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/Pass.h"
  15 #include "llvm/Analysis/ValueTracking.h"
  16 #include "llvm/Support/IRBuilder.h"
  17 #include "llvm/Support/InstVisitor.h"
  18 #include "llvm/Support/TargetFolder.h"
  19
  20 namespace llvm {
  21   class CallSite;
  22   class TargetData;
  23   class DbgDeclareInst;
  24   class MemIntrinsic;
  25   class MemSetInst;
  26
  27 /// SelectPatternFlavor - We can match a variety of different patterns for
  28 /// select operations.
  29 enum SelectPatternFlavor {
  30   SPF_UNKNOWN = 0,
  31   SPF_SMIN, SPF_UMIN,
  32   SPF_SMAX, SPF_UMAX
  33   //SPF_ABS - TODO.
  34 };
  35
  36 /// getComplexity:  Assign a complexity or rank value to LLVM Values...
  37 ///   0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
  38 static inline unsigned getComplexity(Value *V) {
  39   if (isa<Instruction>(V)) {
  40     if (BinaryOperator::isNeg(V) ||
  41         BinaryOperator::isFNeg(V) ||
  42         BinaryOperator::isNot(V))
  43       return 3;
  44     return 4;
  45   }
  46   if (isa<Argument>(V)) return 3;
  47   return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
  48 }
  49
  50
  51 /// InstCombineIRInserter - This is an IRBuilder insertion helper that works
  52 /// just like the normal insertion helper, but also adds any new instructions
  53 /// to the instcombine worklist.
  54 class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
  55     : public IRBuilderDefaultInserter<true> {
  56   InstCombineWorklist &Worklist;
  57 public:
  58   InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
  59
  60   void InsertHelper(Instruction *I, const Twine &Name,
  61                     BasicBlock *BB, BasicBlock::iterator InsertPt) const {
  62     IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
  63     Worklist.Add(I);
  64   }
  65 };
  66
  67 /// InstCombiner - The -instcombine pass.
  68 class LLVM_LIBRARY_VISIBILITY InstCombiner
  69                              : public FunctionPass,
  70                                public InstVisitor<InstCombiner, Instruction*> {
  71   TargetData *TD;
  72   bool MustPreserveLCSSA;
  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 *FoldICmpAddOpCst(ICmpInst &ICI, Value *X, ConstantInt *CI,
 149                                 ICmpInst::Predicate Pred, Value *TheAdd);
 150   Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
 151                            ICmpInst::Predicate Cond, Instruction &I);
 152   Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
 153                                    BinaryOperator &I);
 154   Instruction *commonCastTransforms(CastInst &CI);
 155   Instruction *commonPointerCastTransforms(CastInst &CI);
 156   Instruction *visitTrunc(TruncInst &CI);
 157   Instruction *visitZExt(ZExtInst &CI);
 158   Instruction *visitSExt(SExtInst &CI);
 159   Instruction *visitFPTrunc(FPTruncInst &CI);
 160   Instruction *visitFPExt(CastInst &CI);
 161   Instruction *visitFPToUI(FPToUIInst &FI);
 162   Instruction *visitFPToSI(FPToSIInst &FI);
 163   Instruction *visitUIToFP(CastInst &CI);
 164   Instruction *visitSIToFP(CastInst &CI);
 165   Instruction *visitPtrToInt(PtrToIntInst &CI);
 166   Instruction *visitIntToPtr(IntToPtrInst &CI);
 167   Instruction *visitBitCast(BitCastInst &CI);
 168   Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
 169                               Instruction *FI);
 170   Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
 171   Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
 172                             Value *A, Value *B, Instruction &Outer,
 173                             SelectPatternFlavor SPF2, Value *C);
 174   Instruction *visitSelectInst(SelectInst &SI);
 175   Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
 176   Instruction *visitCallInst(CallInst &CI);
 177   Instruction *visitInvokeInst(InvokeInst &II);
 178
 179   Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
 180   Instruction *visitPHINode(PHINode &PN);
 181   Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
 182   Instruction *visitAllocaInst(AllocaInst &AI);
 183   Instruction *visitMalloc(Instruction &FI);
 184   Instruction *visitFree(CallInst &FI);
 185   Instruction *visitLoadInst(LoadInst &LI);
 186   Instruction *visitStoreInst(StoreInst &SI);
 187   Instruction *visitBranchInst(BranchInst &BI);
 188   Instruction *visitSwitchInst(SwitchInst &SI);
 189   Instruction *visitInsertElementInst(InsertElementInst &IE);
 190   Instruction *visitExtractElementInst(ExtractElementInst &EI);
 191   Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
 192   Instruction *visitExtractValueInst(ExtractValueInst &EV);
 193
 194   // visitInstruction - Specify what to return for unhandled instructions...
 195   Instruction *visitInstruction(Instruction &I) { return 0; }
 196
 197 private:
 198   bool ShouldChangeType(const Type *From, const Type *To) const;
 199   Value *dyn_castNegVal(Value *V) const;
 200   Value *dyn_castFNegVal(Value *V) const;
 201   const Type *FindElementAtOffset(const Type *Ty, int64_t Offset,
 202                                   SmallVectorImpl<Value*> &NewIndices);
 203   Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
 204
 205   /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
 206   /// results in any code being generated and is interesting to optimize out. If
 207   /// the cast can be eliminated by some other simple transformation, we prefer
 208   /// to do the simplification first.
 209   bool ShouldOptimizeCast(Instruction::CastOps opcode,const Value *V,
 210                           const Type *Ty);
 211
 212   Instruction *visitCallSite(CallSite CS);
 213   Instruction *tryOptimizeCall(CallInst *CI, const TargetData *TD);
 214   bool transformConstExprCastCall(CallSite CS);
 215   Instruction *transformCallThroughTrampoline(CallSite CS);
 216   Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
 217                                  bool DoXform = true);
 218   bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
 219   DbgDeclareInst *hasOneUsePlusDeclare(Value *V);
 220   Value *EmitGEPOffset(User *GEP);
 221
 222 public:
 223   // InsertNewInstBefore - insert an instruction New before instruction Old
 224   // in the program.  Add the new instruction to the worklist.
 225   //
 226   Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
 227     assert(New && New->getParent() == 0 &&
 228            "New instruction already inserted into a basic block!");
 229     BasicBlock *BB = Old.getParent();
 230     BB->getInstList().insert(&Old, New);  // Insert inst
 231     Worklist.Add(New);
 232     return New;
 233   }
 234
 235   // ReplaceInstUsesWith - This method is to be used when an instruction is
 236   // found to be dead, replacable with another preexisting expression.  Here
 237   // we add all uses of I to the worklist, replace all uses of I with the new
 238   // value, then return I, so that the inst combiner will know that I was
 239   // modified.
 240   //
 241   Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
 242     Worklist.AddUsersToWorkList(I);   // Add all modified instrs to worklist.
 243
 244     // If we are replacing the instruction with itself, this must be in a
 245     // segment of unreachable code, so just clobber the instruction.
 246     if (&I == V)
 247       V = UndefValue::get(I.getType());
 248
 249     I.replaceAllUsesWith(V);
 250     return &I;
 251   }
 252
 253   // EraseInstFromFunction - When dealing with an instruction that has side
 254   // effects or produces a void value, we can't rely on DCE to delete the
 255   // instruction.  Instead, visit methods should return the value returned by
 256   // this function.
 257   Instruction *EraseInstFromFunction(Instruction &I) {
 258     DEBUG(errs() << "IC: ERASE " << I << '\n');
 259
 260     assert(I.use_empty() && "Cannot erase instruction that is used!");
 261     // Make sure that we reprocess all operands now that we reduced their
 262     // use counts.
 263     if (I.getNumOperands() < 8) {
 264       for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
 265         if (Instruction *Op = dyn_cast<Instruction>(*i))
 266           Worklist.Add(Op);
 267     }
 268     Worklist.Remove(&I);
 269     I.eraseFromParent();
 270     MadeIRChange = true;
 271     return 0;  // Don't do anything with FI
 272   }
 273
 274   void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
 275                          APInt &KnownOne, unsigned Depth = 0) const {
 276     return llvm::ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth);
 277   }
 278
 279   bool MaskedValueIsZero(Value *V, const APInt &Mask,
 280                          unsigned Depth = 0) const {
 281     return llvm::MaskedValueIsZero(V, Mask, TD, Depth);
 282   }
 283   unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
 284     return llvm::ComputeNumSignBits(Op, TD, Depth);
 285   }
 286
 287 private:
 288
 289   /// SimplifyCommutative - This performs a few simplifications for
 290   /// commutative operators.
 291   bool SimplifyCommutative(BinaryOperator &I);
 292
 293   /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
 294   /// based on the demanded bits.
 295   Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
 296                                  APInt& KnownZero, APInt& KnownOne,
 297                                  unsigned Depth);
 298   bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
 299                             APInt& KnownZero, APInt& KnownOne,
 300                             unsigned Depth=0);
 301
 302   /// SimplifyDemandedInstructionBits - Inst is an integer instruction that
 303   /// SimplifyDemandedBits knows about.  See if the instruction has any
 304   /// properties that allow us to simplify its operands.
 305   bool SimplifyDemandedInstructionBits(Instruction &Inst);
 306
 307   Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
 308                                     APInt& UndefElts, unsigned Depth = 0);
 309
 310   // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
 311   // which has a PHI node as operand #0, see if we can fold the instruction
 312   // into the PHI (which is only possible if all operands to the PHI are
 313   // constants).
 314   //
 315   // If AllowAggressive is true, FoldOpIntoPhi will allow certain transforms
 316   // that would normally be unprofitable because they strongly encourage jump
 317   // threading.
 318   Instruction *FoldOpIntoPhi(Instruction &I, bool AllowAggressive = false);
 319
 320   // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
 321   // operator and they all are only used by the PHI, PHI together their
 322   // inputs, and do the operation once, to the result of the PHI.
 323   Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
 324   Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
 325   Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
 326   Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
 327
 328
 329   Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
 330                         ConstantInt *AndRHS, BinaryOperator &TheAnd);
 331
 332   Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
 333                             bool isSub, Instruction &I);
 334   Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
 335                          bool isSigned, bool Inside);
 336   Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
 337   Instruction *MatchBSwap(BinaryOperator &I);
 338   bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
 339   Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
 340   Instruction *SimplifyMemSet(MemSetInst *MI);
 341
 342
 343   Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
 344
 345   unsigned GetOrEnforceKnownAlignment(Value *V,
 346                                       unsigned PrefAlign = 0);
 347
 348 };
 349
 350
 351
 352 } // end namespace llvm.
 353
 354 #endif