Fix a warning from gcc-4.0 (from the ppc buildbot).

llvm-svn: 109605
diff --git a/llvm/utils/TableGen/NeonEmitter.cpp b/llvm/utils/TableGen/NeonEmitter.cpp
index 3516d31..a754ce2 100644
--- a/llvm/utils/TableGen/NeonEmitter.cpp
+++ b/llvm/utils/TableGen/NeonEmitter.cpp
@@ -1016,6 +1016,8 @@
       throw "unhandled type!";
       break;
   }
+  assert(0 && "unreachable");
+  return 0;
 }
 
 /// runHeader - Emit a file with sections defining: