[Mesa-dev] [PATCH v2 2/7] nir/lower_tex: add lowering for texture gradient on cube maps

[Iago Toral]

On Mon, 2016-12-12 at 23:14 -0800, Kenneth Graunke wrote:
> On Monday, December 12, 2016 2:11:43 PM PST Iago Toral Quiroga wrote:
> > 
> > This is ported from the Intel lowering pass that we use with GLSL
> > IR.
> > The NIR pass only handles cube maps, not shadow samplers, which are
> > also lowered for gen < 8 on Intel hardware. We will add support for
> > that in a later patch, at which point we should be able to remove
> > the GLSL IR lowering pass.
> > 
> > v2:
> > - added a helper to retrieve ddx/ddy parameters (Ken)
> > - No need to make size.z=1.0, we are only using component x anyway
> > (Iago)
> > ---
> >  src/compiler/nir/nir.h           |   5 +
> >  src/compiler/nir/nir_lower_tex.c | 265
> > +++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 270 insertions(+)
> > 
> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> > index 544d4ba..600e3d6 100644
> > --- a/src/compiler/nir/nir.h
> > +++ b/src/compiler/nir/nir.h
> > @@ -2394,6 +2394,11 @@ typedef struct nir_lower_tex_options {
> >      * of the texture are lowered to linear.
> >      */
> >     unsigned lower_srgb;
> > +
> > +   /**
> > +    * If true, lower nir_texop_txd on cube maps with
> > nir_texop_txl.
> > +    */
> > +   bool lower_txd_cube_map;
> >  } nir_lower_tex_options;
> >  
> >  bool nir_lower_tex(nir_shader *shader,
> > diff --git a/src/compiler/nir/nir_lower_tex.c
> > b/src/compiler/nir/nir_lower_tex.c
> > index ccca59b..da024e2 100644
> > --- a/src/compiler/nir/nir_lower_tex.c
> > +++ b/src/compiler/nir/nir_lower_tex.c
> > @@ -305,6 +305,265 @@ lower_yx_xuxv_external(nir_builder *b,
> > nir_tex_instr *tex)
> >  }
> >  
> >  static void
> > +get_ddx_ddy(nir_tex_instr *tex, nir_ssa_def **ddx, nir_ssa_def
> > **ddy)
> > +{
> > +   for (int i = 0; i < tex->num_srcs; i++) {
> > +      switch (tex->src[i].src_type) {
> > +      case nir_tex_src_ddx:
> > +         *ddx = tex->src[i].src.ssa;
> > +         break;
> > +      case nir_tex_src_ddy:
> > +         *ddy = tex->src[i].src.ssa;
> > +         break;
> > +      default:
> > +         break;
> > +      }
> > +   }
> > +}
> > +
> > +/*
> > + * Emits a textureLod operation used to replace an existing
> > + * textureGrad instruction.
> > + */
> > +static void
> > +replace_gradient_with_lod(nir_builder *b, nir_ssa_def *lod,
> > nir_tex_instr *tex)
> > +{
> > +   /* Check whether we need projector, shadow comparitor or offset
> > */
> > +   int comparitor_index = -1;
> > +   int projector_index = -1;
> > +   int offset_index = -1;
> > +   int extra_srcs = 0;
> > +   for (int i = 0; i < tex->num_srcs; i++) {
> > +      switch (tex->src[i].src_type) {
> > +      case nir_tex_src_projector:
> > +         projector_index = i;
> > +         extra_srcs++;
> > +         break;
> > +      case nir_tex_src_offset:
> > +         offset_index = i;
> > +         extra_srcs++;
> > +         break;
> > +      case nir_tex_src_comparitor:
> > +         comparitor_index = i;
> > +         extra_srcs++;
> > +         break;
> > +      default:
> > +         break;
> > +      }
> > +   }
> This looks correct now, but I liked Eric's suggestion from last time
> -
> you can actually just do:
> 
>    int comparitor_idx = nir_tex_instr_src_index(tex,
> nir_tex_src_comparitor);
>    int projector_idx = nir_tex_instr_src_index(tex,
> nir_tex_src_projector);
>    int offset_idx = nir_tex_instr_src_index(tex, nir_tex_src_offset);
> 
>    /* we replace ddx and ddy with a single value: lod */
>    int num_srcs = tex->num_srcs - 1;
> 
>    nir_ssa_def *dPdx =
>       tex->src[nir_tex_src_index(tex, nir_tex_src_ddx)].src.ssa;
>    nir_ssa_def *dPdy =
>       tex->src[nir_tex_src_index(tex, nir_tex_src_ddy)].src.ssa;
> 
> Either way, this series is:
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

Ah, I had missed that suggestion, that's much better. I'll fix it up
and push the series. Thanks for the review!

Iago

> I don't need to see a third posting - feel free to fix up any last
> things before pushing.  Thanks for doing this!