ScalarEvolution.h revision dc0e8fb9f9512622f55f73e1a434caa5c0915694
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 /// print - Print out the internal representation of this scalar to the 103 /// specified stream. This should really only be used for debugging 104 /// purposes. 105 virtual void print(raw_ostream &OS) const = 0; 106 107 /// dump - This method is used for debugging. 108 /// 109 void dump() const; 110 }; 111 112 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 113 // temporary FoldingSetNodeID values. 114 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 115 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 116 ID = X.FastID; 117 } 118 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 119 FoldingSetNodeID &TempID) { 120 return ID == X.FastID; 121 } 122 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 123 return X.FastID.ComputeHash(); 124 } 125 }; 126 127 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 128 S.print(OS); 129 return OS; 130 } 131 132 /// SCEVCouldNotCompute - An object of this class is returned by queries that 133 /// could not be answered. For example, if you ask for the number of 134 /// iterations of a linked-list traversal loop, you will get one of these. 135 /// None of the standard SCEV operations are valid on this class, it is just a 136 /// marker. 137 struct SCEVCouldNotCompute : public SCEV { 138 SCEVCouldNotCompute(); 139 140 // None of these methods are valid for this object. 141 virtual const Type *getType() const; 142 virtual void print(raw_ostream &OS) const; 143 virtual bool hasOperand(const SCEV *Op) const; 144 145 /// Methods for support type inquiry through isa, cast, and dyn_cast: 146 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 147 static bool classof(const SCEV *S); 148 }; 149 150 /// ScalarEvolution - This class is the main scalar evolution driver. Because 151 /// client code (intentionally) can't do much with the SCEV objects directly, 152 /// they must ask this class for services. 153 /// 154 class ScalarEvolution : public FunctionPass { 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 /// UnsignedRanges - Memoized results from getUnsignedRange 243 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 244 245 /// SignedRanges - Memoized results from getSignedRange 246 DenseMap<const SCEV *, ConstantRange> SignedRanges; 247 248 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV. 249 const ConstantRange &setUnsignedRange(const SCEV *S, 250 const ConstantRange &CR) { 251 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 252 UnsignedRanges.insert(std::make_pair(S, CR)); 253 if (!Pair.second) 254 Pair.first->second = CR; 255 return Pair.first->second; 256 } 257 258 /// setUnsignedRange - Set the memoized signed range for the given SCEV. 259 const ConstantRange &setSignedRange(const SCEV *S, 260 const ConstantRange &CR) { 261 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair = 262 SignedRanges.insert(std::make_pair(S, CR)); 263 if (!Pair.second) 264 Pair.first->second = CR; 265 return Pair.first->second; 266 } 267 268 /// createSCEV - We know that there is no SCEV for the specified value. 269 /// Analyze the expression. 270 const SCEV *createSCEV(Value *V); 271 272 /// createNodeForPHI - Provide the special handling we need to analyze PHI 273 /// SCEVs. 274 const SCEV *createNodeForPHI(PHINode *PN); 275 276 /// createNodeForGEP - Provide the special handling we need to analyze GEP 277 /// SCEVs. 278 const SCEV *createNodeForGEP(GEPOperator *GEP); 279 280 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 281 /// at most once for each SCEV+Loop pair. 282 /// 283 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 284 285 /// ForgetSymbolicValue - This looks up computed SCEV values for all 286 /// instructions that depend on the given instruction and removes them from 287 /// the ValueExprMap map if they reference SymName. This is used during PHI 288 /// resolution. 289 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 290 291 /// getBECount - Subtract the end and start values and divide by the step, 292 /// rounding up, to get the number of times the backedge is executed. Return 293 /// CouldNotCompute if an intermediate computation overflows. 294 const SCEV *getBECount(const SCEV *Start, 295 const SCEV *End, 296 const SCEV *Step, 297 bool NoWrap); 298 299 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 300 /// loop, lazily computing new values if the loop hasn't been analyzed 301 /// yet. 302 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 303 304 /// ComputeBackedgeTakenCount - Compute the number of times the specified 305 /// loop will iterate. 306 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 307 308 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 309 /// backedge of the specified loop will execute if it exits via the 310 /// specified block. 311 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 312 BasicBlock *ExitingBlock); 313 314 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 315 /// backedge of the specified loop will execute if its exit condition 316 /// were a conditional branch of ExitCond, TBB, and FBB. 317 BackedgeTakenInfo 318 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 319 Value *ExitCond, 320 BasicBlock *TBB, 321 BasicBlock *FBB); 322 323 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 324 /// times the backedge of the specified loop will execute if its exit 325 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 326 /// and FBB. 327 BackedgeTakenInfo 328 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 329 ICmpInst *ExitCond, 330 BasicBlock *TBB, 331 BasicBlock *FBB); 332 333 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 334 /// of 'icmp op load X, cst', try to see if we can compute the 335 /// backedge-taken count. 336 BackedgeTakenInfo 337 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 338 Constant *RHS, 339 const Loop *L, 340 ICmpInst::Predicate p); 341 342 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 343 /// a constant number of times (the condition evolves only from constants), 344 /// try to evaluate a few iterations of the loop until we get the exit 345 /// condition gets a value of ExitWhen (true or false). If we cannot 346 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 347 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 348 Value *Cond, 349 bool ExitWhen); 350 351 /// HowFarToZero - Return the number of times a backedge comparing the 352 /// specified value to zero will execute. If not computable, return 353 /// CouldNotCompute. 354 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 355 356 /// HowFarToNonZero - Return the number of times a backedge checking the 357 /// specified value for nonzero will execute. If not computable, return 358 /// CouldNotCompute. 359 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 360 361 /// HowManyLessThans - Return the number of times a backedge containing the 362 /// specified less-than comparison will execute. If not computable, return 363 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 364 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 365 const Loop *L, bool isSigned); 366 367 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 368 /// (which may not be an immediate predecessor) which has exactly one 369 /// successor from which BB is reachable, or null if no such block is 370 /// found. 371 std::pair<BasicBlock *, BasicBlock *> 372 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 373 374 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 375 /// RHS is true whenever the given FoundCondValue value evaluates to true. 376 bool isImpliedCond(ICmpInst::Predicate Pred, 377 const SCEV *LHS, const SCEV *RHS, 378 Value *FoundCondValue, 379 bool Inverse); 380 381 /// isImpliedCondOperands - Test whether the condition described by Pred, 382 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 383 /// and FoundRHS is true. 384 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 385 const SCEV *LHS, const SCEV *RHS, 386 const SCEV *FoundLHS, const SCEV *FoundRHS); 387 388 /// isImpliedCondOperandsHelper - Test whether the condition described by 389 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 390 /// FoundLHS, and FoundRHS is true. 391 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 392 const SCEV *LHS, const SCEV *RHS, 393 const SCEV *FoundLHS, const SCEV *FoundRHS); 394 395 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 396 /// in the header of its containing loop, we know the loop executes a 397 /// constant number of times, and the PHI node is just a recurrence 398 /// involving constants, fold it. 399 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 400 const Loop *L); 401 402 /// isKnownPredicateWithRanges - Test if the given expression is known to 403 /// satisfy the condition described by Pred and the known constant ranges 404 /// of LHS and RHS. 405 /// 406 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 407 const SCEV *LHS, const SCEV *RHS); 408 409 public: 410 static char ID; // Pass identification, replacement for typeid 411 ScalarEvolution(); 412 413 LLVMContext &getContext() const { return F->getContext(); } 414 415 /// isSCEVable - Test if values of the given type are analyzable within 416 /// the SCEV framework. This primarily includes integer types, and it 417 /// can optionally include pointer types if the ScalarEvolution class 418 /// has access to target-specific information. 419 bool isSCEVable(const Type *Ty) const; 420 421 /// getTypeSizeInBits - Return the size in bits of the specified type, 422 /// for which isSCEVable must return true. 423 uint64_t getTypeSizeInBits(const Type *Ty) const; 424 425 /// getEffectiveSCEVType - Return a type with the same bitwidth as 426 /// the given type and which represents how SCEV will treat the given 427 /// type, for which isSCEVable must return true. For pointer types, 428 /// this is the pointer-sized integer type. 429 const Type *getEffectiveSCEVType(const Type *Ty) const; 430 431 /// getSCEV - Return a SCEV expression for the full generality of the 432 /// specified expression. 433 const SCEV *getSCEV(Value *V); 434 435 const SCEV *getConstant(ConstantInt *V); 436 const SCEV *getConstant(const APInt& Val); 437 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 438 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 439 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 440 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 441 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 442 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 443 bool HasNUW = false, bool HasNSW = false); 444 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 445 bool HasNUW = false, bool HasNSW = false) { 446 SmallVector<const SCEV *, 2> Ops; 447 Ops.push_back(LHS); 448 Ops.push_back(RHS); 449 return getAddExpr(Ops, HasNUW, HasNSW); 450 } 451 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 452 const SCEV *Op2, 453 bool HasNUW = false, bool HasNSW = false) { 454 SmallVector<const SCEV *, 3> Ops; 455 Ops.push_back(Op0); 456 Ops.push_back(Op1); 457 Ops.push_back(Op2); 458 return getAddExpr(Ops, HasNUW, HasNSW); 459 } 460 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 461 bool HasNUW = false, bool HasNSW = false); 462 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 463 bool HasNUW = false, bool HasNSW = false) { 464 SmallVector<const SCEV *, 2> Ops; 465 Ops.push_back(LHS); 466 Ops.push_back(RHS); 467 return getMulExpr(Ops, HasNUW, HasNSW); 468 } 469 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 470 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 471 const Loop *L, 472 bool HasNUW = false, bool HasNSW = false); 473 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 474 const Loop *L, 475 bool HasNUW = false, bool HasNSW = false); 476 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 477 const Loop *L, 478 bool HasNUW = false, bool HasNSW = false) { 479 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 480 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 481 } 482 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 483 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 484 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 485 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 486 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 487 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 488 const SCEV *getUnknown(Value *V); 489 const SCEV *getCouldNotCompute(); 490 491 /// getSizeOfExpr - Return an expression for sizeof on the given type. 492 /// 493 const SCEV *getSizeOfExpr(const Type *AllocTy); 494 495 /// getAlignOfExpr - Return an expression for alignof on the given type. 496 /// 497 const SCEV *getAlignOfExpr(const Type *AllocTy); 498 499 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 500 /// 501 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 502 503 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 504 /// 505 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 506 507 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 508 /// 509 const SCEV *getNegativeSCEV(const SCEV *V); 510 511 /// getNotSCEV - Return the SCEV object corresponding to ~V. 512 /// 513 const SCEV *getNotSCEV(const SCEV *V); 514 515 /// getMinusSCEV - Return LHS-RHS. 516 /// 517 const SCEV *getMinusSCEV(const SCEV *LHS, 518 const SCEV *RHS); 519 520 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 521 /// of the input value to the specified type. If the type must be 522 /// extended, it is zero extended. 523 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 524 525 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 526 /// of the input value to the specified type. If the type must be 527 /// extended, it is sign extended. 528 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 529 530 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 531 /// the input value to the specified type. If the type must be extended, 532 /// it is zero extended. The conversion must not be narrowing. 533 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 534 535 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 536 /// the input value to the specified type. If the type must be extended, 537 /// it is sign extended. The conversion must not be narrowing. 538 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 539 540 /// getNoopOrAnyExtend - 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 extended with unspecified bits. The conversion must not be 543 /// narrowing. 544 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 545 546 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 547 /// input value to the specified type. The conversion must not be 548 /// widening. 549 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 550 551 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 552 /// the types using zero-extension, and then perform a umax operation 553 /// with them. 554 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 555 const SCEV *RHS); 556 557 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 558 /// the types using zero-extension, and then perform a umin operation 559 /// with them. 560 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 561 const SCEV *RHS); 562 563 /// getSCEVAtScope - Return a SCEV expression for the specified value 564 /// at the specified scope in the program. The L value specifies a loop 565 /// nest to evaluate the expression at, where null is the top-level or a 566 /// specified loop is immediately inside of the loop. 567 /// 568 /// This method can be used to compute the exit value for a variable defined 569 /// in a loop by querying what the value will hold in the parent loop. 570 /// 571 /// In the case that a relevant loop exit value cannot be computed, the 572 /// original value V is returned. 573 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 574 575 /// getSCEVAtScope - This is a convenience function which does 576 /// getSCEVAtScope(getSCEV(V), L). 577 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 578 579 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 580 /// by a conditional between LHS and RHS. This is used to help avoid max 581 /// expressions in loop trip counts, and to eliminate casts. 582 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 583 const SCEV *LHS, const SCEV *RHS); 584 585 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 586 /// protected by a conditional between LHS and RHS. This is used to 587 /// to eliminate casts. 588 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 589 const SCEV *LHS, const SCEV *RHS); 590 591 /// getBackedgeTakenCount - If the specified loop has a predictable 592 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 593 /// object. The backedge-taken count is the number of times the loop header 594 /// will be branched to from within the loop. This is one less than the 595 /// trip count of the loop, since it doesn't count the first iteration, 596 /// when the header is branched to from outside the loop. 597 /// 598 /// Note that it is not valid to call this method on a loop without a 599 /// loop-invariant backedge-taken count (see 600 /// hasLoopInvariantBackedgeTakenCount). 601 /// 602 const SCEV *getBackedgeTakenCount(const Loop *L); 603 604 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 605 /// return the least SCEV value that is known never to be less than the 606 /// actual backedge taken count. 607 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 608 609 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 610 /// has an analyzable loop-invariant backedge-taken count. 611 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 612 613 /// forgetLoop - This method should be called by the client when it has 614 /// changed a loop in a way that may effect ScalarEvolution's ability to 615 /// compute a trip count, or if the loop is deleted. 616 void forgetLoop(const Loop *L); 617 618 /// forgetValue - This method should be called by the client when it has 619 /// changed a value in a way that may effect its value, or which may 620 /// disconnect it from a def-use chain linking it to a loop. 621 void forgetValue(Value *V); 622 623 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 624 /// is guaranteed to end in (at every loop iteration). It is, at the same 625 /// time, the minimum number of times S is divisible by 2. For example, 626 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 627 /// bitwidth of S. 628 uint32_t GetMinTrailingZeros(const SCEV *S); 629 630 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 631 /// 632 ConstantRange getUnsignedRange(const SCEV *S); 633 634 /// getSignedRange - Determine the signed range for a particular SCEV. 635 /// 636 ConstantRange getSignedRange(const SCEV *S); 637 638 /// isKnownNegative - Test if the given expression is known to be negative. 639 /// 640 bool isKnownNegative(const SCEV *S); 641 642 /// isKnownPositive - Test if the given expression is known to be positive. 643 /// 644 bool isKnownPositive(const SCEV *S); 645 646 /// isKnownNonNegative - Test if the given expression is known to be 647 /// non-negative. 648 /// 649 bool isKnownNonNegative(const SCEV *S); 650 651 /// isKnownNonPositive - Test if the given expression is known to be 652 /// non-positive. 653 /// 654 bool isKnownNonPositive(const SCEV *S); 655 656 /// isKnownNonZero - Test if the given expression is known to be 657 /// non-zero. 658 /// 659 bool isKnownNonZero(const SCEV *S); 660 661 /// isKnownPredicate - Test if the given expression is known to satisfy 662 /// the condition described by Pred, LHS, and RHS. 663 /// 664 bool isKnownPredicate(ICmpInst::Predicate Pred, 665 const SCEV *LHS, const SCEV *RHS); 666 667 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 668 /// predicate Pred. Return true iff any changes were made. If the 669 /// operands are provably equal or inequal, LHS and RHS are set to 670 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 671 /// 672 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 673 const SCEV *&LHS, 674 const SCEV *&RHS); 675 676 /// isLoopInvariant - Return true if the value of the given SCEV is 677 /// unchanging in the specified loop. 678 bool isLoopInvariant(const SCEV *S, const Loop *L); 679 680 /// hasComputableLoopEvolution - Return true if the given SCEV changes value 681 /// in a known way in the specified loop. This property being true implies 682 /// that the value is variant in the loop AND that we can emit an expression 683 /// to compute the value of the expression at any particular loop iteration. 684 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L); 685 686 /// dominates - Return true if elements that makes up the given SCEV 687 /// dominate the specified basic block. 688 bool dominates(const SCEV *S, BasicBlock *BB) const; 689 690 /// properlyDominates - Return true if elements that makes up the given SCEV 691 /// properly dominate the specified basic block. 692 bool properlyDominates(const SCEV *S, BasicBlock *BB) const; 693 694 virtual bool runOnFunction(Function &F); 695 virtual void releaseMemory(); 696 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 697 virtual void print(raw_ostream &OS, const Module* = 0) const; 698 699 private: 700 FoldingSet<SCEV> UniqueSCEVs; 701 BumpPtrAllocator SCEVAllocator; 702 703 /// FirstUnknown - The head of a linked list of all SCEVUnknown 704 /// values that have been allocated. This is used by releaseMemory 705 /// to locate them all and call their destructors. 706 SCEVUnknown *FirstUnknown; 707 }; 708} 709 710#endif 711