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// icf.h --  Identical Code Folding

// Copyright 2009, 2010 Free Software Foundation, Inc.

// Written by Sriraman Tallam <tmsriram@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

#ifndef GOLD_ICF_H

#define GOLD_ICF_H

#include <vector>

#include "elfcpp.h"

#include "symtab.h"

#include "object.h"

namespace gold

{

class Object;

class Input_objects;

class Symbol_table;

class Icf

{

 public:

  typedef std::vector<Section_id> Sections_reachable_info;

  typedef std::vector<Symbol*> Symbol_info;

  typedef std::vector<std::pair<long long, long long> > Addend_info;

  typedef std::vector<uint64_t> Offset_info;

  typedef std::vector<unsigned int> Reloc_addend_size_info;

  typedef Unordered_map<Section_id,

                        unsigned int,

                        Section_id_hash> Uniq_secn_id_map;

  typedef Unordered_set<Section_id, Section_id_hash> Secn_fptr_taken_set;

  typedef struct

  {

    // This stores the section corresponding to the reloc.

    Sections_reachable_info section_info;

    // This stores the symbol corresponding to the reloc.

    Symbol_info symbol_info;

    // This stores the symbol value and the addend for a reloc.

    Addend_info addend_info;

    Offset_info offset_info;

    Reloc_addend_size_info reloc_addend_size_info;

  } Reloc_info;

  typedef Unordered_map<Section_id, Reloc_info,

                        Section_id_hash> Reloc_info_list;

  Icf()

  : id_section_(), section_id_(), kept_section_id_(),

    fptr_section_id_(),

    num_tracked_relocs(NULL), icf_ready_(false),

    reloc_info_list_()

  { }

  // Returns the kept folded identical section corresponding to

  // dup_obj and dup_shndx.

  Section_id

  get_folded_section(Object* dup_obj, unsigned int dup_shndx);

  // Forms groups of identical sections where the first member

  // of each group is the kept section during folding.

  void

  find_identical_sections(const Input_objects* input_objects,

                          Symbol_table* symtab);

  // This is set when ICF has been run and the groups of

  // identical sections have been formed.

  void

  icf_ready()

  { this->icf_ready_ = true; }

  // Returns true if ICF has been run.

  bool

  is_icf_ready()

  { return this->icf_ready_; }

  // Unfolds the section denoted by OBJ and SHNDX if folded.

  void

  unfold_section(Object* obj, unsigned int shndx);

  // Returns the kept section corresponding to the 

  // given section.

  bool

  is_section_folded(Object* obj, unsigned int shndx);

  // Given an object and a section index, this returns true if the

  // pointer of the function defined in this section is taken.

  bool

  section_has_function_pointers(Object* obj, unsigned int shndx)

  {

    return (this->fptr_section_id_.find(Section_id(obj, shndx))

            != this->fptr_section_id_.end());

  }

  // Records that a pointer of the function defined in this section

  // is taken.

  void

  set_section_has_function_pointers(Object* obj, unsigned int shndx)

  {

    this->fptr_section_id_.insert(Section_id(obj, shndx));

  }

  // Checks if the section_name should be searched for relocs

  // corresponding to taken function pointers.  Ignores eh_frame

  // and vtable sections.

  inline bool

  check_section_for_function_pointers(const std::string& section_name,

                                      Target* target)

  {

    return (parameters->options().icf_safe_folding()

            && target->can_check_for_function_pointers()

            && target->section_may_have_icf_unsafe_pointers(

                section_name.c_str()));

  }

  // Returns a map of a section to info (Reloc_info) about its relocations.

  Reloc_info_list&

  reloc_info_list()

  { return this->reloc_info_list_; }

  // Returns a mapping of each section to a unique integer.

  Uniq_secn_id_map&

  section_to_int_map()

  { return this->section_id_; }

 private:

  // Maps integers to sections.

  std::vector<Section_id> id_section_;

  // Does the reverse.

  Uniq_secn_id_map section_id_;

  // Given a section id, this maps it to the id of the kept

  // section.  If the id's are the same then this section is

  // not folded.

  std::vector<unsigned int> kept_section_id_;

  // Given a section id, this says if the pointer to this

  // function is taken in which case it is dangerous to fold

  // this function.

  Secn_fptr_taken_set fptr_section_id_;

  unsigned int* num_tracked_relocs;

  // Flag to indicate if ICF has been run.

  bool icf_ready_;

  // This list is populated by gc_process_relocs in gc.h.

  Reloc_info_list reloc_info_list_;

};

// This function returns true if this section corresponds to a function that

// should be considered by icf as a possible candidate for folding.  Some

// earlier gcc versions, like 4.0.3, put constructors and destructors in

// .gnu.linkonce.t sections and hence should be included too.

inline bool

is_section_foldable_candidate(const std::string& section_name)

{

  const char* section_name_cstr = section_name.c_str();

  return (is_prefix_of(".text", section_name_cstr)

          || is_prefix_of(".gnu.linkonce.t", section_name_cstr));

}

} // End of namespace gold.

#endif