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
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
/*
* 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 ir_dead_code_local.cpp
*
* Eliminates local dead assignments from the code.
*
* This operates on basic blocks, tracking assignments and finding if
* they're used before the variable is completely reassigned.
*
* Compare this to ir_dead_code.cpp, which operates globally looking
* for assignments to variables that are never read.
*/
#include "ir.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "glsl_types.h"
static bool debug = false;
class assignment_entry : public exec_node
{
public:
assignment_entry(ir_variable *lhs, ir_instruction *ir)
{
assert(lhs);
assert(ir);
this->lhs = lhs;
this->ir = ir;
}
ir_variable *lhs;
ir_instruction *ir;
};
class kill_for_derefs_visitor : public ir_hierarchical_visitor {
public:
kill_for_derefs_visitor(exec_list *assignments)
{
this->assignments = assignments;
}
virtual ir_visitor_status visit(ir_dereference_variable *ir)
{
ir_variable *const var = ir->variable_referenced();
foreach_iter(exec_list_iterator, iter, *this->assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (entry->lhs == var) {
if (debug)
printf("kill %s\n", entry->lhs->name);
entry->remove();
}
}
return visit_continue;
}
private:
exec_list *assignments;
};
class array_index_visit : public ir_hierarchical_visitor {
public:
array_index_visit(ir_hierarchical_visitor *v)
{
this->visitor = v;
}
virtual ir_visitor_status visit_enter(class ir_dereference_array *ir)
{
ir->array_index->accept(visitor);
return visit_continue;
}
static void run(ir_instruction *ir, ir_hierarchical_visitor *v)
{
array_index_visit top_visit(v);
ir->accept(& top_visit);
}
ir_hierarchical_visitor *visitor;
};
/**
* Adds an entry to the available copy list if it's a plain assignment
* of a variable to a variable.
*/
static bool
process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
{
ir_variable *var = NULL;
bool progress = false;
kill_for_derefs_visitor v(assignments);
/* Kill assignment entries for things used to produce this assignment. */
ir->rhs->accept(&v);
if (ir->condition) {
ir->condition->accept(&v);
}
/* Kill assignment enties used as array indices.
*/
array_index_visit::run(ir->lhs, &v);
var = ir->lhs->variable_referenced();
assert(var);
bool always_assign = true;
if (ir->condition) {
ir_constant *condition = ir->condition->as_constant();
if (!condition || !condition->value.b[0])
always_assign = false;
}
/* Now, check if we did a whole-variable assignment. */
if (always_assign && (ir->lhs->whole_variable_referenced() != NULL)) {
/* We did a whole-variable assignment. So, any instruction in
* the assignment list with the same LHS is dead.
*/
if (debug)
printf("looking for %s to remove\n", var->name);
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
if (entry->lhs == var) {
if (debug)
printf("removing %s\n", var->name);
entry->ir->remove();
entry->remove();
progress = true;
}
}
}
/* Add this instruction to the assignment list. */
assignment_entry *entry = new(ctx) assignment_entry(var, ir);
assignments->push_tail(entry);
if (debug) {
printf("add %s\n", var->name);
printf("current entries\n");
foreach_iter(exec_list_iterator, iter, *assignments) {
assignment_entry *entry = (assignment_entry *)iter.get();
printf(" %s\n", entry->lhs->name);
}
}
return progress;
}
static void
dead_code_local_basic_block(ir_instruction *first,
ir_instruction *last,
void *data)
{
ir_instruction *ir, *ir_next;
/* List of avaialble_copy */
exec_list assignments;
bool *out_progress = (bool *)data;
bool progress = false;
void *ctx = talloc(NULL, void*);
/* Safe looping, since process_assignment */
for (ir = first, ir_next = (ir_instruction *)first->next;;
ir = ir_next, ir_next = (ir_instruction *)ir->next) {
ir_assignment *ir_assign = ir->as_assignment();
if (debug) {
ir->print();
printf("\n");
}
if (ir_assign) {
progress = process_assignment(ctx, ir_assign, &assignments) || progress;
} else {
kill_for_derefs_visitor kill(&assignments);
ir->accept(&kill);
}
if (ir == last)
break;
}
*out_progress = progress;
talloc_free(ctx);
}
/**
* Does a copy propagation pass on the code present in the instruction stream.
*/
bool
do_dead_code_local(exec_list *instructions)
{
bool progress = false;
call_for_basic_blocks(instructions, dead_code_local_basic_block, &progress);
return progress;
}
|
