[llvm] [NFCI][WPD]Use unique string saver to store type id (PR #106932)

[Mingming Liu via llvm-commits]

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@@ -327,7 +327,20 @@ template <> struct MappingTraits<ModuleSummaryIndex> {
     if (!io.outputting())
       CustomMappingTraits<GlobalValueSummaryMapTy>::fixAliaseeLinks(
           index.GlobalValueMap);
-    io.mapOptional("TypeIdMap", index.TypeIdMap);
+
+    if (io.outputting()) {
+      io.mapOptional("TypeIdMap", index.TypeIdMap);
+    } else {
+      TypeIdSummaryMapTy TypeIdMap;
+      io.mapOptional("TypeIdMap", TypeIdMap);
+      for (auto &[TypeGUID, TypeIdSummaryMap] : TypeIdMap) {
+        // Save type id references in index and point TypeIdMap to use the
+        // references owned by index.
+        StringRef KeyRef = index.TypeIdSaver.save(TypeIdSummaryMap.first);
+        index.TypeIdMap.insert({TypeGUID, {KeyRef, TypeIdSummaryMap.second}});
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minglotus-6 wrote:

Before I figured out this way, I tried to change `CustomMappingTraits`. If I read correctly, the input/output methods don't take 'index' as a parameter, and 'TypeIdMap' doesn't have a pointer to 'index' either.

I updated the PR to 'move' `TypeIdSummaryMap.second` in the latest reply. yaml IO is likely not on the critical path, but std::move should be safe to invoke here.

https://github.com/llvm/llvm-project/pull/106932