[Mesa-dev] i965/radeonsi use STD430 packing of UBOs by default

Marek Olšák maraeo at gmail.com
Sun Aug 20 22:58:56 UTC 2017

On Mon, Aug 21, 2017 at 12:52 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> On 21/08/17 03:25, Marek Olšák wrote:
>> On Thu, Aug 17, 2017 at 1:02 PM, Timothy Arceri <tarceri at itsqueeze.com>
>> wrote:
>>> Shared (the default) and packed layouts are decided by the
>>> implementation.
>>> Currently we just pack them using the std140 layout. This change makes it
>>> so
>>> we use the slightly more compact std430 layout on i965 and radeonsi.
>>> I doubt this will help many games, but it still seems worth implementing.
>>> I could only find shaders for a single game in my shader-db collection
>>> where STD140 layout wasn't explicitly defined for UBOs, and even there
>>> it was using vec4s so there would be no improvement.
>> Why having a separate codepath that only 2 drivers will use If it
>> doesn't improve any app?
> I didn't say it doesn't improve any apps, presumably something uses the
> shared and packed layout provided by the spec. I just didn't seen it in my
> quick search of my shader-db collection.
> Ignoring how many apps use it, it's not much of a separate path it mostly
> just reuses the existing paths for SSBOs. Also if we can get SNB fixed up
> and add support to the remaining Gallium drivers that support ubos than we
> can drop the old paths entirely.

All Gallium drivers will never support it (unless you intent to add
support by yourself).

> For radeonsi once I get LOAD working with my uniform packing series that
> would just leave immediates using the fetch_constant() code path.

What about Nine and VDPAU/VAAPI/OpenMAX also using CONST?


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