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AK: Use compiler builtins for MakeIntegerSequence/TypeListElement

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These recursive templates have a measurable impact on the compile speed
of Variant-heavy code like LibWeb. Using these builtins leads to a 2.5%
speedup for the measured compilation units.
This commit is contained in:
Daniel Bertalan 2023-06-27 07:48:39 +02:00 committed by Andreas Kling
parent 4596d41291
commit 1a10e904b5
Notes: sideshowbarker 2024-07-17 06:40:35 +09:00 
Author: https://github.com/BertalanD
Commit: https://github.com/SerenityOS/serenity/commit/1a10e904b5
Pull-request: https://github.com/SerenityOS/serenity/pull/19663
2 changed files with 15 additions and 0 deletions
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8
AK/StdLibExtraDetails.h
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@ -454,6 +454,13 @@ struct IntegerSequence {
template<unsigned... Indices>
using IndexSequence = IntegerSequence<unsigned, Indices...>;
#if __has_builtin(__make_integer_seq)
template<typename T, T N>
using MakeIntegerSequence = __make_integer_seq<IntegerSequence, T, N>;
#elif __has_builtin(__integer_pack)
template<typename T, T N>
using MakeIntegerSequence = IntegerSequence<T, __integer_pack(N)...>;
#else
template<typename T, T N, T... Ts>
auto make_integer_sequence_impl()
{
@ -465,6 +472,7 @@ auto make_integer_sequence_impl()
template<typename T, T N>
using MakeIntegerSequence = decltype(make_integer_sequence_impl<T, N>());
#endif
template<unsigned N>
using MakeIndexSequence = MakeIntegerSequence<unsigned, N>;

7
AK/TypeList.h
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@ -16,6 +16,12 @@ struct TypeList;
template<unsigned Index, typename List>
struct TypeListElement;
#if __has_builtin(__type_pack_element)
template<unsigned Index, typename... Types>
struct TypeListElement<Index, TypeList<Types...>> {
using Type = __type_pack_element<Index, Types...>;
};
#else
template<unsigned Index, typename Head, typename... Tail>
struct TypeListElement<Index, TypeList<Head, Tail...>>
: TypeListElement<Index - 1, TypeList<Tail...>> {
@ -25,6 +31,7 @@ template<typename Head, typename... Tail>
struct TypeListElement<0, TypeList<Head, Tail...>> {
using Type = Head;
};
#endif
template<typename... Types>
struct TypeList {