lib/Transforms/InstCombine/InstCombine.h

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