summaryrefslogtreecommitdiffstats
path: root/src/compiler/nir/nir_opt_dce.c
blob: d94f4be28e0df49403c7dc2c1d2eb51ff2911871 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Connor Abbott (cwabbott0@gmail.com)
 *
 */

#include "nir.h"

/* SSA-based mark-and-sweep dead code elimination */

typedef struct {
   struct exec_node node;
   nir_instr *instr;
} worklist_elem;

static void
worklist_push(struct exec_list *worklist, nir_instr *instr)
{
   worklist_elem *elem = ralloc(worklist, worklist_elem);
   elem->instr = instr;
   instr->pass_flags = 1;
   exec_list_push_tail(worklist, &elem->node);
}

static nir_instr *
worklist_pop(struct exec_list *worklist)
{
   struct exec_node *node = exec_list_pop_head(worklist);
   worklist_elem *elem = exec_node_data(worklist_elem, node, node);
   return elem->instr;
}

static bool
mark_live_cb(nir_src *src, void *_state)
{
   struct exec_list *worklist = (struct exec_list *) _state;

   if (src->is_ssa && !src->ssa->parent_instr->pass_flags) {
      worklist_push(worklist, src->ssa->parent_instr);
   }

   return true;
}

static void
init_instr(nir_instr *instr, struct exec_list *worklist)
{
   nir_alu_instr *alu_instr;
   nir_intrinsic_instr *intrin_instr;
   nir_tex_instr *tex_instr;

   /* We use the pass_flags to store the live/dead information.  In DCE, we
    * just treat it as a zero/non-zero boolean for whether or not the
    * instruction is live.
    */
   instr->pass_flags = 0;

   switch (instr->type) {
   case nir_instr_type_call:
   case nir_instr_type_jump:
      worklist_push(worklist, instr);
      break;

   case nir_instr_type_alu:
      alu_instr = nir_instr_as_alu(instr);
      if (!alu_instr->dest.dest.is_ssa)
         worklist_push(worklist, instr);
      break;

   case nir_instr_type_intrinsic:
      intrin_instr = nir_instr_as_intrinsic(instr);
      if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
          NIR_INTRINSIC_CAN_ELIMINATE) {
         if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
             !intrin_instr->dest.is_ssa) {
            worklist_push(worklist, instr);
         }
      } else {
         worklist_push(worklist, instr);
      }
      break;

   case nir_instr_type_tex:
      tex_instr = nir_instr_as_tex(instr);
      if (!tex_instr->dest.is_ssa)
         worklist_push(worklist, instr);
      break;

   default:
      break;
   }
}

static bool
init_block(nir_block *block, struct exec_list *worklist)
{
   nir_foreach_instr(block, instr)
      init_instr(instr, worklist);

   nir_if *following_if = nir_block_get_following_if(block);
   if (following_if) {
      if (following_if->condition.is_ssa &&
          !following_if->condition.ssa->parent_instr->pass_flags)
         worklist_push(worklist, following_if->condition.ssa->parent_instr);
   }

   return true;
}

static bool
nir_opt_dce_impl(nir_function_impl *impl)
{
   struct exec_list *worklist = ralloc(NULL, struct exec_list);
   exec_list_make_empty(worklist);

   nir_foreach_block(block, impl) {
      init_block(block, worklist);
   }

   while (!exec_list_is_empty(worklist)) {
      nir_instr *instr = worklist_pop(worklist);
      nir_foreach_src(instr, mark_live_cb, worklist);
   }

   ralloc_free(worklist);

   bool progress = false;

   nir_foreach_block(block, impl) {
      nir_foreach_instr_safe(block, instr) {
         if (!instr->pass_flags) {
            nir_instr_remove(instr);
            progress = true;
         }
      }
   }

   if (progress)
      nir_metadata_preserve(impl, nir_metadata_block_index |
                                  nir_metadata_dominance);

   return progress;
}

bool
nir_opt_dce(nir_shader *shader)
{
   bool progress = false;
   nir_foreach_function(shader, function) {
      if (function->impl && nir_opt_dce_impl(function->impl))
         progress = true;
   }

   return progress;
}