1 //===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- 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 // The ScalarEvolution class is an LLVM pass which can be used to analyze and 11 // categorize scalar expressions in loops. It specializes in recognizing 12 // general induction variables, representing them with the abstract and opaque 13 // SCEV class. Given this analysis, trip counts of loops and other important 14 // properties can be obtained. 15 // 16 // This analysis is primarily useful for induction variable substitution and 17 // strength reduction. 18 // 19 //===----------------------------------------------------------------------===// 20 21 #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H 22 #define LLVM_ANALYSIS_SCALAREVOLUTION_H 23 24 #include "llvm/Pass.h" 25 #include "llvm/Instructions.h" 26 #include "llvm/Function.h" 27 #include "llvm/Operator.h" 28 #include "llvm/Support/DataTypes.h" 29 #include "llvm/Support/ValueHandle.h" 30 #include "llvm/Support/Allocator.h" 31 #include "llvm/Support/ConstantRange.h" 32 #include "llvm/ADT/FoldingSet.h" 33 #include "llvm/ADT/DenseMap.h" 34 #include <map> 35 36 namespace llvm { 37 class APInt; 38 class Constant; 39 class ConstantInt; 40 class DominatorTree; 41 class Type; 42 class ScalarEvolution; 43 class TargetData; 44 class LLVMContext; 45 class Loop; 46 class LoopInfo; 47 class Operator; 48 class SCEVUnknown; 49 class SCEV; 50 template<> struct FoldingSetTrait<SCEV>; 51 52 /// SCEV - This class represents an analyzed expression in the program. These 53 /// are opaque objects that the client is not allowed to do much with 54 /// directly. 55 /// 56 class SCEV : public FoldingSetNode { 57 friend struct FoldingSetTrait<SCEV>; 58 59 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 60 /// The ScalarEvolution's BumpPtrAllocator holds the data. 61 FoldingSetNodeIDRef FastID; 62 63 // The SCEV baseclass this node corresponds to 64 const unsigned short SCEVType; 65 66 protected: 67 /// SubclassData - This field is initialized to zero and may be used in 68 /// subclasses to store miscellaneous information. 69 unsigned short SubclassData; 70 71 private: 72 SCEV(const SCEV &); // DO NOT IMPLEMENT 73 void operator=(const SCEV &); // DO NOT IMPLEMENT 74 75 public: 76 /// NoWrapFlags are bitfield indices into SubclassData. 77 /// 78 /// Add and Mul expressions may have no-unsigned-wrap <NUW> or 79 /// no-signed-wrap <NSW> properties, which are derived from the IR 80 /// operator. NSW is a misnomer that we use to mean no signed overflow or 81 /// underflow. 82 /// 83 /// AddRec expression may have a no-self-wraparound <NW> property if the 84 /// result can never reach the start value. This property is independent of 85 /// the actual start value and step direction. Self-wraparound is defined 86 /// purely in terms of the recurrence's loop, step size, and 87 /// bitwidth. Formally, a recurrence with no self-wraparound satisfies: 88 /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth). 89 /// 90 /// Note that NUW and NSW are also valid properties of a recurrence, and 91 /// either implies NW. For convenience, NW will be set for a recurrence 92 /// whenever either NUW or NSW are set. 93 enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee. 94 FlagNW = (1 << 0), // No self-wrap. 95 FlagNUW = (1 << 1), // No unsigned wrap. 96 FlagNSW = (1 << 2), // No signed wrap. 97 NoWrapMask = (1 << 3) -1 }; 98 99 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 100 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 101 102 unsigned getSCEVType() const { return SCEVType; } 103 104 /// getType - Return the LLVM type of this SCEV expression. 105 /// 106 Type *getType() const; 107 108 /// isZero - Return true if the expression is a constant zero. 109 /// 110 bool isZero() const; 111 112 /// isOne - Return true if the expression is a constant one. 113 /// 114 bool isOne() const; 115 116 /// isAllOnesValue - Return true if the expression is a constant 117 /// all-ones value. 118 /// 119 bool isAllOnesValue() const; 120 121 /// print - Print out the internal representation of this scalar to the 122 /// specified stream. This should really only be used for debugging 123 /// purposes. 124 void print(raw_ostream &OS) const; 125 126 /// dump - This method is used for debugging. 127 /// 128 void dump() const; 129 }; 130 131 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 132 // temporary FoldingSetNodeID values. 133 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 134 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 135 ID = X.FastID; 136 } 137 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 138 FoldingSetNodeID &TempID) { 139 return ID == X.FastID; 140 } 141 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 142 return X.FastID.ComputeHash(); 143 } 144 }; 145 146 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 147 S.print(OS); 148 return OS; 149 } 150 151 /// SCEVCouldNotCompute - An object of this class is returned by queries that 152 /// could not be answered. For example, if you ask for the number of 153 /// iterations of a linked-list traversal loop, you will get one of these. 154 /// None of the standard SCEV operations are valid on this class, it is just a 155 /// marker. 156 struct SCEVCouldNotCompute : public SCEV { 157 SCEVCouldNotCompute(); 158 159 /// Methods for support type inquiry through isa, cast, and dyn_cast: 160 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 161 static bool classof(const SCEV *S); 162 }; 163 164 /// ScalarEvolution - This class is the main scalar evolution driver. Because 165 /// client code (intentionally) can't do much with the SCEV objects directly, 166 /// they must ask this class for services. 167 /// 168 class ScalarEvolution : public FunctionPass { 169 public: 170 /// LoopDisposition - An enum describing the relationship between a 171 /// SCEV and a loop. 172 enum LoopDisposition { 173 LoopVariant, ///< The SCEV is loop-variant (unknown). 174 LoopInvariant, ///< The SCEV is loop-invariant. 175 LoopComputable ///< The SCEV varies predictably with the loop. 176 }; 177 178 /// BlockDisposition - An enum describing the relationship between a 179 /// SCEV and a basic block. 180 enum BlockDisposition { 181 DoesNotDominateBlock, ///< The SCEV does not dominate the block. 182 DominatesBlock, ///< The SCEV dominates the block. 183 ProperlyDominatesBlock ///< The SCEV properly dominates the block. 184 }; 185 186 /// Convenient NoWrapFlags manipulation that hides enum casts and is 187 /// visible in the ScalarEvolution name space. 188 static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) { 189 return (SCEV::NoWrapFlags)(Flags & Mask); 190 } 191 static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags, 192 SCEV::NoWrapFlags OnFlags) { 193 return (SCEV::NoWrapFlags)(Flags | OnFlags); 194 } 195 static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags, 196 SCEV::NoWrapFlags OffFlags) { 197 return (SCEV::NoWrapFlags)(Flags & ~OffFlags); 198 } 199 200 private: 201 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 202 /// notified whenever a Value is deleted. 203 class SCEVCallbackVH : public CallbackVH { 204 ScalarEvolution *SE; 205 virtual void deleted(); 206 virtual void allUsesReplacedWith(Value *New); 207 public: 208 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 209 }; 210 211 friend class SCEVCallbackVH; 212 friend class SCEVExpander; 213 friend class SCEVUnknown; 214 215 /// F - The function we are analyzing. 216 /// 217 Function *F; 218 219 /// LI - The loop information for the function we are currently analyzing. 220 /// 221 LoopInfo *LI; 222 223 /// TD - The target data information for the target we are targeting. 224 /// 225 TargetData *TD; 226 227 /// DT - The dominator tree. 228 /// 229 DominatorTree *DT; 230 231 /// CouldNotCompute - This SCEV is used to represent unknown trip 232 /// counts and things. 233 SCEVCouldNotCompute CouldNotCompute; 234 235 /// ValueExprMapType - The typedef for ValueExprMap. 236 /// 237 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 238 ValueExprMapType; 239 240 /// ValueExprMap - This is a cache of the values we have analyzed so far. 241 /// 242 ValueExprMapType ValueExprMap; 243 244 /// BackedgeTakenInfo - Information about the backedge-taken count 245 /// of a loop. This currently includes an exact count and a maximum count. 246 /// 247 struct BackedgeTakenInfo { 248 /// Exact - An expression indicating the exact backedge-taken count of 249 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 250 const SCEV *Exact; 251 252 /// Max - An expression indicating the least maximum backedge-taken 253 /// count of the loop that is known, or a SCEVCouldNotCompute. 254 const SCEV *Max; 255 256 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 257 Exact(exact), Max(exact) {} 258 259 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 260 Exact(exact), Max(max) {} 261 262 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 263 /// computed information, or whether it's all SCEVCouldNotCompute 264 /// values. 265 bool hasAnyInfo() const { 266 return !isa<SCEVCouldNotCompute>(Exact) || 267 !isa<SCEVCouldNotCompute>(Max); 268 } 269 }; 270 271 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 272 /// this function as they are computed. 273 DenseMap<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 274 275 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 276 /// the PHI instructions that we attempt to compute constant evolutions for. 277 /// This allows us to avoid potentially expensive recomputation of these 278 /// properties. An instruction maps to null if we are unable to compute its 279 /// exit value. 280 DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 281 282 /// ValuesAtScopes - This map contains entries for all the expressions 283 /// that we attempt to compute getSCEVAtScope information for, which can 284 /// be expensive in extreme cases. 285 DenseMap<const SCEV *, 286 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 287 288 /// LoopDispositions - Memoized computeLoopDisposition results. 289 DenseMap<const SCEV *, 290 std::map<const Loop *, LoopDisposition> > LoopDispositions; 291 292 /// computeLoopDisposition - Compute a LoopDisposition value. 293 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 294 295 /// BlockDispositions - Memoized computeBlockDisposition results. 296 DenseMap<const SCEV *, 297 std::map<const BasicBlock *, BlockDisposition> > BlockDispositions; 298 299 /// computeBlockDisposition - Compute a BlockDisposition value. 300 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB); 301 302 /// UnsignedRanges - Memoized results from getUnsignedRange 303 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 304 305 /// SignedRanges - Memoized results from getSignedRange 306 DenseMap<const SCEV *, ConstantRange> SignedRanges; 307 308 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 309 const ConstantRange &setUnsignedRange(const SCEV *S, 310 const ConstantRange &CR) { 311 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 312 UnsignedRanges.insert(std::make_pair(S, CR)); 313 if (!Pair.second) 314 Pair.first->second = CR; 315 return Pair.first->second; 316 } 317 318 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 319 const ConstantRange &setSignedRange(const SCEV *S, 320 const ConstantRange &CR) { 321 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 322 SignedRanges.insert(std::make_pair(S, CR)); 323 if (!Pair.second) 324 Pair.first->second = CR; 325 return Pair.first->second; 326 } 327 328 /// createSCEV - We know that there is no SCEV for the specified value. 329 /// Analyze the expression. 330 const SCEV *createSCEV(Value *V); 331 332 /// createNodeForPHI - Provide the special handling we need to analyze PHI 333 /// SCEVs. 334 const SCEV *createNodeForPHI(PHINode *PN); 335 336 /// createNodeForGEP - Provide the special handling we need to analyze GEP 337 /// SCEVs. 338 const SCEV *createNodeForGEP(GEPOperator *GEP); 339 340 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 341 /// at most once for each SCEV+Loop pair. 342 /// 343 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 344 345 /// ForgetSymbolicValue - This looks up computed SCEV values for all 346 /// instructions that depend on the given instruction and removes them from 347 /// the ValueExprMap map if they reference SymName. This is used during PHI 348 /// resolution. 349 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 350 351 /// getBECount - Subtract the end and start values and divide by the step, 352 /// rounding up, to get the number of times the backedge is executed. Return 353 /// CouldNotCompute if an intermediate computation overflows. 354 const SCEV *getBECount(const SCEV *Start, 355 const SCEV *End, 356 const SCEV *Step, 357 bool NoWrap); 358 359 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 360 /// loop, lazily computing new values if the loop hasn't been analyzed 361 /// yet. 362 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 363 364 /// ComputeBackedgeTakenCount - Compute the number of times the specified 365 /// loop will iterate. 366 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 367 368 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 369 /// backedge of the specified loop will execute if it exits via the 370 /// specified block. 371 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 372 BasicBlock *ExitingBlock); 373 374 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 375 /// backedge of the specified loop will execute if its exit condition 376 /// were a conditional branch of ExitCond, TBB, and FBB. 377 BackedgeTakenInfo 378 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 379 Value *ExitCond, 380 BasicBlock *TBB, 381 BasicBlock *FBB); 382 383 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 384 /// times the backedge of the specified loop will execute if its exit 385 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 386 /// and FBB. 387 BackedgeTakenInfo 388 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 389 ICmpInst *ExitCond, 390 BasicBlock *TBB, 391 BasicBlock *FBB); 392 393 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 394 /// of 'icmp op load X, cst', try to see if we can compute the 395 /// backedge-taken count. 396 BackedgeTakenInfo 397 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 398 Constant *RHS, 399 const Loop *L, 400 ICmpInst::Predicate p); 401 402 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 403 /// a constant number of times (the condition evolves only from constants), 404 /// try to evaluate a few iterations of the loop until we get the exit 405 /// condition gets a value of ExitWhen (true or false). If we cannot 406 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 407 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 408 Value *Cond, 409 bool ExitWhen); 410 411 /// HowFarToZero - Return the number of times a backedge comparing the 412 /// specified value to zero will execute. If not computable, return 413 /// CouldNotCompute. 414 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 415 416 /// HowFarToNonZero - Return the number of times a backedge checking the 417 /// specified value for nonzero will execute. If not computable, return 418 /// CouldNotCompute. 419 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 420 421 /// HowManyLessThans - Return the number of times a backedge containing the 422 /// specified less-than comparison will execute. If not computable, return 423 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 424 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 425 const Loop *L, bool isSigned); 426 427 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 428 /// (which may not be an immediate predecessor) which has exactly one 429 /// successor from which BB is reachable, or null if no such block is 430 /// found. 431 std::pair<BasicBlock *, BasicBlock *> 432 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 433 434 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 435 /// RHS is true whenever the given FoundCondValue value evaluates to true. 436 bool isImpliedCond(ICmpInst::Predicate Pred, 437 const SCEV *LHS, const SCEV *RHS, 438 Value *FoundCondValue, 439 bool Inverse); 440 441 /// isImpliedCondOperands - Test whether the condition described by Pred, 442 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 443 /// and FoundRHS is true. 444 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 445 const SCEV *LHS, const SCEV *RHS, 446 const SCEV *FoundLHS, const SCEV *FoundRHS); 447 448 /// isImpliedCondOperandsHelper - Test whether the condition described by 449 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 450 /// FoundLHS, and FoundRHS is true. 451 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 452 const SCEV *LHS, const SCEV *RHS, 453 const SCEV *FoundLHS, const SCEV *FoundRHS); 454 455 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 456 /// in the header of its containing loop, we know the loop executes a 457 /// constant number of times, and the PHI node is just a recurrence 458 /// involving constants, fold it. 459 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 460 const Loop *L); 461 462 /// isKnownPredicateWithRanges - Test if the given expression is known to 463 /// satisfy the condition described by Pred and the known constant ranges 464 /// of LHS and RHS. 465 /// 466 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 467 const SCEV *LHS, const SCEV *RHS); 468 469 /// forgetMemoizedResults - Drop memoized information computed for S. 470 void forgetMemoizedResults(const SCEV *S); 471 472 public: 473 static char ID; // Pass identification, replacement for typeid 474 ScalarEvolution(); 475 476 LLVMContext &getContext() const { return F->getContext(); } 477 478 /// isSCEVable - Test if values of the given type are analyzable within 479 /// the SCEV framework. This primarily includes integer types, and it 480 /// can optionally include pointer types if the ScalarEvolution class 481 /// has access to target-specific information. 482 bool isSCEVable(Type *Ty) const; 483 484 /// getTypeSizeInBits - Return the size in bits of the specified type, 485 /// for which isSCEVable must return true. 486 uint64_t getTypeSizeInBits(Type *Ty) const; 487 488 /// getEffectiveSCEVType - Return a type with the same bitwidth as 489 /// the given type and which represents how SCEV will treat the given 490 /// type, for which isSCEVable must return true. For pointer types, 491 /// this is the pointer-sized integer type. 492 Type *getEffectiveSCEVType(Type *Ty) const; 493 494 /// getSCEV - Return a SCEV expression for the full generality of the 495 /// specified expression. 496 const SCEV *getSCEV(Value *V); 497 498 const SCEV *getConstant(ConstantInt *V); 499 const SCEV *getConstant(const APInt& Val); 500 const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false); 501 const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty); 502 const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty); 503 const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty); 504 const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty); 505 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 506 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 507 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 508 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 509 SmallVector<const SCEV *, 2> Ops; 510 Ops.push_back(LHS); 511 Ops.push_back(RHS); 512 return getAddExpr(Ops, Flags); 513 } 514 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 515 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 516 SmallVector<const SCEV *, 3> Ops; 517 Ops.push_back(Op0); 518 Ops.push_back(Op1); 519 Ops.push_back(Op2); 520 return getAddExpr(Ops, Flags); 521 } 522 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 523 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 524 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 525 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) 526 { 527 SmallVector<const SCEV *, 2> Ops; 528 Ops.push_back(LHS); 529 Ops.push_back(RHS); 530 return getMulExpr(Ops, Flags); 531 } 532 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 533 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 534 const Loop *L, SCEV::NoWrapFlags Flags); 535 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 536 const Loop *L, SCEV::NoWrapFlags Flags); 537 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 538 const Loop *L, SCEV::NoWrapFlags Flags) { 539 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 540 return getAddRecExpr(NewOp, L, Flags); 541 } 542 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 543 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 544 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 545 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 546 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 547 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 548 const SCEV *getUnknown(Value *V); 549 const SCEV *getCouldNotCompute(); 550 551 /// getSizeOfExpr - Return an expression for sizeof on the given type. 552 /// 553 const SCEV *getSizeOfExpr(Type *AllocTy); 554 555 /// getAlignOfExpr - Return an expression for alignof on the given type. 556 /// 557 const SCEV *getAlignOfExpr(Type *AllocTy); 558 559 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 560 /// 561 const SCEV *getOffsetOfExpr(StructType *STy, unsigned FieldNo); 562 563 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 564 /// 565 const SCEV *getOffsetOfExpr(Type *CTy, Constant *FieldNo); 566 567 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 568 /// 569 const SCEV *getNegativeSCEV(const SCEV *V); 570 571 /// getNotSCEV - Return the SCEV object corresponding to ~V. 572 /// 573 const SCEV *getNotSCEV(const SCEV *V); 574 575 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1. 576 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS, 577 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 578 579 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 580 /// of the input value to the specified type. If the type must be 581 /// extended, it is zero extended. 582 const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty); 583 584 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 585 /// of the input value to the specified type. If the type must be 586 /// extended, it is sign extended. 587 const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty); 588 589 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 590 /// the input value to the specified type. If the type must be extended, 591 /// it is zero extended. The conversion must not be narrowing. 592 const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty); 593 594 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 595 /// the input value to the specified type. If the type must be extended, 596 /// it is sign extended. The conversion must not be narrowing. 597 const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty); 598 599 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 600 /// the input value to the specified type. If the type must be extended, 601 /// it is extended with unspecified bits. The conversion must not be 602 /// narrowing. 603 const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty); 604 605 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 606 /// input value to the specified type. The conversion must not be 607 /// widening. 608 const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty); 609 610 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 611 /// the types using zero-extension, and then perform a umax operation 612 /// with them. 613 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 614 const SCEV *RHS); 615 616 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 617 /// the types using zero-extension, and then perform a umin operation 618 /// with them. 619 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 620 const SCEV *RHS); 621 622 /// getPointerBase - Transitively follow the chain of pointer-type operands 623 /// until reaching a SCEV that does not have a single pointer operand. This 624 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions, 625 /// but corner cases do exist. 626 const SCEV *getPointerBase(const SCEV *V); 627 628 /// getSCEVAtScope - Return a SCEV expression for the specified value 629 /// at the specified scope in the program. The L value specifies a loop 630 /// nest to evaluate the expression at, where null is the top-level or a 631 /// specified loop is immediately inside of the loop. 632 /// 633 /// This method can be used to compute the exit value for a variable defined 634 /// in a loop by querying what the value will hold in the parent loop. 635 /// 636 /// In the case that a relevant loop exit value cannot be computed, the 637 /// original value V is returned. 638 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 639 640 /// getSCEVAtScope - This is a convenience function which does 641 /// getSCEVAtScope(getSCEV(V), L). 642 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 643 644 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 645 /// by a conditional between LHS and RHS. This is used to help avoid max 646 /// expressions in loop trip counts, and to eliminate casts. 647 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 648 const SCEV *LHS, const SCEV *RHS); 649 650 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 651 /// protected by a conditional between LHS and RHS. This is used to 652 /// to eliminate casts. 653 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 654 const SCEV *LHS, const SCEV *RHS); 655 656 /// getBackedgeTakenCount - If the specified loop has a predictable 657 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 658 /// object. The backedge-taken count is the number of times the loop header 659 /// will be branched to from within the loop. This is one less than the 660 /// trip count of the loop, since it doesn't count the first iteration, 661 /// when the header is branched to from outside the loop. 662 /// 663 /// Note that it is not valid to call this method on a loop without a 664 /// loop-invariant backedge-taken count (see 665 /// hasLoopInvariantBackedgeTakenCount). 666 /// 667 const SCEV *getBackedgeTakenCount(const Loop *L); 668 669 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 670 /// return the least SCEV value that is known never to be less than the 671 /// actual backedge taken count. 672 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 673 674 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 675 /// has an analyzable loop-invariant backedge-taken count. 676 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 677 678 /// forgetLoop - This method should be called by the client when it has 679 /// changed a loop in a way that may effect ScalarEvolution's ability to 680 /// compute a trip count, or if the loop is deleted. 681 void forgetLoop(const Loop *L); 682 683 /// forgetValue - This method should be called by the client when it has 684 /// changed a value in a way that may effect its value, or which may 685 /// disconnect it from a def-use chain linking it to a loop. 686 void forgetValue(Value *V); 687 688 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 689 /// is guaranteed to end in (at every loop iteration). It is, at the same 690 /// time, the minimum number of times S is divisible by 2. For example, 691 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 692 /// bitwidth of S. 693 uint32_t GetMinTrailingZeros(const SCEV *S); 694 695 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 696 /// 697 ConstantRange getUnsignedRange(const SCEV *S); 698 699 /// getSignedRange - Determine the signed range for a particular SCEV. 700 /// 701 ConstantRange getSignedRange(const SCEV *S); 702 703 /// isKnownNegative - Test if the given expression is known to be negative. 704 /// 705 bool isKnownNegative(const SCEV *S); 706 707 /// isKnownPositive - Test if the given expression is known to be positive. 708 /// 709 bool isKnownPositive(const SCEV *S); 710 711 /// isKnownNonNegative - Test if the given expression is known to be 712 /// non-negative. 713 /// 714 bool isKnownNonNegative(const SCEV *S); 715 716 /// isKnownNonPositive - Test if the given expression is known to be 717 /// non-positive. 718 /// 719 bool isKnownNonPositive(const SCEV *S); 720 721 /// isKnownNonZero - Test if the given expression is known to be 722 /// non-zero. 723 /// 724 bool isKnownNonZero(const SCEV *S); 725 726 /// isKnownPredicate - Test if the given expression is known to satisfy 727 /// the condition described by Pred, LHS, and RHS. 728 /// 729 bool isKnownPredicate(ICmpInst::Predicate Pred, 730 const SCEV *LHS, const SCEV *RHS); 731 732 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 733 /// predicate Pred. Return true iff any changes were made. If the 734 /// operands are provably equal or inequal, LHS and RHS are set to 735 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 736 /// 737 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 738 const SCEV *&LHS, 739 const SCEV *&RHS); 740 741 /// getLoopDisposition - Return the "disposition" of the given SCEV with 742 /// respect to the given loop. 743 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 744 745 /// isLoopInvariant - Return true if the value of the given SCEV is 746 /// unchanging in the specified loop. 747 bool isLoopInvariant(const SCEV *S, const Loop *L); 748 749 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 750 /// in a known way in the specified loop. This property being true implies 751 /// that the value is variant in the loop AND that we can emit an expression 752 /// to compute the value of the expression at any particular loop iteration. 753 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 754 755 /// getLoopDisposition - Return the "disposition" of the given SCEV with 756 /// respect to the given block. 757 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB); 758 759 /// dominates - Return true if elements that makes up the given SCEV 760 /// dominate the specified basic block. 761 bool dominates(const SCEV *S, const BasicBlock *BB); 762 763 /// properlyDominates - Return true if elements that makes up the given SCEV 764 /// properly dominate the specified basic block. 765 bool properlyDominates(const SCEV *S, const BasicBlock *BB); 766 767 /// hasOperand - Test whether the given SCEV has Op as a direct or 768 /// indirect operand. 769 bool hasOperand(const SCEV *S, const SCEV *Op) const; 770 771 virtual bool runOnFunction(Function &F); 772 virtual void releaseMemory(); 773 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 774 virtual void print(raw_ostream &OS, const Module* = 0) const; 775 776 private: 777 FoldingSet<SCEV> UniqueSCEVs; 778 BumpPtrAllocator SCEVAllocator; 779 780 /// FirstUnknown - The head of a linked list of all SCEVUnknown 781 /// values that have been allocated. This is used by releaseMemory 782 /// to locate them all and call their destructors. 783 SCEVUnknown *FirstUnknown; 784 }; 785 } 786 787 #endif 788
