[PATCH, rs6000] Fixing PR 67145

[David Edelsohn]

On Fri, Feb 26, 2016 at 12:08 AM, Richard Henderson <rth@redhat.com> wrote:
> It's the simplify-rtx.c portion of the patch that fixes the i686 regression.
>
> In the PR, Alan raises some good points, but I don't believe that we can
> address those for gcc6.  A new rtl reassoc optimization that takes loop
> invariance into account will have to wait.
>
> But we do need to take care of the rs6000 ice that results, and that's the
> bulk of the patch -- allowing CA to be sorted to any register of the plus
> chain.
>
> Some notes:
>
> ca_operand doesn't work as written, since CA_REGNO is not an available
> register, and thus doesn't satisfy register_operand.
>
> Is there any particular reason that subf<>3_carry_in_m1 was written with
> minus rather than plus like all of the other patterns?

Segher wrote the rs6000 carry infrastructure, so he's the best one to comment.

- David