memcpy performance regressions 2.19 -> 2.24(5)

[H.J. Lu]

On Tue, May 23, 2017 at 1:57 PM, Erich Elsen <eriche@google.com> wrote:
> Maybe there's room for both?
>
> Setting the cpu_features would affect everything; it would be useful
> to be able to target only specific (and very important) routines.

I prefer to do the cpu_features first.  If it turns out not
sufficient, we then do
the IFUNC implementation.

> On Tue, May 23, 2017 at 1:46 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, May 23, 2017 at 1:39 PM, Erich Elsen <eriche@google.com> wrote:
>>> I was also thinking that it might be nice to have a TUNABLE that sets
>>> the implementation of memcpy directly.  It would be easier to do this
>>> if memcpy.S was memcpy.c.  Attached is a patch that does the
>>> conversion but doesn't add the tunables.  How would you feel about
>>> this?  It has no runtime impact, probably increases the size slightly,
>>> and makes the code easier to read / modify.
>>>
>>
>> It depends on how far you want to go.  We can add TUNABLE support
>> to each IFUNC implementation or we can add TUNABLE support to
>> cpu_features to update processor features.  I prefer latter.
>>
>>
>> --
>> H.J.



-- 
H.J.