ScalarEvolution.h revision 56a756821842678a96f2baa8c6a53bd28fc2b69e
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 /// forgetMemoizedResults - Drop memoized information computed for S. 417 void forgetMemoizedResults(const SCEV *S); 418 419 public: 420 static char ID; // Pass identification, replacement for typeid 421 ScalarEvolution(); 422 423 LLVMContext &getContext() const { return F->getContext(); } 424 425 /// isSCEVable - Test if values of the given type are analyzable within 426 /// the SCEV framework. This primarily includes integer types, and it 427 /// can optionally include pointer types if the ScalarEvolution class 428 /// has access to target-specific information. 429 bool isSCEVable(const Type *Ty) const; 430 431 /// getTypeSizeInBits - Return the size in bits of the specified type, 432 /// for which isSCEVable must return true. 433 uint64_t getTypeSizeInBits(const Type *Ty) const; 434 435 /// getEffectiveSCEVType - Return a type with the same bitwidth as 436 /// the given type and which represents how SCEV will treat the given 437 /// type, for which isSCEVable must return true. For pointer types, 438 /// this is the pointer-sized integer type. 439 const Type *getEffectiveSCEVType(const Type *Ty) const; 440 441 /// getSCEV - Return a SCEV expression for the full generality of the 442 /// specified expression. 443 const SCEV *getSCEV(Value *V); 444 445 const SCEV *getConstant(ConstantInt *V); 446 const SCEV *getConstant(const APInt& Val); 447 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 448 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 449 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 450 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 451 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 452 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 453 bool HasNUW = false, bool HasNSW = false); 454 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 455 bool HasNUW = false, bool HasNSW = false) { 456 SmallVector<const SCEV *, 2> Ops; 457 Ops.push_back(LHS); 458 Ops.push_back(RHS); 459 return getAddExpr(Ops, HasNUW, HasNSW); 460 } 461 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 462 const SCEV *Op2, 463 bool HasNUW = false, bool HasNSW = false) { 464 SmallVector<const SCEV *, 3> Ops; 465 Ops.push_back(Op0); 466 Ops.push_back(Op1); 467 Ops.push_back(Op2); 468 return getAddExpr(Ops, HasNUW, HasNSW); 469 } 470 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 471 bool HasNUW = false, bool HasNSW = false); 472 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 473 bool HasNUW = false, bool HasNSW = false) { 474 SmallVector<const SCEV *, 2> Ops; 475 Ops.push_back(LHS); 476 Ops.push_back(RHS); 477 return getMulExpr(Ops, HasNUW, HasNSW); 478 } 479 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 480 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 481 const Loop *L, 482 bool HasNUW = false, bool HasNSW = false); 483 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 484 const Loop *L, 485 bool HasNUW = false, bool HasNSW = false); 486 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 487 const Loop *L, 488 bool HasNUW = false, bool HasNSW = false) { 489 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 490 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 491 } 492 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 493 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 494 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 495 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 496 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 497 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 498 const SCEV *getUnknown(Value *V); 499 const SCEV *getCouldNotCompute(); 500 501 /// getSizeOfExpr - Return an expression for sizeof on the given type. 502 /// 503 const SCEV *getSizeOfExpr(const Type *AllocTy); 504 505 /// getAlignOfExpr - Return an expression for alignof on the given type. 506 /// 507 const SCEV *getAlignOfExpr(const Type *AllocTy); 508 509 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 510 /// 511 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 512 513 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 514 /// 515 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 516 517 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 518 /// 519 const SCEV *getNegativeSCEV(const SCEV *V); 520 521 /// getNotSCEV - Return the SCEV object corresponding to ~V. 522 /// 523 const SCEV *getNotSCEV(const SCEV *V); 524 525 /// getMinusSCEV - Return LHS-RHS. 526 /// 527 const SCEV *getMinusSCEV(const SCEV *LHS, 528 const SCEV *RHS); 529 530 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 531 /// of the input value to the specified type. If the type must be 532 /// extended, it is zero extended. 533 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 534 535 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 536 /// of the input value to the specified type. If the type must be 537 /// extended, it is sign extended. 538 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 539 540 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 541 /// the input value to the specified type. If the type must be extended, 542 /// it is zero extended. The conversion must not be narrowing. 543 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 544 545 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 546 /// the input value to the specified type. If the type must be extended, 547 /// it is sign extended. The conversion must not be narrowing. 548 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 549 550 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 551 /// the input value to the specified type. If the type must be extended, 552 /// it is extended with unspecified bits. The conversion must not be 553 /// narrowing. 554 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 555 556 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 557 /// input value to the specified type. The conversion must not be 558 /// widening. 559 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 560 561 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 562 /// the types using zero-extension, and then perform a umax operation 563 /// with them. 564 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 565 const SCEV *RHS); 566 567 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 568 /// the types using zero-extension, and then perform a umin operation 569 /// with them. 570 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 571 const SCEV *RHS); 572 573 /// getSCEVAtScope - Return a SCEV expression for the specified value 574 /// at the specified scope in the program. The L value specifies a loop 575 /// nest to evaluate the expression at, where null is the top-level or a 576 /// specified loop is immediately inside of the loop. 577 /// 578 /// This method can be used to compute the exit value for a variable defined 579 /// in a loop by querying what the value will hold in the parent loop. 580 /// 581 /// In the case that a relevant loop exit value cannot be computed, the 582 /// original value V is returned. 583 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 584 585 /// getSCEVAtScope - This is a convenience function which does 586 /// getSCEVAtScope(getSCEV(V), L). 587 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 588 589 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 590 /// by a conditional between LHS and RHS. This is used to help avoid max 591 /// expressions in loop trip counts, and to eliminate casts. 592 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 593 const SCEV *LHS, const SCEV *RHS); 594 595 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 596 /// protected by a conditional between LHS and RHS. This is used to 597 /// to eliminate casts. 598 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 599 const SCEV *LHS, const SCEV *RHS); 600 601 /// getBackedgeTakenCount - If the specified loop has a predictable 602 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 603 /// object. The backedge-taken count is the number of times the loop header 604 /// will be branched to from within the loop. This is one less than the 605 /// trip count of the loop, since it doesn't count the first iteration, 606 /// when the header is branched to from outside the loop. 607 /// 608 /// Note that it is not valid to call this method on a loop without a 609 /// loop-invariant backedge-taken count (see 610 /// hasLoopInvariantBackedgeTakenCount). 611 /// 612 const SCEV *getBackedgeTakenCount(const Loop *L); 613 614 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 615 /// return the least SCEV value that is known never to be less than the 616 /// actual backedge taken count. 617 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 618 619 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 620 /// has an analyzable loop-invariant backedge-taken count. 621 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 622 623 /// forgetLoop - This method should be called by the client when it has 624 /// changed a loop in a way that may effect ScalarEvolution's ability to 625 /// compute a trip count, or if the loop is deleted. 626 void forgetLoop(const Loop *L); 627 628 /// forgetValue - This method should be called by the client when it has 629 /// changed a value in a way that may effect its value, or which may 630 /// disconnect it from a def-use chain linking it to a loop. 631 void forgetValue(Value *V); 632 633 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 634 /// is guaranteed to end in (at every loop iteration). It is, at the same 635 /// time, the minimum number of times S is divisible by 2. For example, 636 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 637 /// bitwidth of S. 638 uint32_t GetMinTrailingZeros(const SCEV *S); 639 640 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 641 /// 642 ConstantRange getUnsignedRange(const SCEV *S); 643 644 /// getSignedRange - Determine the signed range for a particular SCEV. 645 /// 646 ConstantRange getSignedRange(const SCEV *S); 647 648 /// isKnownNegative - Test if the given expression is known to be negative. 649 /// 650 bool isKnownNegative(const SCEV *S); 651 652 /// isKnownPositive - Test if the given expression is known to be positive. 653 /// 654 bool isKnownPositive(const SCEV *S); 655 656 /// isKnownNonNegative - Test if the given expression is known to be 657 /// non-negative. 658 /// 659 bool isKnownNonNegative(const SCEV *S); 660 661 /// isKnownNonPositive - Test if the given expression is known to be 662 /// non-positive. 663 /// 664 bool isKnownNonPositive(const SCEV *S); 665 666 /// isKnownNonZero - Test if the given expression is known to be 667 /// non-zero. 668 /// 669 bool isKnownNonZero(const SCEV *S); 670 671 /// isKnownPredicate - Test if the given expression is known to satisfy 672 /// the condition described by Pred, LHS, and RHS. 673 /// 674 bool isKnownPredicate(ICmpInst::Predicate Pred, 675 const SCEV *LHS, const SCEV *RHS); 676 677 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 678 /// predicate Pred. Return true iff any changes were made. If the 679 /// operands are provably equal or inequal, LHS and RHS are set to 680 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 681 /// 682 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 683 const SCEV *&LHS, 684 const SCEV *&RHS); 685 686 /// getLoopDisposition - Return the "disposition" of the given SCEV with 687 /// respect to the given loop. 688 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L); 689 690 /// isLoopInvariant - Return true if the value of the given SCEV is 691 /// unchanging in the specified loop. 692 bool isLoopInvariant(const SCEV *S, const Loop *L); 693 694 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 695 /// in a known way in the specified loop. This property being true implies 696 /// that the value is variant in the loop AND that we can emit an expression 697 /// to compute the value of the expression at any particular loop iteration. 698 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 699 700 /// dominates - Return true if elements that makes up the given SCEV 701 /// dominate the specified basic block. 702 bool dominates(const SCEV *S, BasicBlock *BB) const; 703 704 /// properlyDominates - Return true if elements that makes up the given SCEV 705 /// properly dominate the specified basic block. 706 bool properlyDominates(const SCEV *S, BasicBlock *BB) const; 707 708 /// hasOperand - Test whether the given SCEV has Op as a direct or 709 /// indirect operand. 710 bool hasOperand(const SCEV *S, const SCEV *Op) const; 711 712 virtual bool runOnFunction(Function &F); 713 virtual void releaseMemory(); 714 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 715 virtual void print(raw_ostream &OS, const Module* = 0) const; 716 717 private: 718 FoldingSet<SCEV> UniqueSCEVs; 719 BumpPtrAllocator SCEVAllocator; 720 721 /// FirstUnknown - The head of a linked list of all SCEVUnknown 722 /// values that have been allocated. This is used by releaseMemory 723 /// to locate them all and call their destructors. 724 SCEVUnknown *FirstUnknown; 725 }; 726} 727 728#endif 729