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180 lines
5.6 KiB
C++
180 lines
5.6 KiB
C++
// icf.h -- Identical Code Folding
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// Copyright (C) 2009-2014 Free Software Foundation, Inc.
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// Written by Sriraman Tallam <tmsriram@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#ifndef GOLD_ICF_H
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#define GOLD_ICF_H
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#include <vector>
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#include "elfcpp.h"
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#include "symtab.h"
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#include "object.h"
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namespace gold
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{
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class Object;
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class Input_objects;
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class Symbol_table;
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class Icf
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{
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public:
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typedef std::vector<Section_id> Sections_reachable_info;
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typedef std::vector<Symbol*> Symbol_info;
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typedef std::vector<std::pair<long long, long long> > Addend_info;
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typedef std::vector<uint64_t> Offset_info;
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typedef std::vector<unsigned int> Reloc_addend_size_info;
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typedef Unordered_map<Section_id,
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unsigned int,
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Section_id_hash> Uniq_secn_id_map;
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typedef Unordered_set<Section_id, Section_id_hash> Secn_fptr_taken_set;
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typedef struct
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{
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// This stores the section corresponding to the reloc.
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Sections_reachable_info section_info;
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// This stores the symbol corresponding to the reloc.
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Symbol_info symbol_info;
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// This stores the symbol value and the addend for a reloc.
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Addend_info addend_info;
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Offset_info offset_info;
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Reloc_addend_size_info reloc_addend_size_info;
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} Reloc_info;
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typedef Unordered_map<Section_id, Reloc_info,
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Section_id_hash> Reloc_info_list;
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Icf()
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: id_section_(), section_id_(), kept_section_id_(),
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fptr_section_id_(),
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icf_ready_(false),
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reloc_info_list_()
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{ }
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// Returns the kept folded identical section corresponding to
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// dup_obj and dup_shndx.
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Section_id
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get_folded_section(Object* dup_obj, unsigned int dup_shndx);
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// Forms groups of identical sections where the first member
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// of each group is the kept section during folding.
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void
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find_identical_sections(const Input_objects* input_objects,
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Symbol_table* symtab);
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// This is set when ICF has been run and the groups of
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// identical sections have been formed.
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void
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icf_ready()
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{ this->icf_ready_ = true; }
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// Returns true if ICF has been run.
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bool
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is_icf_ready()
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{ return this->icf_ready_; }
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// Unfolds the section denoted by OBJ and SHNDX if folded.
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void
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unfold_section(Object* obj, unsigned int shndx);
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// Returns the kept section corresponding to the
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// given section.
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bool
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is_section_folded(Object* obj, unsigned int shndx);
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// Given an object and a section index, this returns true if the
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// pointer of the function defined in this section is taken.
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bool
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section_has_function_pointers(Object* obj, unsigned int shndx)
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{
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return (this->fptr_section_id_.find(Section_id(obj, shndx))
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!= this->fptr_section_id_.end());
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}
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// Records that a pointer of the function defined in this section
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// is taken.
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void
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set_section_has_function_pointers(Object* obj, unsigned int shndx)
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{
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this->fptr_section_id_.insert(Section_id(obj, shndx));
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}
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// Checks if the section_name should be searched for relocs
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// corresponding to taken function pointers. Ignores eh_frame
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// and vtable sections.
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inline bool
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check_section_for_function_pointers(const std::string& section_name,
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Target* target)
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{
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return (parameters->options().icf_safe_folding()
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&& target->can_check_for_function_pointers()
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&& target->section_may_have_icf_unsafe_pointers(
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section_name.c_str()));
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}
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// Returns a map of a section to info (Reloc_info) about its relocations.
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Reloc_info_list&
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reloc_info_list()
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{ return this->reloc_info_list_; }
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// Returns a mapping of each section to a unique integer.
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Uniq_secn_id_map&
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section_to_int_map()
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{ return this->section_id_; }
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private:
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// Maps integers to sections.
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std::vector<Section_id> id_section_;
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// Does the reverse.
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Uniq_secn_id_map section_id_;
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// Given a section id, this maps it to the id of the kept
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// section. If the id's are the same then this section is
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// not folded.
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std::vector<unsigned int> kept_section_id_;
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// Given a section id, this says if the pointer to this
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// function is taken in which case it is dangerous to fold
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// this function.
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Secn_fptr_taken_set fptr_section_id_;
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// Flag to indicate if ICF has been run.
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bool icf_ready_;
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// This list is populated by gc_process_relocs in gc.h.
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Reloc_info_list reloc_info_list_;
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};
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// This function returns true if this section corresponds to a function that
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// should be considered by icf as a possible candidate for folding. Some
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// earlier gcc versions, like 4.0.3, put constructors and destructors in
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// .gnu.linkonce.t sections and hence should be included too.
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inline bool
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is_section_foldable_candidate(const std::string& section_name)
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{
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const char* section_name_cstr = section_name.c_str();
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return (is_prefix_of(".text", section_name_cstr)
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|| is_prefix_of(".gnu.linkonce.t", section_name_cstr));
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}
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} // End of namespace gold.
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#endif
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