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util: improve (and use) offsetof that's """standard compliant"""

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This commit is contained in:
Michael Scire 2021-10-17 21:45:02 -07:00
parent ad4c794aea
commit ec6d1a92ef
2 changed files with 71 additions and 87 deletions
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4
libraries/libvapours/include/vapours/util/util_intrusive_red_black_tree.hpp
View file

@ -502,7 +502,7 @@ namespace ams::util {
return util::GetParentPointer<Member, Derived>(node); return util::GetParentPointer<Member, Derived>(node);
} }
private: private:
static_assert(util::IsAligned(util::impl::OffsetOf<Member, Derived>::Value, alignof(void *))); static_assert(util::IsAligned(util::impl::OffsetOf<Member, Derived>::value, alignof(void *)));
}; };
template<auto T, class Derived = util::impl::GetParentType<T>> template<auto T, class Derived = util::impl::GetParentType<T>>
@ -516,7 +516,7 @@ namespace ams::util {
using TreeTypeImpl = impl::IntrusiveRedBlackTreeImpl; using TreeTypeImpl = impl::IntrusiveRedBlackTreeImpl;
static constexpr bool IsValid() { static constexpr bool IsValid() {
return util::IsAligned(util::impl::OffsetOf<Member, Derived>::Value, alignof(void *)); return util::IsAligned(util::impl::OffsetOf<Member, Derived>::value, alignof(void *));
} }
private: private:
template<class, class, class> template<class, class, class>

134
libraries/libvapours/include/vapours/util/util_parent_of_member.hpp
View file

@ -23,98 +23,85 @@ namespace ams::util {
namespace impl { namespace impl {
#define AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT 0 #define AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT 1
#if AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT #if AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT
template<size_t MaxDepth> template<std::ptrdiff_t Offset, typename P, typename M, auto Ptr>
struct OffsetOfUnionHolder { consteval std::strong_ordering TestOffsetForOffsetOfImpl() {
template<typename ParentType, typename MemberType, size_t Offset>
union UnionImpl {
using PaddingMember = char;
static constexpr size_t GetOffset() { return Offset; }
#pragma pack(push, 1) #pragma pack(push, 1)
struct { const union Union {
PaddingMember padding[Offset];
MemberType members[(sizeof(ParentType) / sizeof(MemberType)) + 1];
} data;
#pragma pack(pop)
UnionImpl<ParentType, MemberType, Offset + 1> next_union;
};
template<typename ParentType, typename MemberType>
union UnionImpl<ParentType, MemberType, MaxDepth> { /* Empty ... */ };
};
template<typename ParentType, typename MemberType>
struct OffsetOfCalculator {
using UnionHolder = typename OffsetOfUnionHolder<sizeof(MemberType)>::template UnionImpl<ParentType, MemberType, 0>;
union Union {
char c; char c;
UnionHolder first_union; struct {
ParentType parent; char padding[Offset];
M members[1 + (sizeof(P) / std::max<size_t>(sizeof(M), 1))];
/* This coerces the active member to be c. */
constexpr Union() : c() { /* ... */ }
constexpr ~Union() { std::destroy_at(std::addressof(c)); }
}; };
static constexpr Union U = {}; P p;
static constexpr const MemberType *GetNextAddress(const MemberType *start, const MemberType *target) { constexpr Union() : c() { /* ... */ }
while (start < target) { constexpr ~Union() { /* ... */ }
start++; } U;
} #pragma pack(pop)
return start;
const M *target = std::addressof(U.p.*Ptr);
const M *guess = std::addressof(U.members[0]);
/* NOTE: target == guess is definitely legal, target < guess is probably legal, definitely legal if Offset <= true offsetof. */
/* <=> may or may not be legal, but it definitely seems to work. Evaluate again, if it breaks. */
return guess <=> target;
//if (guess == target) {
// return std::strong_ordering::equal;
//} else if (guess < target) {
// return std::strong_ordering::less;
//} else {
// return std::strong_ordering::greater;
//}
} }
static constexpr std::ptrdiff_t GetDifference(const MemberType *start, const MemberType *target) { template<std::ptrdiff_t Low, std::ptrdiff_t High, typename P, typename M, auto Ptr>
return (target - start) * sizeof(MemberType); consteval std::ptrdiff_t OffsetOfImpl() {
} static_assert(Low <= High);
template<typename CurUnion> constexpr std::ptrdiff_t Guess = (Low + High) / 2;
static constexpr std::ptrdiff_t OffsetOfImpl(MemberType ParentType::*member, CurUnion &cur_union) { constexpr auto Order = TestOffsetForOffsetOfImpl<Guess, P, M, Ptr>();
constexpr size_t Offset = CurUnion::GetOffset();
const auto target = std::addressof(U.parent.*member);
const auto start = std::addressof(cur_union.data.members[0]);
const auto next = GetNextAddress(start, target);
if (next != target) { if constexpr (Order == std::strong_ordering::equal) {
if constexpr (Offset < sizeof(MemberType) - 1) { return Guess;
return OffsetOfImpl(member, cur_union.next_union); } else if constexpr (Order == std::strong_ordering::less) {
return OffsetOfImpl<Guess + 1, High, P, M, Ptr>();
} else { } else {
__builtin_unreachable(); static_assert(Order == std::strong_ordering::greater);
return OffsetOfImpl<Low, Guess - 1, P, M, Ptr>();
} }
} }
return (next - start) * sizeof(MemberType) + Offset; template<typename P, typename M, auto Ptr>
} struct OffsetOfCalculator {
static constexpr const std::ptrdiff_t Value = OffsetOfImpl<0, sizeof(P), P, M, Ptr>();
static constexpr std::ptrdiff_t OffsetOf(MemberType ParentType::*member) {
return OffsetOfImpl(member, U.first_union);
}
}; };
#else #else
template<typename T> template<typename ParentType, typename MemberType, auto Ptr>
union HelperUnion { struct OffsetOfCalculator {
T v; private:
static consteval std::ptrdiff_t Calculate() {
const union Union {
ParentType p;
char c; char c;
constexpr HelperUnion() : c() { /* ... */ } constexpr Union() : c() { /* ... */ }
constexpr ~HelperUnion() { std::destroy_at(std::addressof(c)); } constexpr ~Union() { /* ... */ }
}; } U;
const auto *parent = std::addressof(U.p);
const auto *target = std::addressof(parent->*Ptr);
template<typename ParentType, typename MemberType>
struct OffsetOfCalculator {
static constexpr std::ptrdiff_t OffsetOf(MemberType ParentType::*member) {
constexpr HelperUnion<ParentType> Holder = {};
const auto *parent = std::addressof(Holder.v);
const auto *target = std::addressof(parent->*member);
return static_cast<const uint8_t *>(static_cast<const void *>(target)) - static_cast<const uint8_t *>(static_cast<const void *>(parent)); return static_cast<const uint8_t *>(static_cast<const void *>(target)) - static_cast<const uint8_t *>(static_cast<const void *>(parent));
} }
public:
static constexpr const std::ptrdiff_t Value = Calculate();
}; };
#endif #endif
@ -135,22 +122,19 @@ namespace ams::util {
using GetMemberType = typename GetMemberPointerTraits<decltype(MemberPtr)>::Member; using GetMemberType = typename GetMemberPointerTraits<decltype(MemberPtr)>::Member;
template<auto MemberPtr, typename RealParentType = GetParentType<MemberPtr>> requires (std::derived_from<RealParentType, GetParentType<MemberPtr>> || std::same_as<RealParentType, GetParentType<MemberPtr>>) template<auto MemberPtr, typename RealParentType = GetParentType<MemberPtr>> requires (std::derived_from<RealParentType, GetParentType<MemberPtr>> || std::same_as<RealParentType, GetParentType<MemberPtr>>)
struct OffsetOf { struct OffsetOf : public std::integral_constant<std::ptrdiff_t, OffsetOfCalculator<RealParentType, GetMemberType<MemberPtr>, MemberPtr>::Value> {};
using MemberType = GetMemberType<MemberPtr>;
static constexpr std::ptrdiff_t Value = OffsetOfCalculator<RealParentType, MemberType>::OffsetOf(MemberPtr);
};
} }
template<auto MemberPtr, typename RealParentType = impl::GetParentType<MemberPtr>> template<auto MemberPtr, typename RealParentType = impl::GetParentType<MemberPtr>>
ALWAYS_INLINE RealParentType &GetParentReference(impl::GetMemberType<MemberPtr> *member) { ALWAYS_INLINE RealParentType &GetParentReference(impl::GetMemberType<MemberPtr> *member) {
constexpr std::ptrdiff_t Offset = impl::OffsetOf<MemberPtr, RealParentType>::Value; constexpr std::ptrdiff_t Offset = impl::OffsetOf<MemberPtr, RealParentType>::value;
return *static_cast<RealParentType *>(static_cast<void *>(static_cast<uint8_t *>(static_cast<void *>(member)) - Offset)); return *static_cast<RealParentType *>(static_cast<void *>(static_cast<uint8_t *>(static_cast<void *>(member)) - Offset));
} }
template<auto MemberPtr, typename RealParentType = impl::GetParentType<MemberPtr>> template<auto MemberPtr, typename RealParentType = impl::GetParentType<MemberPtr>>
ALWAYS_INLINE RealParentType const &GetParentReference(impl::GetMemberType<MemberPtr> const *member) { ALWAYS_INLINE RealParentType const &GetParentReference(impl::GetMemberType<MemberPtr> const *member) {
constexpr std::ptrdiff_t Offset = impl::OffsetOf<MemberPtr, RealParentType>::Value; constexpr std::ptrdiff_t Offset = impl::OffsetOf<MemberPtr, RealParentType>::value;
return *static_cast<const RealParentType *>(static_cast<const void *>(static_cast<const uint8_t *>(static_cast<const void *>(member)) - Offset)); return *static_cast<const RealParentType *>(static_cast<const void *>(static_cast<const uint8_t *>(static_cast<const void *>(member)) - Offset));
} }
@ -187,7 +171,7 @@ namespace ams::util {
/* Defines, for use by other code. */ /* Defines, for use by other code. */
#define OFFSETOF(parent, member) (::ams::util::impl::OffsetOf<&parent::member, parent>::Value) #define OFFSETOF(parent, member) (::ams::util::impl::OffsetOf<&parent::member, parent>::value)
#define GET_PARENT_PTR(parent, member, _arg) (::ams::util::GetParentPointer<&parent::member, parent>(_arg)) #define GET_PARENT_PTR(parent, member, _arg) (::ams::util::GetParentPointer<&parent::member, parent>(_arg))