1 // icf.h -- Identical Code Folding 2 3 // Copyright (C) 2009-2016 Free Software Foundation, Inc. 4 // Written by Sriraman Tallam <tmsriram (at) 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 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(Relobj* 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(Relobj* obj, unsigned int shndx); 99 100 // Returns the kept section corresponding to the 101 // given section. 102 bool 103 is_section_folded(Relobj* 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(Relobj* 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(Relobj* 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 // Flag to indicate if ICF has been run. 160 bool icf_ready_; 161 // This list is populated by gc_process_relocs in gc.h. 162 Reloc_info_list reloc_info_list_; 163 }; 164 165 // This function returns true if this section corresponds to a function that 166 // should be considered by icf as a possible candidate for folding. Some 167 // earlier gcc versions, like 4.0.3, put constructors and destructors in 168 // .gnu.linkonce.t sections and hence should be included too. 169 inline bool 170 is_section_foldable_candidate(const std::string& section_name) 171 { 172 const char* section_name_cstr = section_name.c_str(); 173 return (is_prefix_of(".text", section_name_cstr) 174 || is_prefix_of(".gnu.linkonce.t", section_name_cstr)); 175 } 176 177 } // End of namespace gold. 178 179 #endif 180
