Revert "[LLD][ThinLTO] Handle GUID collision in import global processing"

This reverts commit cc0b964.

The commit is causing a failure in internal testing. Will recommit with
a fix later.

Author: teresajohnson

llvm/lib/Transforms/Utils/FunctionImportUtils.cpp

@@ -239,17 +239,11 @@ void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
   // propagateConstants hasn't been run. We can't internalize GV
   // in such case.
   if (!GV.isDeclaration() && VI && ImportIndex.withGlobalValueDeadStripping()) {
-    if (GlobalVariable *V = dyn_cast<GlobalVariable>(&GV)) {
-      // We can have more than one local with the same GUID, in the case of
-      // same-named locals in different but same-named source files that were
-      // compiled in their respective directories (so the source file name
-      // and resulting GUID is the same). Find the one in this module.
-      auto* GVS = dyn_cast<GlobalVarSummary>(
-          ImportIndex.findSummaryInModule(VI, M.getModuleIdentifier()));
-      // At this stage "maybe" is "definitely"
-      if (GVS && (GVS->maybeReadOnly() || GVS->maybeWriteOnly()))
-        V->addAttribute("thinlto-internalize");
-    }
+    const auto &SL = VI.getSummaryList();
+    auto *GVS = SL.empty() ? nullptr : dyn_cast<GlobalVarSummary>(SL[0].get());
+    // At this stage "maybe" is "definitely"
+    if (GVS && (GVS->maybeReadOnly() || GVS->maybeWriteOnly()))
+      cast<GlobalVariable>(&GV)->addAttribute("thinlto-internalize");
   }
 
   bool DoPromote = false;