ScalarEvolution.h revision ab37f50838350e1104579fbd1f7c8820473485a5
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 class SCEVUnknown; 48 49 /// SCEV - This class represents an analyzed expression in the program. These 50 /// are opaque objects that the client is not allowed to do much with 51 /// directly. 52 /// 53 class SCEV : public FoldingSetNode { 54 /// FastID - A reference to an Interned FoldingSetNodeID for this node. 55 /// The ScalarEvolution's BumpPtrAllocator holds the data. 56 FoldingSetNodeIDRef FastID; 57 58 // The SCEV baseclass this node corresponds to 59 const unsigned short SCEVType; 60 61 protected: 62 /// SubclassData - This field is initialized to zero and may be used in 63 /// subclasses to store miscellaneous information. 64 unsigned short SubclassData; 65 66 private: 67 SCEV(const SCEV &); // DO NOT IMPLEMENT 68 void operator=(const SCEV &); // DO NOT IMPLEMENT 69 protected: 70 virtual ~SCEV(); 71 public: 72 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) : 73 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {} 74 75 unsigned getSCEVType() const { return SCEVType; } 76 77 /// Profile - FoldingSet support. 78 void Profile(FoldingSetNodeID& ID) { ID = FastID; } 79 80 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 81 /// the specified loop. 82 virtual bool isLoopInvariant(const Loop *L) const = 0; 83 84 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 85 /// known way in the specified loop. This property being true implies that 86 /// the value is variant in the loop AND that we can emit an expression to 87 /// compute the value of the expression at any particular loop iteration. 88 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 89 90 /// getType - Return the LLVM type of this SCEV expression. 91 /// 92 virtual const Type *getType() const = 0; 93 94 /// isZero - Return true if the expression is a constant zero. 95 /// 96 bool isZero() const; 97 98 /// isOne - Return true if the expression is a constant one. 99 /// 100 bool isOne() const; 101 102 /// isAllOnesValue - Return true if the expression is a constant 103 /// all-ones value. 104 /// 105 bool isAllOnesValue() const; 106 107 /// hasOperand - Test whether this SCEV has Op as a direct or 108 /// indirect operand. 109 virtual bool hasOperand(const SCEV *Op) const = 0; 110 111 /// dominates - Return true if elements that makes up this SCEV dominates 112 /// the specified basic block. 113 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 114 115 /// properlyDominates - Return true if elements that makes up this SCEV 116 /// properly dominate the specified basic block. 117 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const = 0; 118 119 /// print - Print out the internal representation of this scalar to the 120 /// specified stream. This should really only be used for debugging 121 /// purposes. 122 virtual void print(raw_ostream &OS) const = 0; 123 124 /// dump - This method is used for debugging. 125 /// 126 void dump() const; 127 }; 128 129 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { 130 S.print(OS); 131 return OS; 132 } 133 134 /// SCEVCouldNotCompute - An object of this class is returned by queries that 135 /// could not be answered. For example, if you ask for the number of 136 /// iterations of a linked-list traversal loop, you will get one of these. 137 /// None of the standard SCEV operations are valid on this class, it is just a 138 /// marker. 139 struct SCEVCouldNotCompute : public SCEV { 140 SCEVCouldNotCompute(); 141 142 // None of these methods are valid for this object. 143 virtual bool isLoopInvariant(const Loop *L) const; 144 virtual const Type *getType() const; 145 virtual bool hasComputableLoopEvolution(const Loop *L) const; 146 virtual void print(raw_ostream &OS) const; 147 virtual bool hasOperand(const SCEV *Op) const; 148 149 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 150 return true; 151 } 152 153 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const { 154 return true; 155 } 156 157 /// Methods for support type inquiry through isa, cast, and dyn_cast: 158 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 159 static bool classof(const SCEV *S); 160 }; 161 162 /// ScalarEvolution - This class is the main scalar evolution driver. Because 163 /// client code (intentionally) can't do much with the SCEV objects directly, 164 /// they must ask this class for services. 165 /// 166 class ScalarEvolution : public FunctionPass { 167 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be 168 /// notified whenever a Value is deleted. 169 class SCEVCallbackVH : public CallbackVH { 170 ScalarEvolution *SE; 171 virtual void deleted(); 172 virtual void allUsesReplacedWith(Value *New); 173 public: 174 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); 175 }; 176 177 friend class SCEVCallbackVH; 178 friend class SCEVExpander; 179 friend class SCEVUnknown; 180 181 /// F - The function we are analyzing. 182 /// 183 Function *F; 184 185 /// LI - The loop information for the function we are currently analyzing. 186 /// 187 LoopInfo *LI; 188 189 /// TD - The target data information for the target we are targeting. 190 /// 191 TargetData *TD; 192 193 /// DT - The dominator tree. 194 /// 195 DominatorTree *DT; 196 197 /// CouldNotCompute - This SCEV is used to represent unknown trip 198 /// counts and things. 199 SCEVCouldNotCompute CouldNotCompute; 200 201 /// Scalars - This is a cache of the scalars we have analyzed so far. 202 /// 203 std::map<SCEVCallbackVH, const SCEV *> Scalars; 204 205 /// BackedgeTakenInfo - Information about the backedge-taken count 206 /// of a loop. This currently includes an exact count and a maximum count. 207 /// 208 struct BackedgeTakenInfo { 209 /// Exact - An expression indicating the exact backedge-taken count of 210 /// the loop if it is known, or a SCEVCouldNotCompute otherwise. 211 const SCEV *Exact; 212 213 /// Max - An expression indicating the least maximum backedge-taken 214 /// count of the loop that is known, or a SCEVCouldNotCompute. 215 const SCEV *Max; 216 217 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : 218 Exact(exact), Max(exact) {} 219 220 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) : 221 Exact(exact), Max(max) {} 222 223 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any 224 /// computed information, or whether it's all SCEVCouldNotCompute 225 /// values. 226 bool hasAnyInfo() const { 227 return !isa<SCEVCouldNotCompute>(Exact) || 228 !isa<SCEVCouldNotCompute>(Max); 229 } 230 }; 231 232 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for 233 /// this function as they are computed. 234 std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; 235 236 /// ConstantEvolutionLoopExitValue - This map contains entries for all of 237 /// the PHI instructions that we attempt to compute constant evolutions for. 238 /// This allows us to avoid potentially expensive recomputation of these 239 /// properties. An instruction maps to null if we are unable to compute its 240 /// exit value. 241 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; 242 243 /// ValuesAtScopes - This map contains entries for all the expressions 244 /// that we attempt to compute getSCEVAtScope information for, which can 245 /// be expensive in extreme cases. 246 std::map<const SCEV *, 247 std::map<const Loop *, const SCEV *> > ValuesAtScopes; 248 249 /// createSCEV - We know that there is no SCEV for the specified value. 250 /// Analyze the expression. 251 const SCEV *createSCEV(Value *V); 252 253 /// createNodeForPHI - Provide the special handling we need to analyze PHI 254 /// SCEVs. 255 const SCEV *createNodeForPHI(PHINode *PN); 256 257 /// createNodeForGEP - Provide the special handling we need to analyze GEP 258 /// SCEVs. 259 const SCEV *createNodeForGEP(GEPOperator *GEP); 260 261 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called 262 /// at most once for each SCEV+Loop pair. 263 /// 264 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L); 265 266 /// ForgetSymbolicValue - This looks up computed SCEV values for all 267 /// instructions that depend on the given instruction and removes them from 268 /// the Scalars map if they reference SymName. This is used during PHI 269 /// resolution. 270 void ForgetSymbolicName(Instruction *I, const SCEV *SymName); 271 272 /// getBECount - Subtract the end and start values and divide by the step, 273 /// rounding up, to get the number of times the backedge is executed. Return 274 /// CouldNotCompute if an intermediate computation overflows. 275 const SCEV *getBECount(const SCEV *Start, 276 const SCEV *End, 277 const SCEV *Step, 278 bool NoWrap); 279 280 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given 281 /// loop, lazily computing new values if the loop hasn't been analyzed 282 /// yet. 283 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); 284 285 /// ComputeBackedgeTakenCount - Compute the number of times the specified 286 /// loop will iterate. 287 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); 288 289 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the 290 /// backedge of the specified loop will execute if it exits via the 291 /// specified block. 292 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L, 293 BasicBlock *ExitingBlock); 294 295 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the 296 /// backedge of the specified loop will execute if its exit condition 297 /// were a conditional branch of ExitCond, TBB, and FBB. 298 BackedgeTakenInfo 299 ComputeBackedgeTakenCountFromExitCond(const Loop *L, 300 Value *ExitCond, 301 BasicBlock *TBB, 302 BasicBlock *FBB); 303 304 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of 305 /// times the backedge of the specified loop will execute if its exit 306 /// condition were a conditional branch of the ICmpInst ExitCond, TBB, 307 /// and FBB. 308 BackedgeTakenInfo 309 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L, 310 ICmpInst *ExitCond, 311 BasicBlock *TBB, 312 BasicBlock *FBB); 313 314 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition 315 /// of 'icmp op load X, cst', try to see if we can compute the 316 /// backedge-taken count. 317 BackedgeTakenInfo 318 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, 319 Constant *RHS, 320 const Loop *L, 321 ICmpInst::Predicate p); 322 323 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute 324 /// a constant number of times (the condition evolves only from constants), 325 /// try to evaluate a few iterations of the loop until we get the exit 326 /// condition gets a value of ExitWhen (true or false). If we cannot 327 /// evaluate the backedge-taken count of the loop, return CouldNotCompute. 328 const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L, 329 Value *Cond, 330 bool ExitWhen); 331 332 /// HowFarToZero - Return the number of times a backedge comparing the 333 /// specified value to zero will execute. If not computable, return 334 /// CouldNotCompute. 335 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L); 336 337 /// HowFarToNonZero - Return the number of times a backedge checking the 338 /// specified value for nonzero will execute. If not computable, return 339 /// CouldNotCompute. 340 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L); 341 342 /// HowManyLessThans - Return the number of times a backedge containing the 343 /// specified less-than comparison will execute. If not computable, return 344 /// CouldNotCompute. isSigned specifies whether the less-than is signed. 345 BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, 346 const Loop *L, bool isSigned); 347 348 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB 349 /// (which may not be an immediate predecessor) which has exactly one 350 /// successor from which BB is reachable, or null if no such block is 351 /// found. 352 std::pair<BasicBlock *, BasicBlock *> 353 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); 354 355 /// isImpliedCond - Test whether the condition described by Pred, LHS, 356 /// and RHS is true whenever the given Cond value evaluates to true. 357 bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred, 358 const SCEV *LHS, const SCEV *RHS, 359 bool Inverse); 360 361 /// isImpliedCondOperands - Test whether the condition described by Pred, 362 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS, 363 /// and FoundRHS is true. 364 bool isImpliedCondOperands(ICmpInst::Predicate Pred, 365 const SCEV *LHS, const SCEV *RHS, 366 const SCEV *FoundLHS, const SCEV *FoundRHS); 367 368 /// isImpliedCondOperandsHelper - Test whether the condition described by 369 /// Pred, LHS, and RHS is true whenever the condition described by Pred, 370 /// FoundLHS, and FoundRHS is true. 371 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, 372 const SCEV *LHS, const SCEV *RHS, 373 const SCEV *FoundLHS, const SCEV *FoundRHS); 374 375 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is 376 /// in the header of its containing loop, we know the loop executes a 377 /// constant number of times, and the PHI node is just a recurrence 378 /// involving constants, fold it. 379 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, 380 const Loop *L); 381 382 /// isKnownPredicateWithRanges - Test if the given expression is known to 383 /// satisfy the condition described by Pred and the known constant ranges 384 /// of LHS and RHS. 385 /// 386 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred, 387 const SCEV *LHS, const SCEV *RHS); 388 389 public: 390 static char ID; // Pass identification, replacement for typeid 391 ScalarEvolution(); 392 393 LLVMContext &getContext() const { return F->getContext(); } 394 395 /// isSCEVable - Test if values of the given type are analyzable within 396 /// the SCEV framework. This primarily includes integer types, and it 397 /// can optionally include pointer types if the ScalarEvolution class 398 /// has access to target-specific information. 399 bool isSCEVable(const Type *Ty) const; 400 401 /// getTypeSizeInBits - Return the size in bits of the specified type, 402 /// for which isSCEVable must return true. 403 uint64_t getTypeSizeInBits(const Type *Ty) const; 404 405 /// getEffectiveSCEVType - Return a type with the same bitwidth as 406 /// the given type and which represents how SCEV will treat the given 407 /// type, for which isSCEVable must return true. For pointer types, 408 /// this is the pointer-sized integer type. 409 const Type *getEffectiveSCEVType(const Type *Ty) const; 410 411 /// getSCEV - Return a SCEV expression for the full generality of the 412 /// specified expression. 413 const SCEV *getSCEV(Value *V); 414 415 const SCEV *getConstant(ConstantInt *V); 416 const SCEV *getConstant(const APInt& Val); 417 const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false); 418 const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty); 419 const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty); 420 const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty); 421 const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty); 422 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops, 423 bool HasNUW = false, bool HasNSW = false); 424 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS, 425 bool HasNUW = false, bool HasNSW = false) { 426 SmallVector<const SCEV *, 2> Ops; 427 Ops.push_back(LHS); 428 Ops.push_back(RHS); 429 return getAddExpr(Ops, HasNUW, HasNSW); 430 } 431 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, 432 const SCEV *Op2, 433 bool HasNUW = false, bool HasNSW = false) { 434 SmallVector<const SCEV *, 3> Ops; 435 Ops.push_back(Op0); 436 Ops.push_back(Op1); 437 Ops.push_back(Op2); 438 return getAddExpr(Ops, HasNUW, HasNSW); 439 } 440 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops, 441 bool HasNUW = false, bool HasNSW = false); 442 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS, 443 bool HasNUW = false, bool HasNSW = false) { 444 SmallVector<const SCEV *, 2> Ops; 445 Ops.push_back(LHS); 446 Ops.push_back(RHS); 447 return getMulExpr(Ops, HasNUW, HasNSW); 448 } 449 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS); 450 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, 451 const Loop *L, 452 bool HasNUW = false, bool HasNSW = false); 453 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands, 454 const Loop *L, 455 bool HasNUW = false, bool HasNSW = false); 456 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands, 457 const Loop *L, 458 bool HasNUW = false, bool HasNSW = false) { 459 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end()); 460 return getAddRecExpr(NewOp, L, HasNUW, HasNSW); 461 } 462 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS); 463 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 464 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS); 465 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands); 466 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS); 467 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS); 468 const SCEV *getUnknown(Value *V); 469 const SCEV *getCouldNotCompute(); 470 471 /// getSizeOfExpr - Return an expression for sizeof on the given type. 472 /// 473 const SCEV *getSizeOfExpr(const Type *AllocTy); 474 475 /// getAlignOfExpr - Return an expression for alignof on the given type. 476 /// 477 const SCEV *getAlignOfExpr(const Type *AllocTy); 478 479 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 480 /// 481 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo); 482 483 /// getOffsetOfExpr - Return an expression for offsetof on the given field. 484 /// 485 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo); 486 487 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 488 /// 489 const SCEV *getNegativeSCEV(const SCEV *V); 490 491 /// getNotSCEV - Return the SCEV object corresponding to ~V. 492 /// 493 const SCEV *getNotSCEV(const SCEV *V); 494 495 /// getMinusSCEV - Return LHS-RHS. 496 /// 497 const SCEV *getMinusSCEV(const SCEV *LHS, 498 const SCEV *RHS); 499 500 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 501 /// of the input value to the specified type. If the type must be 502 /// extended, it is zero extended. 503 const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty); 504 505 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 506 /// of the input value to the specified type. If the type must be 507 /// extended, it is sign extended. 508 const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty); 509 510 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of 511 /// the input value to the specified type. If the type must be extended, 512 /// it is zero extended. The conversion must not be narrowing. 513 const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty); 514 515 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of 516 /// the input value to the specified type. If the type must be extended, 517 /// it is sign extended. The conversion must not be narrowing. 518 const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty); 519 520 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of 521 /// the input value to the specified type. If the type must be extended, 522 /// it is extended with unspecified bits. The conversion must not be 523 /// narrowing. 524 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty); 525 526 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the 527 /// input value to the specified type. The conversion must not be 528 /// widening. 529 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty); 530 531 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of 532 /// the types using zero-extension, and then perform a umax operation 533 /// with them. 534 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, 535 const SCEV *RHS); 536 537 /// getUMinFromMismatchedTypes - Promote the operands to the wider of 538 /// the types using zero-extension, and then perform a umin operation 539 /// with them. 540 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, 541 const SCEV *RHS); 542 543 /// getSCEVAtScope - Return a SCEV expression for the specified value 544 /// at the specified scope in the program. The L value specifies a loop 545 /// nest to evaluate the expression at, where null is the top-level or a 546 /// specified loop is immediately inside of the loop. 547 /// 548 /// This method can be used to compute the exit value for a variable defined 549 /// in a loop by querying what the value will hold in the parent loop. 550 /// 551 /// In the case that a relevant loop exit value cannot be computed, the 552 /// original value V is returned. 553 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L); 554 555 /// getSCEVAtScope - This is a convenience function which does 556 /// getSCEVAtScope(getSCEV(V), L). 557 const SCEV *getSCEVAtScope(Value *V, const Loop *L); 558 559 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected 560 /// by a conditional between LHS and RHS. This is used to help avoid max 561 /// expressions in loop trip counts, and to eliminate casts. 562 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 563 const SCEV *LHS, const SCEV *RHS); 564 565 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is 566 /// protected by a conditional between LHS and RHS. This is used to 567 /// to eliminate casts. 568 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 569 const SCEV *LHS, const SCEV *RHS); 570 571 /// getBackedgeTakenCount - If the specified loop has a predictable 572 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 573 /// object. The backedge-taken count is the number of times the loop header 574 /// will be branched to from within the loop. This is one less than the 575 /// trip count of the loop, since it doesn't count the first iteration, 576 /// when the header is branched to from outside the loop. 577 /// 578 /// Note that it is not valid to call this method on a loop without a 579 /// loop-invariant backedge-taken count (see 580 /// hasLoopInvariantBackedgeTakenCount). 581 /// 582 const SCEV *getBackedgeTakenCount(const Loop *L); 583 584 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except 585 /// return the least SCEV value that is known never to be less than the 586 /// actual backedge taken count. 587 const SCEV *getMaxBackedgeTakenCount(const Loop *L); 588 589 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 590 /// has an analyzable loop-invariant backedge-taken count. 591 bool hasLoopInvariantBackedgeTakenCount(const Loop *L); 592 593 /// forgetLoop - This method should be called by the client when it has 594 /// changed a loop in a way that may effect ScalarEvolution's ability to 595 /// compute a trip count, or if the loop is deleted. 596 void forgetLoop(const Loop *L); 597 598 /// forgetValue - This method should be called by the client when it has 599 /// changed a value in a way that may effect its value, or which may 600 /// disconnect it from a def-use chain linking it to a loop. 601 void forgetValue(Value *V); 602 603 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S 604 /// is guaranteed to end in (at every loop iteration). It is, at the same 605 /// time, the minimum number of times S is divisible by 2. For example, 606 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the 607 /// bitwidth of S. 608 uint32_t GetMinTrailingZeros(const SCEV *S); 609 610 /// getUnsignedRange - Determine the unsigned range for a particular SCEV. 611 /// 612 ConstantRange getUnsignedRange(const SCEV *S); 613 614 /// getSignedRange - Determine the signed range for a particular SCEV. 615 /// 616 ConstantRange getSignedRange(const SCEV *S); 617 618 /// isKnownNegative - Test if the given expression is known to be negative. 619 /// 620 bool isKnownNegative(const SCEV *S); 621 622 /// isKnownPositive - Test if the given expression is known to be positive. 623 /// 624 bool isKnownPositive(const SCEV *S); 625 626 /// isKnownNonNegative - Test if the given expression is known to be 627 /// non-negative. 628 /// 629 bool isKnownNonNegative(const SCEV *S); 630 631 /// isKnownNonPositive - Test if the given expression is known to be 632 /// non-positive. 633 /// 634 bool isKnownNonPositive(const SCEV *S); 635 636 /// isKnownNonZero - Test if the given expression is known to be 637 /// non-zero. 638 /// 639 bool isKnownNonZero(const SCEV *S); 640 641 /// isKnownPredicate - Test if the given expression is known to satisfy 642 /// the condition described by Pred, LHS, and RHS. 643 /// 644 bool isKnownPredicate(ICmpInst::Predicate Pred, 645 const SCEV *LHS, const SCEV *RHS); 646 647 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with 648 /// predicate Pred. Return true iff any changes were made. If the 649 /// operands are provably equal or inequal, LHS and RHS are set to 650 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE. 651 /// 652 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, 653 const SCEV *&LHS, 654 const SCEV *&RHS); 655 656 virtual bool runOnFunction(Function &F); 657 virtual void releaseMemory(); 658 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 659 virtual void print(raw_ostream &OS, const Module* = 0) const; 660 661 private: 662 FoldingSet<SCEV> UniqueSCEVs; 663 BumpPtrAllocator SCEVAllocator; 664 665 /// FirstUnknown - The head of a linked list of all SCEVUnknown 666 /// values that have been allocated. This is used by releaseMemory 667 /// to locate them all and call their destructors. 668 SCEVUnknown *FirstUnknown; 669 }; 670} 671 672#endif 673