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instcombine: Migrate strncpy optimizations

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This patch migrates the strncpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167102 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Meador Inge
2012-10-31 03:33:00 +00:00
parent 5b2c4dc5f8
commit a0885fb882
6 changed files with 175 additions and 90 deletions
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49
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@@ -628,6 +628,53 @@ struct StpCpyOpt: public LibCallOptimization {
}
};
struct StrNCpyOpt : public LibCallOptimization {
virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != B.getInt8PtrTy() ||
!FT->getParamType(2)->isIntegerTy())
return 0;
Value *Dst = CI->getArgOperand(0);
Value *Src = CI->getArgOperand(1);
Value *LenOp = CI->getArgOperand(2);
// See if we can get the length of the input string.
uint64_t SrcLen = GetStringLength(Src);
if (SrcLen == 0) return 0;
--SrcLen;
if (SrcLen == 0) {
// strncpy(x, "", y) -> memset(x, '\0', y, 1)
B.CreateMemSet(Dst, B.getInt8('\0'), LenOp, 1);
return Dst;
}
uint64_t Len;
if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(LenOp))
Len = LengthArg->getZExtValue();
else
return 0;
if (Len == 0) return Dst; // strncpy(x, y, 0) -> x
// These optimizations require DataLayout.
if (!TD) return 0;
// Let strncpy handle the zero padding
if (Len > SrcLen+1) return 0;
Type *PT = FT->getParamType(0);
// strncpy(x, s, c) -> memcpy(x, s, c, 1) [s and c are constant]
B.CreateMemCpy(Dst, Src,
ConstantInt::get(TD->getIntPtrType(PT), Len), 1);
return Dst;
}
};
} // End anonymous namespace.
namespace llvm {
@@ -654,6 +701,7 @@ class LibCallSimplifierImpl {
StrNCmpOpt StrNCmp;
StrCpyOpt StrCpy;
StpCpyOpt StpCpy;
StrNCpyOpt StrNCpy;
void initOptimizations();
public:
@@ -684,6 +732,7 @@ void LibCallSimplifierImpl::initOptimizations() {
Optimizations["strncmp"] = &StrNCmp;
Optimizations["strcpy"] = &StrCpy;
Optimizations["stpcpy"] = &StpCpy;
Optimizations["strncpy"] = &StrNCpy;
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {