ScalarEvolution.h revision 6678e7b6eb534b43b92105076e6d0553e5cf7def
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 /// UnsignedRanges - Memoized results from getUnsignedRange 271 DenseMap<const SCEV *, ConstantRange> UnsignedRanges; 272 273 /// SignedRanges - Memoized results from getSignedRange 274 DenseMap<const SCEV *, ConstantRange> SignedRanges; 275 276 /// createSCEV - We know that there is no SCEV for the specified value. 277 /// Analyze the expression. 278 const SCEV *createSCEV(Value *V); 279 280 /// createNodeForPHI - Provide the special handling we need to analyze PHI 281 /// SCEVs. 282 const SCEV *createNodeForPHI(PHINode *PN); 283 284 /// createNodeForGEP - Provide the special handling we need to analyze GEP 285 /// SCEVs. 286 const SCEV *createNodeForGEP(GEPOperator *GEP); 287 288 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 289 /// at most once for each SCEV+Loop pair. 290 /// 291 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 292 293 /// ForgetSymbolicValue - This looks up computed SCEV values for all 294 /// instructions that depend on the given instruction and removes them from 295 /// the ValueExprMap map if they reference SymName. This is used during PHI 296 /// resolution. 297 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 298 299 /// getBECount - Subtract the end and start values and divide by the step, 300 /// rounding up, to get the number of times the backedge is executed. Return 301 /// CouldNotCompute if an intermediate computation overflows. 302 const SCEV *getBECount(const SCEV *Start, 303 const SCEV *End, 304 const SCEV *Step, 305 bool NoWrap); 306 307 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 308 /// loop, lazily computing new values if the loop hasn't been analyzed 309 /// yet. 310 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 311 312 /// ComputeBackedgeTakenCount - Compute the number of times the specified 313 /// loop will iterate. 314 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 315 316 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 317 /// backedge of the specified loop will execute if it exits via the 318 /// specified block. 319 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 320 BasicBlock *ExitingBlock); 321 322 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 323 /// backedge of the specified loop will execute if its exit condition 324 /// were a conditional branch of ExitCond, TBB, and FBB. 325 BackedgeTakenInfo 326 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 327 Value *ExitCond, 328 BasicBlock *TBB, 329 BasicBlock *FBB); 330 331 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 332 /// times the backedge of the specified loop will execute if its exit 333 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 334 /// and FBB. 335 BackedgeTakenInfo 336 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 337 ICmpInst *ExitCond, 338 BasicBlock *TBB, 339 BasicBlock *FBB); 340 341 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 342 /// of 'icmp op load X, cst', try to see if we can compute the 343 /// backedge-taken count. 344 BackedgeTakenInfo 345 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 346 Constant *RHS, 347 const Loop *L, 348 ICmpInst::Predicate p); 349 350 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 351 /// a constant number of times (the condition evolves only from constants), 352 /// try to evaluate a few iterations of the loop until we get the exit 353 /// condition gets a value of ExitWhen (true or false). If we cannot 354 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 355 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 356 Value *Cond, 357 bool ExitWhen); 358 359 /// HowFarToZero - Return the number of times a backedge comparing the 360 /// specified value to zero will execute. If not computable, return 361 /// CouldNotCompute. 362 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 363 364 /// HowFarToNonZero - Return the number of times a backedge checking the 365 /// specified value for nonzero will execute. If not computable, return 366 /// CouldNotCompute. 367 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 368 369 /// HowManyLessThans - Return the number of times a backedge containing the 370 /// specified less-than comparison will execute. If not computable, return 371 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 372 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 373 const Loop *L, bool isSigned); 374 375 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 376 /// (which may not be an immediate predecessor) which has exactly one 377 /// successor from which BB is reachable, or null if no such block is 378 /// found. 379 std::pair<BasicBlock *, BasicBlock *> 380 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 381 382 /// isImpliedCond - Test whether the condition described by Pred, LHS, and 383 /// RHS is true whenever the given FoundCondValue value evaluates to true. 384 bool isImpliedCond(ICmpInst::Predicate Pred, 385 const SCEV *LHS, const SCEV *RHS, 386 Value *FoundCondValue, 387 bool Inverse); 388 389 /// isImpliedCondOperands - Test whether the condition described by Pred, 390 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 391 /// and FoundRHS is true. 392 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 393 const SCEV *LHS, const SCEV *RHS, 394 const SCEV *FoundLHS, const SCEV *FoundRHS); 395 396 /// isImpliedCondOperandsHelper - Test whether the condition described by 397 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 398 /// FoundLHS, and FoundRHS is true. 399 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 400 const SCEV *LHS, const SCEV *RHS, 401 const SCEV *FoundLHS, const SCEV *FoundRHS); 402 403 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 404 /// in the header of its containing loop, we know the loop executes a 405 /// constant number of times, and the PHI node is just a recurrence 406 /// involving constants, fold it. 407 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 408 const Loop *L); 409 410 /// isKnownPredicateWithRanges - Test if the given expression is known to 411 /// satisfy the condition described by Pred and the known constant ranges 412 /// of LHS and RHS. 413 /// 414 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 415 const SCEV *LHS, const SCEV *RHS); 416 417 public: 418 static char ID; // Pass identification, replacement for typeid 419 ScalarEvolution(); 420 421 LLVMContext &getContext() const { return F->getContext(); } 422 423 /// isSCEVable - Test if values of the given type are analyzable within 424 /// the SCEV framework. This primarily includes integer types, and it 425 /// can optionally include pointer types if the ScalarEvolution class 426 /// has access to target-specific information. 427 bool isSCEVable(const Type *Ty) const; 428 429 /// getTypeSizeInBits - Return the size in bits of the specified type, 430 /// for which isSCEVable must return true. 431 uint64_t getTypeSizeInBits(const Type *Ty) const; 432 433 /// getEffectiveSCEVType - Return a type with the same bitwidth as 434 /// the given type and which represents how SCEV will treat the given 435 /// type, for which isSCEVable must return true. For pointer types, 436 /// this is the pointer-sized integer type. 437 const Type *getEffectiveSCEVType(const Type *Ty) const; 438 439 /// getSCEV - Return a SCEV expression for the full generality of the 440 /// specified expression. 441 const SCEV *getSCEV(Value *V); 442 443 const SCEV *getConstant(ConstantInt *V); 444 const SCEV *getConstant(const APInt& Val); 445 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 446 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 447 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 448 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 449 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 450 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 451 bool HasNUW = false, bool HasNSW = false); 452 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 453 bool HasNUW = false, bool HasNSW = false) { 454 SmallVector<const SCEV *, 2> Ops; 455 Ops.push_back(LHS); 456 Ops.push_back(RHS); 457 return getAddExpr(Ops, HasNUW, HasNSW); 458 } 459 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 460 const SCEV *Op2, 461 bool HasNUW = false, bool HasNSW = false) { 462 SmallVector<const SCEV *, 3> Ops; 463 Ops.push_back(Op0); 464 Ops.push_back(Op1); 465 Ops.push_back(Op2); 466 return getAddExpr(Ops, HasNUW, HasNSW); 467 } 468 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 469 bool HasNUW = false, bool HasNSW = false); 470 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 471 bool HasNUW = false, bool HasNSW = false) { 472 SmallVector<const SCEV *, 2> Ops; 473 Ops.push_back(LHS); 474 Ops.push_back(RHS); 475 return getMulExpr(Ops, HasNUW, HasNSW); 476 } 477 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 478 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 479 const Loop *L, 480 bool HasNUW = false, bool HasNSW = false); 481 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 482 const Loop *L, 483 bool HasNUW = false, bool HasNSW = false); 484 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 485 const Loop *L, 486 bool HasNUW = false, bool HasNSW = false) { 487 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 488 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 489 } 490 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 491 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 492 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 493 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 494 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 495 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 496 const SCEV *getUnknown(Value *V); 497 const SCEV *getCouldNotCompute(); 498 499 /// getSizeOfExpr - Return an expression for sizeof on the given type. 500 /// 501 const SCEV *getSizeOfExpr(const Type *AllocTy); 502 503 /// getAlignOfExpr - Return an expression for alignof on the given type. 504 /// 505 const SCEV *getAlignOfExpr(const Type *AllocTy); 506 507 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 508 /// 509 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 510 511 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 512 /// 513 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 514 515 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 516 /// 517 const SCEV *getNegativeSCEV(const SCEV *V); 518 519 /// getNotSCEV - Return the SCEV object corresponding to ~V. 520 /// 521 const SCEV *getNotSCEV(const SCEV *V); 522 523 /// getMinusSCEV - Return LHS-RHS. 524 /// 525 const SCEV *getMinusSCEV(const SCEV *LHS, 526 const SCEV *RHS); 527 528 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 529 /// of the input value to the specified type. If the type must be 530 /// extended, it is zero extended. 531 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 532 533 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 534 /// of the input value to the specified type. If the type must be 535 /// extended, it is sign extended. 536 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 537 538 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 539 /// the input value to the specified type. If the type must be extended, 540 /// it is zero extended. The conversion must not be narrowing. 541 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 542 543 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 544 /// the input value to the specified type. If the type must be extended, 545 /// it is sign extended. The conversion must not be narrowing. 546 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 547 548 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 549 /// the input value to the specified type. If the type must be extended, 550 /// it is extended with unspecified bits. The conversion must not be 551 /// narrowing. 552 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 553 554 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 555 /// input value to the specified type. The conversion must not be 556 /// widening. 557 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 558 559 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 560 /// the types using zero-extension, and then perform a umax operation 561 /// with them. 562 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 563 const SCEV *RHS); 564 565 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 566 /// the types using zero-extension, and then perform a umin operation 567 /// with them. 568 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 569 const SCEV *RHS); 570 571 /// getSCEVAtScope - Return a SCEV expression for the specified value 572 /// at the specified scope in the program. The L value specifies a loop 573 /// nest to evaluate the expression at, where null is the top-level or a 574 /// specified loop is immediately inside of the loop. 575 /// 576 /// This method can be used to compute the exit value for a variable defined 577 /// in a loop by querying what the value will hold in the parent loop. 578 /// 579 /// In the case that a relevant loop exit value cannot be computed, the 580 /// original value V is returned. 581 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 582 583 /// getSCEVAtScope - This is a convenience function which does 584 /// getSCEVAtScope(getSCEV(V), L). 585 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 586 587 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 588 /// by a conditional between LHS and RHS. This is used to help avoid max 589 /// expressions in loop trip counts, and to eliminate casts. 590 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 591 const SCEV *LHS, const SCEV *RHS); 592 593 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 594 /// protected by a conditional between LHS and RHS. This is used to 595 /// to eliminate casts. 596 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 597 const SCEV *LHS, const SCEV *RHS); 598 599 /// getBackedgeTakenCount - If the specified loop has a predictable 600 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 601 /// object. The backedge-taken count is the number of times the loop header 602 /// will be branched to from within the loop. This is one less than the 603 /// trip count of the loop, since it doesn't count the first iteration, 604 /// when the header is branched to from outside the loop. 605 /// 606 /// Note that it is not valid to call this method on a loop without a 607 /// loop-invariant backedge-taken count (see 608 /// hasLoopInvariantBackedgeTakenCount). 609 /// 610 const SCEV *getBackedgeTakenCount(const Loop *L); 611 612 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 613 /// return the least SCEV value that is known never to be less than the 614 /// actual backedge taken count. 615 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 616 617 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 618 /// has an analyzable loop-invariant backedge-taken count. 619 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 620 621 /// forgetLoop - This method should be called by the client when it has 622 /// changed a loop in a way that may effect ScalarEvolution's ability to 623 /// compute a trip count, or if the loop is deleted. 624 void forgetLoop(const Loop *L); 625 626 /// forgetValue - This method should be called by the client when it has 627 /// changed a value in a way that may effect its value, or which may 628 /// disconnect it from a def-use chain linking it to a loop. 629 void forgetValue(Value *V); 630 631 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 632 /// is guaranteed to end in (at every loop iteration). It is, at the same 633 /// time, the minimum number of times S is divisible by 2. For example, 634 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 635 /// bitwidth of S. 636 uint32_t GetMinTrailingZeros(const SCEV *S); 637 638 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 639 /// 640 ConstantRange getUnsignedRange(const SCEV *S); 641 642 /// getSignedRange - Determine the signed range for a particular SCEV. 643 /// 644 ConstantRange getSignedRange(const SCEV *S); 645 646 /// isKnownNegative - Test if the given expression is known to be negative. 647 /// 648 bool isKnownNegative(const SCEV *S); 649 650 /// isKnownPositive - Test if the given expression is known to be positive. 651 /// 652 bool isKnownPositive(const SCEV *S); 653 654 /// isKnownNonNegative - Test if the given expression is known to be 655 /// non-negative. 656 /// 657 bool isKnownNonNegative(const SCEV *S); 658 659 /// isKnownNonPositive - Test if the given expression is known to be 660 /// non-positive. 661 /// 662 bool isKnownNonPositive(const SCEV *S); 663 664 /// isKnownNonZero - Test if the given expression is known to be 665 /// non-zero. 666 /// 667 bool isKnownNonZero(const SCEV *S); 668 669 /// isKnownPredicate - Test if the given expression is known to satisfy 670 /// the condition described by Pred, LHS, and RHS. 671 /// 672 bool isKnownPredicate(ICmpInst::Predicate Pred, 673 const SCEV *LHS, const SCEV *RHS); 674 675 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 676 /// predicate Pred. Return true iff any changes were made. If the 677 /// operands are provably equal or inequal, LHS and RHS are set to 678 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 679 /// 680 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 681 const SCEV *&LHS, 682 const SCEV *&RHS); 683 684 virtual bool runOnFunction(Function &F); 685 virtual void releaseMemory(); 686 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 687 virtual void print(raw_ostream &OS, const Module* = 0) const; 688 689 private: 690 FoldingSet<SCEV> UniqueSCEVs; 691 BumpPtrAllocator SCEVAllocator; 692 693 /// FirstUnknown - The head of a linked list of all SCEVUnknown 694 /// values that have been allocated. This is used by releaseMemory 695 /// to locate them all and call their destructors. 696 SCEVUnknown *FirstUnknown; 697 }; 698} 699 700#endif 701