This patch makes assignments correct, because they need to
match indices instead of types. In addition, we cut down the
codegen size. The symbols are longer than before, the the amount
of them is roughly the same, so there's no longer an explosion
in their amount.
Relops are the last bit in these fixes, I'll fix them during the weekend.
2019-03-30 Ville Voutilainen <ville.voutilai...@gmail.com>
Use single-visitation in variant assignment and swap.
Also use indices instead of types when checking whether
variants hold the same thing.
* include/std/variant (__do_visit): Add a template parameter
for index visitation, invoke with indices if index visitation
is used.
(__variant_idx_cookie): New.
(_Copy_assign_base::operator=): Do single-visitation with
an index visitor.
(_Move_assign_base::operator=): Likewise.
(_Extra_visit_slot_needed): Adjust.
(__visit_invoke): Call with indices if it's an index visitor.
(swap): Do single-visitation with an index visitor.
(__visitor_result_type): New.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 7fd6947..3ee1cbd 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -138,7 +138,7 @@ namespace __variant
constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
get(const variant<_Types...>&&);
- template<typename _Visitor, typename... _Variants>
+ template<bool __use_index=false, typename _Visitor, typename... _Variants>
constexpr decltype(auto)
__do_visit(_Visitor&& __visitor, _Variants&&... __variants);
@@ -175,6 +175,10 @@ namespace __variant
// used for raw visitation
struct __variant_cookie {};
+ // used for raw visitation with indices passed in
+ struct __variant_idx_cookie {};
+ // a more explanatory name than 'true'
+ inline constexpr auto __visit_with_index = bool_constant<true>{};
// _Uninitialized<T> is guaranteed to be a literal type, even if T is not.
// We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented
@@ -570,45 +574,44 @@ namespace __variant
operator=(const _Copy_assign_base& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
{
- __do_visit([this, &__rhs](auto&& __this_mem, auto&& __rhs_mem) mutable
- -> __detail::__variant::__variant_cookie
+ __do_visit<__visit_with_index>([this](auto&& __rhs_mem,
+ auto __rhs_index) mutable
+ -> __detail::__variant::__variant_idx_cookie
{
- if constexpr (is_same_v<
- remove_reference_t<decltype(__this_mem)>,
- remove_reference_t<decltype(__rhs_mem)>>)
+ if constexpr (__rhs_index != variant_npos)
{
- if constexpr (!is_same_v<
- remove_reference_t<decltype(__rhs_mem)>,
- __variant_cookie>)
- __this_mem = __rhs_mem;
- }
- else
- {
- if constexpr (!is_same_v<
- remove_reference_t<decltype(__rhs_mem)>,
- __variant_cookie>)
+ if (this->_M_index == __rhs_index)
{
- using __rhs_type =
- remove_reference_t<decltype(__rhs_mem)>;
- if constexpr (is_nothrow_copy_constructible_v<__rhs_type>
- || !is_nothrow_move_constructible_v<__rhs_type>)
+ if constexpr (__rhs_index != variant_npos)
{
- this->_M_destructive_copy(__rhs._M_index, __rhs_mem);
+ auto& __this_mem =
+ __get<__rhs_index>(*this);
+ if constexpr (is_same_v<
+ remove_reference_t<decltype(__this_mem)>,
+ remove_reference_t<decltype(__rhs_mem)>>)
+ __this_mem = __rhs_mem;
}
+ }
+ else
+ {
+ using __rhs_type =
+ remove_reference_t<decltype(__rhs_mem)>;
+ if constexpr
+ (is_nothrow_copy_constructible_v<__rhs_type>
+ || !is_nothrow_move_constructible_v<__rhs_type>)
+ this->_M_destructive_copy(__rhs_index, __rhs_mem);
else
{
auto __tmp(__rhs_mem);
- this->_M_destructive_move(__rhs._M_index,
+ this->_M_destructive_move(__rhs_index,
std::move(__tmp));
}
}
- else
- {
- this->_M_reset();
- }
}
- return {};
- }, __variant_cast<_Types...>(*this), __variant_cast<_Types...>(__rhs));
+ else
+ this->_M_reset();
+ return {};
+ }, __variant_cast<_Types...>(__rhs));
__glibcxx_assert(this->_M_index == __rhs._M_index);
return *this;
}
@@ -641,25 +644,32 @@ namespace __variant
operator=(_Move_assign_base&& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_move_assign)
{
- __do_visit([this, &__rhs](auto&& __this_mem, auto&& __rhs_mem) mutable
- -> __detail::__variant::__variant_cookie
+ __do_visit<__visit_with_index>([this](auto&& __rhs_mem,
+ auto __rhs_index) mutable
+ -> __detail::__variant::__variant_idx_cookie
{
- if constexpr (is_same_v<
- remove_reference_t<decltype(__this_mem)>,
- remove_reference_t<decltype(__rhs_mem)>>)
+ if constexpr (__rhs_index != variant_npos)
{
- if constexpr (!is_same_v<
- remove_reference_t<decltype(__rhs_mem)>,
- __variant_cookie>)
- __this_mem = std::move(__rhs_mem);
+ if (this->_M_index == __rhs_index)
+ {
+ if constexpr (__rhs_index != variant_npos)
+ {
+ auto& __this_mem =
+ __get<__rhs_index>(*this);
+ if constexpr (is_same_v<
+ remove_reference_t<decltype(__this_mem)>,
+ remove_reference_t<decltype(__rhs_mem)>>)
+ __this_mem = std::move(__rhs_mem);
+ }
+ }
+ else
+ this->_M_destructive_move(__rhs_index,
+ std::move(__rhs_mem));
}
else
- {
- auto __tmp(std::move(__rhs_mem));
- this->_M_destructive_move(__rhs._M_index, std::move(__tmp));
- }
- return {};
- }, __variant_cast<_Types...>(*this), __variant_cast<_Types...>(__rhs));
+ this->_M_reset();
+ return {};
+ }, __variant_cast<_Types...>(__rhs));
__glibcxx_assert(this->_M_index == __rhs._M_index);
return *this;
}
@@ -777,7 +787,8 @@ namespace __variant
: bool_constant<__never_valueless<_Types...>()> {};
static constexpr bool value =
- is_same_v<_Maybe_variant_cookie, __variant_cookie>
+ (is_same_v<_Maybe_variant_cookie, __variant_cookie>
+ || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>)
&& !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value;
};
@@ -925,7 +936,13 @@ namespace __variant
static constexpr decltype(auto)
__visit_invoke(_Visitor&& __visitor, _Variants... __vars)
{
- return std::__invoke(std::forward<_Visitor>(__visitor),
+ if constexpr (is_same_v<_Result_type, __variant_idx_cookie>)
+ return std::__invoke(std::forward<_Visitor>(__visitor),
+ __element_by_index_or_cookie<__indices>(
+ std::forward<_Variants>(__vars))...,
+ integral_constant<size_t, __indices>()...);
+ else
+ return std::__invoke(std::forward<_Visitor>(__visitor),
__element_by_index_or_cookie<__indices>(
std::forward<_Variants>(__vars))...);
}
@@ -1402,51 +1419,47 @@ namespace __variant
noexcept((__is_nothrow_swappable<_Types>::value && ...)
&& is_nothrow_move_constructible_v<variant>)
{
- __do_visit([this, &__rhs](auto&& __this_mem, auto&& __rhs_mem) mutable
- -> __detail::__variant::__variant_cookie
+ __do_visit<__detail::__variant::__visit_with_index>(
+ [this, &__rhs](auto&& __rhs_mem,
+ auto __rhs_index) mutable
+ -> __detail::__variant::__variant_idx_cookie
{
- if constexpr (is_same_v<
- remove_reference_t<decltype(__this_mem)>,
- remove_reference_t<decltype(__rhs_mem)>>)
+ if constexpr (__rhs_index != variant_npos)
{
- if constexpr (!is_same_v<
- remove_reference_t<decltype(__rhs_mem)>,
- __detail::__variant::__variant_cookie>)
+ if (this->index() == __rhs_index)
{
+ auto& __this_mem =
+ get<__rhs_index>(*this);
using std::swap;
swap(__this_mem, __rhs_mem);
}
+ else
+ {
+ if (this->index() != variant_npos)
+ {
+ auto __tmp(std::move(__rhs_mem));
+ __rhs = std::move(*this);
+ this->_M_destructive_move(__rhs_index,
+ std::move(__tmp));
+ }
+ else
+ {
+ this->_M_destructive_move(__rhs_index,
+ std::move(__rhs_mem));
+ __rhs._M_reset();
+ }
+ }
}
else
{
- if constexpr (is_same_v<
- remove_reference_t<decltype(__this_mem)>,
- __detail::__variant::__variant_cookie>)
+ if (this->index() != variant_npos)
{
- this->_M_destructive_move(__rhs.index(),
- std::move(__rhs_mem));
- __rhs._M_reset();
- }
- else if constexpr (is_same_v<
- remove_reference_t<decltype(__rhs_mem)>,
- __detail::__variant::__variant_cookie>)
- {
- __rhs._M_destructive_move(this->index(),
- std::move(__this_mem));
+ __rhs = std::move(*this);
this->_M_reset();
}
- else
- {
- auto __tmp(std::move(__rhs_mem));
- auto __idx = __rhs.index();
- __rhs._M_destructive_move(this->index(),
- std::move(__this_mem));
- this->_M_destructive_move(__idx,
- std::move(__tmp));
- }
}
- return {};
- }, *this, __rhs);
+ return {};
+ }, __rhs);
}
private:
@@ -1523,13 +1536,25 @@ namespace __variant
return __detail::__variant::__get<_Np>(std::move(__v));
}
- template<typename _Visitor, typename... _Variants>
+ template<bool __use_index, typename _Visitor, typename... _Variants>
+ decltype(auto)
+ __visitor_result_type(_Visitor&& __visitor, _Variants&&... __variants)
+ {
+ if constexpr(__use_index)
+ return __detail::__variant::__variant_idx_cookie{};
+ else
+ return std::forward<_Visitor>(__visitor)(
+ std::get<0>(std::forward<_Variants>(__variants))...);
+ }
+
+ template<bool __use_index, typename _Visitor, typename... _Variants>
constexpr decltype(auto)
__do_visit(_Visitor&& __visitor, _Variants&&... __variants)
{
using _Result_type =
- decltype(std::forward<_Visitor>(__visitor)(
- std::get<0>(std::forward<_Variants>(__variants))...));
+ decltype(__visitor_result_type<__use_index>(
+ std::forward<_Visitor>(__visitor),
+ std::forward<_Variants>(__variants)...));
constexpr auto& __vtable = __detail::__variant::__gen_vtable<
_Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
