Coverity issues

[andrewbird]

There are 4 issues in codegen-sim.c that apparently are caused by overlapping memory. Since you can't always see the proper Coverity tool and I think the email only emits entries for new issues, I post a screenshot so that you may these from the 2022 run of Coverity.

[stsp]

This is probably a false-positive.
Its just a sign-extension op: we
assign from smaller field to a
larger one of the same register.

Please try to experiment with
different syntaxes. For example:
DR1.d = (signed)DR1.bs.bl; // for signed case
DR1.d = DR1.d & 0xff; // for unsigned case
and so on, to see what would
please coverity.