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Minimal changes to support constexpr allocation in MSVC #1313

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Sep 22, 2020
Merged

Minimal changes to support constexpr allocation in MSVC #1313

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81819bf
Minimal changes to support constexpr allocation in MSVC
CaseyCarter Sep 22, 2020
43a393c
Remove extraneous annotations in `<xmemory>`
CaseyCarter Sep 22, 2020
4d1adb5
miscco's review comments
CaseyCarter Sep 22, 2020
43069e3
Grumble, grumble useless warnings
CaseyCarter Sep 22, 2020
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148 changes: 143 additions & 5 deletions stl/inc/memory
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Expand Up @@ -284,34 +284,136 @@ _NoThrowFwdIt uninitialized_fill_n(_NoThrowFwdIt _First, const _Diff _Count_raw,
}
#endif // _HAS_IF_CONSTEXPR

// FUNCTION TEMPLATE construct_at
#if _HAS_CXX20
template <class _Ty, class... _Types>
auto construct_at(_Ty* const _Location, _Types&&... _Args) noexcept(noexcept(::new (const_cast<void*>(
static_cast<const volatile void*>(_Location))) _Ty(_STD forward<_Types>(_Args)...))) // strengthened
_CONSTEXPR20_DYNALLOC auto construct_at(_Ty* const _Location, _Types&&... _Args) noexcept(
noexcept(::new (const_cast<void*>(static_cast<const volatile void*>(_Location)))
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HM in the uninitialized_meow PR we introduced a voidify Funktion. If it is not too far out we should wait until it is merged or reproduce it here

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The whole point of pushing this through before finishing test coverage is to avoid blocking the compiler team. If we get uninit_meow merged in time, I'll make the voidify change here. Otherwise, I'll do so in the followup. (Leaving this comment open as a reminder.)

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👍

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MSVC-PR-276291 is internally out for review, containing uninit_meow, so it's a race 🚀

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@CaseyCarter CaseyCarter Sep 22, 2020 •
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I've annotated the destroy/destroy_n test coverage followup work item in #39 to mention integration with GH-1164 and _Voidify_iter specifically so this won't be dropped.

_Ty(_STD forward<_Types>(_Args)...))) // strengthened
-> decltype(
::new (const_cast<void*>(static_cast<const volatile void*>(_Location))) _Ty(_STD forward<_Types>(_Args)...)) {
return ::new (const_cast<void*>(static_cast<const volatile void*>(_Location))) _Ty(_STD forward<_Types>(_Args)...);
}

#ifdef __cpp_lib_concepts
namespace ranges {
using _STD construct_at;
// VARIABLE ranges::construct_at
class _Construct_at_fn : private _Not_quite_object {
public:
using _Not_quite_object::_Not_quite_object;

// clang-format off
template <class _Ty, class... _Types>
requires requires(void* _Void_ptr, _Types&&... _Args) {
::new (_Void_ptr) _Ty(static_cast<_Types&&>(_Args)...);
}
_CONSTEXPR20_DYNALLOC _Ty* operator()(_Ty* _Location, _Types&&... _Args) const
noexcept(noexcept(::new (const_cast<void*>(static_cast<const volatile void*>(_Location)))
_Ty(_STD forward<_Types>(_Args)...))) /* strengthened */ {
// clang-format on
return ::new (const_cast<void*>(static_cast<const volatile void*>(_Location)))
_Ty(_STD forward<_Types>(_Args)...);
}
};

inline constexpr _Construct_at_fn construct_at{_Not_quite_object::_Construct_tag{}};
} // namespace ranges
#endif // __cpp_lib_concepts
#endif // _HAS_CXX20

#if _HAS_CXX17
// FUNCTION TEMPLATE destroy_at
template <class _Ty>
void destroy_at(_Ty* const _Location) noexcept /* strengthened */ {
_Location->~_Ty();
_CONSTEXPR20_DYNALLOC void destroy_at(_Ty* const _Location) noexcept /* strengthened */ {
#if _HAS_CXX20
if constexpr (is_array_v<_Ty>) {
_Destroy_range(_STD begin(*_Location), _STD end(*_Location));
} else
#endif // _HAS_CXX20
{
_Location->~_Ty();
}
}

#ifdef __cpp_lib_concepts
namespace ranges {
// VARIABLE ranges::destroy_at
// clang-format off
template <_No_throw_input_iterator _It, _No_throw_sentinel_for<_It> _Se>
requires destructible<iter_value_t<_It>>
_NODISCARD _CONSTEXPR20_DYNALLOC _It _Destroy_unchecked(_It _First, _Se _Last) noexcept;
// clang-format on

class _Destroy_at_fn : private _Not_quite_object {
public:
using _Not_quite_object::_Not_quite_object;

template <destructible _Ty>
_CONSTEXPR20_DYNALLOC void operator()(_Ty* const _Location) const noexcept {
if constexpr (is_array_v<_Ty>) {
(void) _RANGES _Destroy_unchecked(_RANGES begin(*_Location), _RANGES end(*_Location));
} else {
_Location->~_Ty();
}
}
};

inline constexpr _Destroy_at_fn destroy_at{_Not_quite_object::_Construct_tag{}};
} // namespace ranges
#endif // __cpp_lib_concepts

// FUNCTION TEMPLATE destroy
template <class _NoThrowFwdIt>
void destroy(const _NoThrowFwdIt _First, const _NoThrowFwdIt _Last) { // destroy all elements in [_First, _Last)
_Adl_verify_range(_First, _Last);
_Destroy_range(_Get_unwrapped(_First), _Get_unwrapped(_Last));
}

#ifdef __cpp_lib_concepts
namespace ranges {
// VARIABLE ranges::destroy
// clang-format off
template <_No_throw_input_iterator _It, _No_throw_sentinel_for<_It> _Se>
requires destructible<iter_value_t<_It>>
_NODISCARD _CONSTEXPR20_DYNALLOC _It _Destroy_unchecked(_It _First, const _Se _Last) noexcept {
// clang-format on
for (; _First != _Last; ++_First) {
_RANGES destroy_at(_STD addressof(*_First));
}

return _First;
}

class _Destroy_fn : private _Not_quite_object {
public:
using _Not_quite_object::_Not_quite_object;

// clang-format off
template <_No_throw_input_iterator _It, _No_throw_sentinel_for<_It> _Se>
requires destructible<iter_value_t<_It>>
/* _CONSTEXPR20_DYNALLOC */ _It operator()(_It _First, _Se _Last) const noexcept {
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// clang-format on
_Adl_verify_range(_First, _Last);
_Seek_wrapped(_First,
_RANGES _Destroy_unchecked(_Get_unwrapped(_STD move(_First)), _Get_unwrapped(_STD move(_Last))));
return _First;
}

// clang-format off
template <_No_throw_input_range _Rng>
requires destructible<range_value_t<_Rng>>
/* _CONSTEXPR20_DYNALLOC */ borrowed_iterator_t<_Rng> operator()(_Rng&& _Range) const noexcept {
// clang-format on
auto _First = _RANGES begin(_Range);
_Seek_wrapped(_First, _RANGES _Destroy_unchecked(_Get_unwrapped(_STD move(_First)), _Uend(_Range)));
return _First;
}
};

inline constexpr _Destroy_fn destroy{_Not_quite_object::_Construct_tag{}};
} // namespace ranges
#endif // __cpp_lib_concepts

// FUNCTION TEMPLATE destroy_n
template <class _NoThrowFwdIt, class _Diff>
_NoThrowFwdIt destroy_n(_NoThrowFwdIt _First, const _Diff _Count_raw) {
Expand All @@ -335,6 +437,42 @@ _NoThrowFwdIt destroy_n(_NoThrowFwdIt _First, const _Diff _Count_raw) {
return _First;
}

#ifdef __cpp_lib_concepts
namespace ranges {
// VARIABLE ranges::destroy_n
class _Destroy_n_fn : private _Not_quite_object {
public:
using _Not_quite_object::_Not_quite_object;

// clang-format off
template <_No_throw_input_iterator _It>
requires destructible<iter_value_t<_It>>
/* _CONSTEXPR20_DYNALLOC */ _It operator()(_It _First, const iter_difference_t<_It> _Count) const noexcept {
// clang-format on
if (_Count <= 0) {
return _First;
}

auto _UFirst = _Get_unwrapped_n(_STD move(_First), _Count);
if constexpr (is_trivially_destructible_v<iter_value_t<_It>>) {
_RANGES advance(_UFirst, _Count);
} else {
do {
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_RANGES destroy_at(_STD addressof(*_UFirst));
++_UFirst;
--_Count;
} while (_Count > 0);
}

_Seek_wrapped(_First, _STD move(_UFirst));
return _First;
}
};

inline constexpr _Destroy_n_fn destroy_n{_Not_quite_object::_Construct_tag{}};
} // namespace ranges
#endif // __cpp_lib_concepts

// FUNCTION TEMPLATE uninitialized_default_construct
template <class _NoThrowFwdIt>
void uninitialized_default_construct(const _NoThrowFwdIt _First, const _NoThrowFwdIt _Last) {
Expand Down
15 changes: 7 additions & 8 deletions stl/inc/xmemory
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Expand Up @@ -257,10 +257,10 @@ _Pointer _Refancy(_Pointer _Ptr) noexcept {

// FUNCTION TEMPLATE _Destroy_in_place
template <class _NoThrowFwdIt, class _NoThrowSentinel>
/* _CONSTEXPR20_DYNALLOC */ void _Destroy_range(_NoThrowFwdIt _First, _NoThrowSentinel _Last) noexcept;
_CONSTEXPR20_DYNALLOC void _Destroy_range(_NoThrowFwdIt _First, _NoThrowSentinel _Last) noexcept;

template <class _Ty>
/* _CONSTEXPR20_DYNALLOC */ void _Destroy_in_place(_Ty& _Obj) noexcept {
_CONSTEXPR20_DYNALLOC void _Destroy_in_place(_Ty& _Obj) noexcept {
#if _HAS_IF_CONSTEXPR
if constexpr (is_array_v<_Ty>) {
_Destroy_range(_Obj, _Obj + extent_v<_Ty>);
Expand Down Expand Up @@ -951,8 +951,7 @@ void _Pocs(_Alloc& _Left, _Alloc& _Right) noexcept {

// FUNCTION TEMPLATE _Destroy_range WITH ALLOC
template <class _Alloc>
/* _CONSTEXPR20_DYNALLOC */ void _Destroy_range(
_Alloc_ptr_t<_Alloc> _First, const _Alloc_ptr_t<_Alloc> _Last, _Alloc& _Al) noexcept {
void _Destroy_range(_Alloc_ptr_t<_Alloc> _First, const _Alloc_ptr_t<_Alloc> _Last, _Alloc& _Al) noexcept {
// note that this is an optimization for debug mode codegen; in release mode the BE removes all of this
using _Ty = typename _Alloc::value_type;
if _CONSTEXPR_IF (!conjunction_v<is_trivially_destructible<_Ty>, _Uses_default_destroy<_Alloc, _Ty*>>) {
Expand All @@ -964,7 +963,7 @@ template <class _Alloc>

// FUNCTION TEMPLATE _Destroy_range
template <class _NoThrowFwdIt, class _NoThrowSentinel>
/* _CONSTEXPR20_DYNALLOC */ void _Destroy_range(_NoThrowFwdIt _First, const _NoThrowSentinel _Last) noexcept {
_CONSTEXPR20_DYNALLOC void _Destroy_range(_NoThrowFwdIt _First, const _NoThrowSentinel _Last) noexcept {
// note that this is an optimization for debug mode codegen; in release mode the BE removes all of this
if _CONSTEXPR_IF (!is_trivially_destructible_v<_Iter_value_t<_NoThrowFwdIt>>) {
for (; _First != _Last; ++_First) {
Expand Down Expand Up @@ -1425,18 +1424,18 @@ struct _Uninitialized_backout { // struct to undo partially constructed ranges i
_Uninitialized_backout(const _Uninitialized_backout&) = delete;
_Uninitialized_backout& operator=(const _Uninitialized_backout&) = delete;

/* _CONSTEXPR20_DYNALLOC */ ~_Uninitialized_backout() {
~_Uninitialized_backout() {
_Destroy_range(_First, _Last);
}

template <class... _Types>
/* _CONSTEXPR20_DYNALLOC */ void _Emplace_back(_Types&&... _Vals) {
void _Emplace_back(_Types&&... _Vals) {
// construct a new element at *_Last and increment
_Construct_in_place(*_Last, _STD forward<_Types>(_Vals)...);
++_Last;
}

/* _CONSTEXPR20_DYNALLOC */ _NoThrowFwdIt _Release() { // suppress any exception handling backout and return _Last
_NoThrowFwdIt _Release() { // suppress any exception handling backout and return _Last
_First = _Last;
return _Last;
}
Expand Down
7 changes: 7 additions & 0 deletions stl/inc/yvals_core.h
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Original file line number Diff line number Diff line change
Expand Up @@ -541,6 +541,13 @@
#define _CONSTEXPR20 inline
#endif // ^^^ inline (not constexpr) in C++17 and earlier ^^^

// Functions that became constexpr in C++20 via P0784R7
#if _HAS_CXX20 && defined(__cpp_constexpr_dynamic_alloc)
#define _CONSTEXPR20_DYNALLOC constexpr
#else
#define _CONSTEXPR20_DYNALLOC inline
#endif

// P0607R0 Inline Variables For The STL
#if _HAS_CXX17
#define _INLINE_VAR inline
Expand Down
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