src/compiler/nir/nir_normalize_cubemap_coords.c

/*
 * Copyright © 2015 Intel 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
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * 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 NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS 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.
 *
 * Authors:
 *    Jason Ekstrand <jason@jlekstrand.net>
 */

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

/*
 * Lower cubemap coordinate to have normalized coordinates where the largest
 * magnitude component is -1.0 or 1.0.
 */
static bool
normalize_cubemap_coords(nir_builder *b, nir_instr *instr, void *data)
{
   if (instr->type != nir_instr_type_tex)
      return false;

   nir_tex_instr *tex = nir_instr_as_tex(instr);
   if (tex->sampler_dim != GLSL_SAMPLER_DIM_CUBE)
      return false;

   b->cursor = nir_before_instr(instr);

   int idx = nir_tex_instr_src_index(tex, nir_tex_src_coord);
   if (idx < 0)
      return false;

   nir_ssa_def *orig_coord =
      nir_ssa_for_src(b, tex->src[idx].src, nir_tex_instr_src_size(tex, idx));
   assert(orig_coord->num_components >= 3);

   nir_ssa_def *orig_xyz = nir_trim_vector(b, orig_coord, 3);
   nir_ssa_def *norm = nir_fmax_abs_vec_comp(b, orig_xyz);
   nir_ssa_def *normalized = nir_fmul(b, orig_coord, nir_frcp(b, norm));

   /* Array indices don't have to be normalized, so make a new vector
    * with the coordinate's array index untouched.
    */
   if (tex->coord_components == 4) {
      normalized = nir_vector_insert_imm(b, normalized,
                                         nir_channel(b, orig_coord, 3), 3);
   }

   nir_instr_rewrite_src_ssa(instr, &tex->src[idx].src, normalized);
   return true;
}

bool
nir_normalize_cubemap_coords(nir_shader *shader)
{
   return nir_shader_instructions_pass(shader, normalize_cubemap_coords,
                                       nir_metadata_block_index |
                                       nir_metadata_dominance,
                                       NULL);
}