On Sat, 30 Mar 2019 at 20:00, Ville Voutilainen
<ville.voutilai...@gmail.com> wrote:
>
> 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.
Here. This does produce 17 symbols instead of 9 for a test with a
single operator== comparison.
But it's not 47 like it is with the code before this patch.
2019-04-01 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.
(__visit_with_index): Likewise.
(_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.
(relops): Do single-visitation with an index visitor.
(swap): Likewise.
(__visitor_result_type): New.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 7fd6947..3a11e1c 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))...);
}
@@ -1082,25 +1099,25 @@ namespace __variant
const variant<_Types...>& __rhs) \
{ \
bool __ret = true; \
- __do_visit([&__ret, &__lhs, __rhs] \
- (auto&& __this_mem, auto&& __rhs_mem) mutable \
- -> __detail::__variant::__variant_cookie \
+ __do_visit<__detail::__variant::__visit_with_index>( \
+ [&__ret, &__lhs, __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)>> \
- || is_same_v<decltype(__this_mem), \
- __detail::__variant::__variant_cookie>) \
- __ret = (__lhs.index() + 1) __OP (__rhs.index() + 1); \
- else if constexpr (is_same_v< \
- remove_reference_t<decltype(__this_mem)>, \
- remove_reference_t<decltype(__rhs_mem)>> \
- && !is_same_v< \
- remove_reference_t<decltype(__this_mem)>, \
- __detail::__variant::__variant_cookie>) \
- __ret = __this_mem __OP __rhs_mem; \
+ if constexpr (__rhs_index != variant_npos) \
+ { \
+ if (__lhs.index() == __rhs_index) \
+ { \
+ auto& __this_mem = get<__rhs_index>(__lhs); \
+ __ret = __this_mem __OP __rhs_mem; \
+ } \
+ else \
+ __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
+ } \
+ else \
+ __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
return {}; \
- }, __lhs, __rhs); \
+ }, __rhs); \
return __ret; \
} \
\
@@ -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;
