Index: llvm/trunk/include/llvm/MC/MCParser/MCAsmParser.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCParser/MCAsmParser.h
+++ llvm/trunk/include/llvm/MC/MCParser/MCAsmParser.h
@@ -55,8 +55,7 @@
                                           InlineAsmIdentifierInfo &Info,
                                           bool IsUnevaluatedContext) = 0;
   virtual StringRef LookupInlineAsmLabel(StringRef Identifier, SourceMgr &SM,
-                                         SMLoc Location, bool Create)
-  { return nullptr; }
+                                         SMLoc Location, bool Create) = 0;
 
   virtual bool LookupInlineAsmField(StringRef Base, StringRef Member,
                                     unsigned &Offset) = 0;