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 /* SSA-based mark-and-sweep dead code elimination */
31
32 typedef struct {
33 struct exec_node node;
34 nir_instr *instr;
35 } worklist_elem;
36
37 static void
worklist_push(struct exec_list * worklist,nir_instr * instr)38 worklist_push(struct exec_list *worklist, nir_instr *instr)
39 {
40 worklist_elem *elem = ralloc(worklist, worklist_elem);
41 elem->instr = instr;
42 instr->pass_flags = 1;
43 exec_list_push_tail(worklist, &elem->node);
44 }
45
46 static nir_instr *
worklist_pop(struct exec_list * worklist)47 worklist_pop(struct exec_list *worklist)
48 {
49 struct exec_node *node = exec_list_pop_head(worklist);
50 worklist_elem *elem = exec_node_data(worklist_elem, node, node);
51 return elem->instr;
52 }
53
54 static bool
mark_live_cb(nir_src * src,void * _state)55 mark_live_cb(nir_src *src, void *_state)
56 {
57 struct exec_list *worklist = (struct exec_list *) _state;
58
59 if (src->is_ssa && !src->ssa->parent_instr->pass_flags) {
60 worklist_push(worklist, src->ssa->parent_instr);
61 }
62
63 return true;
64 }
65
66 static void
init_instr(nir_instr * instr,struct exec_list * worklist)67 init_instr(nir_instr *instr, struct exec_list *worklist)
68 {
69 nir_alu_instr *alu_instr;
70 nir_intrinsic_instr *intrin_instr;
71 nir_tex_instr *tex_instr;
72
73 /* We use the pass_flags to store the live/dead information. In DCE, we
74 * just treat it as a zero/non-zero boolean for whether or not the
75 * instruction is live.
76 */
77 instr->pass_flags = 0;
78
79 switch (instr->type) {
80 case nir_instr_type_call:
81 case nir_instr_type_jump:
82 worklist_push(worklist, instr);
83 break;
84
85 case nir_instr_type_alu:
86 alu_instr = nir_instr_as_alu(instr);
87 if (!alu_instr->dest.dest.is_ssa)
88 worklist_push(worklist, instr);
89 break;
90
91 case nir_instr_type_intrinsic:
92 intrin_instr = nir_instr_as_intrinsic(instr);
93 if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
94 NIR_INTRINSIC_CAN_ELIMINATE) {
95 if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
96 !intrin_instr->dest.is_ssa) {
97 worklist_push(worklist, instr);
98 }
99 } else {
100 worklist_push(worklist, instr);
101 }
102 break;
103
104 case nir_instr_type_tex:
105 tex_instr = nir_instr_as_tex(instr);
106 if (!tex_instr->dest.is_ssa)
107 worklist_push(worklist, instr);
108 break;
109
110 default:
111 break;
112 }
113 }
114
115 static bool
init_block(nir_block * block,struct exec_list * worklist)116 init_block(nir_block *block, struct exec_list *worklist)
117 {
118 nir_foreach_instr(instr, block)
119 init_instr(instr, worklist);
120
121 nir_if *following_if = nir_block_get_following_if(block);
122 if (following_if) {
123 if (following_if->condition.is_ssa &&
124 !following_if->condition.ssa->parent_instr->pass_flags)
125 worklist_push(worklist, following_if->condition.ssa->parent_instr);
126 }
127
128 return true;
129 }
130
131 static bool
nir_opt_dce_impl(nir_function_impl * impl)132 nir_opt_dce_impl(nir_function_impl *impl)
133 {
134 struct exec_list *worklist = rzalloc(NULL, struct exec_list);
135 exec_list_make_empty(worklist);
136
137 nir_foreach_block(block, impl) {
138 init_block(block, worklist);
139 }
140
141 while (!exec_list_is_empty(worklist)) {
142 nir_instr *instr = worklist_pop(worklist);
143 nir_foreach_src(instr, mark_live_cb, worklist);
144 }
145
146 ralloc_free(worklist);
147
148 bool progress = false;
149
150 nir_foreach_block(block, impl) {
151 nir_foreach_instr_safe(instr, block) {
152 if (!instr->pass_flags) {
153 nir_instr_remove(instr);
154 progress = true;
155 }
156 }
157 }
158
159 if (progress)
160 nir_metadata_preserve(impl, nir_metadata_block_index |
161 nir_metadata_dominance);
162
163 return progress;
164 }
165
166 bool
nir_opt_dce(nir_shader * shader)167 nir_opt_dce(nir_shader *shader)
168 {
169 bool progress = false;
170 nir_foreach_function(function, shader) {
171 if (function->impl && nir_opt_dce_impl(function->impl))
172 progress = true;
173 }
174
175 return progress;
176 }
177