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Rework merge_map for speed.

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This commit is contained in:
Ian Lance Taylor 2007-11-27 06:13:33 +00:00
parent 4f0916aa94
commit 4625f782a5
3 changed files with 263 additions and 90 deletions
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299
gold/merge.cc
View File

@ -30,31 +30,239 @@
namespace gold
{
// Class Merge_map::Merge_key_less.
// For each object with merge sections, we store an Object_merge_map.
// This is used to map locations in input sections to a merged output
// section. The output section itself is not recorded here--it can be
// found in the map_to_output_ field of the Object.
// Sort the entries in a merge mapping. The key is an input object, a
// section index in that object, and an offset in that section.
inline bool
Merge_map::Merge_key_less::operator()(const Merge_key& mk1,
const Merge_key& mk2) const
class Object_merge_map
{
// The order of different objects and different sections doesn't
// matter. We want to get consistent results across links so we
// don't use pointer comparison.
if (mk1.object != mk2.object)
public:
Object_merge_map()
: first_shnum_(-1U), first_map_(),
second_shnum_(-1U), second_map_(),
section_merge_maps_()
{ }
~Object_merge_map();
// Add a mapping for MERGE_MAP, for the bytes from OFFSET to OFFSET
// + LENGTH in the input section SHNDX to OUTPUT_OFFSET in the
// output section. An OUTPUT_OFFSET of -1 means that the bytes are
// discarded.
void
add_mapping(const Merge_map*, unsigned int shndx, off_t offset, off_t length,
off_t output_offset);
// Get the output offset for an input address in MERGE_MAP. The
// input address is at offset OFFSET in section SHNDX. This sets
// *OUTPUT_OFFSET to the offset in the output section; this will be
// -1 if the bytes are not being copied to the output. This returns
// true if the mapping is known, false otherwise.
bool
get_output_offset(const Merge_map*, unsigned int shndx, off_t offset,
off_t *output_offset);
private:
// Map input section offsets to a length and an output section
// offset. An output section offset of -1 means that this part of
// the input section is being discarded.
struct Input_merge_entry
{
// The offset in the input section.
off_t input_offset;
// The length.
off_t length;
// The offset in the output section.
off_t output_offset;
};
// A less-than comparison routine for Input_merge_entry.
struct Input_merge_compare
{
bool
operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const
{ return i1.input_offset < i2.input_offset; }
};
// A list of entries for a particular section.
struct Input_merge_map
{
// The Merge_map for this section.
const Merge_map* merge_map;
// The list of mappings.
std::vector<Input_merge_entry> entries;
// Whether the ENTRIES field is sorted by input_offset.
bool sorted;
Input_merge_map()
: merge_map(NULL), entries(), sorted(true)
{ }
};
// Map input section indices to merge maps.
typedef std::map<unsigned int, Input_merge_map*> Section_merge_maps;
// Return a pointer to the Input_merge_map to use for the input
// section SHNDX, or NULL.
Input_merge_map*
get_input_merge_map(unsigned int shndx);
// Get or make the the Input_merge_map to use for the section SHNDX
// with MERGE_MAP.
Input_merge_map*
get_or_make_input_merge_map(const Merge_map* merge_map, unsigned int shndx);
// Any given object file will normally only have a couple of input
// sections with mergeable contents. So we keep the first two input
// section numbers inline, and push any further ones into a map. A
// value of -1U in first_shnum_ or second_shnum_ means that we don't
// have a corresponding entry.
unsigned int first_shnum_;
Input_merge_map first_map_;
unsigned int second_shnum_;
Input_merge_map second_map_;
Section_merge_maps section_merge_maps_;
};
// Destructor.
Object_merge_map::~Object_merge_map()
{
for (Section_merge_maps::iterator p = this->section_merge_maps_.begin();
p != this->section_merge_maps_.end();
++p)
delete p->second;
}
// Get the Input_merge_map to use for an input section, or NULL.
Object_merge_map::Input_merge_map*
Object_merge_map::get_input_merge_map(unsigned int shndx)
{
gold_assert(shndx != -1U);
if (shndx == this->first_shnum_)
return &this->first_map_;
if (shndx == this->second_shnum_)
return &this->second_map_;
Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx);
if (p != this->section_merge_maps_.end())
return p->second;
return NULL;
}
// Get or create the Input_merge_map to use for an input section.
Object_merge_map::Input_merge_map*
Object_merge_map::get_or_make_input_merge_map(const Merge_map* merge_map,
unsigned int shndx)
{
Input_merge_map* map = this->get_input_merge_map(shndx);
if (map != NULL)
{
// Two different object files can have the same name: if foo.a
// includes both bar/qux.o and baz/qux.o, then both end up with
// the name foo.a(qux.o). But it's impossible for two different
// object files to have both the same name and the same offset.
if (mk1.object->offset() != mk2.object->offset())
return mk1.object->offset() < mk2.object->offset();
return mk1.object->name() < mk2.object->name();
// For a given input section in a given object, every mapping
// must be donw with the same Merge_map.
gold_assert(map->merge_map == merge_map);
return map;
}
if (mk1.shndx != mk2.shndx)
return mk1.shndx < mk2.shndx;
return mk1.offset < mk2.offset;
// We need to create a new entry.
if (this->first_shnum_ == -1U)
{
this->first_shnum_ = shndx;
this->first_map_.merge_map = merge_map;
return &this->first_map_;
}
if (this->second_shnum_ == -1U)
{
this->second_shnum_ = shndx;
this->second_map_.merge_map = merge_map;
return &this->second_map_;
}
Input_merge_map* new_map = new Input_merge_map;
new_map->merge_map = merge_map;
this->section_merge_maps_[shndx] = new_map;
return new_map;
}
// Add a mapping.
void
Object_merge_map::add_mapping(const Merge_map* merge_map, unsigned int shndx,
off_t input_offset, off_t length,
off_t output_offset)
{
Input_merge_map* map = this->get_or_make_input_merge_map(merge_map, shndx);
// Try to merge the new entry in the last one we saw.
if (!map->entries.empty())
{
Input_merge_entry& entry(map->entries.back());
// If this entry is not in order, we need to sort the vector
// before looking anything up.
if (input_offset < entry.input_offset + entry.length)
{
gold_assert(input_offset < entry.input_offset
&& input_offset + length <= entry.input_offset);
map->sorted = false;
}
else if (entry.input_offset + entry.length == input_offset
&& (output_offset == -1
? entry.output_offset == -1
: entry.output_offset + entry.length == output_offset))
{
entry.length += length;
return;
}
}
Input_merge_entry entry;
entry.input_offset = input_offset;
entry.length = length;
entry.output_offset = output_offset;
map->entries.push_back(entry);
}
// Get the output offset for an input address.
bool
Object_merge_map::get_output_offset(const Merge_map* merge_map,
unsigned int shndx, off_t input_offset,
off_t *output_offset)
{
Input_merge_map* map = this->get_input_merge_map(shndx);
if (map == NULL || map->merge_map != merge_map)
return false;
if (!map->sorted)
{
std::sort(map->entries.begin(), map->entries.end(),
Input_merge_compare());
map->sorted = true;
}
Input_merge_entry entry;
entry.input_offset = input_offset;
std::vector<Input_merge_entry>::const_iterator p =
std::lower_bound(map->entries.begin(), map->entries.end(),
entry, Input_merge_compare());
if (p == map->entries.end() || p->input_offset > input_offset)
{
if (p == map->entries.begin())
return false;
--p;
gold_assert(p->input_offset <= input_offset);
}
if (input_offset - p->input_offset >= p->length)
return false;
*output_offset = p->output_offset;
if (*output_offset != -1)
*output_offset += (input_offset - p->input_offset);
return true;
}
// Class Merge_map.
@ -67,18 +275,14 @@ void
Merge_map::add_mapping(Relobj* object, unsigned int shndx,
off_t offset, off_t length, off_t output_offset)
{
Merge_key mk;
mk.object = object;
mk.shndx = shndx;
mk.offset = offset;
Object_merge_map* object_merge_map = object->merge_map();
if (object_merge_map == NULL)
{
object_merge_map = new Object_merge_map();
object->set_merge_map(object_merge_map);
}
Merge_value mv;
mv.length = length;
mv.output_offset = output_offset;
std::pair<Merge_mapping::iterator, bool> ins =
this->merge_map_.insert(std::make_pair(mk, mv));
gold_assert(ins.second);
object_merge_map->add_mapping(this, shndx, offset, length, output_offset);
}
// Return the output offset for an input address. The input address
@ -90,34 +294,11 @@ bool
Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,
off_t offset, off_t* output_offset) const
{
Merge_key mk;
mk.object = object;
mk.shndx = shndx;
mk.offset = offset;
Merge_mapping::const_iterator p = this->merge_map_.lower_bound(mk);
// If MK is not in the map, lower_bound returns the next iterator
// larger than it.
if (p == this->merge_map_.end()
|| p->first.object != object
|| p->first.shndx != shndx
|| p->first.offset != offset)
{
if (p == this->merge_map_.begin())
return false;
--p;
}
if (p->first.object != object || p->first.shndx != shndx)
Object_merge_map* object_merge_map = object->merge_map();
if (object_merge_map == NULL)
return false;
if (offset - p->first.offset >= p->second.length)
return false;
*output_offset = p->second.output_offset;
if (*output_offset != -1)
*output_offset += (offset - p->first.offset);
return true;
return object_merge_map->get_output_offset(this, shndx, offset,
output_offset);
}
// Class Output_merge_base.

32
gold/merge.h
View File

@ -32,13 +32,13 @@ namespace gold
{
// This class manages mappings from input sections to offsets in an
// output section. This is used where input sections are merged.
// output section. This is used where input sections are merged. The
// actual data is stored in fields in Object.
class Merge_map
{
public:
Merge_map()
: merge_map_()
{ }
// Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in the
@ -57,34 +57,6 @@ class Merge_map
bool
get_output_offset(const Relobj* object, unsigned int shndx, off_t offset,
off_t *output_offset) const;
private:
// We build a mapping from OBJECT/SHNDX/OFFSET to an offset and
// length in the output section.
struct Merge_key
{
const Relobj* object;
unsigned int shndx;
off_t offset;
};
struct Merge_key_less
{
inline bool
operator()(const Merge_key&, const Merge_key&) const;
};
struct Merge_value
{
off_t length;
off_t output_offset;
};
typedef std::map<Merge_key, Merge_value, Merge_key_less> Merge_mapping;
// A mapping from input object/section/offset to offset in output
// section.
Merge_mapping merge_map_;
};
// A general class for SHF_MERGE data, to hold functions shared by

22
gold/object.h
View File

@ -39,6 +39,7 @@ class Layout;
class Output_section;
class Output_file;
class Dynobj;
class Object_merge_map;
template<typename Stringpool_char>
class Stringpool_template;
@ -411,7 +412,10 @@ class Relobj : public Object
{
public:
Relobj(const std::string& name, Input_file* input_file, off_t offset = 0)
: Object(name, input_file, false, offset)
: Object(name, input_file, false, offset),
map_to_output_(),
object_merge_map_(NULL),
relocs_must_follow_section_writes_(false)
{ }
// Read the relocs.
@ -481,6 +485,19 @@ class Relobj : public Object
relocs_must_follow_section_writes()
{ return this->relocs_must_follow_section_writes_; }
// Return the object merge map.
Object_merge_map*
merge_map() const
{ return this->object_merge_map_; }
// Set the object merge map.
void
set_merge_map(Object_merge_map* object_merge_map)
{
gold_assert(this->object_merge_map_ == NULL);
this->object_merge_map_ = object_merge_map;
}
protected:
// What we need to know to map an input section to an output
// section. We keep an array of these, one for each input section,
@ -533,6 +550,9 @@ class Relobj : public Object
private:
// Mapping from input sections to output section.
std::vector<Map_to_output> map_to_output_;
// Mappings for merge sections. This is managed by the code in the
// Merge_map class.
Object_merge_map* object_merge_map_;
// Whether we need to wait for output sections to be written before
// we can apply relocations.
bool relocs_must_follow_section_writes_;