simplify-libcalls: fold strncmp(x, y, 1) -> memcmp(x, y, 1)
The memcmp will be optimized further and even the pathological case
'strstr(x, "x") == x' generates optimal code now.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106097 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index f562a1b..3ae79ee 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -342,6 +342,9 @@
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->getOperand(3), B, TD);
+
std::string Str1, Str2;
bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
bool HasStr2 = GetConstantStringInfo(Str2P, Str2);