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
30static void
31add_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
58static void
59add_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
72static void
73add_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
86static void
87add_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
115static void
116remove_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
140static bool
141remove_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
158bool
159nir_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}
208