| 1 | // icf.h -- Identical Code Folding |
| 2 | |
| 3 | // Copyright 2009, 2010 Free Software Foundation, Inc. |
| 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" |
| 30 | #include "object.h" |
| 31 | |
| 32 | namespace gold |
| 33 | { |
| 34 | |
| 35 | class Object; |
| 36 | class Input_objects; |
| 37 | class Symbol_table; |
| 38 | |
| 39 | class Icf |
| 40 | { |
| 41 | public: |
| 42 | typedef std::vector<Section_id> Sections_reachable_info; |
| 43 | typedef std::vector<Symbol*> Symbol_info; |
| 44 | typedef std::vector<std::pair<long long, long long> > Addend_info; |
| 45 | typedef std::vector<uint64_t> Offset_info; |
| 46 | typedef std::vector<unsigned int> Reloc_addend_size_info; |
| 47 | typedef Unordered_map<Section_id, |
| 48 | unsigned int, |
| 49 | Section_id_hash> Uniq_secn_id_map; |
| 50 | typedef Unordered_set<Section_id, Section_id_hash> Secn_fptr_taken_set; |
| 51 | |
| 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; |
| 61 | Reloc_addend_size_info reloc_addend_size_info; |
| 62 | } Reloc_info; |
| 63 | |
| 64 | typedef Unordered_map<Section_id, Reloc_info, |
| 65 | Section_id_hash> Reloc_info_list; |
| 66 | |
| 67 | Icf() |
| 68 | : id_section_(), section_id_(), kept_section_id_(), |
| 69 | fptr_section_id_(), |
| 70 | num_tracked_relocs(NULL), icf_ready_(false), |
| 71 | reloc_info_list_() |
| 72 | { } |
| 73 | |
| 74 | // Returns the kept folded identical section corresponding to |
| 75 | // dup_obj and dup_shndx. |
| 76 | Section_id |
| 77 | get_folded_section(Object* dup_obj, unsigned int dup_shndx); |
| 78 | |
| 79 | // Forms groups of identical sections where the first member |
| 80 | // of each group is the kept section during folding. |
| 81 | void |
| 82 | find_identical_sections(const Input_objects* input_objects, |
| 83 | Symbol_table* symtab); |
| 84 | |
| 85 | // This is set when ICF has been run and the groups of |
| 86 | // identical sections have been formed. |
| 87 | void |
| 88 | icf_ready() |
| 89 | { this->icf_ready_ = true; } |
| 90 | |
| 91 | // Returns true if ICF has been run. |
| 92 | bool |
| 93 | is_icf_ready() |
| 94 | { return this->icf_ready_; } |
| 95 | |
| 96 | // Unfolds the section denoted by OBJ and SHNDX if folded. |
| 97 | void |
| 98 | unfold_section(Object* obj, unsigned int shndx); |
| 99 | |
| 100 | // Returns the kept section corresponding to the |
| 101 | // given section. |
| 102 | bool |
| 103 | is_section_folded(Object* obj, unsigned int shndx); |
| 104 | |
| 105 | // Given an object and a section index, this returns true if the |
| 106 | // pointer of the function defined in this section is taken. |
| 107 | bool |
| 108 | section_has_function_pointers(Object* obj, unsigned int shndx) |
| 109 | { |
| 110 | return (this->fptr_section_id_.find(Section_id(obj, shndx)) |
| 111 | != this->fptr_section_id_.end()); |
| 112 | } |
| 113 | |
| 114 | // Records that a pointer of the function defined in this section |
| 115 | // is taken. |
| 116 | void |
| 117 | set_section_has_function_pointers(Object* obj, unsigned int shndx) |
| 118 | { |
| 119 | this->fptr_section_id_.insert(Section_id(obj, shndx)); |
| 120 | } |
| 121 | |
| 122 | // Checks if the section_name should be searched for relocs |
| 123 | // corresponding to taken function pointers. Ignores eh_frame |
| 124 | // and vtable sections. |
| 125 | inline bool |
| 126 | check_section_for_function_pointers(const std::string& section_name, |
| 127 | Target* target) |
| 128 | { |
| 129 | return (parameters->options().icf_safe_folding() |
| 130 | && target->can_check_for_function_pointers() |
| 131 | && target->section_may_have_icf_unsafe_pointers( |
| 132 | section_name.c_str())); |
| 133 | } |
| 134 | |
| 135 | // Returns a map of a section to info (Reloc_info) about its relocations. |
| 136 | Reloc_info_list& |
| 137 | reloc_info_list() |
| 138 | { return this->reloc_info_list_; } |
| 139 | |
| 140 | // Returns a mapping of each section to a unique integer. |
| 141 | Uniq_secn_id_map& |
| 142 | section_to_int_map() |
| 143 | { return this->section_id_; } |
| 144 | |
| 145 | private: |
| 146 | |
| 147 | // Maps integers to sections. |
| 148 | std::vector<Section_id> id_section_; |
| 149 | // Does the reverse. |
| 150 | Uniq_secn_id_map section_id_; |
| 151 | // Given a section id, this maps it to the id of the kept |
| 152 | // section. If the id's are the same then this section is |
| 153 | // not folded. |
| 154 | std::vector<unsigned int> kept_section_id_; |
| 155 | // Given a section id, this says if the pointer to this |
| 156 | // function is taken in which case it is dangerous to fold |
| 157 | // this function. |
| 158 | Secn_fptr_taken_set fptr_section_id_; |
| 159 | unsigned int* num_tracked_relocs; |
| 160 | // Flag to indicate if ICF has been run. |
| 161 | bool icf_ready_; |
| 162 | // This list is populated by gc_process_relocs in gc.h. |
| 163 | Reloc_info_list reloc_info_list_; |
| 164 | }; |
| 165 | |
| 166 | // This function returns true if this section corresponds to a function that |
| 167 | // should be considered by icf as a possible candidate for folding. Some |
| 168 | // earlier gcc versions, like 4.0.3, put constructors and destructors in |
| 169 | // .gnu.linkonce.t sections and hence should be included too. |
| 170 | inline bool |
| 171 | is_section_foldable_candidate(const std::string& section_name) |
| 172 | { |
| 173 | const char* section_name_cstr = section_name.c_str(); |
| 174 | return (is_prefix_of(".text", section_name_cstr) |
| 175 | || is_prefix_of(".gnu.linkonce.t", section_name_cstr)); |
| 176 | } |
| 177 | |
| 178 | } // End of namespace gold. |
| 179 | |
| 180 | #endif |