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#include "nir_worklist.h"
30
31/* SSA-based mark-and-sweep dead code elimination */
32
33static void
34mark_and_push(nir_instr_worklist *wl, nir_instr *instr)
35{
36   nir_instr_worklist_push_tail(wl, instr);
37   instr->pass_flags = 1;
38}
39
40static bool
41mark_live_cb(nir_src *src, void *_state)
42{
43   nir_instr_worklist *worklist = (nir_instr_worklist *) _state;
44
45   if (src->is_ssa && !src->ssa->parent_instr->pass_flags)
46      mark_and_push(worklist, src->ssa->parent_instr);
47
48   return true;
49}
50
51static void
52init_instr(nir_instr *instr, nir_instr_worklist *worklist)
53{
54   nir_alu_instr *alu_instr;
55   nir_deref_instr *deref_instr;
56   nir_intrinsic_instr *intrin_instr;
57   nir_tex_instr *tex_instr;
58
59   /* We use the pass_flags to store the live/dead information.  In DCE, we
60    * just treat it as a zero/non-zero boolean for whether or not the
61    * instruction is live.
62    */
63   instr->pass_flags = 0;
64
65   switch (instr->type) {
66   case nir_instr_type_call:
67   case nir_instr_type_jump:
68      mark_and_push(worklist, instr);
69      break;
70
71   case nir_instr_type_alu:
72      alu_instr = nir_instr_as_alu(instr);
73      if (!alu_instr->dest.dest.is_ssa)
74         mark_and_push(worklist, instr);
75      break;
76
77   case nir_instr_type_deref:
78      deref_instr = nir_instr_as_deref(instr);
79      if (!deref_instr->dest.is_ssa)
80         mark_and_push(worklist, instr);
81      break;
82
83   case nir_instr_type_intrinsic:
84      intrin_instr = nir_instr_as_intrinsic(instr);
85      if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
86          NIR_INTRINSIC_CAN_ELIMINATE) {
87         if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
88             !intrin_instr->dest.is_ssa) {
89            mark_and_push(worklist, instr);
90         }
91      } else {
92         mark_and_push(worklist, instr);
93      }
94      break;
95
96   case nir_instr_type_tex:
97      tex_instr = nir_instr_as_tex(instr);
98      if (!tex_instr->dest.is_ssa)
99         mark_and_push(worklist, instr);
100      break;
101
102   default:
103      break;
104   }
105}
106
107static bool
108init_block(nir_block *block, nir_instr_worklist *worklist)
109{
110   nir_foreach_instr(instr, block)
111      init_instr(instr, worklist);
112
113   nir_if *following_if = nir_block_get_following_if(block);
114   if (following_if) {
115      if (following_if->condition.is_ssa &&
116          !following_if->condition.ssa->parent_instr->pass_flags)
117         mark_and_push(worklist, following_if->condition.ssa->parent_instr);
118   }
119
120   return true;
121}
122
123static bool
124nir_opt_dce_impl(nir_function_impl *impl)
125{
126   nir_instr_worklist *worklist = nir_instr_worklist_create();
127
128   nir_foreach_block(block, impl) {
129      init_block(block, worklist);
130   }
131
132   nir_foreach_instr_in_worklist(instr, worklist)
133      nir_foreach_src(instr, mark_live_cb, worklist);
134
135   nir_instr_worklist_destroy(worklist);
136
137   bool progress = false;
138
139   nir_foreach_block(block, impl) {
140      nir_foreach_instr_safe(instr, block) {
141         if (!instr->pass_flags) {
142            nir_instr_remove(instr);
143            progress = true;
144         }
145      }
146   }
147
148   if (progress) {
149      nir_metadata_preserve(impl, nir_metadata_block_index |
150                                  nir_metadata_dominance);
151   } else {
152#ifndef NDEBUG
153      impl->valid_metadata &= ~nir_metadata_not_properly_reset;
154#endif
155   }
156
157   return progress;
158}
159
160bool
161nir_opt_dce(nir_shader *shader)
162{
163   bool progress = false;
164   nir_foreach_function(function, shader) {
165      if (function->impl && nir_opt_dce_impl(function->impl))
166         progress = true;
167   }
168
169   return progress;
170}
171