Revert "Fix a bug that prevents global variables from having a DW_OP_deref."

This reverts commit r3309704 while investigating bot breakage.

llvm-svn: 330993
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index d893db4..2eb0157 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -230,9 +230,8 @@
         addOpAddress(*Loc, Sym);
       }
     }
-    // Global variables attached to symbols are memory locations.
-    DwarfExpr->setMemoryLocationKind();
-    DwarfExpr->addExpression(Expr);
+    if (Expr)
+      DwarfExpr->addExpression(Expr);
   }
   if (Loc)
     addBlock(*VariableDIE, dwarf::DW_AT_location, DwarfExpr->finalize());