src/compiler/nir/nir_opt_shrink_load.c

/*
 * Copyright © 2018 Valve 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.
 */

#include "nir.h"

static bool
opt_shrink_load(nir_intrinsic_instr *instr)
{
   bool progress = false;

   if (instr->intrinsic == nir_intrinsic_load_push_constant) {
      unsigned mask = nir_ssa_def_components_read(&instr->dest.ssa);

      if (instr->num_components > util_last_bit(mask)) {
         instr->num_components = util_last_bit(mask);
         instr->dest.ssa.num_components = instr->num_components;
         progress = true;
      }
   }

   return progress;
}

bool
nir_opt_shrink_load(nir_shader *shader)
{
   bool progress = false;

   nir_foreach_function(function, shader) {
      if (!function->impl)
         continue;

      nir_foreach_block(block, function->impl) {
         nir_foreach_instr(instr, block) {
            if (instr->type != nir_instr_type_intrinsic)
               continue;

            progress |= opt_shrink_load(nir_instr_as_intrinsic(instr));
         }
      }

      nir_metadata_preserve(function->impl, nir_metadata_block_index |
                                            nir_metadata_dominance);
   }

   return progress;
}