[Mesa-dev] IROUND() issue

[Roland Scheidegger]

Am 19.05.2012 02:43, schrieb Kurt Roeckx:
> On Sat, May 19, 2012 at 02:19:36AM +0200, Roland Scheidegger wrote:
>> Am 18.05.2012 23:55, schrieb Kurt Roeckx:
>>> On Fri, May 18, 2012 at 09:11:38AM -0700, Jose Fonseca wrote:
>>>>
>>>> It sounds a sensible plan, but I wonder if the multiple iround
>>>> versions are really worth it: SSE2 is guaranteed in x64, so we
>>>> could just start requiring SSE2 on x86, and only use the C for
>>>> other platforms.
>>>
>>> Is the "start requiring SSE2 on x86" a typo for x64?
>>>
>>> I still use x86 hardware that doesn't support sse2.
>> Would your hardware also not support sse?
> 
> The one I'm using now does support sse but no sse2.
> 
> What do you think about using cpuid for this?
> 

Runtime cpu detection isn't really suitable for simple helpers like
IROUND which are used in a lot of places and supposed to map to very few
if not a single instruction, you'd have to use that somewhere in the
calling functions adding a lot of complexity. Noone's going to do that
probably.
Though at least linux distributions still compile without -msse as they
generally right now seem to require i686 (with cmov) but not sse. So
removing legacy x87 assembly might be premature.

Roland