C++ AllocaInst::user_end方法代码示例

bool LLPE::runOnModule(Module &M) {
  
	vector<int> argv = readInputFile();

	for (Module::iterator F = M.begin(), F_end = M.end(); F != F_end; ++F) {

		for (Function::arg_iterator A = F->arg_begin(), A_end = F->arg_end(); A != A_end; ++A) {
		
			//Search for variables referencing argv
			if (A->getName() == "argv") {
				
				//Iterate through uses of argv
				for (User::user_iterator U = A->user_begin(), U_end = A->user_end(); U != U_end; ++U) {
					Instruction *User = dyn_cast<Instruction>(*U);
					
					StoreInst *SI = dyn_cast<StoreInst>(User);
					AllocaInst *OrigAlloca = dyn_cast<AllocaInst>(SI->getOperand(1));
					
					for (User::user_iterator U2 = OrigAlloca->user_begin(), U2_end = OrigAlloca->user_end(); U2 != U2_end; ++U2) {
						Instruction *User2 = dyn_cast<Instruction>(*U2);

						for (User::user_iterator U3 = User2->user_begin(), U3_end = OrigAlloca->user_end(); U3 != U3_end; ++U3) {
							searchForStoreInstruction(dyn_cast<Instruction>(*U3)->getParent(), argv);
						}
					}

				}
			}
			
		}

	}
   
	return true;
}

/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
/// the call write its result directly into the destination of the memcpy.
bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
                                     Value *cpyDest, Value *cpySrc,
                                     uint64_t cpyLen, unsigned cpyAlign,
                                     CallInst *C) {
  // The general transformation to keep in mind is
  //
  //   call @func(..., src, ...)
  //   memcpy(dest, src, ...)
  //
  // ->
  //
  //   memcpy(dest, src, ...)
  //   call @func(..., dest, ...)
  //
  // Since moving the memcpy is technically awkward, we additionally check that
  // src only holds uninitialized values at the moment of the call, meaning that
  // the memcpy can be discarded rather than moved.

  // Deliberately get the source and destination with bitcasts stripped away,
  // because we'll need to do type comparisons based on the underlying type.
  CallSite CS(C);

  // Require that src be an alloca.  This simplifies the reasoning considerably.
  AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
  if (!srcAlloca)
    return false;

  ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
  if (!srcArraySize)
    return false;

  const DataLayout &DL = cpy->getModule()->getDataLayout();
  uint64_t srcSize = DL.getTypeAllocSize(srcAlloca->getAllocatedType()) *
                     srcArraySize->getZExtValue();

  if (cpyLen < srcSize)
    return false;

  // Check that accessing the first srcSize bytes of dest will not cause a
  // trap.  Otherwise the transform is invalid since it might cause a trap
  // to occur earlier than it otherwise would.
  if (AllocaInst *A = dyn_cast<AllocaInst>(cpyDest)) {
    // The destination is an alloca.  Check it is larger than srcSize.
    ConstantInt *destArraySize = dyn_cast<ConstantInt>(A->getArraySize());
    if (!destArraySize)
      return false;

    uint64_t destSize = DL.getTypeAllocSize(A->getAllocatedType()) *
                        destArraySize->getZExtValue();

    if (destSize < srcSize)
      return false;
  } else if (Argument *A = dyn_cast<Argument>(cpyDest)) {
    if (A->getDereferenceableBytes() < srcSize) {
      // If the destination is an sret parameter then only accesses that are
      // outside of the returned struct type can trap.
      if (!A->hasStructRetAttr())
        return false;

      Type *StructTy = cast<PointerType>(A->getType())->getElementType();
      if (!StructTy->isSized()) {
        // The call may never return and hence the copy-instruction may never
        // be executed, and therefore it's not safe to say "the destination
        // has at least <cpyLen> bytes, as implied by the copy-instruction",
        return false;
      }

      uint64_t destSize = DL.getTypeAllocSize(StructTy);
      if (destSize < srcSize)
        return false;
    }
  } else {
    return false;
  }

  // Check that dest points to memory that is at least as aligned as src.
  unsigned srcAlign = srcAlloca->getAlignment();
  if (!srcAlign)
    srcAlign = DL.getABITypeAlignment(srcAlloca->getAllocatedType());
  bool isDestSufficientlyAligned = srcAlign <= cpyAlign;
  // If dest is not aligned enough and we can't increase its alignment then
  // bail out.
  if (!isDestSufficientlyAligned && !isa<AllocaInst>(cpyDest))
    return false;

  // Check that src is not accessed except via the call and the memcpy.  This
  // guarantees that it holds only undefined values when passed in (so the final
  // memcpy can be dropped), that it is not read or written between the call and
  // the memcpy, and that writing beyond the end of it is undefined.
  SmallVector<User*, 8> srcUseList(srcAlloca->user_begin(),
                                   srcAlloca->user_end());
  while (!srcUseList.empty()) {
    User *U = srcUseList.pop_back_val();

    if (isa<BitCastInst>(U) || isa<AddrSpaceCastInst>(U)) {
      for (User *UU : U->users())
        srcUseList.push_back(UU);
//.........这里部分代码省略.........