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fixes for strcpy optimizer

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35709 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-07 00:26:18 +00:00
parent 7b50c8f278
commit db895b82a3
1 changed files with 42 additions and 53 deletions
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95
lib/Transforms/IPO/SimplifyLibCalls.cpp
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@ -705,7 +705,7 @@ public:
Value *Str1P = CI->getOperand(1);
Value *Str2P = CI->getOperand(2);
if (Str1P == Str2P) {
// strcmp(x,x) -> 0
// strncmp(x,x) -> 0
CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 0));
CI->eraseFromParent();
return true;
@ -713,8 +713,13 @@ public:
// Check the length argument, if it is Constant zero then the strings are
// considered equal.
ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3));
if (LengthArg && LengthArg->isZero()) {
uint64_t Length;
if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getOperand(3)))
Length = LengthArg->getZExtValue();
else
return false;
if (Length == 0) {
// strncmp(x,y,0) -> 0
CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 0));
CI->eraseFromParent();
@ -725,7 +730,7 @@ public:
ConstantArray *A1;
bool Str1IsCst = GetConstantStringInfo(Str1P, A1, Str1Len, Str1StartIdx);
if (Str1IsCst && Str1Len == 0) {
// strcmp("", x) -> *x
// strncmp("", x) -> *x
Value *V = new LoadInst(Str2P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
CI->replaceAllUsesWith(V);
@ -737,7 +742,7 @@ public:
ConstantArray* A2;
bool Str2IsCst = GetConstantStringInfo(Str2P, A2, Str2Len, Str2StartIdx);
if (Str2IsCst && Str2Len == 0) {
// strcmp(x,"") -> *x
// strncmp(x,"") -> *x
Value *V = new LoadInst(Str1P, CI->getName()+".load", CI);
V = new ZExtInst(V, CI->getType(), CI->getName()+".int", CI);
CI->replaceAllUsesWith(V);
@ -745,13 +750,12 @@ public:
return true;
}
if (LengthArg && Str1IsCst && Str2IsCst && A1->isCString() &&
if (Str1IsCst && Str2IsCst && A1->isCString() &&
A2->isCString()) {
// strcmp(x, y) -> cnst (if both x and y are constant strings)
// strncmp(x, y) -> cnst (if both x and y are constant strings)
std::string S1 = A1->getAsString();
std::string S2 = A2->getAsString();
int R = strncmp(S1.c_str()+Str1StartIdx, S2.c_str()+Str2StartIdx,
LengthArg->getZExtValue());
int R = strncmp(S1.c_str()+Str1StartIdx, S2.c_str()+Str2StartIdx, Length);
CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), R));
CI->eraseFromParent();
return true;
@ -771,71 +775,57 @@ public:
"Number of 'strcpy' calls simplified") {}
/// @brief Make sure that the "strcpy" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
if (f->getReturnType() == PointerType::get(Type::Int8Ty))
if (f->arg_size() == 2) {
Function::const_arg_iterator AI = f->arg_begin();
if (AI++->getType() == PointerType::get(Type::Int8Ty))
if (AI->getType() == PointerType::get(Type::Int8Ty)) {
// Indicate this is a suitable call type.
return true;
}
}
return false;
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
const FunctionType *FT = F->getFunctionType();
return FT->getNumParams() == 2 &&
FT->getParamType(0) == FT->getParamType(1) &&
FT->getReturnType() == FT->getParamType(0) &&
FT->getParamType(0) == PointerType::get(Type::Int8Ty);
}
/// @brief Perform the strcpy optimization
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// First, check to see if src and destination are the same. If they are,
// then the optimization is to replace the CallInst with the destination
// because the call is a no-op. Note that this corresponds to the
// degenerate strcpy(X,X) case which should have "undefined" results
// according to the C specification. However, it occurs sometimes and
// we optimize it as a no-op.
Value* dest = ci->getOperand(1);
Value* src = ci->getOperand(2);
if (dest == src) {
ci->replaceAllUsesWith(dest);
ci->eraseFromParent();
Value *Dst = CI->getOperand(1);
Value *Src = CI->getOperand(2);
if (Dst == Src) {
// strcpy(x, x) -> x
CI->replaceAllUsesWith(Dst);
CI->eraseFromParent();
return true;
}
// Get the length of the constant string referenced by the second operand,
// the "src" parameter. Fail the optimization if we can't get the length
// (note that GetConstantStringInfo does lots of checks to make sure this
// is valid).
uint64_t len, StartIdx;
ConstantArray *A;
if (!GetConstantStringInfo(ci->getOperand(2), A, len, StartIdx))
// Get the length of the constant string referenced by the Src operand.
uint64_t SrcLen, SrcStartIdx;
ConstantArray *SrcArr;
if (!GetConstantStringInfo(Src, SrcArr, SrcLen, SrcStartIdx))
return false;
// If the constant string's length is zero we can optimize this by just
// doing a store of 0 at the first byte of the destination
if (len == 0) {
new StoreInst(ConstantInt::get(Type::Int8Ty,0),ci->getOperand(1),ci);
ci->replaceAllUsesWith(dest);
ci->eraseFromParent();
if (SrcLen == 0) {
new StoreInst(ConstantInt::get(Type::Int8Ty, 0), Dst, CI);
CI->replaceAllUsesWith(Dst);
CI->eraseFromParent();
return true;
}
// Increment the length because we actually want to memcpy the null
// terminator as well.
len++;
// We have enough information to now generate the memcpy call to
// do the concatenation for us.
Value *vals[4] = {
dest, src,
ConstantInt::get(SLC.getIntPtrType(),len), // length
Value *MemcpyOps[] = {
Dst, Src,
ConstantInt::get(SLC.getIntPtrType(), SrcLen), // length including nul.
ConstantInt::get(Type::Int32Ty, 1) // alignment
};
new CallInst(SLC.get_memcpy(), vals, 4, "", ci);
new CallInst(SLC.get_memcpy(), MemcpyOps, 4, "", CI);
// Finally, substitute the first operand of the strcat call for the
// strcat call itself since strcat returns its first operand; and,
// kill the strcat CallInst.
ci->replaceAllUsesWith(dest);
ci->eraseFromParent();
CI->replaceAllUsesWith(Dst);
CI->eraseFromParent();
return true;
}
} StrCpyOptimizer;
@ -849,8 +839,7 @@ struct VISIBILITY_HIDDEN StrLenOptimization : public LibCallOptimization {
"Number of 'strlen' calls simplified") {}
/// @brief Make sure that the "strlen" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
{
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
if (f->arg_size() == 1)
if (Function::const_arg_iterator AI = f->arg_begin())