FileCheckize these testcases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154281 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Assembler/invalid_cast.ll b/test/Assembler/invalid_cast.ll
index c5b082b..f682835 100644
--- a/test/Assembler/invalid_cast.ll
+++ b/test/Assembler/invalid_cast.ll
@@ -1,4 +1,6 @@
-; RUN: not llvm-as < %s |& grep {invalid cast opcode}
+; RUN: not llvm-as < %s |& FileCheck %s
+
+; CHECK: invalid cast opcode for cast from '<4 x i64>' to '<3 x i8>'
 
 define <3 x i8> @foo(<4 x i64> %x) {
   %y = trunc <4 x i64> %x to <3 x i8>