This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Truncate optimisation question
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: gcc at gcc dot gnu dot org, Kyrill Tkachov <kyrylo dot tkachov at arm dot com>
- Date: Fri, 06 Dec 2013 08:42:14 +0000
- Subject: Re: Truncate optimisation question
- Authentication-results: sourceware.org; auth=none
- References: <529E1D60 dot 3030902 at arm dot com> <15068471 dot klO546xLQ2 at polaris> <87pppcyh0w dot fsf at sandifor-thinkpad dot stglab dot manchester dot uk dot ibm dot com> <4377730 dot 9ZxEXnUCx1 at polaris>
Eric Botcazou <ebotcazou@adacore.com> writes:
>> Well, I think making the simplify-rtx code conditional on the target
>> would be the wrong way to go. If we really can't live with it being
>> unconditional then I think we should revert it. But like I say I think
>> it would be better to make combine recognise the redundancy even with
>> the new form. (Or as I say, longer term, not to rely on combine to
>> eliminate redundant extensions.) But I don't have time to do that myself...
>
> It helps x86 so we won't revert it. My fear is that we'll need to add code in
> other places to RISCify back the result of this "simplification".
Sorry, realised I didn't respond to this yesterday. I wasn't suggesting
we just revert and walk away. ISTR the original suggestion was to patch
combine instead of simplify-rtx.c, so we could back to that.
Thanks,
Richard