Fold strlen(expr ? "str1" : "str2") to x ? len1 : len2. This fires about 330 times in a bootstrap of clang.
llvm-svn: 207828
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 903fbb5..0fd1858 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -784,10 +784,25 @@
if (uint64_t Len = GetStringLength(Src))
return ConstantInt::get(CI->getType(), Len-1);
+ // strlen(x?"foo":"bars") --> x ? 3 : 4
+ if (SelectInst *SI = dyn_cast<SelectInst>(Src)) {
+ uint64_t LenTrue = GetStringLength(SI->getTrueValue());
+ uint64_t LenFalse = GetStringLength(SI->getFalseValue());
+ if (LenTrue && LenFalse) {
+ Context->emitOptimizationRemark(
+ "simplify-libcalls", *Caller, SI->getDebugLoc(),
+ "folded strlen(select) to select of constants");
+ return B.CreateSelect(SI->getCondition(),
+ ConstantInt::get(CI->getType(), LenTrue-1),
+ ConstantInt::get(CI->getType(), LenFalse-1));
+ }
+ }
+
// strlen(x) != 0 --> *x != 0
// strlen(x) == 0 --> *x == 0
if (isOnlyUsedInZeroEqualityComparison(CI))
return B.CreateZExt(B.CreateLoad(Src, "strlenfirst"), CI->getType());
+
return nullptr;
}
};