[clang] [CIR] Recognize strlen in the IdiomRecognizer pass (PR #210400)

[Erich Keane via cfe-commits]

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@@ -50,4 +88,14 @@ def CIR_StdFindOp : CIR_StdOp<"find",
   }];
 }
 
+def CIR_StrLenOp : CIR_CStdLibOp<"strlen",
+  (ins CIR_PtrToChar8Type:$string),
+  (outs CIR_AnyFundamentalUIntType:$result)> {
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erichkeane wrote:

I wonder if we should just do these analysis/function recognizing with the FE?  As a part of our 'lower function' we could decide if it is the 'right' function?  

It seems like a lot of extra work here to recognize these when the FE has the info.

https://github.com/llvm/llvm-project/pull/210400