1 /* Search for references that a functions loads or stores.
2 Copyright (C) 2019-2023 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 #ifndef IPA_MODREF_H
21 #define IPA_MODREF_H
22
23 typedef modref_tree <alias_set_type> modref_records;
24 typedef unsigned short eaf_flags_t;
25
26 /* Single function summary. */
27
28 struct GTY(()) modref_summary
29 {
30 /* Load and stores in function (transitively closed to all callees) */
31 modref_records *loads;
32 modref_records *stores;
33 auto_vec<modref_access_node> GTY((skip)) kills;
34 auto_vec<eaf_flags_t> GTY((skip)) arg_flags;
35
36 eaf_flags_t retslot_flags;
37 eaf_flags_t static_chain_flags;
38
39 unsigned writes_errno : 1;
40 /* Side effects does not include memory loads and stores which are
41 expressed using loads, stores and calls_interposable fields. */
42 unsigned side_effects : 1;
43 /* If true function can not be CSE optimized because it may behave
44 differently even if invoked with same inputs. */
45 unsigned nondeterministic : 1;
46 /* IF true the function may read any reachable memory but not use
47 it for anything useful. This may happen i.e. when interposing
48 function with optimized out conditional with unoptimized one.
49
50 In this situation the loads summary is not useful for DSE but
51 it is still useful for CSE. */
52 unsigned calls_interposable : 1;
53
54 /* Flags computed by finalize method. */
55
56 /* Total number of accesses in loads tree. */
57 unsigned int load_accesses;
58 /* global_memory_read is not set for functions calling functions
59 with !binds_to_current_def which, after interposition, may read global
60 memory but do nothing useful with it (except for crashing if some
61 stores are optimized out. */
62 unsigned global_memory_read : 1;
63 unsigned global_memory_written : 1;
64 unsigned try_dse : 1;
65
66
67 modref_summary ();
68 ~modref_summary ();
69 void dump (FILE *);
70 bool useful_p (int ecf_flags, bool check_flags = true);
71 void finalize (tree);
72 };
73
74 modref_summary *get_modref_function_summary (cgraph_node *func);
75 modref_summary *get_modref_function_summary (gcall *call, bool *interposed);
76 void ipa_modref_cc_finalize ();
77 void ipa_merge_modref_summary_after_inlining (cgraph_edge *e);
78
79 /* All flags that are implied by the ECF_CONST functions. */
80 static const int implicit_const_eaf_flags
81 = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
82 | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE
83 | EAF_NO_DIRECT_READ | EAF_NO_INDIRECT_READ
84 | EAF_NOT_RETURNED_INDIRECTLY;
85
86 /* All flags that are implied by the ECF_PURE function. */
87 static const int implicit_pure_eaf_flags
88 = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
89 | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE;
90
91 /* All flags implied when we know we can ignore stores (i.e. when handling
92 call to noreturn). */
93 static const int ignore_stores_eaf_flags
94 = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
95 | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE;
96
97 /* Return slot is write-only. */
98 static const int implicit_retslot_eaf_flags
99 = EAF_NO_DIRECT_READ | EAF_NO_INDIRECT_READ
100 | EAF_NO_INDIRECT_ESCAPE | EAF_NO_INDIRECT_CLOBBER
101 | EAF_NOT_RETURNED_INDIRECTLY;
102
103 /* If function does not bind to current def (i.e. it is inline in comdat
104 section), the modref analysis may not match the behavior of function
105 which will be later symbol interposed to. All side effects must match
106 however it is possible that the other function body contains more loads
107 which may trap.
108 MODREF_FLAGS are flags determined by analysis of function body while
109 FLAGS are flags known otherwise (i.e. by fnspec, pure/const attributes
110 etc.) */
111 inline int
112 interposable_eaf_flags (int modref_flags, int flags)
113 {
114 /* If parameter was previously unused, we know it is only read
115 and its value is not used. */
116 if ((modref_flags & EAF_UNUSED) && !(flags & EAF_UNUSED))
117 {
118 modref_flags &= ~EAF_UNUSED;
119 modref_flags |= EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE
120 | EAF_NOT_RETURNED_DIRECTLY | EAF_NOT_RETURNED_INDIRECTLY
121 | EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER;
122 }
123 /* We can not determine that value is not read at all. */
124 if ((modref_flags & EAF_NO_DIRECT_READ) && !(flags & EAF_NO_DIRECT_READ))
125 modref_flags &= ~EAF_NO_DIRECT_READ;
126 if ((modref_flags & EAF_NO_INDIRECT_READ) && !(flags & EAF_NO_INDIRECT_READ))
127 modref_flags &= ~EAF_NO_INDIRECT_READ;
128 return modref_flags;
129 }
130
131 #endif