[llvm] Reland "[Transforms] LoopIdiomRecognize recognize strlen and wcslen #108985" (PR #132572)

[Alexander Kornienko via llvm-commits]

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@@ -295,7 +313,8 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L) {
 
   // Disable loop idiom recognition if the function's name is a common idiom.
   StringRef Name = L->getHeader()->getParent()->getName();
-  if (Name == "memset" || Name == "memcpy")
+  if (Name == "memset" || Name == "memcpy" || Name == "strlen" ||
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alexfh wrote:

This doesn't work, if the corresponding function is in a namespace. But I get it's a rather niche case, which is better addressed by `-fno-builtin-strlen` or `-ffreestanding`.

https://github.com/llvm/llvm-project/pull/132572