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 #include "nir.h"
29
30 #pragma once
31
32 #ifdef __cplusplus
33 extern "C" {
34 #endif
35
36 /** NIR Control Flow Modification
37 *
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:
41 *
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
45 * deleting them.
46 */
47
48 /** Control flow insertion. */
49
50 /** puts a control flow node where the cursor is */
51 void nir_cf_node_insert(nir_cursor cursor, nir_cf_node *node);
52
53 /** puts a control flow node immediately after another control flow node */
54 static inline void
nir_cf_node_insert_after(nir_cf_node * node,nir_cf_node * after)55 nir_cf_node_insert_after(nir_cf_node *node, nir_cf_node *after)
56 {
57 nir_cf_node_insert(nir_after_cf_node(node), after);
58 }
59
60 /** puts a control flow node immediately before another control flow node */
61 static inline void
nir_cf_node_insert_before(nir_cf_node * node,nir_cf_node * before)62 nir_cf_node_insert_before(nir_cf_node *node, nir_cf_node *before)
63 {
64 nir_cf_node_insert(nir_before_cf_node(node), before);
65 }
66
67 /** puts a control flow node at the beginning of a list from an if, loop, or function */
68 static inline void
nir_cf_node_insert_begin(struct exec_list * list,nir_cf_node * node)69 nir_cf_node_insert_begin(struct exec_list *list, nir_cf_node *node)
70 {
71 nir_cf_node_insert(nir_before_cf_list(list), node);
72 }
73
74 /** puts a control flow node at the end of a list from an if, loop, or function */
75 static inline void
nir_cf_node_insert_end(struct exec_list * list,nir_cf_node * node)76 nir_cf_node_insert_end(struct exec_list *list, nir_cf_node *node)
77 {
78 nir_cf_node_insert(nir_after_cf_list(list), node);
79 }
80
81
82 /** Control flow motion.
83 *
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:
88 *
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
92 * predecessors:
93 *
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.
97 *
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.
108 *
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.
117 *
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.
121 *
122 * 4. It is invalid to move a piece of IR from one function implementation to
123 * another.
124 *
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).
131 */
132
133 typedef struct {
134 struct exec_list list;
135 nir_function_impl *impl; /* for cleaning up if the list is deleted */
136 } nir_cf_list;
137
138 void nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end);
139
140 void nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor);
141
142 void nir_cf_delete(nir_cf_list *cf_list);
143
144 void nir_cf_list_clone(nir_cf_list *dst, nir_cf_list *src, nir_cf_node *parent,
145 struct hash_table *remap_table);
146
147 static inline void
nir_cf_list_extract(nir_cf_list * extracted,struct exec_list * cf_list)148 nir_cf_list_extract(nir_cf_list *extracted, struct exec_list *cf_list)
149 {
150 nir_cf_extract(extracted, nir_before_cf_list(cf_list),
151 nir_after_cf_list(cf_list));
152 }
153
154 /** removes a control flow node, doing any cleanup necessary */
155 static inline void
nir_cf_node_remove(nir_cf_node * node)156 nir_cf_node_remove(nir_cf_node *node)
157 {
158 nir_cf_list list;
159 nir_cf_extract(&list, nir_before_cf_node(node), nir_after_cf_node(node));
160 nir_cf_delete(&list);
161 }
162
163 #ifdef __cplusplus
164 }
165 #endif
166