src/compiler/nir/nir_lower_tex_shadow.c

/*
 * Copyright © Microsoft Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * on the rights to use, copy, modify, merge, publish, distribute, sub
 * license, and/or sell copies of the Software, and to permit persons to whom
 * the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "nir.h"
#include "nir_builder.h"
#include "nir_builtin_builder.h"

static bool
nir_lower_tex_shadow_filter(const nir_instr *instr,
                            UNUSED const void *_options)
{
   if (instr->type != nir_instr_type_tex)
      return false;

   /* To be consistent we also want to lower tex when we lower anything,
    * otherwise the differences in evaluating the shadow value might lead
    * to artifacts. */
   nir_tex_instr *tex = nir_instr_as_tex(instr);
   if (tex->op != nir_texop_txb &&
       tex->op != nir_texop_txl &&
       tex->op != nir_texop_txd &&
       tex->op != nir_texop_tex)
      return false;

   return tex->is_shadow;
}

static const struct glsl_type *
strip_shadow(const struct glsl_type *type)
{
   const struct glsl_type *new_type =
      glsl_sampler_type(
         glsl_get_sampler_dim(type),
         false, glsl_sampler_type_is_array(type),
         GLSL_TYPE_FLOAT);
   return new_type;
}

static const struct glsl_type *
strip_shadow_with_array(const struct glsl_type *type)
{
   if (glsl_type_is_array(type))
      return glsl_array_type(strip_shadow(glsl_without_array(type)),
                             glsl_get_length(type), 0);
   return strip_shadow(type);
}

typedef struct {
   unsigned n_states;
   enum compare_func *compare_func;
   nir_lower_tex_shadow_swizzle *tex_swizzles;
} sampler_state;

static nir_def *
nir_lower_tex_shadow_impl(nir_builder *b, nir_instr *instr, void *options)

{
   nir_tex_instr *tex = nir_instr_as_tex(instr);

   sampler_state *state = (sampler_state *)options;
   unsigned num_components = nir_tex_instr_result_size(tex);

   b->cursor = nir_after_instr(instr);
   tex->is_shadow = false;

   int comp_index = nir_tex_instr_src_index(tex, nir_tex_src_comparator);
   unsigned sampler_binding = tex->texture_index;

   nir_deref_instr *sampler_deref = NULL;
   nir_variable *sampler = NULL;

   int sampler_index = nir_tex_instr_src_index(tex, nir_tex_src_sampler_deref);
   if (sampler_index >= 0) {
      sampler_deref = nir_instr_as_deref(tex->src[sampler_index].src.ssa->parent_instr);
      sampler = nir_deref_instr_get_variable(sampler_deref);
      sampler_binding = sampler ? sampler->data.binding : 0;
   }

   /* NIR expects a vec4 result from the above texture instructions */
   nir_def_init(&tex->instr, &tex->def, 4, 32);

   nir_def *tex_r = nir_channel(b, &tex->def, 0);
   nir_def *cmp = tex->src[comp_index].src.ssa;

   int proj_index = nir_tex_instr_src_index(tex, nir_tex_src_projector);
   if (proj_index >= 0)
      cmp = nir_fmul(b, cmp, nir_frcp(b, tex->src[proj_index].src.ssa));

   nir_def *result =
      nir_compare_func(b,
                       sampler_binding < state->n_states ? state->compare_func[sampler_binding] : COMPARE_FUNC_ALWAYS,
                       cmp, tex_r);

   result = nir_b2f32(b, result);
   nir_def *one = nir_imm_float(b, 1.0);
   nir_def *zero = nir_imm_float(b, 0.0);

   nir_def *lookup[6] = { result, zero, zero, one, zero, one };
   nir_def *r[4] = { result, result, result, result };

   if (sampler_binding < state->n_states) {
      r[0] = lookup[state->tex_swizzles[sampler_binding].swizzle_r];
      r[1] = lookup[state->tex_swizzles[sampler_binding].swizzle_g];
      r[2] = lookup[state->tex_swizzles[sampler_binding].swizzle_b];
      r[3] = lookup[state->tex_swizzles[sampler_binding].swizzle_a];
   }

   result = nir_vec(b, r, num_components);

   if (sampler_index >= 0) {
      sampler->type = strip_shadow_with_array(sampler->type);
      sampler_deref->type = sampler->type;
   }

   tex->is_shadow = false;
   nir_tex_instr_remove_src(tex, comp_index);

   return result;
}

bool
nir_lower_tex_shadow(nir_shader *s,
                     unsigned n_states,
                     enum compare_func *compare_func,
                     nir_lower_tex_shadow_swizzle *tex_swizzles)
{
   sampler_state state = { n_states, compare_func, tex_swizzles };

   bool result =
      nir_shader_lower_instructions(s,
                                    nir_lower_tex_shadow_filter,
                                    nir_lower_tex_shadow_impl,
                                    &state);
   return result;
}