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                       nir_variable_mode modes)
  33 {
  34    unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
  35
  36    switch (instr->intrinsic) {
  37    case nir_intrinsic_copy_var:
  38       _mesa_set_add(live, instr->variables[1]->var);
  39       /* Fall through */
  40    case nir_intrinsic_store_var: {
  41       /* The first source in both copy_var and store_var is the destination.
  42        * If the variable is a local that never escapes the shader, then we
  43        * don't mark it as live for just a store.
  44        */
  45       nir_variable_mode mode = instr->variables[0]->var->data.mode;
  46       if (!(mode & (nir_var_local | nir_var_global | nir_var_shared)))
  47          _mesa_set_add(live, instr->variables[0]->var);
  48       break;
  49    }
  50
  51    /* This pass can't be used on I/O variables after they've been lowered. */
  52    case nir_intrinsic_load_input:
  53       assert(!(modes & nir_var_shader_in));
  54       break;
  55    case nir_intrinsic_store_output:
  56       assert(!(modes & nir_var_shader_out));
  57       break;
  58
  59    default:
  60       for (unsigned i = 0; i < num_vars; i++) {
  61          _mesa_set_add(live, instr->variables[i]->var);
  62       }
  63       break;
  64    }
  65 }
  66
  67 static void
  68 add_var_use_call(nir_call_instr *instr, struct set *live)
  69 {
  70    if (instr->return_deref != NULL) {
  71       nir_variable *var = instr->return_deref->var;
  72       _mesa_set_add(live, var);
  73    }
  74
  75    for (unsigned i = 0; i < instr->num_params; i++) {
  76       nir_variable *var = instr->params[i]->var;
  77       _mesa_set_add(live, var);
  78    }
  79 }
  80
  81 static void
  82 add_var_use_tex(nir_tex_instr *instr, struct set *live)
  83 {
  84    if (instr->texture != NULL) {
  85       nir_variable *var = instr->texture->var;
  86       _mesa_set_add(live, var);
  87    }
  88
  89    if (instr->sampler != NULL) {
  90       nir_variable *var = instr->sampler->var;
  91       _mesa_set_add(live, var);
  92    }
  93 }
  94
  95 static void
  96 add_var_use_shader(nir_shader *shader, struct set *live, nir_variable_mode modes)
  97 {
  98    nir_foreach_function(function, shader) {
  99       if (function->impl) {
 100          nir_foreach_block(block, function->impl) {
 101             nir_foreach_instr(instr, block) {
 102                switch(instr->type) {
 103                case nir_instr_type_intrinsic:
 104                   add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live,
 105                                         modes);
 106                   break;
 107
 108                case nir_instr_type_call:
 109                   add_var_use_call(nir_instr_as_call(instr), live);
 110                   break;
 111
 112                case nir_instr_type_tex:
 113                   add_var_use_tex(nir_instr_as_tex(instr), live);
 114                   break;
 115
 116                default:
 117                   break;
 118                }
 119             }
 120          }
 121       }
 122    }
 123 }
 124
 125 static void
 126 remove_dead_var_writes(nir_shader *shader, struct set *live)
 127 {
 128    nir_foreach_function(function, shader) {
 129       if (!function->impl)
 130          continue;
 131
 132       nir_foreach_block(block, function->impl) {
 133          nir_foreach_instr_safe(instr, block) {
 134             if (instr->type != nir_instr_type_intrinsic)
 135                continue;
 136
 137             nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 138             if (intrin->intrinsic != nir_intrinsic_copy_var &&
 139                 intrin->intrinsic != nir_intrinsic_store_var)
 140                continue;
 141
 142             /* Stores to dead variables need to be removed */
 143             if (intrin->variables[0]->var->data.mode == 0)
 144                nir_instr_remove(instr);
 145          }
 146       }
 147    }
 148 }
 149
 150 static bool
 151 remove_dead_vars(struct exec_list *var_list, struct set *live)
 152 {
 153    bool progress = false;
 154
 155    foreach_list_typed_safe(nir_variable, var, node, var_list) {
 156       struct set_entry *entry = _mesa_set_search(live, var);
 157       if (entry == NULL) {
 158          /* Mark this variable as used by setting the mode to 0 */
 159          var->data.mode = 0;
 160          exec_node_remove(&var->node);
 161          progress = true;
 162       }
 163    }
 164
 165    return progress;
 166 }
 167
 168 bool
 169 nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes)
 170 {
 171    bool progress = false;
 172    struct set *live =
 173       _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
 174
 175    nir_assert_lowered_derefs(shader, nir_lower_all_derefs);
 176
 177    add_var_use_shader(shader, live, modes);
 178
 179    if (modes & nir_var_uniform)
 180       progress = remove_dead_vars(&shader->uniforms, live) || progress;
 181
 182    if (modes & nir_var_shader_in)
 183       progress = remove_dead_vars(&shader->inputs, live) || progress;
 184
 185    if (modes & nir_var_shader_out)
 186       progress = remove_dead_vars(&shader->outputs, live) || progress;
 187
 188    if (modes & nir_var_global)
 189       progress = remove_dead_vars(&shader->globals, live) || progress;
 190
 191    if (modes & nir_var_system_value)
 192       progress = remove_dead_vars(&shader->system_values, live) || progress;
 193
 194    if (modes & nir_var_shared)
 195       progress = remove_dead_vars(&shader->shared, live) || progress;
 196
 197    if (modes & nir_var_local) {
 198       nir_foreach_function(function, shader) {
 199          if (function->impl) {
 200             if (remove_dead_vars(&function->impl->locals, live))
 201                progress = true;
 202          }
 203       }
 204    }
 205
 206    if (progress) {
 207       remove_dead_var_writes(shader, live);
 208
 209       nir_foreach_function(function, shader) {
 210          if (function->impl) {
 211             nir_metadata_preserve(function->impl, nir_metadata_block_index |
 212                                                   nir_metadata_dominance);
 213          }
 214       }
 215    }
 216
 217    _mesa_set_destroy(live, NULL);
 218    return progress;
 219 }