src/compiler/nir/nir_split_per_member_structs.c

   1 /*
   2  * Copyright © 2018 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25 #include "nir_deref.h"
  26
  27 struct split_struct_state {
  28    void *dead_ctx;
  29
  30    struct hash_table *var_to_member_map;
  31 };
  32
  33 static nir_variable *
  34 find_var_member(struct nir_variable *var, unsigned member,
  35                 struct hash_table *var_to_member_map)
  36 {
  37    struct hash_entry *map_entry =
  38       _mesa_hash_table_search(var_to_member_map, var);
  39    if (map_entry == NULL)
  40       return NULL;
  41
  42    nir_variable **members = map_entry->data;
  43    assert(member < var->num_members);
  44    return members[member];
  45 }
  46
  47 static const struct glsl_type *
  48 member_type(const struct glsl_type *type, unsigned index)
  49 {
  50    if (glsl_type_is_array(type)) {
  51       const struct glsl_type *elem =
  52          member_type(glsl_get_array_element(type), index);
  53       return glsl_array_type(elem, glsl_get_length(type));
  54    } else {
  55       assert(glsl_type_is_struct(type));
  56       assert(index < glsl_get_length(type));
  57       return glsl_get_struct_field(type, index);
  58    }
  59 }
  60
  61 static void
  62 split_variable(struct nir_variable *var, nir_shader *shader,
  63                struct hash_table *var_to_member_map, void *dead_ctx)
  64 {
  65    assert(var->state_slots == NULL);
  66
  67    /* Constant initializers are currently not handled */
  68    assert(var->constant_initializer == NULL);
  69
  70    nir_variable **members =
  71       ralloc_array(dead_ctx, nir_variable *, var->num_members);
  72
  73    for (unsigned i = 0; i < var->num_members; i++) {
  74       char *member_name = NULL;
  75       if (var->name) {
  76          /* Calculate a reasonable variable name */
  77          member_name = ralloc_strdup(dead_ctx, var->name);
  78          const struct glsl_type *t = var->type;
  79          while (glsl_type_is_array(t)) {
  80             ralloc_strcat(&member_name, "[*]");
  81             t = glsl_get_array_element(t);
  82          }
  83          const char *field_name = glsl_get_struct_elem_name(t, i);
  84          if (field_name) {
  85             member_name = ralloc_asprintf(dead_ctx, "%s.%s",
  86                                           member_name, field_name);
  87          } else {
  88             member_name = ralloc_asprintf(dead_ctx, "%s.@%d", member_name, i);
  89          }
  90       }
  91
  92       members[i] =
  93          nir_variable_create(shader, var->members[i].mode,
  94                              member_type(var->type, i), member_name);
  95       if (var->interface_type) {
  96          members[i]->interface_type =
  97             glsl_get_struct_field(var->interface_type, i);
  98       }
  99       members[i]->data = var->members[i];
 100    }
 101
 102    _mesa_hash_table_insert(var_to_member_map, var, members);
 103 }
 104
 105 static bool
 106 split_variables_in_list(struct exec_list *var_list, nir_shader *shader,
 107                         struct hash_table *var_to_member_map, void *dead_ctx)
 108 {
 109    bool progress = false;
 110
 111    nir_foreach_variable_safe(var, var_list) {
 112       if (var->num_members == 0)
 113          continue;
 114
 115       split_variable(var, shader, var_to_member_map, dead_ctx);
 116       exec_node_remove(&var->node);
 117       progress = true;
 118    }
 119
 120    return progress;
 121 }
 122
 123 static nir_deref_instr *
 124 build_member_deref(nir_builder *b, nir_deref_instr *deref, nir_variable *member)
 125 {
 126    if (deref->deref_type == nir_deref_type_var) {
 127       return nir_build_deref_var(b, member);
 128    } else {
 129       nir_deref_instr *parent =
 130          build_member_deref(b, nir_deref_instr_parent(deref), member);
 131       return nir_build_deref_follower(b, parent, deref);
 132    }
 133 }
 134
 135 static void
 136 rewrite_deref_instr(nir_builder *b, nir_deref_instr *deref,
 137                     struct hash_table *var_to_member_map)
 138 {
 139    /* We must be a struct deref */
 140    if (deref->deref_type != nir_deref_type_struct)
 141       return;
 142
 143    nir_deref_instr *base;
 144    for (base = nir_deref_instr_parent(deref);
 145         base && base->deref_type != nir_deref_type_var;
 146         base = nir_deref_instr_parent(base)) {
 147
 148       /* If this struct is nested inside another, bail */
 149       if (base->deref_type == nir_deref_type_struct)
 150          return;
 151    }
 152
 153    /* We must be on a variable with members */
 154    if (!base || base->var->num_members == 0)
 155       return;
 156
 157    nir_variable *member = find_var_member(base->var, deref->strct.index,
 158                                           var_to_member_map);
 159    assert(member);
 160
 161    b->cursor = nir_before_instr(&deref->instr);
 162    nir_deref_instr *member_deref =
 163       build_member_deref(b, nir_deref_instr_parent(deref), member);
 164    nir_ssa_def_rewrite_uses(&deref->dest.ssa,
 165                             nir_src_for_ssa(&member_deref->dest.ssa));
 166
 167    /* The referenced variable is no longer valid, clean up the deref */
 168    nir_deref_instr_remove_if_unused(deref);
 169 }
 170
 171 bool
 172 nir_split_per_member_structs(nir_shader *shader)
 173 {
 174    bool progress = false;
 175    void *dead_ctx = ralloc_context(NULL);
 176    struct hash_table *var_to_member_map =
 177       _mesa_hash_table_create(dead_ctx, _mesa_hash_pointer,
 178                               _mesa_key_pointer_equal);
 179
 180    progress |= split_variables_in_list(&shader->inputs, shader,
 181                                        var_to_member_map, dead_ctx);
 182    progress |= split_variables_in_list(&shader->outputs, shader,
 183                                        var_to_member_map, dead_ctx);
 184    progress |= split_variables_in_list(&shader->system_values, shader,
 185                                        var_to_member_map, dead_ctx);
 186    if (!progress)
 187       return false;
 188
 189    nir_foreach_function(function, shader) {
 190       if (!function->impl)
 191          continue;
 192
 193       nir_builder b;
 194       nir_builder_init(&b, function->impl);
 195       nir_foreach_block(block, function->impl) {
 196          nir_foreach_instr_safe(instr, block) {
 197             if (instr->type == nir_instr_type_deref) {
 198                rewrite_deref_instr(&b, nir_instr_as_deref(instr),
 199                                    var_to_member_map);
 200             }
 201          }
 202       }
 203    }
 204
 205    ralloc_free(dead_ctx);
 206
 207    return progress;
 208 }