[Mesa-dev] [PATCH v2 1/5] nir/lower_tex: Add a way to lower TXS(non-0-LOD) instructions

[Boris Brezillon]

Hi Jason,

On Tue, 18 Jun 2019 09:45:56 -0500
Jason Ekstrand <jason at jlekstrand.net> wrote:

> On Tue, Jun 18, 2019 at 2:38 AM Boris Brezillon <
> boris.brezillon at collabora.com> wrote:  
> 
> > The V3D driver has an open-coded solution for this, and we need the
> > same thing for Panfrost, so let's add a generic way to lower TXS(LOD)
> > into max(TXS(0) >> LOD, 1).
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> > ---
> > Changes in v2:
> > * Use == 0 instead of !
> > * Rework the minification logic as suggested by Jason
> > * Assign cursor pos at the beginning of the function
> > * Patch the LOD just after retrieving the old value
> > ---
> >  src/compiler/nir/nir.h           |  6 +++++
> >  src/compiler/nir/nir_lower_tex.c | 46 ++++++++++++++++++++++++++++++++
> >  2 files changed, 52 insertions(+)
> >
> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> > index 4270df565111..8972b4af7480 100644
> > --- a/src/compiler/nir/nir.h
> > +++ b/src/compiler/nir/nir.h
> > @@ -3426,6 +3426,12 @@ typedef struct nir_lower_tex_options {
> >      */
> >     bool lower_txd_clamp_if_sampler_index_not_lt_16;
> >
> > +   /**
> > +    * If true, lower nir_texop_txs with a non-0-lod into nir_texop_txs
> > with
> > +    * 0-lod followed by a nir_ishr.
> > +    */
> > +   bool lower_txs_lod;
> > +
> >     /**
> >      * If true, apply a .bagr swizzle on tg4 results to handle Broadcom's
> >      * mixed-up tg4 locations.
> > diff --git a/src/compiler/nir/nir_lower_tex.c
> > b/src/compiler/nir/nir_lower_tex.c
> > index 53719017a87f..6f82ca5f06db 100644
> > --- a/src/compiler/nir/nir_lower_tex.c
> > +++ b/src/compiler/nir/nir_lower_tex.c
> > @@ -978,6 +978,47 @@ lower_tg4_offsets(nir_builder *b, nir_tex_instr *tex)
> >     return true;
> >  }
> >
> > +static bool
> > +nir_lower_txs_lod(nir_builder *b, nir_tex_instr *tex)
> > +{
> > +   int lod_idx = nir_tex_instr_src_index(tex, nir_tex_src_lod);
> > +   if (lod_idx < 0 ||
> > +       (nir_src_is_const(tex->src[lod_idx].src) &&
> > +        nir_src_as_int(tex->src[lod_idx].src) == 0))
> > +      return false;
> > +
> > +   unsigned dest_size = nir_tex_instr_dest_size(tex);
> > +
> > +   b->cursor = nir_before_instr(&tex->instr);
> > +   nir_ssa_def *lod = nir_ssa_for_src(b, tex->src[lod_idx].src, 1);
> > +
> > +   /* Replace the non-0-LOD in the initial TXS operation by a 0-LOD. */
> > +   nir_instr_rewrite_src(&tex->instr, &tex->src[lod_idx].src,
> > +                         nir_src_for_ssa(nir_imm_int(b, 0)));
> > +
> > +   /* TXS(LOD) = max(TXS(0) >> LOD, 1) */
> > +   b->cursor = nir_after_instr(&tex->instr);
> > +   nir_ssa_def *minified = nir_imax(b, nir_ushr(b, &tex->dest.ssa, lod),
> > +                                    nir_imm_int(b, 1));
> > +
> > +   /* Make sure the component encoding the array size (if any) is not
> > +    * minified.
> > +    */
> > +   if (tex->is_array) {
> > +      nir_ssa_def *comp[3];
> >  
> 
> Mind throwing in a quick assert?
> 
> assert(dest_size <= ARRAY_SIZE(comp));
> 
> With that added,
> 
> Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

The patch has been merged already, but I'll add that in a follow-up
patch.

Thanks,

Boris