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 nir_deref_instr *
 107 build_member_deref(nir_builder *b, nir_deref_instr *deref, nir_variable *member)
 108 {
 109    if (deref->deref_type == nir_deref_type_var) {
 110       return nir_build_deref_var(b, member);
 111    } else {
 112       nir_deref_instr *parent =
 113          build_member_deref(b, nir_deref_instr_parent(deref), member);
 114       return nir_build_deref_follower(b, parent, deref);
 115    }
 116 }
 117
 118 static void
 119 rewrite_deref_instr(nir_builder *b, nir_deref_instr *deref,
 120                     struct hash_table *var_to_member_map)
 121 {
 122    /* We must be a struct deref */
 123    if (deref->deref_type != nir_deref_type_struct)
 124       return;
 125
 126    nir_deref_instr *base;
 127    for (base = nir_deref_instr_parent(deref);
 128         base && base->deref_type != nir_deref_type_var;
 129         base = nir_deref_instr_parent(base)) {
 130
 131       /* If this struct is nested inside another, bail */
 132       if (base->deref_type == nir_deref_type_struct)
 133          return;
 134    }
 135
 136    /* We must be on a variable with members */
 137    if (!base || base->var->num_members == 0)
 138       return;
 139
 140    nir_variable *member = find_var_member(base->var, deref->strct.index,
 141                                           var_to_member_map);
 142    assert(member);
 143
 144    b->cursor = nir_before_instr(&deref->instr);
 145    nir_deref_instr *member_deref =
 146       build_member_deref(b, nir_deref_instr_parent(deref), member);
 147    nir_ssa_def_rewrite_uses(&deref->dest.ssa,
 148                             nir_src_for_ssa(&member_deref->dest.ssa));
 149
 150    /* The referenced variable is no longer valid, clean up the deref */
 151    nir_deref_instr_remove_if_unused(deref);
 152 }
 153
 154 bool
 155 nir_split_per_member_structs(nir_shader *shader)
 156 {
 157    bool progress = false;
 158    void *dead_ctx = ralloc_context(NULL);
 159    struct hash_table *var_to_member_map =
 160       _mesa_pointer_hash_table_create(dead_ctx);
 161
 162    nir_foreach_variable_with_modes_safe(var, shader, nir_var_shader_in |
 163                                                      nir_var_shader_out |
 164                                                      nir_var_system_value) {
 165       if (var->num_members == 0)
 166          continue;
 167
 168       split_variable(var, shader, var_to_member_map, dead_ctx);
 169       exec_node_remove(&var->node);
 170       progress = true;
 171    }
 172
 173    if (!progress) {
 174       ralloc_free(dead_ctx);
 175       return false;
 176    }
 177
 178    nir_foreach_function(function, shader) {
 179       if (!function->impl)
 180          continue;
 181
 182       nir_builder b;
 183       nir_builder_init(&b, function->impl);
 184       nir_foreach_block(block, function->impl) {
 185          nir_foreach_instr_safe(instr, block) {
 186             if (instr->type == nir_instr_type_deref) {
 187                rewrite_deref_instr(&b, nir_instr_as_deref(instr),
 188                                    var_to_member_map);
 189             }
 190          }
 191       }
 192
 193       nir_metadata_preserve(function->impl,
 194                             nir_metadata_block_index |
 195                             nir_metadata_dominance);
 196    }
 197
 198    ralloc_free(dead_ctx);
 199
 200    return progress;
 201 }