1/*
2 * Copyright © 2014 Intel Corporation
3 *
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:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
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
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 * Authors:
24 *    Connor Abbott (cwabbott0@gmail.com)
25 *
26 */
27
28#ifndef NIR_CONTROL_FLOW_H
29#define NIR_CONTROL_FLOW_H
30
31#include "nir.h"
32
33#ifdef __cplusplus
34extern "C" {
35#endif
36
37/** NIR Control Flow Modification
38 *
39 * This file contains various APIs that make modifying control flow in NIR,
40 * while maintaining the invariants checked by the validator, much easier.
41 * There are two parts to this:
42 *
43 * 1. Inserting control flow (ifs and loops) in various places, for creating
44 *    IR either from scratch or as part of some lowering pass.
45 * 2. Taking existing pieces of the IR and either moving them around or
46 *    deleting them.
47 */
48
49/** Control flow insertion. */
50
51/** puts a control flow node where the cursor is */
52void nir_cf_node_insert(nir_cursor cursor, nir_cf_node *node);
53
54/** puts a control flow node immediately after another control flow node */
55static inline void
56nir_cf_node_insert_after(nir_cf_node *node, nir_cf_node *after)
57{
58   nir_cf_node_insert(nir_after_cf_node(node), after);
59}
60
61/** puts a control flow node immediately before another control flow node */
62static inline void
63nir_cf_node_insert_before(nir_cf_node *node, nir_cf_node *before)
64{
65   nir_cf_node_insert(nir_before_cf_node(node), before);
66}
67
68/** puts a control flow node at the beginning of a list from an if, loop, or function */
69static inline void
70nir_cf_node_insert_begin(struct exec_list *list, nir_cf_node *node)
71{
72   nir_cf_node_insert(nir_before_cf_list(list), node);
73}
74
75/** puts a control flow node at the end of a list from an if, loop, or function */
76static inline void
77nir_cf_node_insert_end(struct exec_list *list, nir_cf_node *node)
78{
79   nir_cf_node_insert(nir_after_cf_list(list), node);
80}
81
82
83/** Control flow motion.
84 *
85 * These functions let you take a part of a control flow list (basically
86 * equivalent to a series of statement in GLSL) and "extract" it from the IR,
87 * so that it's a free-floating piece of IR that can be either re-inserted
88 * somewhere else or deleted entirely. A few notes on using it:
89 *
90 * 1. Phi nodes are considered attached to the piece of control flow that
91 *    their sources come from. There are three places where phi nodes can
92 *    occur, which are the three places where a block can have multiple
93 *    predecessors:
94 *
95 *    1) After an if statement, if neither branch ends in a jump.
96 *    2) After a loop, if there are multiple breaks.
97 *    3) At the beginning of a loop.
98 *
99 *    For #1, the phi node is considered to be part of the if, and for #2 and
100 *    #3 the phi node is considered to be part of the loop. This allows us to
101 *    keep phis intact, but it means that phi nodes cannot be separated from
102 *    the control flow they come from. For example, extracting an if without
103 *    extracting all the phi nodes after it is not allowed, and neither is
104 *    extracting only some of the phi nodes at the beginning of a block. It
105 *    also means that extracting from the beginning of a basic block actually
106 *    means extracting from the first non-phi instruction, since there's no
107 *    situation where extracting phi nodes without extracting what comes
108 *    before them makes any sense.
109 *
110 * 2. Phi node sources are guaranteed to remain valid, meaning that they still
111 *    correspond one-to-one with the predecessors of the basic block they're
112 *    part of. In addition, the original sources will be preserved unless they
113 *    correspond to a break or continue that was deleted. However, no attempt
114 *    is made to ensure that SSA form is maintained. In particular, it is
115 *    *not* guaranteed that definitions of SSA values will dominate all their
116 *    uses after all is said and done. Either the caller must ensure that this
117 *    is the case, or it must insert extra phi nodes to restore SSA.
118 *
119 * 3. It is invalid to move a piece of IR with a break/continue outside of the
120 *    loop it references. Doing this will result in invalid
121 *    successors/predecessors and phi node sources.
122 *
123 * 4. It is invalid to move a piece of IR from one function implementation to
124 *    another.
125 *
126 * 5. Extracting a control flow list will leave lots of dangling references to
127 *    and from other pieces of the IR. It also leaves things in a not 100%
128 *    consistent state. This means that some things (e.g. inserting
129 *    instructions) might not work reliably on the extracted control flow. It
130 *    also means that extracting control flow without re-inserting it or
131 *    deleting it is a Bad Thing (tm).
132 */
133
134typedef struct {
135   struct exec_list list;
136   nir_function_impl *impl; /* for cleaning up if the list is deleted */
137} nir_cf_list;
138
139nir_cursor nir_cf_extract(nir_cf_list *extracted, nir_cursor begin,
140                          nir_cursor end);
141
142nir_cursor nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor);
143
144void nir_cf_delete(nir_cf_list *cf_list);
145
146void nir_cf_list_clone(nir_cf_list *dst, nir_cf_list *src, nir_cf_node *parent,
147                       struct hash_table *remap_table);
148
149static inline void
150nir_cf_list_clone_and_reinsert(nir_cf_list *src_list, nir_cf_node *parent,
151                               nir_cursor cursor,
152                               struct hash_table *remap_table)
153{
154   nir_cf_list list;
155   nir_cf_list_clone(&list, src_list, parent, remap_table);
156   nir_cf_reinsert(&list, cursor);
157}
158
159static inline void
160nir_cf_list_extract(nir_cf_list *extracted, struct exec_list *cf_list)
161{
162   nir_cf_extract(extracted, nir_before_cf_list(cf_list),
163                  nir_after_cf_list(cf_list));
164}
165
166/** removes a control flow node, doing any cleanup necessary */
167static inline void
168nir_cf_node_remove(nir_cf_node *node)
169{
170   nir_cf_list list;
171   nir_cf_extract(&list, nir_before_cf_node(node), nir_after_cf_node(node));
172   nir_cf_delete(&list);
173}
174
175/** inserts undef phi sources from predcessor into phis of the block */
176void nir_insert_phi_undef(nir_block *block, nir_block *pred);
177
178#ifdef __cplusplus
179}
180#endif
181
182#endif /* NIR_CONTROL_FLOW_H */
183