916a3fb26d1ccaebac9c9971831fb0ba0145f347
2 * Copyright © 2014 Intel Corporation
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6 * to deal in the Software without restriction, including without limitation
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11 * The above copyright notice and this permission notice (including the next
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25 #include "brw_vec4_live_variables.h"
28 /** @file brw_vec4_dead_code_eliminate.cpp
30 * Dataflow-aware dead code elimination.
32 * Walks the instruction list from the bottom, removing instructions that
33 * have results that both aren't used in later blocks and haven't been read
34 * yet in the tail end of this block.
40 vec4_visitor::dead_code_eliminate()
42 bool progress
= false;
44 calculate_live_intervals();
46 int num_vars
= live_intervals
->num_vars
;
47 BITSET_WORD
*live
= ralloc_array(NULL
, BITSET_WORD
, BITSET_WORDS(num_vars
));
48 BITSET_WORD
*flag_live
= ralloc_array(NULL
, BITSET_WORD
, 1);
50 foreach_block_reverse_safe(block
, cfg
) {
51 memcpy(live
, live_intervals
->block_data
[block
->num
].liveout
,
52 sizeof(BITSET_WORD
) * BITSET_WORDS(num_vars
));
53 memcpy(flag_live
, live_intervals
->block_data
[block
->num
].flag_liveout
,
56 foreach_inst_in_block_reverse_safe(vec4_instruction
, inst
, block
) {
57 if ((inst
->dst
.file
== VGRF
&& !inst
->has_side_effects()) ||
58 (inst
->dst
.is_null() && inst
->writes_flag())){
59 bool result_live
[4] = { false };
61 if (inst
->dst
.file
== VGRF
) {
62 for (unsigned i
= 0; i
< regs_written(inst
); i
++) {
63 for (int c
= 0; c
< 4; c
++)
64 result_live
[c
] |= BITSET_TEST(live
,
66 byte_offset(inst
->dst
, i
* REG_SIZE
), c
));
69 for (unsigned c
= 0; c
< 4; c
++)
70 result_live
[c
] = BITSET_TEST(flag_live
, c
);
73 /* If the instruction can't do writemasking, then it's all or
76 if (!inst
->can_do_writemask(devinfo
)) {
77 bool result
= result_live
[0] | result_live
[1] |
78 result_live
[2] | result_live
[3];
79 result_live
[0] = result
;
80 result_live
[1] = result
;
81 result_live
[2] = result
;
82 result_live
[3] = result
;
85 for (int c
= 0; c
< 4; c
++) {
86 if (!result_live
[c
] && inst
->dst
.writemask
& (1 << c
)) {
87 inst
->dst
.writemask
&= ~(1 << c
);
90 if (inst
->dst
.writemask
== 0) {
91 if (inst
->writes_accumulator
|| inst
->writes_flag()) {
92 inst
->dst
= dst_reg(retype(brw_null_reg(), inst
->dst
.type
));
94 inst
->opcode
= BRW_OPCODE_NOP
;
102 if (inst
->dst
.is_null() && inst
->writes_flag()) {
103 bool combined_live
= false;
104 for (unsigned c
= 0; c
< 4; c
++)
105 combined_live
|= BITSET_TEST(flag_live
, c
);
107 if (!combined_live
) {
108 inst
->opcode
= BRW_OPCODE_NOP
;
113 if (inst
->dst
.file
== VGRF
&& !inst
->predicate
) {
114 for (unsigned i
= 0; i
< regs_written(inst
); i
++) {
115 for (int c
= 0; c
< 4; c
++) {
116 if (inst
->dst
.writemask
& (1 << c
)) {
119 byte_offset(inst
->dst
,
127 if (inst
->writes_flag() && !inst
->predicate
) {
128 for (unsigned c
= 0; c
< 4; c
++)
129 BITSET_CLEAR(flag_live
, c
);
132 if (inst
->opcode
== BRW_OPCODE_NOP
) {
137 for (int i
= 0; i
< 3; i
++) {
138 if (inst
->src
[i
].file
== VGRF
) {
139 for (unsigned j
= 0; j
< regs_read(inst
, i
); j
++) {
140 for (int c
= 0; c
< 4; c
++) {
141 BITSET_SET(live
, var_from_reg(alloc
,
142 byte_offset(inst
->src
[i
],
150 for (unsigned c
= 0; c
< 4; c
++) {
151 if (inst
->reads_flag(c
)) {
152 BITSET_SET(flag_live
, c
);
159 ralloc_free(flag_live
);
162 invalidate_live_intervals();