[IR] Avoid repeated hash lookups (NFC) (#120848)

Author: kazutakahirata

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -1711,10 +1711,9 @@ class ModuleSummaryIndex {
                        GlobalValue::GUID OrigGUID) {
     if (OrigGUID == 0 || ValueGUID == OrigGUID)
       return;
-    if (OidGuidMap.count(OrigGUID) && OidGuidMap[OrigGUID] != ValueGUID)
-      OidGuidMap[OrigGUID] = 0;
-    else
-      OidGuidMap[OrigGUID] = ValueGUID;
+    auto [It, Inserted] = OidGuidMap.try_emplace(OrigGUID, ValueGUID);
+    if (!Inserted && It->second != ValueGUID)
+      It->second = 0;
   }
 
   /// Find the summary for ValueInfo \p VI in module \p ModuleId, or nullptr if