From 6f8ec5c8c5565b56dca38d9e7d2393ea0d963db2 Mon Sep 17 00:00:00 2001 From: Douglas Gregor Date: Fri, 13 Mar 2009 05:23:53 +0000 Subject: [PATCH] Implement an optimization that David Abrahams and myself came up with, 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] --- include/boost/function/function_base.hpp | 18 +++++-- include/boost/function/function_template.hpp | 53 +++++++++++++++----- 2 files changed, 55 insertions(+), 16 deletions(-) diff --git a/include/boost/function/function_base.hpp b/include/boost/function/function_base.hpp index 35afa16..2cc6bf6 100644 --- a/include/boost/function/function_base.hpp +++ b/include/boost/function/function_base.hpp @@ -18,6 +18,9 @@ #include #include #include +#include +#include +#include #include #include #include @@ -625,7 +628,7 @@ public: if (!vtable) return typeid(void); detail::function::function_buffer type; - vtable->manager(functor, type, detail::function::get_functor_type_tag); + get_vtable()->manager(functor, type, detail::function::get_functor_type_tag); return *type.type.type; } @@ -638,7 +641,7 @@ public: type_result.type.type = &typeid(Functor); type_result.type.const_qualified = is_const::value; type_result.type.volatile_qualified = is_volatile::value; - vtable->manager(functor, type_result, + get_vtable()->manager(functor, type_result, detail::function::check_functor_type_tag); return static_cast(type_result.obj_ptr); } @@ -656,7 +659,7 @@ public: type_result.type.type = &typeid(Functor); type_result.type.const_qualified = true; type_result.type.volatile_qualified = is_volatile::value; - vtable->manager(functor, type_result, + get_vtable()->manager(functor, type_result, detail::function::check_functor_type_tag); // GCC 2.95.3 gets the CV qualifiers wrong here, so we // can't do the static_cast that we should do. @@ -702,6 +705,15 @@ public: #endif public: // should be protected, but GCC 2.95.3 will fail to allow access + detail::function::vtable_base* get_vtable() const { + return reinterpret_cast( + reinterpret_cast(vtable) & ~(std::size_t)0x01); + } + + bool has_trivial_copy_and_destroy() const { + return reinterpret_cast(vtable) & 0x01; + } + detail::function::vtable_base* vtable; mutable detail::function::function_buffer functor; }; diff --git a/include/boost/function/function_template.hpp b/include/boost/function/function_template.hpp index 584abe9..23687b4 100644 --- a/include/boost/function/function_template.hpp +++ b/include/boost/function/function_template.hpp @@ -678,6 +678,11 @@ namespace boost { R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS> vtable_type; + vtable_type* get_vtable() const { + return reinterpret_cast( + reinterpret_cast(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)->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)->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(&stored_vtable.base); + if (boost::has_trivial_copy_constructor::value && + boost::has_trivial_destructor::value && + detail::function::function_allows_small_object_optimization::value) + value |= (std::size_t)0x01; + vtable = reinterpret_cast(value); + } else + vtable = 0; } template @@ -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(&stored_vtable.base); + if (boost::has_trivial_copy_constructor::value && + boost::has_trivial_destructor::value && + detail::function::function_allows_small_object_optimization::value) + value |= (std::size_t)0x01; + vtable = reinterpret_cast(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 BOOST_FUNCTION_FUNCTION< R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>::result_type - BOOST_FUNCTION_FUNCTION + inline + BOOST_FUNCTION_FUNCTION ::operator()(BOOST_FUNCTION_PARMS) const { if (this->empty()) boost::throw_exception(bad_function_call()); - return reinterpret_cast(vtable)->invoker + return get_vtable()->invoker (this->functor BOOST_FUNCTION_COMMA BOOST_FUNCTION_ARGS); } #endif