ScalarEvolution.h revision b1831c66403315a1d84593b7c198ddbd43a574cf
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 36namespace 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 /// ExitLimit - Information about the number of loop iterations for 245 /// which a loop exit's branch condition evaluates to the not-taken path. 246 /// This is a temporary pair of exact and max expressions that are 247 /// eventually summarized in ExitNotTakenInfo and BackedgeTakenInfo. 248 struct ExitLimit { 249 const SCEV *Exact; 250 const SCEV *Max; 251 252 /*implicit*/ ExitLimit(const SCEV *E) : Exact(E), Max(E) {} 253 254 ExitLimit(const SCEV *E, const SCEV *M) : Exact(E), Max(M) {} 255 256 /// hasAnyInfo - Test whether this ExitLimit contains any computed 257 /// information, or whether it's all SCEVCouldNotCompute values. 258 bool hasAnyInfo() const { 259 return !isa<SCEVCouldNotCompute>(Exact) || 260 !isa<SCEVCouldNotCompute>(Max); 261 } 262 }; 263 264 /// ExitNotTakenInfo - Information about the number of times a particular 265 /// loop exit may be reached before exiting the loop. 266 struct ExitNotTakenInfo { 267 AssertingVH<BasicBlock> ExitingBlock; 268 const SCEV *ExactNotTaken; 269 PointerIntPair<ExitNotTakenInfo*, 1> NextExit; 270 271 ExitNotTakenInfo() : ExitingBlock(0), ExactNotTaken(0) {} 272 273 /// isCompleteList - Return true if all loop exits are computable. 274 bool isCompleteList() const { 275 return NextExit.getInt() == 0; 276 } 277 278 void setIncomplete() { NextExit.setInt(1); } 279 280 /// getNextExit - Return a pointer to the next exit's not-taken info. 281 ExitNotTakenInfo *getNextExit() const { 282 return NextExit.getPointer(); 283 } 284 285 void setNextExit(ExitNotTakenInfo *ENT) { NextExit.setPointer(ENT); } 286 }; 287 288 /// BackedgeTakenInfo - Information about the backedge-taken count 289 /// of a loop. This currently includes an exact count and a maximum count. 290 /// 291 class BackedgeTakenInfo { 292 /// ExitNotTaken - A list of computable exits and their not-taken counts. 293 /// Loops almost never have more than one computable exit. 294 ExitNotTakenInfo ExitNotTaken; 295 296 /// Max - An expression indicating the least maximum backedge-taken 297 /// count of the loop that is known, or a SCEVCouldNotCompute. 298 const SCEV *Max; 299 300 public: 301 BackedgeTakenInfo() : Max(0) {} 302 303 /// Initialize BackedgeTakenInfo from a list of exact exit counts. 304 BackedgeTakenInfo( 305 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts, 306 bool Complete, const SCEV *MaxCount); 307 308 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 309 /// computed information, or whether it's all SCEVCouldNotCompute 310 /// values. 311 bool hasAnyInfo() const { 312 return ExitNotTaken.ExitingBlock || !isa<SCEVCouldNotCompute>(Max); 313 } 314 315 /// getExact - Return an expression indicating the exact backedge-taken 316 /// count of the loop if it is known, or SCEVCouldNotCompute 317 /// otherwise. This is the number of times the loop header can be 318 /// guaranteed to execute, minus one. 319 const SCEV *getExact(ScalarEvolution *SE) const; 320 321 /// getExact - Return the number of times this loop exit may fall through 322 /// to the back edge. The loop is guaranteed not to exit via this block 323 /// before this number of iterations, but may exit via another block. 324 const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const; 325 326 /// getMax - Get the max backedge taken count for the loop. 327 const SCEV *getMax(ScalarEvolution *SE) const; 328 329 /// clear - Invalidate this result and free associated memory. 330 void clear(); 331 }; 332 333 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 334 /// this function as they are computed. 335 DenseMap<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 336 337 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 338 /// the PHI instructions that we attempt to compute constant evolutions for. 339 /// This allows us to avoid potentially expensive recomputation of these 340 /// properties. An instruction maps to null if we are unable to compute its 341 /// exit value. 342 DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 343 344 /// ValuesAtScopes - This map contains entries for all the expressions 345 /// that we attempt to compute getSCEVAtScope information for, which can 346 /// be expensive in extreme cases. 347 DenseMap<const SCEV *, 348 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 349 350 /// LoopDispositions - Memoized computeLoopDisposition results. 351 DenseMap<const SCEV *, 352 std::map<const Loop *, LoopDisposition> > LoopDispositions; 353 354 /// computeLoopDisposition - Compute a LoopDisposition value. 355 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 356 357 /// BlockDispositions - Memoized computeBlockDisposition results. 358 DenseMap<const SCEV *, 359 std::map<const BasicBlock *, BlockDisposition> > BlockDispositions; 360 361 /// computeBlockDisposition - Compute a BlockDisposition value. 362 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB); 363 364 /// UnsignedRanges - Memoized results from getUnsignedRange 365 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 366 367 /// SignedRanges - Memoized results from getSignedRange 368 DenseMap<const SCEV *, ConstantRange> SignedRanges; 369 370 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 371 const ConstantRange &setUnsignedRange(const SCEV *S, 372 const ConstantRange &CR) { 373 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 374 UnsignedRanges.insert(std::make_pair(S, CR)); 375 if (!Pair.second) 376 Pair.first->second = CR; 377 return Pair.first->second; 378 } 379 380 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 381 const ConstantRange &setSignedRange(const SCEV *S, 382 const ConstantRange &CR) { 383 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 384 SignedRanges.insert(std::make_pair(S, CR)); 385 if (!Pair.second) 386 Pair.first->second = CR; 387 return Pair.first->second; 388 } 389 390 /// createSCEV - We know that there is no SCEV for the specified value. 391 /// Analyze the expression. 392 const SCEV *createSCEV(Value *V); 393 394 /// createNodeForPHI - Provide the special handling we need to analyze PHI 395 /// SCEVs. 396 const SCEV *createNodeForPHI(PHINode *PN); 397 398 /// createNodeForGEP - Provide the special handling we need to analyze GEP 399 /// SCEVs. 400 const SCEV *createNodeForGEP(GEPOperator *GEP); 401 402 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 403 /// at most once for each SCEV+Loop pair. 404 /// 405 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 406 407 /// ForgetSymbolicValue - This looks up computed SCEV values for all 408 /// instructions that depend on the given instruction and removes them from 409 /// the ValueExprMap map if they reference SymName. This is used during PHI 410 /// resolution. 411 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 412 413 /// getBECount - Subtract the end and start values and divide by the step, 414 /// rounding up, to get the number of times the backedge is executed. Return 415 /// CouldNotCompute if an intermediate computation overflows. 416 const SCEV *getBECount(const SCEV *Start, 417 const SCEV *End, 418 const SCEV *Step, 419 bool NoWrap); 420 421 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 422 /// loop, lazily computing new values if the loop hasn't been analyzed 423 /// yet. 424 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 425 426 /// ComputeBackedgeTakenCount - Compute the number of times the specified 427 /// loop will iterate. 428 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 429 430 /// ComputeExitLimit - Compute the number of times the backedge of the 431 /// specified loop will execute if it exits via the specified block. 432 ExitLimit ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock); 433 434 /// ComputeExitLimitFromCond - Compute the number of times the backedge of 435 /// the specified loop will execute if its exit condition were a conditional 436 /// branch of ExitCond, TBB, and FBB. 437 ExitLimit ComputeExitLimitFromCond(const Loop *L, 438 Value *ExitCond, 439 BasicBlock *TBB, 440 BasicBlock *FBB); 441 442 /// ComputeExitLimitFromICmp - Compute the number of times the backedge of 443 /// the specified loop will execute if its exit condition were a conditional 444 /// branch of the ICmpInst ExitCond, TBB, and FBB. 445 ExitLimit ComputeExitLimitFromICmp(const Loop *L, 446 ICmpInst *ExitCond, 447 BasicBlock *TBB, 448 BasicBlock *FBB); 449 450 /// ComputeLoadConstantCompareExitLimit - Given an exit condition 451 /// of 'icmp op load X, cst', try to see if we can compute the 452 /// backedge-taken count. 453 ExitLimit ComputeLoadConstantCompareExitLimit(LoadInst *LI, 454 Constant *RHS, 455 const Loop *L, 456 ICmpInst::Predicate p); 457 458 /// ComputeExitCountExhaustively - If the loop is known to execute a 459 /// constant number of times (the condition evolves only from constants), 460 /// try to evaluate a few iterations of the loop until we get the exit 461 /// condition gets a value of ExitWhen (true or false). If we cannot 462 /// evaluate the exit count of the loop, return CouldNotCompute. 463 const SCEV *ComputeExitCountExhaustively(const Loop *L, 464 Value *Cond, 465 bool ExitWhen); 466 467 /// HowFarToZero - Return the number of times an exit condition comparing 468 /// the specified value to zero will execute. If not computable, return 469 /// CouldNotCompute. 470 ExitLimit HowFarToZero(const SCEV *V, const Loop *L); 471 472 /// HowFarToNonZero - Return the number of times an exit condition checking 473 /// the specified value for nonzero will execute. If not computable, return 474 /// CouldNotCompute. 475 ExitLimit HowFarToNonZero(const SCEV *V, const Loop *L); 476 477 /// HowManyLessThans - Return the number of times an exit condition 478 /// containing the specified less-than comparison will execute. If not 479 /// computable, return CouldNotCompute. isSigned specifies whether the 480 /// less-than is signed. 481 ExitLimit HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 482 const Loop *L, bool isSigned); 483 484 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 485 /// (which may not be an immediate predecessor) which has exactly one 486 /// successor from which BB is reachable, or null if no such block is 487 /// found. 488 std::pair<BasicBlock *, BasicBlock *> 489 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 490 491 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 492 /// RHS is true whenever the given FoundCondValue value evaluates to true. 493 bool isImpliedCond(ICmpInst::Predicate Pred, 494 const SCEV *LHS, const SCEV *RHS, 495 Value *FoundCondValue, 496 bool Inverse); 497 498 /// isImpliedCondOperands - Test whether the condition described by Pred, 499 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 500 /// and FoundRHS is true. 501 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 502 const SCEV *LHS, const SCEV *RHS, 503 const SCEV *FoundLHS, const SCEV *FoundRHS); 504 505 /// isImpliedCondOperandsHelper - Test whether the condition described by 506 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 507 /// FoundLHS, and FoundRHS is true. 508 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 509 const SCEV *LHS, const SCEV *RHS, 510 const SCEV *FoundLHS, 511 const SCEV *FoundRHS); 512 513 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 514 /// in the header of its containing loop, we know the loop executes a 515 /// constant number of times, and the PHI node is just a recurrence 516 /// involving constants, fold it. 517 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 518 const Loop *L); 519 520 /// isKnownPredicateWithRanges - Test if the given expression is known to 521 /// satisfy the condition described by Pred and the known constant ranges 522 /// of LHS and RHS. 523 /// 524 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 525 const SCEV *LHS, const SCEV *RHS); 526 527 /// forgetMemoizedResults - Drop memoized information computed for S. 528 void forgetMemoizedResults(const SCEV *S); 529 530 public: 531 static char ID; // Pass identification, replacement for typeid 532 ScalarEvolution(); 533 534 LLVMContext &getContext() const { return F->getContext(); } 535 536 /// isSCEVable - Test if values of the given type are analyzable within 537 /// the SCEV framework. This primarily includes integer types, and it 538 /// can optionally include pointer types if the ScalarEvolution class 539 /// has access to target-specific information. 540 bool isSCEVable(Type *Ty) const; 541 542 /// getTypeSizeInBits - Return the size in bits of the specified type, 543 /// for which isSCEVable must return true. 544 uint64_t getTypeSizeInBits(Type *Ty) const; 545 546 /// getEffectiveSCEVType - Return a type with the same bitwidth as 547 /// the given type and which represents how SCEV will treat the given 548 /// type, for which isSCEVable must return true. For pointer types, 549 /// this is the pointer-sized integer type. 550 Type *getEffectiveSCEVType(Type *Ty) const; 551 552 /// getSCEV - Return a SCEV expression for the full generality of the 553 /// specified expression. 554 const SCEV *getSCEV(Value *V); 555 556 const SCEV *getConstant(ConstantInt *V); 557 const SCEV *getConstant(const APInt& Val); 558 const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false); 559 const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty); 560 const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty); 561 const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty); 562 const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty); 563 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 564 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 565 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 566 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 567 SmallVector<const SCEV *, 2> Ops; 568 Ops.push_back(LHS); 569 Ops.push_back(RHS); 570 return getAddExpr(Ops, Flags); 571 } 572 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 573 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 574 SmallVector<const SCEV *, 3> Ops; 575 Ops.push_back(Op0); 576 Ops.push_back(Op1); 577 Ops.push_back(Op2); 578 return getAddExpr(Ops, Flags); 579 } 580 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 581 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 582 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 583 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) 584 { 585 SmallVector<const SCEV *, 2> Ops; 586 Ops.push_back(LHS); 587 Ops.push_back(RHS); 588 return getMulExpr(Ops, Flags); 589 } 590 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 591 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 592 const Loop *L, SCEV::NoWrapFlags Flags); 593 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 594 const Loop *L, SCEV::NoWrapFlags Flags); 595 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 596 const Loop *L, SCEV::NoWrapFlags Flags) { 597 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 598 return getAddRecExpr(NewOp, L, Flags); 599 } 600 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 601 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 602 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 603 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 604 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 605 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 606 const SCEV *getUnknown(Value *V); 607 const SCEV *getCouldNotCompute(); 608 609 /// getSizeOfExpr - Return an expression for sizeof on the given type. 610 /// 611 const SCEV *getSizeOfExpr(Type *AllocTy); 612 613 /// getAlignOfExpr - Return an expression for alignof on the given type. 614 /// 615 const SCEV *getAlignOfExpr(Type *AllocTy); 616 617 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 618 /// 619 const SCEV *getOffsetOfExpr(StructType *STy, unsigned FieldNo); 620 621 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 622 /// 623 const SCEV *getOffsetOfExpr(Type *CTy, Constant *FieldNo); 624 625 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 626 /// 627 const SCEV *getNegativeSCEV(const SCEV *V); 628 629 /// getNotSCEV - Return the SCEV object corresponding to ~V. 630 /// 631 const SCEV *getNotSCEV(const SCEV *V); 632 633 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1. 634 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS, 635 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 636 637 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 638 /// of the input value to the specified type. If the type must be 639 /// extended, it is zero extended. 640 const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty); 641 642 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 643 /// of the input value to the specified type. If the type must be 644 /// extended, it is sign extended. 645 const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty); 646 647 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 648 /// the input value to the specified type. If the type must be extended, 649 /// it is zero extended. The conversion must not be narrowing. 650 const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty); 651 652 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 653 /// the input value to the specified type. If the type must be extended, 654 /// it is sign extended. The conversion must not be narrowing. 655 const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty); 656 657 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 658 /// the input value to the specified type. If the type must be extended, 659 /// it is extended with unspecified bits. The conversion must not be 660 /// narrowing. 661 const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty); 662 663 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 664 /// input value to the specified type. The conversion must not be 665 /// widening. 666 const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty); 667 668 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 669 /// the types using zero-extension, and then perform a umax operation 670 /// with them. 671 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 672 const SCEV *RHS); 673 674 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 675 /// the types using zero-extension, and then perform a umin operation 676 /// with them. 677 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 678 const SCEV *RHS); 679 680 /// getPointerBase - Transitively follow the chain of pointer-type operands 681 /// until reaching a SCEV that does not have a single pointer operand. This 682 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions, 683 /// but corner cases do exist. 684 const SCEV *getPointerBase(const SCEV *V); 685 686 /// getSCEVAtScope - Return a SCEV expression for the specified value 687 /// at the specified scope in the program. The L value specifies a loop 688 /// nest to evaluate the expression at, where null is the top-level or a 689 /// specified loop is immediately inside of the loop. 690 /// 691 /// This method can be used to compute the exit value for a variable defined 692 /// in a loop by querying what the value will hold in the parent loop. 693 /// 694 /// In the case that a relevant loop exit value cannot be computed, the 695 /// original value V is returned. 696 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 697 698 /// getSCEVAtScope - This is a convenience function which does 699 /// getSCEVAtScope(getSCEV(V), L). 700 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 701 702 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 703 /// by a conditional between LHS and RHS. This is used to help avoid max 704 /// expressions in loop trip counts, and to eliminate casts. 705 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 706 const SCEV *LHS, const SCEV *RHS); 707 708 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 709 /// protected by a conditional between LHS and RHS. This is used to 710 /// to eliminate casts. 711 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 712 const SCEV *LHS, const SCEV *RHS); 713 714 /// getSmallConstantTripCount - Returns the maximum trip count of this loop 715 /// as a normal unsigned value, if possible. Returns 0 if the trip count is 716 /// unknown or not constant. 717 unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitBlock); 718 719 /// getSmallConstantTripMultiple - Returns the largest constant divisor of 720 /// the trip count of this loop as a normal unsigned value, if 721 /// possible. This means that the actual trip count is always a multiple of 722 /// the returned value (don't forget the trip count could very well be zero 723 /// as well!). 724 unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitBlock); 725 726 // getExitCount - Get the expression for the number of loop iterations for 727 // which this loop is guaranteed not to exit via ExitingBlock. Otherwise 728 // return SCEVCouldNotCompute. 729 const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock); 730 731 /// getBackedgeTakenCount - If the specified loop has a predictable 732 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 733 /// object. The backedge-taken count is the number of times the loop header 734 /// will be branched to from within the loop. This is one less than the 735 /// trip count of the loop, since it doesn't count the first iteration, 736 /// when the header is branched to from outside the loop. 737 /// 738 /// Note that it is not valid to call this method on a loop without a 739 /// loop-invariant backedge-taken count (see 740 /// hasLoopInvariantBackedgeTakenCount). 741 /// 742 const SCEV *getBackedgeTakenCount(const Loop *L); 743 744 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 745 /// return the least SCEV value that is known never to be less than the 746 /// actual backedge taken count. 747 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 748 749 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 750 /// has an analyzable loop-invariant backedge-taken count. 751 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 752 753 /// forgetLoop - This method should be called by the client when it has 754 /// changed a loop in a way that may effect ScalarEvolution's ability to 755 /// compute a trip count, or if the loop is deleted. 756 void forgetLoop(const Loop *L); 757 758 /// forgetValue - This method should be called by the client when it has 759 /// changed a value in a way that may effect its value, or which may 760 /// disconnect it from a def-use chain linking it to a loop. 761 void forgetValue(Value *V); 762 763 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 764 /// is guaranteed to end in (at every loop iteration). It is, at the same 765 /// time, the minimum number of times S is divisible by 2. For example, 766 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 767 /// bitwidth of S. 768 uint32_t GetMinTrailingZeros(const SCEV *S); 769 770 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 771 /// 772 ConstantRange getUnsignedRange(const SCEV *S); 773 774 /// getSignedRange - Determine the signed range for a particular SCEV. 775 /// 776 ConstantRange getSignedRange(const SCEV *S); 777 778 /// isKnownNegative - Test if the given expression is known to be negative. 779 /// 780 bool isKnownNegative(const SCEV *S); 781 782 /// isKnownPositive - Test if the given expression is known to be positive. 783 /// 784 bool isKnownPositive(const SCEV *S); 785 786 /// isKnownNonNegative - Test if the given expression is known to be 787 /// non-negative. 788 /// 789 bool isKnownNonNegative(const SCEV *S); 790 791 /// isKnownNonPositive - Test if the given expression is known to be 792 /// non-positive. 793 /// 794 bool isKnownNonPositive(const SCEV *S); 795 796 /// isKnownNonZero - Test if the given expression is known to be 797 /// non-zero. 798 /// 799 bool isKnownNonZero(const SCEV *S); 800 801 /// isKnownPredicate - Test if the given expression is known to satisfy 802 /// the condition described by Pred, LHS, and RHS. 803 /// 804 bool isKnownPredicate(ICmpInst::Predicate Pred, 805 const SCEV *LHS, const SCEV *RHS); 806 807 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 808 /// predicate Pred. Return true iff any changes were made. If the 809 /// operands are provably equal or inequal, LHS and RHS are set to 810 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 811 /// 812 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 813 const SCEV *&LHS, 814 const SCEV *&RHS); 815 816 /// getLoopDisposition - Return the "disposition" of the given SCEV with 817 /// respect to the given loop. 818 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 819 820 /// isLoopInvariant - Return true if the value of the given SCEV is 821 /// unchanging in the specified loop. 822 bool isLoopInvariant(const SCEV *S, const Loop *L); 823 824 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 825 /// in a known way in the specified loop. This property being true implies 826 /// that the value is variant in the loop AND that we can emit an expression 827 /// to compute the value of the expression at any particular loop iteration. 828 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 829 830 /// getLoopDisposition - Return the "disposition" of the given SCEV with 831 /// respect to the given block. 832 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB); 833 834 /// dominates - Return true if elements that makes up the given SCEV 835 /// dominate the specified basic block. 836 bool dominates(const SCEV *S, const BasicBlock *BB); 837 838 /// properlyDominates - Return true if elements that makes up the given SCEV 839 /// properly dominate the specified basic block. 840 bool properlyDominates(const SCEV *S, const BasicBlock *BB); 841 842 /// hasOperand - Test whether the given SCEV has Op as a direct or 843 /// indirect operand. 844 bool hasOperand(const SCEV *S, const SCEV *Op) const; 845 846 virtual bool runOnFunction(Function &F); 847 virtual void releaseMemory(); 848 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 849 virtual void print(raw_ostream &OS, const Module* = 0) const; 850 851 private: 852 FoldingSet<SCEV> UniqueSCEVs; 853 BumpPtrAllocator SCEVAllocator; 854 855 /// FirstUnknown - The head of a linked list of all SCEVUnknown 856 /// values that have been allocated. This is used by releaseMemory 857 /// to locate them all and call their destructors. 858 SCEVUnknown *FirstUnknown; 859 }; 860} 861 862#endif 863