1 //===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
16 // This analysis is primarily useful for induction variable substitution and
17 // strength reduction.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
22 #define LLVM_ANALYSIS_SCALAREVOLUTION_H
24 #include "llvm/Pass.h"
25 #include "llvm/Instructions.h"
26 #include "llvm/Function.h"
27 #include "llvm/Operator.h"
28 #include "llvm/Support/DataTypes.h"
29 #include "llvm/Support/ValueHandle.h"
30 #include "llvm/Support/Allocator.h"
31 #include "llvm/Support/ConstantRange.h"
32 #include "llvm/ADT/FoldingSet.h"
33 #include "llvm/ADT/DenseSet.h"
42 class ScalarEvolution;
44 class TargetLibraryInfo;
51 template<> struct FoldingSetTrait<SCEV>;
53 /// SCEV - This class represents an analyzed expression in the program. These
54 /// are opaque objects that the client is not allowed to do much with
57 class SCEV : public FoldingSetNode {
58 friend struct FoldingSetTrait<SCEV>;
60 /// FastID - A reference to an Interned FoldingSetNodeID for this node.
61 /// The ScalarEvolution's BumpPtrAllocator holds the data.
62 FoldingSetNodeIDRef FastID;
64 // The SCEV baseclass this node corresponds to
65 const unsigned short SCEVType;
68 /// SubclassData - This field is initialized to zero and may be used in
69 /// subclasses to store miscellaneous information.
70 unsigned short SubclassData;
73 SCEV(const SCEV &) LLVM_DELETED_FUNCTION;
74 void operator=(const SCEV &) LLVM_DELETED_FUNCTION;
77 /// NoWrapFlags are bitfield indices into SubclassData.
79 /// Add and Mul expressions may have no-unsigned-wrap <NUW> or
80 /// no-signed-wrap <NSW> properties, which are derived from the IR
81 /// operator. NSW is a misnomer that we use to mean no signed overflow or
84 /// AddRec expression may have a no-self-wraparound <NW> property if the
85 /// result can never reach the start value. This property is independent of
86 /// the actual start value and step direction. Self-wraparound is defined
87 /// purely in terms of the recurrence's loop, step size, and
88 /// bitwidth. Formally, a recurrence with no self-wraparound satisfies:
89 /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth).
91 /// Note that NUW and NSW are also valid properties of a recurrence, and
92 /// either implies NW. For convenience, NW will be set for a recurrence
93 /// whenever either NUW or NSW are set.
94 enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee.
95 FlagNW = (1 << 0), // No self-wrap.
96 FlagNUW = (1 << 1), // No unsigned wrap.
97 FlagNSW = (1 << 2), // No signed wrap.
98 NoWrapMask = (1 << 3) -1 };
100 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) :
101 FastID(ID), SCEVType(SCEVTy), SubclassData(0) {}
103 unsigned getSCEVType() const { return SCEVType; }
105 /// getType - Return the LLVM type of this SCEV expression.
107 Type *getType() const;
109 /// isZero - Return true if the expression is a constant zero.
113 /// isOne - Return true if the expression is a constant one.
117 /// isAllOnesValue - Return true if the expression is a constant
120 bool isAllOnesValue() const;
122 /// isNonConstantNegative - Return true if the specified scev is negated,
123 /// but not a constant.
124 bool isNonConstantNegative() const;
126 /// print - Print out the internal representation of this scalar to the
127 /// specified stream. This should really only be used for debugging
129 void print(raw_ostream &OS) const;
131 /// dump - This method is used for debugging.
136 // Specialize FoldingSetTrait for SCEV to avoid needing to compute
137 // temporary FoldingSetNodeID values.
138 template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> {
139 static void Profile(const SCEV &X, FoldingSetNodeID& ID) {
142 static bool Equals(const SCEV &X, const FoldingSetNodeID &ID,
143 unsigned IDHash, FoldingSetNodeID &TempID) {
144 return ID == X.FastID;
146 static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) {
147 return X.FastID.ComputeHash();
151 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
156 /// SCEVCouldNotCompute - An object of this class is returned by queries that
157 /// could not be answered. For example, if you ask for the number of
158 /// iterations of a linked-list traversal loop, you will get one of these.
159 /// None of the standard SCEV operations are valid on this class, it is just a
161 struct SCEVCouldNotCompute : public SCEV {
162 SCEVCouldNotCompute();
164 /// Methods for support type inquiry through isa, cast, and dyn_cast:
165 static bool classof(const SCEV *S);
168 /// ScalarEvolution - This class is the main scalar evolution driver. Because
169 /// client code (intentionally) can't do much with the SCEV objects directly,
170 /// they must ask this class for services.
172 class ScalarEvolution : public FunctionPass {
174 /// LoopDisposition - An enum describing the relationship between a
176 enum LoopDisposition {
177 LoopVariant, ///< The SCEV is loop-variant (unknown).
178 LoopInvariant, ///< The SCEV is loop-invariant.
179 LoopComputable ///< The SCEV varies predictably with the loop.
182 /// BlockDisposition - An enum describing the relationship between a
183 /// SCEV and a basic block.
184 enum BlockDisposition {
185 DoesNotDominateBlock, ///< The SCEV does not dominate the block.
186 DominatesBlock, ///< The SCEV dominates the block.
187 ProperlyDominatesBlock ///< The SCEV properly dominates the block.
190 /// Convenient NoWrapFlags manipulation that hides enum casts and is
191 /// visible in the ScalarEvolution name space.
192 static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) {
193 return (SCEV::NoWrapFlags)(Flags & Mask);
195 static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags,
196 SCEV::NoWrapFlags OnFlags) {
197 return (SCEV::NoWrapFlags)(Flags | OnFlags);
199 static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags,
200 SCEV::NoWrapFlags OffFlags) {
201 return (SCEV::NoWrapFlags)(Flags & ~OffFlags);
205 /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
206 /// notified whenever a Value is deleted.
207 class SCEVCallbackVH : public CallbackVH {
209 virtual void deleted();
210 virtual void allUsesReplacedWith(Value *New);
212 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0);
215 friend class SCEVCallbackVH;
216 friend class SCEVExpander;
217 friend class SCEVUnknown;
219 /// F - The function we are analyzing.
223 /// LI - The loop information for the function we are currently analyzing.
227 /// TD - The target data information for the target we are targeting.
231 /// TLI - The target library information for the target we are targeting.
233 TargetLibraryInfo *TLI;
235 /// DT - The dominator tree.
239 /// CouldNotCompute - This SCEV is used to represent unknown trip
240 /// counts and things.
241 SCEVCouldNotCompute CouldNotCompute;
243 /// ValueExprMapType - The typedef for ValueExprMap.
245 typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> >
248 /// ValueExprMap - This is a cache of the values we have analyzed so far.
250 ValueExprMapType ValueExprMap;
252 /// Mark predicate values currently being processed by isImpliedCond.
253 DenseSet<Value*> PendingLoopPredicates;
255 /// ExitLimit - Information about the number of loop iterations for
256 /// which a loop exit's branch condition evaluates to the not-taken path.
257 /// This is a temporary pair of exact and max expressions that are
258 /// eventually summarized in ExitNotTakenInfo and BackedgeTakenInfo.
263 /*implicit*/ ExitLimit(const SCEV *E) : Exact(E), Max(E) {}
265 ExitLimit(const SCEV *E, const SCEV *M) : Exact(E), Max(M) {}
267 /// hasAnyInfo - Test whether this ExitLimit contains any computed
268 /// information, or whether it's all SCEVCouldNotCompute values.
269 bool hasAnyInfo() const {
270 return !isa<SCEVCouldNotCompute>(Exact) ||
271 !isa<SCEVCouldNotCompute>(Max);
275 /// ExitNotTakenInfo - Information about the number of times a particular
276 /// loop exit may be reached before exiting the loop.
277 struct ExitNotTakenInfo {
278 AssertingVH<BasicBlock> ExitingBlock;
279 const SCEV *ExactNotTaken;
280 PointerIntPair<ExitNotTakenInfo*, 1> NextExit;
282 ExitNotTakenInfo() : ExitingBlock(0), ExactNotTaken(0) {}
284 /// isCompleteList - Return true if all loop exits are computable.
285 bool isCompleteList() const {
286 return NextExit.getInt() == 0;
289 void setIncomplete() { NextExit.setInt(1); }
291 /// getNextExit - Return a pointer to the next exit's not-taken info.
292 ExitNotTakenInfo *getNextExit() const {
293 return NextExit.getPointer();
296 void setNextExit(ExitNotTakenInfo *ENT) { NextExit.setPointer(ENT); }
299 /// BackedgeTakenInfo - Information about the backedge-taken count
300 /// of a loop. This currently includes an exact count and a maximum count.
302 class BackedgeTakenInfo {
303 /// ExitNotTaken - A list of computable exits and their not-taken counts.
304 /// Loops almost never have more than one computable exit.
305 ExitNotTakenInfo ExitNotTaken;
307 /// Max - An expression indicating the least maximum backedge-taken
308 /// count of the loop that is known, or a SCEVCouldNotCompute.
312 BackedgeTakenInfo() : Max(0) {}
314 /// Initialize BackedgeTakenInfo from a list of exact exit counts.
316 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
317 bool Complete, const SCEV *MaxCount);
319 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
320 /// computed information, or whether it's all SCEVCouldNotCompute
322 bool hasAnyInfo() const {
323 return ExitNotTaken.ExitingBlock || !isa<SCEVCouldNotCompute>(Max);
326 /// getExact - Return an expression indicating the exact backedge-taken
327 /// count of the loop if it is known, or SCEVCouldNotCompute
328 /// otherwise. This is the number of times the loop header can be
329 /// guaranteed to execute, minus one.
330 const SCEV *getExact(ScalarEvolution *SE) const;
332 /// getExact - Return the number of times this loop exit may fall through
333 /// to the back edge, or SCEVCouldNotCompute. The loop is guaranteed not
334 /// to exit via this block before this number of iterations, but may exit
335 /// via another block.
336 const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const;
338 /// getMax - Get the max backedge taken count for the loop.
339 const SCEV *getMax(ScalarEvolution *SE) const;
341 /// clear - Invalidate this result and free associated memory.
345 /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
346 /// this function as they are computed.
347 DenseMap<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts;
349 /// ConstantEvolutionLoopExitValue - This map contains entries for all of
350 /// the PHI instructions that we attempt to compute constant evolutions for.
351 /// This allows us to avoid potentially expensive recomputation of these
352 /// properties. An instruction maps to null if we are unable to compute its
354 DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
356 /// ValuesAtScopes - This map contains entries for all the expressions
357 /// that we attempt to compute getSCEVAtScope information for, which can
358 /// be expensive in extreme cases.
359 DenseMap<const SCEV *,
360 std::map<const Loop *, const SCEV *> > ValuesAtScopes;
362 /// LoopDispositions - Memoized computeLoopDisposition results.
363 DenseMap<const SCEV *,
364 std::map<const Loop *, LoopDisposition> > LoopDispositions;
366 /// computeLoopDisposition - Compute a LoopDisposition value.
367 LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
369 /// BlockDispositions - Memoized computeBlockDisposition results.
370 DenseMap<const SCEV *,
371 std::map<const BasicBlock *, BlockDisposition> > BlockDispositions;
373 /// computeBlockDisposition - Compute a BlockDisposition value.
374 BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB);
376 /// UnsignedRanges - Memoized results from getUnsignedRange
377 DenseMap<const SCEV *, ConstantRange> UnsignedRanges;
379 /// SignedRanges - Memoized results from getSignedRange
380 DenseMap<const SCEV *, ConstantRange> SignedRanges;
382 /// setUnsignedRange - Set the memoized unsigned range for the given SCEV.
383 const ConstantRange &setUnsignedRange(const SCEV *S,
384 const ConstantRange &CR) {
385 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
386 UnsignedRanges.insert(std::make_pair(S, CR));
388 Pair.first->second = CR;
389 return Pair.first->second;
392 /// setUnsignedRange - Set the memoized signed range for the given SCEV.
393 const ConstantRange &setSignedRange(const SCEV *S,
394 const ConstantRange &CR) {
395 std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
396 SignedRanges.insert(std::make_pair(S, CR));
398 Pair.first->second = CR;
399 return Pair.first->second;
402 /// createSCEV - We know that there is no SCEV for the specified value.
403 /// Analyze the expression.
404 const SCEV *createSCEV(Value *V);
406 /// createNodeForPHI - Provide the special handling we need to analyze PHI
408 const SCEV *createNodeForPHI(PHINode *PN);
410 /// createNodeForGEP - Provide the special handling we need to analyze GEP
412 const SCEV *createNodeForGEP(GEPOperator *GEP);
414 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called
415 /// at most once for each SCEV+Loop pair.
417 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L);
419 /// ForgetSymbolicValue - This looks up computed SCEV values for all
420 /// instructions that depend on the given instruction and removes them from
421 /// the ValueExprMap map if they reference SymName. This is used during PHI
423 void ForgetSymbolicName(Instruction *I, const SCEV *SymName);
425 /// getBECount - Subtract the end and start values and divide by the step,
426 /// rounding up, to get the number of times the backedge is executed. Return
427 /// CouldNotCompute if an intermediate computation overflows.
428 const SCEV *getBECount(const SCEV *Start,
433 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given
434 /// loop, lazily computing new values if the loop hasn't been analyzed
436 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
438 /// ComputeBackedgeTakenCount - Compute the number of times the specified
439 /// loop will iterate.
440 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L);
442 /// ComputeExitLimit - Compute the number of times the backedge of the
443 /// specified loop will execute if it exits via the specified block.
444 ExitLimit ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock);
446 /// ComputeExitLimitFromCond - Compute the number of times the backedge of
447 /// the specified loop will execute if its exit condition were a conditional
448 /// branch of ExitCond, TBB, and FBB.
449 ExitLimit ComputeExitLimitFromCond(const Loop *L,
454 /// ComputeExitLimitFromICmp - Compute the number of times the backedge of
455 /// the specified loop will execute if its exit condition were a conditional
456 /// branch of the ICmpInst ExitCond, TBB, and FBB.
457 ExitLimit ComputeExitLimitFromICmp(const Loop *L,
462 /// ComputeLoadConstantCompareExitLimit - Given an exit condition
463 /// of 'icmp op load X, cst', try to see if we can compute the
464 /// backedge-taken count.
465 ExitLimit ComputeLoadConstantCompareExitLimit(LoadInst *LI,
468 ICmpInst::Predicate p);
470 /// ComputeExitCountExhaustively - If the loop is known to execute a
471 /// constant number of times (the condition evolves only from constants),
472 /// try to evaluate a few iterations of the loop until we get the exit
473 /// condition gets a value of ExitWhen (true or false). If we cannot
474 /// evaluate the exit count of the loop, return CouldNotCompute.
475 const SCEV *ComputeExitCountExhaustively(const Loop *L,
479 /// HowFarToZero - Return the number of times an exit condition comparing
480 /// the specified value to zero will execute. If not computable, return
482 ExitLimit HowFarToZero(const SCEV *V, const Loop *L);
484 /// HowFarToNonZero - Return the number of times an exit condition checking
485 /// the specified value for nonzero will execute. If not computable, return
487 ExitLimit HowFarToNonZero(const SCEV *V, const Loop *L);
489 /// HowManyLessThans - Return the number of times an exit condition
490 /// containing the specified less-than comparison will execute. If not
491 /// computable, return CouldNotCompute. isSigned specifies whether the
492 /// less-than is signed.
493 ExitLimit HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
494 const Loop *L, bool isSigned);
496 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
497 /// (which may not be an immediate predecessor) which has exactly one
498 /// successor from which BB is reachable, or null if no such block is
500 std::pair<BasicBlock *, BasicBlock *>
501 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
503 /// isImpliedCond - Test whether the condition described by Pred, LHS, and
504 /// RHS is true whenever the given FoundCondValue value evaluates to true.
505 bool isImpliedCond(ICmpInst::Predicate Pred,
506 const SCEV *LHS, const SCEV *RHS,
507 Value *FoundCondValue,
510 /// isImpliedCondOperands - Test whether the condition described by Pred,
511 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
512 /// and FoundRHS is true.
513 bool isImpliedCondOperands(ICmpInst::Predicate Pred,
514 const SCEV *LHS, const SCEV *RHS,
515 const SCEV *FoundLHS, const SCEV *FoundRHS);
517 /// isImpliedCondOperandsHelper - Test whether the condition described by
518 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
519 /// FoundLHS, and FoundRHS is true.
520 bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
521 const SCEV *LHS, const SCEV *RHS,
522 const SCEV *FoundLHS,
523 const SCEV *FoundRHS);
525 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
526 /// in the header of its containing loop, we know the loop executes a
527 /// constant number of times, and the PHI node is just a recurrence
528 /// involving constants, fold it.
529 Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
532 /// isKnownPredicateWithRanges - Test if the given expression is known to
533 /// satisfy the condition described by Pred and the known constant ranges
536 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
537 const SCEV *LHS, const SCEV *RHS);
539 /// forgetMemoizedResults - Drop memoized information computed for S.
540 void forgetMemoizedResults(const SCEV *S);
543 static char ID; // Pass identification, replacement for typeid
546 LLVMContext &getContext() const { return F->getContext(); }
548 /// isSCEVable - Test if values of the given type are analyzable within
549 /// the SCEV framework. This primarily includes integer types, and it
550 /// can optionally include pointer types if the ScalarEvolution class
551 /// has access to target-specific information.
552 bool isSCEVable(Type *Ty) const;
554 /// getTypeSizeInBits - Return the size in bits of the specified type,
555 /// for which isSCEVable must return true.
556 uint64_t getTypeSizeInBits(Type *Ty) const;
558 /// getEffectiveSCEVType - Return a type with the same bitwidth as
559 /// the given type and which represents how SCEV will treat the given
560 /// type, for which isSCEVable must return true. For pointer types,
561 /// this is the pointer-sized integer type.
562 Type *getEffectiveSCEVType(Type *Ty) const;
564 /// getSCEV - Return a SCEV expression for the full generality of the
565 /// specified expression.
566 const SCEV *getSCEV(Value *V);
568 const SCEV *getConstant(ConstantInt *V);
569 const SCEV *getConstant(const APInt& Val);
570 const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false);
571 const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty);
572 const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty);
573 const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty);
574 const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty);
575 const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
576 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
577 const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS,
578 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
579 SmallVector<const SCEV *, 2> Ops;
582 return getAddExpr(Ops, Flags);
584 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
585 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
586 SmallVector<const SCEV *, 3> Ops;
590 return getAddExpr(Ops, Flags);
592 const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
593 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
594 const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS,
595 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap)
597 SmallVector<const SCEV *, 2> Ops;
600 return getMulExpr(Ops, Flags);
602 const SCEV *getMulExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
603 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
604 SmallVector<const SCEV *, 3> Ops;
608 return getMulExpr(Ops, Flags);
610 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
611 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
612 const Loop *L, SCEV::NoWrapFlags Flags);
613 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
614 const Loop *L, SCEV::NoWrapFlags Flags);
615 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
616 const Loop *L, SCEV::NoWrapFlags Flags) {
617 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
618 return getAddRecExpr(NewOp, L, Flags);
620 const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
621 const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
622 const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS);
623 const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
624 const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS);
625 const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS);
626 const SCEV *getUnknown(Value *V);
627 const SCEV *getCouldNotCompute();
629 /// getSizeOfExpr - Return an expression for sizeof on the given type.
631 const SCEV *getSizeOfExpr(Type *AllocTy);
633 /// getAlignOfExpr - Return an expression for alignof on the given type.
635 const SCEV *getAlignOfExpr(Type *AllocTy);
637 /// getOffsetOfExpr - Return an expression for offsetof on the given field.
639 const SCEV *getOffsetOfExpr(StructType *STy, unsigned FieldNo);
641 /// getOffsetOfExpr - Return an expression for offsetof on the given field.
643 const SCEV *getOffsetOfExpr(Type *CTy, Constant *FieldNo);
645 /// getNegativeSCEV - Return the SCEV object corresponding to -V.
647 const SCEV *getNegativeSCEV(const SCEV *V);
649 /// getNotSCEV - Return the SCEV object corresponding to ~V.
651 const SCEV *getNotSCEV(const SCEV *V);
653 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
654 const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
655 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
657 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
658 /// of the input value to the specified type. If the type must be
659 /// extended, it is zero extended.
660 const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty);
662 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion
663 /// of the input value to the specified type. If the type must be
664 /// extended, it is sign extended.
665 const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty);
667 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of
668 /// the input value to the specified type. If the type must be extended,
669 /// it is zero extended. The conversion must not be narrowing.
670 const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty);
672 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of
673 /// the input value to the specified type. If the type must be extended,
674 /// it is sign extended. The conversion must not be narrowing.
675 const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty);
677 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
678 /// the input value to the specified type. If the type must be extended,
679 /// it is extended with unspecified bits. The conversion must not be
681 const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty);
683 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
684 /// input value to the specified type. The conversion must not be
686 const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty);
688 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
689 /// the types using zero-extension, and then perform a umax operation
691 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS,
694 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
695 /// the types using zero-extension, and then perform a umin operation
697 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS,
700 /// getPointerBase - Transitively follow the chain of pointer-type operands
701 /// until reaching a SCEV that does not have a single pointer operand. This
702 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
703 /// but corner cases do exist.
704 const SCEV *getPointerBase(const SCEV *V);
706 /// getSCEVAtScope - Return a SCEV expression for the specified value
707 /// at the specified scope in the program. The L value specifies a loop
708 /// nest to evaluate the expression at, where null is the top-level or a
709 /// specified loop is immediately inside of the loop.
711 /// This method can be used to compute the exit value for a variable defined
712 /// in a loop by querying what the value will hold in the parent loop.
714 /// In the case that a relevant loop exit value cannot be computed, the
715 /// original value V is returned.
716 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
718 /// getSCEVAtScope - This is a convenience function which does
719 /// getSCEVAtScope(getSCEV(V), L).
720 const SCEV *getSCEVAtScope(Value *V, const Loop *L);
722 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
723 /// by a conditional between LHS and RHS. This is used to help avoid max
724 /// expressions in loop trip counts, and to eliminate casts.
725 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
726 const SCEV *LHS, const SCEV *RHS);
728 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
729 /// protected by a conditional between LHS and RHS. This is used to
730 /// to eliminate casts.
731 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
732 const SCEV *LHS, const SCEV *RHS);
734 /// getSmallConstantTripCount - Returns the maximum trip count of this loop
735 /// as a normal unsigned value. Returns 0 if the trip count is unknown or
736 /// not constant. This "trip count" assumes that control exits via
737 /// ExitingBlock. More precisely, it is the number of times that control may
738 /// reach ExitingBlock before taking the branch. For loops with multiple
739 /// exits, it may not be the number times that the loop header executes if
740 /// the loop exits prematurely via another branch.
741 unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitingBlock);
743 /// getSmallConstantTripMultiple - Returns the largest constant divisor of
744 /// the trip count of this loop as a normal unsigned value, if
745 /// possible. This means that the actual trip count is always a multiple of
746 /// the returned value (don't forget the trip count could very well be zero
747 /// as well!). As explained in the comments for getSmallConstantTripCount,
748 /// this assumes that control exits the loop via ExitingBlock.
749 unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitingBlock);
751 // getExitCount - Get the expression for the number of loop iterations for
752 // which this loop is guaranteed not to exit via ExitingBlock. Otherwise
753 // return SCEVCouldNotCompute.
754 const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock);
756 /// getBackedgeTakenCount - If the specified loop has a predictable
757 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
758 /// object. The backedge-taken count is the number of times the loop header
759 /// will be branched to from within the loop. This is one less than the
760 /// trip count of the loop, since it doesn't count the first iteration,
761 /// when the header is branched to from outside the loop.
763 /// Note that it is not valid to call this method on a loop without a
764 /// loop-invariant backedge-taken count (see
765 /// hasLoopInvariantBackedgeTakenCount).
767 const SCEV *getBackedgeTakenCount(const Loop *L);
769 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
770 /// return the least SCEV value that is known never to be less than the
771 /// actual backedge taken count.
772 const SCEV *getMaxBackedgeTakenCount(const Loop *L);
774 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
775 /// has an analyzable loop-invariant backedge-taken count.
776 bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
778 /// forgetLoop - This method should be called by the client when it has
779 /// changed a loop in a way that may effect ScalarEvolution's ability to
780 /// compute a trip count, or if the loop is deleted.
781 void forgetLoop(const Loop *L);
783 /// forgetValue - This method should be called by the client when it has
784 /// changed a value in a way that may effect its value, or which may
785 /// disconnect it from a def-use chain linking it to a loop.
786 void forgetValue(Value *V);
788 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S
789 /// is guaranteed to end in (at every loop iteration). It is, at the same
790 /// time, the minimum number of times S is divisible by 2. For example,
791 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the
793 uint32_t GetMinTrailingZeros(const SCEV *S);
795 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
797 ConstantRange getUnsignedRange(const SCEV *S);
799 /// getSignedRange - Determine the signed range for a particular SCEV.
801 ConstantRange getSignedRange(const SCEV *S);
803 /// isKnownNegative - Test if the given expression is known to be negative.
805 bool isKnownNegative(const SCEV *S);
807 /// isKnownPositive - Test if the given expression is known to be positive.
809 bool isKnownPositive(const SCEV *S);
811 /// isKnownNonNegative - Test if the given expression is known to be
814 bool isKnownNonNegative(const SCEV *S);
816 /// isKnownNonPositive - Test if the given expression is known to be
819 bool isKnownNonPositive(const SCEV *S);
821 /// isKnownNonZero - Test if the given expression is known to be
824 bool isKnownNonZero(const SCEV *S);
826 /// isKnownPredicate - Test if the given expression is known to satisfy
827 /// the condition described by Pred, LHS, and RHS.
829 bool isKnownPredicate(ICmpInst::Predicate Pred,
830 const SCEV *LHS, const SCEV *RHS);
832 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
833 /// predicate Pred. Return true iff any changes were made. If the
834 /// operands are provably equal or inequal, LHS and RHS are set to
835 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE.
837 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred,
842 /// getLoopDisposition - Return the "disposition" of the given SCEV with
843 /// respect to the given loop.
844 LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L);
846 /// isLoopInvariant - Return true if the value of the given SCEV is
847 /// unchanging in the specified loop.
848 bool isLoopInvariant(const SCEV *S, const Loop *L);
850 /// hasComputableLoopEvolution - Return true if the given SCEV changes value
851 /// in a known way in the specified loop. This property being true implies
852 /// that the value is variant in the loop AND that we can emit an expression
853 /// to compute the value of the expression at any particular loop iteration.
854 bool hasComputableLoopEvolution(const SCEV *S, const Loop *L);
856 /// getLoopDisposition - Return the "disposition" of the given SCEV with
857 /// respect to the given block.
858 BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB);
860 /// dominates - Return true if elements that makes up the given SCEV
861 /// dominate the specified basic block.
862 bool dominates(const SCEV *S, const BasicBlock *BB);
864 /// properlyDominates - Return true if elements that makes up the given SCEV
865 /// properly dominate the specified basic block.
866 bool properlyDominates(const SCEV *S, const BasicBlock *BB);
868 /// hasOperand - Test whether the given SCEV has Op as a direct or
869 /// indirect operand.
870 bool hasOperand(const SCEV *S, const SCEV *Op) const;
872 virtual bool runOnFunction(Function &F);
873 virtual void releaseMemory();
874 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
875 virtual void print(raw_ostream &OS, const Module* = 0) const;
876 virtual void verifyAnalysis() const;
879 FoldingSet<SCEV> UniqueSCEVs;
880 BumpPtrAllocator SCEVAllocator;
882 /// FirstUnknown - The head of a linked list of all SCEVUnknown
883 /// values that have been allocated. This is used by releaseMemory
884 /// to locate them all and call their destructors.
885 SCEVUnknown *FirstUnknown;