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Implement an optimization that David Abrahams and myself came up with,

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where Boost.Function uses a bit in the vtable pointer to indicate when
the target function object has a trivial copy constructor, trivial
destructor, and fits within the small object buffer. In this case, we
just copy the bits of the function object rather than performing an
indirect call to the manager.

This results in a 60% speedup on a micro-benchmark that copies and
calls such function objects repeatedly.



[SVN r51743]
This commit is contained in:
Douglas Gregor
2009-03-13 05:23:53 +00:00
parent 678fb133f0
commit 6f8ec5c8c5
2 changed files with 55 additions and 16 deletions
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53
include/boost/function/function_template.hpp
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@ -678,6 +678,11 @@ namespace boost {
R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
vtable_type;
vtable_type* get_vtable() const {
return reinterpret_cast<vtable_type*>(
reinterpret_cast<std::size_t>(vtable) & ~(std::size_t)0x01);
}
struct clear_type {};
public:
@ -757,7 +762,7 @@ namespace boost {
if (this->empty())
boost::throw_exception(bad_function_call());
return static_cast<vtable_type*>(vtable)->invoker
return get_vtable()->invoker
(this->functor BOOST_FUNCTION_COMMA BOOST_FUNCTION_ARGS);
}
#else
@ -847,7 +852,8 @@ namespace boost {
void clear()
{
if (vtable) {
reinterpret_cast<vtable_type*>(vtable)->clear(this->functor);
if (!this->has_trivial_copy_and_destroy())
get_vtable()->clear(this->functor);
vtable = 0;
}
}
@ -876,8 +882,11 @@ namespace boost {
{
if (!f.empty()) {
this->vtable = f.vtable;
f.vtable->manager(f.functor, this->functor,
boost::detail::function::clone_functor_tag);
if (this->has_trivial_copy_and_destroy())
this->functor = f.functor;
else
get_vtable()->base.manager(f.functor, this->functor,
boost::detail::function::clone_functor_tag);
}
}
@ -903,8 +912,15 @@ namespace boost {
static vtable_type stored_vtable =
{ { &manager_type::manage }, &invoker_type::invoke };
if (stored_vtable.assign_to(f, functor)) vtable = &stored_vtable.base;
else vtable = 0;
if (stored_vtable.assign_to(f, functor)) {
std::size_t value = reinterpret_cast<std::size_t>(&stored_vtable.base);
if (boost::has_trivial_copy_constructor<Functor>::value &&
boost::has_trivial_destructor<Functor>::value &&
detail::function::function_allows_small_object_optimization<Functor>::value)
value |= (std::size_t)0x01;
vtable = reinterpret_cast<detail::function::vtable_base *>(value);
} else
vtable = 0;
}
template<typename Functor,typename Allocator>
@ -930,8 +946,15 @@ namespace boost {
static vtable_type stored_vtable =
{ { &manager_type::manage }, &invoker_type::invoke };
if (stored_vtable.assign_to_a(f, functor, a)) vtable = &stored_vtable.base;
else vtable = 0;
if (stored_vtable.assign_to_a(f, functor, a)) {
std::size_t value = reinterpret_cast<std::size_t>(&stored_vtable.base);
if (boost::has_trivial_copy_constructor<Functor>::value &&
boost::has_trivial_destructor<Functor>::value &&
detail::function::function_allows_small_object_optimization<Functor>::value)
value |= (std::size_t)0x01;
vtable = reinterpret_cast<detail::function::vtable_base *>(value);
} else
vtable = 0;
}
// Moves the value from the specified argument to *this. If the argument
@ -947,9 +970,12 @@ namespace boost {
#endif
if (!f.empty()) {
this->vtable = f.vtable;
f.vtable->manager(f.functor, this->functor,
boost::detail::function::move_functor_tag);
f.vtable = 0;
if (this->has_trivial_copy_and_destroy())
this->functor = f.functor;
else
get_vtable()->base.manager(f.functor, this->functor,
boost::detail::function::move_functor_tag);
f.vtable = 0;
#if !defined(BOOST_NO_EXCEPTIONS)
} else {
clear();
@ -979,13 +1005,14 @@ namespace boost {
template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
typename BOOST_FUNCTION_FUNCTION<
R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>::result_type
BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
inline
BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
::operator()(BOOST_FUNCTION_PARMS) const
{
if (this->empty())
boost::throw_exception(bad_function_call());
return reinterpret_cast<const vtable_type*>(vtable)->invoker
return get_vtable()->invoker
(this->functor BOOST_FUNCTION_COMMA BOOST_FUNCTION_ARGS);
}
#endif