mesa/src/compiler/nir/nir_lower_io_to_scalar.c

/*
 * Copyright © 2016 Broadcom
 *
 * 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"
#include "nir_builder.h"

/** @file nir_lower_io_to_scalar.c
 *
 * Replaces nir_load_input/nir_store_output operations with num_components !=
 * 1 with individual per-channel operations.
 */

static void
lower_load_input_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
{
   b->cursor = nir_before_instr(&intr->instr);

   assert(intr->dest.is_ssa);

   nir_ssa_def *loads[4];

   for (unsigned i = 0; i < intr->num_components; i++) {
      nir_intrinsic_instr *chan_intr =
         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
      nir_ssa_dest_init(&chan_intr->instr, &chan_intr->dest,
                        1, intr->dest.ssa.bit_size, NULL);
      chan_intr->num_components = 1;

      nir_intrinsic_set_base(chan_intr, nir_intrinsic_base(intr));
      nir_intrinsic_set_component(chan_intr, nir_intrinsic_component(intr) + i);
      /* offset */
      nir_src_copy(&chan_intr->src[0], &intr->src[0], chan_intr);

      nir_builder_instr_insert(b, &chan_intr->instr);

      loads[i] = &chan_intr->dest.ssa;
   }

   nir_ssa_def_rewrite_uses(&intr->dest.ssa,
                            nir_src_for_ssa(nir_vec(b, loads,
                                                    intr->num_components)));
   nir_instr_remove(&intr->instr);
}

static void
lower_store_output_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
{
   b->cursor = nir_before_instr(&intr->instr);

   nir_ssa_def *value = nir_ssa_for_src(b, intr->src[0], intr->num_components);

   for (unsigned i = 0; i < intr->num_components; i++) {
      if (!(nir_intrinsic_write_mask(intr) & (1 << i)))
         continue;

      nir_intrinsic_instr *chan_intr =
         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
      chan_intr->num_components = 1;

      nir_intrinsic_set_base(chan_intr, nir_intrinsic_base(intr));
      nir_intrinsic_set_write_mask(chan_intr, 0x1);
      nir_intrinsic_set_component(chan_intr, nir_intrinsic_component(intr) + i);

      /* value */
      chan_intr->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
      /* offset */
      nir_src_copy(&chan_intr->src[1], &intr->src[1], chan_intr);

      nir_builder_instr_insert(b, &chan_intr->instr);
   }

   nir_instr_remove(&intr->instr);
}

void
nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask)
{
   nir_foreach_function(function, shader) {
      if (function->impl) {
         nir_builder b;
         nir_builder_init(&b, function->impl);

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

               nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);

               if (intr->num_components == 1)
                  continue;

               switch (intr->intrinsic) {
               case nir_intrinsic_load_input:
                  if (mask & nir_var_shader_in)
                     lower_load_input_to_scalar(&b, intr);
                  break;
               case nir_intrinsic_store_output:
                  if (mask & nir_var_shader_out)
                     lower_store_output_to_scalar(&b, intr);
                  break;
               default:
                  break;
               }
            }
         }
      }
   }
}

static nir_variable **
get_channel_variables(struct hash_table *ht, nir_variable *var)
{
   nir_variable **chan_vars;
   struct hash_entry *entry = _mesa_hash_table_search(ht, var);
   if (!entry) {
      chan_vars = (nir_variable **) calloc(4, sizeof(nir_variable *));
      _mesa_hash_table_insert(ht, var, chan_vars);
   } else {
      chan_vars = (nir_variable **) entry->data;
   }

   return chan_vars;
}

/*
 * This function differs from nir_deref_clone() in that it gets its type from
 * the parent deref rather than our source deref. This is useful when splitting
 * vectors because we want to use the scalar type of the new parent rather than
 * then the old vector type.
 */
static nir_deref_array *
clone_deref_array(const nir_deref_array *darr, nir_deref *parent)
{
   nir_deref_array *ndarr = nir_deref_array_create(parent);

   ndarr->deref.type = glsl_get_array_element(parent->type);
   if (darr->deref.child)
      ndarr->deref.child =
         &clone_deref_array(nir_deref_as_array(darr->deref.child),
                            &ndarr->deref)->deref;

   ndarr->deref_array_type = darr->deref_array_type;
   ndarr->base_offset = darr->base_offset;
   if (ndarr->deref_array_type == nir_deref_array_type_indirect)
     nir_src_copy(&ndarr->indirect, &darr->indirect, parent);

   return ndarr;
}

static void
lower_load_to_scalar_early(nir_builder *b, nir_intrinsic_instr *intr,
                           nir_variable *var, struct hash_table *split_inputs,
                           struct hash_table *split_outputs)
{
   b->cursor = nir_before_instr(&intr->instr);

   assert(intr->dest.is_ssa);

   nir_ssa_def *loads[4];

   nir_variable **chan_vars;
   if (var->data.mode == nir_var_shader_in) {
      chan_vars = get_channel_variables(split_inputs, var);
   } else {
      chan_vars = get_channel_variables(split_outputs, var);
   }

   for (unsigned i = 0; i < intr->num_components; i++) {
      nir_variable *chan_var = chan_vars[var->data.location_frac + i];
      if (!chan_vars[var->data.location_frac + i]) {
         chan_var = nir_variable_clone(var, b->shader);
         chan_var->data.location_frac =  var->data.location_frac + i;
         chan_var->type = glsl_channel_type(chan_var->type);

         chan_vars[var->data.location_frac + i] = chan_var;

         nir_shader_add_variable(b->shader, chan_var);
      }

      nir_intrinsic_instr *chan_intr =
         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
      nir_ssa_dest_init(&chan_intr->instr, &chan_intr->dest,
                        1, intr->dest.ssa.bit_size, NULL);
      chan_intr->num_components = 1;
      chan_intr->variables[0] = nir_deref_var_create(chan_intr, chan_var);

      if (intr->variables[0]->deref.child) {
         chan_intr->variables[0]->deref.child =
            &clone_deref_array(nir_deref_as_array(intr->variables[0]->deref.child),
                               &chan_intr->variables[0]->deref)->deref;
      }

      if (intr->intrinsic == nir_intrinsic_interp_var_at_offset ||
          intr->intrinsic == nir_intrinsic_interp_var_at_sample)
         nir_src_copy(chan_intr->src, intr->src, &chan_intr->instr);

      nir_builder_instr_insert(b, &chan_intr->instr);

      loads[i] = &chan_intr->dest.ssa;
   }

   nir_ssa_def_rewrite_uses(&intr->dest.ssa,
                            nir_src_for_ssa(nir_vec(b, loads,
                                                    intr->num_components)));

   /* Remove the old load intrinsic */
   nir_instr_remove(&intr->instr);
}

static void
lower_store_output_to_scalar_early(nir_builder *b, nir_intrinsic_instr *intr,
                                   nir_variable *var,
                                   struct hash_table *split_outputs)
{
   b->cursor = nir_before_instr(&intr->instr);

   nir_ssa_def *value = nir_ssa_for_src(b, intr->src[0], intr->num_components);

   nir_variable **chan_vars = get_channel_variables(split_outputs, var);
   for (unsigned i = 0; i < intr->num_components; i++) {
      if (!(nir_intrinsic_write_mask(intr) & (1 << i)))
         continue;

      nir_variable *chan_var = chan_vars[var->data.location_frac + i];
      if (!chan_vars[var->data.location_frac + i]) {
         chan_var = nir_variable_clone(var, b->shader);
         chan_var->data.location_frac =  var->data.location_frac + i;
         chan_var->type = glsl_channel_type(chan_var->type);

         chan_vars[var->data.location_frac + i] = chan_var;

         nir_shader_add_variable(b->shader, chan_var);
      }

      nir_intrinsic_instr *chan_intr =
         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
      chan_intr->num_components = 1;

      nir_intrinsic_set_write_mask(chan_intr, 0x1);

      chan_intr->variables[0] = nir_deref_var_create(chan_intr, chan_var);
      chan_intr->src[0] = nir_src_for_ssa(nir_channel(b, value, i));

      if (intr->variables[0]->deref.child) {
         chan_intr->variables[0]->deref.child =
            &clone_deref_array(nir_deref_as_array(intr->variables[0]->deref.child),
                               &chan_intr->variables[0]->deref)->deref;
      }

      nir_builder_instr_insert(b, &chan_intr->instr);
   }

   /* Remove the old store intrinsic */
   nir_instr_remove(&intr->instr);
}

/*
 * This function is intended to be called earlier than nir_lower_io_to_scalar()
 * i.e. before nir_lower_io() is called.
 */
void
nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask)
{
   struct hash_table *split_inputs =
      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                              _mesa_key_pointer_equal);
   struct hash_table *split_outputs =
      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                              _mesa_key_pointer_equal);

   nir_foreach_function(function, shader) {
      if (function->impl) {
         nir_builder b;
         nir_builder_init(&b, function->impl);

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

               nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);

               if (intr->num_components == 1)
                  continue;

               if (intr->intrinsic != nir_intrinsic_load_var &&
                   intr->intrinsic != nir_intrinsic_store_var &&
                   intr->intrinsic != nir_intrinsic_interp_var_at_centroid &&
                   intr->intrinsic != nir_intrinsic_interp_var_at_sample &&
                   intr->intrinsic != nir_intrinsic_interp_var_at_offset)
                  continue;

               nir_variable *var = intr->variables[0]->var;
               nir_variable_mode mode = var->data.mode;

               /* TODO: add patch support */
               if (var->data.patch)
                  continue;

               /* TODO: add doubles support */
               if (glsl_type_is_64bit(glsl_without_array(var->type)))
                  continue;

               if (var->data.location < VARYING_SLOT_VAR0 &&
                   var->data.location >= 0)
                  continue;

               /* Don't bother splitting if we can't opt away any unused
                * components.
                */
               if (var->data.always_active_io)
                  continue;

              /* Skip types we cannot split */
              if (glsl_type_is_matrix(glsl_without_array(var->type)) ||
                  glsl_type_is_struct(glsl_without_array(var->type)))
                 continue;

               switch (intr->intrinsic) {
               case nir_intrinsic_interp_var_at_centroid:
               case nir_intrinsic_interp_var_at_sample:
               case nir_intrinsic_interp_var_at_offset:
               case nir_intrinsic_load_var:
                  if ((mask & nir_var_shader_in && mode == nir_var_shader_in) ||
                      (mask & nir_var_shader_out && mode == nir_var_shader_out))
                     lower_load_to_scalar_early(&b, intr, var, split_inputs,
                                                split_outputs);
                  break;
               case nir_intrinsic_store_var:
                  if (mask & nir_var_shader_out &&
                      mode == nir_var_shader_out)
                     lower_store_output_to_scalar_early(&b, intr, var,
                                                        split_outputs);
                  break;
               default:
                  break;
               }
            }
         }
      }
   }

   /* Remove old input from the shaders inputs list */
   struct hash_entry *entry;
   hash_table_foreach(split_inputs, entry) {
      nir_variable *var = (nir_variable *) entry->key;
      exec_node_remove(&var->node);

      free(entry->data);
   }

   /* Remove old output from the shaders outputs list */
   hash_table_foreach(split_outputs, entry) {
      nir_variable *var = (nir_variable *) entry->key;
      exec_node_remove(&var->node);

      free(entry->data);
   }

   _mesa_hash_table_destroy(split_inputs, NULL);
   _mesa_hash_table_destroy(split_outputs, NULL);
}