[ThinLTO][WPD] Simplify check for local summary for efficiency (NFCI) (llvm#164859)

Use the new HasLocal flag to avoid looking through all summaries to see
if there is a local copy.

Author: teresajohnson

llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp

@@ -1408,9 +1408,8 @@ bool DevirtIndex::trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot,
 
   // If the summary list contains multiple summaries where at least one is
   // a local, give up, as we won't know which (possibly promoted) name to use.
-  for (const auto &S : TheFn.getSummaryList())
-    if (GlobalValue::isLocalLinkage(S->linkage()) && Size > 1)
-      return false;
+  if (TheFn.hasLocal() && Size > 1)
+    return false;
 
   // Collect functions devirtualized at least for one call site for stats.
   if (PrintSummaryDevirt || AreStatisticsEnabled())