[Hexagon] Adding double-logic on predicate instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225018 91177308-0d34-0410-b5e6-96231b3b80d8
Generalize even further, for ARM comment syntax (@)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225019 91177308-0d34-0410-b5e6-96231b3b80d8