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Re: [PATCH, rs6000] Fixing PR 67145
- From: David Edelsohn <dje dot gcc at gmail dot com>
- To: Richard Henderson <rth at redhat dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Alan Modra <amodra at gmail dot com>
- Date: Fri, 26 Feb 2016 07:28:49 -0500
- Subject: Re: [PATCH, rs6000] Fixing PR 67145
- Authentication-results: sourceware.org; auth=none
- References: <56CFDDD0 dot 6030503 at redhat dot com>
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