ScalarEvolution.h revision 32efba698df6aa35335eeb44d89288352d04746d
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 class 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 /// DT - The dominator tree. 185 /// 186 DominatorTree *DT; 187 188 /// CouldNotCompute - This SCEV is used to represent unknown trip 189 /// counts and things. 190 SCEVCouldNotCompute CouldNotCompute; 191 192 /// Scalars - This is a cache of the scalars we have analyzed so far. 193 /// 194 std::map<SCEVCallbackVH, const SCEV *> Scalars; 195 196 /// BackedgeTakenInfo - Information about the backedge-taken count 197 /// of a loop. This currently inclues an exact count and a maximum count. 198 /// 199 struct BackedgeTakenInfo { 200 /// Exact - An expression indicating the exact backedge-taken count of 201 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 202 const SCEV *Exact; 203 204 /// Max - An expression indicating the least maximum backedge-taken 205 /// count of the loop that is known, or a SCEVCouldNotCompute. 206 const SCEV *Max; 207 208 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 209 Exact(exact), Max(exact) {} 210 211 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 212 Exact(exact), Max(max) {} 213 214 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 215 /// computed information, or whether it's all SCEVCouldNotCompute 216 /// values. 217 bool hasAnyInfo() const { 218 return !isa<SCEVCouldNotCompute>(Exact) || 219 !isa<SCEVCouldNotCompute>(Max); 220 } 221 }; 222 223 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 224 /// this function as they are computed. 225 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 226 227 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 228 /// the PHI instructions that we attempt to compute constant evolutions for. 229 /// This allows us to avoid potentially expensive recomputation of these 230 /// properties. An instruction maps to null if we are unable to compute its 231 /// exit value. 232 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 233 234 /// ValuesAtScopes - This map contains entries for all the expressions 235 /// that we attempt to compute getSCEVAtScope information for, which can 236 /// be expensive in extreme cases. 237 std::map<const SCEV *, 238 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 239 240 /// createSCEV - We know that there is no SCEV for the specified value. 241 /// Analyze the expression. 242 const SCEV *createSCEV(Value *V); 243 244 /// createNodeForPHI - Provide the special handling we need to analyze PHI 245 /// SCEVs. 246 const SCEV *createNodeForPHI(PHINode *PN); 247 248 /// createNodeForGEP - Provide the special handling we need to analyze GEP 249 /// SCEVs. 250 const SCEV *createNodeForGEP(GEPOperator *GEP); 251 252 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 253 /// at most once for each SCEV+Loop pair. 254 /// 255 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 256 257 /// ForgetSymbolicValue - This looks up computed SCEV values for all 258 /// instructions that depend on the given instruction and removes them from 259 /// the Scalars map if they reference SymName. This is used during PHI 260 /// resolution. 261 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 262 263 /// getBECount - Subtract the end and start values and divide by the step, 264 /// rounding up, to get the number of times the backedge is executed. Return 265 /// CouldNotCompute if an intermediate computation overflows. 266 const SCEV *getBECount(const SCEV *Start, 267 const SCEV *End, 268 const SCEV *Step, 269 bool NoWrap); 270 271 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 272 /// loop, lazily computing new values if the loop hasn't been analyzed 273 /// yet. 274 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 275 276 /// ComputeBackedgeTakenCount - Compute the number of times the specified 277 /// loop will iterate. 278 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 279 280 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 281 /// backedge of the specified loop will execute if it exits via the 282 /// specified block. 283 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 284 BasicBlock *ExitingBlock); 285 286 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 287 /// backedge of the specified loop will execute if its exit condition 288 /// were a conditional branch of ExitCond, TBB, and FBB. 289 BackedgeTakenInfo 290 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 291 Value *ExitCond, 292 BasicBlock *TBB, 293 BasicBlock *FBB); 294 295 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 296 /// times the backedge of the specified loop will execute if its exit 297 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 298 /// and FBB. 299 BackedgeTakenInfo 300 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 301 ICmpInst *ExitCond, 302 BasicBlock *TBB, 303 BasicBlock *FBB); 304 305 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 306 /// of 'icmp op load X, cst', try to see if we can compute the 307 /// backedge-taken count. 308 const SCEV * 309 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 310 Constant *RHS, 311 const Loop *L, 312 ICmpInst::Predicate p); 313 314 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 315 /// a constant number of times (the condition evolves only from constants), 316 /// try to evaluate a few iterations of the loop until we get the exit 317 /// condition gets a value of ExitWhen (true or false). If we cannot 318 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 319 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 320 Value *Cond, 321 bool ExitWhen); 322 323 /// HowFarToZero - Return the number of times a backedge comparing the 324 /// specified value to zero will execute. If not computable, return 325 /// CouldNotCompute. 326 const SCEV *HowFarToZero(const SCEV *V, const Loop *L); 327 328 /// HowFarToNonZero - Return the number of times a backedge checking the 329 /// specified value for nonzero will execute. If not computable, return 330 /// CouldNotCompute. 331 const SCEV *HowFarToNonZero(const SCEV *V, const Loop *L); 332 333 /// HowManyLessThans - Return the number of times a backedge containing the 334 /// specified less-than comparison will execute. If not computable, return 335 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 336 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 337 const Loop *L, bool isSigned); 338 339 /// getLoopPredecessor - If the given loop's header has exactly one unique 340 /// predecessor outside the loop, return it. Otherwise return null. 341 BasicBlock *getLoopPredecessor(const Loop *L); 342 343 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 344 /// (which may not be an immediate predecessor) which has exactly one 345 /// successor from which BB is reachable, or null if no such block is 346 /// found. 347 BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 348 349 /// isImpliedCond - Test whether the condition described by Pred, LHS, 350 /// and RHS is true whenever the given Cond value evaluates to true. 351 bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred, 352 const SCEV *LHS, const SCEV *RHS, 353 bool Inverse); 354 355 /// isImpliedCondOperands - Test whether the condition described by Pred, 356 /// LHS, and RHS is true whenever the condition desribed by Pred, FoundLHS, 357 /// and FoundRHS is true. 358 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 359 const SCEV *LHS, const SCEV *RHS, 360 const SCEV *FoundLHS, const SCEV *FoundRHS); 361 362 /// isImpliedCondOperandsHelper - Test whether the condition described by 363 /// Pred, LHS, and RHS is true whenever the condition desribed by Pred, 364 /// FoundLHS, and FoundRHS is true. 365 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 366 const SCEV *LHS, const SCEV *RHS, 367 const SCEV *FoundLHS, const SCEV *FoundRHS); 368 369 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 370 /// in the header of its containing loop, we know the loop executes a 371 /// constant number of times, and the PHI node is just a recurrence 372 /// involving constants, fold it. 373 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 374 const Loop *L); 375 376 public: 377 static char ID; // Pass identification, replacement for typeid 378 ScalarEvolution(); 379 380 LLVMContext &getContext() const { return F->getContext(); } 381 382 /// isSCEVable - Test if values of the given type are analyzable within 383 /// the SCEV framework. This primarily includes integer types, and it 384 /// can optionally include pointer types if the ScalarEvolution class 385 /// has access to target-specific information. 386 bool isSCEVable(const Type *Ty) const; 387 388 /// getTypeSizeInBits - Return the size in bits of the specified type, 389 /// for which isSCEVable must return true. 390 uint64_t getTypeSizeInBits(const Type *Ty) const; 391 392 /// getEffectiveSCEVType - Return a type with the same bitwidth as 393 /// the given type and which represents how SCEV will treat the given 394 /// type, for which isSCEVable must return true. For pointer types, 395 /// this is the pointer-sized integer type. 396 const Type *getEffectiveSCEVType(const Type *Ty) const; 397 398 /// getSCEV - Return a SCEV expression for the full generality of the 399 /// specified expression. 400 const SCEV *getSCEV(Value *V); 401 402 const SCEV *getConstant(ConstantInt *V); 403 const SCEV *getConstant(const APInt& Val); 404 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 405 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 406 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 407 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 408 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 409 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 410 bool HasNUW = false, bool HasNSW = false); 411 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 412 bool HasNUW = false, bool HasNSW = false) { 413 SmallVector<const SCEV *, 2> Ops; 414 Ops.push_back(LHS); 415 Ops.push_back(RHS); 416 return getAddExpr(Ops, HasNUW, HasNSW); 417 } 418 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 419 const SCEV *Op2, 420 bool HasNUW = false, bool HasNSW = false) { 421 SmallVector<const SCEV *, 3> Ops; 422 Ops.push_back(Op0); 423 Ops.push_back(Op1); 424 Ops.push_back(Op2); 425 return getAddExpr(Ops, HasNUW, HasNSW); 426 } 427 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 428 bool HasNUW = false, bool HasNSW = false); 429 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 430 bool HasNUW = false, bool HasNSW = false) { 431 SmallVector<const SCEV *, 2> Ops; 432 Ops.push_back(LHS); 433 Ops.push_back(RHS); 434 return getMulExpr(Ops, HasNUW, HasNSW); 435 } 436 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 437 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 438 const Loop *L, 439 bool HasNUW = false, bool HasNSW = false); 440 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 441 const Loop *L, 442 bool HasNUW = false, bool HasNSW = false); 443 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 444 const Loop *L, 445 bool HasNUW = false, bool HasNSW = false) { 446 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 447 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 448 } 449 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 450 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 451 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 452 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 453 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 454 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 455 const SCEV *getUnknown(Value *V); 456 const SCEV *getCouldNotCompute(); 457 458 /// getSizeOfExpr - Return an expression for sizeof on the given type. 459 /// 460 const SCEV *getSizeOfExpr(const Type *AllocTy); 461 462 /// getAlignOfExpr - Return an expression for alignof on the given type. 463 /// 464 const SCEV *getAlignOfExpr(const Type *AllocTy); 465 466 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 467 /// 468 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 469 470 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 471 /// 472 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 473 474 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 475 /// 476 const SCEV *getNegativeSCEV(const SCEV *V); 477 478 /// getNotSCEV - Return the SCEV object corresponding to ~V. 479 /// 480 const SCEV *getNotSCEV(const SCEV *V); 481 482 /// getMinusSCEV - Return LHS-RHS. 483 /// 484 const SCEV *getMinusSCEV(const SCEV *LHS, 485 const SCEV *RHS); 486 487 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 488 /// of the input value to the specified type. If the type must be 489 /// extended, it is zero extended. 490 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 491 492 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 493 /// of the input value to the specified type. If the type must be 494 /// extended, it is sign extended. 495 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 496 497 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 498 /// the input value to the specified type. If the type must be extended, 499 /// it is zero extended. The conversion must not be narrowing. 500 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 501 502 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 503 /// the input value to the specified type. If the type must be extended, 504 /// it is sign extended. The conversion must not be narrowing. 505 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 506 507 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 508 /// the input value to the specified type. If the type must be extended, 509 /// it is extended with unspecified bits. The conversion must not be 510 /// narrowing. 511 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 512 513 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 514 /// input value to the specified type. The conversion must not be 515 /// widening. 516 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 517 518 /// getIntegerSCEV - Given a SCEVable type, create a constant for the 519 /// specified signed integer value and return a SCEV for the constant. 520 const SCEV *getIntegerSCEV(int64_t Val, const Type *Ty); 521 522 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 523 /// the types using zero-extension, and then perform a umax operation 524 /// with them. 525 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 526 const SCEV *RHS); 527 528 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 529 /// the types using zero-extension, and then perform a umin operation 530 /// with them. 531 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 532 const SCEV *RHS); 533 534 /// getSCEVAtScope - Return a SCEV expression for the specified value 535 /// at the specified scope in the program. The L value specifies a loop 536 /// nest to evaluate the expression at, where null is the top-level or a 537 /// specified loop is immediately inside of the loop. 538 /// 539 /// This method can be used to compute the exit value for a variable defined 540 /// in a loop by querying what the value will hold in the parent loop. 541 /// 542 /// In the case that a relevant loop exit value cannot be computed, the 543 /// original value V is returned. 544 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 545 546 /// getSCEVAtScope - This is a convenience function which does 547 /// getSCEVAtScope(getSCEV(V), L). 548 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 549 550 /// isLoopGuardedByCond - Test whether entry to the loop is protected by 551 /// a conditional between LHS and RHS. This is used to help avoid max 552 /// expressions in loop trip counts, and to eliminate casts. 553 bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 554 const SCEV *LHS, const SCEV *RHS); 555 556 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 557 /// protected by a conditional between LHS and RHS. This is used to 558 /// to eliminate casts. 559 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 560 const SCEV *LHS, const SCEV *RHS); 561 562 /// getBackedgeTakenCount - If the specified loop has a predictable 563 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 564 /// object. The backedge-taken count is the number of times the loop header 565 /// will be branched to from within the loop. This is one less than the 566 /// trip count of the loop, since it doesn't count the first iteration, 567 /// when the header is branched to from outside the loop. 568 /// 569 /// Note that it is not valid to call this method on a loop without a 570 /// loop-invariant backedge-taken count (see 571 /// hasLoopInvariantBackedgeTakenCount). 572 /// 573 const SCEV *getBackedgeTakenCount(const Loop *L); 574 575 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 576 /// return the least SCEV value that is known never to be less than the 577 /// actual backedge taken count. 578 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 579 580 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 581 /// has an analyzable loop-invariant backedge-taken count. 582 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 583 584 /// forgetLoop - This method should be called by the client when it has 585 /// changed a loop in a way that may effect ScalarEvolution's ability to 586 /// compute a trip count, or if the loop is deleted. 587 void forgetLoop(const Loop *L); 588 589 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 590 /// is guaranteed to end in (at every loop iteration). It is, at the same 591 /// time, the minimum number of times S is divisible by 2. For example, 592 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 593 /// bitwidth of S. 594 uint32_t GetMinTrailingZeros(const SCEV *S); 595 596 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 597 /// 598 ConstantRange getUnsignedRange(const SCEV *S); 599 600 /// getSignedRange - Determine the signed range for a particular SCEV. 601 /// 602 ConstantRange getSignedRange(const SCEV *S); 603 604 /// isKnownNegative - Test if the given expression is known to be negative. 605 /// 606 bool isKnownNegative(const SCEV *S); 607 608 /// isKnownPositive - Test if the given expression is known to be positive. 609 /// 610 bool isKnownPositive(const SCEV *S); 611 612 /// isKnownNonNegative - Test if the given expression is known to be 613 /// non-negative. 614 /// 615 bool isKnownNonNegative(const SCEV *S); 616 617 /// isKnownNonPositive - Test if the given expression is known to be 618 /// non-positive. 619 /// 620 bool isKnownNonPositive(const SCEV *S); 621 622 /// isKnownNonZero - Test if the given expression is known to be 623 /// non-zero. 624 /// 625 bool isKnownNonZero(const SCEV *S); 626 627 /// isKnownNonZero - Test if the given expression is known to satisfy 628 /// the condition described by Pred, LHS, and RHS. 629 /// 630 bool isKnownPredicate(ICmpInst::Predicate Pred, 631 const SCEV *LHS, const SCEV *RHS); 632 633 virtual bool runOnFunction(Function &F); 634 virtual void releaseMemory(); 635 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 636 virtual void print(raw_ostream &OS, const Module* = 0) const; 637 638 private: 639 FoldingSet<SCEV> UniqueSCEVs; 640 BumpPtrAllocator SCEVAllocator; 641 }; 642} 643 644#endif 645