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Re: [PATCH, rs6000] Prefer vnand/vperm over vnor/vperm for Power8
- From: David Edelsohn <dje dot gcc at gmail dot com>
- To: Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 8 Apr 2014 15:52:37 -0400
- Subject: Re: [PATCH, rs6000] Prefer vnand/vperm over vnor/vperm for Power8
- Authentication-results: sourceware.org; auth=none
- References: <1396984045 dot 5401 dot 125 dot camel at gnopaine>
On Tue, Apr 8, 2014 at 3:07 PM, Bill Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Hi,
>
> Recently I posted a patch to use vnor to invert the permute control
> vector for little-endian permutes. It's come to my attention that, when
> available, the vnand instruction should be used in preference to vnor
> for possible future processor exploitation. This patch checks for
> availability of vnand and uses it instead. It also removes earlier use
> of emit_move_insn in this logic where that was not appropriate.
>
> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no
> regressions. Is this ok for trunk?
>
> I would also like to backport the combined patch to the FSF 4.8 branch,
> if you feel that is appropriate. Please let me know.
>
> Thanks,
> Bill
>
>
> 2014-04-08 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
>
> * config/rs6000/rs6000.c (rs6000_expand_vector_set): Use vnand
> instead of vnor to exploit possible fusion opportunity in the
> future.
> (altivec_expand_vec_perm_const_le): Likewise.
Okay for trunk and 4.8.
Thanks, David