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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;
41 struct simple_node
*node
;
43 struct qreg
*movs
= calloc(c
->num_temps
, sizeof(struct qreg
));
45 foreach(node
, &c
->instructions
) {
46 struct qinst
*inst
= (struct qinst
*)node
;
48 /* A single instruction can only read one uniform value. (It
49 * could maybe read the same uniform value in two operands,
50 * but that doesn't seem important to do).
52 bool reads_a_uniform
= false;
53 for (int i
= 0; i
< qir_get_op_nsrc(inst
->op
); i
++) {
54 if (inst
->src
[i
].file
== QFILE_UNIF
)
55 reads_a_uniform
= true;
58 for (int i
= 0; i
< qir_get_op_nsrc(inst
->op
); i
++) {
59 int index
= inst
->src
[i
].index
;
60 if (inst
->src
[i
].file
== QFILE_TEMP
&&
61 (movs
[index
].file
== QFILE_TEMP
||
62 (movs
[index
].file
== QFILE_UNIF
&&
65 fprintf(stderr
, "Copy propagate: ");
67 fprintf(stderr
, "\n");
70 inst
->src
[i
] = movs
[index
];
71 if (movs
[index
].file
== QFILE_UNIF
)
72 reads_a_uniform
= true;
75 fprintf(stderr
, "to: ");
77 fprintf(stderr
, "\n");
84 if (inst
->op
== QOP_MOV
&& inst
->dst
.file
== QFILE_TEMP
)
85 movs
[inst
->dst
.index
] = inst
->src
[0];