1/* Generic dominator tree walker
2 Copyright (C) 2003-2017 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify
8it under the terms of the GNU General Public License as published by
9the Free Software Foundation; either version 3, or (at your option)
10any later version.
11
12GCC is distributed in the hope that it will be useful,
13but WITHOUT ANY WARRANTY; without even the implied warranty of
14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15GNU General Public License for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING3. If not see
19<http://www.gnu.org/licenses/>. */
20
21#ifndef GCC_DOM_WALK_H
22#define GCC_DOM_WALK_H
23
24/**
25 * This is the main class for the dominator walker. It is expected that
26 * consumers will have a custom class inheriting from it, which will over ride
27 * at least one of before_dom_children and after_dom_children to implement the
28 * custom behavior.
29 */
30class dom_walker
31{
32public:
33 static const edge STOP;
34
35 /* Use SKIP_UNREACHBLE_BLOCKS = true when your client can discover
36 that some edges are not executable.
37
38 If a client can discover that a COND, SWITCH or GOTO has a static
39 target in the before_dom_children callback, the taken edge should
40 be returned. The generic walker will clear EDGE_EXECUTABLE on all
41 edges it can determine are not executable.
42
43 You can provide a mapping of basic-block index to RPO if you
44 have that readily available or you do multiple walks. */
45 dom_walker (cdi_direction direction, bool skip_unreachable_blocks = false,
46 int *bb_index_to_rpo = NULL);
47
48 ~dom_walker ();
49
50 /* Walk the dominator tree. */
51 void walk (basic_block);
52
53 /* Function to call before the recursive walk of the dominator children.
54
55 Return value is the always taken edge if the block has multiple outgoing
56 edges, NULL otherwise. When skipping unreachable blocks, the walker
57 uses the taken edge information to clear EDGE_EXECUTABLE on the other
58 edges, exposing unreachable blocks. A NULL return value means all
59 outgoing edges should still be considered executable. A return value
60 of STOP means to stop the domwalk from processing dominated blocks from
61 here. This can be used to process a SEME region only (note domwalk
62 will still do work linear in function size). */
63 virtual edge before_dom_children (basic_block) { return NULL; }
64
65 /* Function to call after the recursive walk of the dominator children. */
66 virtual void after_dom_children (basic_block) {}
67
68private:
69 /* This is the direction of the dominator tree we want to walk. i.e.,
70 if it is set to CDI_DOMINATORS, then we walk the dominator tree,
71 if it is set to CDI_POST_DOMINATORS, then we walk the post
72 dominator tree. */
73 const ENUM_BITFIELD (cdi_direction) m_dom_direction : 2;
74 bool m_skip_unreachable_blocks;
75 bool m_user_bb_to_rpo;
76 basic_block m_unreachable_dom;
77 int *m_bb_to_rpo;
78
79 /* Query whether or not the given block is reachable or not. */
80 bool bb_reachable (struct function *, basic_block);
81
82 /* Given an unreachable block, propagate that property to outgoing
83 and possibly incoming edges for the block. Typically called after
84 determining a block is unreachable in the before_dom_children
85 callback. */
86 void propagate_unreachable_to_edges (basic_block, FILE *, dump_flags_t);
87
88};
89
90#endif
91