[llvm] [NFC][InstrProf]Factor out getCanonicalName to compute the canonical name given a pgo name. (PR #81547)

[Teresa Johnson via llvm-commits]

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@@ -449,6 +449,19 @@ class InstrProfSymtab {
     return "** External Symbol **";
   }
 
+  // Returns the canonial name of the given PGOName. In a canonical name, all
+  // suffixes that begins with "." except ".__uniq." are stripped.
+  // FIXME: Unify this with `FunctionSamples::getCanonicalFnName`. And both
+  // should probably preserve `.specialized.<NSpecs>` suffix now that
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teresajohnson wrote:

It isn't clear to me why we would want to preserve .specialized, since presumably those specialized copies are created after PGO annotation / matching.

https://github.com/llvm/llvm-project/pull/81547