[Mesa-dev] [PATCH 2/6] New unary opcodes for ARB_shader_bit_encoding support.

[Kenneth Graunke]

On 05/01/2012 10:24 AM, Eric Anholt wrote:
> On Tue, 1 May 2012 08:52:51 +0200, Olivier Galibert<galibert at pobox.com>  wrote:
>> On Mon, Apr 30, 2012 at 02:21:51PM -0700, Eric Anholt wrote:
>>> GLSL 1.30 is already on for gen6+.  You can force 1.30 for your purposes
>>> if needed on older hardware with the environment variable:
>>>
>>> MESA_GLSL_VERSION_OVERRIDE=130
>>>
>>> (Also, there's MESA_EXTENSION_OVERRIDE="+GL_ARB_texture_buffer_object
>>> +GL_ARB_uniform_buffer_object" or MESA_GL_VERSION_OVERRIDE for poking at
>>> new extension support before the driver's ready)
>>
>> Thanks.  The only intel hardware I have is a GM45 (8086:2a43) which is
>> seems qualifies at gen4.  I rememeber from my casual reading of the
>> hardware docs that it seemed 3.3-capable.  Did I miss something?
>
> Issues with GL 3.0 pre-gen6:
> - No MSAA.  You'd have to fake it with supersampling.
> - Doesn't support filtering on 32-bit float textures.
> - transform feedback is different and needs backporting.
> - GLSL noperspective/smooth/flat keywords are handled very
>    differently in the SF.

Also, support for gl_ClipDistance pre-Gen6 would be a lot of work, as 
Gen4-5 used a programmable clipping stage (?!?), and we'd basically have 
to rewrite all the clipping programs.  That's one of the major reasons 
why 1.30 is off pre-Gen6.

I'll go ahead and write the patch, since exposing it without 1.30 
doesn't make a lot of sense.