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instcombine: Migrate strcmp and strncmp optimizations

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165915 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Meador Inge
2012-10-15 03:47:37 +00:00
parent baf522ab5f
commit a239c2e6a7
10 changed files with 351 additions and 274 deletions
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99
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -402,6 +402,101 @@ struct StrRChrOpt : public LibCallOptimization {
}
};
struct StrCmpOpt : public LibCallOptimization {
virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strcmp" function prototype.
FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 ||
!FT->getReturnType()->isIntegerTy(32) ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != B.getInt8PtrTy())
return 0;
Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
if (Str1P == Str2P) // strcmp(x,x) -> 0
return ConstantInt::get(CI->getType(), 0);
StringRef Str1, Str2;
bool HasStr1 = getConstantStringInfo(Str1P, Str1);
bool HasStr2 = getConstantStringInfo(Str2P, Str2);
// strcmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2)
return ConstantInt::get(CI->getType(), Str1.compare(Str2));
if (HasStr1 && Str1.empty()) // strcmp("", x) -> -*x
return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
CI->getType()));
if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
// strcmp(P, "x") -> memcmp(P, "x", 2)
uint64_t Len1 = GetStringLength(Str1P);
uint64_t Len2 = GetStringLength(Str2P);
if (Len1 && Len2) {
// These optimizations require DataLayout.
if (!TD) return 0;
return EmitMemCmp(Str1P, Str2P,
ConstantInt::get(TD->getIntPtrType(*Context),
std::min(Len1, Len2)), B, TD, TLI);
}
return 0;
}
};
struct StrNCmpOpt : public LibCallOptimization {
virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
// Verify the "strncmp" function prototype.
FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 ||
!FT->getReturnType()->isIntegerTy(32) ||
FT->getParamType(0) != FT->getParamType(1) ||
FT->getParamType(0) != B.getInt8PtrTy() ||
!FT->getParamType(2)->isIntegerTy())
return 0;
Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
if (Str1P == Str2P) // strncmp(x,x,n) -> 0
return ConstantInt::get(CI->getType(), 0);
// Get the length argument if it is constant.
uint64_t Length;
if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getArgOperand(2)))
Length = LengthArg->getZExtValue();
else
return 0;
if (Length == 0) // strncmp(x,y,0) -> 0
return ConstantInt::get(CI->getType(), 0);
if (TD && Length == 1) // strncmp(x,y,1) -> memcmp(x,y,1)
return EmitMemCmp(Str1P, Str2P, CI->getArgOperand(2), B, TD, TLI);
StringRef Str1, Str2;
bool HasStr1 = getConstantStringInfo(Str1P, Str1);
bool HasStr2 = getConstantStringInfo(Str2P, Str2);
// strncmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2) {
StringRef SubStr1 = Str1.substr(0, Length);
StringRef SubStr2 = Str2.substr(0, Length);
return ConstantInt::get(CI->getType(), SubStr1.compare(SubStr2));
}
if (HasStr1 && Str1.empty()) // strncmp("", x, n) -> -*x
return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
CI->getType()));
if (HasStr2 && Str2.empty()) // strncmp(x, "", n) -> *x
return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
return 0;
}
};
} // End anonymous namespace.
namespace llvm {
@ -423,6 +518,8 @@ class LibCallSimplifierImpl {
StrNCatOpt StrNCat;
StrChrOpt StrChr;
StrRChrOpt StrRChr;
StrCmpOpt StrCmp;
StrNCmpOpt StrNCmp;
void initOptimizations();
public:
@ -443,6 +540,8 @@ void LibCallSimplifierImpl::initOptimizations() {
Optimizations["__stpcpy_chk"] = &StrCpyChk;
Optimizations["__strncpy_chk"] = &StrNCpyChk;
Optimizations["__stpncpy_chk"] = &StrNCpyChk;
Optimizations["strcmp"] = &StrCmp;
Optimizations["strncmp"] = &StrNCmp;
// String and memory library call optimizations.
Optimizations["strcat"] = &StrCat;