[Mesa-dev] [PATCH] freedreno/ir3: Make imageStore use num components from image format

[Eduardo Lima Mitev]

On 12/18/18 9:05 AM, Eduardo Lima Mitev wrote:
> On 12/17/18 10:02 PM, Ilia Mirkin wrote:
>> Note that the format may not be known. I suspect that falls into your
>> "default" case.
>>
> 
> Hi Ilia,
> 
> while on GLES profiles the format qualifier must be declared for all
> image variables, it is true that core profiles allow to omit it for
> writeonly-qualified images.
> 
> I guess we can add a special case for GL_NONE to the switch, that also
> returns 4 components, to at least not break current behavior if image
> format is not known. What do you think?
> 

Thinking a bit more about this, if we care about core profile then there
are more GL formats to consider apart from those supported by GLES 3.1.

However, since image format layout qualifiers were introduced in core
4.20, I don't think we should care for now. So I would leave the patch
as-is and fail the assert on unknown formats.

Eduardo

> Eduardo
> 
>> On Mon, Dec 17, 2018 at 3:41 PM Eduardo Lima Mitev <elima at igalia.com> wrote:
>>>
>>> emit_intrinsic_store_image() is always using 4 components when
>>> collecting registers for the value. When image has less than
>>> 4 components (e.g, r32f, r32i, r32ui) this results in extra mov
>>> instructions.
>>>
>>> This patch uses the actual number of components from the image format.
>>>
>>> For example, in a shader like:
>>>
>>> layout (r32f, binding=0) writeonly uniform imageBuffer u_image;
>>> ...
>>> void main(void) {
>>>    ...
>>>    imageStore (u_image, some_offset, vec4(1.0));
>>>    ...
>>> }
>>>
>>> instruction count is reduced in at least 3 instructions (note image
>>> format is r32f, 1 component only).
>>>
>>> This obviously reduces register pressure as well.
>>> ---
>>>  src/freedreno/ir3/ir3_compiler_nir.c | 34 ++++++++++++++++++++++++++--
>>>  1 file changed, 32 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/src/freedreno/ir3/ir3_compiler_nir.c b/src/freedreno/ir3/ir3_compiler_nir.c
>>> index 85f14f354d2..cc00602c249 100644
>>> --- a/src/freedreno/ir3/ir3_compiler_nir.c
>>> +++ b/src/freedreno/ir3/ir3_compiler_nir.c
>>> @@ -1251,6 +1251,35 @@ emit_intrinsic_load_image(struct ir3_context *ctx, nir_intrinsic_instr *intr,
>>>         ir3_split_dest(b, dst, sam, 0, 4);
>>>  }
>>>
>>> +/* Get the number of components of the different image formats supported
>>> + * by the GLES 3.1 spec.
>>> + */
>>> +static unsigned
>>> +get_num_components_for_glformat(GLuint format)
>>> +{
>>> +       switch (format) {
>>> +       case GL_R32F:
>>> +       case GL_R32I:
>>> +       case GL_R32UI:
>>> +               return 1;
>>> +
>>> +       case GL_RGBA32F:
>>> +       case GL_RGBA16F:
>>> +       case GL_RGBA8:
>>> +       case GL_RGBA8_SNORM:
>>> +       case GL_RGBA32I:
>>> +       case GL_RGBA16I:
>>> +       case GL_RGBA8I:
>>> +       case GL_RGBA32UI:
>>> +       case GL_RGBA16UI:
>>> +       case GL_RGBA8UI:
>>> +               return 4;
>>> +
>>> +       default:
>>> +               assert(!"Unsupported GL format for image");
>>> +       }
>>> +}
>>> +
>>>  /* src[] = { deref, coord, sample_index, value }. const_index[] = {} */
>>>  static void
>>>  emit_intrinsic_store_image(struct ir3_context *ctx, nir_intrinsic_instr *intr)
>>> @@ -1262,6 +1291,7 @@ emit_intrinsic_store_image(struct ir3_context *ctx, nir_intrinsic_instr *intr)
>>>         struct ir3_instruction * const *coords = ir3_get_src(ctx, &intr->src[1]);
>>>         unsigned ncoords = get_image_coords(var, NULL);
>>>         unsigned tex_idx = get_image_slot(ctx, nir_src_as_deref(intr->src[0]));
>>> +       unsigned ncomp = get_num_components_for_glformat(var->data.image.format);
>>>
>>>         /* src0 is value
>>>          * src1 is coords
>>> @@ -1276,10 +1306,10 @@ emit_intrinsic_store_image(struct ir3_context *ctx, nir_intrinsic_instr *intr)
>>>          */
>>>
>>>         stib = ir3_STIB(b, create_immed(b, tex_idx), 0,
>>> -                       ir3_create_collect(ctx, value, 4), 0,
>>> +                       ir3_create_collect(ctx, value, ncomp), 0,
>>>                         ir3_create_collect(ctx, coords, ncoords), 0,
>>>                         offset, 0);
>>> -       stib->cat6.iim_val = 4;
>>> +       stib->cat6.iim_val = ncomp;
>>>         stib->cat6.d = ncoords;
>>>         stib->cat6.type = get_image_type(var);
>>>         stib->cat6.typed = true;
>>> --
>>> 2.19.2
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>
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