etnaviv: nir: Legalize txd comparator

The hardware expects textureGrad (txd) shadow comparator to be
specified as the w component of the coordinate, rather than as a
separate comparator source.

Signed-off-by: Christian Gmeiner <cgmeiner@igalia.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35531>

src/gallium/drivers/etnaviv/etnaviv_nir_lower_texture.c

@@ -66,6 +66,48 @@ legalize_txd_derivatives(nir_builder *b, nir_tex_instr *tex, UNUSED void *data)
    return true;
 }
 
+static bool
+legalize_txd_comparator(nir_builder *b, nir_tex_instr *tex, UNUSED void *data)
+{
+   if (tex->op != nir_texop_txd)
+      return false;
+
+   if (!tex->is_shadow)
+      return false;
+
+   b->cursor = nir_before_instr(&tex->instr);
+
+   nir_def *comp = nir_steal_tex_src(tex, nir_tex_src_comparator);
+   assert(comp);
+
+   int coord_index = nir_tex_instr_src_index(tex, nir_tex_src_coord);
+   int ddx_index = nir_tex_instr_src_index(tex, nir_tex_src_ddx);
+   int ddy_index = nir_tex_instr_src_index(tex, nir_tex_src_ddy);
+
+   assert(coord_index >= 0);
+   assert(ddx_index >= 0);
+   assert(ddy_index >= 0);
+
+   nir_def *coord = tex->src[coord_index].src.ssa;
+   nir_def *ddx = tex->src[ddx_index].src.ssa;
+   nir_def *ddy = tex->src[ddy_index].src.ssa;
+
+   coord = nir_pad_vec4(b, coord);
+   coord = nir_vector_insert_imm(b, coord, comp, 3);
+
+   /* Make nir validation happy. */
+   ddx = nir_pad_vector(b, ddx, tex->is_array ? 3 : 4);
+   ddy = nir_pad_vector(b, ddy, tex->is_array ? 3 : 4);
+
+   nir_src_rewrite(&tex->src[coord_index].src, coord);
+   nir_src_rewrite(&tex->src[ddx_index].src, ddx);
+   nir_src_rewrite(&tex->src[ddy_index].src, ddy);
+
+   tex->coord_components = 4;
+
+   return true;
+}
+
 bool
 etna_nir_lower_texture(nir_shader *s, struct etna_shader_key *key)
 {
@@ -94,5 +136,8 @@ etna_nir_lower_texture(nir_shader *s, struct etna_shader_key *key)
    NIR_PASS(progress, s, nir_shader_tex_pass, legalize_txd_derivatives,
       nir_metadata_control_flow, NULL);
 
+   NIR_PASS(progress, s, nir_shader_tex_pass, legalize_txd_comparator,
+      nir_metadata_control_flow, NULL);
+
    return progress;
 }