Tighten operand checking on memory barrier instructions.

llvm-svn: 137176
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 34b3e62..e7a6b89 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -3814,6 +3814,7 @@
 def memb_opt : Operand<i32> {
   let PrintMethod = "printMemBOption";
   let ParserMatchClass = MemBarrierOptOperand;
+  let DecoderMethod = "DecodeMemBarrierOption";
 }
 
 // memory barriers protect the atomic sequences