ScalarEvolution.h revision e8ac3f3be4b4df619368bf46aa4ed91557b5f76e
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 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 82 /// the specified loop. 83 virtual bool isLoopInvariant(const Loop *L) const = 0; 84 85 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 86 /// known way in the specified loop. This property being true implies that 87 /// the value is variant in the loop AND that we can emit an expression to 88 /// compute the value of the expression at any particular loop iteration. 89 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 90 91 /// getType - Return the LLVM type of this SCEV expression. 92 /// 93 virtual const Type *getType() const = 0; 94 95 /// isZero - Return true if the expression is a constant zero. 96 /// 97 bool isZero() const; 98 99 /// isOne - Return true if the expression is a constant one. 100 /// 101 bool isOne() const; 102 103 /// isAllOnesValue - Return true if the expression is a constant 104 /// all-ones value. 105 /// 106 bool isAllOnesValue() const; 107 108 /// hasOperand - Test whether this SCEV has Op as a direct or 109 /// indirect operand. 110 virtual bool hasOperand(const SCEV *Op) const = 0; 111 112 /// dominates - Return true if elements that makes up this SCEV dominates 113 /// the specified basic block. 114 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 115 116 /// properlyDominates - Return true if elements that makes up this SCEV 117 /// properly dominate the specified basic block. 118 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 119 120 /// print - Print out the internal representation of this scalar to the 121 /// specified stream. This should really only be used for debugging 122 /// purposes. 123 virtual void print(raw_ostream &OS) const = 0; 124 125 /// dump - This method is used for debugging. 126 /// 127 void dump() const; 128 }; 129 130 // Specialize FoldingSetTrait for SCEV to avoid needing to compute 131 // temporary FoldingSetNodeID values. 132 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> { 133 static void Profile(const SCEV &X, FoldingSetNodeID& ID) { 134 ID = X.FastID; 135 } 136 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, 137 FoldingSetNodeID &TempID) { 138 return ID == X.FastID; 139 } 140 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) { 141 return X.FastID.ComputeHash(); 142 } 143 }; 144 145 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 146 S.print(OS); 147 return OS; 148 } 149 150 /// SCEVCouldNotCompute - An object of this class is returned by queries that 151 /// could not be answered. For example, if you ask for the number of 152 /// iterations of a linked-list traversal loop, you will get one of these. 153 /// None of the standard SCEV operations are valid on this class, it is just a 154 /// marker. 155 struct SCEVCouldNotCompute : public SCEV { 156 SCEVCouldNotCompute(); 157 158 // None of these methods are valid for this object. 159 virtual bool isLoopInvariant(const Loop *L) const; 160 virtual const Type *getType() const; 161 virtual bool hasComputableLoopEvolution(const Loop *L) const; 162 virtual void print(raw_ostream &OS) const; 163 virtual bool hasOperand(const SCEV *Op) const; 164 165 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 166 return true; 167 } 168 169 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 170 return true; 171 } 172 173 /// Methods for support type inquiry through isa, cast, and dyn_cast: 174 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 175 static bool classof(const SCEV *S); 176 }; 177 178 /// ScalarEvolution - This class is the main scalar evolution driver. Because 179 /// client code (intentionally) can't do much with the SCEV objects directly, 180 /// they must ask this class for services. 181 /// 182 class ScalarEvolution : public FunctionPass { 183 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 184 /// notified whenever a Value is deleted. 185 class SCEVCallbackVH : public CallbackVH { 186 ScalarEvolution *SE; 187 virtual void deleted(); 188 virtual void allUsesReplacedWith(Value *New); 189 public: 190 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 191 }; 192 193 friend class SCEVCallbackVH; 194 friend class SCEVExpander; 195 friend class SCEVUnknown; 196 197 /// F - The function we are analyzing. 198 /// 199 Function *F; 200 201 /// LI - The loop information for the function we are currently analyzing. 202 /// 203 LoopInfo *LI; 204 205 /// TD - The target data information for the target we are targeting. 206 /// 207 TargetData *TD; 208 209 /// DT - The dominator tree. 210 /// 211 DominatorTree *DT; 212 213 /// CouldNotCompute - This SCEV is used to represent unknown trip 214 /// counts and things. 215 SCEVCouldNotCompute CouldNotCompute; 216 217 /// ValueExprMapType - The typedef for ValueExprMap. 218 /// 219 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> > 220 ValueExprMapType; 221 222 /// ValueExprMap - This is a cache of the values we have analyzed so far. 223 /// 224 ValueExprMapType ValueExprMap; 225 226 /// BackedgeTakenInfo - Information about the backedge-taken count 227 /// of a loop. This currently includes an exact count and a maximum count. 228 /// 229 struct BackedgeTakenInfo { 230 /// Exact - An expression indicating the exact backedge-taken count of 231 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 232 const SCEV *Exact; 233 234 /// Max - An expression indicating the least maximum backedge-taken 235 /// count of the loop that is known, or a SCEVCouldNotCompute. 236 const SCEV *Max; 237 238 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 239 Exact(exact), Max(exact) {} 240 241 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 242 Exact(exact), Max(max) {} 243 244 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 245 /// computed information, or whether it's all SCEVCouldNotCompute 246 /// values. 247 bool hasAnyInfo() const { 248 return !isa<SCEVCouldNotCompute>(Exact) || 249 !isa<SCEVCouldNotCompute>(Max); 250 } 251 }; 252 253 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 254 /// this function as they are computed. 255 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 256 257 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 258 /// the PHI instructions that we attempt to compute constant evolutions for. 259 /// This allows us to avoid potentially expensive recomputation of these 260 /// properties. An instruction maps to null if we are unable to compute its 261 /// exit value. 262 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 263 264 /// ValuesAtScopes - This map contains entries for all the expressions 265 /// that we attempt to compute getSCEVAtScope information for, which can 266 /// be expensive in extreme cases. 267 std::map<const SCEV *, 268 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 269 270 /// createSCEV - We know that there is no SCEV for the specified value. 271 /// Analyze the expression. 272 const SCEV *createSCEV(Value *V); 273 274 /// createNodeForPHI - Provide the special handling we need to analyze PHI 275 /// SCEVs. 276 const SCEV *createNodeForPHI(PHINode *PN); 277 278 /// createNodeForGEP - Provide the special handling we need to analyze GEP 279 /// SCEVs. 280 const SCEV *createNodeForGEP(GEPOperator *GEP); 281 282 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 283 /// at most once for each SCEV+Loop pair. 284 /// 285 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 286 287 /// ForgetSymbolicValue - This looks up computed SCEV values for all 288 /// instructions that depend on the given instruction and removes them from 289 /// the ValueExprMap map if they reference SymName. This is used during PHI 290 /// resolution. 291 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 292 293 /// getBECount - Subtract the end and start values and divide by the step, 294 /// rounding up, to get the number of times the backedge is executed. Return 295 /// CouldNotCompute if an intermediate computation overflows. 296 const SCEV *getBECount(const SCEV *Start, 297 const SCEV *End, 298 const SCEV *Step, 299 bool NoWrap); 300 301 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 302 /// loop, lazily computing new values if the loop hasn't been analyzed 303 /// yet. 304 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 305 306 /// ComputeBackedgeTakenCount - Compute the number of times the specified 307 /// loop will iterate. 308 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 309 310 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 311 /// backedge of the specified loop will execute if it exits via the 312 /// specified block. 313 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 314 BasicBlock *ExitingBlock); 315 316 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 317 /// backedge of the specified loop will execute if its exit condition 318 /// were a conditional branch of ExitCond, TBB, and FBB. 319 BackedgeTakenInfo 320 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 321 Value *ExitCond, 322 BasicBlock *TBB, 323 BasicBlock *FBB); 324 325 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 326 /// times the backedge of the specified loop will execute if its exit 327 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 328 /// and FBB. 329 BackedgeTakenInfo 330 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 331 ICmpInst *ExitCond, 332 BasicBlock *TBB, 333 BasicBlock *FBB); 334 335 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 336 /// of 'icmp op load X, cst', try to see if we can compute the 337 /// backedge-taken count. 338 BackedgeTakenInfo 339 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 340 Constant *RHS, 341 const Loop *L, 342 ICmpInst::Predicate p); 343 344 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 345 /// a constant number of times (the condition evolves only from constants), 346 /// try to evaluate a few iterations of the loop until we get the exit 347 /// condition gets a value of ExitWhen (true or false). If we cannot 348 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 349 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 350 Value *Cond, 351 bool ExitWhen); 352 353 /// HowFarToZero - Return the number of times a backedge comparing the 354 /// specified value to zero will execute. If not computable, return 355 /// CouldNotCompute. 356 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 357 358 /// HowFarToNonZero - Return the number of times a backedge checking the 359 /// specified value for nonzero will execute. If not computable, return 360 /// CouldNotCompute. 361 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 362 363 /// HowManyLessThans - Return the number of times a backedge containing the 364 /// specified less-than comparison will execute. If not computable, return 365 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 366 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 367 const Loop *L, bool isSigned); 368 369 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 370 /// (which may not be an immediate predecessor) which has exactly one 371 /// successor from which BB is reachable, or null if no such block is 372 /// found. 373 std::pair<BasicBlock *, BasicBlock *> 374 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 375 376 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 377 /// RHS is true whenever the given FoundCondValue value evaluates to true. 378 bool isImpliedCond(ICmpInst::Predicate Pred, 379 const SCEV *LHS, const SCEV *RHS, 380 Value *FoundCondValue, 381 bool Inverse); 382 383 /// isImpliedCondOperands - Test whether the condition described by Pred, 384 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 385 /// and FoundRHS is true. 386 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 387 const SCEV *LHS, const SCEV *RHS, 388 const SCEV *FoundLHS, const SCEV *FoundRHS); 389 390 /// isImpliedCondOperandsHelper - Test whether the condition described by 391 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 392 /// FoundLHS, and FoundRHS is true. 393 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 394 const SCEV *LHS, const SCEV *RHS, 395 const SCEV *FoundLHS, const SCEV *FoundRHS); 396 397 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 398 /// in the header of its containing loop, we know the loop executes a 399 /// constant number of times, and the PHI node is just a recurrence 400 /// involving constants, fold it. 401 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 402 const Loop *L); 403 404 /// isKnownPredicateWithRanges - Test if the given expression is known to 405 /// satisfy the condition described by Pred and the known constant ranges 406 /// of LHS and RHS. 407 /// 408 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 409 const SCEV *LHS, const SCEV *RHS); 410 411 public: 412 static char ID; // Pass identification, replacement for typeid 413 ScalarEvolution(); 414 415 LLVMContext &getContext() const { return F->getContext(); } 416 417 /// isSCEVable - Test if values of the given type are analyzable within 418 /// the SCEV framework. This primarily includes integer types, and it 419 /// can optionally include pointer types if the ScalarEvolution class 420 /// has access to target-specific information. 421 bool isSCEVable(const Type *Ty) const; 422 423 /// getTypeSizeInBits - Return the size in bits of the specified type, 424 /// for which isSCEVable must return true. 425 uint64_t getTypeSizeInBits(const Type *Ty) const; 426 427 /// getEffectiveSCEVType - Return a type with the same bitwidth as 428 /// the given type and which represents how SCEV will treat the given 429 /// type, for which isSCEVable must return true. For pointer types, 430 /// this is the pointer-sized integer type. 431 const Type *getEffectiveSCEVType(const Type *Ty) const; 432 433 /// getSCEV - Return a SCEV expression for the full generality of the 434 /// specified expression. 435 const SCEV *getSCEV(Value *V); 436 437 const SCEV *getConstant(ConstantInt *V); 438 const SCEV *getConstant(const APInt& Val); 439 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 440 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 441 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 442 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 443 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 444 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 445 bool HasNUW = false, bool HasNSW = false); 446 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 447 bool HasNUW = false, bool HasNSW = false) { 448 SmallVector<const SCEV *, 2> Ops; 449 Ops.push_back(LHS); 450 Ops.push_back(RHS); 451 return getAddExpr(Ops, HasNUW, HasNSW); 452 } 453 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 454 const SCEV *Op2, 455 bool HasNUW = false, bool HasNSW = false) { 456 SmallVector<const SCEV *, 3> Ops; 457 Ops.push_back(Op0); 458 Ops.push_back(Op1); 459 Ops.push_back(Op2); 460 return getAddExpr(Ops, HasNUW, HasNSW); 461 } 462 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 463 bool HasNUW = false, bool HasNSW = false); 464 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 465 bool HasNUW = false, bool HasNSW = false) { 466 SmallVector<const SCEV *, 2> Ops; 467 Ops.push_back(LHS); 468 Ops.push_back(RHS); 469 return getMulExpr(Ops, HasNUW, HasNSW); 470 } 471 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 472 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 473 const Loop *L, 474 bool HasNUW = false, bool HasNSW = false); 475 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 476 const Loop *L, 477 bool HasNUW = false, bool HasNSW = false); 478 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 479 const Loop *L, 480 bool HasNUW = false, bool HasNSW = false) { 481 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 482 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 483 } 484 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 485 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 486 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 487 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 488 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 489 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 490 const SCEV *getUnknown(Value *V); 491 const SCEV *getCouldNotCompute(); 492 493 /// getSizeOfExpr - Return an expression for sizeof on the given type. 494 /// 495 const SCEV *getSizeOfExpr(const Type *AllocTy); 496 497 /// getAlignOfExpr - Return an expression for alignof on the given type. 498 /// 499 const SCEV *getAlignOfExpr(const Type *AllocTy); 500 501 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 502 /// 503 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 504 505 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 506 /// 507 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 508 509 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 510 /// 511 const SCEV *getNegativeSCEV(const SCEV *V); 512 513 /// getNotSCEV - Return the SCEV object corresponding to ~V. 514 /// 515 const SCEV *getNotSCEV(const SCEV *V); 516 517 /// getMinusSCEV - Return LHS-RHS. 518 /// 519 const SCEV *getMinusSCEV(const SCEV *LHS, 520 const SCEV *RHS); 521 522 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 523 /// of the input value to the specified type. If the type must be 524 /// extended, it is zero extended. 525 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 526 527 /// getTruncateOrSignExtend - 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 sign extended. 530 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 531 532 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 533 /// the input value to the specified type. If the type must be extended, 534 /// it is zero extended. The conversion must not be narrowing. 535 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 536 537 /// getNoopOrSignExtend - 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 sign extended. The conversion must not be narrowing. 540 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 541 542 /// getNoopOrAnyExtend - 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 extended with unspecified bits. The conversion must not be 545 /// narrowing. 546 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 547 548 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 549 /// input value to the specified type. The conversion must not be 550 /// widening. 551 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 552 553 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 554 /// the types using zero-extension, and then perform a umax operation 555 /// with them. 556 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 557 const SCEV *RHS); 558 559 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 560 /// the types using zero-extension, and then perform a umin operation 561 /// with them. 562 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 563 const SCEV *RHS); 564 565 /// getSCEVAtScope - Return a SCEV expression for the specified value 566 /// at the specified scope in the program. The L value specifies a loop 567 /// nest to evaluate the expression at, where null is the top-level or a 568 /// specified loop is immediately inside of the loop. 569 /// 570 /// This method can be used to compute the exit value for a variable defined 571 /// in a loop by querying what the value will hold in the parent loop. 572 /// 573 /// In the case that a relevant loop exit value cannot be computed, the 574 /// original value V is returned. 575 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 576 577 /// getSCEVAtScope - This is a convenience function which does 578 /// getSCEVAtScope(getSCEV(V), L). 579 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 580 581 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 582 /// by a conditional between LHS and RHS. This is used to help avoid max 583 /// expressions in loop trip counts, and to eliminate casts. 584 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 585 const SCEV *LHS, const SCEV *RHS); 586 587 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 588 /// protected by a conditional between LHS and RHS. This is used to 589 /// to eliminate casts. 590 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 591 const SCEV *LHS, const SCEV *RHS); 592 593 /// getBackedgeTakenCount - If the specified loop has a predictable 594 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 595 /// object. The backedge-taken count is the number of times the loop header 596 /// will be branched to from within the loop. This is one less than the 597 /// trip count of the loop, since it doesn't count the first iteration, 598 /// when the header is branched to from outside the loop. 599 /// 600 /// Note that it is not valid to call this method on a loop without a 601 /// loop-invariant backedge-taken count (see 602 /// hasLoopInvariantBackedgeTakenCount). 603 /// 604 const SCEV *getBackedgeTakenCount(const Loop *L); 605 606 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 607 /// return the least SCEV value that is known never to be less than the 608 /// actual backedge taken count. 609 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 610 611 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 612 /// has an analyzable loop-invariant backedge-taken count. 613 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 614 615 /// forgetLoop - This method should be called by the client when it has 616 /// changed a loop in a way that may effect ScalarEvolution's ability to 617 /// compute a trip count, or if the loop is deleted. 618 void forgetLoop(const Loop *L); 619 620 /// forgetValue - This method should be called by the client when it has 621 /// changed a value in a way that may effect its value, or which may 622 /// disconnect it from a def-use chain linking it to a loop. 623 void forgetValue(Value *V); 624 625 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 626 /// is guaranteed to end in (at every loop iteration). It is, at the same 627 /// time, the minimum number of times S is divisible by 2. For example, 628 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 629 /// bitwidth of S. 630 uint32_t GetMinTrailingZeros(const SCEV *S); 631 632 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 633 /// 634 ConstantRange getUnsignedRange(const SCEV *S); 635 636 /// getSignedRange - Determine the signed range for a particular SCEV. 637 /// 638 ConstantRange getSignedRange(const SCEV *S); 639 640 /// isKnownNegative - Test if the given expression is known to be negative. 641 /// 642 bool isKnownNegative(const SCEV *S); 643 644 /// isKnownPositive - Test if the given expression is known to be positive. 645 /// 646 bool isKnownPositive(const SCEV *S); 647 648 /// isKnownNonNegative - Test if the given expression is known to be 649 /// non-negative. 650 /// 651 bool isKnownNonNegative(const SCEV *S); 652 653 /// isKnownNonPositive - Test if the given expression is known to be 654 /// non-positive. 655 /// 656 bool isKnownNonPositive(const SCEV *S); 657 658 /// isKnownNonZero - Test if the given expression is known to be 659 /// non-zero. 660 /// 661 bool isKnownNonZero(const SCEV *S); 662 663 /// isKnownPredicate - Test if the given expression is known to satisfy 664 /// the condition described by Pred, LHS, and RHS. 665 /// 666 bool isKnownPredicate(ICmpInst::Predicate Pred, 667 const SCEV *LHS, const SCEV *RHS); 668 669 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 670 /// predicate Pred. Return true iff any changes were made. If the 671 /// operands are provably equal or inequal, LHS and RHS are set to 672 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 673 /// 674 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 675 const SCEV *&LHS, 676 const SCEV *&RHS); 677 678 virtual bool runOnFunction(Function &F); 679 virtual void releaseMemory(); 680 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 681 virtual void print(raw_ostream &OS, const Module* = 0) const; 682 683 private: 684 FoldingSet<SCEV> UniqueSCEVs; 685 BumpPtrAllocator SCEVAllocator; 686 687 /// FirstUnknown - The head of a linked list of all SCEVUnknown 688 /// values that have been allocated. This is used by releaseMemory 689 /// to locate them all and call their destructors. 690 SCEVUnknown *FirstUnknown; 691 }; 692} 693 694#endif 695