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Re: [PATCH, rs6000] More efficient vector permute for little endian
- 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: Fri, 21 Mar 2014 09:39:59 -0400
- Subject: Re: [PATCH, rs6000] More efficient vector permute for little endian
- Authentication-results: sourceware.org; auth=none
- References: <1395365894 dot 3599 dot 35 dot camel at gnopaine>
On Thu, Mar 20, 2014 at 9:38 PM, Bill Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Hi,
>
> The original workaround for vector permute on a little endian platform
> includes subtracting each element of the permute control vector from 31.
> Because the upper 3 bits of each element are unimportant, this was
> implemented as subtracting the whole vector from a splat of -1. On
> reflection this can be done more efficiently with a vector nor
> operation. This patch makes that change.
>
> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no
> regressions. Is this ok for trunk?
>
> Thanks,
> Bill
>
>
> 2014-03-20 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
>
> * config/rs6000/rs6000.c (rs6000_expand_vector_set): Generate a
> pattern for vector nor instead of subtract from splat(-1).
> (altivec_expand_vec_perm_const_le): Likewise.
Okay.
Thanks, David