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
  35    switch (instr->intrinsic) {
  36    case nir_intrinsic_copy_var:
  37       _mesa_set_add(live, instr->variables[1]->var);
  38       /* Fall through */
  39    case nir_intrinsic_store_var: {
  40       /* The first source in both copy_var and store_var is the destination.
  41        * If the variable is a local that never escapes the shader, then we
  42        * don't mark it as live for just a store.
  43        */
  44       nir_variable_mode mode = instr->variables[0]->var->data.mode;
  45       if (!(mode & (nir_var_local | nir_var_global | nir_var_shared)))
  46          _mesa_set_add(live, instr->variables[0]->var);
  47       break;
  48    }
  49
  50    default:
  51       for (unsigned i = 0; i < num_vars; i++) {
  52          _mesa_set_add(live, instr->variables[i]->var);
  53       }
  54       break;
  55    }
  56 }
  57
  58 static void
  59 add_var_use_call(nir_call_instr *instr, struct set *live)
  60 {
  61    if (instr->return_deref != NULL) {
  62       nir_variable *var = instr->return_deref->var;
  63       _mesa_set_add(live, var);
  64    }
  65
  66    for (unsigned i = 0; i < instr->num_params; i++) {
  67       nir_variable *var = instr->params[i]->var;
  68       _mesa_set_add(live, var);
  69    }
  70 }
  71
  72 static void
  73 add_var_use_tex(nir_tex_instr *instr, struct set *live)
  74 {
  75    if (instr->texture != NULL) {
  76       nir_variable *var = instr->texture->var;
  77       _mesa_set_add(live, var);
  78    }
  79
  80    if (instr->sampler != NULL) {
  81       nir_variable *var = instr->sampler->var;
  82       _mesa_set_add(live, var);
  83    }
  84 }
  85
  86 static void
  87 add_var_use_shader(nir_shader *shader, struct set *live)
  88 {
  89    nir_foreach_function(function, shader) {
  90       if (function->impl) {
  91          nir_foreach_block(block, function->impl) {
  92             nir_foreach_instr(instr, block) {
  93                switch(instr->type) {
  94                case nir_instr_type_intrinsic:
  95                   add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live);
  96                   break;
  97
  98                case nir_instr_type_call:
  99                   add_var_use_call(nir_instr_as_call(instr), live);
 100                   break;
 101
 102                case nir_instr_type_tex:
 103                   add_var_use_tex(nir_instr_as_tex(instr), live);
 104                   break;
 105
 106                default:
 107                   break;
 108                }
 109             }
 110          }
 111       }
 112    }
 113 }
 114
 115 static void
 116 remove_dead_var_writes(nir_shader *shader, struct set *live)
 117 {
 118    nir_foreach_function(function, shader) {
 119       if (!function->impl)
 120          continue;
 121
 122       nir_foreach_block(block, function->impl) {
 123          nir_foreach_instr_safe(instr, block) {
 124             if (instr->type != nir_instr_type_intrinsic)
 125                continue;
 126
 127             nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 128             if (intrin->intrinsic != nir_intrinsic_copy_var &&
 129                 intrin->intrinsic != nir_intrinsic_store_var)
 130                continue;
 131
 132             /* Stores to dead variables need to be removed */
 133             if (intrin->variables[0]->var->data.mode == 0)
 134                nir_instr_remove(instr);
 135          }
 136       }
 137    }
 138 }
 139
 140 static bool
 141 remove_dead_vars(struct exec_list *var_list, struct set *live)
 142 {
 143    bool progress = false;
 144
 145    foreach_list_typed_safe(nir_variable, var, node, var_list) {
 146       struct set_entry *entry = _mesa_set_search(live, var);
 147       if (entry == NULL) {
 148          /* Mark this variable as used by setting the mode to 0 */
 149          var->data.mode = 0;
 150          exec_node_remove(&var->node);
 151          progress = true;
 152       }
 153    }
 154
 155    return progress;
 156 }
 157
 158 bool
 159 nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes)
 160 {
 161    bool progress = false;
 162    struct set *live =
 163       _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
 164
 165    add_var_use_shader(shader, live);
 166
 167    if (modes & nir_var_uniform)
 168       progress = remove_dead_vars(&shader->uniforms, live) || progress;
 169
 170    if (modes & nir_var_shader_in)
 171       progress = remove_dead_vars(&shader->inputs, live) || progress;
 172
 173    if (modes & nir_var_shader_out)
 174       progress = remove_dead_vars(&shader->outputs, live) || progress;
 175
 176    if (modes & nir_var_global)
 177       progress = remove_dead_vars(&shader->globals, live) || progress;
 178
 179    if (modes & nir_var_system_value)
 180       progress = remove_dead_vars(&shader->system_values, live) || progress;
 181
 182    if (modes & nir_var_shared)
 183       progress = remove_dead_vars(&shader->shared, live) || progress;
 184
 185    if (modes & nir_var_local) {
 186       nir_foreach_function(function, shader) {
 187          if (function->impl) {
 188             if (remove_dead_vars(&function->impl->locals, live))
 189                progress = true;
 190          }
 191       }
 192    }
 193
 194    if (progress) {
 195       remove_dead_var_writes(shader, live);
 196
 197       nir_foreach_function(function, shader) {
 198          if (function->impl) {
 199             nir_metadata_preserve(function->impl, nir_metadata_block_index |
 200                                                   nir_metadata_dominance);
 201          }
 202       }
 203    }
 204
 205    _mesa_set_destroy(live, NULL);
 206    return progress;
 207 }