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/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"
41 class ScalarEvolution;
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
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;
57 /// AllocationSequenceNumber - This is used as a deterministic tie
58 /// breaker when sorting SCEVs.
59 unsigned AllocationSequenceNumber;
61 // The SCEV baseclass this node corresponds to
62 const unsigned short SCEVType;
65 /// SubclassData - This field is initialized to zero and may be used in
66 /// subclasses to store miscellaneous information.
67 unsigned short SubclassData;
70 SCEV(const SCEV &); // DO NOT IMPLEMENT
71 void operator=(const SCEV &); // DO NOT IMPLEMENT
75 explicit SCEV(const FoldingSetNodeIDRef ID, unsigned num, unsigned SCEVTy) :
76 FastID(ID), AllocationSequenceNumber(num),
77 SCEVType(SCEVTy), SubclassData(0) {}
79 unsigned getSCEVType() const { return SCEVType; }
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;
87 /// Profile - FoldingSet support.
88 void Profile(FoldingSetNodeID& ID) { ID = FastID; }
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;
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;
100 /// getType - Return the LLVM type of this SCEV expression.
102 virtual const Type *getType() const = 0;
104 /// isZero - Return true if the expression is a constant zero.
108 /// isOne - Return true if the expression is a constant one.
112 /// isAllOnesValue - Return true if the expression is a constant
115 bool isAllOnesValue() const;
117 /// hasOperand - Test whether this SCEV has Op as a direct or
118 /// indirect operand.
119 virtual bool hasOperand(const SCEV *Op) const = 0;
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;
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;
129 /// print - Print out the internal representation of this scalar to the
130 /// specified stream. This should really only be used for debugging
132 virtual void print(raw_ostream &OS) const = 0;
134 /// dump - This method is used for debugging.
139 inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
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
149 struct SCEVCouldNotCompute : public SCEV {
150 SCEVCouldNotCompute();
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;
159 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const {
163 virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
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);
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.
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 {
181 virtual void deleted();
182 virtual void allUsesReplacedWith(Value *New);
184 SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0);
187 friend class SCEVCallbackVH;
188 friend class SCEVExpander;
190 /// F - The function we are analyzing.
194 /// LI - The loop information for the function we are currently analyzing.
198 /// TD - The target data information for the target we are targeting.
202 /// DT - The dominator tree.
206 /// CouldNotCompute - This SCEV is used to represent unknown trip
207 /// counts and things.
208 SCEVCouldNotCompute CouldNotCompute;
210 /// Scalars - This is a cache of the scalars we have analyzed so far.
212 std::map<SCEVCallbackVH, const SCEV *> Scalars;
214 /// BackedgeTakenInfo - Information about the backedge-taken count
215 /// of a loop. This currently includes an exact count and a maximum count.
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.
222 /// Max - An expression indicating the least maximum backedge-taken
223 /// count of the loop that is known, or a SCEVCouldNotCompute.
226 /*implicit*/ BackedgeTakenInfo(const SCEV *exact) :
227 Exact(exact), Max(exact) {}
229 BackedgeTakenInfo(const SCEV *exact, const SCEV *max) :
230 Exact(exact), Max(max) {}
232 /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
233 /// computed information, or whether it's all SCEVCouldNotCompute
235 bool hasAnyInfo() const {
236 return !isa<SCEVCouldNotCompute>(Exact) ||
237 !isa<SCEVCouldNotCompute>(Max);
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;
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
250 std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
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;
258 /// createSCEV - We know that there is no SCEV for the specified value.
259 /// Analyze the expression.
260 const SCEV *createSCEV(Value *V);
262 /// createNodeForPHI - Provide the special handling we need to analyze PHI
264 const SCEV *createNodeForPHI(PHINode *PN);
266 /// createNodeForGEP - Provide the special handling we need to analyze GEP
268 const SCEV *createNodeForGEP(GEPOperator *GEP);
270 /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called
271 /// at most once for each SCEV+Loop pair.
273 const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L);
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
279 void ForgetSymbolicName(Instruction *I, const SCEV *SymName);
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,
289 /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given
290 /// loop, lazily computing new values if the loop hasn't been analyzed
292 const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
294 /// ComputeBackedgeTakenCount - Compute the number of times the specified
295 /// loop will iterate.
296 BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L);
298 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the
299 /// backedge of the specified loop will execute if it exits via the
301 BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L,
302 BasicBlock *ExitingBlock);
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.
308 ComputeBackedgeTakenCountFromExitCond(const Loop *L,
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,
318 ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
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.
327 ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
330 ICmpInst::Predicate p);
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,
341 /// HowFarToZero - Return the number of times a backedge comparing the
342 /// specified value to zero will execute. If not computable, return
344 BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L);
346 /// HowFarToNonZero - Return the number of times a backedge checking the
347 /// specified value for nonzero will execute. If not computable, return
349 BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L);
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);
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);
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
365 std::pair<BasicBlock *, BasicBlock *>
366 getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
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,
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);
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);
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,
395 /// isKnownPredicateWithRanges - Test if the given expression is known to
396 /// satisfy the condition described by Pred and the known constant ranges
399 bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
400 const SCEV *LHS, const SCEV *RHS);
403 static char ID; // Pass identification, replacement for typeid
406 LLVMContext &getContext() const { return F->getContext(); }
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;
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;
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;
424 /// getSCEV - Return a SCEV expression for the full generality of the
425 /// specified expression.
426 const SCEV *getSCEV(Value *V);
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;
442 return getAddExpr(Ops, HasNUW, HasNSW);
444 const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1,
446 bool HasNUW = false, bool HasNSW = false) {
447 SmallVector<const SCEV *, 3> Ops;
451 return getAddExpr(Ops, HasNUW, HasNSW);
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;
460 return getMulExpr(Ops, HasNUW, HasNSW);
462 const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
463 const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
465 bool HasNUW = false, bool HasNSW = false);
466 const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
468 bool HasNUW = false, bool HasNSW = false);
469 const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
471 bool HasNUW = false, bool HasNSW = false) {
472 SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
473 return getAddRecExpr(NewOp, L, HasNUW, HasNSW);
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();
484 /// getSizeOfExpr - Return an expression for sizeof on the given type.
486 const SCEV *getSizeOfExpr(const Type *AllocTy);
488 /// getAlignOfExpr - Return an expression for alignof on the given type.
490 const SCEV *getAlignOfExpr(const Type *AllocTy);
492 /// getOffsetOfExpr - Return an expression for offsetof on the given field.
494 const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo);
496 /// getOffsetOfExpr - Return an expression for offsetof on the given field.
498 const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo);
500 /// getNegativeSCEV - Return the SCEV object corresponding to -V.
502 const SCEV *getNegativeSCEV(const SCEV *V);
504 /// getNotSCEV - Return the SCEV object corresponding to ~V.
506 const SCEV *getNotSCEV(const SCEV *V);
508 /// getMinusSCEV - Return LHS-RHS.
510 const SCEV *getMinusSCEV(const SCEV *LHS,
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);
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);
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);
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);
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
537 const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty);
539 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
540 /// input value to the specified type. The conversion must not be
542 const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty);
544 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
545 /// the types using zero-extension, and then perform a umax operation
547 const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS,
550 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
551 /// the types using zero-extension, and then perform a umin operation
553 const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS,
556 /// getSCEVAtScope - Return a SCEV expression for the specified value
557 /// at the specified scope in the program. The L value specifies a loop
558 /// nest to evaluate the expression at, where null is the top-level or a
559 /// specified loop is immediately inside of the loop.
561 /// This method can be used to compute the exit value for a variable defined
562 /// in a loop by querying what the value will hold in the parent loop.
564 /// In the case that a relevant loop exit value cannot be computed, the
565 /// original value V is returned.
566 const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
568 /// getSCEVAtScope - This is a convenience function which does
569 /// getSCEVAtScope(getSCEV(V), L).
570 const SCEV *getSCEVAtScope(Value *V, const Loop *L);
572 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
573 /// by a conditional between LHS and RHS. This is used to help avoid max
574 /// expressions in loop trip counts, and to eliminate casts.
575 bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
576 const SCEV *LHS, const SCEV *RHS);
578 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
579 /// protected by a conditional between LHS and RHS. This is used to
580 /// to eliminate casts.
581 bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
582 const SCEV *LHS, const SCEV *RHS);
584 /// getBackedgeTakenCount - If the specified loop has a predictable
585 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
586 /// object. The backedge-taken count is the number of times the loop header
587 /// will be branched to from within the loop. This is one less than the
588 /// trip count of the loop, since it doesn't count the first iteration,
589 /// when the header is branched to from outside the loop.
591 /// Note that it is not valid to call this method on a loop without a
592 /// loop-invariant backedge-taken count (see
593 /// hasLoopInvariantBackedgeTakenCount).
595 const SCEV *getBackedgeTakenCount(const Loop *L);
597 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
598 /// return the least SCEV value that is known never to be less than the
599 /// actual backedge taken count.
600 const SCEV *getMaxBackedgeTakenCount(const Loop *L);
602 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
603 /// has an analyzable loop-invariant backedge-taken count.
604 bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
606 /// forgetLoop - This method should be called by the client when it has
607 /// changed a loop in a way that may effect ScalarEvolution's ability to
608 /// compute a trip count, or if the loop is deleted.
609 void forgetLoop(const Loop *L);
611 /// forgetValue - This method should be called by the client when it has
612 /// changed a value in a way that may effect its value, or which may
613 /// disconnect it from a def-use chain linking it to a loop.
614 void forgetValue(Value *V);
616 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S
617 /// is guaranteed to end in (at every loop iteration). It is, at the same
618 /// time, the minimum number of times S is divisible by 2. For example,
619 /// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the
621 uint32_t GetMinTrailingZeros(const SCEV *S);
623 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
625 ConstantRange getUnsignedRange(const SCEV *S);
627 /// getSignedRange - Determine the signed range for a particular SCEV.
629 ConstantRange getSignedRange(const SCEV *S);
631 /// isKnownNegative - Test if the given expression is known to be negative.
633 bool isKnownNegative(const SCEV *S);
635 /// isKnownPositive - Test if the given expression is known to be positive.
637 bool isKnownPositive(const SCEV *S);
639 /// isKnownNonNegative - Test if the given expression is known to be
642 bool isKnownNonNegative(const SCEV *S);
644 /// isKnownNonPositive - Test if the given expression is known to be
647 bool isKnownNonPositive(const SCEV *S);
649 /// isKnownNonZero - Test if the given expression is known to be
652 bool isKnownNonZero(const SCEV *S);
654 /// isKnownPredicate - Test if the given expression is known to satisfy
655 /// the condition described by Pred, LHS, and RHS.
657 bool isKnownPredicate(ICmpInst::Predicate Pred,
658 const SCEV *LHS, const SCEV *RHS);
660 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
661 /// predicate Pred. Return true iff any changes were made. If the
662 /// operands are provably equal or inequal, LHS and RHS are set to
663 /// the same value and Pred is set to either ICMP_EQ or ICMP_NE.
665 bool SimplifyICmpOperands(ICmpInst::Predicate &Pred,
669 virtual bool runOnFunction(Function &F);
670 virtual void releaseMemory();
671 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
672 virtual void print(raw_ostream &OS, const Module* = 0) const;
675 FoldingSet<SCEV> UniqueSCEVs;
676 BumpPtrAllocator SCEVAllocator;
677 unsigned CurAllocationSequenceNumber;