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Use immediate stores.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43055 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-10-16 23:44:18 +00:00
parent db44bf85d8
commit 16a04f3f20
1 changed files with 25 additions and 3 deletions
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28
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -7673,18 +7673,40 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
unsigned Size = MemOpLength->getZExtValue();
unsigned Align = cast<ConstantInt>(CI.getOperand(4))->getZExtValue();
PointerType *NewPtrTy = NULL;
unsigned numBits = Size << 3;
// Destination pointer type is always i8 *
// If Size is 8 then use Int64Ty
// If Size is 4 then use Int32Ty
// If Size is 2 then use Int16Ty
// If Size is 1 then use Int8Ty
if (Size && Size <=8 && !(Size&(Size-1)))
NewPtrTy = PointerType::get(IntegerType::get(Size<<3));
NewPtrTy = PointerType::get(IntegerType::get(numBits));
if (NewPtrTy) {
Value *Src = InsertCastBefore(Instruction::BitCast, CI.getOperand(2), NewPtrTy, CI);
Value *L = NULL;
// If source is a null terminated constant c string then try to use immediate store.
if (Constant *C = dyn_cast<Constant>(CI.getOperand(2))) {
const std::string &Str = C->getStringValue();
if (!Str.empty()) {
APInt StrVal(numBits, 0);
unsigned len = Str.length();
APInt SingleChar(numBits, 0);
for (unsigned i = 0; i < len; i++) {
SingleChar = (uint64_t) Str[i];
StrVal = (StrVal << 8) | SingleChar;
}
// Append NULL at the end.
SingleChar = 0;
StrVal = (StrVal << 8) | SingleChar;
L = ConstantInt::get(StrVal);
}
}
// Otherwise load source from memory.
if (L == NULL) {
Value *Src = InsertCastBefore(Instruction::BitCast, CI.getOperand(2), NewPtrTy, CI);
L = new LoadInst(Src, "tmp", false, Align, &CI);
}
Value *Dest = InsertCastBefore(Instruction::BitCast, CI.getOperand(1), NewPtrTy, CI);
Value *L = new LoadInst(Src, "tmp", false, Align, &CI);
Value *NS = new StoreInst(L, Dest, false, Align, &CI);
CI.replaceAllUsesWith(NS);
Changed = true;