ScalarEvolution.h revision 17ead4ff4baceb2c5503f233d0288d363ae44165
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 protected: 74 virtual ~SCEV(); 75 public: 76 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 77 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 78 79 unsigned getSCEVType() const { return SCEVType; } 80 81 /// getType - Return the LLVM type of this SCEV expression. 82 /// 83 virtual const Type *getType() const = 0; 84 85 /// isZero - Return true if the expression is a constant zero. 86 /// 87 bool isZero() const; 88 89 /// isOne - Return true if the expression is a constant one. 90 /// 91 bool isOne() const; 92 93 /// isAllOnesValue - Return true if the expression is a constant 94 /// all-ones value. 95 /// 96 bool isAllOnesValue() const; 97 98 /// hasOperand - Test whether this SCEV has Op as a direct or 99 /// indirect operand. 100 virtual bool hasOperand(const SCEV *Op) const = 0; 101 102 /// dominates - Return true if elements that makes up this SCEV dominates 103 /// the specified basic block. 104 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 105 106 /// properlyDominates - Return true if elements that makes up this SCEV 107 /// properly dominate the specified basic block. 108 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 109 110 /// print - Print out the internal representation of this scalar to the 111 /// specified stream. This should really only be used for debugging 112 /// purposes. 113 virtual void print(raw_ostream &OS) const = 0; 114 115 /// dump - This method is used for debugging. 116 /// 117 void dump() const; 118 }; 119 120 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 121 // temporary FoldingSetNodeID values. 122 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 123 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 124 ID = X.FastID; 125 } 126 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 127 FoldingSetNodeID &TempID) { 128 return ID == X.FastID; 129 } 130 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 131 return X.FastID.ComputeHash(); 132 } 133 }; 134 135 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 136 S.print(OS); 137 return OS; 138 } 139 140 /// SCEVCouldNotCompute - An object of this class is returned by queries that 141 /// could not be answered. For example, if you ask for the number of 142 /// iterations of a linked-list traversal loop, you will get one of these. 143 /// None of the standard SCEV operations are valid on this class, it is just a 144 /// marker. 145 struct SCEVCouldNotCompute : public SCEV { 146 SCEVCouldNotCompute(); 147 148 // None of these methods are valid for this object. 149 virtual const Type *getType() const; 150 virtual void print(raw_ostream &OS) const; 151 virtual bool hasOperand(const SCEV *Op) const; 152 153 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 154 return true; 155 } 156 157 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 158 return true; 159 } 160 161 /// Methods for support type inquiry through isa, cast, and dyn_cast: 162 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 163 static bool classof(const SCEV *S); 164 }; 165 166 /// ScalarEvolution - This class is the main scalar evolution driver. Because 167 /// client code (intentionally) can't do much with the SCEV objects directly, 168 /// they must ask this class for services. 169 /// 170 class ScalarEvolution : public FunctionPass { 171 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 172 /// notified whenever a Value is deleted. 173 class SCEVCallbackVH : public CallbackVH { 174 ScalarEvolution *SE; 175 virtual void deleted(); 176 virtual void allUsesReplacedWith(Value *New); 177 public: 178 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 179 }; 180 181 friend class SCEVCallbackVH; 182 friend class SCEVExpander; 183 friend class SCEVUnknown; 184 185 /// F - The function we are analyzing. 186 /// 187 Function *F; 188 189 /// LI - The loop information for the function we are currently analyzing. 190 /// 191 LoopInfo *LI; 192 193 /// TD - The target data information for the target we are targeting. 194 /// 195 TargetData *TD; 196 197 /// DT - The dominator tree. 198 /// 199 DominatorTree *DT; 200 201 /// CouldNotCompute - This SCEV is used to represent unknown trip 202 /// counts and things. 203 SCEVCouldNotCompute CouldNotCompute; 204 205 /// ValueExprMapType - The typedef for ValueExprMap. 206 /// 207 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 208 ValueExprMapType; 209 210 /// ValueExprMap - This is a cache of the values we have analyzed so far. 211 /// 212 ValueExprMapType ValueExprMap; 213 214 /// BackedgeTakenInfo - Information about the backedge-taken count 215 /// of a loop. This currently includes an exact count and a maximum count. 216 /// 217 struct BackedgeTakenInfo { 218 /// Exact - An expression indicating the exact backedge-taken count of 219 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 220 const SCEV *Exact; 221 222 /// Max - An expression indicating the least maximum backedge-taken 223 /// count of the loop that is known, or a SCEVCouldNotCompute. 224 const SCEV *Max; 225 226 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 227 Exact(exact), Max(exact) {} 228 229 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 230 Exact(exact), Max(max) {} 231 232 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 233 /// computed information, or whether it's all SCEVCouldNotCompute 234 /// values. 235 bool hasAnyInfo() const { 236 return !isa<SCEVCouldNotCompute>(Exact) || 237 !isa<SCEVCouldNotCompute>(Max); 238 } 239 }; 240 241 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 242 /// this function as they are computed. 243 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 244 245 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 246 /// the PHI instructions that we attempt to compute constant evolutions for. 247 /// This allows us to avoid potentially expensive recomputation of these 248 /// properties. An instruction maps to null if we are unable to compute its 249 /// exit value. 250 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 251 252 /// ValuesAtScopes - This map contains entries for all the expressions 253 /// that we attempt to compute getSCEVAtScope information for, which can 254 /// be expensive in extreme cases. 255 std::map<const SCEV *, 256 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 257 258 /// UnsignedRanges - Memoized results from getUnsignedRange 259 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 260 261 /// SignedRanges - Memoized results from getSignedRange 262 DenseMap<const SCEV *, ConstantRange> SignedRanges; 263 264 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 265 const ConstantRange &setUnsignedRange(const SCEV *S, 266 const ConstantRange &CR) { 267 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 268 UnsignedRanges.insert(std::make_pair(S, CR)); 269 if (!Pair.second) 270 Pair.first->second = CR; 271 return Pair.first->second; 272 } 273 274 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 275 const ConstantRange &setSignedRange(const SCEV *S, 276 const ConstantRange &CR) { 277 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 278 SignedRanges.insert(std::make_pair(S, CR)); 279 if (!Pair.second) 280 Pair.first->second = CR; 281 return Pair.first->second; 282 } 283 284 /// createSCEV - We know that there is no SCEV for the specified value. 285 /// Analyze the expression. 286 const SCEV *createSCEV(Value *V); 287 288 /// createNodeForPHI - Provide the special handling we need to analyze PHI 289 /// SCEVs. 290 const SCEV *createNodeForPHI(PHINode *PN); 291 292 /// createNodeForGEP - Provide the special handling we need to analyze GEP 293 /// SCEVs. 294 const SCEV *createNodeForGEP(GEPOperator *GEP); 295 296 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 297 /// at most once for each SCEV+Loop pair. 298 /// 299 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 300 301 /// ForgetSymbolicValue - This looks up computed SCEV values for all 302 /// instructions that depend on the given instruction and removes them from 303 /// the ValueExprMap map if they reference SymName. This is used during PHI 304 /// resolution. 305 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 306 307 /// getBECount - Subtract the end and start values and divide by the step, 308 /// rounding up, to get the number of times the backedge is executed. Return 309 /// CouldNotCompute if an intermediate computation overflows. 310 const SCEV *getBECount(const SCEV *Start, 311 const SCEV *End, 312 const SCEV *Step, 313 bool NoWrap); 314 315 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 316 /// loop, lazily computing new values if the loop hasn't been analyzed 317 /// yet. 318 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 319 320 /// ComputeBackedgeTakenCount - Compute the number of times the specified 321 /// loop will iterate. 322 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 323 324 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 325 /// backedge of the specified loop will execute if it exits via the 326 /// specified block. 327 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 328 BasicBlock *ExitingBlock); 329 330 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 331 /// backedge of the specified loop will execute if its exit condition 332 /// were a conditional branch of ExitCond, TBB, and FBB. 333 BackedgeTakenInfo 334 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 335 Value *ExitCond, 336 BasicBlock *TBB, 337 BasicBlock *FBB); 338 339 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 340 /// times the backedge of the specified loop will execute if its exit 341 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 342 /// and FBB. 343 BackedgeTakenInfo 344 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 345 ICmpInst *ExitCond, 346 BasicBlock *TBB, 347 BasicBlock *FBB); 348 349 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 350 /// of 'icmp op load X, cst', try to see if we can compute the 351 /// backedge-taken count. 352 BackedgeTakenInfo 353 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 354 Constant *RHS, 355 const Loop *L, 356 ICmpInst::Predicate p); 357 358 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 359 /// a constant number of times (the condition evolves only from constants), 360 /// try to evaluate a few iterations of the loop until we get the exit 361 /// condition gets a value of ExitWhen (true or false). If we cannot 362 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 363 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 364 Value *Cond, 365 bool ExitWhen); 366 367 /// HowFarToZero - Return the number of times a backedge comparing the 368 /// specified value to zero will execute. If not computable, return 369 /// CouldNotCompute. 370 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 371 372 /// HowFarToNonZero - Return the number of times a backedge checking the 373 /// specified value for nonzero will execute. If not computable, return 374 /// CouldNotCompute. 375 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 376 377 /// HowManyLessThans - Return the number of times a backedge containing the 378 /// specified less-than comparison will execute. If not computable, return 379 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 380 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 381 const Loop *L, bool isSigned); 382 383 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 384 /// (which may not be an immediate predecessor) which has exactly one 385 /// successor from which BB is reachable, or null if no such block is 386 /// found. 387 std::pair<BasicBlock *, BasicBlock *> 388 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 389 390 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 391 /// RHS is true whenever the given FoundCondValue value evaluates to true. 392 bool isImpliedCond(ICmpInst::Predicate Pred, 393 const SCEV *LHS, const SCEV *RHS, 394 Value *FoundCondValue, 395 bool Inverse); 396 397 /// isImpliedCondOperands - Test whether the condition described by Pred, 398 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 399 /// and FoundRHS is true. 400 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 401 const SCEV *LHS, const SCEV *RHS, 402 const SCEV *FoundLHS, const SCEV *FoundRHS); 403 404 /// isImpliedCondOperandsHelper - Test whether the condition described by 405 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 406 /// FoundLHS, and FoundRHS is true. 407 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 408 const SCEV *LHS, const SCEV *RHS, 409 const SCEV *FoundLHS, const SCEV *FoundRHS); 410 411 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 412 /// in the header of its containing loop, we know the loop executes a 413 /// constant number of times, and the PHI node is just a recurrence 414 /// involving constants, fold it. 415 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 416 const Loop *L); 417 418 /// isKnownPredicateWithRanges - Test if the given expression is known to 419 /// satisfy the condition described by Pred and the known constant ranges 420 /// of LHS and RHS. 421 /// 422 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 423 const SCEV *LHS, const SCEV *RHS); 424 425 public: 426 static char ID; // Pass identification, replacement for typeid 427 ScalarEvolution(); 428 429 LLVMContext &getContext() const { return F->getContext(); } 430 431 /// isSCEVable - Test if values of the given type are analyzable within 432 /// the SCEV framework. This primarily includes integer types, and it 433 /// can optionally include pointer types if the ScalarEvolution class 434 /// has access to target-specific information. 435 bool isSCEVable(const Type *Ty) const; 436 437 /// getTypeSizeInBits - Return the size in bits of the specified type, 438 /// for which isSCEVable must return true. 439 uint64_t getTypeSizeInBits(const Type *Ty) const; 440 441 /// getEffectiveSCEVType - Return a type with the same bitwidth as 442 /// the given type and which represents how SCEV will treat the given 443 /// type, for which isSCEVable must return true. For pointer types, 444 /// this is the pointer-sized integer type. 445 const Type *getEffectiveSCEVType(const Type *Ty) const; 446 447 /// getSCEV - Return a SCEV expression for the full generality of the 448 /// specified expression. 449 const SCEV *getSCEV(Value *V); 450 451 const SCEV *getConstant(ConstantInt *V); 452 const SCEV *getConstant(const APInt& Val); 453 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 454 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 455 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 456 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 457 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 458 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 459 bool HasNUW = false, bool HasNSW = false); 460 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 461 bool HasNUW = false, bool HasNSW = false) { 462 SmallVector<const SCEV *, 2> Ops; 463 Ops.push_back(LHS); 464 Ops.push_back(RHS); 465 return getAddExpr(Ops, HasNUW, HasNSW); 466 } 467 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 468 const SCEV *Op2, 469 bool HasNUW = false, bool HasNSW = false) { 470 SmallVector<const SCEV *, 3> Ops; 471 Ops.push_back(Op0); 472 Ops.push_back(Op1); 473 Ops.push_back(Op2); 474 return getAddExpr(Ops, HasNUW, HasNSW); 475 } 476 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 477 bool HasNUW = false, bool HasNSW = false); 478 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 479 bool HasNUW = false, bool HasNSW = false) { 480 SmallVector<const SCEV *, 2> Ops; 481 Ops.push_back(LHS); 482 Ops.push_back(RHS); 483 return getMulExpr(Ops, HasNUW, HasNSW); 484 } 485 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 486 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 487 const Loop *L, 488 bool HasNUW = false, bool HasNSW = false); 489 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 490 const Loop *L, 491 bool HasNUW = false, bool HasNSW = false); 492 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 493 const Loop *L, 494 bool HasNUW = false, bool HasNSW = false) { 495 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 496 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 497 } 498 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 499 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 500 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 501 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 502 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 503 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 504 const SCEV *getUnknown(Value *V); 505 const SCEV *getCouldNotCompute(); 506 507 /// getSizeOfExpr - Return an expression for sizeof on the given type. 508 /// 509 const SCEV *getSizeOfExpr(const Type *AllocTy); 510 511 /// getAlignOfExpr - Return an expression for alignof on the given type. 512 /// 513 const SCEV *getAlignOfExpr(const Type *AllocTy); 514 515 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 516 /// 517 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 518 519 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 520 /// 521 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 522 523 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 524 /// 525 const SCEV *getNegativeSCEV(const SCEV *V); 526 527 /// getNotSCEV - Return the SCEV object corresponding to ~V. 528 /// 529 const SCEV *getNotSCEV(const SCEV *V); 530 531 /// getMinusSCEV - Return LHS-RHS. 532 /// 533 const SCEV *getMinusSCEV(const SCEV *LHS, 534 const SCEV *RHS); 535 536 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 537 /// of the input value to the specified type. If the type must be 538 /// extended, it is zero extended. 539 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 540 541 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 542 /// of the input value to the specified type. If the type must be 543 /// extended, it is sign extended. 544 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 545 546 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 547 /// the input value to the specified type. If the type must be extended, 548 /// it is zero extended. The conversion must not be narrowing. 549 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 550 551 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 552 /// the input value to the specified type. If the type must be extended, 553 /// it is sign extended. The conversion must not be narrowing. 554 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 555 556 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 557 /// the input value to the specified type. If the type must be extended, 558 /// it is extended with unspecified bits. The conversion must not be 559 /// narrowing. 560 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 561 562 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 563 /// input value to the specified type. The conversion must not be 564 /// widening. 565 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 566 567 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 568 /// the types using zero-extension, and then perform a umax operation 569 /// with them. 570 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 571 const SCEV *RHS); 572 573 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 574 /// the types using zero-extension, and then perform a umin operation 575 /// with them. 576 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 577 const SCEV *RHS); 578 579 /// getSCEVAtScope - Return a SCEV expression for the specified value 580 /// at the specified scope in the program. The L value specifies a loop 581 /// nest to evaluate the expression at, where null is the top-level or a 582 /// specified loop is immediately inside of the loop. 583 /// 584 /// This method can be used to compute the exit value for a variable defined 585 /// in a loop by querying what the value will hold in the parent loop. 586 /// 587 /// In the case that a relevant loop exit value cannot be computed, the 588 /// original value V is returned. 589 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 590 591 /// getSCEVAtScope - This is a convenience function which does 592 /// getSCEVAtScope(getSCEV(V), L). 593 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 594 595 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 596 /// by a conditional between LHS and RHS. This is used to help avoid max 597 /// expressions in loop trip counts, and to eliminate casts. 598 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 599 const SCEV *LHS, const SCEV *RHS); 600 601 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 602 /// protected by a conditional between LHS and RHS. This is used to 603 /// to eliminate casts. 604 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 605 const SCEV *LHS, const SCEV *RHS); 606 607 /// getBackedgeTakenCount - If the specified loop has a predictable 608 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 609 /// object. The backedge-taken count is the number of times the loop header 610 /// will be branched to from within the loop. This is one less than the 611 /// trip count of the loop, since it doesn't count the first iteration, 612 /// when the header is branched to from outside the loop. 613 /// 614 /// Note that it is not valid to call this method on a loop without a 615 /// loop-invariant backedge-taken count (see 616 /// hasLoopInvariantBackedgeTakenCount). 617 /// 618 const SCEV *getBackedgeTakenCount(const Loop *L); 619 620 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 621 /// return the least SCEV value that is known never to be less than the 622 /// actual backedge taken count. 623 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 624 625 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 626 /// has an analyzable loop-invariant backedge-taken count. 627 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 628 629 /// forgetLoop - This method should be called by the client when it has 630 /// changed a loop in a way that may effect ScalarEvolution's ability to 631 /// compute a trip count, or if the loop is deleted. 632 void forgetLoop(const Loop *L); 633 634 /// forgetValue - This method should be called by the client when it has 635 /// changed a value in a way that may effect its value, or which may 636 /// disconnect it from a def-use chain linking it to a loop. 637 void forgetValue(Value *V); 638 639 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 640 /// is guaranteed to end in (at every loop iteration). It is, at the same 641 /// time, the minimum number of times S is divisible by 2. For example, 642 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 643 /// bitwidth of S. 644 uint32_t GetMinTrailingZeros(const SCEV *S); 645 646 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 647 /// 648 ConstantRange getUnsignedRange(const SCEV *S); 649 650 /// getSignedRange - Determine the signed range for a particular SCEV. 651 /// 652 ConstantRange getSignedRange(const SCEV *S); 653 654 /// isKnownNegative - Test if the given expression is known to be negative. 655 /// 656 bool isKnownNegative(const SCEV *S); 657 658 /// isKnownPositive - Test if the given expression is known to be positive. 659 /// 660 bool isKnownPositive(const SCEV *S); 661 662 /// isKnownNonNegative - Test if the given expression is known to be 663 /// non-negative. 664 /// 665 bool isKnownNonNegative(const SCEV *S); 666 667 /// isKnownNonPositive - Test if the given expression is known to be 668 /// non-positive. 669 /// 670 bool isKnownNonPositive(const SCEV *S); 671 672 /// isKnownNonZero - Test if the given expression is known to be 673 /// non-zero. 674 /// 675 bool isKnownNonZero(const SCEV *S); 676 677 /// isKnownPredicate - Test if the given expression is known to satisfy 678 /// the condition described by Pred, LHS, and RHS. 679 /// 680 bool isKnownPredicate(ICmpInst::Predicate Pred, 681 const SCEV *LHS, const SCEV *RHS); 682 683 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 684 /// predicate Pred. Return true iff any changes were made. If the 685 /// operands are provably equal or inequal, LHS and RHS are set to 686 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 687 /// 688 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 689 const SCEV *&LHS, 690 const SCEV *&RHS); 691 692 /// isLoopInvariant - Return true if the value of the given SCEV is 693 /// unchanging in the specified loop. 694 bool isLoopInvariant(const SCEV *S, const Loop *L); 695 696 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 697 /// in a known way in the specified loop. This property being true implies 698 /// that the value is variant in the loop AND that we can emit an expression 699 /// to compute the value of the expression at any particular loop iteration. 700 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 701 702 virtual bool runOnFunction(Function &F); 703 virtual void releaseMemory(); 704 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 705 virtual void print(raw_ostream &OS, const Module* = 0) const; 706 707 private: 708 FoldingSet<SCEV> UniqueSCEVs; 709 BumpPtrAllocator SCEVAllocator; 710 711 /// FirstUnknown - The head of a linked list of all SCEVUnknown 712 /// values that have been allocated. This is used by releaseMemory 713 /// to locate them all and call their destructors. 714 SCEVUnknown *FirstUnknown; 715 }; 716} 717 718#endif 719