InstCombine.h revision 9d236f909cec671ef2ff186c8fce6d2e1540a0a9 
1//===- InstCombine.h - Main InstCombine pass definition -------------------===//
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#ifndef INSTCOMBINE_INSTCOMBINE_H
11#define INSTCOMBINE_INSTCOMBINE_H
12
13#include "InstCombineWorklist.h"
14#include "llvm/IntrinsicInst.h"
15#include "llvm/Operator.h"
16#include "llvm/Pass.h"
17#include "llvm/Analysis/ValueTracking.h"
18#include "llvm/Support/IRBuilder.h"
19#include "llvm/Support/InstVisitor.h"
20#include "llvm/Support/TargetFolder.h"
21
22namespace llvm {
23  class CallSite;
24  class TargetData;
25  class TargetLibraryInfo;
26  class DbgDeclareInst;
27  class MemIntrinsic;
28  class MemSetInst;
29
30/// SelectPatternFlavor - We can match a variety of different patterns for
31/// select operations.
32enum SelectPatternFlavor {
33  SPF_UNKNOWN = 0,
34  SPF_SMIN, SPF_UMIN,
35  SPF_SMAX, SPF_UMAX
36  //SPF_ABS - TODO.
37};
38
39/// getComplexity:  Assign a complexity or rank value to LLVM Values...
40///   0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
41static inline unsigned getComplexity(Value *V) {
42  if (isa<Instruction>(V)) {
43    if (BinaryOperator::isNeg(V) ||
44        BinaryOperator::isFNeg(V) ||
45        BinaryOperator::isNot(V))
46      return 3;
47    return 4;
48  }
49  if (isa<Argument>(V)) return 3;
50  return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
51}
52
53
54/// InstCombineIRInserter - This is an IRBuilder insertion helper that works
55/// just like the normal insertion helper, but also adds any new instructions
56/// to the instcombine worklist.
57class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
58    : public IRBuilderDefaultInserter<true> {
59  InstCombineWorklist &Worklist;
60public:
61  InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
62
63  void InsertHelper(Instruction *I, const Twine &Name,
64                    BasicBlock *BB, BasicBlock::iterator InsertPt) const {
65    IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
66    Worklist.Add(I);
67  }
68};
69
70/// InstCombiner - The -instcombine pass.
71class LLVM_LIBRARY_VISIBILITY InstCombiner
72                             : public FunctionPass,
73                               public InstVisitor<InstCombiner, Instruction*> {
74  TargetData *TD;
75  TargetLibraryInfo *TLI;
76  bool MadeIRChange;
77public:
78  /// Worklist - All of the instructions that need to be simplified.
79  InstCombineWorklist Worklist;
80
81  /// Builder - This is an IRBuilder that automatically inserts new
82  /// instructions into the worklist when they are created.
83  typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
84  BuilderTy *Builder;
85
86  static char ID; // Pass identification, replacement for typeid
87  InstCombiner() : FunctionPass(ID), TD(0), Builder(0) {
88    initializeInstCombinerPass(*PassRegistry::getPassRegistry());
89  }
90
91public:
92  virtual bool runOnFunction(Function &F);
93
94  bool DoOneIteration(Function &F, unsigned ItNum);
95
96  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
97
98  TargetData *getTargetData() const { return TD; }
99
100  TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
101
102  // Visitation implementation - Implement instruction combining for different
103  // instruction types.  The semantics are as follows:
104  // Return Value:
105  //    null        - No change was made
106  //     I          - Change was made, I is still valid, I may be dead though
107  //   otherwise    - Change was made, replace I with returned instruction
108  //
109  Instruction *visitAdd(BinaryOperator &I);
110  Instruction *visitFAdd(BinaryOperator &I);
111  Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
112  Instruction *visitSub(BinaryOperator &I);
113  Instruction *visitFSub(BinaryOperator &I);
114  Instruction *visitMul(BinaryOperator &I);
115  Instruction *visitFMul(BinaryOperator &I);
116  Instruction *visitURem(BinaryOperator &I);
117  Instruction *visitSRem(BinaryOperator &I);
118  Instruction *visitFRem(BinaryOperator &I);
119  bool SimplifyDivRemOfSelect(BinaryOperator &I);
120  Instruction *commonRemTransforms(BinaryOperator &I);
121  Instruction *commonIRemTransforms(BinaryOperator &I);
122  Instruction *commonDivTransforms(BinaryOperator &I);
123  Instruction *commonIDivTransforms(BinaryOperator &I);
124  Instruction *visitUDiv(BinaryOperator &I);
125  Instruction *visitSDiv(BinaryOperator &I);
126  Instruction *visitFDiv(BinaryOperator &I);
127  Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
128  Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
129  Instruction *visitAnd(BinaryOperator &I);
130  Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS);
131  Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
132  Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op,
133                                   Value *A, Value *B, Value *C);
134  Instruction *visitOr (BinaryOperator &I);
135  Instruction *visitXor(BinaryOperator &I);
136  Instruction *visitShl(BinaryOperator &I);
137  Instruction *visitAShr(BinaryOperator &I);
138  Instruction *visitLShr(BinaryOperator &I);
139  Instruction *commonShiftTransforms(BinaryOperator &I);
140  Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
141                                    Constant *RHSC);
142  Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
143                                            GlobalVariable *GV, CmpInst &ICI,
144                                            ConstantInt *AndCst = 0);
145  Instruction *visitFCmpInst(FCmpInst &I);
146  Instruction *visitICmpInst(ICmpInst &I);
147  Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
148  Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
149                                              Instruction *LHS,
150                                              ConstantInt *RHS);
151  Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
152                              ConstantInt *DivRHS);
153  Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
154                              ConstantInt *DivRHS);
155  Instruction *FoldICmpAddOpCst(ICmpInst &ICI, Value *X, ConstantInt *CI,
156                                ICmpInst::Predicate Pred, Value *TheAdd);
157  Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
158                           ICmpInst::Predicate Cond, Instruction &I);
159  Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
160                                   BinaryOperator &I);
161  Instruction *commonCastTransforms(CastInst &CI);
162  Instruction *commonPointerCastTransforms(CastInst &CI);
163  Instruction *visitTrunc(TruncInst &CI);
164  Instruction *visitZExt(ZExtInst &CI);
165  Instruction *visitSExt(SExtInst &CI);
166  Instruction *visitFPTrunc(FPTruncInst &CI);
167  Instruction *visitFPExt(CastInst &CI);
168  Instruction *visitFPToUI(FPToUIInst &FI);
169  Instruction *visitFPToSI(FPToSIInst &FI);
170  Instruction *visitUIToFP(CastInst &CI);
171  Instruction *visitSIToFP(CastInst &CI);
172  Instruction *visitPtrToInt(PtrToIntInst &CI);
173  Instruction *visitIntToPtr(IntToPtrInst &CI);
174  Instruction *visitBitCast(BitCastInst &CI);
175  Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
176                              Instruction *FI);
177  Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
178  Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
179                            Value *A, Value *B, Instruction &Outer,
180                            SelectPatternFlavor SPF2, Value *C);
181  Instruction *visitSelectInst(SelectInst &SI);
182  Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
183  Instruction *visitCallInst(CallInst &CI);
184  Instruction *visitInvokeInst(InvokeInst &II);
185
186  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
187  Instruction *visitPHINode(PHINode &PN);
188  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
189  Instruction *visitAllocaInst(AllocaInst &AI);
190  Instruction *visitMalloc(Instruction &FI);
191  Instruction *visitFree(CallInst &FI);
192  Instruction *visitLoadInst(LoadInst &LI);
193  Instruction *visitStoreInst(StoreInst &SI);
194  Instruction *visitBranchInst(BranchInst &BI);
195  Instruction *visitSwitchInst(SwitchInst &SI);
196  Instruction *visitInsertElementInst(InsertElementInst &IE);
197  Instruction *visitExtractElementInst(ExtractElementInst &EI);
198  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
199  Instruction *visitExtractValueInst(ExtractValueInst &EV);
200  Instruction *visitLandingPadInst(LandingPadInst &LI);
201
202  // visitInstruction - Specify what to return for unhandled instructions...
203  Instruction *visitInstruction(Instruction &I) { return 0; }
204
205private:
206  bool ShouldChangeType(Type *From, Type *To) const;
207  Value *dyn_castNegVal(Value *V) const;
208  Value *dyn_castFNegVal(Value *V) const;
209  Type *FindElementAtOffset(Type *Ty, int64_t Offset,
210                                  SmallVectorImpl<Value*> &NewIndices);
211  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
212
213  /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
214  /// results in any code being generated and is interesting to optimize out. If
215  /// the cast can be eliminated by some other simple transformation, we prefer
216  /// to do the simplification first.
217  bool ShouldOptimizeCast(Instruction::CastOps opcode,const Value *V,
218                          Type *Ty);
219
220  Instruction *visitCallSite(CallSite CS);
221  Instruction *tryOptimizeCall(CallInst *CI, const TargetData *TD);
222  bool transformConstExprCastCall(CallSite CS);
223  Instruction *transformCallThroughTrampoline(CallSite CS,
224                                              IntrinsicInst *Tramp);
225  Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
226                                 bool DoXform = true);
227  Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
228  bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
229  Value *EmitGEPOffset(User *GEP, bool NoNUW = false);
230
231public:
232  // InsertNewInstBefore - insert an instruction New before instruction Old
233  // in the program.  Add the new instruction to the worklist.
234  //
235  Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
236    assert(New && New->getParent() == 0 &&
237           "New instruction already inserted into a basic block!");
238    BasicBlock *BB = Old.getParent();
239    BB->getInstList().insert(&Old, New);  // Insert inst
240    Worklist.Add(New);
241    return New;
242  }
243
244  // InsertNewInstWith - same as InsertNewInstBefore, but also sets the
245  // debug loc.
246  //
247  Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
248    New->setDebugLoc(Old.getDebugLoc());
249    return InsertNewInstBefore(New, Old);
250  }
251
252  // ReplaceInstUsesWith - This method is to be used when an instruction is
253  // found to be dead, replacable with another preexisting expression.  Here
254  // we add all uses of I to the worklist, replace all uses of I with the new
255  // value, then return I, so that the inst combiner will know that I was
256  // modified.
257  //
258  Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
259    Worklist.AddUsersToWorkList(I);   // Add all modified instrs to worklist.
260
261    // If we are replacing the instruction with itself, this must be in a
262    // segment of unreachable code, so just clobber the instruction.
263    if (&I == V)
264      V = UndefValue::get(I.getType());
265
266    DEBUG(errs() << "IC: Replacing " << I << "\n"
267                    "    with " << *V << '\n');
268
269    I.replaceAllUsesWith(V);
270    return &I;
271  }
272
273  // EraseInstFromFunction - When dealing with an instruction that has side
274  // effects or produces a void value, we can't rely on DCE to delete the
275  // instruction.  Instead, visit methods should return the value returned by
276  // this function.
277  Instruction *EraseInstFromFunction(Instruction &I) {
278    DEBUG(errs() << "IC: ERASE " << I << '\n');
279
280    assert(I.use_empty() && "Cannot erase instruction that is used!");
281    // Make sure that we reprocess all operands now that we reduced their
282    // use counts.
283    if (I.getNumOperands() < 8) {
284      for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
285        if (Instruction *Op = dyn_cast<Instruction>(*i))
286          Worklist.Add(Op);
287    }
288    Worklist.Remove(&I);
289    I.eraseFromParent();
290    MadeIRChange = true;
291    return 0;  // Don't do anything with FI
292  }
293
294  void ComputeMaskedBits(Value *V, APInt &KnownZero,
295                         APInt &KnownOne, unsigned Depth = 0) const {
296    return llvm::ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth);
297  }
298
299  bool MaskedValueIsZero(Value *V, const APInt &Mask,
300                         unsigned Depth = 0) const {
301    return llvm::MaskedValueIsZero(V, Mask, TD, Depth);
302  }
303  unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
304    return llvm::ComputeNumSignBits(Op, TD, Depth);
305  }
306
307private:
308
309  /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
310  /// operators which are associative or commutative.
311  bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
312
313  /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
314  /// which some other binary operation distributes over either by factorizing
315  /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
316  /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
317  /// a win).  Returns the simplified value, or null if it didn't simplify.
318  Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
319
320  /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
321  /// based on the demanded bits.
322  Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
323                                 APInt& KnownZero, APInt& KnownOne,
324                                 unsigned Depth);
325  bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
326                            APInt& KnownZero, APInt& KnownOne,
327                            unsigned Depth=0);
328
329  /// SimplifyDemandedInstructionBits - Inst is an integer instruction that
330  /// SimplifyDemandedBits knows about.  See if the instruction has any
331  /// properties that allow us to simplify its operands.
332  bool SimplifyDemandedInstructionBits(Instruction &Inst);
333
334  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
335                                    APInt& UndefElts, unsigned Depth = 0);
336
337  // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
338  // which has a PHI node as operand #0, see if we can fold the instruction
339  // into the PHI (which is only possible if all operands to the PHI are
340  // constants).
341  //
342  Instruction *FoldOpIntoPhi(Instruction &I);
343
344  // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
345  // operator and they all are only used by the PHI, PHI together their
346  // inputs, and do the operation once, to the result of the PHI.
347  Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
348  Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
349  Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
350  Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
351
352
353  Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
354                        ConstantInt *AndRHS, BinaryOperator &TheAnd);
355
356  Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
357                            bool isSub, Instruction &I);
358  Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
359                         bool isSigned, bool Inside);
360  Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
361  Instruction *MatchBSwap(BinaryOperator &I);
362  bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
363  Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
364  Instruction *SimplifyMemSet(MemSetInst *MI);
365
366
367  Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
368};
369
370
371
372} // end namespace llvm.
373
374#endif
375