ScalarEvolution.h revision 8b67f774e9c38b7718b2b300b628388f966df4e0
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// catagorize 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 FastFoldingSetNode { 53 // The SCEV baseclass this node corresponds to 54 const unsigned short SCEVType; 55 56 protected: 57 /// SubclassData - This field is initialized to zero and may be used in 58 /// subclasses to store miscelaneous information. 59 unsigned short SubclassData; 60 61 private: 62 SCEV(const SCEV &); // DO NOT IMPLEMENT 63 void operator=(const SCEV &); // DO NOT IMPLEMENT 64 protected: 65 virtual ~SCEV(); 66 public: 67 explicit SCEV(const FoldingSetNodeID &ID, unsigned SCEVTy) : 68 FastFoldingSetNode(ID), SCEVType(SCEVTy), SubclassData(0) {} 69 70 unsigned getSCEVType() const { return SCEVType; } 71 72 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 73 /// the specified loop. 74 virtual bool isLoopInvariant(const Loop *L) const = 0; 75 76 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 77 /// known way in the specified loop. This property being true implies that 78 /// the value is variant in the loop AND that we can emit an expression to 79 /// compute the value of the expression at any particular loop iteration. 80 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 81 82 /// getType - Return the LLVM type of this SCEV expression. 83 /// 84 virtual const Type *getType() const = 0; 85 86 /// isZero - Return true if the expression is a constant zero. 87 /// 88 bool isZero() const; 89 90 /// isOne - Return true if the expression is a constant one. 91 /// 92 bool isOne() const; 93 94 /// isAllOnesValue - Return true if the expression is a constant 95 /// all-ones value. 96 /// 97 bool isAllOnesValue() const; 98 99 /// hasOperand - Test whether this SCEV has Op as a direct or 100 /// indirect operand. 101 virtual bool hasOperand(const SCEV *Op) const = 0; 102 103 /// dominates - Return true if elements that makes up this SCEV dominates 104 /// the specified basic block. 105 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 106 107 /// properlyDominates - Return true if elements that makes up this SCEV 108 /// properly dominate the specified basic block. 109 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 110 111 /// print - Print out the internal representation of this scalar to the 112 /// specified stream. This should really only be used for debugging 113 /// purposes. 114 virtual void print(raw_ostream &OS) const = 0; 115 116 /// dump - This method is used for debugging. 117 /// 118 void dump() const; 119 }; 120 121 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 122 S.print(OS); 123 return OS; 124 } 125 126 /// SCEVCouldNotCompute - An object of this class is returned by queries that 127 /// could not be answered. For example, if you ask for the number of 128 /// iterations of a linked-list traversal loop, you will get one of these. 129 /// None of the standard SCEV operations are valid on this class, it is just a 130 /// marker. 131 struct SCEVCouldNotCompute : public SCEV { 132 SCEVCouldNotCompute(); 133 134 // None of these methods are valid for this object. 135 virtual bool isLoopInvariant(const Loop *L) const; 136 virtual const Type *getType() const; 137 virtual bool hasComputableLoopEvolution(const Loop *L) const; 138 virtual void print(raw_ostream &OS) const; 139 virtual bool hasOperand(const SCEV *Op) const; 140 141 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 142 return true; 143 } 144 145 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 146 return true; 147 } 148 149 /// Methods for support type inquiry through isa, cast, and dyn_cast: 150 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 151 static bool classof(const SCEV *S); 152 }; 153 154 /// ScalarEvolution - This class is the main scalar evolution driver. Because 155 /// client code (intentionally) can't do much with the SCEV objects directly, 156 /// they must ask this class for services. 157 /// 158 class ScalarEvolution : public FunctionPass { 159 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 160 /// notified whenever a Value is deleted. 161 class SCEVCallbackVH : public CallbackVH { 162 ScalarEvolution *SE; 163 virtual void deleted(); 164 virtual void allUsesReplacedWith(Value *New); 165 public: 166 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 167 }; 168 169 friend class SCEVCallbackVH; 170 friend struct SCEVExpander; 171 172 /// F - The function we are analyzing. 173 /// 174 Function *F; 175 176 /// LI - The loop information for the function we are currently analyzing. 177 /// 178 LoopInfo *LI; 179 180 /// TD - The target data information for the target we are targetting. 181 /// 182 TargetData *TD; 183 184 /// CouldNotCompute - This SCEV is used to represent unknown trip 185 /// counts and things. 186 SCEVCouldNotCompute CouldNotCompute; 187 188 /// Scalars - This is a cache of the scalars we have analyzed so far. 189 /// 190 std::map<SCEVCallbackVH, const SCEV *> Scalars; 191 192 /// BackedgeTakenInfo - Information about the backedge-taken count 193 /// of a loop. This currently inclues an exact count and a maximum count. 194 /// 195 struct BackedgeTakenInfo { 196 /// Exact - An expression indicating the exact backedge-taken count of 197 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 198 const SCEV *Exact; 199 200 /// Max - An expression indicating the least maximum backedge-taken 201 /// count of the loop that is known, or a SCEVCouldNotCompute. 202 const SCEV *Max; 203 204 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 205 Exact(exact), Max(exact) {} 206 207 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 208 Exact(exact), Max(max) {} 209 210 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 211 /// computed information, or whether it's all SCEVCouldNotCompute 212 /// values. 213 bool hasAnyInfo() const { 214 return !isa<SCEVCouldNotCompute>(Exact) || 215 !isa<SCEVCouldNotCompute>(Max); 216 } 217 }; 218 219 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 220 /// this function as they are computed. 221 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 222 223 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 224 /// the PHI instructions that we attempt to compute constant evolutions for. 225 /// This allows us to avoid potentially expensive recomputation of these 226 /// properties. An instruction maps to null if we are unable to compute its 227 /// exit value. 228 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 229 230 /// ValuesAtScopes - This map contains entries for all the expressions 231 /// that we attempt to compute getSCEVAtScope information for, which can 232 /// be expensive in extreme cases. 233 std::map<const SCEV *, 234 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 235 236 /// createSCEV - We know that there is no SCEV for the specified value. 237 /// Analyze the expression. 238 const SCEV *createSCEV(Value *V); 239 240 /// createNodeForPHI - Provide the special handling we need to analyze PHI 241 /// SCEVs. 242 const SCEV *createNodeForPHI(PHINode *PN); 243 244 /// createNodeForGEP - Provide the special handling we need to analyze GEP 245 /// SCEVs. 246 const SCEV *createNodeForGEP(Operator *GEP); 247 248 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 249 /// at most once for each SCEV+Loop pair. 250 /// 251 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 252 253 /// ForgetSymbolicValue - This looks up computed SCEV values for all 254 /// instructions that depend on the given instruction and removes them from 255 /// the Scalars map if they reference SymName. This is used during PHI 256 /// resolution. 257 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 258 259 /// getBECount - Subtract the end and start values and divide by the step, 260 /// rounding up, to get the number of times the backedge is executed. Return 261 /// CouldNotCompute if an intermediate computation overflows. 262 const SCEV *getBECount(const SCEV *Start, 263 const SCEV *End, 264 const SCEV *Step, 265 bool NoWrap); 266 267 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 268 /// loop, lazily computing new values if the loop hasn't been analyzed 269 /// yet. 270 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 271 272 /// ComputeBackedgeTakenCount - Compute the number of times the specified 273 /// loop will iterate. 274 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 275 276 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 277 /// backedge of the specified loop will execute if it exits via the 278 /// specified block. 279 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 280 BasicBlock *ExitingBlock); 281 282 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 283 /// backedge of the specified loop will execute if its exit condition 284 /// were a conditional branch of ExitCond, TBB, and FBB. 285 BackedgeTakenInfo 286 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 287 Value *ExitCond, 288 BasicBlock *TBB, 289 BasicBlock *FBB); 290 291 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 292 /// times the backedge of the specified loop will execute if its exit 293 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 294 /// and FBB. 295 BackedgeTakenInfo 296 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 297 ICmpInst *ExitCond, 298 BasicBlock *TBB, 299 BasicBlock *FBB); 300 301 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 302 /// of 'icmp op load X, cst', try to see if we can compute the 303 /// backedge-taken count. 304 const SCEV * 305 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 306 Constant *RHS, 307 const Loop *L, 308 ICmpInst::Predicate p); 309 310 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 311 /// a constant number of times (the condition evolves only from constants), 312 /// try to evaluate a few iterations of the loop until we get the exit 313 /// condition gets a value of ExitWhen (true or false). If we cannot 314 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 315 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 316 Value *Cond, 317 bool ExitWhen); 318 319 /// HowFarToZero - Return the number of times a backedge comparing the 320 /// specified value to zero will execute. If not computable, return 321 /// CouldNotCompute. 322 const SCEV *HowFarToZero(const SCEV *V, const Loop *L); 323 324 /// HowFarToNonZero - Return the number of times a backedge checking the 325 /// specified value for nonzero will execute. If not computable, return 326 /// CouldNotCompute. 327 const SCEV *HowFarToNonZero(const SCEV *V, const Loop *L); 328 329 /// HowManyLessThans - Return the number of times a backedge containing the 330 /// specified less-than comparison will execute. If not computable, return 331 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 332 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 333 const Loop *L, bool isSigned); 334 335 /// getLoopPredecessor - If the given loop's header has exactly one unique 336 /// predecessor outside the loop, return it. Otherwise return null. 337 BasicBlock *getLoopPredecessor(const Loop *L); 338 339 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 340 /// (which may not be an immediate predecessor) which has exactly one 341 /// successor from which BB is reachable, or null if no such block is 342 /// found. 343 BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 344 345 /// isImpliedCond - Test whether the condition described by Pred, LHS, 346 /// and RHS is true whenever the given Cond value evaluates to true. 347 bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred, 348 const SCEV *LHS, const SCEV *RHS, 349 bool Inverse); 350 351 /// isImpliedCondOperands - Test whether the condition described by Pred, 352 /// LHS, and RHS is true whenever the condition desribed by Pred, FoundLHS, 353 /// and FoundRHS is true. 354 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 355 const SCEV *LHS, const SCEV *RHS, 356 const SCEV *FoundLHS, const SCEV *FoundRHS); 357 358 /// isImpliedCondOperandsHelper - Test whether the condition described by 359 /// Pred, LHS, and RHS is true whenever the condition desribed by Pred, 360 /// FoundLHS, and FoundRHS is true. 361 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 362 const SCEV *LHS, const SCEV *RHS, 363 const SCEV *FoundLHS, const SCEV *FoundRHS); 364 365 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 366 /// in the header of its containing loop, we know the loop executes a 367 /// constant number of times, and the PHI node is just a recurrence 368 /// involving constants, fold it. 369 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 370 const Loop *L); 371 372 public: 373 static char ID; // Pass identification, replacement for typeid 374 ScalarEvolution(); 375 376 LLVMContext &getContext() const { return F->getContext(); } 377 378 /// isSCEVable - Test if values of the given type are analyzable within 379 /// the SCEV framework. This primarily includes integer types, and it 380 /// can optionally include pointer types if the ScalarEvolution class 381 /// has access to target-specific information. 382 bool isSCEVable(const Type *Ty) const; 383 384 /// getTypeSizeInBits - Return the size in bits of the specified type, 385 /// for which isSCEVable must return true. 386 uint64_t getTypeSizeInBits(const Type *Ty) const; 387 388 /// getEffectiveSCEVType - Return a type with the same bitwidth as 389 /// the given type and which represents how SCEV will treat the given 390 /// type, for which isSCEVable must return true. For pointer types, 391 /// this is the pointer-sized integer type. 392 const Type *getEffectiveSCEVType(const Type *Ty) const; 393 394 /// getSCEV - Return a SCEV expression for the full generality of the 395 /// specified expression. 396 const SCEV *getSCEV(Value *V); 397 398 const SCEV *getConstant(ConstantInt *V); 399 const SCEV *getConstant(const APInt& Val); 400 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 401 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 402 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 403 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 404 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 405 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 406 bool HasNUW = false, bool HasNSW = false); 407 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 408 bool HasNUW = false, bool HasNSW = false) { 409 SmallVector<const SCEV *, 2> Ops; 410 Ops.push_back(LHS); 411 Ops.push_back(RHS); 412 return getAddExpr(Ops, HasNUW, HasNSW); 413 } 414 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 415 const SCEV *Op2, 416 bool HasNUW = false, bool HasNSW = false) { 417 SmallVector<const SCEV *, 3> Ops; 418 Ops.push_back(Op0); 419 Ops.push_back(Op1); 420 Ops.push_back(Op2); 421 return getAddExpr(Ops, HasNUW, HasNSW); 422 } 423 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 424 bool HasNUW = false, bool HasNSW = false); 425 const SCEV *getMulExpr(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 getMulExpr(Ops, HasNUW, HasNSW); 431 } 432 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 433 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 434 const Loop *L, 435 bool HasNUW = false, bool HasNSW = false); 436 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 437 const Loop *L, 438 bool HasNUW = false, bool HasNSW = false); 439 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 440 const Loop *L, 441 bool HasNUW = false, bool HasNSW = false) { 442 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 443 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 444 } 445 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 446 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 447 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 448 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 449 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 450 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 451 const SCEV *getFieldOffsetExpr(const StructType *STy, unsigned FieldNo); 452 const SCEV *getAllocSizeExpr(const Type *AllocTy); 453 const SCEV *getUnknown(Value *V); 454 const SCEV *getCouldNotCompute(); 455 456 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 457 /// 458 const SCEV *getNegativeSCEV(const SCEV *V); 459 460 /// getNotSCEV - Return the SCEV object corresponding to ~V. 461 /// 462 const SCEV *getNotSCEV(const SCEV *V); 463 464 /// getMinusSCEV - Return LHS-RHS. 465 /// 466 const SCEV *getMinusSCEV(const SCEV *LHS, 467 const SCEV *RHS); 468 469 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 470 /// of the input value to the specified type. If the type must be 471 /// extended, it is zero extended. 472 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 473 474 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 475 /// of the input value to the specified type. If the type must be 476 /// extended, it is sign extended. 477 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 478 479 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 480 /// the input value to the specified type. If the type must be extended, 481 /// it is zero extended. The conversion must not be narrowing. 482 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 483 484 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 485 /// the input value to the specified type. If the type must be extended, 486 /// it is sign extended. The conversion must not be narrowing. 487 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 488 489 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 490 /// the input value to the specified type. If the type must be extended, 491 /// it is extended with unspecified bits. The conversion must not be 492 /// narrowing. 493 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 494 495 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 496 /// input value to the specified type. The conversion must not be 497 /// widening. 498 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 499 500 /// getIntegerSCEV - Given a SCEVable type, create a constant for the 501 /// specified signed integer value and return a SCEV for the constant. 502 const SCEV *getIntegerSCEV(int Val, const Type *Ty); 503 504 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 505 /// the types using zero-extension, and then perform a umax operation 506 /// with them. 507 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 508 const SCEV *RHS); 509 510 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 511 /// the types using zero-extension, and then perform a umin operation 512 /// with them. 513 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 514 const SCEV *RHS); 515 516 /// getSCEVAtScope - Return a SCEV expression for the specified value 517 /// at the specified scope in the program. The L value specifies a loop 518 /// nest to evaluate the expression at, where null is the top-level or a 519 /// specified loop is immediately inside of the loop. 520 /// 521 /// This method can be used to compute the exit value for a variable defined 522 /// in a loop by querying what the value will hold in the parent loop. 523 /// 524 /// In the case that a relevant loop exit value cannot be computed, the 525 /// original value V is returned. 526 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 527 528 /// getSCEVAtScope - This is a convenience function which does 529 /// getSCEVAtScope(getSCEV(V), L). 530 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 531 532 /// isLoopGuardedByCond - Test whether entry to the loop is protected by 533 /// a conditional between LHS and RHS. This is used to help avoid max 534 /// expressions in loop trip counts, and to eliminate casts. 535 bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 536 const SCEV *LHS, const SCEV *RHS); 537 538 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 539 /// protected by a conditional between LHS and RHS. This is used to 540 /// to eliminate casts. 541 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 542 const SCEV *LHS, const SCEV *RHS); 543 544 /// getBackedgeTakenCount - If the specified loop has a predictable 545 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 546 /// object. The backedge-taken count is the number of times the loop header 547 /// will be branched to from within the loop. This is one less than the 548 /// trip count of the loop, since it doesn't count the first iteration, 549 /// when the header is branched to from outside the loop. 550 /// 551 /// Note that it is not valid to call this method on a loop without a 552 /// loop-invariant backedge-taken count (see 553 /// hasLoopInvariantBackedgeTakenCount). 554 /// 555 const SCEV *getBackedgeTakenCount(const Loop *L); 556 557 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 558 /// return the least SCEV value that is known never to be less than the 559 /// actual backedge taken count. 560 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 561 562 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 563 /// has an analyzable loop-invariant backedge-taken count. 564 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 565 566 /// forgetLoopBackedgeTakenCount - This method should be called by the 567 /// client when it has changed a loop in a way that may effect 568 /// ScalarEvolution's ability to compute a trip count, or if the loop 569 /// is deleted. 570 void forgetLoopBackedgeTakenCount(const Loop *L); 571 572 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 573 /// is guaranteed to end in (at every loop iteration). It is, at the same 574 /// time, the minimum number of times S is divisible by 2. For example, 575 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 576 /// bitwidth of S. 577 uint32_t GetMinTrailingZeros(const SCEV *S); 578 579 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 580 /// 581 ConstantRange getUnsignedRange(const SCEV *S); 582 583 /// getSignedRange - Determine the signed range for a particular SCEV. 584 /// 585 ConstantRange getSignedRange(const SCEV *S); 586 587 /// isKnownNegative - Test if the given expression is known to be negative. 588 /// 589 bool isKnownNegative(const SCEV *S); 590 591 /// isKnownPositive - Test if the given expression is known to be positive. 592 /// 593 bool isKnownPositive(const SCEV *S); 594 595 /// isKnownNonNegative - Test if the given expression is known to be 596 /// non-negative. 597 /// 598 bool isKnownNonNegative(const SCEV *S); 599 600 /// isKnownNonPositive - Test if the given expression is known to be 601 /// non-positive. 602 /// 603 bool isKnownNonPositive(const SCEV *S); 604 605 /// isKnownNonZero - Test if the given expression is known to be 606 /// non-zero. 607 /// 608 bool isKnownNonZero(const SCEV *S); 609 610 /// isKnownNonZero - Test if the given expression is known to satisfy 611 /// the condition described by Pred, LHS, and RHS. 612 /// 613 bool isKnownPredicate(ICmpInst::Predicate Pred, 614 const SCEV *LHS, const SCEV *RHS); 615 616 virtual bool runOnFunction(Function &F); 617 virtual void releaseMemory(); 618 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 619 virtual void print(raw_ostream &OS, const Module* = 0) const; 620 621 private: 622 FoldingSet<SCEV> UniqueSCEVs; 623 BumpPtrAllocator SCEVAllocator; 624 }; 625} 626 627#endif 628