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11 * The above copyright notice and this permission notice (including the next
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25 #include "nir_builder.h"
27 /** @file nir_opt_conditional_discard.c
29 * Handles optimization of lowering if (cond) discard to discard_if(cond).
33 nir_opt_conditional_discard_block(nir_builder
*b
, nir_block
*block
)
35 if (nir_cf_node_is_first(&block
->cf_node
))
38 nir_cf_node
*prev_node
= nir_cf_node_prev(&block
->cf_node
);
39 if (prev_node
->type
!= nir_cf_node_if
)
42 nir_if
*if_stmt
= nir_cf_node_as_if(prev_node
);
43 nir_block
*then_block
= nir_if_first_then_block(if_stmt
);
44 nir_block
*else_block
= nir_if_first_else_block(if_stmt
);
46 /* check there is only one else block and it is empty */
47 if (nir_if_last_else_block(if_stmt
) != else_block
)
49 if (!exec_list_is_empty(&else_block
->instr_list
))
52 /* check there is only one then block and it has only one instruction in it */
53 if (nir_if_last_then_block(if_stmt
) != then_block
)
55 if (exec_list_is_empty(&then_block
->instr_list
))
57 if (exec_list_length(&then_block
->instr_list
) > 1)
60 * make sure no subsequent phi nodes point at this if.
62 nir_block
*after
= nir_cf_node_as_block(nir_cf_node_next(&if_stmt
->cf_node
));
63 nir_foreach_instr_safe(instr
, after
) {
64 if (instr
->type
!= nir_instr_type_phi
)
66 nir_phi_instr
*phi
= nir_instr_as_phi(instr
);
68 nir_foreach_phi_src(phi_src
, phi
) {
69 if (phi_src
->pred
== then_block
||
70 phi_src
->pred
== else_block
)
75 /* Get the first instruction in the then block and confirm it is
76 * a discard or a discard_if
78 nir_instr
*instr
= nir_block_first_instr(then_block
);
79 if (instr
->type
!= nir_instr_type_intrinsic
)
82 nir_intrinsic_instr
*intrin
= nir_instr_as_intrinsic(instr
);
83 if (intrin
->intrinsic
!= nir_intrinsic_discard
&&
84 intrin
->intrinsic
!= nir_intrinsic_discard_if
)
89 b
->cursor
= nir_before_cf_node(prev_node
);
90 if (intrin
->intrinsic
== nir_intrinsic_discard
)
91 cond
= if_stmt
->condition
;
93 cond
= nir_src_for_ssa(nir_iand(b
,
94 nir_ssa_for_src(b
, if_stmt
->condition
, 1),
95 nir_ssa_for_src(b
, intrin
->src
[0], 1)));
97 nir_intrinsic_instr
*discard_if
=
98 nir_intrinsic_instr_create(b
->shader
, nir_intrinsic_discard_if
);
99 nir_src_copy(&discard_if
->src
[0], &cond
, discard_if
);
101 nir_instr_insert_before_cf(prev_node
, &discard_if
->instr
);
102 nir_instr_remove(&intrin
->instr
);
103 nir_cf_node_remove(&if_stmt
->cf_node
);
109 nir_opt_conditional_discard(nir_shader
*shader
)
111 bool progress
= false;
115 nir_foreach_function(function
, shader
) {
116 if (function
->impl
) {
117 nir_builder_init(&builder
, function
->impl
);
118 nir_foreach_block_safe(block
, function
->impl
) {
119 progress
|= nir_opt_conditional_discard_block(&builder
, block
);