InstCombineInternal.h revision 286684 
1//===- InstCombineInternal.h - InstCombine pass internals -------*- 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/// \file
10///
11/// This file provides internal interfaces used to implement the InstCombine.
12///
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H
16#define LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINEINTERNAL_H
17
18#include "llvm/Analysis/AliasAnalysis.h"
19#include "llvm/Analysis/AssumptionCache.h"
20#include "llvm/Analysis/LoopInfo.h"
21#include "llvm/Analysis/TargetFolder.h"
22#include "llvm/Analysis/ValueTracking.h"
23#include "llvm/IR/Dominators.h"
24#include "llvm/IR/IRBuilder.h"
25#include "llvm/IR/InstVisitor.h"
26#include "llvm/IR/IntrinsicInst.h"
27#include "llvm/IR/Operator.h"
28#include "llvm/IR/PatternMatch.h"
29#include "llvm/Pass.h"
30#include "llvm/Transforms/InstCombine/InstCombineWorklist.h"
31
32#define DEBUG_TYPE "instcombine"
33
34namespace llvm {
35class CallSite;
36class DataLayout;
37class DominatorTree;
38class TargetLibraryInfo;
39class DbgDeclareInst;
40class MemIntrinsic;
41class MemSetInst;
42
43/// \brief Assign a complexity or rank value to LLVM Values.
44///
45/// This routine maps IR values to various complexity ranks:
46///   0 -> undef
47///   1 -> Constants
48///   2 -> Other non-instructions
49///   3 -> Arguments
50///   3 -> Unary operations
51///   4 -> Other instructions
52static inline unsigned getComplexity(Value *V) {
53  if (isa<Instruction>(V)) {
54    if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
55        BinaryOperator::isNot(V))
56      return 3;
57    return 4;
58  }
59  if (isa<Argument>(V))
60    return 3;
61  return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
62}
63
64/// \brief Add one to a Constant
65static inline Constant *AddOne(Constant *C) {
66  return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
67}
68/// \brief Subtract one from a Constant
69static inline Constant *SubOne(Constant *C) {
70  return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
71}
72
73/// \brief Return true if the specified value is free to invert (apply ~ to).
74/// This happens in cases where the ~ can be eliminated.  If WillInvertAllUses
75/// is true, work under the assumption that the caller intends to remove all
76/// uses of V and only keep uses of ~V.
77///
78static inline bool IsFreeToInvert(Value *V, bool WillInvertAllUses) {
79  // ~(~(X)) -> X.
80  if (BinaryOperator::isNot(V))
81    return true;
82
83  // Constants can be considered to be not'ed values.
84  if (isa<ConstantInt>(V))
85    return true;
86
87  // Compares can be inverted if all of their uses are being modified to use the
88  // ~V.
89  if (isa<CmpInst>(V))
90    return WillInvertAllUses;
91
92  // If `V` is of the form `A + Constant` then `-1 - V` can be folded into `(-1
93  // - Constant) - A` if we are willing to invert all of the uses.
94  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
95    if (BO->getOpcode() == Instruction::Add ||
96        BO->getOpcode() == Instruction::Sub)
97      if (isa<Constant>(BO->getOperand(0)) || isa<Constant>(BO->getOperand(1)))
98        return WillInvertAllUses;
99
100  return false;
101}
102
103
104/// \brief Specific patterns of overflow check idioms that we match.
105enum OverflowCheckFlavor {
106  OCF_UNSIGNED_ADD,
107  OCF_SIGNED_ADD,
108  OCF_UNSIGNED_SUB,
109  OCF_SIGNED_SUB,
110  OCF_UNSIGNED_MUL,
111  OCF_SIGNED_MUL,
112
113  OCF_INVALID
114};
115
116/// \brief Returns the OverflowCheckFlavor corresponding to a overflow_with_op
117/// intrinsic.
118static inline OverflowCheckFlavor
119IntrinsicIDToOverflowCheckFlavor(unsigned ID) {
120  switch (ID) {
121  default:
122    return OCF_INVALID;
123  case Intrinsic::uadd_with_overflow:
124    return OCF_UNSIGNED_ADD;
125  case Intrinsic::sadd_with_overflow:
126    return OCF_SIGNED_ADD;
127  case Intrinsic::usub_with_overflow:
128    return OCF_UNSIGNED_SUB;
129  case Intrinsic::ssub_with_overflow:
130    return OCF_SIGNED_SUB;
131  case Intrinsic::umul_with_overflow:
132    return OCF_UNSIGNED_MUL;
133  case Intrinsic::smul_with_overflow:
134    return OCF_SIGNED_MUL;
135  }
136}
137
138/// \brief An IRBuilder inserter that adds new instructions to the instcombine
139/// worklist.
140class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
141    : public IRBuilderDefaultInserter<true> {
142  InstCombineWorklist &Worklist;
143  AssumptionCache *AC;
144
145public:
146  InstCombineIRInserter(InstCombineWorklist &WL, AssumptionCache *AC)
147      : Worklist(WL), AC(AC) {}
148
149  void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
150                    BasicBlock::iterator InsertPt) const {
151    IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
152    Worklist.Add(I);
153
154    using namespace llvm::PatternMatch;
155    if (match(I, m_Intrinsic<Intrinsic::assume>()))
156      AC->registerAssumption(cast<CallInst>(I));
157  }
158};
159
160/// \brief The core instruction combiner logic.
161///
162/// This class provides both the logic to recursively visit instructions and
163/// combine them, as well as the pass infrastructure for running this as part
164/// of the LLVM pass pipeline.
165class LLVM_LIBRARY_VISIBILITY InstCombiner
166    : public InstVisitor<InstCombiner, Instruction *> {
167  // FIXME: These members shouldn't be public.
168public:
169  /// \brief A worklist of the instructions that need to be simplified.
170  InstCombineWorklist &Worklist;
171
172  /// \brief An IRBuilder that automatically inserts new instructions into the
173  /// worklist.
174  typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
175  BuilderTy *Builder;
176
177private:
178  // Mode in which we are running the combiner.
179  const bool MinimizeSize;
180
181  AliasAnalysis *AA;
182
183  // Required analyses.
184  // FIXME: These can never be null and should be references.
185  AssumptionCache *AC;
186  TargetLibraryInfo *TLI;
187  DominatorTree *DT;
188  const DataLayout &DL;
189
190  // Optional analyses. When non-null, these can both be used to do better
191  // combining and will be updated to reflect any changes.
192  LoopInfo *LI;
193
194  bool MadeIRChange;
195
196public:
197  InstCombiner(InstCombineWorklist &Worklist, BuilderTy *Builder,
198               bool MinimizeSize, AliasAnalysis *AA,
199               AssumptionCache *AC, TargetLibraryInfo *TLI,
200               DominatorTree *DT, const DataLayout &DL, LoopInfo *LI)
201      : Worklist(Worklist), Builder(Builder), MinimizeSize(MinimizeSize),
202        AA(AA), AC(AC), TLI(TLI), DT(DT), DL(DL), LI(LI), MadeIRChange(false) {}
203
204  /// \brief Run the combiner over the entire worklist until it is empty.
205  ///
206  /// \returns true if the IR is changed.
207  bool run();
208
209  AssumptionCache *getAssumptionCache() const { return AC; }
210
211  const DataLayout &getDataLayout() const { return DL; }
212
213  DominatorTree *getDominatorTree() const { return DT; }
214
215  LoopInfo *getLoopInfo() const { return LI; }
216
217  TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
218
219  // Visitation implementation - Implement instruction combining for different
220  // instruction types.  The semantics are as follows:
221  // Return Value:
222  //    null        - No change was made
223  //     I          - Change was made, I is still valid, I may be dead though
224  //   otherwise    - Change was made, replace I with returned instruction
225  //
226  Instruction *visitAdd(BinaryOperator &I);
227  Instruction *visitFAdd(BinaryOperator &I);
228  Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
229  Instruction *visitSub(BinaryOperator &I);
230  Instruction *visitFSub(BinaryOperator &I);
231  Instruction *visitMul(BinaryOperator &I);
232  Value *foldFMulConst(Instruction *FMulOrDiv, Constant *C,
233                       Instruction *InsertBefore);
234  Instruction *visitFMul(BinaryOperator &I);
235  Instruction *visitURem(BinaryOperator &I);
236  Instruction *visitSRem(BinaryOperator &I);
237  Instruction *visitFRem(BinaryOperator &I);
238  bool SimplifyDivRemOfSelect(BinaryOperator &I);
239  Instruction *commonRemTransforms(BinaryOperator &I);
240  Instruction *commonIRemTransforms(BinaryOperator &I);
241  Instruction *commonDivTransforms(BinaryOperator &I);
242  Instruction *commonIDivTransforms(BinaryOperator &I);
243  Instruction *visitUDiv(BinaryOperator &I);
244  Instruction *visitSDiv(BinaryOperator &I);
245  Instruction *visitFDiv(BinaryOperator &I);
246  Value *simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1, bool Inverted);
247  Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
248  Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
249  Instruction *visitAnd(BinaryOperator &I);
250  Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS, Instruction *CxtI);
251  Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
252  Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op, Value *A,
253                                   Value *B, Value *C);
254  Instruction *FoldXorWithConstants(BinaryOperator &I, Value *Op, Value *A,
255                                    Value *B, Value *C);
256  Instruction *visitOr(BinaryOperator &I);
257  Instruction *visitXor(BinaryOperator &I);
258  Instruction *visitShl(BinaryOperator &I);
259  Instruction *visitAShr(BinaryOperator &I);
260  Instruction *visitLShr(BinaryOperator &I);
261  Instruction *commonShiftTransforms(BinaryOperator &I);
262  Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
263                                    Constant *RHSC);
264  Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
265                                            GlobalVariable *GV, CmpInst &ICI,
266                                            ConstantInt *AndCst = nullptr);
267  Instruction *visitFCmpInst(FCmpInst &I);
268  Instruction *visitICmpInst(ICmpInst &I);
269  Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
270  Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI, Instruction *LHS,
271                                              ConstantInt *RHS);
272  Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
273                              ConstantInt *DivRHS);
274  Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
275                              ConstantInt *DivRHS);
276  Instruction *FoldICmpCstShrCst(ICmpInst &I, Value *Op, Value *A,
277                                 ConstantInt *CI1, ConstantInt *CI2);
278  Instruction *FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A,
279                                 ConstantInt *CI1, ConstantInt *CI2);
280  Instruction *FoldICmpAddOpCst(Instruction &ICI, Value *X, ConstantInt *CI,
281                                ICmpInst::Predicate Pred);
282  Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
283                           ICmpInst::Predicate Cond, Instruction &I);
284  Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1,
285                                   BinaryOperator &I);
286  Instruction *commonCastTransforms(CastInst &CI);
287  Instruction *commonPointerCastTransforms(CastInst &CI);
288  Instruction *visitTrunc(TruncInst &CI);
289  Instruction *visitZExt(ZExtInst &CI);
290  Instruction *visitSExt(SExtInst &CI);
291  Instruction *visitFPTrunc(FPTruncInst &CI);
292  Instruction *visitFPExt(CastInst &CI);
293  Instruction *visitFPToUI(FPToUIInst &FI);
294  Instruction *visitFPToSI(FPToSIInst &FI);
295  Instruction *visitUIToFP(CastInst &CI);
296  Instruction *visitSIToFP(CastInst &CI);
297  Instruction *visitPtrToInt(PtrToIntInst &CI);
298  Instruction *visitIntToPtr(IntToPtrInst &CI);
299  Instruction *visitBitCast(BitCastInst &CI);
300  Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI);
301  Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
302  Instruction *FoldSelectIntoOp(SelectInst &SI, Value *, Value *);
303  Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
304                            Value *A, Value *B, Instruction &Outer,
305                            SelectPatternFlavor SPF2, Value *C);
306  Instruction *FoldItoFPtoI(Instruction &FI);
307  Instruction *visitSelectInst(SelectInst &SI);
308  Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
309  Instruction *visitCallInst(CallInst &CI);
310  Instruction *visitInvokeInst(InvokeInst &II);
311
312  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
313  Instruction *visitPHINode(PHINode &PN);
314  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
315  Instruction *visitAllocaInst(AllocaInst &AI);
316  Instruction *visitAllocSite(Instruction &FI);
317  Instruction *visitFree(CallInst &FI);
318  Instruction *visitLoadInst(LoadInst &LI);
319  Instruction *visitStoreInst(StoreInst &SI);
320  Instruction *visitBranchInst(BranchInst &BI);
321  Instruction *visitSwitchInst(SwitchInst &SI);
322  Instruction *visitReturnInst(ReturnInst &RI);
323  Instruction *visitInsertValueInst(InsertValueInst &IV);
324  Instruction *visitInsertElementInst(InsertElementInst &IE);
325  Instruction *visitExtractElementInst(ExtractElementInst &EI);
326  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
327  Instruction *visitExtractValueInst(ExtractValueInst &EV);
328  Instruction *visitLandingPadInst(LandingPadInst &LI);
329
330  // visitInstruction - Specify what to return for unhandled instructions...
331  Instruction *visitInstruction(Instruction &I) { return nullptr; }
332
333  // True when DB dominates all uses of DI execpt UI.
334  // UI must be in the same block as DI.
335  // The routine checks that the DI parent and DB are different.
336  bool dominatesAllUses(const Instruction *DI, const Instruction *UI,
337                        const BasicBlock *DB) const;
338
339  // Replace select with select operand SIOpd in SI-ICmp sequence when possible
340  bool replacedSelectWithOperand(SelectInst *SI, const ICmpInst *Icmp,
341                                 const unsigned SIOpd);
342
343private:
344  bool ShouldChangeType(Type *From, Type *To) const;
345  Value *dyn_castNegVal(Value *V) const;
346  Value *dyn_castFNegVal(Value *V, bool NoSignedZero = false) const;
347  Type *FindElementAtOffset(PointerType *PtrTy, int64_t Offset,
348                            SmallVectorImpl<Value *> &NewIndices);
349  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
350
351  /// \brief Classify whether a cast is worth optimizing.
352  ///
353  /// Returns true if the cast from "V to Ty" actually results in any code
354  /// being generated and is interesting to optimize out. If the cast can be
355  /// eliminated by some other simple transformation, we prefer to do the
356  /// simplification first.
357  bool ShouldOptimizeCast(Instruction::CastOps opcode, const Value *V,
358                          Type *Ty);
359
360  /// \brief Try to optimize a sequence of instructions checking if an operation
361  /// on LHS and RHS overflows.
362  ///
363  /// If a simplification is possible, stores the simplified result of the
364  /// operation in OperationResult and result of the overflow check in
365  /// OverflowResult, and return true.  If no simplification is possible,
366  /// returns false.
367  bool OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS, Value *RHS,
368                             Instruction &CtxI, Value *&OperationResult,
369                             Constant *&OverflowResult);
370
371  Instruction *visitCallSite(CallSite CS);
372  Instruction *tryOptimizeCall(CallInst *CI);
373  bool transformConstExprCastCall(CallSite CS);
374  Instruction *transformCallThroughTrampoline(CallSite CS,
375                                              IntrinsicInst *Tramp);
376  Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
377                                 bool DoXform = true);
378  Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
379  bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS, Instruction &CxtI);
380  bool WillNotOverflowSignedSub(Value *LHS, Value *RHS, Instruction &CxtI);
381  bool WillNotOverflowUnsignedSub(Value *LHS, Value *RHS, Instruction &CxtI);
382  bool WillNotOverflowSignedMul(Value *LHS, Value *RHS, Instruction &CxtI);
383  Value *EmitGEPOffset(User *GEP);
384  Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
385  Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
386
387public:
388  /// \brief Inserts an instruction \p New before instruction \p Old
389  ///
390  /// Also adds the new instruction to the worklist and returns \p New so that
391  /// it is suitable for use as the return from the visitation patterns.
392  Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
393    assert(New && !New->getParent() &&
394           "New instruction already inserted into a basic block!");
395    BasicBlock *BB = Old.getParent();
396    BB->getInstList().insert(&Old, New); // Insert inst
397    Worklist.Add(New);
398    return New;
399  }
400
401  /// \brief Same as InsertNewInstBefore, but also sets the debug loc.
402  Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
403    New->setDebugLoc(Old.getDebugLoc());
404    return InsertNewInstBefore(New, Old);
405  }
406
407  /// \brief A combiner-aware RAUW-like routine.
408  ///
409  /// This method is to be used when an instruction is found to be dead,
410  /// replacable with another preexisting expression. Here we add all uses of
411  /// I to the worklist, replace all uses of I with the new value, then return
412  /// I, so that the inst combiner will know that I was modified.
413  Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
414    // If there are no uses to replace, then we return nullptr to indicate that
415    // no changes were made to the program.
416    if (I.use_empty()) return nullptr;
417
418    Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.
419
420    // If we are replacing the instruction with itself, this must be in a
421    // segment of unreachable code, so just clobber the instruction.
422    if (&I == V)
423      V = UndefValue::get(I.getType());
424
425    DEBUG(dbgs() << "IC: Replacing " << I << "\n"
426                 << "    with " << *V << '\n');
427
428    I.replaceAllUsesWith(V);
429    return &I;
430  }
431
432  /// Creates a result tuple for an overflow intrinsic \p II with a given
433  /// \p Result and a constant \p Overflow value.
434  Instruction *CreateOverflowTuple(IntrinsicInst *II, Value *Result,
435                                   Constant *Overflow) {
436    Constant *V[] = {UndefValue::get(Result->getType()), Overflow};
437    StructType *ST = cast<StructType>(II->getType());
438    Constant *Struct = ConstantStruct::get(ST, V);
439    return InsertValueInst::Create(Struct, Result, 0);
440  }
441
442  /// \brief Combiner aware instruction erasure.
443  ///
444  /// When dealing with an instruction that has side effects or produces a void
445  /// value, we can't rely on DCE to delete the instruction. Instead, visit
446  /// methods should return the value returned by this function.
447  Instruction *EraseInstFromFunction(Instruction &I) {
448    DEBUG(dbgs() << "IC: ERASE " << I << '\n');
449
450    assert(I.use_empty() && "Cannot erase instruction that is used!");
451    // Make sure that we reprocess all operands now that we reduced their
452    // use counts.
453    if (I.getNumOperands() < 8) {
454      for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
455        if (Instruction *Op = dyn_cast<Instruction>(*i))
456          Worklist.Add(Op);
457    }
458    Worklist.Remove(&I);
459    I.eraseFromParent();
460    MadeIRChange = true;
461    return nullptr; // Don't do anything with FI
462  }
463
464  void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne,
465                        unsigned Depth, Instruction *CxtI) const {
466    return llvm::computeKnownBits(V, KnownZero, KnownOne, DL, Depth, AC, CxtI,
467                                  DT);
468  }
469
470  bool MaskedValueIsZero(Value *V, const APInt &Mask, unsigned Depth = 0,
471                         Instruction *CxtI = nullptr) const {
472    return llvm::MaskedValueIsZero(V, Mask, DL, Depth, AC, CxtI, DT);
473  }
474  unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0,
475                              Instruction *CxtI = nullptr) const {
476    return llvm::ComputeNumSignBits(Op, DL, Depth, AC, CxtI, DT);
477  }
478  void ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne,
479                      unsigned Depth = 0, Instruction *CxtI = nullptr) const {
480    return llvm::ComputeSignBit(V, KnownZero, KnownOne, DL, Depth, AC, CxtI,
481                                DT);
482  }
483  OverflowResult computeOverflowForUnsignedMul(Value *LHS, Value *RHS,
484                                               const Instruction *CxtI) {
485    return llvm::computeOverflowForUnsignedMul(LHS, RHS, DL, AC, CxtI, DT);
486  }
487  OverflowResult computeOverflowForUnsignedAdd(Value *LHS, Value *RHS,
488                                               const Instruction *CxtI) {
489    return llvm::computeOverflowForUnsignedAdd(LHS, RHS, DL, AC, CxtI, DT);
490  }
491
492private:
493  /// \brief Performs a few simplifications for operators which are associative
494  /// or commutative.
495  bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
496
497  /// \brief Tries to simplify binary operations which some other binary
498  /// operation distributes over.
499  ///
500  /// It does this by either by factorizing out common terms (eg "(A*B)+(A*C)"
501  /// -> "A*(B+C)") or expanding out if this results in simplifications (eg: "A
502  /// & (B | C) -> (A&B) | (A&C)" if this is a win).  Returns the simplified
503  /// value, or null if it didn't simplify.
504  Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
505
506  /// \brief Attempts to replace V with a simpler value based on the demanded
507  /// bits.
508  Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, APInt &KnownZero,
509                                 APInt &KnownOne, unsigned Depth,
510                                 Instruction *CxtI);
511  bool SimplifyDemandedBits(Use &U, APInt DemandedMask, APInt &KnownZero,
512                            APInt &KnownOne, unsigned Depth = 0);
513  /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
514  /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
515  Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl,
516                                    APInt DemandedMask, APInt &KnownZero,
517                                    APInt &KnownOne);
518
519  /// \brief Tries to simplify operands to an integer instruction based on its
520  /// demanded bits.
521  bool SimplifyDemandedInstructionBits(Instruction &Inst);
522
523  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
524                                    APInt &UndefElts, unsigned Depth = 0);
525
526  Value *SimplifyVectorOp(BinaryOperator &Inst);
527  Value *SimplifyBSwap(BinaryOperator &Inst);
528
529  // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
530  // which has a PHI node as operand #0, see if we can fold the instruction
531  // into the PHI (which is only possible if all operands to the PHI are
532  // constants).
533  //
534  Instruction *FoldOpIntoPhi(Instruction &I);
535
536  /// \brief Try to rotate an operation below a PHI node, using PHI nodes for
537  /// its operands.
538  Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
539  Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
540  Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
541  Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
542
543  Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
544                        ConstantInt *AndRHS, BinaryOperator &TheAnd);
545
546  Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
547                            bool isSub, Instruction &I);
548  Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi, bool isSigned,
549                         bool Inside);
550  Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
551  Instruction *MatchBSwap(BinaryOperator &I);
552  bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
553  Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
554  Instruction *SimplifyMemSet(MemSetInst *MI);
555
556  Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
557
558  /// \brief Returns a value X such that Val = X * Scale, or null if none.
559  ///
560  /// If the multiplication is known not to overflow then NoSignedWrap is set.
561  Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
562};
563
564} // end namespace llvm.
565
566#undef DEBUG_TYPE
567
568#endif
569