InstCombine.h revision 562b84b3aea359d1f918184e355da82bf05eb290 
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/Operator.h"
15#include "llvm/Pass.h"
16#include "llvm/Analysis/ValueTracking.h"
17#include "llvm/Support/IRBuilder.h"
18#include "llvm/Support/InstVisitor.h"
19#include "llvm/Support/TargetFolder.h"
20
21namespace llvm {
22  class CallSite;
23  class TargetData;
24  class DbgDeclareInst;
25  class MemIntrinsic;
26  class MemSetInst;
27
28/// SelectPatternFlavor - We can match a variety of different patterns for
29/// select operations.
30enum SelectPatternFlavor {
31  SPF_UNKNOWN = 0,
32  SPF_SMIN, SPF_UMIN,
33  SPF_SMAX, SPF_UMAX
34  //SPF_ABS - TODO.
35};
36
37/// getComplexity:  Assign a complexity or rank value to LLVM Values...
38///   0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
39static inline unsigned getComplexity(Value *V) {
40  if (isa<Instruction>(V)) {
41    if (BinaryOperator::isNeg(V) ||
42        BinaryOperator::isFNeg(V) ||
43        BinaryOperator::isNot(V))
44      return 3;
45    return 4;
46  }
47  if (isa<Argument>(V)) return 3;
48  return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
49}
50
51
52/// InstCombineIRInserter - This is an IRBuilder insertion helper that works
53/// just like the normal insertion helper, but also adds any new instructions
54/// to the instcombine worklist.
55class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
56    : public IRBuilderDefaultInserter<true> {
57  InstCombineWorklist &Worklist;
58public:
59  InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
60
61  void InsertHelper(Instruction *I, const Twine &Name,
62                    BasicBlock *BB, BasicBlock::iterator InsertPt) const {
63    IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
64    Worklist.Add(I);
65  }
66};
67
68/// InstCombiner - The -instcombine pass.
69class LLVM_LIBRARY_VISIBILITY InstCombiner
70                             : public FunctionPass,
71                               public InstVisitor<InstCombiner, Instruction*> {
72  TargetData *TD;
73  bool MustPreserveLCSSA;
74  bool MadeIRChange;
75public:
76  /// Worklist - All of the instructions that need to be simplified.
77  InstCombineWorklist Worklist;
78
79  /// Builder - This is an IRBuilder that automatically inserts new
80  /// instructions into the worklist when they are created.
81  typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
82  BuilderTy *Builder;
83
84  static char ID; // Pass identification, replacement for typeid
85  InstCombiner() : FunctionPass(ID), TD(0), Builder(0) {
86    initializeInstCombinerPass(*PassRegistry::getPassRegistry());
87  }
88
89public:
90  virtual bool runOnFunction(Function &F);
91
92  bool DoOneIteration(Function &F, unsigned ItNum);
93
94  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
95
96  TargetData *getTargetData() const { return TD; }
97
98  // Visitation implementation - Implement instruction combining for different
99  // instruction types.  The semantics are as follows:
100  // Return Value:
101  //    null        - No change was made
102  //     I          - Change was made, I is still valid, I may be dead though
103  //   otherwise    - Change was made, replace I with returned instruction
104  //
105  Instruction *visitAdd(BinaryOperator &I);
106  Instruction *visitFAdd(BinaryOperator &I);
107  Value *OptimizePointerDifference(Value *LHS, Value *RHS, const Type *Ty);
108  Instruction *visitSub(BinaryOperator &I);
109  Instruction *visitFSub(BinaryOperator &I);
110  Instruction *visitMul(BinaryOperator &I);
111  Instruction *visitFMul(BinaryOperator &I);
112  Instruction *visitURem(BinaryOperator &I);
113  Instruction *visitSRem(BinaryOperator &I);
114  Instruction *visitFRem(BinaryOperator &I);
115  bool SimplifyDivRemOfSelect(BinaryOperator &I);
116  Instruction *commonRemTransforms(BinaryOperator &I);
117  Instruction *commonIRemTransforms(BinaryOperator &I);
118  Instruction *commonDivTransforms(BinaryOperator &I);
119  Instruction *commonIDivTransforms(BinaryOperator &I);
120  Instruction *visitUDiv(BinaryOperator &I);
121  Instruction *visitSDiv(BinaryOperator &I);
122  Instruction *visitFDiv(BinaryOperator &I);
123  Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
124  Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
125  Instruction *visitAnd(BinaryOperator &I);
126  Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS);
127  Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
128  Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op,
129                                   Value *A, Value *B, Value *C);
130  Instruction *visitOr (BinaryOperator &I);
131  Instruction *visitXor(BinaryOperator &I);
132  Instruction *visitShl(BinaryOperator &I);
133  Instruction *visitAShr(BinaryOperator &I);
134  Instruction *visitLShr(BinaryOperator &I);
135  Instruction *commonShiftTransforms(BinaryOperator &I);
136  Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
137                                    Constant *RHSC);
138  Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
139                                            GlobalVariable *GV, CmpInst &ICI,
140                                            ConstantInt *AndCst = 0);
141  Instruction *visitFCmpInst(FCmpInst &I);
142  Instruction *visitICmpInst(ICmpInst &I);
143  Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
144  Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
145                                              Instruction *LHS,
146                                              ConstantInt *RHS);
147  Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
148                              ConstantInt *DivRHS);
149  Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
150                              ConstantInt *DivRHS);
151  Instruction *FoldICmpAddOpCst(ICmpInst &ICI, Value *X, ConstantInt *CI,
152                                ICmpInst::Predicate Pred, Value *TheAdd);
153  Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
154                           ICmpInst::Predicate Cond, Instruction &I);
155  Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
156                                   BinaryOperator &I);
157  Instruction *commonCastTransforms(CastInst &CI);
158  Instruction *commonPointerCastTransforms(CastInst &CI);
159  Instruction *visitTrunc(TruncInst &CI);
160  Instruction *visitZExt(ZExtInst &CI);
161  Instruction *visitSExt(SExtInst &CI);
162  Instruction *visitFPTrunc(FPTruncInst &CI);
163  Instruction *visitFPExt(CastInst &CI);
164  Instruction *visitFPToUI(FPToUIInst &FI);
165  Instruction *visitFPToSI(FPToSIInst &FI);
166  Instruction *visitUIToFP(CastInst &CI);
167  Instruction *visitSIToFP(CastInst &CI);
168  Instruction *visitPtrToInt(PtrToIntInst &CI);
169  Instruction *visitIntToPtr(IntToPtrInst &CI);
170  Instruction *visitBitCast(BitCastInst &CI);
171  Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
172                              Instruction *FI);
173  Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
174  Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
175                            Value *A, Value *B, Instruction &Outer,
176                            SelectPatternFlavor SPF2, Value *C);
177  Instruction *visitSelectInst(SelectInst &SI);
178  Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
179  Instruction *visitCallInst(CallInst &CI);
180  Instruction *visitInvokeInst(InvokeInst &II);
181
182  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
183  Instruction *visitPHINode(PHINode &PN);
184  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
185  Instruction *visitAllocaInst(AllocaInst &AI);
186  Instruction *visitMalloc(Instruction &FI);
187  Instruction *visitFree(CallInst &FI);
188  Instruction *visitLoadInst(LoadInst &LI);
189  Instruction *visitStoreInst(StoreInst &SI);
190  Instruction *visitBranchInst(BranchInst &BI);
191  Instruction *visitSwitchInst(SwitchInst &SI);
192  Instruction *visitInsertElementInst(InsertElementInst &IE);
193  Instruction *visitExtractElementInst(ExtractElementInst &EI);
194  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
195  Instruction *visitExtractValueInst(ExtractValueInst &EV);
196
197  // visitInstruction - Specify what to return for unhandled instructions...
198  Instruction *visitInstruction(Instruction &I) { return 0; }
199
200private:
201  bool ShouldChangeType(const Type *From, const Type *To) const;
202  Value *dyn_castNegVal(Value *V) const;
203  Value *dyn_castFNegVal(Value *V) const;
204  const Type *FindElementAtOffset(const Type *Ty, int64_t Offset,
205                                  SmallVectorImpl<Value*> &NewIndices);
206  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
207
208  /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
209  /// results in any code being generated and is interesting to optimize out. If
210  /// the cast can be eliminated by some other simple transformation, we prefer
211  /// to do the simplification first.
212  bool ShouldOptimizeCast(Instruction::CastOps opcode,const Value *V,
213                          const Type *Ty);
214
215  Instruction *visitCallSite(CallSite CS);
216  Instruction *tryOptimizeCall(CallInst *CI, const TargetData *TD);
217  bool transformConstExprCastCall(CallSite CS);
218  Instruction *transformCallThroughTrampoline(CallSite CS);
219  Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
220                                 bool DoXform = true);
221  Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
222  bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
223  Value *EmitGEPOffset(User *GEP);
224
225public:
226  // InsertNewInstBefore - insert an instruction New before instruction Old
227  // in the program.  Add the new instruction to the worklist.
228  //
229  Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
230    assert(New && New->getParent() == 0 &&
231           "New instruction already inserted into a basic block!");
232    BasicBlock *BB = Old.getParent();
233    BB->getInstList().insert(&Old, New);  // Insert inst
234    Worklist.Add(New);
235    return New;
236  }
237
238  // ReplaceInstUsesWith - This method is to be used when an instruction is
239  // found to be dead, replacable with another preexisting expression.  Here
240  // we add all uses of I to the worklist, replace all uses of I with the new
241  // value, then return I, so that the inst combiner will know that I was
242  // modified.
243  //
244  Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
245    Worklist.AddUsersToWorkList(I);   // Add all modified instrs to worklist.
246
247    // If we are replacing the instruction with itself, this must be in a
248    // segment of unreachable code, so just clobber the instruction.
249    if (&I == V)
250      V = UndefValue::get(I.getType());
251
252    DEBUG(errs() << "IC: Replacing " << I << "\n"
253                    "    with " << *V << '\n');
254
255    I.replaceAllUsesWith(V);
256    return &I;
257  }
258
259  // EraseInstFromFunction - When dealing with an instruction that has side
260  // effects or produces a void value, we can't rely on DCE to delete the
261  // instruction.  Instead, visit methods should return the value returned by
262  // this function.
263  Instruction *EraseInstFromFunction(Instruction &I) {
264    DEBUG(errs() << "IC: ERASE " << I << '\n');
265
266    assert(I.use_empty() && "Cannot erase instruction that is used!");
267    // Make sure that we reprocess all operands now that we reduced their
268    // use counts.
269    if (I.getNumOperands() < 8) {
270      for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
271        if (Instruction *Op = dyn_cast<Instruction>(*i))
272          Worklist.Add(Op);
273    }
274    Worklist.Remove(&I);
275    I.eraseFromParent();
276    MadeIRChange = true;
277    return 0;  // Don't do anything with FI
278  }
279
280  void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
281                         APInt &KnownOne, unsigned Depth = 0) const {
282    return llvm::ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth);
283  }
284
285  bool MaskedValueIsZero(Value *V, const APInt &Mask,
286                         unsigned Depth = 0) const {
287    return llvm::MaskedValueIsZero(V, Mask, TD, Depth);
288  }
289  unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
290    return llvm::ComputeNumSignBits(Op, TD, Depth);
291  }
292
293private:
294
295  /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
296  /// operators which are associative or commutative.
297  bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
298
299  /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
300  /// which some other binary operation distributes over either by factorizing
301  /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
302  /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
303  /// a win).  Returns the simplified value, or null if it didn't simplify.
304  Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
305
306  /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
307  /// based on the demanded bits.
308  Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
309                                 APInt& KnownZero, APInt& KnownOne,
310                                 unsigned Depth);
311  bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
312                            APInt& KnownZero, APInt& KnownOne,
313                            unsigned Depth=0);
314
315  /// SimplifyDemandedInstructionBits - Inst is an integer instruction that
316  /// SimplifyDemandedBits knows about.  See if the instruction has any
317  /// properties that allow us to simplify its operands.
318  bool SimplifyDemandedInstructionBits(Instruction &Inst);
319
320  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
321                                    APInt& UndefElts, unsigned Depth = 0);
322
323  // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
324  // which has a PHI node as operand #0, see if we can fold the instruction
325  // into the PHI (which is only possible if all operands to the PHI are
326  // constants).
327  //
328  Instruction *FoldOpIntoPhi(Instruction &I);
329
330  // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
331  // operator and they all are only used by the PHI, PHI together their
332  // inputs, and do the operation once, to the result of the PHI.
333  Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
334  Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
335  Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
336  Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
337
338
339  Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
340                        ConstantInt *AndRHS, BinaryOperator &TheAnd);
341
342  Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
343                            bool isSub, Instruction &I);
344  Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
345                         bool isSigned, bool Inside);
346  Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
347  Instruction *MatchBSwap(BinaryOperator &I);
348  bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
349  Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
350  Instruction *SimplifyMemSet(MemSetInst *MI);
351
352
353  Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
354};
355
356
357
358} // end namespace llvm.
359
360#endif
361