ScalarEvolution.h revision 714b5290b04e08570dae4304c1c92d30c06d3c99
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/System/DataTypes.h" 28#include "llvm/Support/ValueHandle.h" 29#include "llvm/Support/Allocator.h" 30#include "llvm/Support/ConstantRange.h" 31#include "llvm/ADT/FoldingSet.h" 32#include "llvm/ADT/DenseMap.h" 33#include <map> 34 35namespace llvm { 36 class APInt; 37 class Constant; 38 class ConstantInt; 39 class DominatorTree; 40 class Type; 41 class ScalarEvolution; 42 class TargetData; 43 class LLVMContext; 44 class Loop; 45 class LoopInfo; 46 class Operator; 47 class SCEVUnknown; 48 class SCEV; 49 template<> struct FoldingSetTrait<SCEV>; 50 51 /// SCEV - This class represents an analyzed expression in the program. These 52 /// are opaque objects that the client is not allowed to do much with 53 /// directly. 54 /// 55 class SCEV : public FoldingSetNode { 56 friend struct FoldingSetTrait<SCEV>; 57 58 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 59 /// The ScalarEvolution's BumpPtrAllocator holds the data. 60 FoldingSetNodeIDRef FastID; 61 62 // The SCEV baseclass this node corresponds to 63 const unsigned short SCEVType; 64 65 protected: 66 /// SubclassData - This field is initialized to zero and may be used in 67 /// subclasses to store miscellaneous information. 68 unsigned short SubclassData; 69 70 private: 71 SCEV(const SCEV &); // DO NOT IMPLEMENT 72 void operator=(const SCEV &); // DO NOT IMPLEMENT 73 74 public: 75 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 76 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 77 78 unsigned getSCEVType() const { return SCEVType; } 79 80 /// getType - Return the LLVM type of this SCEV expression. 81 /// 82 const Type *getType() const; 83 84 /// isZero - Return true if the expression is a constant zero. 85 /// 86 bool isZero() const; 87 88 /// isOne - Return true if the expression is a constant one. 89 /// 90 bool isOne() const; 91 92 /// isAllOnesValue - Return true if the expression is a constant 93 /// all-ones value. 94 /// 95 bool isAllOnesValue() const; 96 97 /// print - Print out the internal representation of this scalar to the 98 /// specified stream. This should really only be used for debugging 99 /// purposes. 100 void print(raw_ostream &OS) const; 101 102 /// dump - This method is used for debugging. 103 /// 104 void dump() const; 105 }; 106 107 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 108 // temporary FoldingSetNodeID values. 109 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 110 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 111 ID = X.FastID; 112 } 113 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 114 FoldingSetNodeID &TempID) { 115 return ID == X.FastID; 116 } 117 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 118 return X.FastID.ComputeHash(); 119 } 120 }; 121 122 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 123 S.print(OS); 124 return OS; 125 } 126 127 /// SCEVCouldNotCompute - An object of this class is returned by queries that 128 /// could not be answered. For example, if you ask for the number of 129 /// iterations of a linked-list traversal loop, you will get one of these. 130 /// None of the standard SCEV operations are valid on this class, it is just a 131 /// marker. 132 struct SCEVCouldNotCompute : public SCEV { 133 SCEVCouldNotCompute(); 134 135 /// Methods for support type inquiry through isa, cast, and dyn_cast: 136 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 137 static bool classof(const SCEV *S); 138 }; 139 140 /// ScalarEvolution - This class is the main scalar evolution driver. Because 141 /// client code (intentionally) can't do much with the SCEV objects directly, 142 /// they must ask this class for services. 143 /// 144 class ScalarEvolution : public FunctionPass { 145 public: 146 /// LoopDisposition - An enum describing the relationship between a 147 /// SCEV and a loop. 148 enum LoopDisposition { 149 LoopVariant, ///< The SCEV is loop-variant (unknown). 150 LoopInvariant, ///< The SCEV is loop-invariant. 151 LoopComputable ///< The SCEV varies predictably with the loop. 152 }; 153 154 private: 155 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 156 /// notified whenever a Value is deleted. 157 class SCEVCallbackVH : public CallbackVH { 158 ScalarEvolution *SE; 159 virtual void deleted(); 160 virtual void allUsesReplacedWith(Value *New); 161 public: 162 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 163 }; 164 165 friend class SCEVCallbackVH; 166 friend class SCEVExpander; 167 friend class SCEVUnknown; 168 169 /// F - The function we are analyzing. 170 /// 171 Function *F; 172 173 /// LI - The loop information for the function we are currently analyzing. 174 /// 175 LoopInfo *LI; 176 177 /// TD - The target data information for the target we are targeting. 178 /// 179 TargetData *TD; 180 181 /// DT - The dominator tree. 182 /// 183 DominatorTree *DT; 184 185 /// CouldNotCompute - This SCEV is used to represent unknown trip 186 /// counts and things. 187 SCEVCouldNotCompute CouldNotCompute; 188 189 /// ValueExprMapType - The typedef for ValueExprMap. 190 /// 191 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 192 ValueExprMapType; 193 194 /// ValueExprMap - This is a cache of the values we have analyzed so far. 195 /// 196 ValueExprMapType ValueExprMap; 197 198 /// BackedgeTakenInfo - Information about the backedge-taken count 199 /// of a loop. This currently includes an exact count and a maximum count. 200 /// 201 struct BackedgeTakenInfo { 202 /// Exact - An expression indicating the exact backedge-taken count of 203 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 204 const SCEV *Exact; 205 206 /// Max - An expression indicating the least maximum backedge-taken 207 /// count of the loop that is known, or a SCEVCouldNotCompute. 208 const SCEV *Max; 209 210 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 211 Exact(exact), Max(exact) {} 212 213 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 214 Exact(exact), Max(max) {} 215 216 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 217 /// computed information, or whether it's all SCEVCouldNotCompute 218 /// values. 219 bool hasAnyInfo() const { 220 return !isa<SCEVCouldNotCompute>(Exact) || 221 !isa<SCEVCouldNotCompute>(Max); 222 } 223 }; 224 225 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 226 /// this function as they are computed. 227 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 228 229 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 230 /// the PHI instructions that we attempt to compute constant evolutions for. 231 /// This allows us to avoid potentially expensive recomputation of these 232 /// properties. An instruction maps to null if we are unable to compute its 233 /// exit value. 234 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 235 236 /// ValuesAtScopes - This map contains entries for all the expressions 237 /// that we attempt to compute getSCEVAtScope information for, which can 238 /// be expensive in extreme cases. 239 std::map<const SCEV *, 240 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 241 242 /// LoopDispositions - Memoized computeLoopDisposition results. 243 std::map<const SCEV *, 244 std::map<const Loop *, LoopDisposition> > LoopDispositions; 245 246 /// computeLoopDisposition - Compute a LoopDisposition value. 247 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L); 248 249 /// UnsignedRanges - Memoized results from getUnsignedRange 250 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 251 252 /// SignedRanges - Memoized results from getSignedRange 253 DenseMap<const SCEV *, ConstantRange> SignedRanges; 254 255 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 256 const ConstantRange &setUnsignedRange(const SCEV *S, 257 const ConstantRange &CR) { 258 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 259 UnsignedRanges.insert(std::make_pair(S, CR)); 260 if (!Pair.second) 261 Pair.first->second = CR; 262 return Pair.first->second; 263 } 264 265 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 266 const ConstantRange &setSignedRange(const SCEV *S, 267 const ConstantRange &CR) { 268 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 269 SignedRanges.insert(std::make_pair(S, CR)); 270 if (!Pair.second) 271 Pair.first->second = CR; 272 return Pair.first->second; 273 } 274 275 /// createSCEV - We know that there is no SCEV for the specified value. 276 /// Analyze the expression. 277 const SCEV *createSCEV(Value *V); 278 279 /// createNodeForPHI - Provide the special handling we need to analyze PHI 280 /// SCEVs. 281 const SCEV *createNodeForPHI(PHINode *PN); 282 283 /// createNodeForGEP - Provide the special handling we need to analyze GEP 284 /// SCEVs. 285 const SCEV *createNodeForGEP(GEPOperator *GEP); 286 287 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 288 /// at most once for each SCEV+Loop pair. 289 /// 290 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 291 292 /// ForgetSymbolicValue - This looks up computed SCEV values for all 293 /// instructions that depend on the given instruction and removes them from 294 /// the ValueExprMap map if they reference SymName. This is used during PHI 295 /// resolution. 296 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 297 298 /// getBECount - Subtract the end and start values and divide by the step, 299 /// rounding up, to get the number of times the backedge is executed. Return 300 /// CouldNotCompute if an intermediate computation overflows. 301 const SCEV *getBECount(const SCEV *Start, 302 const SCEV *End, 303 const SCEV *Step, 304 bool NoWrap); 305 306 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 307 /// loop, lazily computing new values if the loop hasn't been analyzed 308 /// yet. 309 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 310 311 /// ComputeBackedgeTakenCount - Compute the number of times the specified 312 /// loop will iterate. 313 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 314 315 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 316 /// backedge of the specified loop will execute if it exits via the 317 /// specified block. 318 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 319 BasicBlock *ExitingBlock); 320 321 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 322 /// backedge of the specified loop will execute if its exit condition 323 /// were a conditional branch of ExitCond, TBB, and FBB. 324 BackedgeTakenInfo 325 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 326 Value *ExitCond, 327 BasicBlock *TBB, 328 BasicBlock *FBB); 329 330 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 331 /// times the backedge of the specified loop will execute if its exit 332 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 333 /// and FBB. 334 BackedgeTakenInfo 335 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 336 ICmpInst *ExitCond, 337 BasicBlock *TBB, 338 BasicBlock *FBB); 339 340 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 341 /// of 'icmp op load X, cst', try to see if we can compute the 342 /// backedge-taken count. 343 BackedgeTakenInfo 344 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 345 Constant *RHS, 346 const Loop *L, 347 ICmpInst::Predicate p); 348 349 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 350 /// a constant number of times (the condition evolves only from constants), 351 /// try to evaluate a few iterations of the loop until we get the exit 352 /// condition gets a value of ExitWhen (true or false). If we cannot 353 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 354 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 355 Value *Cond, 356 bool ExitWhen); 357 358 /// HowFarToZero - Return the number of times a backedge comparing the 359 /// specified value to zero will execute. If not computable, return 360 /// CouldNotCompute. 361 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 362 363 /// HowFarToNonZero - Return the number of times a backedge checking the 364 /// specified value for nonzero will execute. If not computable, return 365 /// CouldNotCompute. 366 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 367 368 /// HowManyLessThans - Return the number of times a backedge containing the 369 /// specified less-than comparison will execute. If not computable, return 370 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 371 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 372 const Loop *L, bool isSigned); 373 374 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 375 /// (which may not be an immediate predecessor) which has exactly one 376 /// successor from which BB is reachable, or null if no such block is 377 /// found. 378 std::pair<BasicBlock *, BasicBlock *> 379 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 380 381 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 382 /// RHS is true whenever the given FoundCondValue value evaluates to true. 383 bool isImpliedCond(ICmpInst::Predicate Pred, 384 const SCEV *LHS, const SCEV *RHS, 385 Value *FoundCondValue, 386 bool Inverse); 387 388 /// isImpliedCondOperands - Test whether the condition described by Pred, 389 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 390 /// and FoundRHS is true. 391 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 392 const SCEV *LHS, const SCEV *RHS, 393 const SCEV *FoundLHS, const SCEV *FoundRHS); 394 395 /// isImpliedCondOperandsHelper - Test whether the condition described by 396 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 397 /// FoundLHS, and FoundRHS is true. 398 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 399 const SCEV *LHS, const SCEV *RHS, 400 const SCEV *FoundLHS, const SCEV *FoundRHS); 401 402 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 403 /// in the header of its containing loop, we know the loop executes a 404 /// constant number of times, and the PHI node is just a recurrence 405 /// involving constants, fold it. 406 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 407 const Loop *L); 408 409 /// isKnownPredicateWithRanges - Test if the given expression is known to 410 /// satisfy the condition described by Pred and the known constant ranges 411 /// of LHS and RHS. 412 /// 413 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 414 const SCEV *LHS, const SCEV *RHS); 415 416 public: 417 static char ID; // Pass identification, replacement for typeid 418 ScalarEvolution(); 419 420 LLVMContext &getContext() const { return F->getContext(); } 421 422 /// isSCEVable - Test if values of the given type are analyzable within 423 /// the SCEV framework. This primarily includes integer types, and it 424 /// can optionally include pointer types if the ScalarEvolution class 425 /// has access to target-specific information. 426 bool isSCEVable(const Type *Ty) const; 427 428 /// getTypeSizeInBits - Return the size in bits of the specified type, 429 /// for which isSCEVable must return true. 430 uint64_t getTypeSizeInBits(const Type *Ty) const; 431 432 /// getEffectiveSCEVType - Return a type with the same bitwidth as 433 /// the given type and which represents how SCEV will treat the given 434 /// type, for which isSCEVable must return true. For pointer types, 435 /// this is the pointer-sized integer type. 436 const Type *getEffectiveSCEVType(const Type *Ty) const; 437 438 /// getSCEV - Return a SCEV expression for the full generality of the 439 /// specified expression. 440 const SCEV *getSCEV(Value *V); 441 442 const SCEV *getConstant(ConstantInt *V); 443 const SCEV *getConstant(const APInt& Val); 444 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 445 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 446 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 447 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 448 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 449 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 450 bool HasNUW = false, bool HasNSW = false); 451 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 452 bool HasNUW = false, bool HasNSW = false) { 453 SmallVector<const SCEV *, 2> Ops; 454 Ops.push_back(LHS); 455 Ops.push_back(RHS); 456 return getAddExpr(Ops, HasNUW, HasNSW); 457 } 458 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 459 const SCEV *Op2, 460 bool HasNUW = false, bool HasNSW = false) { 461 SmallVector<const SCEV *, 3> Ops; 462 Ops.push_back(Op0); 463 Ops.push_back(Op1); 464 Ops.push_back(Op2); 465 return getAddExpr(Ops, HasNUW, HasNSW); 466 } 467 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 468 bool HasNUW = false, bool HasNSW = false); 469 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 470 bool HasNUW = false, bool HasNSW = false) { 471 SmallVector<const SCEV *, 2> Ops; 472 Ops.push_back(LHS); 473 Ops.push_back(RHS); 474 return getMulExpr(Ops, HasNUW, HasNSW); 475 } 476 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 477 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 478 const Loop *L, 479 bool HasNUW = false, bool HasNSW = false); 480 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 481 const Loop *L, 482 bool HasNUW = false, bool HasNSW = false); 483 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 484 const Loop *L, 485 bool HasNUW = false, bool HasNSW = false) { 486 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 487 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 488 } 489 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 490 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 491 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 492 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 493 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 494 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 495 const SCEV *getUnknown(Value *V); 496 const SCEV *getCouldNotCompute(); 497 498 /// getSizeOfExpr - Return an expression for sizeof on the given type. 499 /// 500 const SCEV *getSizeOfExpr(const Type *AllocTy); 501 502 /// getAlignOfExpr - Return an expression for alignof on the given type. 503 /// 504 const SCEV *getAlignOfExpr(const Type *AllocTy); 505 506 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 507 /// 508 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 509 510 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 511 /// 512 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 513 514 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 515 /// 516 const SCEV *getNegativeSCEV(const SCEV *V); 517 518 /// getNotSCEV - Return the SCEV object corresponding to ~V. 519 /// 520 const SCEV *getNotSCEV(const SCEV *V); 521 522 /// getMinusSCEV - Return LHS-RHS. 523 /// 524 const SCEV *getMinusSCEV(const SCEV *LHS, 525 const SCEV *RHS); 526 527 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 528 /// of the input value to the specified type. If the type must be 529 /// extended, it is zero extended. 530 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 531 532 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 533 /// of the input value to the specified type. If the type must be 534 /// extended, it is sign extended. 535 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 536 537 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 538 /// the input value to the specified type. If the type must be extended, 539 /// it is zero extended. The conversion must not be narrowing. 540 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 541 542 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 543 /// the input value to the specified type. If the type must be extended, 544 /// it is sign extended. The conversion must not be narrowing. 545 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 546 547 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 548 /// the input value to the specified type. If the type must be extended, 549 /// it is extended with unspecified bits. The conversion must not be 550 /// narrowing. 551 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 552 553 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 554 /// input value to the specified type. The conversion must not be 555 /// widening. 556 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 557 558 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 559 /// the types using zero-extension, and then perform a umax operation 560 /// with them. 561 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 562 const SCEV *RHS); 563 564 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 565 /// the types using zero-extension, and then perform a umin operation 566 /// with them. 567 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 568 const SCEV *RHS); 569 570 /// getSCEVAtScope - Return a SCEV expression for the specified value 571 /// at the specified scope in the program. The L value specifies a loop 572 /// nest to evaluate the expression at, where null is the top-level or a 573 /// specified loop is immediately inside of the loop. 574 /// 575 /// This method can be used to compute the exit value for a variable defined 576 /// in a loop by querying what the value will hold in the parent loop. 577 /// 578 /// In the case that a relevant loop exit value cannot be computed, the 579 /// original value V is returned. 580 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 581 582 /// getSCEVAtScope - This is a convenience function which does 583 /// getSCEVAtScope(getSCEV(V), L). 584 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 585 586 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 587 /// by a conditional between LHS and RHS. This is used to help avoid max 588 /// expressions in loop trip counts, and to eliminate casts. 589 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 590 const SCEV *LHS, const SCEV *RHS); 591 592 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 593 /// protected by a conditional between LHS and RHS. This is used to 594 /// to eliminate casts. 595 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 596 const SCEV *LHS, const SCEV *RHS); 597 598 /// getBackedgeTakenCount - If the specified loop has a predictable 599 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 600 /// object. The backedge-taken count is the number of times the loop header 601 /// will be branched to from within the loop. This is one less than the 602 /// trip count of the loop, since it doesn't count the first iteration, 603 /// when the header is branched to from outside the loop. 604 /// 605 /// Note that it is not valid to call this method on a loop without a 606 /// loop-invariant backedge-taken count (see 607 /// hasLoopInvariantBackedgeTakenCount). 608 /// 609 const SCEV *getBackedgeTakenCount(const Loop *L); 610 611 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 612 /// return the least SCEV value that is known never to be less than the 613 /// actual backedge taken count. 614 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 615 616 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 617 /// has an analyzable loop-invariant backedge-taken count. 618 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 619 620 /// forgetLoop - This method should be called by the client when it has 621 /// changed a loop in a way that may effect ScalarEvolution's ability to 622 /// compute a trip count, or if the loop is deleted. 623 void forgetLoop(const Loop *L); 624 625 /// forgetValue - This method should be called by the client when it has 626 /// changed a value in a way that may effect its value, or which may 627 /// disconnect it from a def-use chain linking it to a loop. 628 void forgetValue(Value *V); 629 630 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 631 /// is guaranteed to end in (at every loop iteration). It is, at the same 632 /// time, the minimum number of times S is divisible by 2. For example, 633 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 634 /// bitwidth of S. 635 uint32_t GetMinTrailingZeros(const SCEV *S); 636 637 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 638 /// 639 ConstantRange getUnsignedRange(const SCEV *S); 640 641 /// getSignedRange - Determine the signed range for a particular SCEV. 642 /// 643 ConstantRange getSignedRange(const SCEV *S); 644 645 /// isKnownNegative - Test if the given expression is known to be negative. 646 /// 647 bool isKnownNegative(const SCEV *S); 648 649 /// isKnownPositive - Test if the given expression is known to be positive. 650 /// 651 bool isKnownPositive(const SCEV *S); 652 653 /// isKnownNonNegative - Test if the given expression is known to be 654 /// non-negative. 655 /// 656 bool isKnownNonNegative(const SCEV *S); 657 658 /// isKnownNonPositive - Test if the given expression is known to be 659 /// non-positive. 660 /// 661 bool isKnownNonPositive(const SCEV *S); 662 663 /// isKnownNonZero - Test if the given expression is known to be 664 /// non-zero. 665 /// 666 bool isKnownNonZero(const SCEV *S); 667 668 /// isKnownPredicate - Test if the given expression is known to satisfy 669 /// the condition described by Pred, LHS, and RHS. 670 /// 671 bool isKnownPredicate(ICmpInst::Predicate Pred, 672 const SCEV *LHS, const SCEV *RHS); 673 674 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 675 /// predicate Pred. Return true iff any changes were made. If the 676 /// operands are provably equal or inequal, LHS and RHS are set to 677 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 678 /// 679 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 680 const SCEV *&LHS, 681 const SCEV *&RHS); 682 683 /// getLoopDisposition - Return the "disposition" of the given SCEV with 684 /// respect to the given loop. 685 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 686 687 /// isLoopInvariant - Return true if the value of the given SCEV is 688 /// unchanging in the specified loop. 689 bool isLoopInvariant(const SCEV *S, const Loop *L); 690 691 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 692 /// in a known way in the specified loop. This property being true implies 693 /// that the value is variant in the loop AND that we can emit an expression 694 /// to compute the value of the expression at any particular loop iteration. 695 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 696 697 /// dominates - Return true if elements that makes up the given SCEV 698 /// dominate the specified basic block. 699 bool dominates(const SCEV *S, BasicBlock *BB) const; 700 701 /// properlyDominates - Return true if elements that makes up the given SCEV 702 /// properly dominate the specified basic block. 703 bool properlyDominates(const SCEV *S, BasicBlock *BB) const; 704 705 /// hasOperand - Test whether the given SCEV has Op as a direct or 706 /// indirect operand. 707 bool hasOperand(const SCEV *S, const SCEV *Op) const; 708 709 virtual bool runOnFunction(Function &F); 710 virtual void releaseMemory(); 711 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 712 virtual void print(raw_ostream &OS, const Module* = 0) const; 713 714 private: 715 FoldingSet<SCEV> UniqueSCEVs; 716 BumpPtrAllocator SCEVAllocator; 717 718 /// FirstUnknown - The head of a linked list of all SCEVUnknown 719 /// values that have been allocated. This is used by releaseMemory 720 /// to locate them all and call their destructors. 721 SCEVUnknown *FirstUnknown; 722 }; 723} 724 725#endif 726