1 /* Communication between registering jump thread requests and
2 updating the SSA/CFG for jump threading.
3 Copyright (C) 2013-2023 Free Software Foundation, Inc.
4
5 This file is part of GCC.
6
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
11
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
20
21 #ifndef _TREE_SSA_THREADUPDATE_H
22 #define _TREE_SSA_THREADUPDATE_H 1
23
24 enum jump_thread_edge_type
25 {
26 EDGE_START_JUMP_THREAD,
27 EDGE_COPY_SRC_BLOCK,
28 EDGE_COPY_SRC_JOINER_BLOCK,
29 EDGE_NO_COPY_SRC_BLOCK
30 };
31
32 // We keep the registered jump threading opportunities in this
33 // vector as edge pairs (original_edge, target_edge).
34
35 class jump_thread_edge
36 {
37 public:
38 jump_thread_edge (edge e, jump_thread_edge_type t) : e (e), type (t) {}
39
40 edge e;
41 jump_thread_edge_type type;
42 };
43
44 class jump_thread_path_allocator
45 {
46 public:
47 jump_thread_path_allocator ();
48 ~jump_thread_path_allocator ();
49 jump_thread_edge *allocate_thread_edge (edge, jump_thread_edge_type);
50 vec<jump_thread_edge *> *allocate_thread_path ();
51 private:
52 DISABLE_COPY_AND_ASSIGN (jump_thread_path_allocator);
53 obstack m_obstack;
54 };
55
56 // Abstract class for the jump thread registry.
57 //
58 // When all candidates have been registered with
59 // register_jump_thread(), thread_through_all_blocks() is called to
60 // update the CFG.
61
62 class jt_path_registry
63 {
64 public:
65 jt_path_registry (bool backedge_threads);
66 virtual ~jt_path_registry ();
67 bool register_jump_thread (vec<jump_thread_edge *> *);
68 bool thread_through_all_blocks (bool peel_loop_headers);
69 void push_edge (vec<jump_thread_edge *> *path, edge, jump_thread_edge_type);
70 vec<jump_thread_edge *> *allocate_thread_path ();
71 void debug ();
72 protected:
73 void debug_path (FILE *, int pathno);
74 vec<vec<jump_thread_edge *> *> m_paths;
75 unsigned long m_num_threaded_edges;
76 private:
77 virtual bool update_cfg (bool peel_loop_headers) = 0;
78 bool cancel_invalid_paths (vec<jump_thread_edge *> &path);
79 jump_thread_path_allocator m_allocator;
80 // True if threading through back edges is allowed. This is only
81 // allowed in the generic copier in the backward threader.
82 bool m_backedge_threads;
83 DISABLE_COPY_AND_ASSIGN (jt_path_registry);
84 };
85
86 // Forward threader path registry using a custom BB copier.
87
88 class fwd_jt_path_registry : public jt_path_registry
89 {
90 public:
91 fwd_jt_path_registry ();
92 ~fwd_jt_path_registry ();
93 void remove_jump_threads_including (edge);
94 private:
95 bool update_cfg (bool peel_loop_headers) override;
96 void mark_threaded_blocks (bitmap threaded_blocks);
97 bool thread_block_1 (basic_block, bool noloop_only, bool joiners);
98 bool thread_block (basic_block, bool noloop_only);
99 bool thread_through_loop_header (class loop *loop,
100 bool may_peel_loop_headers);
101 class redirection_data *lookup_redirection_data (edge e, enum insert_option);
102
103 hash_table<struct removed_edges> *m_removed_edges;
104
105 // Main data structure to hold information for duplicates of BB.
106 hash_table<redirection_data> *m_redirection_data;
107 };
108
109 // Backward threader path registry using a generic BB copier.
110
111 class back_jt_path_registry : public jt_path_registry
112 {
113 public:
114 back_jt_path_registry ();
115 private:
116 bool update_cfg (bool peel_loop_headers) override;
117 void adjust_paths_after_duplication (unsigned curr_path_num);
118 bool duplicate_thread_path (edge entry, edge exit, basic_block *region,
119 unsigned n_region, unsigned current_path_no);
120 bool rewire_first_differing_edge (unsigned path_num, unsigned edge_num);
121 };
122
123 // Rather than search all the edges in jump thread paths each time DOM
124 // is able to simply if control statement, we build a hash table with
125 // the deleted edges. We only care about the address of the edge, not
126 // its contents.
127 struct removed_edges : nofree_ptr_hash<edge_def>
128 {
129 static hashval_t hash (edge e) { return htab_hash_pointer (e); }
130 static bool equal (edge e1, edge e2) { return e1 == e2; }
131 };
132
133 extern unsigned int estimate_threading_killed_stmts (basic_block);
134
135 enum bb_dom_status
136 {
137 /* BB does not dominate latch of the LOOP. */
138 DOMST_NONDOMINATING,
139 /* The LOOP is broken (there is no path from the header to its latch. */
140 DOMST_LOOP_BROKEN,
141 /* BB dominates the latch of the LOOP. */
142 DOMST_DOMINATING
143 };
144
145 enum bb_dom_status determine_bb_domination_status (class loop *, basic_block);
146
147 // In tree-ssa-dom.cc.
148 extern void free_dom_edge_info (edge);
149
150 #endif