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clean up strcat optimizer, no functionality change.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35704 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-06 22:59:33 +00:00
parent c8e1741bb9
commit 09c11aa7f5
1 changed files with 21 additions and 28 deletions
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49
lib/Transforms/IPO/SimplifyLibCalls.cpp
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@ -474,57 +474,50 @@ public:
}
/// @brief Optimize the strcat library function
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC) {
virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
// Extract some information from the instruction
Value* dest = ci->getOperand(1);
Value* src = ci->getOperand(2);
Value *Dst = CI->getOperand(1);
Value *Src = CI->getOperand(2);
// Extract the initializer (while making numerous checks) from the
// source operand of the call to strcat. If we get null back, one of
// a variety of checks in get_GVInitializer failed
uint64_t len, StartIdx;
// source operand of the call to strcat.
uint64_t SrcLength, StartIdx;
ConstantArray *Arr;
if (!GetConstantStringInfo(src, Arr, len, StartIdx))
if (!GetConstantStringInfo(Src, Arr, SrcLength, StartIdx))
return false;
// Handle the simple, do-nothing case
if (len == 0) {
ci->replaceAllUsesWith(dest);
ci->eraseFromParent();
if (SrcLength == 0) {
CI->replaceAllUsesWith(Dst);
CI->eraseFromParent();
return true;
}
// Increment the length because we actually want to memcpy the null
// terminator as well.
len++;
// We need to find the end of the destination string. That's where the
// memory is to be moved to. We just generate a call to strlen (further
// optimized in another pass). Note that the SLC.get_strlen() call
// caches the Function* for us.
CallInst* strlen_inst =
new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
// optimized in another pass).
CallInst *DstLen = new CallInst(SLC.get_strlen(), Dst,
Dst->getName()+".len", CI);
// Now that we have the destination's length, we must index into the
// destination's pointer to get the actual memcpy destination (end of
// the string .. we're concatenating).
GetElementPtrInst* gep =
new GetElementPtrInst(dest, strlen_inst, dest->getName()+".indexed", ci);
Dst = new GetElementPtrInst(Dst, DstLen, Dst->getName()+".indexed", CI);
// We have enough information to now generate the memcpy call to
// do the concatenation for us.
Value *vals[4];
vals[0] = gep; // destination
vals[1] = ci->getOperand(2); // source
vals[2] = ConstantInt::get(SLC.getIntPtrType(),len); // length
vals[3] = ConstantInt::get(Type::Int32Ty,1); // alignment
new CallInst(SLC.get_memcpy(), vals, 4, "", ci);
Value *Vals[] = {
Dst, Src,
ConstantInt::get(SLC.getIntPtrType(), SrcLength+1), // copy nul term.
ConstantInt::get(Type::Int32Ty, 1) // alignment
};
new CallInst(SLC.get_memcpy(), Vals, 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;
}
} StrCatOptimizer;