I am not sure about this. There is an earlier if statement in the loop
that does a 'return' instead of a break (or continue) and there is a
return in the 'else' part of the if that sets must_annul. Both of these
are inside the loop that looks at all the instructions in the sequence
'seq'. I think the code is looking at all the instructions in the
sequence and if any of them fail one of the tests in the loop (in this
case require annulling) then we can't handle any of the instructions in
the sequence and so we return immediately without putting any of the
instructions from 'seq' in the delay slot. I believe a frame related
instruction in an annulled branch needs to be handled that way too.