Re: [PATCH][rs6000] avoid using unaligned vsx or lxvd2x/stxvd2x for memcpy/memmove inline expansion

[Aaron Sawdey <acsawdey at linux dot ibm dot com>]

On 12/20/18 3:51 AM, Segher Boessenkool wrote:
> On Wed, Dec 19, 2018 at 01:53:05PM -0600, Aaron Sawdey wrote:
>> Because of POWER9 dd2.1 issues with certain unaligned vsx instructions
>> to cache inhibited memory, here is a patch that keeps memmove (and memcpy)
>> inline expansion from doing unaligned vector or using vector load/store
>> other than lvx/stvx. More description of the issue is here:
>>
>> https://patchwork.ozlabs.org/patch/814059/
>>
>> OK for trunk if bootstrap/regtest ok?
> 
> Okay, but see below.
> 
[snip]
> 
> This is extraordinarily clumsy :-)  Maybe something like:
> 
> static rtx
> gen_lvx_v4si_move (rtx dest, rtx src)
> {
>   gcc_assert (!(MEM_P (dest) && MEM_P (src));
>   gcc_assert (GET_MODE (dest) == V4SImode && GET_MODE (src) == V4SImode);
>   if (MEM_P (dest))
>     return gen_altivec_stvx_v4si_internal (dest, src);
>   else if (MEM_P (src))
>     return gen_altivec_lvx_v4si_internal (dest, src);
>   else
>     gcc_unreachable ();
> }
> 
> (Or do you allow VOIDmode for src as well?)  Anyway, at least get rid of
> the useless extra variable.

I think this should be better:

static rtx
gen_lvx_v4si_move (rtx dest, rtx src)
{
  gcc_assert ((MEM_P (dest) && !MEM_P (src)) || (MEM_P (src) && !MEM_P(dest)));
  gcc_assert (GET_MODE (dest) == V4SImode && GET_MODE (src) == V4SImode);
  if (MEM_P (dest))
      return gen_altivec_stvx_v4si_internal (dest, src);
  else if (MEM_P (src))
      return gen_altivec_lvx_v4si_internal (dest, src);
  gcc_unreachable ();
}

I'll commit after I re-regstrap.

Thanks!
   Aaron

-- 
Aaron Sawdey, Ph.D.  acsawdey@linux.vnet.ibm.com
050-2/C113  (507) 253-7520 home: 507/263-0782
IBM Linux Technology Center - PPC Toolchain