[Mesa-dev] [PATCH 3/4] radeonsi: add more unlikely() uses into si_draw_vbo

[Michel Dänzer]

On 06/09/16 08:33 PM, Marek Olšák wrote:
> On Sep 6, 2016 12:03 PM, "Michel Dänzer" <michel at daenzer.net
> <mailto:michel at daenzer.net>> wrote:
>> On 06/09/16 06:04 PM, Marek Olšák wrote:
>> > On Tue, Sep 6, 2016 at 3:54 AM, Michel Dänzer <michel at daenzer.net
> <mailto:michel at daenzer.net>> wrote:
>> >> On 06/09/16 07:46 AM, Marek Olšák wrote:
>> >>> From: Marek Olšák <marek.olsak at amd.com <mailto:marek.olsak at amd.com>>
>> >>
>> >> Did you measure any significant performance boost with this change?
>> >
>> > I didn't measure anything.
>> >
>> >> Otherwise, using (un)likely can be bad because it can defeat the CPU's
>> >> branch prediction, which tends to be pretty good these days.
>> >
>> > I'm not an expert on that, but it doesn't seem to be the case
>> > according to other people's comments here.
>>
>> My main point (which Gustaw seems to agree with) is that (un)likely
>> should only be used when measurements show that they have a positive
> effect.
> 
> I agree with you, but do you always measure the effect of unlikely? I
> almost never do and I just use it instinctively like most people do. Due
> to our manpower constraints, we can't even afford to measure performance
> for much bigger changes than this.

So let's spend our manpower on more important things than (un)likely
annotations. :)


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer