[Mesa-dev] [PATCH] mesa: expose ARB_compute_shader with compat profile

[Ian Romanick]

On 06/07/2016 04:28 PM, Nanley Chery wrote:
> On Wed, May 25, 2016 at 12:52:38PM -0700, Matt Turner wrote:
>> On Wed, May 25, 2016 at 12:17 PM, Samuel Pitoiset
>> <samuel.pitoiset at gmail.com> wrote:
>>> This fixes use of compute shaders with some NVIDIA GL 4.3 samples which
>>> require a compat profile.
>>
>> I'm confused.
>>
>> The samples you're talking about... use 4.3 compatibility? We already
>> don't support compatibility profile, so you presumably have to hack
>> that on.
>>
>> The ARB_compute_shader extension spec says it requires 4.2, and we
>> don't expose 4.2 with the compatibility profile. I think you should
>> have some justification for why it's safe to expose in compatibility
>> profile, since that's a pretty big change. Or, you don't want to
>> expose it in compatibility but you need this patch to enable it with
>> the 4.2-compat hack enabled...?
>>
>> Strangely, ARB_compute_shader says "GLL, GLC" in extensions_table.h,
>> but it's only core-enabled on my glxinfo.
> 
> Because extensions_table.h has "GLL" in the ARB_compute_shader entry,
> the extension is already exposed in all compatibility contexts. This
> patch fixes the bug of advertising the extension externally, but
> internally failing to do the logic required by the extension.

Thanks for clearing that up, Nanley.  That makes sense.  I believe the
commit message is misleading, and that led to some confusion.  I think a
better commit message is:

    mesa: Let compute shaders work in compatibility profiles

    The extension is already advertised in compatibility profile, but
    the _mesa_has_compute_shaders only returns true in core profile.
    If we advertise it, we should allow it to work.

Now, whether or not we should advertise the extension in compatibility
profiles is an orthogonal question.  We discussed this when compute
shaders first landed, and we decided to enable it.  I don't know of a
strong reason to change that, but I'm not married to it.

Either way, with the above change to the commit message, this patch is

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

> - Nanley
> 
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