DwarfCompileUnit: Fix another assertion failure on malformed input
that is not rejected by the Verifier.

Thanks to Björn Pettersson for providing a reproducer!

llvm-svn: 331535
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 7d6d45e..952b0d9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -212,6 +212,7 @@
   void addUnsignedConstant(const APInt &Value);
 
   bool isMemoryLocation() const { return LocationKind == Memory; }
+  bool isUnknownLocation() const { return LocationKind == Unknown; }
 
   /// Lock this down to become a memory location description.
   void setMemoryLocationKind() {