[llvm] [SampleFDO] Match functions with the same base function name (PR #126688)

[Lei Wang via llvm-commits]

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@@ -727,6 +728,33 @@ bool SampleProfileMatcher::functionMatchesProfileHelper(
   // two sequences are.
   float Similarity = 0.0;
 
+  // Match the functions if they have the same base name(after demangling) and
+  // skip the similarity check.
+  ItaniumPartialDemangler Demangler;
+  // Helper lambda to demangle and get the base name. If the demangling failed,
+  // return an empty string.
+  auto GetBaseName = [&](StringRef FName) {
+    auto FunctionName = FName.str();
+    if (Demangler.partialDemangle(FunctionName.c_str()))
+      return std::string();
+    constexpr size_t MaxBaseNameSize = 4096;
+    char BaseNameBuf[MaxBaseNameSize] = {};
+    size_t BaseNameSize = MaxBaseNameSize;
+    char *BaseNamePtr =
+        Demangler.getFunctionBaseName(BaseNameBuf, &BaseNameSize);
+    return (BaseNamePtr && BaseNameSize)
+               ? std::string(BaseNamePtr, BaseNameSize)
+               : std::string();
+  };
+  auto IRBaseName = GetBaseName(IRFunc.getName());
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wlei-llvm wrote:

Good point. It doesn't include the parameters. I was thinking to make the check in the early place so that if it passes, we can skip the later anchor LCS which is a heavy check. 

>If not, I wonder if we should treat base name comparison as a fall back only when there is no anchor in functions?

I see, but then it doesn't work for the case I mentioned in other comment, where all the anchors are mismatched but the function still match. Seems like a tradeoff 
(1) mismatch between overload functions vs (2) mismatch with all parameter changes. 


https://github.com/llvm/llvm-project/pull/126688