instcombine: Migrate strchr and strrchr optimizations
This patch migrates the strchr and strrchr optimizations from the
simplify-libcalls pass into the instcombine library call simplifier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165875 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 2c8fb8b..2876369 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -320,6 +320,88 @@
}
};
+struct StrChrOpt : public LibCallOptimization {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ // Verify the "strchr" function prototype.
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 2 ||
+ FT->getReturnType() != B.getInt8PtrTy() ||
+ FT->getParamType(0) != FT->getReturnType() ||
+ !FT->getParamType(1)->isIntegerTy(32))
+ return 0;
+
+ Value *SrcStr = CI->getArgOperand(0);
+
+ // If the second operand is non-constant, see if we can compute the length
+ // of the input string and turn this into memchr.
+ ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+ if (CharC == 0) {
+ // These optimizations require DataLayout.
+ if (!TD) return 0;
+
+ uint64_t Len = GetStringLength(SrcStr);
+ if (Len == 0 || !FT->getParamType(1)->isIntegerTy(32))// memchr needs i32.
+ return 0;
+
+ return EmitMemChr(SrcStr, CI->getArgOperand(1), // include nul.
+ ConstantInt::get(TD->getIntPtrType(*Context), Len),
+ B, TD, TLI);
+ }
+
+ // Otherwise, the character is a constant, see if the first argument is
+ // a string literal. If so, we can constant fold.
+ StringRef Str;
+ if (!getConstantStringInfo(SrcStr, Str))
+ return 0;
+
+ // Compute the offset, make sure to handle the case when we're searching for
+ // zero (a weird way to spell strlen).
+ size_t I = CharC->getSExtValue() == 0 ?
+ Str.size() : Str.find(CharC->getSExtValue());
+ if (I == StringRef::npos) // Didn't find the char. strchr returns null.
+ return Constant::getNullValue(CI->getType());
+
+ // strchr(s+n,c) -> gep(s+n+i,c)
+ return B.CreateGEP(SrcStr, B.getInt64(I), "strchr");
+ }
+};
+
+struct StrRChrOpt : public LibCallOptimization {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ // Verify the "strrchr" function prototype.
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 2 ||
+ FT->getReturnType() != B.getInt8PtrTy() ||
+ FT->getParamType(0) != FT->getReturnType() ||
+ !FT->getParamType(1)->isIntegerTy(32))
+ return 0;
+
+ Value *SrcStr = CI->getArgOperand(0);
+ ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+
+ // Cannot fold anything if we're not looking for a constant.
+ if (!CharC)
+ return 0;
+
+ StringRef Str;
+ if (!getConstantStringInfo(SrcStr, Str)) {
+ // strrchr(s, 0) -> strchr(s, 0)
+ if (TD && CharC->isZero())
+ return EmitStrChr(SrcStr, '\0', B, TD, TLI);
+ return 0;
+ }
+
+ // Compute the offset.
+ size_t I = CharC->getSExtValue() == 0 ?
+ Str.size() : Str.rfind(CharC->getSExtValue());
+ if (I == StringRef::npos) // Didn't find the char. Return null.
+ return Constant::getNullValue(CI->getType());
+
+ // strrchr(s+n,c) -> gep(s+n+i,c)
+ return B.CreateGEP(SrcStr, B.getInt64(I), "strrchr");
+ }
+};
+
} // End anonymous namespace.
namespace llvm {
@@ -340,6 +422,8 @@
// String and memory library call optimizations.
StrCatOpt StrCat;
StrNCatOpt StrNCat;
+ StrChrOpt StrChr;
+ StrRChrOpt StrRChr;
void initOptimizations();
public:
@@ -364,6 +448,8 @@
// String and memory library call optimizations.
Optimizations["strcat"] = &StrCat;
Optimizations["strncat"] = &StrNCat;
+ Optimizations["strchr"] = &StrChr;
+ Optimizations["strrchr"] = &StrRChr;
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {