[Mesa-dev] [PATCH 08/11] mesa: Implement the GL entry points defined by ARB_shader_image_load_store.

[Francisco Jerez]

Fredrik Höglund <fredrik at kde.org> writes:

> On Tuesday 26 November 2013, Francisco Jerez wrote:
>> Fredrik Höglund <fredrik at kde.org> writes:
>> >[...]
>> >> +}
>> >> +
>> >> +void GLAPIENTRY
>> >> +_mesa_MemoryBarrier(GLbitfield barriers)
>> >> +{
>> >> +   GET_CURRENT_CONTEXT(ctx);
>> >> +
>> >> +   if (ctx->Driver.MemoryBarrier)
>> >> +      ctx->Driver.MemoryBarrier(ctx, barriers);
>> >> +}
>> >
>> > Is this the best place to implement this entry point?
>> > It's not specific to ARB_shader_image_load_store.
>> 
>> Right.  It's also going to be used for shader storage blocks, which we
>> don't support yet -- right now it's only going to have an effect on
>> shader images, though I'm fine with moving the definition somewhere else
>> now, if you have a better suggestion.  Any ideas?
>
> And ARB_buffer_storage.
>
Ehm...  Yes and no.  The point of glMemoryBarrier() is to serialize
image writes and atomics with other operations that might manipulate the
texture data bound to an image unit [or, if
ARB_shader_storage_buffer_object is supported, to serialize storage
block writes and atomics with other operations].  ARB_buffer_storage
interacts with it because its persistent mappings are among those memory
operations that can be serialized with shader storage blocks and images.

> I think I would put it in texturebarrier.c and rename the file to
> memorybarrier.c. _mesa_TextureBarrierNV can be changed to use the
> same driver hook as _mesa_MemoryBarrier.
>

Well, in unextended GL glMemoryBarrier doesn't necessarily have any
interaction with fragment shader outputs, so glTextureBarrierNV() is not
necessarily equivalent to glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT).
We probably want to keep both driver hooks around.  Other than that I'm
OK with renaming texturebarrier.c and moving the definition of
glMemoryBarrier, though I don't think it's extremely urgent because
glMemoryBarrier is specific to ARB_shader_image_load_store at this
point.  Feel free to send a follow-up patch series making the necessary
changes.

> Fredrik
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