this)->visitUDivExpr((const SCEVUDivExpr*)S); 595 case scAddRecExpr: 596 return ((SC*)this)->visitAddRecExpr((const SCEVAddRecExpr*)S); 597 case scSMaxExpr: 598 return ((SC*)this)->visitSMaxExpr((const SCEVSMaxExpr*)S); 599 case scUMaxExpr: 600 return ((SC*)this)->visitUMaxExpr((const SCEVUMaxExpr*)S); 601 case scSMinExpr: 602 return ((SC *)this)->visitSMinExpr((const SCEVSMinExpr *)S); 603 case scUMinExpr: 604 return ((SC *)this)->visitUMinExpr((const SCEVUMinExpr *)S); 605 case scUnknown: 606 return ((SC*)this)->visitUnknown((const SCEVUnknown*)S); 607 case scCouldNotCompute: 608 return ((SC*)this)->visitCouldNotCompute((const SCEVCouldNotCompute*)S); 609 } 610 llvm_unreachable("Unknown SCEV kind!"); 611 } 612 visitCouldNotComputeSCEVVisitor613 RetVal visitCouldNotCompute(const SCEVCouldNotCompute *S) { 614 llvm_unreachable("Invalid use of SCEVCouldNotCompute!"); 615 } 616 }; 617 618 /// Visit all nodes in the expression tree using worklist traversal. 619 /// 620 /// Visitor implements: 621 /// // return true to follow this node. 622 /// bool follow(const SCEV *S); 623 /// // return true to terminate the search. 624 /// bool isDone(); 625 template<typename SV> 626 class SCEVTraversal { 627 SV &Visitor; 628 SmallVector<const SCEV *, 8> Worklist; 629 SmallPtrSet<const SCEV *, 8> Visited; 630 push(const SCEV * S)631 void push(const SCEV *S) { 632 if (Visited.insert(S).second && Visitor.follow(S)) 633 Worklist.push_back(S); 634 } 635 636 public: SCEVTraversal(SV & V)637 SCEVTraversal(SV& V): Visitor(V) {} 638 visitAll(const SCEV * Root)639 void visitAll(const SCEV *Root) { 640 push(Root); 641 while (!Worklist.empty() && !Visitor.isDone()) { 642 const SCEV *S = Worklist.pop_back_val(); 643 644 switch (S->getSCEVType()) { 645 case scConstant: 646 case scUnknown: 647 continue; 648 case scPtrToInt: 649 case scTruncate: 650 case scZeroExtend: 651 case scSignExtend: 652 push(cast<SCEVCastExpr>(S)->getOperand()); 653 continue; 654 case scAddExpr: 655 case scMulExpr: 656 case scSMaxExpr: 657 case scUMaxExpr: 658 case scSMinExpr: 659 case scUMinExpr: 660 case scAddRecExpr: 661 for (const auto *Op : cast<SCEVNAryExpr>(S)->operands()) 662 push(Op); 663 continue; 664 case scUDivExpr: { 665 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S); 666 push(UDiv->getLHS()); 667 push(UDiv->getRHS()); 668 continue; 669 } 670 case scCouldNotCompute: 671 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!"); 672 } 673 llvm_unreachable("Unknown SCEV kind!"); 674 } 675 } 676 }; 677 678 /// Use SCEVTraversal to visit all nodes in the given expression tree. 679 template<typename SV> visitAll(const SCEV * Root,SV & Visitor)680 void visitAll(const SCEV *Root, SV& Visitor) { 681 SCEVTraversal<SV> T(Visitor); 682 T.visitAll(Root); 683 } 684 685 /// Return true if any node in \p Root satisfies the predicate \p Pred. 686 template <typename PredTy> SCEVExprContains(const SCEV * Root,PredTy Pred)687 bool SCEVExprContains(const SCEV *Root, PredTy Pred) { 688 struct FindClosure { 689 bool Found = false; 690 PredTy Pred; 691 692 FindClosure(PredTy Pred) : Pred(Pred) {} 693 694 bool follow(const SCEV *S) { 695 if (!Pred(S)) 696 return true; 697 698 Found = true; 699 return false; 700 } 701 702 bool isDone() const { return Found; } 703 }; 704 705 FindClosure FC(Pred); 706 visitAll(Root, FC); 707 return FC.Found; 708 } 709 710 /// This visitor recursively visits a SCEV expression and re-writes it. 711 /// The result from each visit is cached, so it will return the same 712 /// SCEV for the same input. 713 template<typename SC> 714 class SCEVRewriteVisitor : public SCEVVisitor<SC, const SCEV *> { 715 protected: 716 ScalarEvolution &SE; 717 // Memoize the result of each visit so that we only compute once for 718 // the same input SCEV. This is to avoid redundant computations when 719 // a SCEV is referenced by multiple SCEVs. Without memoization, this 720 // visit algorithm would have exponential time complexity in the worst 721 // case, causing the compiler to hang on certain tests. 722 DenseMap<const SCEV *, const SCEV *> RewriteResults; 723 724 public: SCEVRewriteVisitor(ScalarEvolution & SE)725 SCEVRewriteVisitor(ScalarEvolution &SE) : SE(SE) {} 726 visit(const SCEV * S)727 const SCEV *visit(const SCEV *S) { 728 auto It = RewriteResults.find(S); 729 if (It != RewriteResults.end()) 730 return It->second; 731 auto* Visited = SCEVVisitor<SC, const SCEV *>::visit(S); 732 auto Result = RewriteResults.try_emplace(S, Visited); 733 assert(Result.second && "Should insert a new entry"); 734 return Result.first->second; 735 } 736 visitConstant(const SCEVConstant * Constant)737 const SCEV *visitConstant(const SCEVConstant *Constant) { 738 return Constant; 739 } 740 visitPtrToIntExpr(const SCEVPtrToIntExpr * Expr)741 const SCEV *visitPtrToIntExpr(const SCEVPtrToIntExpr *Expr) { 742 const SCEV *Operand = ((SC *)this)->visit(Expr->getOperand()); 743 return Operand == Expr->getOperand() 744 ? Expr 745 : SE.getPtrToIntExpr(Operand, Expr->getType()); 746 } 747 visitTruncateExpr(const SCEVTruncateExpr * Expr)748 const SCEV *visitTruncateExpr(const SCEVTruncateExpr *Expr) { 749 const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand()); 750 return Operand == Expr->getOperand() 751 ? Expr 752 : SE.getTruncateExpr(Operand, Expr->getType()); 753 } 754 visitZeroExtendExpr(const SCEVZeroExtendExpr * Expr)755 const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) { 756 const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand()); 757 return Operand == Expr->getOperand() 758 ? Expr 759 : SE.getZeroExtendExpr(Operand, Expr->getType()); 760 } 761 visitSignExtendExpr(const SCEVSignExtendExpr * Expr)762 const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) { 763 const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand()); 764 return Operand == Expr->getOperand() 765 ? Expr 766 : SE.getSignExtendExpr(Operand, Expr->getType()); 767 } 768 visitAddExpr(const SCEVAddExpr * Expr)769 const SCEV *visitAddExpr(const SCEVAddExpr *Expr) { 770 SmallVector<const SCEV *, 2> Operands; 771 bool Changed = false; 772 for (auto *Op : Expr->operands()) { 773 Operands.push_back(((SC*)this)->visit(Op)); 774 Changed |= Op != Operands.back(); 775 } 776 return !Changed ? Expr : SE.getAddExpr(Operands); 777 } 778 visitMulExpr(const SCEVMulExpr * Expr)779 const SCEV *visitMulExpr(const SCEVMulExpr *Expr) { 780 SmallVector<const SCEV *, 2> Operands; 781 bool Changed = false; 782 for (auto *Op : Expr->operands()) { 783 Operands.push_back(((SC*)this)->visit(Op)); 784 Changed |= Op != Operands.back(); 785 } 786 return !Changed ? Expr : SE.getMulExpr(Operands); 787 } 788 visitUDivExpr(const SCEVUDivExpr * Expr)789 const SCEV *visitUDivExpr(const SCEVUDivExpr *Expr) { 790 auto *LHS = ((SC *)this)->visit(Expr->getLHS()); 791 auto *RHS = ((SC *)this)->visit(Expr->getRHS()); 792 bool Changed = LHS != Expr->getLHS() || RHS != Expr->getRHS(); 793 return !Changed ? Expr : SE.getUDivExpr(LHS, RHS); 794 } 795 visitAddRecExpr(const SCEVAddRecExpr * Expr)796 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { 797 SmallVector<const SCEV *, 2> Operands; 798 bool Changed = false; 799 for (auto *Op : Expr->operands()) { 800 Operands.push_back(((SC*)this)->visit(Op)); 801 Changed |= Op != Operands.back(); 802 } 803 return !Changed ? Expr 804 : SE.getAddRecExpr(Operands, Expr->getLoop(), 805 Expr->getNoWrapFlags()); 806 } 807 visitSMaxExpr(const SCEVSMaxExpr * Expr)808 const SCEV *visitSMaxExpr(const SCEVSMaxExpr *Expr) { 809 SmallVector<const SCEV *, 2> Operands; 810 bool Changed = false; 811 for (auto *Op : Expr->operands()) { 812 Operands.push_back(((SC *)this)->visit(Op)); 813 Changed |= Op != Operands.back(); 814 } 815 return !Changed ? Expr : SE.getSMaxExpr(Operands); 816 } 817 visitUMaxExpr(const SCEVUMaxExpr * Expr)818 const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) { 819 SmallVector<const SCEV *, 2> Operands; 820 bool Changed = false; 821 for (auto *Op : Expr->operands()) { 822 Operands.push_back(((SC*)this)->visit(Op)); 823 Changed |= Op != Operands.back(); 824 } 825 return !Changed ? Expr : SE.getUMaxExpr(Operands); 826 } 827 visitSMinExpr(const SCEVSMinExpr * Expr)828 const SCEV *visitSMinExpr(const SCEVSMinExpr *Expr) { 829 SmallVector<const SCEV *, 2> Operands; 830 bool Changed = false; 831 for (auto *Op : Expr->operands()) { 832 Operands.push_back(((SC *)this)->visit(Op)); 833 Changed |= Op != Operands.back(); 834 } 835 return !Changed ? Expr : SE.getSMinExpr(Operands); 836 } 837 visitUMinExpr(const SCEVUMinExpr * Expr)838 const SCEV *visitUMinExpr(const SCEVUMinExpr *Expr) { 839 SmallVector<const SCEV *, 2> Operands; 840 bool Changed = false; 841 for (auto *Op : Expr->operands()) { 842 Operands.push_back(((SC *)this)->visit(Op)); 843 Changed |= Op != Operands.back(); 844 } 845 return !Changed ? Expr : SE.getUMinExpr(Operands); 846 } 847 visitUnknown(const SCEVUnknown * Expr)848 const SCEV *visitUnknown(const SCEVUnknown *Expr) { 849 return Expr; 850 } 851 visitCouldNotCompute(const SCEVCouldNotCompute * Expr)852 const SCEV *visitCouldNotCompute(const SCEVCouldNotCompute *Expr) { 853 return Expr; 854 } 855 }; 856 857 using ValueToValueMap = DenseMap<const Value *, Value *>; 858 using ValueToSCEVMapTy = DenseMap<const Value *, const SCEV *>; 859 860 /// The SCEVParameterRewriter takes a scalar evolution expression and updates 861 /// the SCEVUnknown components following the Map (Value -> SCEV). 862 class SCEVParameterRewriter : public SCEVRewriteVisitor<SCEVParameterRewriter> { 863 public: rewrite(const SCEV * Scev,ScalarEvolution & SE,ValueToSCEVMapTy & Map)864 static const SCEV *rewrite(const SCEV *Scev, ScalarEvolution &SE, 865 ValueToSCEVMapTy &Map) { 866 SCEVParameterRewriter Rewriter(SE, Map); 867 return Rewriter.visit(Scev); 868 } 869 SCEVParameterRewriter(ScalarEvolution & SE,ValueToSCEVMapTy & M)870 SCEVParameterRewriter(ScalarEvolution &SE, ValueToSCEVMapTy &M) 871 : SCEVRewriteVisitor(SE), Map(M) {} 872 visitUnknown(const SCEVUnknown * Expr)873 const SCEV *visitUnknown(const SCEVUnknown *Expr) { 874 auto I = Map.find(Expr->getValue()); 875 if (I == Map.end()) 876 return Expr; 877 return I->second; 878 } 879 880 private: 881 ValueToSCEVMapTy ⤅ 882 }; 883 884 using LoopToScevMapT = DenseMap<const Loop *, const SCEV *>; 885 886 /// The SCEVLoopAddRecRewriter takes a scalar evolution expression and applies 887 /// the Map (Loop -> SCEV) to all AddRecExprs. 888 class SCEVLoopAddRecRewriter 889 : public SCEVRewriteVisitor<SCEVLoopAddRecRewriter> { 890 public: SCEVLoopAddRecRewriter(ScalarEvolution & SE,LoopToScevMapT & M)891 SCEVLoopAddRecRewriter(ScalarEvolution &SE, LoopToScevMapT &M) 892 : SCEVRewriteVisitor(SE), Map(M) {} 893 rewrite(const SCEV * Scev,LoopToScevMapT & Map,ScalarEvolution & SE)894 static const SCEV *rewrite(const SCEV *Scev, LoopToScevMapT &Map, 895 ScalarEvolution &SE) { 896 SCEVLoopAddRecRewriter Rewriter(SE, Map); 897 return Rewriter.visit(Scev); 898 } 899 visitAddRecExpr(const SCEVAddRecExpr * Expr)900 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) { 901 SmallVector<const SCEV *, 2> Operands; 902 for (const SCEV *Op : Expr->operands()) 903 Operands.push_back(visit(Op)); 904 905 const Loop *L = Expr->getLoop(); 906 if (0 == Map.count(L)) 907 return SE.getAddRecExpr(Operands, L, Expr->getNoWrapFlags()); 908 909 return SCEVAddRecExpr::evaluateAtIteration(Operands, Map[L], SE); 910 } 911 912 private: 913 LoopToScevMapT ⤅ 914 }; 915 916 } // end namespace llvm 917 918 #endif // LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H 919