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      1 //===- InstCombine.h - Main InstCombine pass definition ---------*- 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 
     10 #ifndef INSTCOMBINE_INSTCOMBINE_H
     11 #define INSTCOMBINE_INSTCOMBINE_H
     12 
     13 #include "InstCombineWorklist.h"
     14 #include "llvm/Analysis/ValueTracking.h"
     15 #include "llvm/IR/IRBuilder.h"
     16 #include "llvm/IR/IntrinsicInst.h"
     17 #include "llvm/IR/Operator.h"
     18 #include "llvm/InstVisitor.h"
     19 #include "llvm/Pass.h"
     20 #include "llvm/Support/TargetFolder.h"
     21 #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
     22 
     23 namespace llvm {
     24   class CallSite;
     25   class DataLayout;
     26   class TargetLibraryInfo;
     27   class DbgDeclareInst;
     28   class MemIntrinsic;
     29   class MemSetInst;
     30 
     31 /// SelectPatternFlavor - We can match a variety of different patterns for
     32 /// select operations.
     33 enum SelectPatternFlavor {
     34   SPF_UNKNOWN = 0,
     35   SPF_SMIN, SPF_UMIN,
     36   SPF_SMAX, SPF_UMAX
     37   //SPF_ABS - TODO.
     38 };
     39 
     40 /// getComplexity:  Assign a complexity or rank value to LLVM Values...
     41 ///   0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
     42 static inline unsigned getComplexity(Value *V) {
     43   if (isa<Instruction>(V)) {
     44     if (BinaryOperator::isNeg(V) ||
     45         BinaryOperator::isFNeg(V) ||
     46         BinaryOperator::isNot(V))
     47       return 3;
     48     return 4;
     49   }
     50   if (isa<Argument>(V)) return 3;
     51   return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
     52 }
     53 
     54 
     55 /// InstCombineIRInserter - This is an IRBuilder insertion helper that works
     56 /// just like the normal insertion helper, but also adds any new instructions
     57 /// to the instcombine worklist.
     58 class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
     59     : public IRBuilderDefaultInserter<true> {
     60   InstCombineWorklist &Worklist;
     61 public:
     62   InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
     63 
     64   void InsertHelper(Instruction *I, const Twine &Name,
     65                     BasicBlock *BB, BasicBlock::iterator InsertPt) const {
     66     IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
     67     Worklist.Add(I);
     68   }
     69 };
     70 
     71 /// InstCombiner - The -instcombine pass.
     72 class LLVM_LIBRARY_VISIBILITY InstCombiner
     73                              : public FunctionPass,
     74                                public InstVisitor<InstCombiner, Instruction*> {
     75   DataLayout *TD;
     76   TargetLibraryInfo *TLI;
     77   bool MadeIRChange;
     78   LibCallSimplifier *Simplifier;
     79   bool MinimizeSize;
     80 public:
     81   /// Worklist - All of the instructions that need to be simplified.
     82   InstCombineWorklist Worklist;
     83 
     84   /// Builder - This is an IRBuilder that automatically inserts new
     85   /// instructions into the worklist when they are created.
     86   typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
     87   BuilderTy *Builder;
     88 
     89   static char ID; // Pass identification, replacement for typeid
     90   InstCombiner() : FunctionPass(ID), TD(0), Builder(0) {
     91     MinimizeSize = false;
     92     initializeInstCombinerPass(*PassRegistry::getPassRegistry());
     93   }
     94 
     95 public:
     96   virtual bool runOnFunction(Function &F);
     97 
     98   bool DoOneIteration(Function &F, unsigned ItNum);
     99 
    100   virtual void getAnalysisUsage(AnalysisUsage &AU) const;
    101 
    102   DataLayout *getDataLayout() const { return TD; }
    103 
    104   TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
    105 
    106   // Visitation implementation - Implement instruction combining for different
    107   // instruction types.  The semantics are as follows:
    108   // Return Value:
    109   //    null        - No change was made
    110   //     I          - Change was made, I is still valid, I may be dead though
    111   //   otherwise    - Change was made, replace I with returned instruction
    112   //
    113   Instruction *visitAdd(BinaryOperator &I);
    114   Instruction *visitFAdd(BinaryOperator &I);
    115   Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
    116   Instruction *visitSub(BinaryOperator &I);
    117   Instruction *visitFSub(BinaryOperator &I);
    118   Instruction *visitMul(BinaryOperator &I);
    119   Value *foldFMulConst(Instruction *FMulOrDiv, ConstantFP *C,
    120                        Instruction *InsertBefore);
    121   Instruction *visitFMul(BinaryOperator &I);
    122   Instruction *visitURem(BinaryOperator &I);
    123   Instruction *visitSRem(BinaryOperator &I);
    124   Instruction *visitFRem(BinaryOperator &I);
    125   bool SimplifyDivRemOfSelect(BinaryOperator &I);
    126   Instruction *commonRemTransforms(BinaryOperator &I);
    127   Instruction *commonIRemTransforms(BinaryOperator &I);
    128   Instruction *commonDivTransforms(BinaryOperator &I);
    129   Instruction *commonIDivTransforms(BinaryOperator &I);
    130   Instruction *visitUDiv(BinaryOperator &I);
    131   Instruction *visitSDiv(BinaryOperator &I);
    132   Instruction *visitFDiv(BinaryOperator &I);
    133   Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
    134   Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
    135   Instruction *visitAnd(BinaryOperator &I);
    136   Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS);
    137   Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
    138   Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op,
    139                                    Value *A, Value *B, Value *C);
    140   Instruction *visitOr (BinaryOperator &I);
    141   Instruction *visitXor(BinaryOperator &I);
    142   Instruction *visitShl(BinaryOperator &I);
    143   Instruction *visitAShr(BinaryOperator &I);
    144   Instruction *visitLShr(BinaryOperator &I);
    145   Instruction *commonShiftTransforms(BinaryOperator &I);
    146   Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
    147                                     Constant *RHSC);
    148   Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
    149                                             GlobalVariable *GV, CmpInst &ICI,
    150                                             ConstantInt *AndCst = 0);
    151   Instruction *visitFCmpInst(FCmpInst &I);
    152   Instruction *visitICmpInst(ICmpInst &I);
    153   Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
    154   Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
    155                                               Instruction *LHS,
    156                                               ConstantInt *RHS);
    157   Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
    158                               ConstantInt *DivRHS);
    159   Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
    160                               ConstantInt *DivRHS);
    161   Instruction *FoldICmpAddOpCst(ICmpInst &ICI, Value *X, ConstantInt *CI,
    162                                 ICmpInst::Predicate Pred, Value *TheAdd);
    163   Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
    164                            ICmpInst::Predicate Cond, Instruction &I);
    165   Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
    166                                    BinaryOperator &I);
    167   Instruction *commonCastTransforms(CastInst &CI);
    168   Instruction *commonPointerCastTransforms(CastInst &CI);
    169   Instruction *visitTrunc(TruncInst &CI);
    170   Instruction *visitZExt(ZExtInst &CI);
    171   Instruction *visitSExt(SExtInst &CI);
    172   Instruction *visitFPTrunc(FPTruncInst &CI);
    173   Instruction *visitFPExt(CastInst &CI);
    174   Instruction *visitFPToUI(FPToUIInst &FI);
    175   Instruction *visitFPToSI(FPToSIInst &FI);
    176   Instruction *visitUIToFP(CastInst &CI);
    177   Instruction *visitSIToFP(CastInst &CI);
    178   Instruction *visitPtrToInt(PtrToIntInst &CI);
    179   Instruction *visitIntToPtr(IntToPtrInst &CI);
    180   Instruction *visitBitCast(BitCastInst &CI);
    181   Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
    182                               Instruction *FI);
    183   Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
    184   Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
    185                             Value *A, Value *B, Instruction &Outer,
    186                             SelectPatternFlavor SPF2, Value *C);
    187   Instruction *visitSelectInst(SelectInst &SI);
    188   Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
    189   Instruction *visitCallInst(CallInst &CI);
    190   Instruction *visitInvokeInst(InvokeInst &II);
    191 
    192   Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
    193   Instruction *visitPHINode(PHINode &PN);
    194   Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
    195   Instruction *visitAllocaInst(AllocaInst &AI);
    196   Instruction *visitAllocSite(Instruction &FI);
    197   Instruction *visitFree(CallInst &FI);
    198   Instruction *visitLoadInst(LoadInst &LI);
    199   Instruction *visitStoreInst(StoreInst &SI);
    200   Instruction *visitBranchInst(BranchInst &BI);
    201   Instruction *visitSwitchInst(SwitchInst &SI);
    202   Instruction *visitInsertElementInst(InsertElementInst &IE);
    203   Instruction *visitExtractElementInst(ExtractElementInst &EI);
    204   Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
    205   Instruction *visitExtractValueInst(ExtractValueInst &EV);
    206   Instruction *visitLandingPadInst(LandingPadInst &LI);
    207 
    208   // visitInstruction - Specify what to return for unhandled instructions...
    209   Instruction *visitInstruction(Instruction &I) { return 0; }
    210 
    211 private:
    212   bool ShouldChangeType(Type *From, Type *To) const;
    213   Value *dyn_castNegVal(Value *V) const;
    214   Value *dyn_castFNegVal(Value *V, bool NoSignedZero=false) const;
    215   Type *FindElementAtOffset(Type *Ty, int64_t Offset,
    216                                   SmallVectorImpl<Value*> &NewIndices);
    217   Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
    218 
    219   /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
    220   /// results in any code being generated and is interesting to optimize out. If
    221   /// the cast can be eliminated by some other simple transformation, we prefer
    222   /// to do the simplification first.
    223   bool ShouldOptimizeCast(Instruction::CastOps opcode,const Value *V,
    224                           Type *Ty);
    225 
    226   Instruction *visitCallSite(CallSite CS);
    227   Instruction *tryOptimizeCall(CallInst *CI, const DataLayout *TD);
    228   bool transformConstExprCastCall(CallSite CS);
    229   Instruction *transformCallThroughTrampoline(CallSite CS,
    230                                               IntrinsicInst *Tramp);
    231   Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
    232                                  bool DoXform = true);
    233   Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
    234   bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
    235   Value *EmitGEPOffset(User *GEP);
    236   Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
    237   Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
    238 
    239 public:
    240   // InsertNewInstBefore - insert an instruction New before instruction Old
    241   // in the program.  Add the new instruction to the worklist.
    242   //
    243   Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
    244     assert(New && New->getParent() == 0 &&
    245            "New instruction already inserted into a basic block!");
    246     BasicBlock *BB = Old.getParent();
    247     BB->getInstList().insert(&Old, New);  // Insert inst
    248     Worklist.Add(New);
    249     return New;
    250   }
    251 
    252   // InsertNewInstWith - same as InsertNewInstBefore, but also sets the
    253   // debug loc.
    254   //
    255   Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
    256     New->setDebugLoc(Old.getDebugLoc());
    257     return InsertNewInstBefore(New, Old);
    258   }
    259 
    260   // ReplaceInstUsesWith - This method is to be used when an instruction is
    261   // found to be dead, replacable with another preexisting expression.  Here
    262   // we add all uses of I to the worklist, replace all uses of I with the new
    263   // value, then return I, so that the inst combiner will know that I was
    264   // modified.
    265   //
    266   Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
    267     Worklist.AddUsersToWorkList(I);   // Add all modified instrs to worklist.
    268 
    269     // If we are replacing the instruction with itself, this must be in a
    270     // segment of unreachable code, so just clobber the instruction.
    271     if (&I == V)
    272       V = UndefValue::get(I.getType());
    273 
    274     DEBUG(errs() << "IC: Replacing " << I << "\n"
    275                     "    with " << *V << '\n');
    276 
    277     I.replaceAllUsesWith(V);
    278     return &I;
    279   }
    280 
    281   // EraseInstFromFunction - When dealing with an instruction that has side
    282   // effects or produces a void value, we can't rely on DCE to delete the
    283   // instruction.  Instead, visit methods should return the value returned by
    284   // this function.
    285   Instruction *EraseInstFromFunction(Instruction &I) {
    286     DEBUG(errs() << "IC: ERASE " << I << '\n');
    287 
    288     assert(I.use_empty() && "Cannot erase instruction that is used!");
    289     // Make sure that we reprocess all operands now that we reduced their
    290     // use counts.
    291     if (I.getNumOperands() < 8) {
    292       for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
    293         if (Instruction *Op = dyn_cast<Instruction>(*i))
    294           Worklist.Add(Op);
    295     }
    296     Worklist.Remove(&I);
    297     I.eraseFromParent();
    298     MadeIRChange = true;
    299     return 0;  // Don't do anything with FI
    300   }
    301 
    302   void ComputeMaskedBits(Value *V, APInt &KnownZero,
    303                          APInt &KnownOne, unsigned Depth = 0) const {
    304     return llvm::ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth);
    305   }
    306 
    307   bool MaskedValueIsZero(Value *V, const APInt &Mask,
    308                          unsigned Depth = 0) const {
    309     return llvm::MaskedValueIsZero(V, Mask, TD, Depth);
    310   }
    311   unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
    312     return llvm::ComputeNumSignBits(Op, TD, Depth);
    313   }
    314 
    315 private:
    316 
    317   /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
    318   /// operators which are associative or commutative.
    319   bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
    320 
    321   /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
    322   /// which some other binary operation distributes over either by factorizing
    323   /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
    324   /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
    325   /// a win).  Returns the simplified value, or null if it didn't simplify.
    326   Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
    327 
    328   /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
    329   /// based on the demanded bits.
    330   Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
    331                                  APInt& KnownZero, APInt& KnownOne,
    332                                  unsigned Depth);
    333   bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
    334                             APInt& KnownZero, APInt& KnownOne,
    335                             unsigned Depth=0);
    336   /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
    337   /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
    338   Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl,
    339                                     APInt DemandedMask, APInt &KnownZero,
    340                                     APInt &KnownOne);
    341 
    342   /// SimplifyDemandedInstructionBits - Inst is an integer instruction that
    343   /// SimplifyDemandedBits knows about.  See if the instruction has any
    344   /// properties that allow us to simplify its operands.
    345   bool SimplifyDemandedInstructionBits(Instruction &Inst);
    346 
    347   Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
    348                                     APInt& UndefElts, unsigned Depth = 0);
    349 
    350   // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
    351   // which has a PHI node as operand #0, see if we can fold the instruction
    352   // into the PHI (which is only possible if all operands to the PHI are
    353   // constants).
    354   //
    355   Instruction *FoldOpIntoPhi(Instruction &I);
    356 
    357   // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
    358   // operator and they all are only used by the PHI, PHI together their
    359   // inputs, and do the operation once, to the result of the PHI.
    360   Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
    361   Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
    362   Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
    363   Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
    364 
    365 
    366   Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
    367                         ConstantInt *AndRHS, BinaryOperator &TheAnd);
    368 
    369   Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
    370                             bool isSub, Instruction &I);
    371   Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
    372                          bool isSigned, bool Inside);
    373   Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
    374   Instruction *MatchBSwap(BinaryOperator &I);
    375   bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
    376   Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
    377   Instruction *SimplifyMemSet(MemSetInst *MI);
    378 
    379 
    380   Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
    381 
    382   /// Descale - Return a value X such that Val = X * Scale, or null if none.  If
    383   /// the multiplication is known not to overflow then NoSignedWrap is set.
    384   Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
    385 };
    386 
    387 
    388 
    389 } // end namespace llvm.
    390 
    391 #endif
    392