ScalarEvolution.h revision 53c66eacc417c0113fba7159487b90005dc8f91e
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 48 /// SCEV - This class represents an analyzed expression in the program. These 49 /// are opaque objects that the client is not allowed to do much with 50 /// directly. 51 /// 52 class SCEV : public FoldingSetNode { 53 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 54 /// The ScalarEvolution's BumpPtrAllocator holds the data. 55 FoldingSetNodeIDRef FastID; 56 57 // The SCEV baseclass this node corresponds to 58 const unsigned short SCEVType; 59 60 protected: 61 /// SubclassData - This field is initialized to zero and may be used in 62 /// subclasses to store miscellaneous information. 63 unsigned short SubclassData; 64 65 private: 66 SCEV(const SCEV &); // DO NOT IMPLEMENT 67 void operator=(const SCEV &); // DO NOT IMPLEMENT 68 protected: 69 virtual ~SCEV(); 70 public: 71 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 72 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 73 74 unsigned getSCEVType() const { return SCEVType; } 75 76 /// Profile - FoldingSet support. 77 void Profile(FoldingSetNodeID& ID) { ID = FastID; } 78 79 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 80 /// the specified loop. 81 virtual bool isLoopInvariant(const Loop *L) const = 0; 82 83 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 84 /// known way in the specified loop. This property being true implies that 85 /// the value is variant in the loop AND that we can emit an expression to 86 /// compute the value of the expression at any particular loop iteration. 87 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 88 89 /// getType - Return the LLVM type of this SCEV expression. 90 /// 91 virtual const Type *getType() const = 0; 92 93 /// isZero - Return true if the expression is a constant zero. 94 /// 95 bool isZero() const; 96 97 /// isOne - Return true if the expression is a constant one. 98 /// 99 bool isOne() const; 100 101 /// isAllOnesValue - Return true if the expression is a constant 102 /// all-ones value. 103 /// 104 bool isAllOnesValue() const; 105 106 /// hasOperand - Test whether this SCEV has Op as a direct or 107 /// indirect operand. 108 virtual bool hasOperand(const SCEV *Op) const = 0; 109 110 /// dominates - Return true if elements that makes up this SCEV dominates 111 /// the specified basic block. 112 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 113 114 /// properlyDominates - Return true if elements that makes up this SCEV 115 /// properly dominate the specified basic block. 116 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 117 118 /// print - Print out the internal representation of this scalar to the 119 /// specified stream. This should really only be used for debugging 120 /// purposes. 121 virtual void print(raw_ostream &OS) const = 0; 122 123 /// dump - This method is used for debugging. 124 /// 125 void dump() const; 126 }; 127 128 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 129 S.print(OS); 130 return OS; 131 } 132 133 /// SCEVCouldNotCompute - An object of this class is returned by queries that 134 /// could not be answered. For example, if you ask for the number of 135 /// iterations of a linked-list traversal loop, you will get one of these. 136 /// None of the standard SCEV operations are valid on this class, it is just a 137 /// marker. 138 struct SCEVCouldNotCompute : public SCEV { 139 SCEVCouldNotCompute(); 140 141 // None of these methods are valid for this object. 142 virtual bool isLoopInvariant(const Loop *L) const; 143 virtual const Type *getType() const; 144 virtual bool hasComputableLoopEvolution(const Loop *L) const; 145 virtual void print(raw_ostream &OS) const; 146 virtual bool hasOperand(const SCEV *Op) const; 147 148 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 149 return true; 150 } 151 152 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 153 return true; 154 } 155 156 /// Methods for support type inquiry through isa, cast, and dyn_cast: 157 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 158 static bool classof(const SCEV *S); 159 }; 160 161 /// ScalarEvolution - This class is the main scalar evolution driver. Because 162 /// client code (intentionally) can't do much with the SCEV objects directly, 163 /// they must ask this class for services. 164 /// 165 class ScalarEvolution : public FunctionPass { 166 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 167 /// notified whenever a Value is deleted. 168 class SCEVCallbackVH : public CallbackVH { 169 ScalarEvolution *SE; 170 virtual void deleted(); 171 virtual void allUsesReplacedWith(Value *New); 172 public: 173 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 174 }; 175 176 friend class SCEVCallbackVH; 177 friend class SCEVExpander; 178 179 /// F - The function we are analyzing. 180 /// 181 Function *F; 182 183 /// LI - The loop information for the function we are currently analyzing. 184 /// 185 LoopInfo *LI; 186 187 /// TD - The target data information for the target we are targeting. 188 /// 189 TargetData *TD; 190 191 /// DT - The dominator tree. 192 /// 193 DominatorTree *DT; 194 195 /// CouldNotCompute - This SCEV is used to represent unknown trip 196 /// counts and things. 197 SCEVCouldNotCompute CouldNotCompute; 198 199 /// Scalars - This is a cache of the scalars we have analyzed so far. 200 /// 201 std::map<SCEVCallbackVH, const SCEV *> Scalars; 202 203 /// BackedgeTakenInfo - Information about the backedge-taken count 204 /// of a loop. This currently includes an exact count and a maximum count. 205 /// 206 struct BackedgeTakenInfo { 207 /// Exact - An expression indicating the exact backedge-taken count of 208 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 209 const SCEV *Exact; 210 211 /// Max - An expression indicating the least maximum backedge-taken 212 /// count of the loop that is known, or a SCEVCouldNotCompute. 213 const SCEV *Max; 214 215 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 216 Exact(exact), Max(exact) {} 217 218 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 219 Exact(exact), Max(max) {} 220 221 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 222 /// computed information, or whether it's all SCEVCouldNotCompute 223 /// values. 224 bool hasAnyInfo() const { 225 return !isa<SCEVCouldNotCompute>(Exact) || 226 !isa<SCEVCouldNotCompute>(Max); 227 } 228 }; 229 230 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 231 /// this function as they are computed. 232 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 233 234 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 235 /// the PHI instructions that we attempt to compute constant evolutions for. 236 /// This allows us to avoid potentially expensive recomputation of these 237 /// properties. An instruction maps to null if we are unable to compute its 238 /// exit value. 239 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 240 241 /// ValuesAtScopes - This map contains entries for all the expressions 242 /// that we attempt to compute getSCEVAtScope information for, which can 243 /// be expensive in extreme cases. 244 std::map<const SCEV *, 245 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 246 247 /// createSCEV - We know that there is no SCEV for the specified value. 248 /// Analyze the expression. 249 const SCEV *createSCEV(Value *V); 250 251 /// createNodeForPHI - Provide the special handling we need to analyze PHI 252 /// SCEVs. 253 const SCEV *createNodeForPHI(PHINode *PN); 254 255 /// createNodeForGEP - Provide the special handling we need to analyze GEP 256 /// SCEVs. 257 const SCEV *createNodeForGEP(GEPOperator *GEP); 258 259 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 260 /// at most once for each SCEV+Loop pair. 261 /// 262 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 263 264 /// ForgetSymbolicValue - This looks up computed SCEV values for all 265 /// instructions that depend on the given instruction and removes them from 266 /// the Scalars map if they reference SymName. This is used during PHI 267 /// resolution. 268 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 269 270 /// getBECount - Subtract the end and start values and divide by the step, 271 /// rounding up, to get the number of times the backedge is executed. Return 272 /// CouldNotCompute if an intermediate computation overflows. 273 const SCEV *getBECount(const SCEV *Start, 274 const SCEV *End, 275 const SCEV *Step, 276 bool NoWrap); 277 278 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 279 /// loop, lazily computing new values if the loop hasn't been analyzed 280 /// yet. 281 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 282 283 /// ComputeBackedgeTakenCount - Compute the number of times the specified 284 /// loop will iterate. 285 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 286 287 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 288 /// backedge of the specified loop will execute if it exits via the 289 /// specified block. 290 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 291 BasicBlock *ExitingBlock); 292 293 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 294 /// backedge of the specified loop will execute if its exit condition 295 /// were a conditional branch of ExitCond, TBB, and FBB. 296 BackedgeTakenInfo 297 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 298 Value *ExitCond, 299 BasicBlock *TBB, 300 BasicBlock *FBB); 301 302 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 303 /// times the backedge of the specified loop will execute if its exit 304 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 305 /// and FBB. 306 BackedgeTakenInfo 307 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 308 ICmpInst *ExitCond, 309 BasicBlock *TBB, 310 BasicBlock *FBB); 311 312 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 313 /// of 'icmp op load X, cst', try to see if we can compute the 314 /// backedge-taken count. 315 BackedgeTakenInfo 316 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 317 Constant *RHS, 318 const Loop *L, 319 ICmpInst::Predicate p); 320 321 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 322 /// a constant number of times (the condition evolves only from constants), 323 /// try to evaluate a few iterations of the loop until we get the exit 324 /// condition gets a value of ExitWhen (true or false). If we cannot 325 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 326 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 327 Value *Cond, 328 bool ExitWhen); 329 330 /// HowFarToZero - Return the number of times a backedge comparing the 331 /// specified value to zero will execute. If not computable, return 332 /// CouldNotCompute. 333 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 334 335 /// HowFarToNonZero - Return the number of times a backedge checking the 336 /// specified value for nonzero will execute. If not computable, return 337 /// CouldNotCompute. 338 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 339 340 /// HowManyLessThans - Return the number of times a backedge containing the 341 /// specified less-than comparison will execute. If not computable, return 342 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 343 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 344 const Loop *L, bool isSigned); 345 346 /// getLoopPredecessor - If the given loop's header has exactly one unique 347 /// predecessor outside the loop, return it. Otherwise return null. 348 BasicBlock *getLoopPredecessor(const Loop *L); 349 350 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 351 /// (which may not be an immediate predecessor) which has exactly one 352 /// successor from which BB is reachable, or null if no such block is 353 /// found. 354 BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 355 356 /// isImpliedCond - Test whether the condition described by Pred, LHS, 357 /// and RHS is true whenever the given Cond value evaluates to true. 358 bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred, 359 const SCEV *LHS, const SCEV *RHS, 360 bool Inverse); 361 362 /// isImpliedCondOperands - Test whether the condition described by Pred, 363 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 364 /// and FoundRHS is true. 365 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 366 const SCEV *LHS, const SCEV *RHS, 367 const SCEV *FoundLHS, const SCEV *FoundRHS); 368 369 /// isImpliedCondOperandsHelper - Test whether the condition described by 370 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 371 /// FoundLHS, and FoundRHS is true. 372 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 373 const SCEV *LHS, const SCEV *RHS, 374 const SCEV *FoundLHS, const SCEV *FoundRHS); 375 376 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 377 /// in the header of its containing loop, we know the loop executes a 378 /// constant number of times, and the PHI node is just a recurrence 379 /// involving constants, fold it. 380 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 381 const Loop *L); 382 383 /// isKnownPredicateWithRanges - Test if the given expression is known to 384 /// satisfy the condition described by Pred and the known constant ranges 385 /// of LHS and RHS. 386 /// 387 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 388 const SCEV *LHS, const SCEV *RHS); 389 390 public: 391 static char ID; // Pass identification, replacement for typeid 392 ScalarEvolution(); 393 394 LLVMContext &getContext() const { return F->getContext(); } 395 396 /// isSCEVable - Test if values of the given type are analyzable within 397 /// the SCEV framework. This primarily includes integer types, and it 398 /// can optionally include pointer types if the ScalarEvolution class 399 /// has access to target-specific information. 400 bool isSCEVable(const Type *Ty) const; 401 402 /// getTypeSizeInBits - Return the size in bits of the specified type, 403 /// for which isSCEVable must return true. 404 uint64_t getTypeSizeInBits(const Type *Ty) const; 405 406 /// getEffectiveSCEVType - Return a type with the same bitwidth as 407 /// the given type and which represents how SCEV will treat the given 408 /// type, for which isSCEVable must return true. For pointer types, 409 /// this is the pointer-sized integer type. 410 const Type *getEffectiveSCEVType(const Type *Ty) const; 411 412 /// getSCEV - Return a SCEV expression for the full generality of the 413 /// specified expression. 414 const SCEV *getSCEV(Value *V); 415 416 const SCEV *getConstant(ConstantInt *V); 417 const SCEV *getConstant(const APInt& Val); 418 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 419 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 420 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 421 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 422 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 423 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 424 bool HasNUW = false, bool HasNSW = false); 425 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 426 bool HasNUW = false, bool HasNSW = false) { 427 SmallVector<const SCEV *, 2> Ops; 428 Ops.push_back(LHS); 429 Ops.push_back(RHS); 430 return getAddExpr(Ops, HasNUW, HasNSW); 431 } 432 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 433 const SCEV *Op2, 434 bool HasNUW = false, bool HasNSW = false) { 435 SmallVector<const SCEV *, 3> Ops; 436 Ops.push_back(Op0); 437 Ops.push_back(Op1); 438 Ops.push_back(Op2); 439 return getAddExpr(Ops, HasNUW, HasNSW); 440 } 441 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 442 bool HasNUW = false, bool HasNSW = false); 443 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 444 bool HasNUW = false, bool HasNSW = false) { 445 SmallVector<const SCEV *, 2> Ops; 446 Ops.push_back(LHS); 447 Ops.push_back(RHS); 448 return getMulExpr(Ops, HasNUW, HasNSW); 449 } 450 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 451 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 452 const Loop *L, 453 bool HasNUW = false, bool HasNSW = false); 454 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 455 const Loop *L, 456 bool HasNUW = false, bool HasNSW = false); 457 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 458 const Loop *L, 459 bool HasNUW = false, bool HasNSW = false) { 460 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 461 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 462 } 463 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 464 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 465 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 466 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 467 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 468 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 469 const SCEV *getUnknown(Value *V); 470 const SCEV *getCouldNotCompute(); 471 472 /// getSizeOfExpr - Return an expression for sizeof on the given type. 473 /// 474 const SCEV *getSizeOfExpr(const Type *AllocTy); 475 476 /// getAlignOfExpr - Return an expression for alignof on the given type. 477 /// 478 const SCEV *getAlignOfExpr(const Type *AllocTy); 479 480 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 481 /// 482 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 483 484 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 485 /// 486 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 487 488 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 489 /// 490 const SCEV *getNegativeSCEV(const SCEV *V); 491 492 /// getNotSCEV - Return the SCEV object corresponding to ~V. 493 /// 494 const SCEV *getNotSCEV(const SCEV *V); 495 496 /// getMinusSCEV - Return LHS-RHS. 497 /// 498 const SCEV *getMinusSCEV(const SCEV *LHS, 499 const SCEV *RHS); 500 501 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 502 /// of the input value to the specified type. If the type must be 503 /// extended, it is zero extended. 504 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 505 506 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 507 /// of the input value to the specified type. If the type must be 508 /// extended, it is sign extended. 509 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 510 511 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 512 /// the input value to the specified type. If the type must be extended, 513 /// it is zero extended. The conversion must not be narrowing. 514 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 515 516 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 517 /// the input value to the specified type. If the type must be extended, 518 /// it is sign extended. The conversion must not be narrowing. 519 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 520 521 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 522 /// the input value to the specified type. If the type must be extended, 523 /// it is extended with unspecified bits. The conversion must not be 524 /// narrowing. 525 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 526 527 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 528 /// input value to the specified type. The conversion must not be 529 /// widening. 530 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 531 532 /// getIntegerSCEV - Given a SCEVable type, create a constant for the 533 /// specified signed integer value and return a SCEV for the constant. 534 const SCEV *getIntegerSCEV(int64_t Val, const Type *Ty); 535 536 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 537 /// the types using zero-extension, and then perform a umax operation 538 /// with them. 539 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 540 const SCEV *RHS); 541 542 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 543 /// the types using zero-extension, and then perform a umin operation 544 /// with them. 545 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 546 const SCEV *RHS); 547 548 /// getSCEVAtScope - Return a SCEV expression for the specified value 549 /// at the specified scope in the program. The L value specifies a loop 550 /// nest to evaluate the expression at, where null is the top-level or a 551 /// specified loop is immediately inside of the loop. 552 /// 553 /// This method can be used to compute the exit value for a variable defined 554 /// in a loop by querying what the value will hold in the parent loop. 555 /// 556 /// In the case that a relevant loop exit value cannot be computed, the 557 /// original value V is returned. 558 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 559 560 /// getSCEVAtScope - This is a convenience function which does 561 /// getSCEVAtScope(getSCEV(V), L). 562 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 563 564 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 565 /// by a conditional between LHS and RHS. This is used to help avoid max 566 /// expressions in loop trip counts, and to eliminate casts. 567 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 568 const SCEV *LHS, const SCEV *RHS); 569 570 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 571 /// protected by a conditional between LHS and RHS. This is used to 572 /// to eliminate casts. 573 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 574 const SCEV *LHS, const SCEV *RHS); 575 576 /// getBackedgeTakenCount - If the specified loop has a predictable 577 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 578 /// object. The backedge-taken count is the number of times the loop header 579 /// will be branched to from within the loop. This is one less than the 580 /// trip count of the loop, since it doesn't count the first iteration, 581 /// when the header is branched to from outside the loop. 582 /// 583 /// Note that it is not valid to call this method on a loop without a 584 /// loop-invariant backedge-taken count (see 585 /// hasLoopInvariantBackedgeTakenCount). 586 /// 587 const SCEV *getBackedgeTakenCount(const Loop *L); 588 589 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 590 /// return the least SCEV value that is known never to be less than the 591 /// actual backedge taken count. 592 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 593 594 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 595 /// has an analyzable loop-invariant backedge-taken count. 596 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 597 598 /// forgetLoop - This method should be called by the client when it has 599 /// changed a loop in a way that may effect ScalarEvolution's ability to 600 /// compute a trip count, or if the loop is deleted. 601 void forgetLoop(const Loop *L); 602 603 /// forgetValue - This method should be called by the client when it has 604 /// changed a value in a way that may effect its value, or which may 605 /// disconnect it from a def-use chain linking it to a loop. 606 void forgetValue(Value *V); 607 608 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 609 /// is guaranteed to end in (at every loop iteration). It is, at the same 610 /// time, the minimum number of times S is divisible by 2. For example, 611 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 612 /// bitwidth of S. 613 uint32_t GetMinTrailingZeros(const SCEV *S); 614 615 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 616 /// 617 ConstantRange getUnsignedRange(const SCEV *S); 618 619 /// getSignedRange - Determine the signed range for a particular SCEV. 620 /// 621 ConstantRange getSignedRange(const SCEV *S); 622 623 /// isKnownNegative - Test if the given expression is known to be negative. 624 /// 625 bool isKnownNegative(const SCEV *S); 626 627 /// isKnownPositive - Test if the given expression is known to be positive. 628 /// 629 bool isKnownPositive(const SCEV *S); 630 631 /// isKnownNonNegative - Test if the given expression is known to be 632 /// non-negative. 633 /// 634 bool isKnownNonNegative(const SCEV *S); 635 636 /// isKnownNonPositive - Test if the given expression is known to be 637 /// non-positive. 638 /// 639 bool isKnownNonPositive(const SCEV *S); 640 641 /// isKnownNonZero - Test if the given expression is known to be 642 /// non-zero. 643 /// 644 bool isKnownNonZero(const SCEV *S); 645 646 /// isKnownPredicate - Test if the given expression is known to satisfy 647 /// the condition described by Pred, LHS, and RHS. 648 /// 649 bool isKnownPredicate(ICmpInst::Predicate Pred, 650 const SCEV *LHS, const SCEV *RHS); 651 652 virtual bool runOnFunction(Function &F); 653 virtual void releaseMemory(); 654 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 655 virtual void print(raw_ostream &OS, const Module* = 0) const; 656 657 private: 658 FoldingSet<SCEV> UniqueSCEVs; 659 BumpPtrAllocator SCEVAllocator; 660 }; 661} 662 663#endif 664