[llvm] [SampleFDO] Improve stale profile matching by diff algorithm (PR #87375)

[via llvm-commits]

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@@ -122,15 +122,153 @@ void SampleProfileMatcher::findProfileAnchors(
   }
 }
 
+MyersDiff::DiffResult
+MyersDiff::longestCommonSequence(const std::vector<Anchor> &A,
+                                 const std::vector<Anchor> &B) const {
+  int32_t N = A.size(), M = B.size(), Max = N + M;
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WenleiHe wrote:

General comment: can we replace A,B,M,N,X,Y,V names with something meaningful and more readable? Also Max is not really Max but total size of two sequence. 

https://github.com/llvm/llvm-project/pull/87375