+2009-08-05 Sriraman Tallam <tmsriram@google.com>
+
+ * icf.cc: New file.
+ * icf.h: New file.
+ * Makefile.am (CCFILES): Add icf.cc.
+ (HFILES): Add icf.h
+ * Makefile.in: Regenerate.
+ * dynobj.h (Sized_dynobj::do_section_entsize): New function.
+ * gc.h (gc_process_relocs): Populate lists used by icf to contain
+ section, symbol and addend information for the relocs.
+ * gold.cc (queue_middle_tasks): Call identical code folding.
+ * gold.h: Add defines for multimap.
+ * layout.cc (Layout::create_symtab_sections): Add symtab as parameter
+ to the call of finalize_local_symbols.
+ * main.cc (main): Create object of class Icf.
+ * object.cc (Sized_relobj::do_layout): Allow this function to be
+ called twice during icf.
+ (Sized_relobj::do_finalize_local_symbols): Fold symbols corresponding
+ to sections marked as identical by icf.
+ (Sized_relobj::do_section_flags): Get section_flags from Symbols_data
+ when available.
+ (Sized_relobj::do_section_entsize): New function.
+ * object.h (Object::section_entsize): New function.
+ (Object::do_section_entsize): New pure virtual function.
+ (Relobj::finalize_local_symbols): Add new parameter.
+ (Relobj::do_section_entsize): New function.
+ * options.h (General_options::icf): New option.
+ (General_options::icf_iterations): New option.
+ (General_options::print_icf_sections): New option.
+ * plugin.cc (Sized_pluginobj::do_section_entsize): New function.
+ * plugin.h (Sized_pluginobj::do_section_entsize): New function.
+ * reloc.cc (Read_relocs::run): Delay scanning relocs when doing
+ icf.
+ * symtab.cc (Symbol_table::is_section_folded): New function.
+ (Symbol_table::sized_finalize_symbol): Fold symbols corresponding
+ to sections marked as identical by icf.
+ * symtab.h (Symbol_table::set_icf): New function.
+ (Symbol_table::icf): New function.
+ (Symbol_table::is_section_folded): New function.
+ (Symbol_table::icf_): New data member.
+ * target-reloc.h (relocate_section): Ignore sections folded by icf.
+ * testsuite/Makefile.am: Add commands to build icf_test.
+ * testsuite/Makefile.in: Regenerate.
+ * testsuite/icf_test.sh: New file.
+ * testsuite/icf_test.cc: New file.
+
2009-07-24 Chris Demetriou <cgd@google.com>
* layout.cc (is_compressible_debug_section): Fix incorrect
gc.cc \
gold.cc \
gold-threads.cc \
+ icf.cc \
incremental.cc \
layout.cc \
mapfile.cc \
gc.h \
gold.h \
gold-threads.h \
+ icf.h \
layout.h \
mapfile.h \
merge.h \
dirsearch.$(OBJEXT) dynobj.$(OBJEXT) dwarf_reader.$(OBJEXT) \
ehframe.$(OBJEXT) errors.$(OBJEXT) expression.$(OBJEXT) \
fileread.$(OBJEXT) gc.$(OBJEXT) gold.$(OBJEXT) \
- gold-threads.$(OBJEXT) incremental.$(OBJEXT) layout.$(OBJEXT) \
- mapfile.$(OBJEXT) merge.$(OBJEXT) object.$(OBJEXT) \
- options.$(OBJEXT) output.$(OBJEXT) parameters.$(OBJEXT) \
- plugin.$(OBJEXT) readsyms.$(OBJEXT) \
+ gold-threads.$(OBJEXT) icf.$(OBJEXT) incremental.$(OBJEXT) \
+ layout.$(OBJEXT) mapfile.$(OBJEXT) merge.$(OBJEXT) \
+ object.$(OBJEXT) options.$(OBJEXT) output.$(OBJEXT) \
+ parameters.$(OBJEXT) plugin.$(OBJEXT) readsyms.$(OBJEXT) \
reduced_debug_output.$(OBJEXT) reloc.$(OBJEXT) \
resolve.$(OBJEXT) script-sections.$(OBJEXT) script.$(OBJEXT) \
stringpool.$(OBJEXT) symtab.$(OBJEXT) target.$(OBJEXT) \
gc.cc \
gold.cc \
gold-threads.cc \
+ icf.cc \
incremental.cc \
layout.cc \
mapfile.cc \
gc.h \
gold.h \
gold-threads.h \
+ icf.h \
layout.h \
mapfile.h \
merge.h \
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/gold-threads.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/gold.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/i386.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/icf.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/incremental.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/layout.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/main.Po@am__quote@
do_section_flags(unsigned int shndx)
{ return this->elf_file_.section_flags(shndx); }
+ // Not used for dynobj.
+ uint64_t
+ do_section_entsize(unsigned int )
+ { gold_unreachable(); }
+
// Return section address.
uint64_t
do_section_address(unsigned int shndx)
#define GOLD_GC_H
#include <queue>
+#include <vector>
#include "elfcpp.h"
#include "symtab.h"
{ return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; }
};
+ public:
+
typedef Unordered_set<Section_id, Section_id_hash> Sections_reachable;
typedef std::map<Section_id, Sections_reachable> Section_ref;
typedef std::queue<Section_id> Worklist_type;
- public :
- Garbage_collection()
- :is_worklist_ready_(false)
- { }
-
- // Accessor methods for the private members.
-
- Sections_reachable&
- referenced_list()
- { return referenced_list_; }
-
- Section_ref&
- section_reloc_map()
- { return section_reloc_map_; }
-
- Worklist_type&
- worklist()
- { return work_list_; }
-
- bool
- is_worklist_ready()
- { return is_worklist_ready_; }
-
- void
- worklist_ready()
- { is_worklist_ready_ = true; }
-
- void
- do_transitive_closure();
-
- private :
- Worklist_type work_list_;
- bool is_worklist_ready_;
- Section_ref section_reloc_map_;
- Sections_reachable referenced_list_;
+ Garbage_collection()
+ : is_worklist_ready_(false)
+ { }
+
+ // Accessor methods for the private members.
+
+ Sections_reachable&
+ referenced_list()
+ { return referenced_list_; }
+
+ Section_ref&
+ section_reloc_map()
+ { return this->section_reloc_map_; }
+
+ Worklist_type&
+ worklist()
+ { return this->work_list_; }
+
+ bool
+ is_worklist_ready()
+ { return this->is_worklist_ready_; }
+
+ void
+ worklist_ready()
+ { this->is_worklist_ready_ = true; }
+
+ void
+ do_transitive_closure();
+
+ bool
+ is_section_garbage(Object* obj, unsigned int shndx)
+ { return (this->referenced_list().find(Section_id(obj, shndx))
+ == this->referenced_list().end()); }
+ private:
+
+ Worklist_type work_list_;
+ bool is_worklist_ready_;
+ Section_ref section_reloc_map_;
+ Sections_reachable referenced_list_;
};
// Data to pass between successive invocations of do_layout
section_size_type symbol_names_size;
};
-// This function implements the the generic part of reloc
-// processing to map a section to all the sections it
-// references through relocs. It is used only during garbage
-// collection.
+// This function implements the generic part of reloc
+// processing to map a section to all the sections it
+// references through relocs. It is called only during
+// garbage collection (--gc-sections) and identical code
+// folding (--icf).
template<int size, bool big_endian, typename Target_type, int sh_type,
typename Scan>
Symbol_table* symtab,
Layout*,
Target_type* ,
- Sized_relobj<size, big_endian>* object,
- unsigned int data_shndx,
+ Sized_relobj<size, big_endian>* src_obj,
+ unsigned int src_indx,
const unsigned char* prelocs,
size_t reloc_count,
Output_section*,
size_t local_count,
const unsigned char* plocal_syms)
{
- Object *src_obj, *dst_obj;
- unsigned int src_indx, dst_indx;
+ Object *dst_obj;
+ unsigned int dst_indx;
- src_obj = object;
- src_indx = data_shndx;
-
typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
+ std::vector<Section_id>* secvec = NULL;
+ std::vector<Symbol*>* symvec = NULL;
+ std::vector<std::pair<long long, long long> >* addendvec = NULL;
+ bool is_icf_tracked = false;
+
+ if (parameters->options().icf()
+ && is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))
+ {
+ is_icf_tracked = true;
+ Section_id src_id(src_obj, src_indx);
+ secvec = &symtab->icf()->section_reloc_list()[src_id];
+ symvec = &symtab->icf()->symbol_reloc_list()[src_id];
+ addendvec = &symtab->icf()->addend_reloc_list()[src_id];
+ }
+
for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
{
Reltype reloc(prelocs);
typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
-
+ typename elfcpp::Elf_types<size>::Elf_Swxword addend =
+ Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&reloc);
+
if (r_sym < local_count)
{
gold_assert(plocal_syms != NULL);
+ r_sym * sym_size);
unsigned int shndx = lsym.get_st_shndx();
bool is_ordinary;
- shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
- if (!is_ordinary)
+ shndx = src_obj->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
+ if (!is_ordinary)
continue;
dst_obj = src_obj;
- if (shndx == src_indx)
- continue;
dst_indx = shndx;
+ Section_id dst_id(dst_obj, dst_indx);
+ if (is_icf_tracked)
+ {
+ (*secvec).push_back(dst_id);
+ (*symvec).push_back(NULL);
+ long long symvalue = static_cast<long long>(lsym.get_st_value());
+ (*addendvec).push_back(std::make_pair(symvalue,
+ static_cast<long long>(addend)));
+ }
+ if (shndx == src_indx)
+ continue;
}
else
{
- Symbol* gsym = object->global_symbol(r_sym);
+ Symbol* gsym = src_obj->global_symbol(r_sym);
gold_assert(gsym != NULL);
if (gsym->is_forwarder())
gsym = symtab->resolve_forwards(gsym);
dst_indx = gsym->shndx(&is_ordinary);
if (!is_ordinary)
continue;
+ Section_id dst_id(dst_obj, dst_indx);
+ if (is_icf_tracked)
+ {
+ (*secvec).push_back(dst_id);
+ (*symvec).push_back(gsym);
+ Sized_symbol<size>* sized_gsym =
+ static_cast<Sized_symbol<size>* >(gsym);
+ long long symvalue =
+ static_cast<long long>(sized_gsym->value());
+ (*addendvec).push_back(std::make_pair(symvalue,
+ static_cast<long long>(addend)));
+ }
}
- Section_id p1(src_obj, src_indx);
- Section_id p2(dst_obj, dst_indx);
- Garbage_collection::Section_ref::iterator map_it;
- map_it = symtab->gc()->section_reloc_map().find(p1);
- if (map_it == symtab->gc()->section_reloc_map().end())
- {
- symtab->gc()->section_reloc_map()[p1].insert(p2);
- }
- else
+ if (parameters->options().gc_sections())
{
- Garbage_collection::Sections_reachable& v(map_it->second);
- v.insert(p2);
+ Section_id src_id(src_obj, src_indx);
+ Section_id dst_id(dst_obj, dst_indx);
+ Garbage_collection::Section_ref::iterator map_it;
+ map_it = symtab->gc()->section_reloc_map().find(src_id);
+ if (map_it == symtab->gc()->section_reloc_map().end())
+ {
+ symtab->gc()->section_reloc_map()[src_id].insert(dst_id);
+ }
+ else
+ {
+ Garbage_collection::Sections_reachable& v(map_it->second);
+ v.insert(dst_id);
+ }
}
}
return;
#include "reloc.h"
#include "defstd.h"
#include "plugin.h"
+#include "icf.h"
namespace gold
{
}
if (parameters->options().relocatable()
- && parameters->options().gc_sections())
- gold_error(_("cannot mix -r with garbage collection"));
+ && (parameters->options().gc_sections() || parameters->options().icf()))
+ gold_error(_("cannot mix -r with --gc-sections or --icf"));
- if (parameters->options().gc_sections())
+ if (parameters->options().gc_sections() || parameters->options().icf())
{
workqueue->queue(new Task_function(new Gc_runner(options,
input_objects,
gold_assert(symtab->gc() != NULL);
// Do a transitive closure on all references to determine the worklist.
symtab->gc()->do_transitive_closure();
- // Call do_layout again to determine the output_sections for all
- // referenced input sections.
+ }
+
+ // If identical code folding (--icf) is chosen it makes sense to do it
+ // only after garbage collection (--gc-sections) as we do not want to
+ // be folding sections that will be garbage.
+ if (parameters->options().icf())
+ {
+ symtab->icf()->find_identical_sections(input_objects, symtab);
+ }
+
+ // Call Object::layout for the second time to determine the
+ // output_sections for all referenced input sections. When
+ // --gc-sections or --icf is turned on, Object::layout is
+ // called twice. It is called the first time when the
+ // symbols are added.
+ if (parameters->options().gc_sections() || parameters->options().icf())
+ {
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
(*p)->layout(symtab, layout, NULL);
}
}
+
// Layout deferred objects due to plugins.
if (parameters->options().has_plugins())
{
gold_assert(plugins != NULL);
plugins->layout_deferred_objects();
}
- if (parameters->options().gc_sections())
+
+ if (parameters->options().gc_sections() || parameters->options().icf())
{
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
// If doing garbage collection, the relocations have already been read.
// Otherwise, read and scan the relocations.
- if (parameters->options().gc_sections())
+ if (parameters->options().gc_sections() || parameters->options().icf())
{
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
#define Unordered_set std::tr1::unordered_set
#define Unordered_map std::tr1::unordered_map
+#define Unordered_multimap std::tr1::unordered_multimap
#define reserve_unordered_map(map, n) ((map)->rehash(n))
#define Unordered_set __gnu_cxx::hash_set
#define Unordered_map __gnu_cxx::hash_map
+#define Unordered_multimap __gnu_cxx::hash_multimap
namespace __gnu_cxx
{
#define Unordered_set std::set
#define Unordered_map std::map
+#define Unordered_map std::multimap
#define reserve_unordered_map(map, n)
--- /dev/null
+// icf.cc -- Identical Code Folding.
+//
+// Copyright 2009 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.
+
+// Identical Code Folding Algorithm
+// ----------------------------------
+// Detecting identical functions is done here and the basic algorithm
+// is as follows. A checksum is computed on each .text section using
+// its contents and relocations. If the symbol name corresponding to
+// a relocation is known it is used to compute the checksum. If the
+// symbol name is not known the stringified name of the object and the
+// section number pointed to by the relocation is used. The checksums
+// are stored as keys in a hash map and a section is identical to some
+// other section if its checksum is already present in the hash map.
+// Checksum collisions are handled by using a multimap and explicitly
+// checking the contents when two sections have the same checksum.
+//
+// However, two functions A and B with identical text but with
+// relocations pointing to different .text sections can be identical if
+// the corresponding .text sections to which their relocations point to
+// turn out to be identical. Hence, this checksumming process must be
+// done repeatedly until convergence is obtained. Here is an example for
+// the following case :
+//
+// int funcA () int funcB ()
+// { {
+// return foo(); return goo();
+// } }
+//
+// The functions funcA and funcB are identical if functions foo() and
+// goo() are identical.
+//
+// Hence, as described above, we repeatedly do the checksumming,
+// assigning identical functions to the same group, until convergence is
+// obtained. Now, we have two different ways to do this depending on how
+// we initialize.
+//
+// Algorithm I :
+// -----------
+// We can start with marking all functions as different and repeatedly do
+// the checksumming. This has the advantage that we do not need to wait
+// for convergence. We can stop at any point and correctness will be
+// guaranteed although not all cases would have been found. However, this
+// has a problem that some cases can never be found even if it is run until
+// convergence. Here is an example with mutually recursive functions :
+//
+// int funcA (int a) int funcB (int a)
+// { {
+// if (a == 1) if (a == 1)
+// return 1; return 1;
+// return 1 + funcB(a - 1); return 1 + funcA(a - 1);
+// } }
+//
+// In this example funcA and funcB are identical and one of them could be
+// folded into the other. However, if we start with assuming that funcA
+// and funcB are not identical, the algorithm, even after it is run to
+// convergence, cannot detect that they are identical. It should be noted
+// that even if the functions were self-recursive, Algorithm I cannot catch
+// that they are identical, at least as is.
+//
+// Algorithm II :
+// ------------
+// Here we start with marking all functions as identical and then repeat
+// the checksumming until convergence. This can detect the above case
+// mentioned above. It can detect all cases that Algorithm I can and more.
+// However, the caveat is that it has to be run to convergence. It cannot
+// be stopped arbitrarily like Algorithm I as correctness cannot be
+// guaranteed. Algorithm II is not implemented.
+//
+// Algorithm I is used because experiments show that about three
+// iterations are more than enough to achieve convergence. Algorithm I can
+// handle recursive calls if it is changed to use a special common symbol
+// for recursive relocs. This seems to be the most common case that
+// Algorithm I could not catch as is. Mutually recursive calls are not
+// frequent and Algorithm I wins because of its ability to be stopped
+// arbitrarily.
+//
+// Caveat with using function pointers :
+// ------------------------------------
+//
+// Programs using function pointer comparisons/checks should use function
+// folding with caution as the result of such comparisons could be different
+// when folding takes place. This could lead to unexpected run-time
+// behaviour.
+//
+//
+// How to run : --icf
+// Optional parameters : --icf-iterations <num> --print-icf-sections
+//
+// Performance : Less than 20 % link-time overhead on industry strength
+// applications. Up to 6 % text size reductions.
+
+#include "gold.h"
+#include "object.h"
+#include "gc.h"
+#include "icf.h"
+#include "symtab.h"
+#include "libiberty.h"
+
+namespace gold
+{
+
+// This function determines if a section or a group of identical
+// sections has unique contents. Such unique sections or groups can be
+// declared final and need not be processed any further.
+// Parameters :
+// ID_SECTION : Vector mapping a section index to a Section_id pair.
+// IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
+// sections is already known to be unique.
+// SECTION_CONTENTS : Contains the section's text and relocs to sections
+// that cannot be folded. SECTION_CONTENTS are NULL
+// implies that this function is being called for the
+// first time before the first iteration of icf.
+
+static void
+preprocess_for_unique_sections(const std::vector<Section_id>& id_section,
+ std::vector<bool>* is_secn_or_group_unique,
+ std::vector<std::string>* section_contents)
+{
+ Unordered_map<uint32_t, unsigned int> uniq_map;
+ std::pair<Unordered_map<uint32_t, unsigned int>::iterator, bool>
+ uniq_map_insert;
+
+ for (unsigned int i = 0; i < id_section.size(); i++)
+ {
+ if ((*is_secn_or_group_unique)[i])
+ continue;
+
+ uint32_t cksum;
+ Section_id secn = id_section[i];
+ section_size_type plen;
+ if (section_contents == NULL)
+ {
+ const unsigned char* contents;
+ contents = secn.first->section_contents(secn.second,
+ &plen,
+ false);
+ cksum = xcrc32(contents, plen, 0xffffffff);
+ }
+ else
+ {
+ const unsigned char* contents_array = reinterpret_cast
+ <const unsigned char*>((*section_contents)[i].c_str());
+ cksum = xcrc32(contents_array, (*section_contents)[i].length(),
+ 0xffffffff);
+ }
+ uniq_map_insert = uniq_map.insert(std::make_pair(cksum, i));
+ if (uniq_map_insert.second)
+ {
+ (*is_secn_or_group_unique)[i] = true;
+ }
+ else
+ {
+ (*is_secn_or_group_unique)[i] = false;
+ (*is_secn_or_group_unique)[uniq_map_insert.first->second] = false;
+ }
+ }
+}
+
+// This returns the buffer containing the section's contents, both
+// text and relocs. Relocs are differentiated as those pointing to
+// sections that could be folded and those that cannot. Only relocs
+// pointing to sections that could be folded are recomputed on
+// subsequent invocations of this function.
+// Parameters :
+// FIRST_ITERATION : true if it is the first invocation.
+// SECN : Section for which contents are desired.
+// SECTION_NUM : Unique section number of this section.
+// NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
+// to ICF sections.
+// KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
+// SECTION_CONTENTS : Store the section's text and relocs to non-ICF
+// sections.
+
+static std::string
+get_section_contents(bool first_iteration,
+ const Section_id& secn,
+ unsigned int section_num,
+ unsigned int* num_tracked_relocs,
+ Symbol_table* symtab,
+ const std::vector<unsigned int>& kept_section_id,
+ std::vector<std::string>* section_contents)
+{
+ section_size_type plen;
+ const unsigned char* contents = NULL;
+
+ if (first_iteration)
+ {
+ contents = secn.first->section_contents(secn.second,
+ &plen,
+ false);
+ }
+
+ // The buffer to hold all the contents including relocs. A checksum
+ // is then computed on this buffer.
+ std::string buffer;
+ std::string icf_reloc_buffer;
+
+ if (num_tracked_relocs)
+ *num_tracked_relocs = 0;
+
+ Icf::Section_list& seclist = symtab->icf()->section_reloc_list();
+ Icf::Symbol_list& symlist = symtab->icf()->symbol_reloc_list();
+ Icf::Addend_list& addendlist = symtab->icf()->addend_reloc_list();
+
+ Icf::Section_list::iterator it_seclist = seclist.find(secn);
+ Icf::Symbol_list::iterator it_symlist = symlist.find(secn);
+ Icf::Addend_list::iterator it_addendlist = addendlist.find(secn);
+
+ buffer.clear();
+ icf_reloc_buffer.clear();
+
+ // Process relocs and put them into the buffer.
+
+ if (it_seclist != seclist.end())
+ {
+ gold_assert(it_symlist != symlist.end());
+ gold_assert(it_addendlist != addendlist.end());
+ Icf::Sections_reachable_list v = it_seclist->second;
+ Icf::Symbol_info s = it_symlist->second;
+ Icf::Addend_info a = it_addendlist->second;
+ Icf::Sections_reachable_list::iterator it_v = v.begin();
+ Icf::Symbol_info::iterator it_s = s.begin();
+ Icf::Addend_info::iterator it_a = a.begin();
+
+ for (; it_v != v.end(); ++it_v, ++it_s, ++it_a)
+ {
+ // ADDEND_STR stores the symbol value and addend, each
+ // atmost 16 hex digits long. it_v points to a pair
+ // where first is the symbol value and second is the
+ // addend.
+ char addend_str[34];
+ snprintf(addend_str, sizeof(addend_str), "%llx %llx",
+ (*it_a).first, (*it_a).second);
+ Section_id reloc_secn(it_v->first, it_v->second);
+
+ // If this reloc turns back and points to the same section,
+ // like a recursive call, use a special symbol to mark this.
+ if (reloc_secn.first == secn.first
+ && reloc_secn.second == secn.second)
+ {
+ if (first_iteration)
+ {
+ buffer.append("R");
+ buffer.append(addend_str);
+ buffer.append("@");
+ }
+ continue;
+ }
+ Icf::Uniq_secn_id_map& section_id_map =
+ symtab->icf()->section_to_int_map();
+ Icf::Uniq_secn_id_map::iterator section_id_map_it =
+ section_id_map.find(reloc_secn);
+ if (section_id_map_it != section_id_map.end())
+ {
+ // This is a reloc to a section that might be folded.
+ if (num_tracked_relocs)
+ (*num_tracked_relocs)++;
+
+ char kept_section_str[10];
+ unsigned int secn_id = section_id_map_it->second;
+ snprintf(kept_section_str, sizeof(kept_section_str), "%u",
+ kept_section_id[secn_id]);
+ if (first_iteration)
+ {
+ buffer.append("ICF_R");
+ buffer.append(addend_str);
+ }
+ icf_reloc_buffer.append(kept_section_str);
+ // Append the addend.
+ icf_reloc_buffer.append(addend_str);
+ icf_reloc_buffer.append("@");
+ }
+ else
+ {
+ // This is a reloc to a section that cannot be folded.
+ // Process it only in the first iteration.
+ if (!first_iteration)
+ continue;
+
+ uint64_t secn_flags = (it_v->first)->section_flags(it_v->second);
+ // This reloc points to a merge section. Hash the
+ // contents of this section.
+ if ((secn_flags & elfcpp::SHF_MERGE) != 0)
+ {
+ uint64_t entsize =
+ (it_v->first)->section_entsize(it_v->second);
+ long long offset = it_a->first + it_a->second;
+ section_size_type secn_len;
+ const unsigned char* str_contents =
+ (it_v->first)->section_contents(it_v->second,
+ &secn_len,
+ false) + offset;
+ if ((secn_flags & elfcpp::SHF_STRINGS) != 0)
+ {
+ // String merge section.
+ const char* str_char =
+ reinterpret_cast<const char*>(str_contents);
+ switch(entsize)
+ {
+ case 1:
+ {
+ buffer.append(str_char);
+ break;
+ }
+ case 2:
+ {
+ const uint16_t* ptr_16 =
+ reinterpret_cast<const uint16_t*>(str_char);
+ unsigned int strlen_16 = 0;
+ // Find the NULL character.
+ while(*(ptr_16 + strlen_16) != 0)
+ strlen_16++;
+ buffer.append(str_char, strlen_16 * 2);
+ }
+ break;
+ case 4:
+ {
+ const uint32_t* ptr_32 =
+ reinterpret_cast<const uint32_t*>(str_char);
+ unsigned int strlen_32 = 0;
+ // Find the NULL character.
+ while(*(ptr_32 + strlen_32) != 0)
+ strlen_32++;
+ buffer.append(str_char, strlen_32 * 4);
+ }
+ break;
+ default:
+ gold_unreachable();
+ }
+ }
+ else
+ {
+ // Use the entsize to determine the length.
+ buffer.append(reinterpret_cast<const
+ char*>(str_contents),
+ entsize);
+ }
+ }
+ else if ((*it_s) != NULL)
+ {
+ // If symbol name is available use that.
+ const char *sym_name = (*it_s)->name();
+ buffer.append(sym_name);
+ // Append the addend.
+ buffer.append(addend_str);
+ buffer.append("@");
+ }
+ else
+ {
+ // Symbol name is not available, like for a local symbol,
+ // use object and section id.
+ buffer.append(it_v->first->name());
+ char secn_id[10];
+ snprintf(secn_id, sizeof(secn_id), "%u",it_v->second);
+ buffer.append(secn_id);
+ // Append the addend.
+ buffer.append(addend_str);
+ buffer.append("@");
+ }
+ }
+ }
+ }
+
+ if (first_iteration)
+ {
+ buffer.append("Contents = ");
+ buffer.append(reinterpret_cast<const char*>(contents), plen);
+ // Store the section contents that dont change to avoid recomputing
+ // during the next call to this function.
+ (*section_contents)[section_num] = buffer;
+ }
+ else
+ {
+ gold_assert(buffer.empty());
+ // Reuse the contents computed in the previous iteration.
+ buffer.append((*section_contents)[section_num]);
+ }
+
+ buffer.append(icf_reloc_buffer);
+ return buffer;
+}
+
+// This function computes a checksum on each section to detect and form
+// groups of identical sections. The first iteration does this for all
+// sections.
+// Further iterations do this only for the kept sections from each group to
+// determine if larger groups of identical sections could be formed. The
+// first section in each group is the kept section for that group.
+//
+// CRC32 is the checksumming algorithm and can have collisions. That is,
+// two sections with different contents can have the same checksum. Hence,
+// a multimap is used to maintain more than one group of checksum
+// identical sections. A section is added to a group only after its
+// contents are explicitly compared with the kept section of the group.
+//
+// Parameters :
+// ITERATION_NUM : Invocation instance of this function.
+// NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
+// to ICF sections.
+// KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
+// ID_SECTION : Vector mapping a section to an unique integer.
+// IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
+// sectionsis already known to be unique.
+// SECTION_CONTENTS : Store the section's text and relocs to non-ICF
+// sections.
+
+static bool
+match_sections(unsigned int iteration_num,
+ Symbol_table* symtab,
+ std::vector<unsigned int>* num_tracked_relocs,
+ std::vector<unsigned int>* kept_section_id,
+ const std::vector<Section_id>& id_section,
+ std::vector<bool>* is_secn_or_group_unique,
+ std::vector<std::string>* section_contents)
+{
+ Unordered_multimap<uint32_t, unsigned int> section_cksum;
+ std::pair<Unordered_multimap<uint32_t, unsigned int>::iterator,
+ Unordered_multimap<uint32_t, unsigned int>::iterator> key_range;
+ bool converged = true;
+
+ if (iteration_num == 1)
+ preprocess_for_unique_sections(id_section,
+ is_secn_or_group_unique,
+ NULL);
+ else
+ preprocess_for_unique_sections(id_section,
+ is_secn_or_group_unique,
+ section_contents);
+
+ std::vector<std::string> full_section_contents;
+
+ for (unsigned int i = 0; i < id_section.size(); i++)
+ {
+ full_section_contents.push_back("");
+ if ((*is_secn_or_group_unique)[i])
+ continue;
+
+ Section_id secn = id_section[i];
+ std::string this_secn_contents;
+ uint32_t cksum;
+ if (iteration_num == 1)
+ {
+ unsigned int num_relocs = 0;
+ this_secn_contents = get_section_contents(true, secn, i, &num_relocs,
+ symtab, (*kept_section_id),
+ section_contents);
+ (*num_tracked_relocs)[i] = num_relocs;
+ }
+ else
+ {
+ if ((*kept_section_id)[i] != i)
+ {
+ // This section is already folded into something. See
+ // if it should point to a different kept section.
+ unsigned int kept_section = (*kept_section_id)[i];
+ if (kept_section != (*kept_section_id)[kept_section])
+ {
+ (*kept_section_id)[i] = (*kept_section_id)[kept_section];
+ }
+ continue;
+ }
+ this_secn_contents = get_section_contents(false, secn, i, NULL,
+ symtab, (*kept_section_id),
+ section_contents);
+ }
+
+ const unsigned char* this_secn_contents_array =
+ reinterpret_cast<const unsigned char*>(this_secn_contents.c_str());
+ cksum = xcrc32(this_secn_contents_array, this_secn_contents.length(),
+ 0xffffffff);
+ size_t count = section_cksum.count(cksum);
+
+ if (count == 0)
+ {
+ // Start a group with this cksum.
+ section_cksum.insert(std::make_pair(cksum, i));
+ full_section_contents[i] = this_secn_contents;
+ }
+ else
+ {
+ key_range = section_cksum.equal_range(cksum);
+ Unordered_multimap<uint32_t, unsigned int>::iterator it;
+ // Search all the groups with this cksum for a match.
+ for (it = key_range.first; it != key_range.second; ++it)
+ {
+ unsigned int kept_section = it->second;
+ if (full_section_contents[kept_section].length()
+ != this_secn_contents.length())
+ continue;
+ if (memcmp(full_section_contents[kept_section].c_str(),
+ this_secn_contents.c_str(),
+ this_secn_contents.length()) != 0)
+ continue;
+ (*kept_section_id)[i] = kept_section;
+ converged = false;
+ break;
+ }
+ if (it == key_range.second)
+ {
+ // Create a new group for this cksum.
+ section_cksum.insert(std::make_pair(cksum, i));
+ full_section_contents[i] = this_secn_contents;
+ }
+ }
+ // If there are no relocs to foldable sections do not process
+ // this section any further.
+ if (iteration_num == 1 && (*num_tracked_relocs)[i] == 0)
+ (*is_secn_or_group_unique)[i] = true;
+ }
+
+ return converged;
+}
+
+
+// This is the main ICF function called in gold.cc. This does the
+// initialization and calls match_sections repeatedly (twice by default)
+// which computes the crc checksums and detects identical functions.
+
+void
+Icf::find_identical_sections(const Input_objects* input_objects,
+ Symbol_table* symtab)
+{
+ unsigned int section_num = 0;
+ std::vector<unsigned int> num_tracked_relocs;
+ std::vector<bool> is_secn_or_group_unique;
+ std::vector<std::string> section_contents;
+
+ // Decide which sections are possible candidates first.
+
+ for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
+ p != input_objects->relobj_end();
+ ++p)
+ {
+ for (unsigned int i = 0;i < (*p)->shnum(); ++i)
+ {
+ // Only looking to fold functions, so just look at .text sections.
+ if (!is_prefix_of(".text.", (*p)->section_name(i).c_str()))
+ continue;
+ if (!(*p)->is_section_included(i))
+ continue;
+ if (parameters->options().gc_sections()
+ && symtab->gc()->is_section_garbage(*p, i))
+ continue;
+ this->id_section_.push_back(Section_id(*p, i));
+ this->section_id_[Section_id(*p, i)] = section_num;
+ this->kept_section_id_.push_back(section_num);
+ num_tracked_relocs.push_back(0);
+ is_secn_or_group_unique.push_back(false);
+ section_contents.push_back("");
+ section_num++;
+ }
+ }
+
+ unsigned int num_iterations = 0;
+
+ // Default number of iterations to run ICF is 2.
+ unsigned int max_iterations = (parameters->options().icf_iterations() > 0)
+ ? parameters->options().icf_iterations()
+ : 2;
+
+ bool converged = false;
+
+ while (!converged && (num_iterations < max_iterations))
+ {
+ num_iterations++;
+ converged = match_sections(num_iterations, symtab,
+ &num_tracked_relocs, &this->kept_section_id_,
+ this->id_section_, &is_secn_or_group_unique,
+ §ion_contents);
+ }
+
+ if (parameters->options().print_icf_sections())
+ {
+ if (converged)
+ gold_info(_("%s: ICF Converged after %u iteration(s)"),
+ program_name, num_iterations);
+ else
+ gold_info(_("%s: ICF stopped after %u iteration(s)"),
+ program_name, num_iterations);
+ }
+
+ this->icf_ready();
+}
+
+// This function determines if the section corresponding to the
+// given object and index is folded based on if the kept section
+// is different from this section.
+
+bool
+Icf::is_section_folded(Object* obj, unsigned int shndx)
+{
+ Section_id secn(obj, shndx);
+ Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
+ if (it == this->section_id_.end())
+ return false;
+ unsigned int section_num = it->second;
+ unsigned int kept_section_id = this->kept_section_id_[section_num];
+ return kept_section_id != section_num;
+}
+
+// This function returns the folded section for the given section.
+
+Section_id
+Icf::get_folded_section(Object* dup_obj, unsigned int dup_shndx)
+{
+ Section_id dup_secn(dup_obj, dup_shndx);
+ Uniq_secn_id_map::iterator it = this->section_id_.find(dup_secn);
+ gold_assert(it != this->section_id_.end());
+ unsigned int section_num = it->second;
+ unsigned int kept_section_id = this->kept_section_id_[section_num];
+ Section_id folded_section = this->id_section_[kept_section_id];
+ return folded_section;
+}
+
+} // End of namespace gold.
--- /dev/null
+// icf.h -- Identical Code Folding
+
+// Copyright 2009 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"
+
+namespace gold
+{
+
+class Object;
+class Input_objects;
+class Symbol_table;
+
+typedef std::pair<Object*, unsigned int> Section_id;
+
+class Icf
+{
+ public:
+ struct Section_id_hash
+ {
+ size_t operator()(const Section_id& loc) const
+ { return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; }
+ };
+
+ typedef std::vector<Section_id> Sections_reachable_list;
+ typedef std::vector<Symbol*> Symbol_info;
+ typedef std::vector<std::pair<long long, long long> > Addend_info;
+ typedef Unordered_map<Section_id,
+ Sections_reachable_list,
+ Section_id_hash> Section_list;
+ typedef Unordered_map<Section_id, Symbol_info, Section_id_hash> Symbol_list;
+ typedef Unordered_map<Section_id, Addend_info, Section_id_hash> Addend_list;
+ typedef Unordered_map<Section_id,
+ unsigned int,
+ Section_id_hash> Uniq_secn_id_map;
+
+ Icf()
+ : id_section_(), section_id_(), kept_section_id_(),
+ num_tracked_relocs(NULL), icf_ready_(false),
+ section_reloc_list_(), symbol_reloc_list_(),
+ addend_reloc_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_; }
+
+ // Returns the kept section corresponding to the
+ // given section.
+ bool
+ is_section_folded(Object* obj, unsigned int shndx);
+
+ // Returns a map of a section to a list of all sections referenced
+ // by its relocations.
+ Section_list&
+ section_reloc_list()
+ { return this->section_reloc_list_; }
+
+ // Returns a map of a section to a list of all symbols referenced
+ // by its relocations.
+ Symbol_list&
+ symbol_reloc_list()
+ { return this->symbol_reloc_list_; }
+
+ // Returns a maps of a section to a list of symbol values and addends
+ // of its relocations.
+ Addend_list&
+ addend_reloc_list()
+ { return this->addend_reloc_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_;
+ unsigned int* num_tracked_relocs;
+ // Flag to indicate if ICF has been run.
+ bool icf_ready_;
+
+ // These lists are populated by gc_process_relocs in gc.h.
+ Section_list section_reloc_list_;
+ Symbol_list symbol_reloc_list_;
+ Addend_list addend_reloc_list_;
+};
+
+} // End of namespace gold.
+
+#endif
++p)
{
unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
- off);
+ off, symtab);
off += (index - local_symbol_index) * symsize;
local_symbol_index = index;
}
#include "layout.h"
#include "plugin.h"
#include "gc.h"
+#include "icf.h"
#include "incremental.h"
using namespace gold;
// The list of input objects.
Input_objects input_objects;
- // The Garbage Collection Object.
+ // The Garbage Collection (GC, --gc-sections) Object.
Garbage_collection gc;
+ // The Identical Code Folding (ICF, --icf) Object.
+ Icf icf;
+
// The symbol table. We're going to guess here how many symbols
// we're going to see based on the number of input files. Even when
// this is off, it means at worst we don't quite optimize hashtable
if (parameters->options().gc_sections())
symtab.set_gc(&gc);
+ if (parameters->options().icf())
+ symtab.set_icf(&icf);
+
// The layout object.
Layout layout(command_line.number_of_input_files(),
&command_line.script_options());
// whether they should be included in the link. If they should, we
// pass them to the Layout object, which will return an output section
// and an offset.
-// During garbage collection (gc-sections), this function is called
-// twice. When it is called the first time, it is for setting up some
-// sections as roots to a work-list and to do comdat processing. Actual
-// layout happens the second time around after all the relevant sections
-// have been determined. The first time, is_worklist_ready is false.
-// It is then set to true after the worklist is processed and the relevant
-// sections are determined. Then, this function is called again to
-// layout the sections.
+// During garbage collection (--gc-sections) and identical code folding
+// (--icf), this function is called twice. When it is called the first
+// time, it is for setting up some sections as roots to a work-list for
+// --gc-sections and to do comdat processing. Actual layout happens the
+// second time around after all the relevant sections have been determined.
+// The first time, is_worklist_ready or is_icf_ready is false. It is then
+// set to true after the garbage collection worklist or identical code
+// folding is processed and the relevant sections to be kept are
+// determined. Then, this function is called again to layout the sections.
template<int size, bool big_endian>
void
Read_symbols_data* sd)
{
const unsigned int shnum = this->shnum();
- bool is_gc_pass_one = (parameters->options().gc_sections()
- && !symtab->gc()->is_worklist_ready());
- bool is_gc_pass_two = (parameters->options().gc_sections()
- && symtab->gc()->is_worklist_ready());
+ bool is_gc_pass_one = ((parameters->options().gc_sections()
+ && !symtab->gc()->is_worklist_ready())
+ || (parameters->options().icf()
+ && !symtab->icf()->is_icf_ready()));
+
+ bool is_gc_pass_two = ((parameters->options().gc_sections()
+ && symtab->gc()->is_worklist_ready())
+ || (parameters->options().icf()
+ && symtab->icf()->is_icf_ready()));
+
+ bool is_gc_or_icf = (parameters->options().gc_sections()
+ || parameters->options().icf());
+
+ // Both is_gc_pass_one and is_gc_pass_two should not be true.
+ gold_assert(!(is_gc_pass_one && is_gc_pass_two));
+
if (shnum == 0)
return;
Symbols_data* gc_sd = NULL;
const unsigned char* symbol_names_data = NULL;
section_size_type symbol_names_size;
- if (parameters->options().gc_sections())
+ if (is_gc_or_icf)
{
section_headers_data = gc_sd->section_headers_data;
section_names_size = gc_sd->section_names_size;
const unsigned char* pshdrs;
// Get the section names.
- const unsigned char* pnamesu = parameters->options().gc_sections() ?
- gc_sd->section_names_data :
- sd->section_names->data();
+ const unsigned char* pnamesu = (is_gc_or_icf)
+ ? gc_sd->section_names_data
+ : sd->section_names->data();
+
const char* pnames = reinterpret_cast<const char*>(pnamesu);
// If any input files have been claimed by plugins, we need to defer
}
}
- if (is_gc_pass_one)
+ if (is_gc_pass_one && parameters->options().gc_sections())
{
if (is_section_name_included(name)
|| shdr.get_sh_type() == elfcpp::SHT_INIT_ARRAY
continue;
}
- if (is_gc_pass_two)
+ if (is_gc_pass_two && parameters->options().gc_sections())
{
// This is executed during the second pass of garbage
// collection. do_layout has been called before and some
gold_assert(out_section_offsets[i] == invalid_address);
continue;
}
- if ((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0)
- if (symtab->gc()->referenced_list().find(Section_id(this,i))
- == symtab->gc()->referenced_list().end())
+ if (((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0)
+ && symtab->gc()->is_section_garbage(this, i))
{
if (parameters->options().print_gc_sections())
gold_info(_("%s: removing unused section from '%s'"
- " in file '%s"),
+ " in file '%s'"),
program_name, this->section_name(i).c_str(),
this->name().c_str());
out_sections[i] = NULL;
continue;
}
}
+
+ if (is_gc_pass_two && parameters->options().icf())
+ {
+ if (out_sections[i] == NULL)
+ {
+ gold_assert(out_section_offsets[i] == invalid_address);
+ continue;
+ }
+ if (((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0)
+ && symtab->icf()->is_section_folded(this, i))
+ {
+ if (parameters->options().print_icf_sections())
+ {
+ Section_id folded =
+ symtab->icf()->get_folded_section(this, i);
+ Relobj* folded_obj =
+ reinterpret_cast<Relobj*>(folded.first);
+ gold_info(_("%s: ICF folding section '%s' in file '%s'"
+ "into '%s' in file '%s'"),
+ program_name, this->section_name(i).c_str(),
+ this->name().c_str(),
+ folded_obj->section_name(folded.second).c_str(),
+ folded_obj->name().c_str());
+ }
+ out_sections[i] = NULL;
+ out_section_offsets[i] = invalid_address;
+ continue;
+ }
+ }
+
// Defer layout here if input files are claimed by plugins. When gc
// is turned on this function is called twice. For the second call
// should_defer_layout should be false.
out_sections[i] = reinterpret_cast<Output_section*>(2);
out_section_offsets[i] = invalid_address;
continue;
- }
+ }
+
// During gc_pass_two if a section that was previously deferred is
// found, do not layout the section as layout_deferred_sections will
// do it later from gold.cc.
layout->layout_gnu_stack(seen_gnu_stack, gnu_stack_flags);
// When doing a relocatable link handle the reloc sections at the
- // end. Garbage collection is not turned on for relocatable code.
+ // end. Garbage collection and Identical Code Folding is not
+ // turned on for relocatable code.
if (emit_relocs)
this->size_relocatable_relocs();
- gold_assert(!parameters->options().gc_sections() || reloc_sections.empty());
+
+ gold_assert(!(is_gc_or_icf) || reloc_sections.empty());
+
for (std::vector<unsigned int>::const_iterator p = reloc_sections.begin();
p != reloc_sections.end();
++p)
delete[] gc_sd->section_names_data;
delete[] gc_sd->symbols_data;
delete[] gc_sd->symbol_names_data;
+ this->set_symbols_data(NULL);
}
else
{
template<int size, bool big_endian>
unsigned int
Sized_relobj<size, big_endian>::do_finalize_local_symbols(unsigned int index,
- off_t off)
+ off_t off,
+ Symbol_table* symtab)
{
gold_assert(off == static_cast<off_t>(align_address(off, size >> 3)));
}
Output_section* os = out_sections[shndx];
+ Address secoffset = out_offsets[shndx];
+ if (symtab->is_section_folded(this, shndx))
+ {
+ gold_assert (os == NULL && secoffset == invalid_address);
+ // Get the os of the section it is folded onto.
+ Section_id folded = symtab->icf()->get_folded_section(this,
+ shndx);
+ gold_assert(folded.first != NULL);
+ Sized_relobj<size, big_endian>* folded_obj = reinterpret_cast
+ <Sized_relobj<size, big_endian>*>(folded.first);
+ os = folded_obj->output_section(folded.second);
+ gold_assert(os != NULL);
+ secoffset = folded_obj->get_output_section_offset(folded.second);
+ gold_assert(secoffset != invalid_address);
+ }
if (os == NULL)
{
// so we leave the input value unchanged here.
continue;
}
- else if (out_offsets[shndx] == invalid_address)
+ else if (secoffset == invalid_address)
{
uint64_t start;
}
else if (lv.is_tls_symbol())
lv.set_output_value(os->tls_offset()
- + out_offsets[shndx]
+ + secoffset
+ lv.input_value());
else
lv.set_output_value((relocatable ? 0 : os->address())
- + out_offsets[shndx]
+ + secoffset
+ lv.input_value());
}
return this->output_local_dynsym_count_;
}
+// If Symbols_data is not NULL get the section flags from here otherwise
+// get it from the file.
+
+template<int size, bool big_endian>
+uint64_t
+Sized_relobj<size, big_endian>::do_section_flags(unsigned int shndx)
+{
+ Symbols_data* sd = this->get_symbols_data();
+ if (sd != NULL)
+ {
+ const unsigned char* pshdrs = sd->section_headers_data
+ + This::shdr_size * shndx;
+ typename This::Shdr shdr(pshdrs);
+ return shdr.get_sh_flags();
+ }
+ // If sd is NULL, read the section header from the file.
+ return this->elf_file_.section_flags(shndx);
+}
+
+// Get the section's ent size from Symbols_data. Called by get_section_contents
+// in icf.cc
+
+template<int size, bool big_endian>
+uint64_t
+Sized_relobj<size, big_endian>::do_section_entsize(unsigned int shndx)
+{
+ Symbols_data* sd = this->get_symbols_data();
+ gold_assert (sd != NULL);
+
+ const unsigned char* pshdrs = sd->section_headers_data
+ + This::shdr_size * shndx;
+ typename This::Shdr shdr(pshdrs);
+ return shdr.get_sh_entsize();
+}
+
+
// Write out the local symbols.
template<int size, bool big_endian>
section_flags(unsigned int shndx)
{ return this->do_section_flags(shndx); }
+ // Return the section entsize given a section index.
+ uint64_t
+ section_entsize(unsigned int shndx)
+ { return this->do_section_entsize(shndx); }
+
// Return the section address given a section index.
uint64_t
section_address(unsigned int shndx)
virtual uint64_t
do_section_flags(unsigned int shndx) = 0;
+ // Get section entsize--implemented by child class.
+ virtual uint64_t
+ do_section_entsize(unsigned int shndx) = 0;
+
// Get section address--implemented by child class.
virtual uint64_t
do_section_address(unsigned int shndx) = 0;
output_sections_(),
map_to_relocatable_relocs_(NULL),
object_merge_map_(NULL),
- relocs_must_follow_section_writes_(false)
+ relocs_must_follow_section_writes_(false),
+ sd_(NULL)
{ }
// During garbage collection, the Read_symbols_data pass for
// indexes for the local variables, and set the offset where local
// symbol information will be stored. Returns the new local symbol index.
unsigned int
- finalize_local_symbols(unsigned int index, off_t off)
- { return this->do_finalize_local_symbols(index, off); }
+ finalize_local_symbols(unsigned int index, off_t off, Symbol_table* symtab)
+ { return this->do_finalize_local_symbols(index, off, symtab); }
// Set the output dynamic symbol table indexes for the local variables.
unsigned int
// for the local variables, and set the offset where local symbol
// information will be stored.
virtual unsigned int
- do_finalize_local_symbols(unsigned int, off_t) = 0;
+ do_finalize_local_symbols(unsigned int, off_t, Symbol_table*) = 0;
// Set the output dynamic symbol table indexes for the local variables.
virtual unsigned int
// Finalize the local symbols.
unsigned int
- do_finalize_local_symbols(unsigned int, off_t);
+ do_finalize_local_symbols(unsigned int, off_t, Symbol_table*);
// Set the offset where local dynamic symbol information will be stored.
unsigned int
// Return section flags.
uint64_t
- do_section_flags(unsigned int shndx)
- { return this->elf_file_.section_flags(shndx); }
+ do_section_flags(unsigned int shndx);
+
+ // Return section entsize.
+ uint64_t
+ do_section_entsize(unsigned int shndx);
// Return section address.
uint64_t
DEFINE_special(static, options::ONE_DASH, '\0',
N_("Do not link against shared libraries"), NULL);
+ DEFINE_bool(icf, options::TWO_DASHES, '\0', false,
+ N_("Fold identical functions"),
+ N_("Don't fold identical functions (default)"));
+
+ DEFINE_uint(icf_iterations, options::TWO_DASHES , '\0', 0,
+ N_("Number of iterations of ICF (default 2)"), N_("COUNT"));
+
+ DEFINE_bool(print_icf_sections, options::TWO_DASHES, '\0', false,
+ N_("List folded identical sections on stderr"),
+ N_("Do not list folded identical sections"));
+
DEFINE_bool(gc_sections, options::TWO_DASHES, '\0', false,
N_("Remove unused sections"),
N_("Don't remove unused sections (default)"));
return 0;
}
+// Return section entsize. Not used for plugin objects.
+
+template<int size, bool big_endian>
+uint64_t
+Sized_pluginobj<size, big_endian>::do_section_entsize(unsigned int)
+{
+ gold_unreachable();
+ return 0;
+}
+
// Return section address. Not used for plugin objects.
template<int size, bool big_endian>
uint64_t
do_section_flags(unsigned int shndx);
+ // Return section entsize.
+ uint64_t
+ do_section_entsize(unsigned int shndx);
+
// Return section address.
uint64_t
do_section_address(unsigned int shndx);
this->object_->set_relocs_data(rd);
this->object_->release();
- // If garbage collection is desired, we must process the relocs
- // instead of scanning the relocs as reloc processing is necessary
- // to determine unused sections.
- if (parameters->options().gc_sections())
- {
- workqueue->queue_next(new Gc_process_relocs(this->options_,
+ // If garbage collection or identical comdat folding is desired, we
+ // process the relocs first before scanning them. Scanning of relocs is
+ // done only after garbage or identical sections is identified.
+ if (parameters->options().gc_sections() || parameters->options().icf())
+ {
+ workqueue->queue_next(new Gc_process_relocs(this->options_,
this->symtab_,
this->layout_,
this->object_, rd,
// When garbage collection is on, unreferenced sections are not included
// in the link that would have been included normally. This is known only
// after Read_relocs hence this check has to be done again.
- if (parameters->options().gc_sections())
+ if (parameters->options().gc_sections() || parameters->options().icf())
{
if (p->output_section == NULL)
continue;
: saw_undefined_(0), offset_(0), table_(count), namepool_(),
forwarders_(), commons_(), tls_commons_(), small_commons_(),
large_commons_(), forced_locals_(), warnings_(),
- version_script_(version_script), gc_(NULL)
+ version_script_(version_script), gc_(NULL), icf_(NULL)
{
namepool_.reserve(count);
}
return k1.first == k2.first && k1.second == k2.second;
}
+bool
+Symbol_table::is_section_folded(Object* obj, unsigned int shndx) const
+{
+ return (parameters->options().icf()
+ && this->icf_->is_section_folded(obj, shndx));
+}
+
// For symbols that have been listed with -u option, add them to the
// work list to avoid gc'ing them.
{
Relobj* relobj = static_cast<Relobj*>(symobj);
Output_section* os = relobj->output_section(shndx);
+ uint64_t secoff64 = relobj->output_section_offset(shndx);
- if (os == NULL)
+ if (this->is_section_folded(relobj, shndx))
+ {
+ gold_assert(os == NULL);
+ // Get the os of the section it is folded onto.
+ Section_id folded = this->icf_->get_folded_section(relobj,
+ shndx);
+ gold_assert(folded.first != NULL);
+ Relobj* folded_obj = reinterpret_cast<Relobj*>(folded.first);
+ os = folded_obj->output_section(folded.second);
+ gold_assert(os != NULL);
+ secoff64 = folded_obj->output_section_offset(folded.second);
+ }
+
+ if (os == NULL)
{
sym->set_symtab_index(-1U);
bool static_or_reloc = (parameters->doing_static_link() ||
return false;
}
- uint64_t secoff64 = relobj->output_section_offset(shndx);
if (secoff64 == -1ULL)
{
// The section needs special handling (e.g., a merge section).
+
value = os->output_address(relobj, shndx, sym->value());
}
else
{
Relobj* relobj = static_cast<Relobj*>(symobj);
Output_section* os = relobj->output_section(in_shndx);
+ if (this->is_section_folded(relobj, in_shndx))
+ {
+ // This global symbol must be written out even though
+ // it is folded.
+ // Get the os of the section it is folded onto.
+ Section_id folded =
+ this->icf_->get_folded_section(relobj, in_shndx);
+ gold_assert(folded.first !=NULL);
+ Relobj* folded_obj =
+ reinterpret_cast<Relobj*>(folded.first);
+ os = folded_obj->output_section(folded.second);
+ gold_assert(os != NULL);
+ }
gold_assert(os != NULL);
shndx = os->out_shndx();
#include <vector>
#include "gc.h"
+#include "icf.h"
#include "elfcpp.h"
#include "parameters.h"
#include "stringpool.h"
class Output_file;
class Output_symtab_xindex;
class Garbage_collection;
+class Icf;
// The base class of an entry in the symbol table. The symbol table
// can have a lot of entries, so we don't want this class to big.
~Symbol_table();
void
+ set_icf(Icf* icf)
+ { this->icf_ = icf;}
+
+ Icf*
+ icf() const
+ { return this->icf_; }
+
+ // Returns true if ICF determined that this is a duplicate section.
+ bool
+ is_section_folded(Object* obj, unsigned int shndx) const;
+
+ void
set_gc(Garbage_collection* gc)
{ this->gc_ = gc; }
Garbage_collection*
- gc()
+ gc() const
{ return this->gc_; }
// During garbage collection, this keeps undefined symbols.
// Information parsed from the version script, if any.
const Version_script_info& version_script_;
Garbage_collection* gc_;
+ Icf* icf_;
};
// We inline get_sized_symbol for efficiency.
// If the local symbol belongs to a section we are discarding,
// and that section is a debug section, try to find the
// corresponding kept section and map this symbol to its
- // counterpart in the kept section.
+ // counterpart in the kept section. The symbol must not
+ // correspond to a section we are folding.
bool is_ordinary;
unsigned int shndx = psymval->input_shndx(&is_ordinary);
if (is_ordinary
&& shndx != elfcpp::SHN_UNDEF
- && !object->is_section_included(shndx))
+ && !object->is_section_included(shndx)
+ && !(relinfo->symtab->is_section_folded(object, shndx)))
{
if (comdat_behavior == CB_UNDETERMINED)
{
gc_comdat_test.stdout: gc_comdat_test
$(TEST_NM) -C gc_comdat_test > gc_comdat_test.stdout
+check_SCRIPTS += icf_test.sh
+check_DATA += icf_test.stdout
+icf_test.o: icf_test.cc
+ $(CXXCOMPILE) -O0 -c -ffunction-sections -g -o $@ $<
+icf_test: icf_test.o gcctestdir/ld
+ $(CXXLINK) -Bgcctestdir/ -Wl,--icf icf_test.o
+icf_test.stdout: icf_test
+ $(TEST_NM) -C icf_test > icf_test.stdout
+
check_PROGRAMS += basic_test
check_PROGRAMS += basic_static_test
# Test --dynamic-list, --dynamic-list-data, --dynamic-list-cpp-new,
# and --dynamic-list-cpp-typeinfo
@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_1 = gc_comdat_test.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@ two_file_shared.sh weak_plt.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@ debug_msg.sh undef_symbol.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_1.sh ver_test_2.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_4.sh ver_test_5.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_7.sh ver_test_10.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_test.sh two_file_shared.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ weak_plt.sh debug_msg.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ undef_symbol.sh ver_test_1.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_2.sh ver_test_4.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_5.sh ver_test_7.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_test_10.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ ver_matching_test.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ script_test_3.sh \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ script_test_4.sh \
# We also want to make sure we do something reasonable when there's no
# debug info available. For the best test, we use .so's.
@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_2 = gc_comdat_test.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_test.stdout \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ two_file_shared.dbg \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ weak_plt_shared.so debug_msg.err \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ debug_msg_so.err \
@NATIVE_LINKER_FALSE@ $(am__DEPENDENCIES_1) \
@NATIVE_LINKER_FALSE@ $(am__DEPENDENCIES_1)
subdir = testsuite
-DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
+DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in ChangeLog
ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
am__aclocal_m4_deps = $(top_srcdir)/../config/depstand.m4 \
$(top_srcdir)/../config/gettext-sister.m4 \
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXLINK) -Bgcctestdir/ -Wl,--gc-sections gc_comdat_test_1.o gc_comdat_test_2.o
@GCC_TRUE@@NATIVE_LINKER_TRUE@gc_comdat_test.stdout: gc_comdat_test
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_NM) -C gc_comdat_test > gc_comdat_test.stdout
+@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_test.o: icf_test.cc
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -ffunction-sections -g -o $@ $<
+@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_test: icf_test.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXLINK) -Bgcctestdir/ -Wl,--icf icf_test.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_test.stdout: icf_test
+@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_NM) -C icf_test > icf_test.stdout
@GCC_TRUE@@NATIVE_LINKER_TRUE@basic_test.o: basic_test.cc
@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -o $@ $<
@GCC_TRUE@@NATIVE_LINKER_TRUE@basic_test: basic_test.o gcctestdir/ld
--- /dev/null
+// icf_test.cc -- a test case for gold
+
+// Copyright 2009 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.
+
+// The goal of this program is to verify if identical code folding
+// correctly identifies and folds functions. folded_func must be
+// folded into kept_func.
+
+int common()
+{
+ return 1;
+}
+
+int kept_func()
+{
+ common();
+ // Recursive call.
+ kept_func();
+ return 1;
+}
+
+int folded_func()
+{
+ common();
+ // Recursive call.
+ folded_func();
+ return 1;
+}
+
+int main()
+{
+ return 0;
+}
--- /dev/null
+#!/bin/sh
+
+# icf_test.sh -- test --icf
+
+# Copyright 2009 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.
+
+# The goal of this program is to verify if icf works as expected.
+# File icf_test.cc is in this test. This program checks if the
+# identical sections are correctly folded.
+
+check()
+{
+ func_addr_1=`grep $2 $1 | awk '{print $1}'`
+ func_addr_2=`grep $3 $1 | awk '{print $1}'`
+ if [ $func_addr_1 != $func_addr_2 ]
+ then
+ echo "Identical Code Folding failed to fold" $2 "and" $3
+ exit 1
+ fi
+}
+
+check icf_test.stdout "folded_func" "kept_func"
projects / external / binutils.git / commitdiff