[Mesa-dev] [PATCH] glsl: always do sqrt(abs()) and inversesqrt(abs())

[Ilia Mirkin]

On Tue, Jan 10, 2017 at 12:51 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> On Tue, Jan 10, 2017 at 9:48 AM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
>>
>> I'll be honest, I'm not a fan... Given that D3D10 has one defined
>> behavior, D3D9 has another, and GL doesn't specify, I don't really think we
>> should be making a global change to all drivers to do the D3D9 behavior just
>> to fix one app.  Sure, other apps probably have the same bug, but are we
>> going to have apps that expect the D3D10 behavior that we've now explicitly
>> made not work?
>>
>> If we're going to hack around an app bug, I would really rather see it
>> behind a driconf option rather than a global change to driver behavior.
>> Even better, it'd be cool if we could see the app get fixed. (Yes, I know
>> that's not likely).
>
>
> As a quick addendum, this won't actually hurt our performance (at least not
> on modern hardware) because we can do source modifiers on SQRT and RSQ.

Same on NVIDIA.