src/compiler/nir/nir_remove_dead_variables.c

   1 /*
   2  * Copyright © 2014 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  * Authors:
  24  *    Connor Abbott (cwabbott0@gmail.com)
  25  *
  26  */
  27
  28 #include "nir.h"
  29
  30 static void
  31 add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live)
  32 {
  33    unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
  34    for (unsigned i = 0; i < num_vars; i++) {
  35       nir_variable *var = instr->variables[i]->var;
  36       _mesa_set_add(live, var);
  37    }
  38 }
  39
  40 static void
  41 add_var_use_call(nir_call_instr *instr, struct set *live)
  42 {
  43    if (instr->return_deref != NULL) {
  44       nir_variable *var = instr->return_deref->var;
  45       _mesa_set_add(live, var);
  46    }
  47
  48    for (unsigned i = 0; i < instr->num_params; i++) {
  49       nir_variable *var = instr->params[i]->var;
  50       _mesa_set_add(live, var);
  51    }
  52 }
  53
  54 static void
  55 add_var_use_tex(nir_tex_instr *instr, struct set *live)
  56 {
  57    if (instr->sampler != NULL) {
  58       nir_variable *var = instr->sampler->var;
  59       _mesa_set_add(live, var);
  60    }
  61 }
  62
  63 static bool
  64 add_var_use_block(nir_block *block, void *state)
  65 {
  66    struct set *live = state;
  67
  68    nir_foreach_instr(block, instr) {
  69       switch(instr->type) {
  70       case nir_instr_type_intrinsic:
  71          add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live);
  72          break;
  73
  74       case nir_instr_type_call:
  75          add_var_use_call(nir_instr_as_call(instr), live);
  76          break;
  77
  78       case nir_instr_type_tex:
  79          add_var_use_tex(nir_instr_as_tex(instr), live);
  80          break;
  81
  82       default:
  83          break;
  84       }
  85    }
  86
  87    return true;
  88 }
  89
  90 static void
  91 add_var_use_shader(nir_shader *shader, struct set *live)
  92 {
  93    nir_foreach_function(shader, function) {
  94       if (function->impl) {
  95          nir_foreach_block(function->impl, add_var_use_block, live);
  96       }
  97    }
  98 }
  99
 100 static bool
 101 remove_dead_vars(struct exec_list *var_list, struct set *live)
 102 {
 103    bool progress = false;
 104
 105    foreach_list_typed_safe(nir_variable, var, node, var_list) {
 106       struct set_entry *entry = _mesa_set_search(live, var);
 107       if (entry == NULL) {
 108          exec_node_remove(&var->node);
 109          ralloc_free(var);
 110          progress = true;
 111       }
 112    }
 113
 114    return progress;
 115 }
 116
 117 bool
 118 nir_remove_dead_variables(nir_shader *shader)
 119 {
 120    bool progress = false;
 121    struct set *live =
 122       _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
 123
 124    add_var_use_shader(shader, live);
 125
 126    progress = remove_dead_vars(&shader->globals, live) || progress;
 127
 128    nir_foreach_function(shader, function) {
 129       if (function->impl) {
 130          if (remove_dead_vars(&function->impl->locals, live)) {
 131             nir_metadata_preserve(function->impl, nir_metadata_block_index |
 132                                                   nir_metadata_dominance |
 133                                                   nir_metadata_live_ssa_defs);
 134             progress = true;
 135          }
 136       }
 137    }
 138
 139    _mesa_set_destroy(live, NULL);
 140    return progress;
 141 }