Index: lib/CodeGen/GlobalMerge.cpp
===================================================================
--- lib/CodeGen/GlobalMerge.cpp
+++ lib/CodeGen/GlobalMerge.cpp
@@ -280,6 +280,8 @@
       // users, so look through ConstantExpr...
       Use *UI, *UE;
       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
+        if (CE->use_empty())
+          continue;
         UI = &*CE->use_begin();
         UE = nullptr;
       } else if (isa<Instruction>(U.getUser())) {