Index: llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
+++ llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
@@ -777,9 +777,7 @@
     if (!VI)
       return;
 
-    // We need to make sure all variants of the symbol are scanned, alias can
-    // make one (but not all) alive.
-    if (llvm::all_of(VI.getSummaryList(),
+    if (llvm::any_of(VI.getSummaryList(),
                      [](const std::unique_ptr<llvm::GlobalValueSummary> &S) {
                        return S->isLive();
                      }))
@@ -819,12 +817,23 @@
   while (!Worklist.empty()) {
     auto VI = Worklist.pop_back_val();
     for (auto &Summary : VI.getSummaryList()) {
-      GlobalValueSummary *Base = Summary->getBaseObject();
-      // Set base value live in case it is an alias.
-      Base->setLive(true);
-      for (auto Ref : Base->refs())
+      if (auto *AS = dyn_cast<AliasSummary>(Summary.get())) {
+        // If this is an alias, visit the aliasee VI to ensure that all copies
+        // are marked live and it is added to the worklist for further
+        // processing of its references.
+        // FIXME: The aliasee GUID is only populated in the summary when we
+        // read them from bitcode, which is currently the only way we can
+        // get here (we don't yet support reading the summary index directly
+        // from LLVM assembly code in tools that can perform a thin link).
+        // If that ever changes, the below call to getAliaseGUID will assert.
+        visit(Index.getValueInfo(AS->getAliaseeGUID()));
+        continue;
+      }
+
+      Summary->setLive(true);
+      for (auto Ref : Summary->refs())
         visit(Ref);
-      if (auto *FS = dyn_cast<FunctionSummary>(Base))
+      if (auto *FS = dyn_cast<FunctionSummary>(Summary.get()))
         for (auto Call : FS->calls())
           visit(Call.first);
     }