[Mesa-dev] [RFC PATCH] mesa: Replace _mesa_round_to_even() with roundeven().

[Matt Turner]

On Wed, Mar 11, 2015 at 3:13 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> On Wed, Mar 11, 2015 at 6:09 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> glibc uses roundsd/roundss in rint/f guarded by a runtime check. The
>> SSE code here just allows those instructions to be inlined.
>
> OK, as long as glibc would end up using the same rounding mode settings,
>
> Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>

Okay, so slight difference. It doesn't use the same rounding mode
settings, since rint() rounds in the current rounding direction it
uses rounds* with imm8=0x4 (current rounding direction) whereas we're
using rounds* with imm8=0x8 (round to nearest). We're assuming the
current rounding mode is to nearest, since that's the default and if
it weren't other things would go badly.

I don't know if your R-b stands in that case?