ScalarEvolution.h revision 508955156a25a9abc470a29e1760aa176d341cf9
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/Analysis/LoopInfo.h" 26#include "llvm/Support/DataTypes.h" 27#include "llvm/Support/ValueHandle.h" 28#include "llvm/Support/Allocator.h" 29#include "llvm/ADT/FoldingSet.h" 30#include "llvm/ADT/DenseMap.h" 31#include <iosfwd> 32 33namespace llvm { 34 class APInt; 35 class ConstantInt; 36 class Type; 37 class ScalarEvolution; 38 class TargetData; 39 class LLVMContext; 40 41 /// SCEV - This class represents an analyzed expression in the program. These 42 /// are opaque objects that the client is not allowed to do much with 43 /// directly. 44 /// 45 class SCEV : public FoldingSetNode { 46 const unsigned SCEVType; // The SCEV baseclass this node corresponds to 47 48 SCEV(const SCEV &); // DO NOT IMPLEMENT 49 void operator=(const SCEV &); // DO NOT IMPLEMENT 50 protected: 51 virtual ~SCEV(); 52 public: 53 explicit SCEV(unsigned SCEVTy) : 54 SCEVType(SCEVTy) {} 55 56 virtual void Profile(FoldingSetNodeID &ID) const = 0; 57 58 unsigned getSCEVType() const { return SCEVType; } 59 60 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 61 /// the specified loop. 62 virtual bool isLoopInvariant(const Loop *L) const = 0; 63 64 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 65 /// known way in the specified loop. This property being true implies that 66 /// the value is variant in the loop AND that we can emit an expression to 67 /// compute the value of the expression at any particular loop iteration. 68 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 69 70 /// getType - Return the LLVM type of this SCEV expression. 71 /// 72 virtual const Type *getType() const = 0; 73 74 /// isZero - Return true if the expression is a constant zero. 75 /// 76 bool isZero() const; 77 78 /// isOne - Return true if the expression is a constant one. 79 /// 80 bool isOne() const; 81 82 /// isAllOnesValue - Return true if the expression is a constant 83 /// all-ones value. 84 /// 85 bool isAllOnesValue() const; 86 87 /// replaceSymbolicValuesWithConcrete - If this SCEV internally references 88 /// the symbolic value "Sym", construct and return a new SCEV that produces 89 /// the same value, but which uses the concrete value Conc instead of the 90 /// symbolic value. If this SCEV does not use the symbolic value, it 91 /// returns itself. 92 virtual const SCEV* 93 replaceSymbolicValuesWithConcrete(const SCEV* Sym, 94 const SCEV* Conc, 95 ScalarEvolution &SE) const = 0; 96 97 /// dominates - Return true if elements that makes up this SCEV dominates 98 /// the specified basic block. 99 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 100 101 /// print - Print out the internal representation of this scalar to the 102 /// specified stream. This should really only be used for debugging 103 /// purposes. 104 virtual void print(raw_ostream &OS) const = 0; 105 void print(std::ostream &OS) const; 106 void print(std::ostream *OS) const { if (OS) print(*OS); } 107 108 /// dump - This method is used for debugging. 109 /// 110 void dump() const; 111 }; 112 113 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 114 S.print(OS); 115 return OS; 116 } 117 118 inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) { 119 S.print(OS); 120 return OS; 121 } 122 123 /// SCEVCouldNotCompute - An object of this class is returned by queries that 124 /// could not be answered. For example, if you ask for the number of 125 /// iterations of a linked-list traversal loop, you will get one of these. 126 /// None of the standard SCEV operations are valid on this class, it is just a 127 /// marker. 128 struct SCEVCouldNotCompute : public SCEV { 129 SCEVCouldNotCompute(); 130 131 // None of these methods are valid for this object. 132 virtual void Profile(FoldingSetNodeID &ID) const; 133 virtual bool isLoopInvariant(const Loop *L) const; 134 virtual const Type *getType() const; 135 virtual bool hasComputableLoopEvolution(const Loop *L) const; 136 virtual void print(raw_ostream &OS) const; 137 virtual const SCEV* 138 replaceSymbolicValuesWithConcrete(const SCEV* Sym, 139 const SCEV* Conc, 140 ScalarEvolution &SE) const; 141 142 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 143 return true; 144 } 145 146 /// Methods for support type inquiry through isa, cast, and dyn_cast: 147 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 148 static bool classof(const SCEV *S); 149 }; 150 151 /// ScalarEvolution - This class is the main scalar evolution driver. Because 152 /// client code (intentionally) can't do much with the SCEV objects directly, 153 /// they must ask this class for services. 154 /// 155 class ScalarEvolution : public FunctionPass { 156 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 157 /// notified whenever a Value is deleted. 158 class SCEVCallbackVH : public CallbackVH { 159 ScalarEvolution *SE; 160 virtual void deleted(); 161 virtual void allUsesReplacedWith(Value *New); 162 public: 163 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 164 }; 165 166 friend class SCEVCallbackVH; 167 friend class SCEVExpander; 168 169 /// F - The function we are analyzing. 170 /// 171 Function *F; 172 173 /// LI - The loop information for the function we are currently analyzing. 174 /// 175 LoopInfo *LI; 176 177 /// TD - The target data information for the target we are targetting. 178 /// 179 TargetData *TD; 180 181 /// CouldNotCompute - This SCEV is used to represent unknown trip 182 /// counts and things. 183 SCEVCouldNotCompute CouldNotCompute; 184 185 /// Scalars - This is a cache of the scalars we have analyzed so far. 186 /// 187 std::map<SCEVCallbackVH, const SCEV*> Scalars; 188 189 /// BackedgeTakenInfo - Information about the backedge-taken count 190 /// of a loop. This currently inclues an exact count and a maximum count. 191 /// 192 struct BackedgeTakenInfo { 193 /// Exact - An expression indicating the exact backedge-taken count of 194 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 195 const SCEV* Exact; 196 197 /// Exact - An expression indicating the least maximum backedge-taken 198 /// count of the loop that is known, or a SCEVCouldNotCompute. 199 const SCEV* Max; 200 201 /*implicit*/ BackedgeTakenInfo(const SCEV* exact) : 202 Exact(exact), Max(exact) {} 203 204 BackedgeTakenInfo(const SCEV* exact, const SCEV* max) : 205 Exact(exact), Max(max) {} 206 207 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 208 /// computed information, or whether it's all SCEVCouldNotCompute 209 /// values. 210 bool hasAnyInfo() const { 211 return !isa<SCEVCouldNotCompute>(Exact) || 212 !isa<SCEVCouldNotCompute>(Max); 213 } 214 }; 215 216 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 217 /// this function as they are computed. 218 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 219 220 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 221 /// the PHI instructions that we attempt to compute constant evolutions for. 222 /// This allows us to avoid potentially expensive recomputation of these 223 /// properties. An instruction maps to null if we are unable to compute its 224 /// exit value. 225 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 226 227 /// ValuesAtScopes - This map contains entries for all the instructions 228 /// that we attempt to compute getSCEVAtScope information for without 229 /// using SCEV techniques, which can be expensive. 230 std::map<Instruction *, std::map<const Loop *, Constant *> > ValuesAtScopes; 231 232 /// createSCEV - We know that there is no SCEV for the specified value. 233 /// Analyze the expression. 234 const SCEV* createSCEV(Value *V); 235 236 /// createNodeForPHI - Provide the special handling we need to analyze PHI 237 /// SCEVs. 238 const SCEV* createNodeForPHI(PHINode *PN); 239 240 /// createNodeForGEP - Provide the special handling we need to analyze GEP 241 /// SCEVs. 242 const SCEV* createNodeForGEP(User *GEP); 243 244 /// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value 245 /// for the specified instruction and replaces any references to the 246 /// symbolic value SymName with the specified value. This is used during 247 /// PHI resolution. 248 void ReplaceSymbolicValueWithConcrete(Instruction *I, 249 const SCEV* SymName, 250 const SCEV* NewVal); 251 252 /// getBECount - Subtract the end and start values and divide by the step, 253 /// rounding up, to get the number of times the backedge is executed. Return 254 /// CouldNotCompute if an intermediate computation overflows. 255 const SCEV* getBECount(const SCEV* Start, 256 const SCEV* End, 257 const SCEV* Step); 258 259 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 260 /// loop, lazily computing new values if the loop hasn't been analyzed 261 /// yet. 262 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 263 264 /// ComputeBackedgeTakenCount - Compute the number of times the specified 265 /// loop will iterate. 266 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 267 268 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 269 /// backedge of the specified loop will execute if it exits via the 270 /// specified block. 271 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 272 BasicBlock *ExitingBlock); 273 274 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 275 /// backedge of the specified loop will execute if its exit condition 276 /// were a conditional branch of ExitCond, TBB, and FBB. 277 BackedgeTakenInfo 278 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 279 Value *ExitCond, 280 BasicBlock *TBB, 281 BasicBlock *FBB); 282 283 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 284 /// times the backedge of the specified loop will execute if its exit 285 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 286 /// and FBB. 287 BackedgeTakenInfo 288 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 289 ICmpInst *ExitCond, 290 BasicBlock *TBB, 291 BasicBlock *FBB); 292 293 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 294 /// of 'icmp op load X, cst', try to see if we can compute the trip count. 295 const SCEV* 296 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 297 Constant *RHS, 298 const Loop *L, 299 ICmpInst::Predicate p); 300 301 /// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute 302 /// a constant number of times (the condition evolves only from constants), 303 /// try to evaluate a few iterations of the loop until we get the exit 304 /// condition gets a value of ExitWhen (true or false). If we cannot 305 /// evaluate the trip count of the loop, return CouldNotCompute. 306 const SCEV* ComputeBackedgeTakenCountExhaustively(const Loop *L, 307 Value *Cond, 308 bool ExitWhen); 309 310 /// HowFarToZero - Return the number of times a backedge comparing the 311 /// specified value to zero will execute. If not computable, return 312 /// CouldNotCompute. 313 const SCEV* HowFarToZero(const SCEV *V, const Loop *L); 314 315 /// HowFarToNonZero - Return the number of times a backedge checking the 316 /// specified value for nonzero will execute. If not computable, return 317 /// CouldNotCompute. 318 const SCEV* HowFarToNonZero(const SCEV *V, const Loop *L); 319 320 /// HowManyLessThans - Return the number of times a backedge containing the 321 /// specified less-than comparison will execute. If not computable, return 322 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 323 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 324 const Loop *L, bool isSigned); 325 326 /// getLoopPredecessor - If the given loop's header has exactly one unique 327 /// predecessor outside the loop, return it. Otherwise return null. 328 BasicBlock *getLoopPredecessor(const Loop *L); 329 330 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 331 /// (which may not be an immediate predecessor) which has exactly one 332 /// successor from which BB is reachable, or null if no such block is 333 /// found. 334 BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 335 336 /// isNecessaryCond - Test whether the given CondValue value is a condition 337 /// which is at least as strict as the one described by Pred, LHS, and RHS. 338 bool isNecessaryCond(Value *Cond, ICmpInst::Predicate Pred, 339 const SCEV *LHS, const SCEV *RHS, 340 bool Inverse); 341 342 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 343 /// in the header of its containing loop, we know the loop executes a 344 /// constant number of times, and the PHI node is just a recurrence 345 /// involving constants, fold it. 346 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 347 const Loop *L); 348 349 /// forgetLoopPHIs - Delete the memoized SCEVs associated with the 350 /// PHI nodes in the given loop. This is used when the trip count of 351 /// the loop may have changed. 352 void forgetLoopPHIs(const Loop *L); 353 354 public: 355 static char ID; // Pass identification, replacement for typeid 356 ScalarEvolution(); 357 358 LLVMContext* getContext() const { return Context; } 359 360 /// isSCEVable - Test if values of the given type are analyzable within 361 /// the SCEV framework. This primarily includes integer types, and it 362 /// can optionally include pointer types if the ScalarEvolution class 363 /// has access to target-specific information. 364 bool isSCEVable(const Type *Ty) const; 365 366 /// getTypeSizeInBits - Return the size in bits of the specified type, 367 /// for which isSCEVable must return true. 368 uint64_t getTypeSizeInBits(const Type *Ty) const; 369 370 /// getEffectiveSCEVType - Return a type with the same bitwidth as 371 /// the given type and which represents how SCEV will treat the given 372 /// type, for which isSCEVable must return true. For pointer types, 373 /// this is the pointer-sized integer type. 374 const Type *getEffectiveSCEVType(const Type *Ty) const; 375 376 /// getSCEV - Return a SCEV expression handle for the full generality of the 377 /// specified expression. 378 const SCEV* getSCEV(Value *V); 379 380 const SCEV* getConstant(ConstantInt *V); 381 const SCEV* getConstant(const APInt& Val); 382 const SCEV* getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 383 const SCEV* getTruncateExpr(const SCEV* Op, const Type *Ty); 384 const SCEV* getZeroExtendExpr(const SCEV* Op, const Type *Ty); 385 const SCEV* getSignExtendExpr(const SCEV* Op, const Type *Ty); 386 const SCEV* getAnyExtendExpr(const SCEV* Op, const Type *Ty); 387 const SCEV* getAddExpr(SmallVectorImpl<const SCEV*> &Ops); 388 const SCEV* getAddExpr(const SCEV* LHS, const SCEV* RHS) { 389 SmallVector<const SCEV*, 2> Ops; 390 Ops.push_back(LHS); 391 Ops.push_back(RHS); 392 return getAddExpr(Ops); 393 } 394 const SCEV* getAddExpr(const SCEV* Op0, const SCEV* Op1, 395 const SCEV* Op2) { 396 SmallVector<const SCEV*, 3> Ops; 397 Ops.push_back(Op0); 398 Ops.push_back(Op1); 399 Ops.push_back(Op2); 400 return getAddExpr(Ops); 401 } 402 const SCEV* getMulExpr(SmallVectorImpl<const SCEV*> &Ops); 403 const SCEV* getMulExpr(const SCEV* LHS, const SCEV* RHS) { 404 SmallVector<const SCEV*, 2> Ops; 405 Ops.push_back(LHS); 406 Ops.push_back(RHS); 407 return getMulExpr(Ops); 408 } 409 const SCEV* getUDivExpr(const SCEV* LHS, const SCEV* RHS); 410 const SCEV* getAddRecExpr(const SCEV* Start, const SCEV* Step, 411 const Loop *L); 412 const SCEV* getAddRecExpr(SmallVectorImpl<const SCEV*> &Operands, 413 const Loop *L); 414 const SCEV* getAddRecExpr(const SmallVectorImpl<const SCEV*> &Operands, 415 const Loop *L) { 416 SmallVector<const SCEV*, 4> NewOp(Operands.begin(), Operands.end()); 417 return getAddRecExpr(NewOp, L); 418 } 419 const SCEV* getSMaxExpr(const SCEV* LHS, const SCEV* RHS); 420 const SCEV* getSMaxExpr(SmallVectorImpl<const SCEV*> &Operands); 421 const SCEV* getUMaxExpr(const SCEV* LHS, const SCEV* RHS); 422 const SCEV* getUMaxExpr(SmallVectorImpl<const SCEV*> &Operands); 423 const SCEV* getSMinExpr(const SCEV* LHS, const SCEV* RHS); 424 const SCEV* getUMinExpr(const SCEV* LHS, const SCEV* RHS); 425 const SCEV* getUnknown(Value *V); 426 const SCEV* getCouldNotCompute(); 427 428 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 429 /// 430 const SCEV* getNegativeSCEV(const SCEV* V); 431 432 /// getNotSCEV - Return the SCEV object corresponding to ~V. 433 /// 434 const SCEV* getNotSCEV(const SCEV* V); 435 436 /// getMinusSCEV - Return LHS-RHS. 437 /// 438 const SCEV* getMinusSCEV(const SCEV* LHS, 439 const SCEV* RHS); 440 441 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 442 /// of the input value to the specified type. If the type must be 443 /// extended, it is zero extended. 444 const SCEV* getTruncateOrZeroExtend(const SCEV* V, const Type *Ty); 445 446 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 447 /// of the input value to the specified type. If the type must be 448 /// extended, it is sign extended. 449 const SCEV* getTruncateOrSignExtend(const SCEV* V, const Type *Ty); 450 451 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 452 /// the input value to the specified type. If the type must be extended, 453 /// it is zero extended. The conversion must not be narrowing. 454 const SCEV* getNoopOrZeroExtend(const SCEV* V, const Type *Ty); 455 456 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 457 /// the input value to the specified type. If the type must be extended, 458 /// it is sign extended. The conversion must not be narrowing. 459 const SCEV* getNoopOrSignExtend(const SCEV* V, const Type *Ty); 460 461 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 462 /// the input value to the specified type. If the type must be extended, 463 /// it is extended with unspecified bits. The conversion must not be 464 /// narrowing. 465 const SCEV* getNoopOrAnyExtend(const SCEV* V, const Type *Ty); 466 467 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 468 /// input value to the specified type. The conversion must not be 469 /// widening. 470 const SCEV* getTruncateOrNoop(const SCEV* V, const Type *Ty); 471 472 /// getIntegerSCEV - Given a SCEVable type, create a constant for the 473 /// specified signed integer value and return a SCEV for the constant. 474 const SCEV* getIntegerSCEV(int Val, const Type *Ty); 475 476 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 477 /// the types using zero-extension, and then perform a umax operation 478 /// with them. 479 const SCEV* getUMaxFromMismatchedTypes(const SCEV* LHS, 480 const SCEV* RHS); 481 482 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 483 /// the types using zero-extension, and then perform a umin operation 484 /// with them. 485 const SCEV* getUMinFromMismatchedTypes(const SCEV* LHS, 486 const SCEV* RHS); 487 488 /// hasSCEV - Return true if the SCEV for this value has already been 489 /// computed. 490 bool hasSCEV(Value *V) const; 491 492 /// setSCEV - Insert the specified SCEV into the map of current SCEVs for 493 /// the specified value. 494 void setSCEV(Value *V, const SCEV* H); 495 496 /// getSCEVAtScope - Return a SCEV expression handle for the specified value 497 /// at the specified scope in the program. The L value specifies a loop 498 /// nest to evaluate the expression at, where null is the top-level or a 499 /// specified loop is immediately inside of the loop. 500 /// 501 /// This method can be used to compute the exit value for a variable defined 502 /// in a loop by querying what the value will hold in the parent loop. 503 /// 504 /// In the case that a relevant loop exit value cannot be computed, the 505 /// original value V is returned. 506 const SCEV* getSCEVAtScope(const SCEV *S, const Loop *L); 507 508 /// getSCEVAtScope - This is a convenience function which does 509 /// getSCEVAtScope(getSCEV(V), L). 510 const SCEV* getSCEVAtScope(Value *V, const Loop *L); 511 512 /// isLoopGuardedByCond - Test whether entry to the loop is protected by 513 /// a conditional between LHS and RHS. This is used to help avoid max 514 /// expressions in loop trip counts. 515 bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 516 const SCEV *LHS, const SCEV *RHS); 517 518 /// getBackedgeTakenCount - If the specified loop has a predictable 519 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 520 /// object. The backedge-taken count is the number of times the loop header 521 /// will be branched to from within the loop. This is one less than the 522 /// trip count of the loop, since it doesn't count the first iteration, 523 /// when the header is branched to from outside the loop. 524 /// 525 /// Note that it is not valid to call this method on a loop without a 526 /// loop-invariant backedge-taken count (see 527 /// hasLoopInvariantBackedgeTakenCount). 528 /// 529 const SCEV* getBackedgeTakenCount(const Loop *L); 530 531 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 532 /// return the least SCEV value that is known never to be less than the 533 /// actual backedge taken count. 534 const SCEV* getMaxBackedgeTakenCount(const Loop *L); 535 536 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 537 /// has an analyzable loop-invariant backedge-taken count. 538 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 539 540 /// forgetLoopBackedgeTakenCount - This method should be called by the 541 /// client when it has changed a loop in a way that may effect 542 /// ScalarEvolution's ability to compute a trip count, or if the loop 543 /// is deleted. 544 void forgetLoopBackedgeTakenCount(const Loop *L); 545 546 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 547 /// is guaranteed to end in (at every loop iteration). It is, at the same 548 /// time, the minimum number of times S is divisible by 2. For example, 549 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 550 /// bitwidth of S. 551 uint32_t GetMinTrailingZeros(const SCEV* S); 552 553 /// GetMinLeadingZeros - Determine the minimum number of zero bits that S is 554 /// guaranteed to begin with (at every loop iteration). 555 uint32_t GetMinLeadingZeros(const SCEV* S); 556 557 /// GetMinSignBits - Determine the minimum number of sign bits that S is 558 /// guaranteed to begin with. 559 uint32_t GetMinSignBits(const SCEV* S); 560 561 virtual bool runOnFunction(Function &F); 562 virtual void releaseMemory(); 563 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 564 void print(raw_ostream &OS, const Module* = 0) const; 565 virtual void print(std::ostream &OS, const Module* = 0) const; 566 void print(std::ostream *OS, const Module* M = 0) const { 567 if (OS) print(*OS, M); 568 } 569 570 private: 571 FoldingSet<SCEV> UniqueSCEVs; 572 BumpPtrAllocator SCEVAllocator; 573 }; 574} 575 576#endif 577