[Mesa-dev] [PATCH 5/6] i965/draw: Do resolves properly for textures used by TXF

[Jason Ekstrand]

On Thu, Jan 11, 2018 at 1:48 AM, Iago Toral <itoral at igalia.com> wrote:

> On Wed, 2018-01-10 at 11:22 -0800, Jason Ekstrand wrote:
> > ---
> >  src/mesa/drivers/dri/i965/brw_draw.c | 41
> > ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 41 insertions(+)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_draw.c
> > b/src/mesa/drivers/dri/i965/brw_draw.c
> > index 4945dec..9fd44e4 100644
> > --- a/src/mesa/drivers/dri/i965/brw_draw.c
> > +++ b/src/mesa/drivers/dri/i965/brw_draw.c
> > @@ -40,6 +40,7 @@
> >  #include "swrast_setup/swrast_setup.h"
> >  #include "drivers/common/meta.h"
> >  #include "util/bitscan.h"
> > +#include "util/bitset.h"
> >
> >  #include "brw_blorp.h"
> >  #include "brw_draw.h"
> > @@ -371,6 +372,20 @@ intel_disable_rb_aux_buffer(struct brw_context
> > *brw,
> >     return found;
> >  }
> >
> > +static void
> > +mark_textures_used_for_txf(BITSET_WORD *used_for_txf,
> > +                           const struct gl_program *prog)
> > +{
> > +   if (!prog)
> > +      return;
> > +
> > +   unsigned mask = prog->SamplersUsed & prog-
> > >info.textures_used_by_txf;
> > +   while (mask) {
> > +      int s = u_bit_scan(&mask);
> > +      BITSET_SET(used_for_txf, prog->SamplerUnits[s]);
> > +   }
> > +}
> > +
> >  /**
> >   * \brief Resolve buffers before drawing.
> >   *
> > @@ -386,6 +401,18 @@ brw_predraw_resolve_inputs(struct brw_context
> > *brw, bool rendering)
> >     memset(brw->draw_aux_buffer_disabled, 0,
> >            sizeof(brw->draw_aux_buffer_disabled));
> >
> > +   BITSET_DECLARE(used_for_txf, MAX_COMBINED_TEXTURE_IMAGE_UNITS);
> > +   memset(used_for_txf, 0, sizeof(used_for_txf));
> > +   if (rendering) {
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >VertexProgram._Current);
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >TessCtrlProgram._Current);
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >TessEvalProgram._Current);
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >GeometryProgram._Current);
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >FragmentProgram._Current);
> > +   } else {
> > +      mark_textures_used_for_txf(used_for_txf, ctx-
> > >ComputeProgram._Current);
> > +   }
> > +
> >     /* Resolve depth buffer and render cache of each enabled texture.
> > */
> >     int maxEnabledUnit = ctx->Texture._MaxEnabledTexImageUnit;
> >     for (int i = 0; i <= maxEnabledUnit; i++) {
> > @@ -422,6 +449,20 @@ brw_predraw_resolve_inputs(struct brw_context
> > *brw, bool rendering)
> >                                      min_layer, num_layers,
> >                                      disable_aux);
> >
> > +      /* If any programs are using it with texelFetch, we may need
> > to also do
> > +       * a prepare with an sRGB format to ensure texelFetch works
> > "properly".
> > +       */
>
> I am not sure I understand this. The only way that txf_format and
> view_format can be different is if the texture format is sRGB and the
> user has selected GL_SKIP_DECODE_EXT, right? If the user selected that,
> it would mean that they do not want sRGB decoded data when sampling,
> but I understand that is what they would get, since we are preparing
> the MT with the sRGB format in this case. What am I missing?
>

The utterly insane rules around texelFetch in EXT_texture_sRGB_decode. :-)
I'd quote them here but it involves a table so that may not come out well
in e-mail.  The short version is that, if you use texelFetch,
GL_SKIP_DECODE_EXT is ignored because it's part of the sampler and
texelFetch doesn't use a sampler.  It's utterly insane but somehow that's
where "design by committee" got us.  The fallout is that if we see a
texelFetch, we need to do intel_miptree_prepare_texture with both sRGB and
UNORM formats.


> > +      if (BITSET_TEST(used_for_txf, i)) {
> > +         enum isl_format txf_format =
> > +            translate_tex_format(brw, tex_obj->_Format,
> > GL_DECODE_EXT);
> > +         if (txf_format != view_format) {
> > +            intel_miptree_prepare_texture(brw, tex_obj->mt,
> > txf_format,
> > +                                          min_level, num_levels,
> > +                                          min_layer, num_layers,
> > +                                          disable_aux);
> > +         }
> > +      }
> > +
> >        brw_cache_flush_for_read(brw, tex_obj->mt->bo);
> >
> >        if (tex_obj->base.StencilSampling ||
>
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