C++ ConstantExpr::use_end方法代码示例

/// \brief Emit materialization code for all rebased constants and update their
/// users.
void ConstantHoisting::EmitBaseConstants(Function &F, User *U,
                                         Instruction *Base, Constant *Offset,
                                         ConstantInt *OriginalConstant) {
  if (Instruction *I = dyn_cast<Instruction>(U)) {
    Instruction *Mat = Base;
    if (!Offset->isNullValue()) {
      Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
                                   "const_mat", getMatInsertPt(I, DT));

      // Use the same debug location as the instruction we are about to update.
      Mat->setDebugLoc(I->getDebugLoc());

      DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
                   << " + " << *Offset << ") in BB "
                   << I->getParent()->getName() << '\n' << *Mat << '\n');
    }
    DEBUG(dbgs() << "Update: " << *I << '\n');
    I->replaceUsesOfWith(OriginalConstant, Mat);
    DEBUG(dbgs() << "To: " << *I << '\n');
    return;
  }
  assert(isa<ConstantExpr>(U) && "Expected a ConstantExpr.");
  ConstantExpr *CE = cast<ConstantExpr>(U);
  for (Value::use_iterator UU = CE->use_begin(), E = CE->use_end();
       UU != E; ++UU) {
    // We only handel instructions here and won't walk down a ConstantExpr chain
    // to replace all ConstExpr with instructions.
    if (Instruction *I = dyn_cast<Instruction>(*UU)) {
      // Only update constant expressions in the current function.
      if (I->getParent()->getParent() != &F)
        continue;

      Instruction *Mat = Base;
      Instruction *InsertBefore = getMatInsertPt(I, DT);
      if (!Offset->isNullValue()) {
        Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
                                     "const_mat", InsertBefore);

        // Use the same debug location as the instruction we are about to
        // update.
        Mat->setDebugLoc(I->getDebugLoc());

        DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
                     << " + " << *Offset << ") in BB "
                     << I->getParent()->getName() << '\n' << *Mat << '\n');
      }
      Instruction *ICE = CE->getAsInstruction();
      ICE->replaceUsesOfWith(OriginalConstant, Mat);
      ICE->insertBefore(InsertBefore);

      // Use the same debug location as the instruction we are about to update.
      ICE->setDebugLoc(I->getDebugLoc());

      DEBUG(dbgs() << "Create instruction: " << *ICE << '\n');
      DEBUG(dbgs() << "Update: " << *I << '\n');
      I->replaceUsesOfWith(CE, ICE);
      DEBUG(dbgs() << "To: " << *I << '\n');
    }
  }
}

//
// Method: runOnModule()
//
// Description:
//  Entry point for this LLVM pass.
//  Search for all call sites to casted functions.
//  Check if they only differ in an argument type
//  Cast the argument, and call the original function
//
// Inputs:
//  M - A reference to the LLVM module to transform
//
// Outputs:
//  M - The transformed LLVM module.
//
// Return value:
//  true  - The module was modified.
//  false - The module was not modified.
//
bool ArgCast::runOnModule(Module& M) {

  std::vector<CallInst*> worklist;
  for (Module::iterator I = M.begin(); I != M.end(); ++I) {
    if (I->mayBeOverridden())
      continue;
    // Find all uses of this function
    for(Value::use_iterator ui = I->use_begin(), ue = I->use_end(); ui != ue; ) {
      // check if is ever casted to a different function type
      ConstantExpr *CE = dyn_cast<ConstantExpr>(*ui++);
      if(!CE)
        continue;
      if (CE->getOpcode() != Instruction::BitCast)
        continue;
      if(CE->getOperand(0) != I)
        continue;
      const PointerType *PTy = dyn_cast<PointerType>(CE->getType());
      if (!PTy)
        continue;
      const Type *ETy = PTy->getElementType();
      const FunctionType *FTy  = dyn_cast<FunctionType>(ETy); 
      if(!FTy)
        continue;
      // casting to a varargs funtion
      // or function with same number of arguments
      // possibly varying types of arguments
      
      if(FTy->getNumParams() != I->arg_size() && !FTy->isVarArg())
        continue;
      for(Value::use_iterator uii = CE->use_begin(),
          uee = CE->use_end(); uii != uee; ++uii) {
        // Find all uses of the casted value, and check if it is 
        // used in a Call Instruction
        if (CallInst* CI = dyn_cast<CallInst>(*uii)) {
          // Check that it is the called value, and not an argument
          if(CI->getCalledValue() != CE) 
            continue;
          // Check that the number of arguments passed, and expected
          // by the function are the same.
          if(!I->isVarArg()) {
            if(CI->getNumOperands() != I->arg_size() + 1)
              continue;
          } else {
            if(CI->getNumOperands() < I->arg_size() + 1)
              continue;
          }
          // If so, add to worklist
          worklist.push_back(CI);
        }
      }
    }
  }

  // Proces the worklist of potential call sites to transform
  while(!worklist.empty()) {
    CallInst *CI = worklist.back();
    worklist.pop_back();
    // Get the called Function
    Function *F = cast<Function>(CI->getCalledValue()->stripPointerCasts());
    const FunctionType *FTy = F->getFunctionType();

    SmallVector<Value*, 8> Args;
    unsigned i =0;
    for(i =0; i< FTy->getNumParams(); ++i) {
      Type *ArgType = CI->getOperand(i+1)->getType();
      Type *FormalType = FTy->getParamType(i);
      // If the types for this argument match, just add it to the
      // parameter list. No cast needs to be inserted.
      if(ArgType == FormalType) {
        Args.push_back(CI->getOperand(i+1));
      }
      else if(ArgType->isPointerTy() && FormalType->isPointerTy()) {
        CastInst *CastI = CastInst::CreatePointerCast(CI->getOperand(i+1), 
                                                      FormalType, "", CI);
        Args.push_back(CastI);
      } else if (ArgType->isIntegerTy() && FormalType->isIntegerTy()) {
        unsigned SrcBits = ArgType->getScalarSizeInBits();
        unsigned DstBits = FormalType->getScalarSizeInBits();
        if(SrcBits > DstBits) {
          CastInst *CastI = CastInst::CreateIntegerCast(CI->getOperand(i+1), 
                                                        FormalType, true, "", CI);
//.........这里部分代码省略.........