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ef15dade ST |
1 | // icf.h -- Identical Code Folding |
2 | ||
b3adc24a | 3 | // Copyright (C) 2009-2020 Free Software Foundation, Inc. |
ef15dade ST |
4 | // Written by Sriraman Tallam <tmsriram@google.com>. |
5 | ||
6 | // This file is part of gold. | |
7 | ||
8 | // This program is free software; you can redistribute it and/or modify | |
9 | // it under the terms of the GNU General Public License as published by | |
10 | // the Free Software Foundation; either version 3 of the License, or | |
11 | // (at your option) any later version. | |
12 | ||
13 | // This program is distributed in the hope that it will be useful, | |
14 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | // GNU General Public License for more details. | |
17 | ||
18 | // You should have received a copy of the GNU General Public License | |
19 | // along with this program; if not, write to the Free Software | |
20 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
21 | // MA 02110-1301, USA. | |
22 | ||
23 | #ifndef GOLD_ICF_H | |
24 | #define GOLD_ICF_H | |
25 | ||
26 | #include <vector> | |
27 | ||
28 | #include "elfcpp.h" | |
29 | #include "symtab.h" | |
5ac169d4 | 30 | #include "object.h" |
ef15dade ST |
31 | |
32 | namespace gold | |
33 | { | |
34 | ||
35 | class Object; | |
36 | class Input_objects; | |
37 | class Symbol_table; | |
38 | ||
ef15dade ST |
39 | class Icf |
40 | { | |
41 | public: | |
b487ad64 | 42 | typedef std::vector<Section_id> Sections_reachable_info; |
ef15dade ST |
43 | typedef std::vector<Symbol*> Symbol_info; |
44 | typedef std::vector<std::pair<long long, long long> > Addend_info; | |
b487ad64 | 45 | typedef std::vector<uint64_t> Offset_info; |
41cbeecc | 46 | typedef std::vector<unsigned int> Reloc_addend_size_info; |
ef15dade ST |
47 | typedef Unordered_map<Section_id, |
48 | unsigned int, | |
49 | Section_id_hash> Uniq_secn_id_map; | |
21bb3914 | 50 | typedef Unordered_set<Section_id, Section_id_hash> Secn_fptr_taken_set; |
ef15dade | 51 | |
b487ad64 ST |
52 | typedef struct |
53 | { | |
54 | // This stores the section corresponding to the reloc. | |
55 | Sections_reachable_info section_info; | |
56 | // This stores the symbol corresponding to the reloc. | |
57 | Symbol_info symbol_info; | |
58 | // This stores the symbol value and the addend for a reloc. | |
59 | Addend_info addend_info; | |
60 | Offset_info offset_info; | |
41cbeecc | 61 | Reloc_addend_size_info reloc_addend_size_info; |
b487ad64 ST |
62 | } Reloc_info; |
63 | ||
64 | typedef Unordered_map<Section_id, Reloc_info, | |
65 | Section_id_hash> Reloc_info_list; | |
66 | ||
e173ea00 JO |
67 | // A region of some other section that should be considered part of |
68 | // a section for ICF purposes. This is used to avoid folding sections | |
69 | // that have identical text and relocations but different .eh_frame | |
70 | // information. | |
71 | typedef struct | |
72 | { | |
73 | Section_id section; | |
74 | section_offset_type offset; | |
75 | section_size_type length; | |
76 | } Extra_identity_info; | |
77 | ||
78 | typedef std::multimap<Section_id, Extra_identity_info> Extra_identity_list; | |
79 | ||
ef15dade ST |
80 | Icf() |
81 | : id_section_(), section_id_(), kept_section_id_(), | |
21bb3914 | 82 | fptr_section_id_(), |
43819297 | 83 | icf_ready_(false), |
b487ad64 | 84 | reloc_info_list_() |
ef15dade ST |
85 | { } |
86 | ||
87 | // Returns the kept folded identical section corresponding to | |
88 | // dup_obj and dup_shndx. | |
89 | Section_id | |
efc6fa12 | 90 | get_folded_section(Relobj* dup_obj, unsigned int dup_shndx); |
ef15dade ST |
91 | |
92 | // Forms groups of identical sections where the first member | |
93 | // of each group is the kept section during folding. | |
94 | void | |
95 | find_identical_sections(const Input_objects* input_objects, | |
96 | Symbol_table* symtab); | |
97 | ||
98 | // This is set when ICF has been run and the groups of | |
99 | // identical sections have been formed. | |
100 | void | |
101 | icf_ready() | |
102 | { this->icf_ready_ = true; } | |
103 | ||
104 | // Returns true if ICF has been run. | |
105 | bool | |
106 | is_icf_ready() | |
107 | { return this->icf_ready_; } | |
108 | ||
48c187ce ST |
109 | // Unfolds the section denoted by OBJ and SHNDX if folded. |
110 | void | |
efc6fa12 | 111 | unfold_section(Relobj* obj, unsigned int shndx); |
48c187ce | 112 | |
43819297 | 113 | // Returns the kept section corresponding to the |
ef15dade ST |
114 | // given section. |
115 | bool | |
efc6fa12 | 116 | is_section_folded(Relobj* obj, unsigned int shndx); |
21bb3914 ST |
117 | |
118 | // Given an object and a section index, this returns true if the | |
119 | // pointer of the function defined in this section is taken. | |
120 | bool | |
efc6fa12 | 121 | section_has_function_pointers(Relobj* obj, unsigned int shndx) |
21bb3914 ST |
122 | { |
123 | return (this->fptr_section_id_.find(Section_id(obj, shndx)) | |
124 | != this->fptr_section_id_.end()); | |
125 | } | |
126 | ||
127 | // Records that a pointer of the function defined in this section | |
128 | // is taken. | |
129 | void | |
efc6fa12 | 130 | set_section_has_function_pointers(Relobj* obj, unsigned int shndx) |
21bb3914 ST |
131 | { |
132 | this->fptr_section_id_.insert(Section_id(obj, shndx)); | |
133 | } | |
134 | ||
135 | // Checks if the section_name should be searched for relocs | |
136 | // corresponding to taken function pointers. Ignores eh_frame | |
137 | // and vtable sections. | |
138 | inline bool | |
8a75a161 | 139 | check_section_for_function_pointers(const std::string& section_name, |
21bb3914 ST |
140 | Target* target) |
141 | { | |
142 | return (parameters->options().icf_safe_folding() | |
143 | && target->can_check_for_function_pointers() | |
8a75a161 DK |
144 | && target->section_may_have_icf_unsafe_pointers( |
145 | section_name.c_str())); | |
21bb3914 ST |
146 | } |
147 | ||
b487ad64 ST |
148 | // Returns a map of a section to info (Reloc_info) about its relocations. |
149 | Reloc_info_list& | |
150 | reloc_info_list() | |
151 | { return this->reloc_info_list_; } | |
43819297 | 152 | |
e173ea00 JO |
153 | // Returns a map from section to region of a different section that should |
154 | // be considered part of the key section for ICF purposes. | |
155 | Extra_identity_list& | |
156 | extra_identity_list() | |
157 | { return this->extra_identity_list_; } | |
158 | ||
ef15dade ST |
159 | // Returns a mapping of each section to a unique integer. |
160 | Uniq_secn_id_map& | |
161 | section_to_int_map() | |
162 | { return this->section_id_; } | |
163 | ||
164 | private: | |
165 | ||
e173ea00 JO |
166 | bool |
167 | add_ehframe_links(Relobj* object, unsigned int ehframe_shndx, | |
168 | Reloc_info& ehframe_relocs); | |
169 | ||
ef15dade ST |
170 | // Maps integers to sections. |
171 | std::vector<Section_id> id_section_; | |
172 | // Does the reverse. | |
173 | Uniq_secn_id_map section_id_; | |
174 | // Given a section id, this maps it to the id of the kept | |
175 | // section. If the id's are the same then this section is | |
176 | // not folded. | |
177 | std::vector<unsigned int> kept_section_id_; | |
21bb3914 ST |
178 | // Given a section id, this says if the pointer to this |
179 | // function is taken in which case it is dangerous to fold | |
180 | // this function. | |
181 | Secn_fptr_taken_set fptr_section_id_; | |
ef15dade ST |
182 | // Flag to indicate if ICF has been run. |
183 | bool icf_ready_; | |
b487ad64 ST |
184 | // This list is populated by gc_process_relocs in gc.h. |
185 | Reloc_info_list reloc_info_list_; | |
e173ea00 JO |
186 | // Regions of other sections that should be considered part of |
187 | // each section for ICF purposes. | |
188 | Extra_identity_list extra_identity_list_; | |
ef15dade ST |
189 | }; |
190 | ||
55a2bb35 ST |
191 | // This function returns true if this section corresponds to a function that |
192 | // should be considered by icf as a possible candidate for folding. Some | |
193 | // earlier gcc versions, like 4.0.3, put constructors and destructors in | |
194 | // .gnu.linkonce.t sections and hence should be included too. | |
e173ea00 JO |
195 | // The mechanism used to safely fold functions referenced by .eh_frame |
196 | // requires folding .gcc_except_table sections as well; see "Notes regarding | |
197 | // C++ exception handling" at the top of icf.cc for an explanation why. | |
55a2bb35 | 198 | inline bool |
4e271fff | 199 | is_section_foldable_candidate(const std::string& section_name) |
55a2bb35 | 200 | { |
4e271fff ST |
201 | const char* section_name_cstr = section_name.c_str(); |
202 | return (is_prefix_of(".text", section_name_cstr) | |
e173ea00 | 203 | || is_prefix_of(".gcc_except_table", section_name_cstr) |
4e271fff | 204 | || is_prefix_of(".gnu.linkonce.t", section_name_cstr)); |
55a2bb35 ST |
205 | } |
206 | ||
ef15dade ST |
207 | } // End of namespace gold. |
208 | ||
209 | #endif |