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
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
/*
* Copyright © 2010 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.
*/
/**
* \file opt_discard_simplification.cpp
*
* This pass simplifies if-statements and loops containing unconditional
* discards.
*
* Case 1: Both branches contain unconditional discards:
* -----------------------------------------------------
*
* if (cond) {
* s1;
* discard;
* s2;
* } else {
* s3;
* discard;
* s4;
* }
*
* becomes:
*
* discard
*
* Case 2: The "then" clause contains an unconditional discard:
* ------------------------------------------------------------
*
* if (cond) {
* s1;
* discard;
* s2;
* } else {
* s3;
* }
*
* becomes:
*
* if (cond) {
* discard;
* } else {
* s3;
* }
*
* Case 3: The "else" clause contains an unconditional discard:
* ------------------------------------------------------------
*
* if (cond) {
* s1;
* } else {
* s2;
* discard;
* s3;
* }
*
* becomes:
*
* if (cond) {
* s1;
* } else {
* discard;
* }
*/
#include "glsl_types.h"
#include "ir.h"
class discard_simplifier : public ir_hierarchical_visitor {
public:
discard_simplifier()
{
this->progress = false;
}
ir_visitor_status visit_enter(ir_if *);
ir_visitor_status visit_enter(ir_loop *);
ir_visitor_status visit_enter(ir_assignment *);
bool progress;
};
static ir_discard *
find_unconditional_discard(exec_list &instructions)
{
foreach_list(n, &instructions) {
ir_discard *ir = ((ir_instruction *) n)->as_discard();
if (ir != NULL && ir->condition == NULL)
return ir;
}
return NULL;
}
static bool
is_only_instruction(ir_discard *discard)
{
return (discard->prev->is_head_sentinel() &&
discard->next->is_tail_sentinel());
}
/* We only care about the top level instructions, so don't descend
* into expressions.
*/
ir_visitor_status
discard_simplifier::visit_enter(ir_assignment *ir)
{
return visit_continue_with_parent;
}
ir_visitor_status
discard_simplifier::visit_enter(ir_if *ir)
{
ir_discard *then_discard = find_unconditional_discard(ir->then_instructions);
ir_discard *else_discard = find_unconditional_discard(ir->else_instructions);
if (then_discard == NULL && else_discard == NULL)
return visit_continue;
/* If both branches result in discard, replace whole if with discard. */
if (then_discard != NULL && else_discard != NULL) {
this->progress = true;
ir->replace_with(then_discard);
return visit_continue_with_parent;
}
/* Otherwise, one branch has a discard. */
if (then_discard != NULL && !is_only_instruction(then_discard)) {
this->progress = true;
ir->then_instructions.make_empty();
ir->then_instructions.push_tail(then_discard);
} else if (else_discard != NULL && !is_only_instruction(else_discard)) {
this->progress = true;
ir->else_instructions.make_empty();
ir->else_instructions.push_tail(else_discard);
}
visit_list_elements(this, &ir->then_instructions);
return visit_continue_with_parent;
}
ir_visitor_status
discard_simplifier::visit_enter(ir_loop *ir)
{
ir_discard *discard = find_unconditional_discard(ir->body_instructions);
if (discard) {
ir->replace_with(discard);
return visit_continue_with_parent;
}
return visit_continue;
}
bool
do_discard_simplification(exec_list *instructions)
{
/* Look for a top-level unconditional discard */
ir_discard *discard = find_unconditional_discard(*instructions);
if (discard != NULL) {
instructions->make_empty();
instructions->push_tail(discard);
return true;
}
discard_simplifier v;
visit_list_elements(&v, instructions);
return v.progress;
}
|
