Re: [Mesa-dev] [PATCH v2 1/4] nir: set default lod to texture opcodes that needed it but don't provide it

[Samuel Iglesias Gonsálvez]

On Tuesday, October 10, 2017 11:53:27 AM CEST Eric Anholt wrote:
> Samuel Iglesias Gonsálvez <sigles...@igalia.com> writes:
> > Signed-off-by: Samuel Iglesias Gonsálvez <sigles...@igalia.com>
> > ---
> > 
> >  src/compiler/nir/nir_lower_tex.c | 68
> >  ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68
> >  insertions(+)
> > 
> > diff --git a/src/compiler/nir/nir_lower_tex.c
> > b/src/compiler/nir/nir_lower_tex.c index 65681decb1c..d3380710405 100644
> > --- a/src/compiler/nir/nir_lower_tex.c
> > +++ b/src/compiler/nir/nir_lower_tex.c
> > @@ -717,6 +717,52 @@ linearize_srgb_result(nir_builder *b, nir_tex_instr
> > *tex)> 
> >                                    result->parent_instr);
> >  
> >  }
> > 
> > +static void
> > +set_default_lod(nir_builder *b, nir_tex_instr *tex)
> > +{
> > +   b->cursor = nir_before_instr(&tex->instr);
> > +
> > +   /* We are going to emit the same texture but adding a default LOD.
> > +    */
> > +   int num_srcs = tex->num_srcs + 1;
> > +   nir_tex_instr *new = nir_tex_instr_create(b->shader, num_srcs);
> > +
> > +   new->op = tex->op;
> > +   new->sampler_dim = tex->sampler_dim;
> > +   new->texture_index = tex->texture_index;
> > +   new->dest_type = tex->dest_type;
> > +   new->is_array = tex->is_array;
> > +   new->is_shadow = tex->is_shadow;
> > +   new->is_new_style_shadow = tex->is_new_style_shadow;
> > +   new->sampler_index = tex->sampler_index;
> > +   new->texture = nir_deref_var_clone(tex->texture, new);
> > +   new->sampler = nir_deref_var_clone(tex->sampler, new);
> > +   new->coord_components = tex->coord_components;
> 
> Couldn't we just make a new srcs array of num_srcs+1, memcpy the old
> srcs/types over, add our new use of the immediate 0 lod to it by
> manipulating the immediate's uses list

This is an interesting approach.  I have done the following:

   b->cursor = nir_before_instr(&tex->instr);

   nir_tex_src *srcs = ralloc_array(tex, nir_tex_src, tex->num_srcs + 1);
   memcpy(srcs, tex->src, sizeof(nir_tex_src) * tex->num_srcs);

   srcs[tex->num_srcs + 1].src = nir_src_for_ssa(nir_imm_int(b, 0));
   srcs[tex->num_srcs + 1].src_type = nir_tex_src_lod;
   tex->num_srcs++;
   ralloc_free(tex->src);
   tex->src = srcs;

However, it crashes when validating ssa def. I also tried calling 
nir_ssa_def_rewrite_uses() but I am not sure how to do it for this case, 
probably I am missing something.

How can I manipulate the immediate's uses list for this case? Can you provide 
an example?

Sam

> , and free the old list?  It seems
> less fragile to me than needing to update this path if we add a new
> texture flag.

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