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* layout.cc (Layout::find_or_add_kept_section): New function.

Browse source 
(Layout::add_comdat): Removed.
	* layout.h (struct Kept_section): Move out of class Layout.
	Remove trailing underscores from field names.  Add group_sections
	field.  Rename group_ field to is_group.  Change all uses.
	(class Layout): Declare find_or_add_kept_section, not add_comdat.
	* object.cc (Sized_relobj::Sized_relobj): Don't initialize
	comdat_groups_ field.
	(Sized_relobj::include_section_group): Use
	find_or_add_kept_section and Kept_section::group_sections.
	(Sized_relobj::include_linkonce_section): Likewise.
	* object.cc (class Sized_relobj): Don't define Comdat_group or
	Comdat_group_table.  Remove find_comdat_group and
	add_comdat_group.  Remove comdat_groups_ field.
	* plugin.cc (include_comdat_group): Use
	Layout::find_or_add_kept_section.
This commit is contained in:
Ian Lance Taylor 2009-03-01 22:22:02 +00:00
parent d1bbb13a63
commit 8a4c0b0d7e
6 changed files with 126 additions and 101 deletions
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19
gold/ChangeLog
View file

@ -1,3 +1,22 @@
2009-03-01 Mikolaj Zalewski <mikolajz@google.com>
* layout.cc (Layout::find_or_add_kept_section): New function.
(Layout::add_comdat): Removed.
* layout.h (struct Kept_section): Move out of class Layout.
Remove trailing underscores from field names. Add group_sections
field. Rename group_ field to is_group. Change all uses.
(class Layout): Declare find_or_add_kept_section, not add_comdat.
* object.cc (Sized_relobj::Sized_relobj): Don't initialize
comdat_groups_ field.
(Sized_relobj::include_section_group): Use
find_or_add_kept_section and Kept_section::group_sections.
(Sized_relobj::include_linkonce_section): Likewise.
* object.cc (class Sized_relobj): Don't define Comdat_group or
Comdat_group_table. Remove find_comdat_group and
add_comdat_group. Remove comdat_groups_ field.
* plugin.cc (include_comdat_group): Use
Layout::find_or_add_kept_section.
2009-02-28 Ian Lance Taylor <iant@google.com>
* README: --gc-sections and map files are now supported. Document

41
gold/layout.cc
View file

@ -2930,46 +2930,50 @@ Layout::output_section_name(const char* name, size_t* plen)
return name;
}
// Record the signature of a comdat section, and return whether to
// include it in the link. If GROUP is true, this is a regular
// section group. If GROUP is false, this is a group signature
// derived from the name of a linkonce section. We want linkonce
// signatures and group signatures to block each other, but we don't
// want a linkonce signature to block another linkonce signature.
// Check if a comdat group or .gnu.linkonce section with the given
// NAME is selected for the link. If there is already a section,
// *KEPT_SECTION is set to point to the signature and the function
// returns false. Otherwise, the CANDIDATE signature is recorded for
// this NAME in the layout object, *KEPT_SECTION is set to the
// internal copy and the function return false. In some cases, with
// CANDIDATE->GROUP_ being false, KEPT_SECTION can point back to
// CANDIDATE.
bool
Layout::add_comdat(Relobj* object, unsigned int shndx,
const std::string& signature, bool group)
Layout::find_or_add_kept_section(const std::string name,
Kept_section* candidate,
Kept_section** kept_section)
{
Kept_section kept(object, shndx, group);
std::pair<Signatures::iterator, bool> ins(
this->signatures_.insert(std::make_pair(signature, kept)));
this->signatures_.insert(std::make_pair(name, *candidate)));
if (kept_section)
*kept_section = &ins.first->second;
if (ins.second)
{
// This is the first time we've seen this signature.
return true;
}
if (ins.first->second.group_)
if (ins.first->second.is_group)
{
// We've already seen a real section group with this signature.
// If the kept group is from a plugin object, and we're in
// the replacement phase, accept the new one as a replacement.
if (ins.first->second.object_ == NULL
if (ins.first->second.object == NULL
&& parameters->options().plugins()->in_replacement_phase())
{
ins.first->second = kept;
ins.first->second = *candidate;
return true;
}
return false;
}
else if (group)
else if (candidate->is_group)
{
// This is a real section group, and we've already seen a
// linkonce section with this signature. Record that we've seen
// a section group, and don't include this section group.
ins.first->second.group_ = true;
ins.first->second.is_group = true;
return false;
}
else
@ -2977,6 +2981,7 @@ Layout::add_comdat(Relobj* object, unsigned int shndx,
// We've already seen a linkonce section and this is a linkonce
// section. These don't block each other--this may be the same
// symbol name with different section types.
*kept_section = candidate;
return true;
}
}
@ -2991,8 +2996,8 @@ Layout::find_kept_object(const std::string& signature,
if (p == this->signatures_.end())
return NULL;
if (pshndx != NULL)
*pshndx = p->second.shndx_;
return p->second.object_;
*pshndx = p->second.shndx;
return p->second.object;
}
// Store the allocated sections into the section list.
@ -3101,7 +3106,7 @@ Layout::write_sections_after_input_sections(Output_file* of)
{
off_t off = this->output_file_size_;
off = this->set_section_offsets(off, POSTPROCESSING_SECTIONS_PASS);
// Now that we've finalized the names, we can finalize the shstrab.
off =
this->set_section_offsets(off,

65
gold/layout.h
View file

@ -1,6 +1,6 @@
// layout.h -- lay out output file sections for gold -*- C++ -*-
// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
@ -89,6 +89,37 @@ class Layout_task_runner : public Task_function_runner
Mapfile* mapfile_;
};
// This struct holds information about the comdat or .gnu.linkonce
// that will be kept.
struct Kept_section
{
Kept_section()
: object(NULL), shndx(0), is_group(false), group_sections(NULL)
{ }
Kept_section(Relobj* a_object, unsigned int a_shndx, bool a_is_group)
: object(a_object), shndx(a_shndx), is_group(a_is_group),
group_sections(NULL)
{ }
typedef Unordered_map<std::string, unsigned int> Comdat_group;
// The object containing the comdat or .gnu.linkonce.
Relobj* object;
// Index to the group section for comdats and the section itself for
// .gnu.linkonce.
unsigned int shndx;
// The Kept_sections are values of a mapping, that maps names to
// them. This field is true if this struct is associated with the
// name of a comdat or .gnu.linkonce, false if it is associated with
// the name of a symbol obtained from the .gnu.linkonce.* name
// through some heuristics.
bool is_group;
// For comdats, a map from names of the sections in the group to
// indexes in OBJECT_. NULL for .gnu.linkonce.
Comdat_group* group_sections;
};
// This class handles the details of laying out input sections.
class Layout
@ -225,18 +256,24 @@ class Layout
{
// Debugging sections can only be recognized by name.
return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0
|| strncmp(name, ".gnu.linkonce.wi.",
|| strncmp(name, ".gnu.linkonce.wi.",
sizeof(".gnu.linkonce.wi.") - 1) == 0
|| strncmp(name, ".line", sizeof(".line") - 1) == 0
|| strncmp(name, ".stab", sizeof(".stab") - 1) == 0);
}
// Record the signature of a comdat section, and return whether to
// include it in the link. The GROUP parameter is true for a
// section group signature, false for a signature derived from a
// .gnu.linkonce section.
// Check if a comdat group or .gnu.linkonce section with the given
// NAME is selected for the link. If there is already a section,
// *KEPT_SECTION is set to point to the signature and the function
// returns false. Otherwise, the CANDIDATE signature is recorded
// for this NAME in the layout object, *KEPT_SECTION is set to the
// internal copy and the function return false. In some cases, with
// CANDIDATE->GROUP_ being false, KEPT_SECTION can point back to
// CANDIDATE.
bool
add_comdat(Relobj*, unsigned int, const std::string&, bool group);
find_or_add_kept_section(const std::string name,
Kept_section* candidate,
Kept_section** kept_section);
// Find the given comdat signature, and return the object and section
// index of the kept group.
@ -577,19 +614,7 @@ class Layout
static bool
segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
// A mapping used for group signatures.
struct Kept_section
{
Kept_section()
: object_(NULL), shndx_(0), group_(false)
{ }
Kept_section(Relobj* object, unsigned int shndx, bool group)
: object_(object), shndx_(shndx), group_(group)
{ }
Relobj* object_;
unsigned int shndx_;
bool group_;
};
// A mapping used for kept comdats/.gnu.linkonce group signatures.
typedef Unordered_map<std::string, Kept_section> Signatures;
// Mapping from input section name/type/flags to output section. We

67
gold/object.cc
View file

@ -327,7 +327,6 @@ Sized_relobj<size, big_endian>::Sized_relobj(
local_values_(),
local_got_offsets_(),
kept_comdat_sections_(),
comdat_groups_(),
has_eh_frame_(false)
{
}
@ -674,29 +673,25 @@ Sized_relobj<size, big_endian>::include_section_group(
// Record this section group in the layout, and see whether we've already
// seen one with the same signature.
bool include_group = ((flags & elfcpp::GRP_COMDAT) == 0
|| layout->add_comdat(this, index, signature, true));
bool include_group;
Sized_relobj<size, big_endian>* kept_object = NULL;
Comdat_group* kept_group = NULL;
Kept_section::Comdat_group* kept_group = NULL;
if (!include_group)
if ((flags & elfcpp::GRP_COMDAT) == 0)
include_group = true;
else
{
// This group is being discarded. Find the object and group
// that was kept in its place.
unsigned int kept_group_index = 0;
Relobj* kept_relobj = layout->find_kept_object(signature,
&kept_group_index);
kept_object = static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
if (kept_object != NULL)
kept_group = kept_object->find_comdat_group(kept_group_index);
}
else if (flags & elfcpp::GRP_COMDAT)
{
// This group is being kept. Create the table to map section names
// to section indexes and add it to the table of groups.
kept_group = new Comdat_group();
this->add_comdat_group(index, kept_group);
Kept_section this_group(this, index, true);
Kept_section *kept_section_group;
include_group = layout->find_or_add_kept_section(signature,
&this_group,
&kept_section_group);
if (include_group)
kept_section_group->group_sections = new Kept_section::Comdat_group;
kept_group = kept_section_group->group_sections;
kept_object = (static_cast<Sized_relobj<size, big_endian>*>
(kept_section_group->object));
}
size_t count = shdr.get_sh_size() / sizeof(elfcpp::Elf_Word);
@ -745,7 +740,8 @@ Sized_relobj<size, big_endian>::include_section_group(
{
// Find the corresponding kept section, and store that info
// in the discarded section table.
Comdat_group::const_iterator p = kept_group->find(mname);
Kept_section::Comdat_group::const_iterator p =
kept_group->find(mname);
if (p != kept_group->end())
{
Kept_comdat_section* kept =
@ -808,8 +804,12 @@ Sized_relobj<size, big_endian>::include_linkonce_section(
symname = strrchr(name, '.') + 1;
std::string sig1(symname);
std::string sig2(name);
bool include1 = layout->add_comdat(this, index, sig1, false);
bool include2 = layout->add_comdat(this, index, sig2, true);
Kept_section candidate1(this, index, false);
Kept_section candidate2(this, index, true);
Kept_section* kept1;
Kept_section* kept2;
bool include1 = layout->find_or_add_kept_section(sig1, &candidate1, &kept1);
bool include2 = layout->find_or_add_kept_section(sig2, &candidate2, &kept2);
if (!include2)
{
@ -817,12 +817,12 @@ Sized_relobj<size, big_endian>::include_linkonce_section(
// name (i.e., the kept section was also a linkonce section).
// In this case, the section index stored with the layout object
// is the linkonce section that was kept.
unsigned int kept_group_index = 0;
Relobj* kept_relobj = layout->find_kept_object(sig2, &kept_group_index);
unsigned int kept_group_index = kept2->shndx;
Relobj* kept_relobj = kept2->object;
if (kept_relobj != NULL)
{
Sized_relobj<size, big_endian>* kept_object
= static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
Sized_relobj<size, big_endian>* kept_object =
static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
Kept_comdat_section* kept =
new Kept_comdat_section(kept_object, kept_group_index);
this->set_kept_comdat_section(index, kept);
@ -837,17 +837,16 @@ Sized_relobj<size, big_endian>::include_linkonce_section(
// this linkonce section. We'll handle the simple case where
// the group has only one member section. Otherwise, it's not
// worth the effort.
unsigned int kept_group_index = 0;
Relobj* kept_relobj = layout->find_kept_object(sig1, &kept_group_index);
Relobj* kept_relobj = kept1->object;
if (kept_relobj != NULL)
{
Sized_relobj<size, big_endian>* kept_object =
static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
Comdat_group* kept_group =
kept_object->find_comdat_group(kept_group_index);
static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
Kept_section::Comdat_group* kept_group = kept1->group_sections;
if (kept_group != NULL && kept_group->size() == 1)
{
Comdat_group::const_iterator p = kept_group->begin();
Kept_section::Comdat_group::const_iterator p =
kept_group->begin();
gold_assert(p != kept_group->end());
Kept_comdat_section* kept =
new Kept_comdat_section(kept_object, p->second);

28
gold/object.h
View file

@ -1584,32 +1584,6 @@ class Sized_relobj : public Relobj
typedef std::map<unsigned int, Kept_comdat_section*>
Kept_comdat_section_table;
// Information needed to keep track of kept comdat groups. This is
// simply a map from the section name to its section index. This may
// not be a one-to-one mapping, but we ignore that possibility since
// this is used only to attempt to handle stray relocations from
// non-comdat debug sections that refer to comdat loadable sections.
typedef Unordered_map<std::string, unsigned int> Comdat_group;
// A map from group section index to the table of group members.
typedef std::map<unsigned int, Comdat_group*> Comdat_group_table;
// Find a comdat group table given its group section SHNDX.
Comdat_group*
find_comdat_group(unsigned int shndx) const
{
Comdat_group_table::const_iterator p =
this->comdat_groups_.find(shndx);
if (p != this->comdat_groups_.end())
return p->second;
return NULL;
}
// Record a new comdat group whose group section index is SHNDX.
void
add_comdat_group(unsigned int shndx, Comdat_group* group)
{ this->comdat_groups_[shndx] = group; }
// Adjust a section index if necessary.
unsigned int
adjust_shndx(unsigned int shndx)
@ -1823,8 +1797,6 @@ class Sized_relobj : public Relobj
std::vector<Address> section_offsets_;
// Table mapping discarded comdat sections to corresponding kept sections.
Kept_comdat_section_table kept_comdat_sections_;
// Table of kept comdat groups.
Comdat_group_table comdat_groups_;
// Whether this object has a GNU style .eh_frame section.
bool has_eh_frame_;
// The list of sections whose layout was deferred.

7
gold/plugin.cc
View file

@ -506,7 +506,12 @@ Pluginobj::include_comdat_group(std::string comdat_key, Layout* layout)
// If this is the first time we've seen this comdat key, ask the
// layout object whether it should be included.
if (ins.second)
ins.first->second = layout->add_comdat(NULL, 1, comdat_key, true);
{
Kept_section to_add(NULL, 1, true);
ins.first->second = layout->find_or_add_kept_section(comdat_key,
&to_add,
NULL);
}
return ins.first->second;
}