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       assert(glsl_get_explicit_stride(type) == 0);
  54       return glsl_array_type(elem, glsl_get_length(type), 0);
  55    } else {
  56       assert(glsl_type_is_struct_or_ifc(type));
  57       assert(index < glsl_get_length(type));
  58       return glsl_get_struct_field(type, index);
  59    }
  60 }
  61
  62 static void
  63 split_variable(struct nir_variable *var, nir_shader *shader,
  64                struct hash_table *var_to_member_map, void *dead_ctx)
  65 {
  66    assert(var->state_slots == NULL);
  67
  68    /* Constant initializers are currently not handled */
  69    assert(var->constant_initializer == NULL && var->pointer_initializer == NULL);
  70
  71    nir_variable **members =
  72       ralloc_array(dead_ctx, nir_variable *, var->num_members);
  73
  74    for (unsigned i = 0; i < var->num_members; i++) {
  75       char *member_name = NULL;
  76       if (var->name) {
  77          /* Calculate a reasonable variable name */
  78          member_name = ralloc_strdup(dead_ctx, var->name);
  79          const struct glsl_type *t = var->type;
  80          while (glsl_type_is_array(t)) {
  81             ralloc_strcat(&member_name, "[*]");
  82             t = glsl_get_array_element(t);
  83          }
  84          const char *field_name = glsl_get_struct_elem_name(t, i);
  85          if (field_name) {
  86             member_name = ralloc_asprintf(dead_ctx, "%s.%s",
  87                                           member_name, field_name);
  88          } else {
  89             member_name = ralloc_asprintf(dead_ctx, "%s.@%d", member_name, i);
  90          }
  91       }
  92
  93       members[i] =
  94          nir_variable_create(shader, var->members[i].mode,
  95                              member_type(var->type, i), member_name);
  96       if (var->interface_type) {
  97          members[i]->interface_type =
  98             glsl_get_struct_field(var->interface_type, i);
  99       }
 100       members[i]->data = var->members[i];
 101    }
 102
 103    _mesa_hash_table_insert(var_to_member_map, var, members);
 104 }
 105
 106 static bool
 107 split_variables_in_list(struct exec_list *var_list, nir_shader *shader,
 108                         struct hash_table *var_to_member_map, void *dead_ctx)
 109 {
 110    bool progress = false;
 111
 112    nir_foreach_variable_safe(var, var_list) {
 113       if (var->num_members == 0)
 114          continue;
 115
 116       split_variable(var, shader, var_to_member_map, dead_ctx);
 117       exec_node_remove(&var->node);
 118       progress = true;
 119    }
 120
 121    return progress;
 122 }
 123
 124 static nir_deref_instr *
 125 build_member_deref(nir_builder *b, nir_deref_instr *deref, nir_variable *member)
 126 {
 127    if (deref->deref_type == nir_deref_type_var) {
 128       return nir_build_deref_var(b, member);
 129    } else {
 130       nir_deref_instr *parent =
 131          build_member_deref(b, nir_deref_instr_parent(deref), member);
 132       return nir_build_deref_follower(b, parent, deref);
 133    }
 134 }
 135
 136 static void
 137 rewrite_deref_instr(nir_builder *b, nir_deref_instr *deref,
 138                     struct hash_table *var_to_member_map)
 139 {
 140    /* We must be a struct deref */
 141    if (deref->deref_type != nir_deref_type_struct)
 142       return;
 143
 144    nir_deref_instr *base;
 145    for (base = nir_deref_instr_parent(deref);
 146         base && base->deref_type != nir_deref_type_var;
 147         base = nir_deref_instr_parent(base)) {
 148
 149       /* If this struct is nested inside another, bail */
 150       if (base->deref_type == nir_deref_type_struct)
 151          return;
 152    }
 153
 154    /* We must be on a variable with members */
 155    if (!base || base->var->num_members == 0)
 156       return;
 157
 158    nir_variable *member = find_var_member(base->var, deref->strct.index,
 159                                           var_to_member_map);
 160    assert(member);
 161
 162    b->cursor = nir_before_instr(&deref->instr);
 163    nir_deref_instr *member_deref =
 164       build_member_deref(b, nir_deref_instr_parent(deref), member);
 165    nir_ssa_def_rewrite_uses(&deref->dest.ssa,
 166                             nir_src_for_ssa(&member_deref->dest.ssa));
 167
 168    /* The referenced variable is no longer valid, clean up the deref */
 169    nir_deref_instr_remove_if_unused(deref);
 170 }
 171
 172 bool
 173 nir_split_per_member_structs(nir_shader *shader)
 174 {
 175    bool progress = false;
 176    void *dead_ctx = ralloc_context(NULL);
 177    struct hash_table *var_to_member_map =
 178       _mesa_pointer_hash_table_create(dead_ctx);
 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       ralloc_free(dead_ctx);
 188       return false;
 189    }
 190
 191    nir_foreach_function(function, shader) {
 192       if (!function->impl)
 193          continue;
 194
 195       nir_builder b;
 196       nir_builder_init(&b, function->impl);
 197       nir_foreach_block(block, function->impl) {
 198          nir_foreach_instr_safe(instr, block) {
 199             if (instr->type == nir_instr_type_deref) {
 200                rewrite_deref_instr(&b, nir_instr_as_deref(instr),
 201                                    var_to_member_map);
 202             }
 203          }
 204       }
 205
 206       nir_metadata_preserve(function->impl,
 207                             nir_metadata_block_index |
 208                             nir_metadata_dominance);
 209    }
 210
 211    ralloc_free(dead_ctx);
 212
 213    return progress;
 214 }