There was a bug where we would hit an assertion if 'Q' was used as a
constraint.
I also removed hardcoded register names to prefer regexes so the tests
don't break when the register allocator changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289325 91177308-0d34-0410-b5e6-96231b3b80d8