ScalarEvolution.h revision b12a754cce0c1d5542af605203a47820edba454d
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/Support/DataTypes.h" 28#include "llvm/Support/ValueHandle.h" 29#include "llvm/Support/Allocator.h" 30#include "llvm/Support/ConstantRange.h" 31#include "llvm/ADT/FoldingSet.h" 32#include "llvm/ADT/DenseMap.h" 33#include <map> 34 35namespace llvm { 36 class APInt; 37 class Constant; 38 class ConstantInt; 39 class DominatorTree; 40 class Type; 41 class ScalarEvolution; 42 class TargetData; 43 class LLVMContext; 44 class Loop; 45 class LoopInfo; 46 class Operator; 47 class SCEVUnknown; 48 class SCEV; 49 template<> struct FoldingSetTrait<SCEV>; 50 51 /// SCEV - This class represents an analyzed expression in the program. These 52 /// are opaque objects that the client is not allowed to do much with 53 /// directly. 54 /// 55 class SCEV : public FoldingSetNode { 56 friend struct FoldingSetTrait<SCEV>; 57 58 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 59 /// The ScalarEvolution's BumpPtrAllocator holds the data. 60 FoldingSetNodeIDRef FastID; 61 62 // The SCEV baseclass this node corresponds to 63 const unsigned short SCEVType; 64 65 protected: 66 /// SubclassData - This field is initialized to zero and may be used in 67 /// subclasses to store miscellaneous information. 68 unsigned short SubclassData; 69 70 private: 71 SCEV(const SCEV &); // DO NOT IMPLEMENT 72 void operator=(const SCEV &); // DO NOT IMPLEMENT 73 74 public: 75 /// NoWrapFlags are bitfield indices into SubclassData. 76 /// 77 /// Add and Mul expressions may have no-unsigned-wrap <NUW> or 78 /// no-signed-wrap <NSW> properties, which are derived from the IR 79 /// operator. NSW is a misnomer that we use to mean no signed overflow or 80 /// underflow. 81 /// 82 /// AddRec expression may have a no-self-wraparound <NW> property if the 83 /// result can never reach the start value. This property is independent of 84 /// the actual start value and step direction. Self-wraparound is defined 85 /// purely in terms of the recurrence's loop, step size, and 86 /// bitwidth. Formally, a recurrence with no self-wraparound satisfies: 87 /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth). 88 /// 89 /// Note that NUW and NSW are also valid properties of a recurrence, and 90 /// either implies NW. For convenience, NW will be set for a recurrence 91 /// whenever either NUW or NSW are set. 92 enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee. 93 FlagNW = (1 << 0), // No self-wrap. 94 FlagNUW = (1 << 1), // No unsigned wrap. 95 FlagNSW = (1 << 2), // No signed wrap. 96 NoWrapMask = (1 << 3) -1 }; 97 98 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 99 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 100 101 unsigned getSCEVType() const { return SCEVType; } 102 103 /// getType - Return the LLVM type of this SCEV expression. 104 /// 105 const Type *getType() const; 106 107 /// isZero - Return true if the expression is a constant zero. 108 /// 109 bool isZero() const; 110 111 /// isOne - Return true if the expression is a constant one. 112 /// 113 bool isOne() const; 114 115 /// isAllOnesValue - Return true if the expression is a constant 116 /// all-ones value. 117 /// 118 bool isAllOnesValue() const; 119 120 /// print - Print out the internal representation of this scalar to the 121 /// specified stream. This should really only be used for debugging 122 /// purposes. 123 void print(raw_ostream &OS) const; 124 125 /// dump - This method is used for debugging. 126 /// 127 void dump() const; 128 }; 129 130 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 131 // temporary FoldingSetNodeID values. 132 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 133 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 134 ID = X.FastID; 135 } 136 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 137 FoldingSetNodeID &TempID) { 138 return ID == X.FastID; 139 } 140 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 141 return X.FastID.ComputeHash(); 142 } 143 }; 144 145 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 146 S.print(OS); 147 return OS; 148 } 149 150 /// SCEVCouldNotCompute - An object of this class is returned by queries that 151 /// could not be answered. For example, if you ask for the number of 152 /// iterations of a linked-list traversal loop, you will get one of these. 153 /// None of the standard SCEV operations are valid on this class, it is just a 154 /// marker. 155 struct SCEVCouldNotCompute : public SCEV { 156 SCEVCouldNotCompute(); 157 158 /// Methods for support type inquiry through isa, cast, and dyn_cast: 159 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 160 static bool classof(const SCEV *S); 161 }; 162 163 /// ScalarEvolution - This class is the main scalar evolution driver. Because 164 /// client code (intentionally) can't do much with the SCEV objects directly, 165 /// they must ask this class for services. 166 /// 167 class ScalarEvolution : public FunctionPass { 168 public: 169 /// LoopDisposition - An enum describing the relationship between a 170 /// SCEV and a loop. 171 enum LoopDisposition { 172 LoopVariant, ///< The SCEV is loop-variant (unknown). 173 LoopInvariant, ///< The SCEV is loop-invariant. 174 LoopComputable ///< The SCEV varies predictably with the loop. 175 }; 176 177 /// BlockDisposition - An enum describing the relationship between a 178 /// SCEV and a basic block. 179 enum BlockDisposition { 180 DoesNotDominateBlock, ///< The SCEV does not dominate the block. 181 DominatesBlock, ///< The SCEV dominates the block. 182 ProperlyDominatesBlock ///< The SCEV properly dominates the block. 183 }; 184 185 /// Convenient NoWrapFlags manipulation that hides enum casts and is 186 /// visible in the ScalarEvolution name space. 187 static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) { 188 return (SCEV::NoWrapFlags)(Flags & Mask); 189 } 190 static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags, 191 SCEV::NoWrapFlags OnFlags) { 192 return (SCEV::NoWrapFlags)(Flags | OnFlags); 193 } 194 static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags, 195 SCEV::NoWrapFlags OffFlags) { 196 return (SCEV::NoWrapFlags)(Flags & ~OffFlags); 197 } 198 199 private: 200 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 201 /// notified whenever a Value is deleted. 202 class SCEVCallbackVH : public CallbackVH { 203 ScalarEvolution *SE; 204 virtual void deleted(); 205 virtual void allUsesReplacedWith(Value *New); 206 public: 207 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 208 }; 209 210 friend class SCEVCallbackVH; 211 friend class SCEVExpander; 212 friend class SCEVUnknown; 213 214 /// F - The function we are analyzing. 215 /// 216 Function *F; 217 218 /// LI - The loop information for the function we are currently analyzing. 219 /// 220 LoopInfo *LI; 221 222 /// TD - The target data information for the target we are targeting. 223 /// 224 TargetData *TD; 225 226 /// DT - The dominator tree. 227 /// 228 DominatorTree *DT; 229 230 /// CouldNotCompute - This SCEV is used to represent unknown trip 231 /// counts and things. 232 SCEVCouldNotCompute CouldNotCompute; 233 234 /// ValueExprMapType - The typedef for ValueExprMap. 235 /// 236 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 237 ValueExprMapType; 238 239 /// ValueExprMap - This is a cache of the values we have analyzed so far. 240 /// 241 ValueExprMapType ValueExprMap; 242 243 /// BackedgeTakenInfo - Information about the backedge-taken count 244 /// of a loop. This currently includes an exact count and a maximum count. 245 /// 246 struct BackedgeTakenInfo { 247 /// Exact - An expression indicating the exact backedge-taken count of 248 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 249 const SCEV *Exact; 250 251 /// Max - An expression indicating the least maximum backedge-taken 252 /// count of the loop that is known, or a SCEVCouldNotCompute. 253 const SCEV *Max; 254 255 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 256 Exact(exact), Max(exact) {} 257 258 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 259 Exact(exact), Max(max) {} 260 261 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 262 /// computed information, or whether it's all SCEVCouldNotCompute 263 /// values. 264 bool hasAnyInfo() const { 265 return !isa<SCEVCouldNotCompute>(Exact) || 266 !isa<SCEVCouldNotCompute>(Max); 267 } 268 }; 269 270 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 271 /// this function as they are computed. 272 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 273 274 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 275 /// the PHI instructions that we attempt to compute constant evolutions for. 276 /// This allows us to avoid potentially expensive recomputation of these 277 /// properties. An instruction maps to null if we are unable to compute its 278 /// exit value. 279 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 280 281 /// ValuesAtScopes - This map contains entries for all the expressions 282 /// that we attempt to compute getSCEVAtScope information for, which can 283 /// be expensive in extreme cases. 284 std::map<const SCEV *, 285 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 286 287 /// LoopDispositions - Memoized computeLoopDisposition results. 288 std::map<const SCEV *, 289 std::map<const Loop *, LoopDisposition> > LoopDispositions; 290 291 /// computeLoopDisposition - Compute a LoopDisposition value. 292 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 293 294 /// BlockDispositions - Memoized computeBlockDisposition results. 295 std::map<const SCEV *, 296 std::map<const BasicBlock *, BlockDisposition> > BlockDispositions; 297 298 /// computeBlockDisposition - Compute a BlockDisposition value. 299 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB); 300 301 /// UnsignedRanges - Memoized results from getUnsignedRange 302 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 303 304 /// SignedRanges - Memoized results from getSignedRange 305 DenseMap<const SCEV *, ConstantRange> SignedRanges; 306 307 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 308 const ConstantRange &setUnsignedRange(const SCEV *S, 309 const ConstantRange &CR) { 310 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 311 UnsignedRanges.insert(std::make_pair(S, CR)); 312 if (!Pair.second) 313 Pair.first->second = CR; 314 return Pair.first->second; 315 } 316 317 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 318 const ConstantRange &setSignedRange(const SCEV *S, 319 const ConstantRange &CR) { 320 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 321 SignedRanges.insert(std::make_pair(S, CR)); 322 if (!Pair.second) 323 Pair.first->second = CR; 324 return Pair.first->second; 325 } 326 327 /// createSCEV - We know that there is no SCEV for the specified value. 328 /// Analyze the expression. 329 const SCEV *createSCEV(Value *V); 330 331 /// createNodeForPHI - Provide the special handling we need to analyze PHI 332 /// SCEVs. 333 const SCEV *createNodeForPHI(PHINode *PN); 334 335 /// createNodeForGEP - Provide the special handling we need to analyze GEP 336 /// SCEVs. 337 const SCEV *createNodeForGEP(GEPOperator *GEP); 338 339 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 340 /// at most once for each SCEV+Loop pair. 341 /// 342 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 343 344 /// ForgetSymbolicValue - This looks up computed SCEV values for all 345 /// instructions that depend on the given instruction and removes them from 346 /// the ValueExprMap map if they reference SymName. This is used during PHI 347 /// resolution. 348 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 349 350 /// getBECount - Subtract the end and start values and divide by the step, 351 /// rounding up, to get the number of times the backedge is executed. Return 352 /// CouldNotCompute if an intermediate computation overflows. 353 const SCEV *getBECount(const SCEV *Start, 354 const SCEV *End, 355 const SCEV *Step, 356 bool NoWrap); 357 358 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 359 /// loop, lazily computing new values if the loop hasn't been analyzed 360 /// yet. 361 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 362 363 /// ComputeBackedgeTakenCount - Compute the number of times the specified 364 /// loop will iterate. 365 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 366 367 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 368 /// backedge of the specified loop will execute if it exits via the 369 /// specified block. 370 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 371 BasicBlock *ExitingBlock); 372 373 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 374 /// backedge of the specified loop will execute if its exit condition 375 /// were a conditional branch of ExitCond, TBB, and FBB. 376 BackedgeTakenInfo 377 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 378 Value *ExitCond, 379 BasicBlock *TBB, 380 BasicBlock *FBB); 381 382 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 383 /// times the backedge of the specified loop will execute if its exit 384 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 385 /// and FBB. 386 BackedgeTakenInfo 387 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 388 ICmpInst *ExitCond, 389 BasicBlock *TBB, 390 BasicBlock *FBB); 391 392 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 393 /// of 'icmp op load X, cst', try to see if we can compute the 394 /// backedge-taken count. 395 BackedgeTakenInfo 396 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 397 Constant *RHS, 398 const Loop *L, 399 ICmpInst::Predicate p); 400 401 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 402 /// a constant number of times (the condition evolves only from constants), 403 /// try to evaluate a few iterations of the loop until we get the exit 404 /// condition gets a value of ExitWhen (true or false). If we cannot 405 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 406 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 407 Value *Cond, 408 bool ExitWhen); 409 410 /// HowFarToZero - Return the number of times a backedge comparing the 411 /// specified value to zero will execute. If not computable, return 412 /// CouldNotCompute. 413 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 414 415 /// HowFarToNonZero - Return the number of times a backedge checking the 416 /// specified value for nonzero will execute. If not computable, return 417 /// CouldNotCompute. 418 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 419 420 /// HowManyLessThans - Return the number of times a backedge containing the 421 /// specified less-than comparison will execute. If not computable, return 422 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 423 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 424 const Loop *L, bool isSigned); 425 426 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 427 /// (which may not be an immediate predecessor) which has exactly one 428 /// successor from which BB is reachable, or null if no such block is 429 /// found. 430 std::pair<BasicBlock *, BasicBlock *> 431 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 432 433 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 434 /// RHS is true whenever the given FoundCondValue value evaluates to true. 435 bool isImpliedCond(ICmpInst::Predicate Pred, 436 const SCEV *LHS, const SCEV *RHS, 437 Value *FoundCondValue, 438 bool Inverse); 439 440 /// isImpliedCondOperands - Test whether the condition described by Pred, 441 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 442 /// and FoundRHS is true. 443 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 444 const SCEV *LHS, const SCEV *RHS, 445 const SCEV *FoundLHS, const SCEV *FoundRHS); 446 447 /// isImpliedCondOperandsHelper - Test whether the condition described by 448 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 449 /// FoundLHS, and FoundRHS is true. 450 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 451 const SCEV *LHS, const SCEV *RHS, 452 const SCEV *FoundLHS, const SCEV *FoundRHS); 453 454 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 455 /// in the header of its containing loop, we know the loop executes a 456 /// constant number of times, and the PHI node is just a recurrence 457 /// involving constants, fold it. 458 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 459 const Loop *L); 460 461 /// isKnownPredicateWithRanges - Test if the given expression is known to 462 /// satisfy the condition described by Pred and the known constant ranges 463 /// of LHS and RHS. 464 /// 465 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 466 const SCEV *LHS, const SCEV *RHS); 467 468 /// forgetMemoizedResults - Drop memoized information computed for S. 469 void forgetMemoizedResults(const SCEV *S); 470 471 public: 472 static char ID; // Pass identification, replacement for typeid 473 ScalarEvolution(); 474 475 LLVMContext &getContext() const { return F->getContext(); } 476 477 /// isSCEVable - Test if values of the given type are analyzable within 478 /// the SCEV framework. This primarily includes integer types, and it 479 /// can optionally include pointer types if the ScalarEvolution class 480 /// has access to target-specific information. 481 bool isSCEVable(const Type *Ty) const; 482 483 /// getTypeSizeInBits - Return the size in bits of the specified type, 484 /// for which isSCEVable must return true. 485 uint64_t getTypeSizeInBits(const Type *Ty) const; 486 487 /// getEffectiveSCEVType - Return a type with the same bitwidth as 488 /// the given type and which represents how SCEV will treat the given 489 /// type, for which isSCEVable must return true. For pointer types, 490 /// this is the pointer-sized integer type. 491 const Type *getEffectiveSCEVType(const Type *Ty) const; 492 493 /// getSCEV - Return a SCEV expression for the full generality of the 494 /// specified expression. 495 const SCEV *getSCEV(Value *V); 496 497 const SCEV *getConstant(ConstantInt *V); 498 const SCEV *getConstant(const APInt& Val); 499 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 500 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 501 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 502 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 503 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 504 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 505 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 506 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 507 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 508 SmallVector<const SCEV *, 2> Ops; 509 Ops.push_back(LHS); 510 Ops.push_back(RHS); 511 return getAddExpr(Ops, Flags); 512 } 513 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 514 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 515 SmallVector<const SCEV *, 3> Ops; 516 Ops.push_back(Op0); 517 Ops.push_back(Op1); 518 Ops.push_back(Op2); 519 return getAddExpr(Ops, Flags); 520 } 521 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 522 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 523 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 524 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) 525 { 526 SmallVector<const SCEV *, 2> Ops; 527 Ops.push_back(LHS); 528 Ops.push_back(RHS); 529 return getMulExpr(Ops, Flags); 530 } 531 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 532 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 533 const Loop *L, SCEV::NoWrapFlags Flags); 534 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 535 const Loop *L, SCEV::NoWrapFlags Flags); 536 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 537 const Loop *L, SCEV::NoWrapFlags Flags) { 538 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 539 return getAddRecExpr(NewOp, L, Flags); 540 } 541 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 542 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 543 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 544 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 545 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 546 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 547 const SCEV *getUnknown(Value *V); 548 const SCEV *getCouldNotCompute(); 549 550 /// getSizeOfExpr - Return an expression for sizeof on the given type. 551 /// 552 const SCEV *getSizeOfExpr(const Type *AllocTy); 553 554 /// getAlignOfExpr - Return an expression for alignof on the given type. 555 /// 556 const SCEV *getAlignOfExpr(const Type *AllocTy); 557 558 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 559 /// 560 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 561 562 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 563 /// 564 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 565 566 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 567 /// 568 const SCEV *getNegativeSCEV(const SCEV *V); 569 570 /// getNotSCEV - Return the SCEV object corresponding to ~V. 571 /// 572 const SCEV *getNotSCEV(const SCEV *V); 573 574 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1. 575 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS, 576 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 577 578 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 579 /// of the input value to the specified type. If the type must be 580 /// extended, it is zero extended. 581 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 582 583 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 584 /// of the input value to the specified type. If the type must be 585 /// extended, it is sign extended. 586 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 587 588 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 589 /// the input value to the specified type. If the type must be extended, 590 /// it is zero extended. The conversion must not be narrowing. 591 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 592 593 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 594 /// the input value to the specified type. If the type must be extended, 595 /// it is sign extended. The conversion must not be narrowing. 596 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 597 598 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 599 /// the input value to the specified type. If the type must be extended, 600 /// it is extended with unspecified bits. The conversion must not be 601 /// narrowing. 602 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 603 604 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 605 /// input value to the specified type. The conversion must not be 606 /// widening. 607 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 608 609 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 610 /// the types using zero-extension, and then perform a umax operation 611 /// with them. 612 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 613 const SCEV *RHS); 614 615 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 616 /// the types using zero-extension, and then perform a umin operation 617 /// with them. 618 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 619 const SCEV *RHS); 620 621 /// getPointerBase - Transitively follow the chain of pointer-type operands 622 /// until reaching a SCEV that does not have a single pointer operand. This 623 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions, 624 /// but corner cases do exist. 625 const SCEV *getPointerBase(const SCEV *V); 626 627 /// getSCEVAtScope - Return a SCEV expression for the specified value 628 /// at the specified scope in the program. The L value specifies a loop 629 /// nest to evaluate the expression at, where null is the top-level or a 630 /// specified loop is immediately inside of the loop. 631 /// 632 /// This method can be used to compute the exit value for a variable defined 633 /// in a loop by querying what the value will hold in the parent loop. 634 /// 635 /// In the case that a relevant loop exit value cannot be computed, the 636 /// original value V is returned. 637 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 638 639 /// getSCEVAtScope - This is a convenience function which does 640 /// getSCEVAtScope(getSCEV(V), L). 641 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 642 643 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 644 /// by a conditional between LHS and RHS. This is used to help avoid max 645 /// expressions in loop trip counts, and to eliminate casts. 646 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 647 const SCEV *LHS, const SCEV *RHS); 648 649 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 650 /// protected by a conditional between LHS and RHS. This is used to 651 /// to eliminate casts. 652 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 653 const SCEV *LHS, const SCEV *RHS); 654 655 /// getBackedgeTakenCount - If the specified loop has a predictable 656 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 657 /// object. The backedge-taken count is the number of times the loop header 658 /// will be branched to from within the loop. This is one less than the 659 /// trip count of the loop, since it doesn't count the first iteration, 660 /// when the header is branched to from outside the loop. 661 /// 662 /// Note that it is not valid to call this method on a loop without a 663 /// loop-invariant backedge-taken count (see 664 /// hasLoopInvariantBackedgeTakenCount). 665 /// 666 const SCEV *getBackedgeTakenCount(const Loop *L); 667 668 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 669 /// return the least SCEV value that is known never to be less than the 670 /// actual backedge taken count. 671 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 672 673 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 674 /// has an analyzable loop-invariant backedge-taken count. 675 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 676 677 /// forgetLoop - This method should be called by the client when it has 678 /// changed a loop in a way that may effect ScalarEvolution's ability to 679 /// compute a trip count, or if the loop is deleted. 680 void forgetLoop(const Loop *L); 681 682 /// forgetValue - This method should be called by the client when it has 683 /// changed a value in a way that may effect its value, or which may 684 /// disconnect it from a def-use chain linking it to a loop. 685 void forgetValue(Value *V); 686 687 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 688 /// is guaranteed to end in (at every loop iteration). It is, at the same 689 /// time, the minimum number of times S is divisible by 2. For example, 690 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 691 /// bitwidth of S. 692 uint32_t GetMinTrailingZeros(const SCEV *S); 693 694 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 695 /// 696 ConstantRange getUnsignedRange(const SCEV *S); 697 698 /// getSignedRange - Determine the signed range for a particular SCEV. 699 /// 700 ConstantRange getSignedRange(const SCEV *S); 701 702 /// isKnownNegative - Test if the given expression is known to be negative. 703 /// 704 bool isKnownNegative(const SCEV *S); 705 706 /// isKnownPositive - Test if the given expression is known to be positive. 707 /// 708 bool isKnownPositive(const SCEV *S); 709 710 /// isKnownNonNegative - Test if the given expression is known to be 711 /// non-negative. 712 /// 713 bool isKnownNonNegative(const SCEV *S); 714 715 /// isKnownNonPositive - Test if the given expression is known to be 716 /// non-positive. 717 /// 718 bool isKnownNonPositive(const SCEV *S); 719 720 /// isKnownNonZero - Test if the given expression is known to be 721 /// non-zero. 722 /// 723 bool isKnownNonZero(const SCEV *S); 724 725 /// isKnownPredicate - Test if the given expression is known to satisfy 726 /// the condition described by Pred, LHS, and RHS. 727 /// 728 bool isKnownPredicate(ICmpInst::Predicate Pred, 729 const SCEV *LHS, const SCEV *RHS); 730 731 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 732 /// predicate Pred. Return true iff any changes were made. If the 733 /// operands are provably equal or inequal, LHS and RHS are set to 734 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 735 /// 736 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 737 const SCEV *&LHS, 738 const SCEV *&RHS); 739 740 /// getLoopDisposition - Return the "disposition" of the given SCEV with 741 /// respect to the given loop. 742 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 743 744 /// isLoopInvariant - Return true if the value of the given SCEV is 745 /// unchanging in the specified loop. 746 bool isLoopInvariant(const SCEV *S, const Loop *L); 747 748 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 749 /// in a known way in the specified loop. This property being true implies 750 /// that the value is variant in the loop AND that we can emit an expression 751 /// to compute the value of the expression at any particular loop iteration. 752 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 753 754 /// getLoopDisposition - Return the "disposition" of the given SCEV with 755 /// respect to the given block. 756 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB); 757 758 /// dominates - Return true if elements that makes up the given SCEV 759 /// dominate the specified basic block. 760 bool dominates(const SCEV *S, const BasicBlock *BB); 761 762 /// properlyDominates - Return true if elements that makes up the given SCEV 763 /// properly dominate the specified basic block. 764 bool properlyDominates(const SCEV *S, const BasicBlock *BB); 765 766 /// hasOperand - Test whether the given SCEV has Op as a direct or 767 /// indirect operand. 768 bool hasOperand(const SCEV *S, const SCEV *Op) const; 769 770 virtual bool runOnFunction(Function &F); 771 virtual void releaseMemory(); 772 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 773 virtual void print(raw_ostream &OS, const Module* = 0) const; 774 775 private: 776 FoldingSet<SCEV> UniqueSCEVs; 777 BumpPtrAllocator SCEVAllocator; 778 779 /// FirstUnknown - The head of a linked list of all SCEVUnknown 780 /// values that have been allocated. This is used by releaseMemory 781 /// to locate them all and call their destructors. 782 SCEVUnknown *FirstUnknown; 783 }; 784} 785 786#endif 787