ScalarEvolution.h revision 7e77f7959162a601291fd5400a88908d021033d3
1//===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// The ScalarEvolution class is an LLVM pass which can be used to analyze and
11// catagorize scalar expressions in loops.  It specializes in recognizing
12// general induction variables, representing them with the abstract and opaque
13// SCEV class.  Given this analysis, trip counts of loops and other important
14// properties can be obtained.
15//
16// This analysis is primarily useful for induction variable substitution and
17// strength reduction.
18//
19//===----------------------------------------------------------------------===//
20
21#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
22#define LLVM_ANALYSIS_SCALAREVOLUTION_H
23
24#include "llvm/Pass.h"
25#include "llvm/Instructions.h"
26#include "llvm/Support/DataTypes.h"
27#include "llvm/Support/ValueHandle.h"
28#include "llvm/Support/Allocator.h"
29#include "llvm/Support/ConstantRange.h"
30#include "llvm/ADT/FoldingSet.h"
31#include "llvm/ADT/DenseMap.h"
32#include <iosfwd>
33#include <map>
34
35namespace llvm {
36  class APInt;
37  class Constant;
38  class ConstantInt;
39  class DominatorTree;
40  class Type;
41  class ScalarEvolution;
42  class TargetData;
43  class LLVMContext;
44  class Loop;
45  class LoopInfo;
46  class Operator;
47
48  /// SCEV - This class represents an analyzed expression in the program.  These
49  /// are opaque objects that the client is not allowed to do much with
50  /// directly.
51  ///
52  class SCEV : public FastFoldingSetNode {
53    // The SCEV baseclass this node corresponds to
54    const unsigned short SCEVType;
55
56  protected:
57    /// SubclassData - This field is initialized to zero and may be used in
58    /// subclasses to store miscelaneous information.
59    unsigned short SubclassData;
60
61  private:
62    SCEV(const SCEV &);            // DO NOT IMPLEMENT
63    void operator=(const SCEV &);  // DO NOT IMPLEMENT
64  protected:
65    virtual ~SCEV();
66  public:
67    explicit SCEV(const FoldingSetNodeID &ID, unsigned SCEVTy) :
68      FastFoldingSetNode(ID), SCEVType(SCEVTy), SubclassData(0) {}
69
70    unsigned getSCEVType() const { return SCEVType; }
71
72    /// isLoopInvariant - Return true if the value of this SCEV is unchanging in
73    /// the specified loop.
74    virtual bool isLoopInvariant(const Loop *L) const = 0;
75
76    /// hasComputableLoopEvolution - Return true if this SCEV changes value in a
77    /// known way in the specified loop.  This property being true implies that
78    /// the value is variant in the loop AND that we can emit an expression to
79    /// compute the value of the expression at any particular loop iteration.
80    virtual bool hasComputableLoopEvolution(const Loop *L) const = 0;
81
82    /// getType - Return the LLVM type of this SCEV expression.
83    ///
84    virtual const Type *getType() const = 0;
85
86    /// isZero - Return true if the expression is a constant zero.
87    ///
88    bool isZero() const;
89
90    /// isOne - Return true if the expression is a constant one.
91    ///
92    bool isOne() const;
93
94    /// isAllOnesValue - Return true if the expression is a constant
95    /// all-ones value.
96    ///
97    bool isAllOnesValue() const;
98
99    /// hasOperand - Test whether this SCEV has Op as a direct or
100    /// indirect operand.
101    virtual bool hasOperand(const SCEV *Op) const = 0;
102
103    /// dominates - Return true if elements that makes up this SCEV dominates
104    /// the specified basic block.
105    virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0;
106
107    /// print - Print out the internal representation of this scalar to the
108    /// specified stream.  This should really only be used for debugging
109    /// purposes.
110    virtual void print(raw_ostream &OS) const = 0;
111    void print(std::ostream &OS) const;
112    void print(std::ostream *OS) const { if (OS) print(*OS); }
113
114    /// dump - This method is used for debugging.
115    ///
116    void dump() const;
117  };
118
119  inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
120    S.print(OS);
121    return OS;
122  }
123
124  inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) {
125    S.print(OS);
126    return OS;
127  }
128
129  /// SCEVCouldNotCompute - An object of this class is returned by queries that
130  /// could not be answered.  For example, if you ask for the number of
131  /// iterations of a linked-list traversal loop, you will get one of these.
132  /// None of the standard SCEV operations are valid on this class, it is just a
133  /// marker.
134  struct SCEVCouldNotCompute : public SCEV {
135    SCEVCouldNotCompute();
136
137    // None of these methods are valid for this object.
138    virtual bool isLoopInvariant(const Loop *L) const;
139    virtual const Type *getType() const;
140    virtual bool hasComputableLoopEvolution(const Loop *L) const;
141    virtual void print(raw_ostream &OS) const;
142    virtual bool hasOperand(const SCEV *Op) const;
143
144    virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const {
145      return true;
146    }
147
148    /// Methods for support type inquiry through isa, cast, and dyn_cast:
149    static inline bool classof(const SCEVCouldNotCompute *S) { return true; }
150    static bool classof(const SCEV *S);
151  };
152
153  /// ScalarEvolution - This class is the main scalar evolution driver.  Because
154  /// client code (intentionally) can't do much with the SCEV objects directly,
155  /// they must ask this class for services.
156  ///
157  class ScalarEvolution : public FunctionPass {
158    /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
159    /// notified whenever a Value is deleted.
160    class SCEVCallbackVH : public CallbackVH {
161      ScalarEvolution *SE;
162      virtual void deleted();
163      virtual void allUsesReplacedWith(Value *New);
164    public:
165      SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0);
166    };
167
168    friend class SCEVCallbackVH;
169    friend struct SCEVExpander;
170
171    /// F - The function we are analyzing.
172    ///
173    Function *F;
174
175    /// LI - The loop information for the function we are currently analyzing.
176    ///
177    LoopInfo *LI;
178
179    /// TD - The target data information for the target we are targetting.
180    ///
181    TargetData *TD;
182
183    /// CouldNotCompute - This SCEV is used to represent unknown trip
184    /// counts and things.
185    SCEVCouldNotCompute CouldNotCompute;
186
187    /// Scalars - This is a cache of the scalars we have analyzed so far.
188    ///
189    std::map<SCEVCallbackVH, const SCEV *> Scalars;
190
191    /// BackedgeTakenInfo - Information about the backedge-taken count
192    /// of a loop. This currently inclues an exact count and a maximum count.
193    ///
194    struct BackedgeTakenInfo {
195      /// Exact - An expression indicating the exact backedge-taken count of
196      /// the loop if it is known, or a SCEVCouldNotCompute otherwise.
197      const SCEV *Exact;
198
199      /// Max - An expression indicating the least maximum backedge-taken
200      /// count of the loop that is known, or a SCEVCouldNotCompute.
201      const SCEV *Max;
202
203      /*implicit*/ BackedgeTakenInfo(const SCEV *exact) :
204        Exact(exact), Max(exact) {}
205
206      BackedgeTakenInfo(const SCEV *exact, const SCEV *max) :
207        Exact(exact), Max(max) {}
208
209      /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
210      /// computed information, or whether it's all SCEVCouldNotCompute
211      /// values.
212      bool hasAnyInfo() const {
213        return !isa<SCEVCouldNotCompute>(Exact) ||
214               !isa<SCEVCouldNotCompute>(Max);
215      }
216    };
217
218    /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
219    /// this function as they are computed.
220    std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts;
221
222    /// ConstantEvolutionLoopExitValue - This map contains entries for all of
223    /// the PHI instructions that we attempt to compute constant evolutions for.
224    /// This allows us to avoid potentially expensive recomputation of these
225    /// properties.  An instruction maps to null if we are unable to compute its
226    /// exit value.
227    std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
228
229    /// ValuesAtScopes - This map contains entries for all the instructions
230    /// that we attempt to compute getSCEVAtScope information for without
231    /// using SCEV techniques, which can be expensive.
232    std::map<Instruction *, std::map<const Loop *, Constant *> > ValuesAtScopes;
233
234    /// createSCEV - We know that there is no SCEV for the specified value.
235    /// Analyze the expression.
236    const SCEV *createSCEV(Value *V);
237
238    /// createNodeForPHI - Provide the special handling we need to analyze PHI
239    /// SCEVs.
240    const SCEV *createNodeForPHI(PHINode *PN);
241
242    /// createNodeForGEP - Provide the special handling we need to analyze GEP
243    /// SCEVs.
244    const SCEV *createNodeForGEP(Operator *GEP);
245
246    /// ForgetSymbolicValue - This looks up computed SCEV values for all
247    /// instructions that depend on the given instruction and removes them from
248    /// the Scalars map if they reference SymName. This is used during PHI
249    /// resolution.
250    void ForgetSymbolicName(Instruction *I, const SCEV *SymName);
251
252    /// getBECount - Subtract the end and start values and divide by the step,
253    /// rounding up, to get the number of times the backedge is executed. Return
254    /// CouldNotCompute if an intermediate computation overflows.
255    const SCEV *getBECount(const SCEV *Start,
256                           const SCEV *End,
257                           const SCEV *Step);
258
259    /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given
260    /// loop, lazily computing new values if the loop hasn't been analyzed
261    /// yet.
262    const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
263
264    /// ComputeBackedgeTakenCount - Compute the number of times the specified
265    /// loop will iterate.
266    BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L);
267
268    /// ComputeBackedgeTakenCountFromExit - Compute the number of times the
269    /// backedge of the specified loop will execute if it exits via the
270    /// specified block.
271    BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L,
272                                                      BasicBlock *ExitingBlock);
273
274    /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
275    /// backedge of the specified loop will execute if its exit condition
276    /// were a conditional branch of ExitCond, TBB, and FBB.
277    BackedgeTakenInfo
278      ComputeBackedgeTakenCountFromExitCond(const Loop *L,
279                                            Value *ExitCond,
280                                            BasicBlock *TBB,
281                                            BasicBlock *FBB);
282
283    /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of
284    /// times the backedge of the specified loop will execute if its exit
285    /// condition were a conditional branch of the ICmpInst ExitCond, TBB,
286    /// and FBB.
287    BackedgeTakenInfo
288      ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
289                                                ICmpInst *ExitCond,
290                                                BasicBlock *TBB,
291                                                BasicBlock *FBB);
292
293    /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition
294    /// of 'icmp op load X, cst', try to see if we can compute the
295    /// backedge-taken count.
296    const SCEV *
297      ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
298                                                   Constant *RHS,
299                                                   const Loop *L,
300                                                   ICmpInst::Predicate p);
301
302    /// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute
303    /// a constant number of times (the condition evolves only from constants),
304    /// try to evaluate a few iterations of the loop until we get the exit
305    /// condition gets a value of ExitWhen (true or false).  If we cannot
306    /// evaluate the backedge-taken count of the loop, return CouldNotCompute.
307    const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L,
308                                                      Value *Cond,
309                                                      bool ExitWhen);
310
311    /// HowFarToZero - Return the number of times a backedge comparing the
312    /// specified value to zero will execute.  If not computable, return
313    /// CouldNotCompute.
314    const SCEV *HowFarToZero(const SCEV *V, const Loop *L);
315
316    /// HowFarToNonZero - Return the number of times a backedge checking the
317    /// specified value for nonzero will execute.  If not computable, return
318    /// CouldNotCompute.
319    const SCEV *HowFarToNonZero(const SCEV *V, const Loop *L);
320
321    /// HowManyLessThans - Return the number of times a backedge containing the
322    /// specified less-than comparison will execute.  If not computable, return
323    /// CouldNotCompute. isSigned specifies whether the less-than is signed.
324    BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
325                                       const Loop *L, bool isSigned);
326
327    /// getLoopPredecessor - If the given loop's header has exactly one unique
328    /// predecessor outside the loop, return it. Otherwise return null.
329    BasicBlock *getLoopPredecessor(const Loop *L);
330
331    /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
332    /// (which may not be an immediate predecessor) which has exactly one
333    /// successor from which BB is reachable, or null if no such block is
334    /// found.
335    BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
336
337    /// isImpliedCond - Test whether the condition described by Pred, LHS,
338    /// and RHS is true whenever the given Cond value evaluates to true.
339    bool isImpliedCond(Value *Cond, ICmpInst::Predicate Pred,
340                       const SCEV *LHS, const SCEV *RHS,
341                       bool Inverse);
342
343    /// isImpliedCondOperands - Test whether the condition described by Pred,
344    /// LHS, and RHS is true whenever the condition desribed by Pred, FoundLHS,
345    /// and FoundRHS is true.
346    bool isImpliedCondOperands(ICmpInst::Predicate Pred,
347                               const SCEV *LHS, const SCEV *RHS,
348                               const SCEV *FoundLHS, const SCEV *FoundRHS);
349
350    /// isImpliedCondOperandsHelper - Test whether the condition described by
351    /// Pred, LHS, and RHS is true whenever the condition desribed by Pred,
352    /// FoundLHS, and FoundRHS is true.
353    bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
354                                     const SCEV *LHS, const SCEV *RHS,
355                                     const SCEV *FoundLHS, const SCEV *FoundRHS);
356
357    /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
358    /// in the header of its containing loop, we know the loop executes a
359    /// constant number of times, and the PHI node is just a recurrence
360    /// involving constants, fold it.
361    Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
362                                                const Loop *L);
363
364  public:
365    static char ID; // Pass identification, replacement for typeid
366    ScalarEvolution();
367
368    LLVMContext &getContext() const { return F->getContext(); }
369
370    /// isSCEVable - Test if values of the given type are analyzable within
371    /// the SCEV framework. This primarily includes integer types, and it
372    /// can optionally include pointer types if the ScalarEvolution class
373    /// has access to target-specific information.
374    bool isSCEVable(const Type *Ty) const;
375
376    /// getTypeSizeInBits - Return the size in bits of the specified type,
377    /// for which isSCEVable must return true.
378    uint64_t getTypeSizeInBits(const Type *Ty) const;
379
380    /// getEffectiveSCEVType - Return a type with the same bitwidth as
381    /// the given type and which represents how SCEV will treat the given
382    /// type, for which isSCEVable must return true. For pointer types,
383    /// this is the pointer-sized integer type.
384    const Type *getEffectiveSCEVType(const Type *Ty) const;
385
386    /// getSCEV - Return a SCEV expression handle for the full generality of the
387    /// specified expression.
388    const SCEV *getSCEV(Value *V);
389
390    const SCEV *getConstant(ConstantInt *V);
391    const SCEV *getConstant(const APInt& Val);
392    const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false);
393    const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty);
394    const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty);
395    const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty);
396    const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty);
397    const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops);
398    const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS) {
399      SmallVector<const SCEV *, 2> Ops;
400      Ops.push_back(LHS);
401      Ops.push_back(RHS);
402      return getAddExpr(Ops);
403    }
404    const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1,
405                           const SCEV *Op2) {
406      SmallVector<const SCEV *, 3> Ops;
407      Ops.push_back(Op0);
408      Ops.push_back(Op1);
409      Ops.push_back(Op2);
410      return getAddExpr(Ops);
411    }
412    const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops);
413    const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS) {
414      SmallVector<const SCEV *, 2> Ops;
415      Ops.push_back(LHS);
416      Ops.push_back(RHS);
417      return getMulExpr(Ops);
418    }
419    const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
420    const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
421                              const Loop *L);
422    const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
423                              const Loop *L);
424    const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
425                              const Loop *L) {
426      SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
427      return getAddRecExpr(NewOp, L);
428    }
429    const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
430    const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
431    const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS);
432    const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
433    const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS);
434    const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS);
435    const SCEV *getUnknown(Value *V);
436    const SCEV *getCouldNotCompute();
437
438    /// getNegativeSCEV - Return the SCEV object corresponding to -V.
439    ///
440    const SCEV *getNegativeSCEV(const SCEV *V);
441
442    /// getNotSCEV - Return the SCEV object corresponding to ~V.
443    ///
444    const SCEV *getNotSCEV(const SCEV *V);
445
446    /// getMinusSCEV - Return LHS-RHS.
447    ///
448    const SCEV *getMinusSCEV(const SCEV *LHS,
449                             const SCEV *RHS);
450
451    /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
452    /// of the input value to the specified type.  If the type must be
453    /// extended, it is zero extended.
454    const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty);
455
456    /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion
457    /// of the input value to the specified type.  If the type must be
458    /// extended, it is sign extended.
459    const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty);
460
461    /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of
462    /// the input value to the specified type.  If the type must be extended,
463    /// it is zero extended.  The conversion must not be narrowing.
464    const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty);
465
466    /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of
467    /// the input value to the specified type.  If the type must be extended,
468    /// it is sign extended.  The conversion must not be narrowing.
469    const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty);
470
471    /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
472    /// the input value to the specified type. If the type must be extended,
473    /// it is extended with unspecified bits. The conversion must not be
474    /// narrowing.
475    const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty);
476
477    /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
478    /// input value to the specified type.  The conversion must not be
479    /// widening.
480    const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty);
481
482    /// getIntegerSCEV - Given a SCEVable type, create a constant for the
483    /// specified signed integer value and return a SCEV for the constant.
484    const SCEV *getIntegerSCEV(int Val, const Type *Ty);
485
486    /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
487    /// the types using zero-extension, and then perform a umax operation
488    /// with them.
489    const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS,
490                                           const SCEV *RHS);
491
492    /// getUMinFromMismatchedTypes - Promote the operands to the wider of
493    /// the types using zero-extension, and then perform a umin operation
494    /// with them.
495    const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS,
496                                           const SCEV *RHS);
497
498    /// getSCEVAtScope - Return a SCEV expression handle for the specified value
499    /// at the specified scope in the program.  The L value specifies a loop
500    /// nest to evaluate the expression at, where null is the top-level or a
501    /// specified loop is immediately inside of the loop.
502    ///
503    /// This method can be used to compute the exit value for a variable defined
504    /// in a loop by querying what the value will hold in the parent loop.
505    ///
506    /// In the case that a relevant loop exit value cannot be computed, the
507    /// original value V is returned.
508    const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
509
510    /// getSCEVAtScope - This is a convenience function which does
511    /// getSCEVAtScope(getSCEV(V), L).
512    const SCEV *getSCEVAtScope(Value *V, const Loop *L);
513
514    /// isLoopGuardedByCond - Test whether entry to the loop is protected by
515    /// a conditional between LHS and RHS.  This is used to help avoid max
516    /// expressions in loop trip counts, and to eliminate casts.
517    bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
518                             const SCEV *LHS, const SCEV *RHS);
519
520    /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
521    /// protected by a conditional between LHS and RHS.  This is used to
522    /// to eliminate casts.
523    bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
524                                     const SCEV *LHS, const SCEV *RHS);
525
526    /// getBackedgeTakenCount - If the specified loop has a predictable
527    /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
528    /// object. The backedge-taken count is the number of times the loop header
529    /// will be branched to from within the loop. This is one less than the
530    /// trip count of the loop, since it doesn't count the first iteration,
531    /// when the header is branched to from outside the loop.
532    ///
533    /// Note that it is not valid to call this method on a loop without a
534    /// loop-invariant backedge-taken count (see
535    /// hasLoopInvariantBackedgeTakenCount).
536    ///
537    const SCEV *getBackedgeTakenCount(const Loop *L);
538
539    /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
540    /// return the least SCEV value that is known never to be less than the
541    /// actual backedge taken count.
542    const SCEV *getMaxBackedgeTakenCount(const Loop *L);
543
544    /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
545    /// has an analyzable loop-invariant backedge-taken count.
546    bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
547
548    /// forgetLoopBackedgeTakenCount - This method should be called by the
549    /// client when it has changed a loop in a way that may effect
550    /// ScalarEvolution's ability to compute a trip count, or if the loop
551    /// is deleted.
552    void forgetLoopBackedgeTakenCount(const Loop *L);
553
554    /// GetMinTrailingZeros - Determine the minimum number of zero bits that S
555    /// is guaranteed to end in (at every loop iteration).  It is, at the same
556    /// time, the minimum number of times S is divisible by 2.  For example,
557    /// given {4,+,8} it returns 2.  If S is guaranteed to be 0, it returns the
558    /// bitwidth of S.
559    uint32_t GetMinTrailingZeros(const SCEV *S);
560
561    /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
562    ///
563    ConstantRange getUnsignedRange(const SCEV *S);
564
565    /// getSignedRange - Determine the signed range for a particular SCEV.
566    ///
567    ConstantRange getSignedRange(const SCEV *S);
568
569    /// isKnownNegative - Test if the given expression is known to be negative.
570    ///
571    bool isKnownNegative(const SCEV *S);
572
573    /// isKnownPositive - Test if the given expression is known to be positive.
574    ///
575    bool isKnownPositive(const SCEV *S);
576
577    /// isKnownNonNegative - Test if the given expression is known to be
578    /// non-negative.
579    ///
580    bool isKnownNonNegative(const SCEV *S);
581
582    /// isKnownNonPositive - Test if the given expression is known to be
583    /// non-positive.
584    ///
585    bool isKnownNonPositive(const SCEV *S);
586
587    /// isKnownNonZero - Test if the given expression is known to be
588    /// non-zero.
589    ///
590    bool isKnownNonZero(const SCEV *S);
591
592    /// isKnownNonZero - Test if the given expression is known to satisfy
593    /// the condition described by Pred, LHS, and RHS.
594    ///
595    bool isKnownPredicate(ICmpInst::Predicate Pred,
596                          const SCEV *LHS, const SCEV *RHS);
597
598    virtual bool runOnFunction(Function &F);
599    virtual void releaseMemory();
600    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
601    void print(raw_ostream &OS, const Module* = 0) const;
602    virtual void print(std::ostream &OS, const Module* = 0) const;
603    void print(std::ostream *OS, const Module* M = 0) const {
604      if (OS) print(*OS, M);
605    }
606
607  private:
608    FoldingSet<SCEV> UniqueSCEVs;
609    BumpPtrAllocator SCEVAllocator;
610  };
611}
612
613#endif
614