1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
// icf.h -- Identical Code Folding
// Copyright (C) 2009-2016 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_(),
icf_ready_(false),
reloc_info_list_()
{ }
// Returns the kept folded identical section corresponding to
// dup_obj and dup_shndx.
Section_id
get_folded_section(Relobj* 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(Relobj* obj, unsigned int shndx);
// Returns the kept section corresponding to the
// given section.
bool
is_section_folded(Relobj* 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(Relobj* 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(Relobj* 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_;
// 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
|
