instcombine: Migrate strcmp and strncmp optimizations
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
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 5ce5843..bd28ec3 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -402,6 +402,101 @@
}
};
+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 @@
StrNCatOpt StrNCat;
StrChrOpt StrChr;
StrRChrOpt StrRChr;
+ StrCmpOpt StrCmp;
+ StrNCmpOpt StrNCmp;
void initOptimizations();
public:
@@ -443,6 +540,8 @@
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;