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25 * @file vc4_opt_copy_propagation.c
27 * This implements simple copy propagation for QIR without control flow.
29 * For each temp, it keeps a qreg of which source it was MOVed from, if it
30 * was. If we see that used later, we can just reuse the source value, since
31 * we know we don't have control flow, and we have SSA for our values so
32 * there's no killing to worry about.
38 qir_opt_copy_propagation(struct vc4_compile
*c
)
40 bool progress
= false;
43 list_for_each_entry(struct qinst
, inst
, &c
->instructions
, link
) {
44 int nsrc
= qir_get_op_nsrc(inst
->op
);
45 for (int i
= 0; i
< nsrc
; i
++) {
46 if (inst
->src
[i
].file
!= QFILE_TEMP
)
49 struct qinst
*mov
= c
->defs
[inst
->src
[i
].index
];
51 (mov
->op
!= QOP_MOV
&&
52 mov
->op
!= QOP_FMOV
&&
53 mov
->op
!= QOP_MMOV
)) {
57 if (mov
->src
[0].file
!= QFILE_TEMP
&&
58 mov
->src
[0].file
!= QFILE_UNIF
) {
66 if (mov
->src
[0].pack
) {
67 /* Make sure that the meaning of the unpack
68 * would be the same between the two
71 if (qir_is_float_input(inst
) !=
72 qir_is_float_input(mov
)) {
76 /* There's only one unpack field, so make sure
77 * this instruction doesn't already use it.
79 bool already_has_unpack
= false;
80 for (int j
= 0; j
< nsrc
; j
++) {
81 if (inst
->src
[j
].pack
)
82 already_has_unpack
= true;
84 if (already_has_unpack
)
87 /* A destination pack requires the PM bit to
88 * be set to a specific value already, which
89 * may be different from ours.
94 unpack
= mov
->src
[0].pack
;
96 unpack
= inst
->src
[i
].pack
;
100 fprintf(stderr
, "Copy propagate: ");
101 qir_dump_inst(c
, inst
);
102 fprintf(stderr
, "\n");
105 inst
->src
[i
] = mov
->src
[0];
106 inst
->src
[i
].pack
= unpack
;
109 fprintf(stderr
, "to: ");
110 qir_dump_inst(c
, inst
);
111 fprintf(stderr
, "\n");