gold/icf.h

   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_list;
  43   typedef std::vector<Symbol*> Symbol_info;
  44   typedef std::vector<std::pair<long long, long long> > Addend_info;
  45   typedef Unordered_map<Section_id,
  46                         Sections_reachable_list,
  47                         Section_id_hash> Section_list;
  48   typedef Unordered_map<Section_id, Symbol_info, Section_id_hash> Symbol_list;
  49   typedef Unordered_map<Section_id, Addend_info, Section_id_hash> Addend_list;
  50   typedef Unordered_map<Section_id,
  51                         unsigned int,
  52                         Section_id_hash> Uniq_secn_id_map;
  53
  54   Icf()
  55   : id_section_(), section_id_(), kept_section_id_(),
  56     num_tracked_relocs(NULL), icf_ready_(false),
  57     section_reloc_list_(), symbol_reloc_list_(),
  58     addend_reloc_list_()
  59   { }
  60
  61   // Returns the kept folded identical section corresponding to
  62   // dup_obj and dup_shndx.
  63   Section_id
  64   get_folded_section(Object* dup_obj, unsigned int dup_shndx);
  65
  66   // Forms groups of identical sections where the first member
  67   // of each group is the kept section during folding.
  68   void
  69   find_identical_sections(const Input_objects* input_objects,
  70                           Symbol_table* symtab);
  71
  72   // This is set when ICF has been run and the groups of
  73   // identical sections have been formed.
  74   void
  75   icf_ready()
  76   { this->icf_ready_ = true; }
  77
  78   // Returns true if ICF has been run.
  79   bool
  80   is_icf_ready()
  81   { return this->icf_ready_; }
  82
  83   // Unfolds the section denoted by OBJ and SHNDX if folded.
  84   void
  85   unfold_section(Object* obj, unsigned int shndx);
  86
  87   // Returns the kept section corresponding to the
  88   // given section.
  89   bool
  90   is_section_folded(Object* obj, unsigned int shndx);
  91
  92   // Returns a map of a section to a list of all sections referenced
  93   // by its relocations.
  94   Section_list&
  95   section_reloc_list()
  96   { return this->section_reloc_list_; }
  97
  98   // Returns a map of  a section to a list of all symbols referenced
  99   // by its relocations.
 100   Symbol_list&
 101   symbol_reloc_list()
 102   { return this->symbol_reloc_list_; }
 103
 104   // Returns a maps of a section to a list of symbol values and addends
 105   // of its relocations.
 106   Addend_list&
 107   addend_reloc_list()
 108   { return this->addend_reloc_list_; }
 109
 110   // Returns a mapping of each section to a unique integer.
 111   Uniq_secn_id_map&
 112   section_to_int_map()
 113   { return this->section_id_; }
 114
 115  private:
 116
 117   // Maps integers to sections.
 118   std::vector<Section_id> id_section_;
 119   // Does the reverse.
 120   Uniq_secn_id_map section_id_;
 121   // Given a section id, this maps it to the id of the kept
 122   // section.  If the id's are the same then this section is
 123   // not folded.
 124   std::vector<unsigned int> kept_section_id_;
 125   unsigned int* num_tracked_relocs;
 126   // Flag to indicate if ICF has been run.
 127   bool icf_ready_;
 128
 129   // These lists are populated by gc_process_relocs in gc.h.
 130   Section_list section_reloc_list_;
 131   Symbol_list symbol_reloc_list_;
 132   Addend_list addend_reloc_list_;
 133 };
 134
 135 // This function returns true if this section corresponds to a function that
 136 // should be considered by icf as a possible candidate for folding.  Some
 137 // earlier gcc versions, like 4.0.3, put constructors and destructors in
 138 // .gnu.linkonce.t sections and hence should be included too.
 139 inline bool
 140 is_section_foldable_candidate(const char* section_name)
 141 {
 142   return (is_prefix_of(".text", section_name)
 143           || is_prefix_of(".gnu.linkonce.t", section_name));
 144 }
 145
 146 } // End of namespace gold.
 147
 148 #endif