Add support for parsing dmb/dsb instructions

llvm-svn: 125055
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 01ae5df..961649b 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -3191,6 +3191,7 @@
 
 def memb_opt : Operand<i32> {
   let PrintMethod = "printMemBOption";
+  let ParserMatchClass = MemBarrierOptOperand;
 }
 
 // memory barriers protect the atomic sequences