b71382fc5977566077f14187076988f0b9e2a054
2 * Copyright © 2014 Intel Corporation
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice (including the next
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
24 * Connor Abbott (cwabbott0@gmail.com)
36 /** NIR Control Flow Modification
38 * This file contains various API's that make modifying control flow in NIR,
39 * while maintaining the invariants checked by the validator, much easier.
40 * There are two parts to this:
42 * 1. Inserting control flow (if's and loops) in various places, for creating
43 * IR either from scratch or as part of some lowering pass.
44 * 2. Taking existing pieces of the IR and either moving them around or
48 /** Control flow insertion. */
50 /** puts a control flow node where the cursor is */
51 void nir_cf_node_insert(nir_cursor cursor
, nir_cf_node
*node
);
53 /** puts a control flow node immediately after another control flow node */
55 nir_cf_node_insert_after(nir_cf_node
*node
, nir_cf_node
*after
)
57 nir_cf_node_insert(nir_after_cf_node(node
), after
);
60 /** puts a control flow node immediately before another control flow node */
62 nir_cf_node_insert_before(nir_cf_node
*node
, nir_cf_node
*before
)
64 nir_cf_node_insert(nir_before_cf_node(node
), before
);
67 /** puts a control flow node at the beginning of a list from an if, loop, or function */
69 nir_cf_node_insert_begin(struct exec_list
*list
, nir_cf_node
*node
)
71 nir_cf_node_insert(nir_before_cf_list(list
), node
);
74 /** puts a control flow node at the end of a list from an if, loop, or function */
76 nir_cf_node_insert_end(struct exec_list
*list
, nir_cf_node
*node
)
78 nir_cf_node_insert(nir_after_cf_list(list
), node
);
82 /** Control flow motion.
84 * These functions let you take a part of a control flow list (basically
85 * equivalent to a series of statement in GLSL) and "extract" it from the IR,
86 * so that it's a free-floating piece of IR that can be either re-inserted
87 * somewhere else or deleted entirely. A few notes on using it:
89 * 1. Phi nodes are considered attached to the piece of control flow that
90 * their sources come from. There are three places where phi nodes can
91 * occur, which are the three places where a block can have multiple
94 * 1) After an if statement, if neither branch ends in a jump.
95 * 2) After a loop, if there are multiple break's.
96 * 3) At the beginning of a loop.
98 * For #1, the phi node is considered to be part of the if, and for #2 and
99 * #3 the phi node is considered to be part of the loop. This allows us to
100 * keep phi's intact, but it means that phi nodes cannot be separated from
101 * the control flow they come from. For example, extracting an if without
102 * extracting all the phi nodes after it is not allowed, and neither is
103 * extracting only some of the phi nodes at the beginning of a block. It
104 * also means that extracting from the beginning of a basic block actually
105 * means extracting from the first non-phi instruction, since there's no
106 * situation where extracting phi nodes without extracting what comes
107 * before them makes any sense.
109 * 2. Phi node sources are guaranteed to remain valid, meaning that they still
110 * correspond one-to-one with the predecessors of the basic block they're
111 * part of. In addition, the original sources will be preserved unless they
112 * correspond to a break or continue that was deleted. However, no attempt
113 * is made to ensure that SSA form is maintained. In particular, it is
114 * *not* guaranteed that definitions of SSA values will dominate all their
115 * uses after all is said and done. Either the caller must ensure that this
116 * is the case, or it must insert extra phi nodes to restore SSA.
118 * 3. It is invalid to move a piece of IR with a break/continue outside of the
119 * loop it references. Doing this will result in invalid
120 * successors/predecessors and phi node sources.
122 * 4. It is invalid to move a piece of IR from one function implementation to
125 * 5. Extracting a control flow list will leave lots of dangling references to
126 * and from other pieces of the IR. It also leaves things in a not 100%
127 * consistent state. This means that some things (e.g. inserting
128 * instructions) might not work reliably on the extracted control flow. It
129 * also means that extracting control flow without re-inserting it or
130 * deleting it is a Bad Thing (tm).
134 struct exec_list list
;
135 nir_function_impl
*impl
; /* for cleaning up if the list is deleted */
138 void nir_cf_extract(nir_cf_list
*extracted
, nir_cursor begin
, nir_cursor end
);
140 void nir_cf_reinsert(nir_cf_list
*cf_list
, nir_cursor cursor
);
142 void nir_cf_delete(nir_cf_list
*cf_list
);
145 nir_cf_list_extract(nir_cf_list
*extracted
, struct exec_list
*cf_list
)
147 nir_cf_extract(extracted
, nir_before_cf_list(cf_list
),
148 nir_after_cf_list(cf_list
));
151 /** removes a control flow node, doing any cleanup necessary */
153 nir_cf_node_remove(nir_cf_node
*node
)
156 nir_cf_extract(&list
, nir_before_cf_node(node
), nir_after_cf_node(node
));
157 nir_cf_delete(&list
);