[llvm] [SampleProfileMatcher] Fix backward matching of non-anchor locations (PR #190118)

[Grigory Pastukhov via llvm-commits]

================
@@ -234,10 +234,12 @@ SampleProfileMatcher::longestCommonSequence(const AnchorList &AnchorList1,
 void SampleProfileMatcher::matchNonCallsiteLocs(
     const LocToLocMap &MatchedAnchors, const AnchorMap &IRAnchors,
     LocToLocMap &IRToProfileLocationMap) {
-  auto InsertMatching = [&](const LineLocation &From, const LineLocation &To) {
+  auto UpdateMatching = [&](const LineLocation &From, const LineLocation &To) {
     // Skip the unchanged location mapping to save memory.
     if (From != To)
-      IRToProfileLocationMap.insert({From, To});
+      IRToProfileLocationMap.insert_or_assign(From, To);
+    else
+      IRToProfileLocationMap.erase(From);
----------------
grigorypas wrote:

Maybe I am missing something... We start with empty map. If statement above should prevent adding pairs (or updating) when From = To. It looks like we should never have From = To in the map. 

https://github.com/llvm/llvm-project/pull/190118