ScalarEvolution.h revision fd447eff22637c3d47ce709468ab50b6243d0e4c
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 /// AllocationSequenceNumber - This is used as a deterministic tie 58 /// breaker when sorting SCEVs. 59 unsigned AllocationSequenceNumber; 60 61 // The SCEV baseclass this node corresponds to 62 const unsigned short SCEVType; 63 64 protected: 65 /// SubclassData - This field is initialized to zero and may be used in 66 /// subclasses to store miscellaneous information. 67 unsigned short SubclassData; 68 69 private: 70 SCEV(const SCEV &); // DO NOT IMPLEMENT 71 void operator=(const SCEV &); // DO NOT IMPLEMENT 72 protected: 73 virtual ~SCEV(); 74 public: 75 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned num, unsigned SCEVTy) : 76 FastID(ID), AllocationSequenceNumber(num), 77 SCEVType(SCEVTy), SubclassData(0) {} 78 79 unsigned getSCEVType() const { return SCEVType; } 80 81 /// getAllocationSequenceNumber - Return an arbitrary value which can be 82 /// used to deterministically order a sequence of SCEVs. 83 unsigned getAllocationSequenceNumber() const { 84 return AllocationSequenceNumber; 85 } 86 87 /// Profile - FoldingSet support. 88 void Profile(FoldingSetNodeID& ID) { ID = FastID; } 89 90 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 91 /// the specified loop. 92 virtual bool isLoopInvariant(const Loop *L) const = 0; 93 94 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 95 /// known way in the specified loop. This property being true implies that 96 /// the value is variant in the loop AND that we can emit an expression to 97 /// compute the value of the expression at any particular loop iteration. 98 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 99 100 /// getType - Return the LLVM type of this SCEV expression. 101 /// 102 virtual const Type *getType() const = 0; 103 104 /// isZero - Return true if the expression is a constant zero. 105 /// 106 bool isZero() const; 107 108 /// isOne - Return true if the expression is a constant one. 109 /// 110 bool isOne() const; 111 112 /// isAllOnesValue - Return true if the expression is a constant 113 /// all-ones value. 114 /// 115 bool isAllOnesValue() const; 116 117 /// hasOperand - Test whether this SCEV has Op as a direct or 118 /// indirect operand. 119 virtual bool hasOperand(const SCEV *Op) const = 0; 120 121 /// dominates - Return true if elements that makes up this SCEV dominates 122 /// the specified basic block. 123 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 124 125 /// properlyDominates - Return true if elements that makes up this SCEV 126 /// properly dominate the specified basic block. 127 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 128 129 /// print - Print out the internal representation of this scalar to the 130 /// specified stream. This should really only be used for debugging 131 /// purposes. 132 virtual void print(raw_ostream &OS) const = 0; 133 134 /// dump - This method is used for debugging. 135 /// 136 void dump() const; 137 }; 138 139 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 140 S.print(OS); 141 return OS; 142 } 143 144 /// SCEVCouldNotCompute - An object of this class is returned by queries that 145 /// could not be answered. For example, if you ask for the number of 146 /// iterations of a linked-list traversal loop, you will get one of these. 147 /// None of the standard SCEV operations are valid on this class, it is just a 148 /// marker. 149 struct SCEVCouldNotCompute : public SCEV { 150 SCEVCouldNotCompute(); 151 152 // None of these methods are valid for this object. 153 virtual bool isLoopInvariant(const Loop *L) const; 154 virtual const Type *getType() const; 155 virtual bool hasComputableLoopEvolution(const Loop *L) const; 156 virtual void print(raw_ostream &OS) const; 157 virtual bool hasOperand(const SCEV *Op) const; 158 159 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 160 return true; 161 } 162 163 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 164 return true; 165 } 166 167 /// Methods for support type inquiry through isa, cast, and dyn_cast: 168 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 169 static bool classof(const SCEV *S); 170 }; 171 172 /// ScalarEvolution - This class is the main scalar evolution driver. Because 173 /// client code (intentionally) can't do much with the SCEV objects directly, 174 /// they must ask this class for services. 175 /// 176 class ScalarEvolution : public FunctionPass { 177 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 178 /// notified whenever a Value is deleted. 179 class SCEVCallbackVH : public CallbackVH { 180 ScalarEvolution *SE; 181 virtual void deleted(); 182 virtual void allUsesReplacedWith(Value *New); 183 public: 184 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 185 }; 186 187 friend class SCEVCallbackVH; 188 friend class SCEVExpander; 189 190 /// F - The function we are analyzing. 191 /// 192 Function *F; 193 194 /// LI - The loop information for the function we are currently analyzing. 195 /// 196 LoopInfo *LI; 197 198 /// TD - The target data information for the target we are targeting. 199 /// 200 TargetData *TD; 201 202 /// DT - The dominator tree. 203 /// 204 DominatorTree *DT; 205 206 /// CouldNotCompute - This SCEV is used to represent unknown trip 207 /// counts and things. 208 SCEVCouldNotCompute CouldNotCompute; 209 210 /// Scalars - This is a cache of the scalars we have analyzed so far. 211 /// 212 std::map<SCEVCallbackVH, const SCEV *> Scalars; 213 214 /// BackedgeTakenInfo - Information about the backedge-taken count 215 /// of a loop. This currently includes an exact count and a maximum count. 216 /// 217 struct BackedgeTakenInfo { 218 /// Exact - An expression indicating the exact backedge-taken count of 219 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 220 const SCEV *Exact; 221 222 /// Max - An expression indicating the least maximum backedge-taken 223 /// count of the loop that is known, or a SCEVCouldNotCompute. 224 const SCEV *Max; 225 226 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 227 Exact(exact), Max(exact) {} 228 229 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 230 Exact(exact), Max(max) {} 231 232 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 233 /// computed information, or whether it's all SCEVCouldNotCompute 234 /// values. 235 bool hasAnyInfo() const { 236 return !isa<SCEVCouldNotCompute>(Exact) || 237 !isa<SCEVCouldNotCompute>(Max); 238 } 239 }; 240 241 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 242 /// this function as they are computed. 243 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 244 245 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 246 /// the PHI instructions that we attempt to compute constant evolutions for. 247 /// This allows us to avoid potentially expensive recomputation of these 248 /// properties. An instruction maps to null if we are unable to compute its 249 /// exit value. 250 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 251 252 /// ValuesAtScopes - This map contains entries for all the expressions 253 /// that we attempt to compute getSCEVAtScope information for, which can 254 /// be expensive in extreme cases. 255 std::map<const SCEV *, 256 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 257 258 /// createSCEV - We know that there is no SCEV for the specified value. 259 /// Analyze the expression. 260 const SCEV *createSCEV(Value *V); 261 262 /// createNodeForPHI - Provide the special handling we need to analyze PHI 263 /// SCEVs. 264 const SCEV *createNodeForPHI(PHINode *PN); 265 266 /// createNodeForGEP - Provide the special handling we need to analyze GEP 267 /// SCEVs. 268 const SCEV *createNodeForGEP(GEPOperator *GEP); 269 270 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 271 /// at most once for each SCEV+Loop pair. 272 /// 273 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 274 275 /// ForgetSymbolicValue - This looks up computed SCEV values for all 276 /// instructions that depend on the given instruction and removes them from 277 /// the Scalars map if they reference SymName. This is used during PHI 278 /// resolution. 279 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 280 281 /// getBECount - Subtract the end and start values and divide by the step, 282 /// rounding up, to get the number of times the backedge is executed. Return 283 /// CouldNotCompute if an intermediate computation overflows. 284 const SCEV *getBECount(const SCEV *Start, 285 const SCEV *End, 286 const SCEV *Step, 287 bool NoWrap); 288 289 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 290 /// loop, lazily computing new values if the loop hasn't been analyzed 291 /// yet. 292 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 293 294 /// ComputeBackedgeTakenCount - Compute the number of times the specified 295 /// loop will iterate. 296 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 297 298 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 299 /// backedge of the specified loop will execute if it exits via the 300 /// specified block. 301 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 302 BasicBlock *ExitingBlock); 303 304 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 305 /// backedge of the specified loop will execute if its exit condition 306 /// were a conditional branch of ExitCond, TBB, and FBB. 307 BackedgeTakenInfo 308 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 309 Value *ExitCond, 310 BasicBlock *TBB, 311 BasicBlock *FBB); 312 313 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 314 /// times the backedge of the specified loop will execute if its exit 315 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 316 /// and FBB. 317 BackedgeTakenInfo 318 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 319 ICmpInst *ExitCond, 320 BasicBlock *TBB, 321 BasicBlock *FBB); 322 323 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 324 /// of 'icmp op load X, cst', try to see if we can compute the 325 /// backedge-taken count. 326 BackedgeTakenInfo 327 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 328 Constant *RHS, 329 const Loop *L, 330 ICmpInst::Predicate p); 331 332 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 333 /// a constant number of times (the condition evolves only from constants), 334 /// try to evaluate a few iterations of the loop until we get the exit 335 /// condition gets a value of ExitWhen (true or false). If we cannot 336 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 337 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 338 Value *Cond, 339 bool ExitWhen); 340 341 /// HowFarToZero - Return the number of times a backedge comparing the 342 /// specified value to zero will execute. If not computable, return 343 /// CouldNotCompute. 344 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 345 346 /// HowFarToNonZero - Return the number of times a backedge checking the 347 /// specified value for nonzero will execute. If not computable, return 348 /// CouldNotCompute. 349 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 350 351 /// HowManyLessThans - Return the number of times a backedge containing the 352 /// specified less-than comparison will execute. If not computable, return 353 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 354 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 355 const Loop *L, bool isSigned); 356 357 /// getLoopPredecessor - If the given loop's header has exactly one unique 358 /// predecessor outside the loop, return it. Otherwise return null. 359 BasicBlock *getLoopPredecessor(const Loop *L); 360 361 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 362 /// (which may not be an immediate predecessor) which has exactly one 363 /// successor from which BB is reachable, or null if no such block is 364 /// found. 365 std::pair<BasicBlock *, BasicBlock *> 366 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 367 368 /// isImpliedCond - Test whether the condition described by Pred, LHS, 369 /// and RHS is true whenever the given Cond value evaluates to true. 370 bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred, 371 const SCEV *LHS, const SCEV *RHS, 372 bool Inverse); 373 374 /// isImpliedCondOperands - Test whether the condition described by Pred, 375 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 376 /// and FoundRHS is true. 377 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 378 const SCEV *LHS, const SCEV *RHS, 379 const SCEV *FoundLHS, const SCEV *FoundRHS); 380 381 /// isImpliedCondOperandsHelper - Test whether the condition described by 382 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 383 /// FoundLHS, and FoundRHS is true. 384 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 385 const SCEV *LHS, const SCEV *RHS, 386 const SCEV *FoundLHS, const SCEV *FoundRHS); 387 388 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 389 /// in the header of its containing loop, we know the loop executes a 390 /// constant number of times, and the PHI node is just a recurrence 391 /// involving constants, fold it. 392 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 393 const Loop *L); 394 395 /// isKnownPredicateWithRanges - Test if the given expression is known to 396 /// satisfy the condition described by Pred and the known constant ranges 397 /// of LHS and RHS. 398 /// 399 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 400 const SCEV *LHS, const SCEV *RHS); 401 402 public: 403 static char ID; // Pass identification, replacement for typeid 404 ScalarEvolution(); 405 406 LLVMContext &getContext() const { return F->getContext(); } 407 408 /// isSCEVable - Test if values of the given type are analyzable within 409 /// the SCEV framework. This primarily includes integer types, and it 410 /// can optionally include pointer types if the ScalarEvolution class 411 /// has access to target-specific information. 412 bool isSCEVable(const Type *Ty) const; 413 414 /// getTypeSizeInBits - Return the size in bits of the specified type, 415 /// for which isSCEVable must return true. 416 uint64_t getTypeSizeInBits(const Type *Ty) const; 417 418 /// getEffectiveSCEVType - Return a type with the same bitwidth as 419 /// the given type and which represents how SCEV will treat the given 420 /// type, for which isSCEVable must return true. For pointer types, 421 /// this is the pointer-sized integer type. 422 const Type *getEffectiveSCEVType(const Type *Ty) const; 423 424 /// getSCEV - Return a SCEV expression for the full generality of the 425 /// specified expression. 426 const SCEV *getSCEV(Value *V); 427 428 const SCEV *getConstant(ConstantInt *V); 429 const SCEV *getConstant(const APInt& Val); 430 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 431 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 432 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 433 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 434 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 435 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 436 bool HasNUW = false, bool HasNSW = false); 437 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 438 bool HasNUW = false, bool HasNSW = false) { 439 SmallVector<const SCEV *, 2> Ops; 440 Ops.push_back(LHS); 441 Ops.push_back(RHS); 442 return getAddExpr(Ops, HasNUW, HasNSW); 443 } 444 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 445 const SCEV *Op2, 446 bool HasNUW = false, bool HasNSW = false) { 447 SmallVector<const SCEV *, 3> Ops; 448 Ops.push_back(Op0); 449 Ops.push_back(Op1); 450 Ops.push_back(Op2); 451 return getAddExpr(Ops, HasNUW, HasNSW); 452 } 453 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 454 bool HasNUW = false, bool HasNSW = false); 455 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 456 bool HasNUW = false, bool HasNSW = false) { 457 SmallVector<const SCEV *, 2> Ops; 458 Ops.push_back(LHS); 459 Ops.push_back(RHS); 460 return getMulExpr(Ops, HasNUW, HasNSW); 461 } 462 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 463 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 464 const Loop *L, 465 bool HasNUW = false, bool HasNSW = false); 466 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 467 const Loop *L, 468 bool HasNUW = false, bool HasNSW = false); 469 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 470 const Loop *L, 471 bool HasNUW = false, bool HasNSW = false) { 472 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 473 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 474 } 475 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 476 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 477 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 478 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 479 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 480 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 481 const SCEV *getUnknown(Value *V); 482 const SCEV *getCouldNotCompute(); 483 484 /// getSizeOfExpr - Return an expression for sizeof on the given type. 485 /// 486 const SCEV *getSizeOfExpr(const Type *AllocTy); 487 488 /// getAlignOfExpr - Return an expression for alignof on the given type. 489 /// 490 const SCEV *getAlignOfExpr(const Type *AllocTy); 491 492 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 493 /// 494 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 495 496 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 497 /// 498 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 499 500 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 501 /// 502 const SCEV *getNegativeSCEV(const SCEV *V); 503 504 /// getNotSCEV - Return the SCEV object corresponding to ~V. 505 /// 506 const SCEV *getNotSCEV(const SCEV *V); 507 508 /// getMinusSCEV - Return LHS-RHS. 509 /// 510 const SCEV *getMinusSCEV(const SCEV *LHS, 511 const SCEV *RHS); 512 513 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 514 /// of the input value to the specified type. If the type must be 515 /// extended, it is zero extended. 516 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 517 518 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 519 /// of the input value to the specified type. If the type must be 520 /// extended, it is sign extended. 521 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 522 523 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 524 /// the input value to the specified type. If the type must be extended, 525 /// it is zero extended. The conversion must not be narrowing. 526 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 527 528 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 529 /// the input value to the specified type. If the type must be extended, 530 /// it is sign extended. The conversion must not be narrowing. 531 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 532 533 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 534 /// the input value to the specified type. If the type must be extended, 535 /// it is extended with unspecified bits. The conversion must not be 536 /// narrowing. 537 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 538 539 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 540 /// input value to the specified type. The conversion must not be 541 /// widening. 542 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 543 544 /// getIntegerSCEV - Given a SCEVable type, create a constant for the 545 /// specified signed integer value and return a SCEV for the constant. 546 const SCEV *getIntegerSCEV(int64_t Val, const Type *Ty); 547 548 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 549 /// the types using zero-extension, and then perform a umax operation 550 /// with them. 551 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 552 const SCEV *RHS); 553 554 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 555 /// the types using zero-extension, and then perform a umin operation 556 /// with them. 557 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 558 const SCEV *RHS); 559 560 /// getSCEVAtScope - Return a SCEV expression for the specified value 561 /// at the specified scope in the program. The L value specifies a loop 562 /// nest to evaluate the expression at, where null is the top-level or a 563 /// specified loop is immediately inside of the loop. 564 /// 565 /// This method can be used to compute the exit value for a variable defined 566 /// in a loop by querying what the value will hold in the parent loop. 567 /// 568 /// In the case that a relevant loop exit value cannot be computed, the 569 /// original value V is returned. 570 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 571 572 /// getSCEVAtScope - This is a convenience function which does 573 /// getSCEVAtScope(getSCEV(V), L). 574 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 575 576 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 577 /// by a conditional between LHS and RHS. This is used to help avoid max 578 /// expressions in loop trip counts, and to eliminate casts. 579 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 580 const SCEV *LHS, const SCEV *RHS); 581 582 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 583 /// protected by a conditional between LHS and RHS. This is used to 584 /// to eliminate casts. 585 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 586 const SCEV *LHS, const SCEV *RHS); 587 588 /// getBackedgeTakenCount - If the specified loop has a predictable 589 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 590 /// object. The backedge-taken count is the number of times the loop header 591 /// will be branched to from within the loop. This is one less than the 592 /// trip count of the loop, since it doesn't count the first iteration, 593 /// when the header is branched to from outside the loop. 594 /// 595 /// Note that it is not valid to call this method on a loop without a 596 /// loop-invariant backedge-taken count (see 597 /// hasLoopInvariantBackedgeTakenCount). 598 /// 599 const SCEV *getBackedgeTakenCount(const Loop *L); 600 601 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 602 /// return the least SCEV value that is known never to be less than the 603 /// actual backedge taken count. 604 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 605 606 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 607 /// has an analyzable loop-invariant backedge-taken count. 608 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 609 610 /// forgetLoop - This method should be called by the client when it has 611 /// changed a loop in a way that may effect ScalarEvolution's ability to 612 /// compute a trip count, or if the loop is deleted. 613 void forgetLoop(const Loop *L); 614 615 /// forgetValue - This method should be called by the client when it has 616 /// changed a value in a way that may effect its value, or which may 617 /// disconnect it from a def-use chain linking it to a loop. 618 void forgetValue(Value *V); 619 620 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 621 /// is guaranteed to end in (at every loop iteration). It is, at the same 622 /// time, the minimum number of times S is divisible by 2. For example, 623 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 624 /// bitwidth of S. 625 uint32_t GetMinTrailingZeros(const SCEV *S); 626 627 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 628 /// 629 ConstantRange getUnsignedRange(const SCEV *S); 630 631 /// getSignedRange - Determine the signed range for a particular SCEV. 632 /// 633 ConstantRange getSignedRange(const SCEV *S); 634 635 /// isKnownNegative - Test if the given expression is known to be negative. 636 /// 637 bool isKnownNegative(const SCEV *S); 638 639 /// isKnownPositive - Test if the given expression is known to be positive. 640 /// 641 bool isKnownPositive(const SCEV *S); 642 643 /// isKnownNonNegative - Test if the given expression is known to be 644 /// non-negative. 645 /// 646 bool isKnownNonNegative(const SCEV *S); 647 648 /// isKnownNonPositive - Test if the given expression is known to be 649 /// non-positive. 650 /// 651 bool isKnownNonPositive(const SCEV *S); 652 653 /// isKnownNonZero - Test if the given expression is known to be 654 /// non-zero. 655 /// 656 bool isKnownNonZero(const SCEV *S); 657 658 /// isKnownPredicate - Test if the given expression is known to satisfy 659 /// the condition described by Pred, LHS, and RHS. 660 /// 661 bool isKnownPredicate(ICmpInst::Predicate Pred, 662 const SCEV *LHS, const SCEV *RHS); 663 664 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 665 /// predicate Pred. Return true iff any changes were made. If the 666 /// operands are provably equal or inequal, LHS and RHS are set to 667 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 668 /// 669 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 670 const SCEV *&LHS, 671 const SCEV *&RHS); 672 673 virtual bool runOnFunction(Function &F); 674 virtual void releaseMemory(); 675 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 676 virtual void print(raw_ostream &OS, const Module* = 0) const; 677 678 private: 679 FoldingSet<SCEV> UniqueSCEVs; 680 BumpPtrAllocator SCEVAllocator; 681 unsigned CurAllocationSequenceNumber; 682 }; 683} 684 685#endif 686