[Mesa-dev] [RFC PATCH 1/2] r600/sb: Set flags for GROUP_BARRIER instruction and force it into slot X

[Dave Airlie]

On 11 January 2018 at 06:13, Gert Wollny <gw.fossdev at gmail.com> wrote:
> Am Mittwoch, den 10.01.2018, 16:36 +0100 schrieb Gert Wollny:
>> This seems to satisfy the sb optimizer, i.e. no regressions in the
>> piglits compared to disabling sb for tesselation shaders with
>> barriers but enabling them in general.
>> ---
>
> Actually, it seems this is not enough, at least for Tomb Raider which
> uses one tessellation control shader with a barrier. The optimizer
> reorders the LDS instructions around the barrier in a way that in the
> optimized version there are more reads before it than in the original
> byte code.
>
> The number of writes is the same though, and as far as I can tell from
> the TGSI, the values written to LDS before the barrier are not read
> back within the shader - which makes me wonder whether the barrier is
> actually necessary.

probably needs a dep on the LDS_RW stuff.

Dave.