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25 * @file vc4_opt_dead_code.c
27 * This is a simmple dead code eliminator for QIR with no control flow.
29 * It walks from the bottom of the instruction list, removing instructions
30 * with a destination that is never used, and marking the sources of non-dead
31 * instructions as used.
39 dce(struct vc4_compile
*c
, struct qinst
*inst
)
42 fprintf(stderr
, "Removing: ");
43 qir_dump_inst(c
, inst
);
44 fprintf(stderr
, "\n");
47 qir_remove_instruction(c
, inst
);
51 has_nonremovable_reads(struct vc4_compile
*c
, struct qinst
*inst
)
53 for (int i
= 0; i
< qir_get_op_nsrc(inst
->op
); i
++) {
54 if (inst
->src
[i
].file
== QFILE_VPM
) {
55 uint32_t attr
= inst
->src
[i
].index
/ 4;
56 uint32_t offset
= (inst
->src
[i
].index
% 4) * 4;
58 if (c
->vattr_sizes
[attr
] != offset
+ 4)
61 /* Can't get rid of the last VPM read, or the
62 * simulator (at least) throws an error.
64 uint32_t total_size
= 0;
65 for (uint32_t i
= 0; i
< ARRAY_SIZE(c
->vattr_sizes
); i
++)
66 total_size
+= c
->vattr_sizes
[i
];
71 if (inst
->src
[i
].file
== QFILE_VARY
&&
72 c
->input_slots
[inst
->src
[i
].index
].slot
== 0xff) {
81 qir_opt_dead_code(struct vc4_compile
*c
)
83 bool progress
= false;
84 bool *used
= calloc(c
->num_temps
, sizeof(bool));
86 list_for_each_entry_safe_rev(struct qinst
, inst
, &c
->instructions
,
88 if ((inst
->dst
.file
== QFILE_NULL
||
89 (inst
->dst
.file
== QFILE_TEMP
&&
90 !used
[inst
->dst
.index
])) &&
92 !qir_has_side_effects(c
, inst
) &&
93 !has_nonremovable_reads(c
, inst
)) {
94 for (int i
= 0; i
< qir_get_op_nsrc(inst
->op
); i
++) {
95 if (inst
->src
[i
].file
!= QFILE_VPM
)
97 uint32_t attr
= inst
->src
[i
].index
/ 4;
98 uint32_t offset
= (inst
->src
[i
].index
% 4) * 4;
100 if (c
->vattr_sizes
[attr
] == offset
+ 4) {
102 c
->vattr_sizes
[attr
] -= 4;
111 for (int i
= 0; i
< qir_get_op_nsrc(inst
->op
); i
++) {
112 if (inst
->src
[i
].file
== QFILE_TEMP
)
113 used
[inst
->src
[i
].index
] = true;