[Mesa-dev] [PATCH 1/5] mesa: add ARB_derivative_control extension bit

[Ian Romanick]

On 08/14/2014 12:00 AM, Matt Turner wrote:
> On Wed, Aug 13, 2014 at 11:44 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> On Wed, Aug 13, 2014 at 9:52 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>>> ---
>>>  src/mesa/main/extensions.c | 1 +
>>>  src/mesa/main/mtypes.h     | 1 +
>>>  2 files changed, 2 insertions(+)
>>>
>>> diff --git a/src/mesa/main/extensions.c b/src/mesa/main/extensions.c
>>> index 8658ca8..3dcb199 100644
>>> --- a/src/mesa/main/extensions.c
>>> +++ b/src/mesa/main/extensions.c
>>> @@ -101,6 +101,7 @@ static const struct extension extension_table[] = {
>>>     { "GL_ARB_depth_buffer_float",                  o(ARB_depth_buffer_float),                  GL,             2008 },
>>>     { "GL_ARB_depth_clamp",                         o(ARB_depth_clamp),                         GL,             2003 },
>>>     { "GL_ARB_depth_texture",                       o(ARB_depth_texture),                       GLL,            2001 },
>>> +   { "GL_ARB_derivative_control",                  o(ARB_derivative_control),                  GLC,            2014 },
>>
>> No reason to be core-only that I can see.
> 
> I guess we can just leave it up to the drivers to turn on the
> extension if GLSL >= 4.00? Seems ugly. Also seems like a pretty
> arbitrary requirement.

I've also made a query in Khronos about this.  In my (brief) research, I
couldn't find any reason why it should be limited to 4.0+.  There were
some changes in the spec about derivitaves versus flow control, but I
was pretty sure those changes happened before 4.0.  Since this spec has
interactions with flow control, it would make sense to limit it to GLSL
versions with the updated language.

I think we implement the updated requirements even in out 3.x drivers,
so this may not be a problem in practice.

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