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/ConstantRange.h" 27 #include "llvm/IR/Function.h" 28 #include "llvm/IR/Instructions.h" 29 #include "llvm/IR/Operator.h" 30 #include "llvm/IR/ValueHandle.h" 31 #include "llvm/Pass.h" 32 #include "llvm/Support/Allocator.h" 33 #include "llvm/Support/DataTypes.h" 34 #include <map> 35 36 namespace llvm { 37 class APInt; 38 class AssumptionCache; 39 class Constant; 40 class ConstantInt; 41 class DominatorTree; 42 class Type; 43 class ScalarEvolution; 44 class DataLayout; 45 class TargetLibraryInfo; 46 class LLVMContext; 47 class Loop; 48 class LoopInfo; 49 class Operator; 50 class SCEVUnknown; 51 class SCEV; 52 template<> struct FoldingSetTrait<SCEV>; 53 54 /// SCEV - This class represents an analyzed expression in the program. These 55 /// are opaque objects that the client is not allowed to do much with 56 /// directly. 57 /// 58 class SCEV : public FoldingSetNode { 59 friend struct FoldingSetTrait<SCEV>; 60 61 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 62 /// The ScalarEvolution's BumpPtrAllocator holds the data. 63 FoldingSetNodeIDRef FastID; 64 65 // The SCEV baseclass this node corresponds to 66 const unsigned short SCEVType; 67 68 protected: 69 /// SubclassData - This field is initialized to zero and may be used in 70 /// subclasses to store miscellaneous information. 71 unsigned short SubclassData; 72 73 private: 74 SCEV(const SCEV &) LLVM_DELETED_FUNCTION; 75 void operator=(const SCEV &) LLVM_DELETED_FUNCTION; 76 77 public: 78 /// NoWrapFlags are bitfield indices into SubclassData. 79 /// 80 /// Add and Mul expressions may have no-unsigned-wrap <NUW> or 81 /// no-signed-wrap <NSW> properties, which are derived from the IR 82 /// operator. NSW is a misnomer that we use to mean no signed overflow or 83 /// underflow. 84 /// 85 /// AddRec expression may have a no-self-wraparound <NW> property if the 86 /// result can never reach the start value. This property is independent of 87 /// the actual start value and step direction. Self-wraparound is defined 88 /// purely in terms of the recurrence's loop, step size, and 89 /// bitwidth. Formally, a recurrence with no self-wraparound satisfies: 90 /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth). 91 /// 92 /// Note that NUW and NSW are also valid properties of a recurrence, and 93 /// either implies NW. For convenience, NW will be set for a recurrence 94 /// whenever either NUW or NSW are set. 95 enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee. 96 FlagNW = (1 << 0), // No self-wrap. 97 FlagNUW = (1 << 1), // No unsigned wrap. 98 FlagNSW = (1 << 2), // No signed wrap. 99 NoWrapMask = (1 << 3) -1 }; 100 101 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 102 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 103 104 unsigned getSCEVType() const { return SCEVType; } 105 106 /// getType - Return the LLVM type of this SCEV expression. 107 /// 108 Type *getType() const; 109 110 /// isZero - Return true if the expression is a constant zero. 111 /// 112 bool isZero() const; 113 114 /// isOne - Return true if the expression is a constant one. 115 /// 116 bool isOne() const; 117 118 /// isAllOnesValue - Return true if the expression is a constant 119 /// all-ones value. 120 /// 121 bool isAllOnesValue() const; 122 123 /// isNonConstantNegative - Return true if the specified scev is negated, 124 /// but not a constant. 125 bool isNonConstantNegative() const; 126 127 /// print - Print out the internal representation of this scalar to the 128 /// specified stream. This should really only be used for debugging 129 /// purposes. 130 void print(raw_ostream &OS) const; 131 132 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 133 /// dump - This method is used for debugging. 134 /// 135 void dump() const; 136 #endif 137 }; 138 139 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 140 // temporary FoldingSetNodeID values. 141 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 142 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 143 ID = X.FastID; 144 } 145 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 146 unsigned IDHash, FoldingSetNodeID &TempID) { 147 return ID == X.FastID; 148 } 149 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 150 return X.FastID.ComputeHash(); 151 } 152 }; 153 154 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 155 S.print(OS); 156 return OS; 157 } 158 159 /// SCEVCouldNotCompute - An object of this class is returned by queries that 160 /// could not be answered. For example, if you ask for the number of 161 /// iterations of a linked-list traversal loop, you will get one of these. 162 /// None of the standard SCEV operations are valid on this class, it is just a 163 /// marker. 164 struct SCEVCouldNotCompute : public SCEV { 165 SCEVCouldNotCompute(); 166 167 /// Methods for support type inquiry through isa, cast, and dyn_cast: 168 static bool classof(const SCEV *S); 169 }; 170 171 /// ScalarEvolution - This class is the main scalar evolution driver. Because 172 /// client code (intentionally) can't do much with the SCEV objects directly, 173 /// they must ask this class for services. 174 /// 175 class ScalarEvolution : public FunctionPass { 176 public: 177 /// LoopDisposition - An enum describing the relationship between a 178 /// SCEV and a loop. 179 enum LoopDisposition { 180 LoopVariant, ///< The SCEV is loop-variant (unknown). 181 LoopInvariant, ///< The SCEV is loop-invariant. 182 LoopComputable ///< The SCEV varies predictably with the loop. 183 }; 184 185 /// BlockDisposition - An enum describing the relationship between a 186 /// SCEV and a basic block. 187 enum BlockDisposition { 188 DoesNotDominateBlock, ///< The SCEV does not dominate the block. 189 DominatesBlock, ///< The SCEV dominates the block. 190 ProperlyDominatesBlock ///< The SCEV properly dominates the block. 191 }; 192 193 /// Convenient NoWrapFlags manipulation that hides enum casts and is 194 /// visible in the ScalarEvolution name space. 195 static SCEV::NoWrapFlags LLVM_ATTRIBUTE_UNUSED_RESULT 196 maskFlags(SCEV::NoWrapFlags Flags, int Mask) { 197 return (SCEV::NoWrapFlags)(Flags & Mask); 198 } 199 static SCEV::NoWrapFlags LLVM_ATTRIBUTE_UNUSED_RESULT 200 setFlags(SCEV::NoWrapFlags Flags, SCEV::NoWrapFlags OnFlags) { 201 return (SCEV::NoWrapFlags)(Flags | OnFlags); 202 } 203 static SCEV::NoWrapFlags LLVM_ATTRIBUTE_UNUSED_RESULT 204 clearFlags(SCEV::NoWrapFlags Flags, SCEV::NoWrapFlags OffFlags) { 205 return (SCEV::NoWrapFlags)(Flags & ~OffFlags); 206 } 207 208 private: 209 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 210 /// notified whenever a Value is deleted. 211 class SCEVCallbackVH : public CallbackVH { 212 ScalarEvolution *SE; 213 void deleted() override; 214 void allUsesReplacedWith(Value *New) override; 215 public: 216 SCEVCallbackVH(Value *V, ScalarEvolution *SE = nullptr); 217 }; 218 219 friend class SCEVCallbackVH; 220 friend class SCEVExpander; 221 friend class SCEVUnknown; 222 223 /// F - The function we are analyzing. 224 /// 225 Function *F; 226 227 /// The tracker for @llvm.assume intrinsics in this function. 228 AssumptionCache *AC; 229 230 /// LI - The loop information for the function we are currently analyzing. 231 /// 232 LoopInfo *LI; 233 234 /// The DataLayout information for the target we are targeting. 235 /// 236 const DataLayout *DL; 237 238 /// TLI - The target library information for the target we are targeting. 239 /// 240 TargetLibraryInfo *TLI; 241 242 /// DT - The dominator tree. 243 /// 244 DominatorTree *DT; 245 246 /// CouldNotCompute - This SCEV is used to represent unknown trip 247 /// counts and things. 248 SCEVCouldNotCompute CouldNotCompute; 249 250 /// ValueExprMapType - The typedef for ValueExprMap. 251 /// 252 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 253 ValueExprMapType; 254 255 /// ValueExprMap - This is a cache of the values we have analyzed so far. 256 /// 257 ValueExprMapType ValueExprMap; 258 259 /// Mark predicate values currently being processed by isImpliedCond. 260 DenseSet<Value*> PendingLoopPredicates; 261 262 /// ExitLimit - Information about the number of loop iterations for which a 263 /// loop exit's branch condition evaluates to the not-taken path. This is a 264 /// temporary pair of exact and max expressions that are eventually 265 /// summarized in ExitNotTakenInfo and BackedgeTakenInfo. 266 struct ExitLimit { 267 const SCEV *Exact; 268 const SCEV *Max; 269 270 /*implicit*/ ExitLimit(const SCEV *E) : Exact(E), Max(E) {} 271 272 ExitLimit(const SCEV *E, const SCEV *M) : Exact(E), Max(M) {} 273 274 /// hasAnyInfo - Test whether this ExitLimit contains any computed 275 /// information, or whether it's all SCEVCouldNotCompute values. 276 bool hasAnyInfo() const { 277 return !isa<SCEVCouldNotCompute>(Exact) || 278 !isa<SCEVCouldNotCompute>(Max); 279 } 280 }; 281 282 /// ExitNotTakenInfo - Information about the number of times a particular 283 /// loop exit may be reached before exiting the loop. 284 struct ExitNotTakenInfo { 285 AssertingVH<BasicBlock> ExitingBlock; 286 const SCEV *ExactNotTaken; 287 PointerIntPair<ExitNotTakenInfo*, 1> NextExit; 288 289 ExitNotTakenInfo() : ExitingBlock(nullptr), ExactNotTaken(nullptr) {} 290 291 /// isCompleteList - Return true if all loop exits are computable. 292 bool isCompleteList() const { 293 return NextExit.getInt() == 0; 294 } 295 296 void setIncomplete() { NextExit.setInt(1); } 297 298 /// getNextExit - Return a pointer to the next exit's not-taken info. 299 ExitNotTakenInfo *getNextExit() const { 300 return NextExit.getPointer(); 301 } 302 303 void setNextExit(ExitNotTakenInfo *ENT) { NextExit.setPointer(ENT); } 304 }; 305 306 /// BackedgeTakenInfo - Information about the backedge-taken count 307 /// of a loop. This currently includes an exact count and a maximum count. 308 /// 309 class BackedgeTakenInfo { 310 /// ExitNotTaken - A list of computable exits and their not-taken counts. 311 /// Loops almost never have more than one computable exit. 312 ExitNotTakenInfo ExitNotTaken; 313 314 /// Max - An expression indicating the least maximum backedge-taken 315 /// count of the loop that is known, or a SCEVCouldNotCompute. 316 const SCEV *Max; 317 318 public: 319 BackedgeTakenInfo() : Max(nullptr) {} 320 321 /// Initialize BackedgeTakenInfo from a list of exact exit counts. 322 BackedgeTakenInfo( 323 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts, 324 bool Complete, const SCEV *MaxCount); 325 326 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 327 /// computed information, or whether it's all SCEVCouldNotCompute 328 /// values. 329 bool hasAnyInfo() const { 330 return ExitNotTaken.ExitingBlock || !isa<SCEVCouldNotCompute>(Max); 331 } 332 333 /// getExact - Return an expression indicating the exact backedge-taken 334 /// count of the loop if it is known, or SCEVCouldNotCompute 335 /// otherwise. This is the number of times the loop header can be 336 /// guaranteed to execute, minus one. 337 const SCEV *getExact(ScalarEvolution *SE) const; 338 339 /// getExact - Return the number of times this loop exit may fall through 340 /// to the back edge, or SCEVCouldNotCompute. The loop is guaranteed not 341 /// to exit via this block before this number of iterations, but may exit 342 /// via another block. 343 const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const; 344 345 /// getMax - Get the max backedge taken count for the loop. 346 const SCEV *getMax(ScalarEvolution *SE) const; 347 348 /// Return true if any backedge taken count expressions refer to the given 349 /// subexpression. 350 bool hasOperand(const SCEV *S, ScalarEvolution *SE) const; 351 352 /// clear - Invalidate this result and free associated memory. 353 void clear(); 354 }; 355 356 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 357 /// this function as they are computed. 358 DenseMap<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 359 360 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 361 /// the PHI instructions that we attempt to compute constant evolutions for. 362 /// This allows us to avoid potentially expensive recomputation of these 363 /// properties. An instruction maps to null if we are unable to compute its 364 /// exit value. 365 DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 366 367 /// ValuesAtScopes - This map contains entries for all the expressions 368 /// that we attempt to compute getSCEVAtScope information for, which can 369 /// be expensive in extreme cases. 370 DenseMap<const SCEV *, 371 SmallVector<std::pair<const Loop *, const SCEV *>, 2> > ValuesAtScopes; 372 373 /// LoopDispositions - Memoized computeLoopDisposition results. 374 DenseMap<const SCEV *, 375 SmallVector<std::pair<const Loop *, LoopDisposition>, 2> > LoopDispositions; 376 377 /// computeLoopDisposition - Compute a LoopDisposition value. 378 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 379 380 /// BlockDispositions - Memoized computeBlockDisposition results. 381 DenseMap<const SCEV *, 382 SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> > BlockDispositions; 383 384 /// computeBlockDisposition - Compute a BlockDisposition value. 385 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB); 386 387 /// UnsignedRanges - Memoized results from getUnsignedRange 388 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 389 390 /// SignedRanges - Memoized results from getSignedRange 391 DenseMap<const SCEV *, ConstantRange> SignedRanges; 392 393 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 394 const ConstantRange &setUnsignedRange(const SCEV *S, 395 const ConstantRange &CR) { 396 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 397 UnsignedRanges.insert(std::make_pair(S, CR)); 398 if (!Pair.second) 399 Pair.first->second = CR; 400 return Pair.first->second; 401 } 402 403 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 404 const ConstantRange &setSignedRange(const SCEV *S, 405 const ConstantRange &CR) { 406 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 407 SignedRanges.insert(std::make_pair(S, CR)); 408 if (!Pair.second) 409 Pair.first->second = CR; 410 return Pair.first->second; 411 } 412 413 /// createSCEV - We know that there is no SCEV for the specified value. 414 /// Analyze the expression. 415 const SCEV *createSCEV(Value *V); 416 417 /// createNodeForPHI - Provide the special handling we need to analyze PHI 418 /// SCEVs. 419 const SCEV *createNodeForPHI(PHINode *PN); 420 421 /// createNodeForGEP - Provide the special handling we need to analyze GEP 422 /// SCEVs. 423 const SCEV *createNodeForGEP(GEPOperator *GEP); 424 425 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 426 /// at most once for each SCEV+Loop pair. 427 /// 428 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 429 430 /// ForgetSymbolicValue - This looks up computed SCEV values for all 431 /// instructions that depend on the given instruction and removes them from 432 /// the ValueExprMap map if they reference SymName. This is used during PHI 433 /// resolution. 434 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 435 436 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 437 /// loop, lazily computing new values if the loop hasn't been analyzed 438 /// yet. 439 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 440 441 /// ComputeBackedgeTakenCount - Compute the number of times the specified 442 /// loop will iterate. 443 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 444 445 /// ComputeExitLimit - Compute the number of times the backedge of the 446 /// specified loop will execute if it exits via the specified block. 447 ExitLimit ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock); 448 449 /// ComputeExitLimitFromCond - Compute the number of times the backedge of 450 /// the specified loop will execute if its exit condition were a conditional 451 /// branch of ExitCond, TBB, and FBB. 452 ExitLimit ComputeExitLimitFromCond(const Loop *L, 453 Value *ExitCond, 454 BasicBlock *TBB, 455 BasicBlock *FBB, 456 bool IsSubExpr); 457 458 /// ComputeExitLimitFromICmp - Compute the number of times the backedge of 459 /// the specified loop will execute if its exit condition were a conditional 460 /// branch of the ICmpInst ExitCond, TBB, and FBB. 461 ExitLimit ComputeExitLimitFromICmp(const Loop *L, 462 ICmpInst *ExitCond, 463 BasicBlock *TBB, 464 BasicBlock *FBB, 465 bool IsSubExpr); 466 467 /// ComputeExitLimitFromSingleExitSwitch - Compute the number of times the 468 /// backedge of the specified loop will execute if its exit condition were a 469 /// switch with a single exiting case to ExitingBB. 470 ExitLimit 471 ComputeExitLimitFromSingleExitSwitch(const Loop *L, SwitchInst *Switch, 472 BasicBlock *ExitingBB, bool IsSubExpr); 473 474 /// ComputeLoadConstantCompareExitLimit - Given an exit condition 475 /// of 'icmp op load X, cst', try to see if we can compute the 476 /// backedge-taken count. 477 ExitLimit ComputeLoadConstantCompareExitLimit(LoadInst *LI, 478 Constant *RHS, 479 const Loop *L, 480 ICmpInst::Predicate p); 481 482 /// ComputeExitCountExhaustively - If the loop is known to execute a 483 /// constant number of times (the condition evolves only from constants), 484 /// try to evaluate a few iterations of the loop until we get the exit 485 /// condition gets a value of ExitWhen (true or false). If we cannot 486 /// evaluate the exit count of the loop, return CouldNotCompute. 487 const SCEV *ComputeExitCountExhaustively(const Loop *L, 488 Value *Cond, 489 bool ExitWhen); 490 491 /// HowFarToZero - Return the number of times an exit condition comparing 492 /// the specified value to zero will execute. If not computable, return 493 /// CouldNotCompute. 494 ExitLimit HowFarToZero(const SCEV *V, const Loop *L, bool IsSubExpr); 495 496 /// HowFarToNonZero - Return the number of times an exit condition checking 497 /// the specified value for nonzero will execute. If not computable, return 498 /// CouldNotCompute. 499 ExitLimit HowFarToNonZero(const SCEV *V, const Loop *L); 500 501 /// HowManyLessThans - Return the number of times an exit condition 502 /// containing the specified less-than comparison will execute. If not 503 /// computable, return CouldNotCompute. isSigned specifies whether the 504 /// less-than is signed. 505 ExitLimit HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 506 const Loop *L, bool isSigned, bool IsSubExpr); 507 ExitLimit HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS, 508 const Loop *L, bool isSigned, bool IsSubExpr); 509 510 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 511 /// (which may not be an immediate predecessor) which has exactly one 512 /// successor from which BB is reachable, or null if no such block is 513 /// found. 514 std::pair<BasicBlock *, BasicBlock *> 515 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 516 517 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 518 /// RHS is true whenever the given FoundCondValue value evaluates to true. 519 bool isImpliedCond(ICmpInst::Predicate Pred, 520 const SCEV *LHS, const SCEV *RHS, 521 Value *FoundCondValue, 522 bool Inverse); 523 524 /// isImpliedCondOperands - Test whether the condition described by Pred, 525 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 526 /// and FoundRHS is true. 527 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 528 const SCEV *LHS, const SCEV *RHS, 529 const SCEV *FoundLHS, const SCEV *FoundRHS); 530 531 /// isImpliedCondOperandsHelper - Test whether the condition described by 532 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 533 /// FoundLHS, and FoundRHS is true. 534 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 535 const SCEV *LHS, const SCEV *RHS, 536 const SCEV *FoundLHS, 537 const SCEV *FoundRHS); 538 539 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 540 /// in the header of its containing loop, we know the loop executes a 541 /// constant number of times, and the PHI node is just a recurrence 542 /// involving constants, fold it. 543 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 544 const Loop *L); 545 546 /// isKnownPredicateWithRanges - Test if the given expression is known to 547 /// satisfy the condition described by Pred and the known constant ranges 548 /// of LHS and RHS. 549 /// 550 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 551 const SCEV *LHS, const SCEV *RHS); 552 553 /// forgetMemoizedResults - Drop memoized information computed for S. 554 void forgetMemoizedResults(const SCEV *S); 555 556 /// Return false iff given SCEV contains a SCEVUnknown with NULL value- 557 /// pointer. 558 bool checkValidity(const SCEV *S) const; 559 560 public: 561 static char ID; // Pass identification, replacement for typeid 562 ScalarEvolution(); 563 564 LLVMContext &getContext() const { return F->getContext(); } 565 566 /// isSCEVable - Test if values of the given type are analyzable within 567 /// the SCEV framework. This primarily includes integer types, and it 568 /// can optionally include pointer types if the ScalarEvolution class 569 /// has access to target-specific information. 570 bool isSCEVable(Type *Ty) const; 571 572 /// getTypeSizeInBits - Return the size in bits of the specified type, 573 /// for which isSCEVable must return true. 574 uint64_t getTypeSizeInBits(Type *Ty) const; 575 576 /// getEffectiveSCEVType - Return a type with the same bitwidth as 577 /// the given type and which represents how SCEV will treat the given 578 /// type, for which isSCEVable must return true. For pointer types, 579 /// this is the pointer-sized integer type. 580 Type *getEffectiveSCEVType(Type *Ty) const; 581 582 /// getSCEV - Return a SCEV expression for the full generality of the 583 /// specified expression. 584 const SCEV *getSCEV(Value *V); 585 586 const SCEV *getConstant(ConstantInt *V); 587 const SCEV *getConstant(const APInt& Val); 588 const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false); 589 const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty); 590 const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty); 591 const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty); 592 const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty); 593 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 594 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 595 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 596 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 597 SmallVector<const SCEV *, 2> Ops; 598 Ops.push_back(LHS); 599 Ops.push_back(RHS); 600 return getAddExpr(Ops, Flags); 601 } 602 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 603 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 604 SmallVector<const SCEV *, 3> Ops; 605 Ops.push_back(Op0); 606 Ops.push_back(Op1); 607 Ops.push_back(Op2); 608 return getAddExpr(Ops, Flags); 609 } 610 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 611 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 612 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 613 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) 614 { 615 SmallVector<const SCEV *, 2> Ops; 616 Ops.push_back(LHS); 617 Ops.push_back(RHS); 618 return getMulExpr(Ops, Flags); 619 } 620 const SCEV *getMulExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2, 621 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) { 622 SmallVector<const SCEV *, 3> Ops; 623 Ops.push_back(Op0); 624 Ops.push_back(Op1); 625 Ops.push_back(Op2); 626 return getMulExpr(Ops, Flags); 627 } 628 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 629 const SCEV *getUDivExactExpr(const SCEV *LHS, const SCEV *RHS); 630 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 631 const Loop *L, SCEV::NoWrapFlags Flags); 632 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 633 const Loop *L, SCEV::NoWrapFlags Flags); 634 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 635 const Loop *L, SCEV::NoWrapFlags Flags) { 636 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 637 return getAddRecExpr(NewOp, L, Flags); 638 } 639 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 640 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 641 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 642 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 643 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 644 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 645 const SCEV *getUnknown(Value *V); 646 const SCEV *getCouldNotCompute(); 647 648 /// getSizeOfExpr - Return an expression for sizeof AllocTy that is type 649 /// IntTy 650 /// 651 const SCEV *getSizeOfExpr(Type *IntTy, Type *AllocTy); 652 653 /// getOffsetOfExpr - Return an expression for offsetof on the given field 654 /// with type IntTy 655 /// 656 const SCEV *getOffsetOfExpr(Type *IntTy, StructType *STy, unsigned FieldNo); 657 658 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 659 /// 660 const SCEV *getNegativeSCEV(const SCEV *V); 661 662 /// getNotSCEV - Return the SCEV object corresponding to ~V. 663 /// 664 const SCEV *getNotSCEV(const SCEV *V); 665 666 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1. 667 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS, 668 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap); 669 670 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 671 /// of the input value to the specified type. If the type must be 672 /// extended, it is zero extended. 673 const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty); 674 675 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 676 /// of the input value to the specified type. If the type must be 677 /// extended, it is sign extended. 678 const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty); 679 680 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 681 /// the input value to the specified type. If the type must be extended, 682 /// it is zero extended. The conversion must not be narrowing. 683 const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty); 684 685 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 686 /// the input value to the specified type. If the type must be extended, 687 /// it is sign extended. The conversion must not be narrowing. 688 const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty); 689 690 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 691 /// the input value to the specified type. If the type must be extended, 692 /// it is extended with unspecified bits. The conversion must not be 693 /// narrowing. 694 const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty); 695 696 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 697 /// input value to the specified type. The conversion must not be 698 /// widening. 699 const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty); 700 701 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 702 /// the types using zero-extension, and then perform a umax operation 703 /// with them. 704 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 705 const SCEV *RHS); 706 707 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 708 /// the types using zero-extension, and then perform a umin operation 709 /// with them. 710 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 711 const SCEV *RHS); 712 713 /// getPointerBase - Transitively follow the chain of pointer-type operands 714 /// until reaching a SCEV that does not have a single pointer operand. This 715 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions, 716 /// but corner cases do exist. 717 const SCEV *getPointerBase(const SCEV *V); 718 719 /// getSCEVAtScope - Return a SCEV expression for the specified value 720 /// at the specified scope in the program. The L value specifies a loop 721 /// nest to evaluate the expression at, where null is the top-level or a 722 /// specified loop is immediately inside of the loop. 723 /// 724 /// This method can be used to compute the exit value for a variable defined 725 /// in a loop by querying what the value will hold in the parent loop. 726 /// 727 /// In the case that a relevant loop exit value cannot be computed, the 728 /// original value V is returned. 729 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 730 731 /// getSCEVAtScope - This is a convenience function which does 732 /// getSCEVAtScope(getSCEV(V), L). 733 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 734 735 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 736 /// by a conditional between LHS and RHS. This is used to help avoid max 737 /// expressions in loop trip counts, and to eliminate casts. 738 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 739 const SCEV *LHS, const SCEV *RHS); 740 741 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 742 /// protected by a conditional between LHS and RHS. This is used to 743 /// to eliminate casts. 744 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 745 const SCEV *LHS, const SCEV *RHS); 746 747 /// \brief Returns the maximum trip count of the loop if it is a single-exit 748 /// loop and we can compute a small maximum for that loop. 749 /// 750 /// Implemented in terms of the \c getSmallConstantTripCount overload with 751 /// the single exiting block passed to it. See that routine for details. 752 unsigned getSmallConstantTripCount(Loop *L); 753 754 /// getSmallConstantTripCount - Returns the maximum trip count of this loop 755 /// as a normal unsigned value. Returns 0 if the trip count is unknown or 756 /// not constant. This "trip count" assumes that control exits via 757 /// ExitingBlock. More precisely, it is the number of times that control may 758 /// reach ExitingBlock before taking the branch. For loops with multiple 759 /// exits, it may not be the number times that the loop header executes if 760 /// the loop exits prematurely via another branch. 761 unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitingBlock); 762 763 /// \brief Returns the largest constant divisor of the trip count of the 764 /// loop if it is a single-exit loop and we can compute a small maximum for 765 /// that loop. 766 /// 767 /// Implemented in terms of the \c getSmallConstantTripMultiple overload with 768 /// the single exiting block passed to it. See that routine for details. 769 unsigned getSmallConstantTripMultiple(Loop *L); 770 771 /// getSmallConstantTripMultiple - Returns the largest constant divisor of 772 /// the trip count of this loop as a normal unsigned value, if 773 /// possible. This means that the actual trip count is always a multiple of 774 /// the returned value (don't forget the trip count could very well be zero 775 /// as well!). As explained in the comments for getSmallConstantTripCount, 776 /// this assumes that control exits the loop via ExitingBlock. 777 unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitingBlock); 778 779 // getExitCount - Get the expression for the number of loop iterations for 780 // which this loop is guaranteed not to exit via ExitingBlock. Otherwise 781 // return SCEVCouldNotCompute. 782 const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock); 783 784 /// getBackedgeTakenCount - If the specified loop has a predictable 785 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 786 /// object. The backedge-taken count is the number of times the loop header 787 /// will be branched to from within the loop. This is one less than the 788 /// trip count of the loop, since it doesn't count the first iteration, 789 /// when the header is branched to from outside the loop. 790 /// 791 /// Note that it is not valid to call this method on a loop without a 792 /// loop-invariant backedge-taken count (see 793 /// hasLoopInvariantBackedgeTakenCount). 794 /// 795 const SCEV *getBackedgeTakenCount(const Loop *L); 796 797 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 798 /// return the least SCEV value that is known never to be less than the 799 /// actual backedge taken count. 800 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 801 802 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 803 /// has an analyzable loop-invariant backedge-taken count. 804 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 805 806 /// forgetLoop - This method should be called by the client when it has 807 /// changed a loop in a way that may effect ScalarEvolution's ability to 808 /// compute a trip count, or if the loop is deleted. This call is 809 /// potentially expensive for large loop bodies. 810 void forgetLoop(const Loop *L); 811 812 /// forgetValue - This method should be called by the client when it has 813 /// changed a value in a way that may effect its value, or which may 814 /// disconnect it from a def-use chain linking it to a loop. 815 void forgetValue(Value *V); 816 817 /// \brief Called when the client has changed the disposition of values in 818 /// this loop. 819 /// 820 /// We don't have a way to invalidate per-loop dispositions. Clear and 821 /// recompute is simpler. 822 void forgetLoopDispositions(const Loop *L) { LoopDispositions.clear(); } 823 824 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 825 /// is guaranteed to end in (at every loop iteration). It is, at the same 826 /// time, the minimum number of times S is divisible by 2. For example, 827 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 828 /// bitwidth of S. 829 uint32_t GetMinTrailingZeros(const SCEV *S); 830 831 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 832 /// 833 ConstantRange getUnsignedRange(const SCEV *S); 834 835 /// getSignedRange - Determine the signed range for a particular SCEV. 836 /// 837 ConstantRange getSignedRange(const SCEV *S); 838 839 /// isKnownNegative - Test if the given expression is known to be negative. 840 /// 841 bool isKnownNegative(const SCEV *S); 842 843 /// isKnownPositive - Test if the given expression is known to be positive. 844 /// 845 bool isKnownPositive(const SCEV *S); 846 847 /// isKnownNonNegative - Test if the given expression is known to be 848 /// non-negative. 849 /// 850 bool isKnownNonNegative(const SCEV *S); 851 852 /// isKnownNonPositive - Test if the given expression is known to be 853 /// non-positive. 854 /// 855 bool isKnownNonPositive(const SCEV *S); 856 857 /// isKnownNonZero - Test if the given expression is known to be 858 /// non-zero. 859 /// 860 bool isKnownNonZero(const SCEV *S); 861 862 /// isKnownPredicate - Test if the given expression is known to satisfy 863 /// the condition described by Pred, LHS, and RHS. 864 /// 865 bool isKnownPredicate(ICmpInst::Predicate Pred, 866 const SCEV *LHS, const SCEV *RHS); 867 868 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 869 /// predicate Pred. Return true iff any changes were made. If the 870 /// operands are provably equal or unequal, LHS and RHS are set to 871 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 872 /// 873 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 874 const SCEV *&LHS, 875 const SCEV *&RHS, 876 unsigned Depth = 0); 877 878 /// getLoopDisposition - Return the "disposition" of the given SCEV with 879 /// respect to the given loop. 880 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 881 882 /// isLoopInvariant - Return true if the value of the given SCEV is 883 /// unchanging in the specified loop. 884 bool isLoopInvariant(const SCEV *S, const Loop *L); 885 886 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 887 /// in a known way in the specified loop. This property being true implies 888 /// that the value is variant in the loop AND that we can emit an expression 889 /// to compute the value of the expression at any particular loop iteration. 890 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 891 892 /// getLoopDisposition - Return the "disposition" of the given SCEV with 893 /// respect to the given block. 894 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB); 895 896 /// dominates - Return true if elements that makes up the given SCEV 897 /// dominate the specified basic block. 898 bool dominates(const SCEV *S, const BasicBlock *BB); 899 900 /// properlyDominates - Return true if elements that makes up the given SCEV 901 /// properly dominate the specified basic block. 902 bool properlyDominates(const SCEV *S, const BasicBlock *BB); 903 904 /// hasOperand - Test whether the given SCEV has Op as a direct or 905 /// indirect operand. 906 bool hasOperand(const SCEV *S, const SCEV *Op) const; 907 908 /// Return the size of an element read or written by Inst. 909 const SCEV *getElementSize(Instruction *Inst); 910 911 /// Compute the array dimensions Sizes from the set of Terms extracted from 912 /// the memory access function of this SCEVAddRecExpr. 913 void findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms, 914 SmallVectorImpl<const SCEV *> &Sizes, 915 const SCEV *ElementSize) const; 916 917 bool runOnFunction(Function &F) override; 918 void releaseMemory() override; 919 void getAnalysisUsage(AnalysisUsage &AU) const override; 920 void print(raw_ostream &OS, const Module* = nullptr) const override; 921 void verifyAnalysis() const override; 922 923 private: 924 /// Compute the backedge taken count knowing the interval difference, the 925 /// stride and presence of the equality in the comparison. 926 const SCEV *computeBECount(const SCEV *Delta, const SCEV *Stride, 927 bool Equality); 928 929 /// Verify if an linear IV with positive stride can overflow when in a 930 /// less-than comparison, knowing the invariant term of the comparison, 931 /// the stride and the knowledge of NSW/NUW flags on the recurrence. 932 bool doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride, 933 bool IsSigned, bool NoWrap); 934 935 /// Verify if an linear IV with negative stride can overflow when in a 936 /// greater-than comparison, knowing the invariant term of the comparison, 937 /// the stride and the knowledge of NSW/NUW flags on the recurrence. 938 bool doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride, 939 bool IsSigned, bool NoWrap); 940 941 private: 942 FoldingSet<SCEV> UniqueSCEVs; 943 BumpPtrAllocator SCEVAllocator; 944 945 /// FirstUnknown - The head of a linked list of all SCEVUnknown 946 /// values that have been allocated. This is used by releaseMemory 947 /// to locate them all and call their destructors. 948 SCEVUnknown *FirstUnknown; 949 }; 950 } 951 952 #endif 953