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/ADT/DenseSet.h" 25 #include "llvm/ADT/FoldingSet.h" 26 #include "llvm/IR/Function.h" 27 #include "llvm/IR/Instructions.h" 28 #include "llvm/IR/Operator.h" 29 #include "llvm/Pass.h" 30 #include "llvm/Support/Allocator.h" 31 #include "llvm/Support/ConstantRange.h" 32 #include "llvm/Support/DataTypes.h" 33 #include "llvm/Support/ValueHandle.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 DataLayout; 44 class TargetLibraryInfo; 45 class LLVMContext; 46 class Loop; 47 class LoopInfo; 48 class Operator; 49 class SCEVUnknown; 50 class SCEV; 51 template<> struct FoldingSetTrait<SCEV>; 52 53 /// SCEV - This class represents an analyzed expression in the program. These 54 /// are opaque objects that the client is not allowed to do much with 55 /// directly. 56 /// 57 class SCEV : public FoldingSetNode { 58 friend struct FoldingSetTrait<SCEV>; 59 60 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 61 /// The ScalarEvolution's BumpPtrAllocator holds the data. 62 FoldingSetNodeIDRef FastID; 63 64 // The SCEV baseclass this node corresponds to 65 const unsigned short SCEVType; 66 67 protected: 68 /// SubclassData - This field is initialized to zero and may be used in 69 /// subclasses to store miscellaneous information. 70 unsigned short SubclassData; 71 72 private: 73 SCEV(const SCEV &) LLVM_DELETED_FUNCTION; 74 void operator=(const SCEV &) LLVM_DELETED_FUNCTION; 75 76 public: 77 /// NoWrapFlags are bitfield indices into SubclassData. 78 /// 79 /// Add and Mul expressions may have no-unsigned-wrap <NUW> or 80 /// no-signed-wrap <NSW> properties, which are derived from the IR 81 /// operator. NSW is a misnomer that we use to mean no signed overflow or 82 /// underflow. 83 /// 84 /// AddRec expression may have a no-self-wraparound <NW> property if the 85 /// result can never reach the start value. This property is independent of 86 /// the actual start value and step direction. Self-wraparound is defined 87 /// purely in terms of the recurrence's loop, step size, and 88 /// bitwidth. Formally, a recurrence with no self-wraparound satisfies: 89 /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth). 90 /// 91 /// Note that NUW and NSW are also valid properties of a recurrence, and 92 /// either implies NW. For convenience, NW will be set for a recurrence 93 /// whenever either NUW or NSW are set. 94 enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee. 95 FlagNW = (1 << 0), // No self-wrap. 96 FlagNUW = (1 << 1), // No unsigned wrap. 97 FlagNSW = (1 << 2), // No signed wrap. 98 NoWrapMask = (1 << 3) -1 }; 99 100 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 101 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 102 103 unsigned getSCEVType() const { return SCEVType; } 104 105 /// getType - Return the LLVM type of this SCEV expression. 106 /// 107 Type *getType() const; 108 109 /// isZero - Return true if the expression is a constant zero. 110 /// 111 bool isZero() const; 112 113 /// isOne - Return true if the expression is a constant one. 114 /// 115 bool isOne() const; 116 117 /// isAllOnesValue - Return true if the expression is a constant 118 /// all-ones value. 119 /// 120 bool isAllOnesValue() const; 121 122 /// isNonConstantNegative - Return true if the specified scev is negated, 123 /// but not a constant. 124 bool isNonConstantNegative() const; 125 126 /// print - Print out the internal representation of this scalar to the 127 /// specified stream. This should really only be used for debugging 128 /// purposes. 129 void print(raw_ostream &OS) const; 130 131 /// dump - This method is used for debugging. 132 /// 133 void dump() const; 134 }; 135 136 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 137 // temporary FoldingSetNodeID values. 138 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 139 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 140 ID = X.FastID; 141 } 142 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 143 unsigned IDHash, FoldingSetNodeID &TempID) { 144 return ID == X.FastID; 145 } 146 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 147 return X.FastID.ComputeHash(); 148 } 149 }; 150 151 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 152 S.print(OS); 153 return OS; 154 } 155 156 /// SCEVCouldNotCompute - An object of this class is returned by queries that 157 /// could not be answered. For example, if you ask for the number of 158 /// iterations of a linked-list traversal loop, you will get one of these. 159 /// None of the standard SCEV operations are valid on this class, it is just a 160 /// marker. 161 struct SCEVCouldNotCompute : public SCEV { 162 SCEVCouldNotCompute(); 163 164 /// Methods for support type inquiry through isa, cast, and dyn_cast: 165 static bool classof(const SCEV *S); 166 }; 167 168 /// ScalarEvolution - This class is the main scalar evolution driver. Because 169 /// client code (intentionally) can't do much with the SCEV objects directly, 170 /// they must ask this class for services. 171 /// 172 class ScalarEvolution : public FunctionPass { 173 public: 174 /// LoopDisposition - An enum describing the relationship between a 175 /// SCEV and a loop. 176 enum LoopDisposition { 177 LoopVariant, ///< The SCEV is loop-variant (unknown). 178 LoopInvariant, ///< The SCEV is loop-invariant. 179 LoopComputable ///< The SCEV varies predictably with the loop. 180 }; 181 182 /// BlockDisposition - An enum describing the relationship between a 183 /// SCEV and a basic block. 184 enum BlockDisposition { 185 DoesNotDominateBlock, ///< The SCEV does not dominate the block. 186 DominatesBlock, ///< The SCEV dominates the block. 187 ProperlyDominatesBlock ///< The SCEV properly dominates the block. 188 }; 189 190 /// Convenient NoWrapFlags manipulation that hides enum casts and is 191 /// visible in the ScalarEvolution name space. 192 static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) { 193 return (SCEV::NoWrapFlags)(Flags & Mask); 194 } 195 static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags, 196 SCEV::NoWrapFlags OnFlags) { 197 return (SCEV::NoWrapFlags)(Flags | OnFlags); 198 } 199 static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags, 200 SCEV::NoWrapFlags OffFlags) { 201 return (SCEV::NoWrapFlags)(Flags & ~OffFlags); 202 } 203 204 private: 205 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 206 /// notified whenever a Value is deleted. 207 class SCEVCallbackVH : public CallbackVH { 208 ScalarEvolution *SE; 209 virtual void deleted(); 210 virtual void allUsesReplacedWith(Value *New); 211 public: 212 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 213 }; 214 215 friend class SCEVCallbackVH; 216 friend class SCEVExpander; 217 friend class SCEVUnknown; 218 219 /// F - The function we are analyzing. 220 /// 221 Function *F; 222 223 /// LI - The loop information for the function we are currently analyzing. 224 /// 225 LoopInfo *LI; 226 227 /// TD - The target data information for the target we are targeting. 228 /// 229 DataLayout *TD; 230 231 /// TLI - The target library information for the target we are targeting. 232 /// 233 TargetLibraryInfo *TLI; 234 235 /// DT - The dominator tree. 236 /// 237 DominatorTree *DT; 238 239 /// CouldNotCompute - This SCEV is used to represent unknown trip 240 /// counts and things. 241 SCEVCouldNotCompute CouldNotCompute; 242 243 /// ValueExprMapType - The typedef for ValueExprMap. 244 /// 245 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 246 ValueExprMapType; 247 248 /// ValueExprMap - This is a cache of the values we have analyzed so far. 249 /// 250 ValueExprMapType ValueExprMap; 251 252 /// Mark predicate values currently being processed by isImpliedCond. 253 DenseSet<Value*> PendingLoopPredicates; 254 255 /// ExitLimit - Information about the number of loop iterations for 256 /// which a loop exit's branch condition evaluates to the not-taken path. 257 /// This is a temporary pair of exact and max expressions that are 258 /// eventually summarized in ExitNotTakenInfo and BackedgeTakenInfo. 259 struct ExitLimit { 260 const SCEV *Exact; 261 const SCEV *Max; 262 263 /*implicit*/ ExitLimit(const SCEV *E) : Exact(E), Max(E) {} 264 265 ExitLimit(const SCEV *E, const SCEV *M) : Exact(E), Max(M) {} 266 267 /// hasAnyInfo - Test whether this ExitLimit contains any computed 268 /// information, or whether it's all SCEVCouldNotCompute values. 269 bool hasAnyInfo() const { 270 return !isa<SCEVCouldNotCompute>(Exact) || 271 !isa<SCEVCouldNotCompute>(Max); 272 } 273 }; 274 275 /// ExitNotTakenInfo - Information about the number of times a particular 276 /// loop exit may be reached before exiting the loop. 277 struct ExitNotTakenInfo { 278 AssertingVH<BasicBlock> ExitingBlock; 279 const SCEV *ExactNotTaken; 280 PointerIntPair<ExitNotTakenInfo*, 1> NextExit; 281 282 ExitNotTakenInfo() : ExitingBlock(0), ExactNotTaken(0) {} 283 284 /// isCompleteList - Return true if all loop exits are computable. 285 bool isCompleteList() const { 286 return NextExit.getInt() == 0; 287 } 288 289 void setIncomplete() { NextExit.setInt(1); } 290 291 /// getNextExit - Return a pointer to the next exit's not-taken info. 292 ExitNotTakenInfo *getNextExit() const { 293 return NextExit.getPointer(); 294 } 295 296 void setNextExit(ExitNotTakenInfo *ENT) { NextExit.setPointer(ENT); } 297 }; 298 299 /// BackedgeTakenInfo - Information about the backedge-taken count 300 /// of a loop. This currently includes an exact count and a maximum count. 301 /// 302 class BackedgeTakenInfo { 303 /// ExitNotTaken - A list of computable exits and their not-taken counts. 304 /// Loops almost never have more than one computable exit. 305 ExitNotTakenInfo ExitNotTaken; 306 307 /// Max - An expression indicating the least maximum backedge-taken 308 /// count of the loop that is known, or a SCEVCouldNotCompute. 309 const SCEV *Max; 310 311 public: 312 BackedgeTakenInfo() : Max(0) {} 313 314 /// Initialize BackedgeTakenInfo from a list of exact exit counts. 315 BackedgeTakenInfo( 316 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts, 317 bool Complete, const SCEV *MaxCount); 318 319 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 320 /// computed information, or whether it's all SCEVCouldNotCompute 321 /// values. 322 bool hasAnyInfo() const { 323 return ExitNotTaken.ExitingBlock || !isa<SCEVCouldNotCompute>(Max); 324 } 325 326 /// getExact - Return an expression indicating the exact backedge-taken 327 /// count of the loop if it is known, or SCEVCouldNotCompute 328 /// otherwise. This is the number of times the loop header can be 329 /// guaranteed to execute, minus one. 330 const SCEV *getExact(ScalarEvolution *SE) const; 331 332 /// getExact - Return the number of times this loop exit may fall through 333 /// to the back edge, or SCEVCouldNotCompute. The loop is guaranteed not 334 /// to exit via this block before this number of iterations, but may exit 335 /// via another block. 336 const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const; 337 338 /// getMax - Get the max backedge taken count for the loop. 339 const SCEV *getMax(ScalarEvolution *SE) const; 340 341 /// Return true if any backedge taken count expressions refer to the given 342 /// subexpression. 343 bool hasOperand(const SCEV *S, ScalarEvolution *SE) const; 344 345 /// clear - Invalidate this result and free associated memory. 346 void clear(); 347 }; 348 349 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 350 /// this function as they are computed. 351 DenseMap<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 352 353 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 354 /// the PHI instructions that we attempt to compute constant evolutions for. 355 /// This allows us to avoid potentially expensive recomputation of these 356 /// properties. An instruction maps to null if we are unable to compute its 357 /// exit value. 358 DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 359 360 /// ValuesAtScopes - This map contains entries for all the expressions 361 /// that we attempt to compute getSCEVAtScope information for, which can 362 /// be expensive in extreme cases. 363 DenseMap<const SCEV *, 364 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 365 366 /// LoopDispositions - Memoized computeLoopDisposition results. 367 DenseMap<const SCEV *, 368 std::map<const Loop *, LoopDisposition> > LoopDispositions; 369 370 /// computeLoopDisposition - Compute a LoopDisposition value. 371 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 372 373 /// BlockDispositions - Memoized computeBlockDisposition results. 374 DenseMap<const SCEV *, 375 std::map<const BasicBlock *, BlockDisposition> > BlockDispositions; 376 377 /// computeBlockDisposition - Compute a BlockDisposition value. 378 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB); 379 380 /// UnsignedRanges - Memoized results from getUnsignedRange 381 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 382 383 /// SignedRanges - Memoized results from getSignedRange 384 DenseMap<const SCEV *, ConstantRange> SignedRanges; 385 386 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 387 const ConstantRange &setUnsignedRange(const SCEV *S, 388 const ConstantRange &CR) { 389 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 390 UnsignedRanges.insert(std::make_pair(S, CR)); 391 if (!Pair.second) 392 Pair.first->second = CR; 393 return Pair.first->second; 394 } 395 396 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 397 const ConstantRange &setSignedRange(const SCEV *S, 398 const ConstantRange &CR) { 399 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 400 SignedRanges.insert(std::make_pair(S, CR)); 401 if (!Pair.second) 402 Pair.first->second = CR; 403 return Pair.first->second; 404 } 405 406 /// createSCEV - We know that there is no SCEV for the specified value. 407 /// Analyze the expression. 408 const SCEV *createSCEV(Value *V); 409 410 /// createNodeForPHI - Provide the special handling we need to analyze PHI 411 /// SCEVs. 412 const SCEV *createNodeForPHI(PHINode *PN); 413 414 /// createNodeForGEP - Provide the special handling we need to analyze GEP 415 /// SCEVs. 416 const SCEV *createNodeForGEP(GEPOperator *GEP); 417 418 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 419 /// at most once for each SCEV+Loop pair. 420 /// 421 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 422 423 /// ForgetSymbolicValue - This looks up computed SCEV values for all 424 /// instructions that depend on the given instruction and removes them from 425 /// the ValueExprMap map if they reference SymName. This is used during PHI 426 /// resolution. 427 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 428 429 /// getBECount - Subtract the end and start values and divide by the step, 430 /// rounding up, to get the number of times the backedge is executed. Return 431 /// CouldNotCompute if an intermediate computation overflows. 432 const SCEV *getBECount(const SCEV *Start, 433 const SCEV *End, 434 const SCEV *Step, 435 bool NoWrap); 436 437 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 438 /// loop, lazily computing new values if the loop hasn't been analyzed 439 /// yet. 440 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 441 442 /// ComputeBackedgeTakenCount - Compute the number of times the specified 443 /// loop will iterate. 444 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 445 446 /// ComputeExitLimit - Compute the number of times the backedge of the 447 /// specified loop will execute if it exits via the specified block. 448 ExitLimit ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock); 449 450 /// ComputeExitLimitFromCond - Compute the number of times the backedge of 451 /// the specified loop will execute if its exit condition were a conditional 452 /// branch of ExitCond, TBB, and FBB. 453 ExitLimit ComputeExitLimitFromCond(const Loop *L, 454 Value *ExitCond, 455 BasicBlock *TBB, 456 BasicBlock *FBB, 457 bool IsSubExpr); 458 459 /// ComputeExitLimitFromICmp - Compute the number of times the backedge of 460 /// the specified loop will execute if its exit condition were a conditional 461 /// branch of the ICmpInst ExitCond, TBB, and FBB. 462 ExitLimit ComputeExitLimitFromICmp(const Loop *L, 463 ICmpInst *ExitCond, 464 BasicBlock *TBB, 465 BasicBlock *FBB, 466 bool IsSubExpr); 467 468 /// ComputeLoadConstantCompareExitLimit - Given an exit condition 469 /// of 'icmp op load X, cst', try to see if we can compute the 470 /// backedge-taken count. 471 ExitLimit ComputeLoadConstantCompareExitLimit(LoadInst *LI, 472 Constant *RHS, 473 const Loop *L, 474 ICmpInst::Predicate p); 475 476 /// ComputeExitCountExhaustively - If the loop is known to execute a 477 /// constant number of times (the condition evolves only from constants), 478 /// try to evaluate a few iterations of the loop until we get the exit 479 /// condition gets a value of ExitWhen (true or false). If we cannot 480 /// evaluate the exit count of the loop, return CouldNotCompute. 481 const SCEV *ComputeExitCountExhaustively(const Loop *L, 482 Value *Cond, 483 bool ExitWhen); 484 485 /// HowFarToZero - Return the number of times an exit condition comparing 486 /// the specified value to zero will execute. If not computable, return 487 /// CouldNotCompute. 488 ExitLimit HowFarToZero(const SCEV *V, const Loop *L, bool IsSubExpr); 489 490 /// HowFarToNonZero - Return the number of times an exit condition checking 491 /// the specified value for nonzero will execute. If not computable, return 492 /// CouldNotCompute. 493 ExitLimit HowFarToNonZero(const SCEV *V, const Loop *L); 494 495 /// HowManyLessThans - Return the number of times an exit condition 496 /// containing the specified less-than comparison will execute. If not 497 /// computable, return CouldNotCompute. isSigned specifies whether the 498 /// less-than is signed. 499 ExitLimit HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 500 const Loop *L, bool isSigned, bool IsSubExpr); 501 502 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 503 /// (which may not be an immediate predecessor) which has exactly one 504 /// successor from which BB is reachable, or null if no such block is 505 /// found. 506 std::pair<BasicBlock *, BasicBlock *> 507 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 508 509 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 510 /// RHS is true whenever the given FoundCondValue value evaluates to true. 511 bool isImpliedCond(ICmpInst::Predicate Pred, 512 const SCEV *LHS, const SCEV *RHS, 513 Value *FoundCondValue, 514 bool Inverse); 515 516 /// isImpliedCondOperands - Test whether the condition described by Pred, 517 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 518 /// and FoundRHS is true. 519 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 520 const SCEV *LHS, const SCEV *RHS, 521 const SCEV *FoundLHS, const SCEV *FoundRHS); 522 523 /// isImpliedCondOperandsHelper - Test whether the condition described by 524 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 525 /// FoundLHS, and FoundRHS is true. 526 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 527 const SCEV *LHS, const SCEV *RHS, 528 const SCEV *FoundLHS, 529 const SCEV *FoundRHS); 530 531 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 532 /// in the header of its containing loop, we know the loop executes a 533 /// constant number of times, and the PHI node is just a recurrence 534 /// involving constants, fold it. 535 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 536 const Loop *L); 537 538 /// isKnownPredicateWithRanges - Test if the given expression is known to 539 /// satisfy the condition described by Pred and the known constant ranges 540 /// of LHS and RHS. 541 /// 542 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 543 const SCEV *LHS, const SCEV *RHS); 544 545 /// forgetMemoizedResults - Drop memoized information computed for S. 546 void forgetMemoizedResults(const SCEV *S); 547 548 /// Return false iff given SCEV contains a SCEVUnknown with NULL value- 549 /// pointer. 550 bool checkValidity(const SCEV *S) const; 551 552 public: 553 static char ID; // Pass identification, replacement for typeid 554 ScalarEvolution(); 555 556 LLVMContext &getContext() const { return F->getContext(); } 557 558 /// isSCEVable - Test if values of the given type are analyzable within 559 /// the SCEV framework. This primarily includes integer types, and it 560 /// can optionally include pointer types if the ScalarEvolution class 561 /// has access to target-specific information. 562 bool isSCEVable(Type *Ty) const; 563 564 /// getTypeSizeInBits - Return the size in bits of the specified type, 565 /// for which isSCEVable must return true. 566 uint64_t getTypeSizeInBits(Type *Ty) const; 567 568 /// getEffectiveSCEVType - Return a type with the same bitwidth as 569 /// the given type and which represents how SCEV will treat the given 570 /// type, for which isSCEVable must return true. For pointer types, 571 /// this is the pointer-sized integer type. 572 Type *getEffectiveSCEVType(Type *Ty) const; 573 574 /// getSCEV - Return a SCEV expression for the full generality of the 575 /// specified expression. 576 const SCEV *getSCEV(Value *V); 577 578 const SCEV *getConstant(ConstantInt *V); 579 const SCEV *getConstant(const APInt& Val); 580 const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false); 581 const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty); 582 const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty); 583 const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty); 584 const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty); 585 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 586 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 587 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 588 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 589 SmallVector<const SCEV *, 2> Ops; 590 Ops.push_back(LHS); 591 Ops.push_back(RHS); 592 return getAddExpr(Ops, Flags); 593 } 594 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 595 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 596 SmallVector<const SCEV *, 3> Ops; 597 Ops.push_back(Op0); 598 Ops.push_back(Op1); 599 Ops.push_back(Op2); 600 return getAddExpr(Ops, Flags); 601 } 602 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 603 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 604 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 605 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) 606 { 607 SmallVector<const SCEV *, 2> Ops; 608 Ops.push_back(LHS); 609 Ops.push_back(RHS); 610 return getMulExpr(Ops, Flags); 611 } 612 const SCEV *getMulExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 613 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 614 SmallVector<const SCEV *, 3> Ops; 615 Ops.push_back(Op0); 616 Ops.push_back(Op1); 617 Ops.push_back(Op2); 618 return getMulExpr(Ops, Flags); 619 } 620 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 621 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 622 const Loop *L, SCEV::NoWrapFlags Flags); 623 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 624 const Loop *L, SCEV::NoWrapFlags Flags); 625 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 626 const Loop *L, SCEV::NoWrapFlags Flags) { 627 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 628 return getAddRecExpr(NewOp, L, Flags); 629 } 630 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 631 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 632 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 633 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 634 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 635 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 636 const SCEV *getUnknown(Value *V); 637 const SCEV *getCouldNotCompute(); 638 639 /// getSizeOfExpr - Return an expression for sizeof on the given type. 640 /// 641 const SCEV *getSizeOfExpr(Type *AllocTy); 642 643 /// getAlignOfExpr - Return an expression for alignof on the given type. 644 /// 645 const SCEV *getAlignOfExpr(Type *AllocTy); 646 647 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 648 /// 649 const SCEV *getOffsetOfExpr(StructType *STy, unsigned FieldNo); 650 651 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 652 /// 653 const SCEV *getOffsetOfExpr(Type *CTy, Constant *FieldNo); 654 655 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 656 /// 657 const SCEV *getNegativeSCEV(const SCEV *V); 658 659 /// getNotSCEV - Return the SCEV object corresponding to ~V. 660 /// 661 const SCEV *getNotSCEV(const SCEV *V); 662 663 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1. 664 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS, 665 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 666 667 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 668 /// of the input value to the specified type. If the type must be 669 /// extended, it is zero extended. 670 const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty); 671 672 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 673 /// of the input value to the specified type. If the type must be 674 /// extended, it is sign extended. 675 const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty); 676 677 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 678 /// the input value to the specified type. If the type must be extended, 679 /// it is zero extended. The conversion must not be narrowing. 680 const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty); 681 682 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 683 /// the input value to the specified type. If the type must be extended, 684 /// it is sign extended. The conversion must not be narrowing. 685 const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty); 686 687 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 688 /// the input value to the specified type. If the type must be extended, 689 /// it is extended with unspecified bits. The conversion must not be 690 /// narrowing. 691 const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty); 692 693 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 694 /// input value to the specified type. The conversion must not be 695 /// widening. 696 const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty); 697 698 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 699 /// the types using zero-extension, and then perform a umax operation 700 /// with them. 701 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 702 const SCEV *RHS); 703 704 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 705 /// the types using zero-extension, and then perform a umin operation 706 /// with them. 707 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 708 const SCEV *RHS); 709 710 /// getPointerBase - Transitively follow the chain of pointer-type operands 711 /// until reaching a SCEV that does not have a single pointer operand. This 712 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions, 713 /// but corner cases do exist. 714 const SCEV *getPointerBase(const SCEV *V); 715 716 /// getSCEVAtScope - Return a SCEV expression for the specified value 717 /// at the specified scope in the program. The L value specifies a loop 718 /// nest to evaluate the expression at, where null is the top-level or a 719 /// specified loop is immediately inside of the loop. 720 /// 721 /// This method can be used to compute the exit value for a variable defined 722 /// in a loop by querying what the value will hold in the parent loop. 723 /// 724 /// In the case that a relevant loop exit value cannot be computed, the 725 /// original value V is returned. 726 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 727 728 /// getSCEVAtScope - This is a convenience function which does 729 /// getSCEVAtScope(getSCEV(V), L). 730 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 731 732 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 733 /// by a conditional between LHS and RHS. This is used to help avoid max 734 /// expressions in loop trip counts, and to eliminate casts. 735 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 736 const SCEV *LHS, const SCEV *RHS); 737 738 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 739 /// protected by a conditional between LHS and RHS. This is used to 740 /// to eliminate casts. 741 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 742 const SCEV *LHS, const SCEV *RHS); 743 744 /// getSmallConstantTripCount - Returns the maximum trip count of this loop 745 /// as a normal unsigned value. Returns 0 if the trip count is unknown or 746 /// not constant. This "trip count" assumes that control exits via 747 /// ExitingBlock. More precisely, it is the number of times that control may 748 /// reach ExitingBlock before taking the branch. For loops with multiple 749 /// exits, it may not be the number times that the loop header executes if 750 /// the loop exits prematurely via another branch. 751 unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitingBlock); 752 753 /// getSmallConstantTripMultiple - Returns the largest constant divisor of 754 /// the trip count of this loop as a normal unsigned value, if 755 /// possible. This means that the actual trip count is always a multiple of 756 /// the returned value (don't forget the trip count could very well be zero 757 /// as well!). As explained in the comments for getSmallConstantTripCount, 758 /// this assumes that control exits the loop via ExitingBlock. 759 unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitingBlock); 760 761 // getExitCount - Get the expression for the number of loop iterations for 762 // which this loop is guaranteed not to exit via ExitingBlock. Otherwise 763 // return SCEVCouldNotCompute. 764 const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock); 765 766 /// getBackedgeTakenCount - If the specified loop has a predictable 767 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 768 /// object. The backedge-taken count is the number of times the loop header 769 /// will be branched to from within the loop. This is one less than the 770 /// trip count of the loop, since it doesn't count the first iteration, 771 /// when the header is branched to from outside the loop. 772 /// 773 /// Note that it is not valid to call this method on a loop without a 774 /// loop-invariant backedge-taken count (see 775 /// hasLoopInvariantBackedgeTakenCount). 776 /// 777 const SCEV *getBackedgeTakenCount(const Loop *L); 778 779 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 780 /// return the least SCEV value that is known never to be less than the 781 /// actual backedge taken count. 782 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 783 784 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 785 /// has an analyzable loop-invariant backedge-taken count. 786 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 787 788 /// forgetLoop - This method should be called by the client when it has 789 /// changed a loop in a way that may effect ScalarEvolution's ability to 790 /// compute a trip count, or if the loop is deleted. 791 void forgetLoop(const Loop *L); 792 793 /// forgetValue - This method should be called by the client when it has 794 /// changed a value in a way that may effect its value, or which may 795 /// disconnect it from a def-use chain linking it to a loop. 796 void forgetValue(Value *V); 797 798 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 799 /// is guaranteed to end in (at every loop iteration). It is, at the same 800 /// time, the minimum number of times S is divisible by 2. For example, 801 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 802 /// bitwidth of S. 803 uint32_t GetMinTrailingZeros(const SCEV *S); 804 805 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 806 /// 807 ConstantRange getUnsignedRange(const SCEV *S); 808 809 /// getSignedRange - Determine the signed range for a particular SCEV. 810 /// 811 ConstantRange getSignedRange(const SCEV *S); 812 813 /// isKnownNegative - Test if the given expression is known to be negative. 814 /// 815 bool isKnownNegative(const SCEV *S); 816 817 /// isKnownPositive - Test if the given expression is known to be positive. 818 /// 819 bool isKnownPositive(const SCEV *S); 820 821 /// isKnownNonNegative - Test if the given expression is known to be 822 /// non-negative. 823 /// 824 bool isKnownNonNegative(const SCEV *S); 825 826 /// isKnownNonPositive - Test if the given expression is known to be 827 /// non-positive. 828 /// 829 bool isKnownNonPositive(const SCEV *S); 830 831 /// isKnownNonZero - Test if the given expression is known to be 832 /// non-zero. 833 /// 834 bool isKnownNonZero(const SCEV *S); 835 836 /// isKnownPredicate - Test if the given expression is known to satisfy 837 /// the condition described by Pred, LHS, and RHS. 838 /// 839 bool isKnownPredicate(ICmpInst::Predicate Pred, 840 const SCEV *LHS, const SCEV *RHS); 841 842 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 843 /// predicate Pred. Return true iff any changes were made. If the 844 /// operands are provably equal or unequal, LHS and RHS are set to 845 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 846 /// 847 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 848 const SCEV *&LHS, 849 const SCEV *&RHS, 850 unsigned Depth = 0); 851 852 /// getLoopDisposition - Return the "disposition" of the given SCEV with 853 /// respect to the given loop. 854 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 855 856 /// isLoopInvariant - Return true if the value of the given SCEV is 857 /// unchanging in the specified loop. 858 bool isLoopInvariant(const SCEV *S, const Loop *L); 859 860 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 861 /// in a known way in the specified loop. This property being true implies 862 /// that the value is variant in the loop AND that we can emit an expression 863 /// to compute the value of the expression at any particular loop iteration. 864 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 865 866 /// getLoopDisposition - Return the "disposition" of the given SCEV with 867 /// respect to the given block. 868 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB); 869 870 /// dominates - Return true if elements that makes up the given SCEV 871 /// dominate the specified basic block. 872 bool dominates(const SCEV *S, const BasicBlock *BB); 873 874 /// properlyDominates - Return true if elements that makes up the given SCEV 875 /// properly dominate the specified basic block. 876 bool properlyDominates(const SCEV *S, const BasicBlock *BB); 877 878 /// hasOperand - Test whether the given SCEV has Op as a direct or 879 /// indirect operand. 880 bool hasOperand(const SCEV *S, const SCEV *Op) const; 881 882 virtual bool runOnFunction(Function &F); 883 virtual void releaseMemory(); 884 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 885 virtual void print(raw_ostream &OS, const Module* = 0) const; 886 virtual void verifyAnalysis() const; 887 888 private: 889 FoldingSet<SCEV> UniqueSCEVs; 890 BumpPtrAllocator SCEVAllocator; 891 892 /// FirstUnknown - The head of a linked list of all SCEVUnknown 893 /// values that have been allocated. This is used by releaseMemory 894 /// to locate them all and call their destructors. 895 SCEVUnknown *FirstUnknown; 896 }; 897 } 898 899 #endif 900
