[libcxx/variant] Introduce `switch`-based mechanism for `std::visit`.
This patch introduces mechanism for `std::visit` backed by `switch`.
The `switch` is structured such that it's a flattened manual vtable (an n-ary array).
The `switch` mechanism is enabled if `(1 * ... * vs.size()) < 1024`.
The following are performance numbers from the benchmarks added in D85419, tested on my 2017 Macbook Pro.
```
$ ./projects/libcxx/benchmarks/variant_visit_1.libcxx.out
2020-08-09 23:55:14
Running ./projects/libcxx/benchmarks/variant_visit_1.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 2.03, 2.36, 2.43
------------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------------
BM_Visit<1, 1> 0.260 ns 0.260 ns 1000000000
BM_Visit<1, 2> 1.56 ns 1.56 ns 435925220
BM_Visit<1, 3> 1.55 ns 1.55 ns 444416228
BM_Visit<1, 4> 1.57 ns 1.57 ns 427951336
BM_Visit<1, 5> 1.57 ns 1.56 ns 444766371
BM_Visit<1, 6> 1.70 ns 1.68 ns 446639358
BM_Visit<1, 7> 1.64 ns 1.64 ns 400441630
BM_Visit<1, 8> 1.56 ns 1.56 ns 430729471
BM_Visit<1, 9> 1.58 ns 1.58 ns 449894596
BM_Visit<1, 10> 1.54 ns 1.54 ns 449660506
BM_Visit<1, 20> 1.56 ns 1.56 ns 450813074
BM_Visit<1, 30> 1.59 ns 1.59 ns 440032940
BM_Visit<1, 40> 1.59 ns 1.59 ns 443731656
BM_Visit<1, 50> 1.56 ns 1.56 ns 444709859
BM_Visit<1, 60> 1.59 ns 1.58 ns 439527320
BM_Visit<1, 70> 1.57 ns 1.57 ns 438450890
BM_Visit<1, 80> 1.58 ns 1.58 ns 443001525
BM_Visit<1, 90> 1.63 ns 1.62 ns 448456349
BM_Visit<1, 100> 1.57 ns 1.57 ns 445740630
$ ./projects/libcxx/benchmarks/variant_visit_2.libcxx.out
2020-08-09 23:59:35
Running ./projects/libcxx/benchmarks/variant_visit_2.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 1.40, 1.94, 2.22
-----------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------
BM_Visit<2, 1> 0.261 ns 0.260 ns 1000000000
BM_Visit<2, 2> 1.55 ns 1.54 ns 432844219
BM_Visit<2, 3> 1.30 ns 1.30 ns 532529974
BM_Visit<2, 4> 1.54 ns 1.54 ns 446055910
BM_Visit<2, 5> 1.31 ns 1.31 ns 531099680
BM_Visit<2, 6> 1.56 ns 1.56 ns 443203475
BM_Visit<2, 7> 1.29 ns 1.29 ns 526478087
BM_Visit<2, 8> 1.56 ns 1.56 ns 439000834
BM_Visit<2, 9> 1.30 ns 1.30 ns 528756817
BM_Visit<2, 10> 1.56 ns 1.55 ns 442923039
BM_Visit<2, 20> 1.35 ns 1.35 ns 517021072
BM_Visit<2, 30> 1.60 ns 1.59 ns 419724661
BM_Visit<2, 40> 1.45 ns 1.44 ns 472137163
BM_Visit<2, 50> 1.65 ns 1.65 ns 421389743
$ ./projects/libcxx/benchmarks/variant_visit_3.libcxx.out
2020-08-10 00:01:32
Running ./projects/libcxx/benchmarks/variant_visit_3.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 2.20, 2.01, 2.21
-----------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------
BM_Visit<3, 1> 0.272 ns 0.271 ns 1000000000
BM_Visit<3, 2> 1.87 ns 1.86 ns 361858090
BM_Visit<3, 3> 1.77 ns 1.77 ns 391192579
BM_Visit<3, 4> 1.84 ns 1.84 ns 374694223
BM_Visit<3, 5> 1.75 ns 1.75 ns 408270392
BM_Visit<3, 6> 1.88 ns 1.88 ns 378759185
BM_Visit<3, 7> 1.79 ns 1.79 ns 395498102
BM_Visit<3, 8> 1.85 ns 1.85 ns 371660366
BM_Visit<3, 9> 1.80 ns 1.80 ns 386872851
BM_Visit<3, 10> 1.84 ns 1.84 ns 362367606
BM_Visit<3, 15> 1.77 ns 1.77 ns 392060220
BM_Visit<3, 20> 1.85 ns 1.85 ns 379157188
```
```
$ ./projects/libcxx/benchmarks/variant_visit_1.libcxx.out
2020-08-10 00:05:57
Running ./projects/libcxx/benchmarks/variant_visit_1.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 2.27, 2.36, 2.34
------------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------------
BM_Visit<1, 1> 0.271 ns 0.271 ns 1000000000
BM_Visit<1, 2> 0.269 ns 0.269 ns 1000000000
BM_Visit<1, 3> 0.271 ns 0.271 ns 1000000000
BM_Visit<1, 4> 0.270 ns 0.270 ns 1000000000
BM_Visit<1, 5> 0.269 ns 0.269 ns 1000000000
BM_Visit<1, 6> 0.270 ns 0.269 ns 1000000000
BM_Visit<1, 7> 0.265 ns 0.265 ns 1000000000
BM_Visit<1, 8> 0.269 ns 0.269 ns 1000000000
BM_Visit<1, 9> 0.268 ns 0.268 ns 1000000000
BM_Visit<1, 10> 0.269 ns 0.269 ns 1000000000
BM_Visit<1, 20> 0.267 ns 0.267 ns 1000000000
BM_Visit<1, 30> 0.272 ns 0.272 ns 1000000000
BM_Visit<1, 40> 0.268 ns 0.268 ns 1000000000
BM_Visit<1, 50> 0.268 ns 0.268 ns 1000000000
BM_Visit<1, 60> 0.268 ns 0.268 ns 1000000000
BM_Visit<1, 70> 0.269 ns 0.269 ns 1000000000
BM_Visit<1, 80> 0.266 ns 0.266 ns 1000000000
BM_Visit<1, 90> 0.268 ns 0.268 ns 1000000000
BM_Visit<1, 100> 0.267 ns 0.267 ns 1000000000
$ ./projects/libcxx/benchmarks/variant_visit_2.libcxx.out
2020-08-12 04:09:59
Running ./projects/libcxx/benchmarks/variant_visit_2.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 2.17, 4.20, 4.78
-----------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------
BM_Visit<2, 1> 0.302 ns 0.301 ns 1000000000
BM_Visit<2, 2> 0.297 ns 0.295 ns 1000000000
BM_Visit<2, 3> 0.353 ns 0.351 ns 1000000000
BM_Visit<2, 4> 0.276 ns 0.276 ns 1000000000
BM_Visit<2, 5> 0.285 ns 0.283 ns 1000000000
BM_Visit<2, 6> 0.290 ns 0.287 ns 1000000000
BM_Visit<2, 7> 0.282 ns 0.280 ns 1000000000
BM_Visit<2, 8> 0.290 ns 0.287 ns 1000000000
BM_Visit<2, 9> 0.291 ns 0.285 ns 1000000000
BM_Visit<2, 10> 0.293 ns 0.287 ns 1000000000
BM_Visit<2, 20> 1.70 ns 1.68 ns 391400375
BM_Visit<2, 30> 1.64 ns 1.63 ns 418925874
BM_Visit<2, 40> 1.63 ns 1.62 ns 423623677
BM_Visit<2, 50> 1.68 ns 1.67 ns 411687212
$ ./projects/libcxx/benchmarks/variant_visit_3.libcxx.out
2020-08-12 04:10:43
Running ./projects/libcxx/benchmarks/variant_visit_3.libcxx.out
Run on (8 X 3100 MHz CPU s)
CPU Caches:
L1 Data 32K (x4)
L1 Instruction 32K (x4)
L2 Unified 262K (x4)
L3 Unified 8388K (x1)
Load Average: 1.57, 3.76, 4.59
-----------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------
BM_Visit<3, 1> 0.271 ns 0.270 ns 1000000000
BM_Visit<3, 2> 0.344 ns 0.334 ns 1000000000
BM_Visit<3, 3> 0.347 ns 0.336 ns 1000000000
BM_Visit<3, 4> 0.300 ns 0.296 ns 1000000000
BM_Visit<3, 5> 0.290 ns 0.286 ns 1000000000
BM_Visit<3, 6> 0.272 ns 0.271 ns 1000000000
BM_Visit<3, 7> 1.72 ns 1.71 ns 415765841
BM_Visit<3, 8> 1.73 ns 1.72 ns 408909555
BM_Visit<3, 9> 2.16 ns 2.04 ns 380898485
BM_Visit<3, 10> 2.45 ns 2.40 ns 295714256
BM_Visit<3, 15> 1.92 ns 1.85 ns 375990332
BM_Visit<3, 20> 1.66 ns 1.65 ns 414456233
```
Differential Revision: https://reviews.llvm.org/D85420
GitOrigin-RevId: a175a96517c5d9dc05ba13a6481b1b031a53a22f
diff --git a/include/variant b/include/variant
index 33d5dc7..c18ef55 100644
--- a/include/variant
+++ b/include/variant
@@ -354,9 +354,9 @@
enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
-template <typename _Tp,
- template <typename> class _IsTriviallyAvailable,
- template <typename> class _IsAvailable>
+template <class _Tp,
+ template <class> class _IsTriviallyAvailable,
+ template <class> class _IsAvailable>
constexpr _Trait __trait =
_IsTriviallyAvailable<_Tp>::value
? _Trait::_TriviallyAvailable
@@ -373,7 +373,7 @@
return __result;
}
-template <typename... _Types>
+template <class... _Types>
struct __traits {
static constexpr _Trait __copy_constructible_trait =
__common_trait({__trait<_Types,
@@ -434,183 +434,270 @@
namespace __visitation {
+#define _LIBCPP_VARIANT_CASES_4(_Case, _Base) \
+ _Case(_Base + 0) \
+ _Case(_Base + 1) \
+ _Case(_Base + 2) \
+ _Case(_Base + 3)
+
+#define _LIBCPP_VARIANT_CASES_16(_Case, _Base) \
+ _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 0) \
+ _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 1) \
+ _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 2) \
+ _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 3)
+
+#define _LIBCPP_VARIANT_CASES_64(_Case, _Base) \
+ _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 0) \
+ _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 1) \
+ _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 2) \
+ _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 3)
+
+#define _LIBCPP_VARIANT_CASES_256(_Case, _Base) \
+ _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 0) \
+ _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 1) \
+ _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 2) \
+ _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 3)
+
+#define _LIBCPP_VARIANT_CASES(_NumCases, _Case) \
+ _LIBCPP_CONCAT(_LIBCPP_VARIANT_CASES_, _NumCases)(_Case, 0)
+
+#define _LIBCPP_VARIANT_SWITCH_MAX 256
+
+template <class _Iter, class _Fp, size_t... _Is>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr void __fill_cartesian_impl(
+ _Iter __iter, _Fp __f, index_sequence<_Is...>) {
+ *__iter = __f(integral_constant<size_t, _Is>{}...);
+}
+
+template <class _Iter, class _Fp, size_t... _Is, size_t... _Js, class... _Ls>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr void __fill_cartesian_impl(
+ _Iter __iter, _Fp __f, index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) {
+ constexpr size_t _Mp = (1 * ... * _Ls::size());
+ (__fill_cartesian_impl(
+ __iter + _Js * _Mp, __f, index_sequence<_Is..., _Js>{}, __ls...), ...);
+}
+
+template <size_t... _Ns, class _Iter, class _Fp>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr void __fill_cartesian(_Iter __iter, _Fp __f) {
+ __fill_cartesian_impl(
+ __iter, __f, index_sequence<>{}, make_index_sequence<_Ns>{}...);
+}
+
+template <size_t _Np, size_t... _Ns>
+struct __multi {
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr size_t __size = (_Np * ... * _Ns);
+
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr size_t
+ __index(const size_t (&__is)[sizeof...(_Ns) + 1]) noexcept {
+ constexpr size_t __ns[] = {_Ns..., 1};
+ size_t __result = 0;
+ for (size_t __i = 0; __i < sizeof...(_Ns) + 1; ++__i) {
+ if (__is[__i] == variant_npos) {
+ return variant_npos;
+ }
+ __result += __is[__i];
+ __result *= __ns[__i];
+ }
+ return __result;
+ }
+};
+
+template <size_t... _Ns>
+struct __indices {
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __value = [] {
+ using _Tp = array<size_t, sizeof...(_Ns)>;
+ array<_Tp, (1 * ... * _Ns)> __result = {};
+ __fill_cartesian<_Ns...>(__result.begin(),
+ [](auto... __is) -> _Tp { return {__is...}; });
+ return __result;
+ }();
+};
+
+template <size_t... _Ns, class _Fp, class _Rp, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr auto __make_vtable_impl(_Fp __f, _Rp (*)(_Args...)) {
+ array<_Rp (*)(_Args...), (1 * ... * _Ns) + 1> __result = {
+ [](_Args...) -> _Rp { __throw_bad_variant_access(); }
+ };
+ __fill_cartesian<_Ns...>(__result.begin() + 1, __f);
+ return __result;
+}
+
+template <size_t... _Ns, class _Fp>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr auto __make_vtable(_Fp __f) {
+ using _Tp = decltype(__f(integral_constant<size_t, (_Ns, 0)>{}...));
+ return __make_vtable_impl<_Ns...>(__f, _Tp{});
+}
+
struct __base {
- template <class _Visitor, class... _Vs>
+ template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
- __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
- constexpr auto __fdiagonal =
- __make_fdiagonal<_Visitor&&,
- decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
- return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
- _VSTD::forward<_Vs>(__vs).__as_base()...);
- }
-
- template <class _Visitor, class... _Vs>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
- _Vs&&... __vs) {
- constexpr auto __fmatrix =
- __make_fmatrix<_Visitor&&,
- decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
- return __at(__fmatrix, __vs.index()...)(
- _VSTD::forward<_Visitor>(__visitor),
- _VSTD::forward<_Vs>(__vs).__as_base()...);
- }
-
-private:
- template <class _Tp>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr const _Tp& __at(const _Tp& __elem) { return __elem; }
-
- template <class _Tp, size_t _Np, typename... _Indices>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
- size_t __index, _Indices... __indices) {
- return __at(__elems[__index], __indices...);
- }
-
- template <class _Fp, class... _Fs>
- static constexpr void __std_visit_visitor_return_type_check() {
- static_assert(
- __all<is_same_v<_Fp, _Fs>...>::value,
- "`std::visit` requires the visitor to have a single return type.");
- }
-
- template <class... _Fs>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_farray(_Fs&&... __fs) {
- __std_visit_visitor_return_type_check<__uncvref_t<_Fs>...>();
- using __result = array<common_type_t<__uncvref_t<_Fs>...>, sizeof...(_Fs)>;
- return __result{{_VSTD::forward<_Fs>(__fs)...}};
- }
-
- template <std::size_t... _Is>
- struct __dispatcher {
- template <class _Fp, class... _Vs>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
+ __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
+ constexpr size_t __size = __uncvref_t<_Vp>::__size();
+ static_assert(__size == __uncvref_t<_Wp>::__size());
+ constexpr auto __dispatch = [](auto __i) {
+ return +[](_Vis&& __vis, _Vp&& __v, _Wp&& __w) -> decltype(auto) {
+ constexpr size_t _Ip = decltype(__i)::value;
return __invoke_constexpr(
- static_cast<_Fp>(__f),
- __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
+ _VSTD::forward<_Vis>(__vis),
+ __access::__base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)),
+ __access::__base::__get_alt<_Ip>(_VSTD::forward<_Wp>(__w)));
+ };
+ };
+#define _LIBCPP_VARIANT_CASE(_Ip) \
+ case _Ip: { \
+ if constexpr (_Ip < __size) { \
+ return __dispatch(integral_constant<size_t, _Ip>{})( \
+ _VSTD::forward<_Vis>(__vis), \
+ _VSTD::forward<_Vp>(__v), \
+ _VSTD::forward<_Wp>(__w)); \
+ } else { \
+ _LIBCPP_UNREACHABLE(); \
+ } \
+ }
+ if constexpr (__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
+ switch (__index) {
+ _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
+ default: __throw_bad_variant_access();
+ }
+ } else {
+ constexpr auto __vtable = __make_vtable<__size>(__dispatch);
+ return __vtable[__index + 1](_VSTD::forward<_Vis>(__vis),
+ _VSTD::forward<_Vp>(__v),
+ _VSTD::forward<_Wp>(__w));
}
- };
-
- template <class _Fp, class... _Vs, size_t... _Is>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_dispatch(index_sequence<_Is...>) {
- return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
+#undef _LIBCPP_VARIANT_CASE
}
- template <size_t _Ip, class _Fp, class... _Vs>
+ template <size_t... _Is, class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fdiagonal_impl() {
- return __make_dispatch<_Fp, _Vs...>(
- index_sequence<(__identity<_Vs>{}, _Ip)...>{});
+ static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
+ if constexpr (sizeof...(_Vs) == 0) {
+ return __invoke_constexpr(_VSTD::forward<_Vis>(__vis));
+ } else {
+ return __visit_alt_impl(index_sequence_for<_Vs...>{},
+ _VSTD::forward<_Vis>(__vis),
+ _VSTD::forward<_Vs>(__vs)...);
+ }
}
- template <class _Fp, class... _Vs, size_t... _Is>
+ template <size_t... _Is, class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
- return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
+ static constexpr decltype(auto)
+ __visit_alt_impl(index_sequence<_Is...>, _Vis&& __vis, _Vs&&... __vs) {
+ using __multi = __multi<__uncvref_t<_Vs>::__size()...>;
+ constexpr auto __dispatch = [](auto... __is) {
+ return +[](_Vis&& __vis, _Vs&&... __vs) {
+ return __invoke_constexpr(
+ _VSTD::forward<_Vis>(__vis),
+ __access::__base::__get_alt<decltype(__is)::value>(
+ _VSTD::forward<_Vs>(__vs))...);
+ };
+ };
+#define _LIBCPP_VARIANT_CASE(_Ip) \
+ case _Ip: { \
+ if constexpr (_Ip < __multi::__size) { \
+ return __dispatch(integral_constant<size_t, __itable[_Ip][_Is]>{}...)( \
+ _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...); \
+ } else { \
+ _LIBCPP_UNREACHABLE(); \
+ } \
}
-
- template <class _Fp, class _Vp, class... _Vs>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fdiagonal() {
- constexpr size_t _Np = __uncvref_t<_Vp>::__size();
- static_assert(__all<(_Np == __uncvref_t<_Vs>::__size())...>::value);
- return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
- }
-
- template <class _Fp, class... _Vs, size_t... _Is>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
- return __make_dispatch<_Fp, _Vs...>(__is);
- }
-
- template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
- index_sequence<_Js...>,
- _Ls... __ls) {
- return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
- index_sequence<_Is..., _Js>{}, __ls...)...);
- }
-
- template <class _Fp, class... _Vs>
- inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_fmatrix() {
- return __make_fmatrix_impl<_Fp, _Vs...>(
- index_sequence<>{}, make_index_sequence<__uncvref_t<_Vs>::__size()>{}...);
+ if constexpr (__multi::__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
+ constexpr const auto& __itable =
+ __indices<__uncvref_t<_Vs>::__size()...>::__value;
+ switch (__multi::__index({__vs.index()...})) {
+ _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
+ default: __throw_bad_variant_access();
+ }
+ } else {
+ constexpr auto __vtable =
+ __make_vtable<__uncvref_t<_Vs>::__size()...>(__dispatch);
+ return __vtable[__multi::__index({__vs.index()...}) + 1](
+ _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...);
+ }
+#undef _LIBCPP_VARIANT_CASE
}
};
struct __variant {
- template <class _Visitor, class... _Vs>
+ template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
- __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
return __base::__visit_alt_at(__index,
- _VSTD::forward<_Visitor>(__visitor),
- _VSTD::forward<_Vs>(__vs).__impl...);
+ _VSTD::forward<_Vis>(__vis),
+ _VSTD::forward<_Vp>(__v).__impl,
+ _VSTD::forward<_Wp>(__w).__impl);
}
- template <class _Visitor, class... _Vs>
+ template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
- _Vs&&... __vs) {
- return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
+ static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
+ return __base::__visit_alt(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vs>(__vs).__impl...);
}
- template <class _Visitor, class... _Vs>
+ template <class _Vis, class _Vp, class _Wp>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
- __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
- return __visit_alt_at(
- __index,
- __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
- _VSTD::forward<_Vs>(__vs)...);
+ __visit_value_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
+ return __visit_alt_at(__index,
+ __make_value_visitor(_VSTD::forward<_Vis>(__vis)),
+ _VSTD::forward<_Vp>(__v),
+ _VSTD::forward<_Wp>(__w));
}
- template <class _Visitor, class... _Vs>
+ template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
- _Vs&&... __vs) {
- return __visit_alt(
- __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
- _VSTD::forward<_Vs>(__vs)...);
+ static constexpr decltype(auto) __visit_value(_Vis&& __vis, _Vs&&... __vs) {
+ return __visit_alt(__make_value_visitor(_VSTD::forward<_Vis>(__vis)),
+ _VSTD::forward<_Vs>(__vs)...);
}
private:
- template <class _Visitor, class... _Values>
+ template <class _Vis, class... _Values>
+ inline _LIBCPP_INLINE_VISIBILITY
static constexpr void __std_visit_exhaustive_visitor_check() {
- static_assert(is_invocable_v<_Visitor, _Values...>,
+ static_assert(is_invocable_v<_Vis, _Values...>,
"`std::visit` requires the visitor to be exhaustive.");
}
- template <class _Visitor>
+ template <class _Vis>
struct __value_visitor {
template <class... _Alts>
inline _LIBCPP_INLINE_VISIBILITY
constexpr decltype(auto) operator()(_Alts&&... __alts) const {
__std_visit_exhaustive_visitor_check<
- _Visitor,
- decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
- return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
+ _Vis, decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
+ return __invoke_constexpr(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Alts>(__alts).__value...);
}
- _Visitor&& __visitor;
+ _Vis&& __vis;
};
- template <class _Visitor>
+ template <class _Vis>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
- return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
+ static constexpr auto __make_value_visitor(_Vis&& __vis) {
+ return __value_visitor<_Vis>{_VSTD::forward<_Vis>(__vis)};
}
};
+#undef _LIBCPP_VARIANT_SWITCH_MAX
+#undef _LIBCPP_VARIANT_CASES
+#undef _LIBCPP_VARIANT_CASES_256
+#undef _LIBCPP_VARIANT_CASES_64
+#undef _LIBCPP_VARIANT_CASES_16
+#undef _LIBCPP_VARIANT_CASES_4
+
} // namespace __visitation
template <size_t _Index, class _Tp>
@@ -633,7 +720,7 @@
#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
template <size_t _Index, class _Tp, class... _Types> \
- union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
+ union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
_Index, \
_Tp, \
_Types...> { \
@@ -787,9 +874,9 @@
template <size_t _Ip, class _Tp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
- ::new ((void*)_VSTD::addressof(__a))
+ auto* result = ::new ((void*)_VSTD::addressof(__a))
__alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
- return __a.__value;
+ return result->__value;
}
template <class _Rhs>
@@ -816,7 +903,7 @@
#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
move_constructor) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
move_constructible_trait> \
: public __constructor<__traits<_Types...>> { \
using __base_type = __constructor<__traits<_Types...>>; \
@@ -856,7 +943,7 @@
#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
copy_constructor) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
copy_constructible_trait> \
: public __move_constructor<__traits<_Types...>> { \
using __base_type = __move_constructor<__traits<_Types...>>; \
@@ -902,7 +989,7 @@
auto& __emplace(_Args&&... __args) {
this->__destroy();
auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
- _VSTD::forward<_Args>(__args)...);
+ _VSTD::forward<_Args>(__args)...);
this->__index = _Ip;
return __res;
}
@@ -955,7 +1042,7 @@
#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
move_assignment) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
move_assignable_trait> \
: public __assignment<__traits<_Types...>> { \
using __base_type = __assignment<__traits<_Types...>>; \
@@ -996,7 +1083,7 @@
#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
copy_assignment) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
copy_assignable_trait> \
: public __move_assignment<__traits<_Types...>> { \
using __base_type = __move_assignment<__traits<_Types...>>; \
@@ -1590,18 +1677,12 @@
__lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
}
-template <class _Visitor, class... _Vs>
+template <class _Vis, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
-constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
+constexpr decltype(auto) visit(_Vis&& __vis, _Vs&&... __vs) {
using __variant_detail::__visitation::__variant;
- bool __results[] = {__vs.valueless_by_exception()...};
- for (bool __result : __results) {
- if (__result) {
- __throw_bad_variant_access();
- }
- }
- return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
+ return __variant::__visit_value(_VSTD::forward<_Vis>(__vis),
_VSTD::forward<_Vs>(__vs)...);
}
diff --git a/test/std/utilities/variant/variant.visit/visit.pass.cpp b/test/std/utilities/variant/variant.visit/visit.pass.cpp
index 41ce442..fc03407 100644
--- a/test/std/utilities/variant/variant.visit/visit.pass.cpp
+++ b/test/std/utilities/variant/variant.visit/visit.pass.cpp
@@ -140,6 +140,30 @@
std::visit(std::move(cobj), v, v2);
assert((Fn::check_call<long &, std::string &>(CT_Const | CT_RValue)));
}
+ {
+ using V = std::variant<int, long, double, std::string>;
+ V v1(42l), v2("hello"), v3(101), v4(1.1);
+ std::visit(obj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int &, double &>(CT_NonConst | CT_LValue)));
+ std::visit(cobj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int &, double &>(CT_Const | CT_LValue)));
+ std::visit(std::move(obj), v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int &, double &>(CT_NonConst | CT_RValue)));
+ std::visit(std::move(cobj), v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int &, double &>(CT_Const | CT_RValue)));
+ }
+ {
+ using V = std::variant<int, long, double, int*, std::string>;
+ V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
+ std::visit(obj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_NonConst | CT_LValue)));
+ std::visit(cobj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_Const | CT_LValue)));
+ std::visit(std::move(obj), v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_NonConst | CT_RValue)));
+ std::visit(std::move(cobj), v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_Const | CT_RValue)));
+ }
}
void test_argument_forwarding() {
@@ -188,23 +212,31 @@
std::visit(obj, std::move(cv));
assert(Fn::check_call<int &&>(Val));
}
- { // multi argument - multi variant
- using S = const std::string &;
- using V = std::variant<int, S, long &&>;
- const std::string str = "hello";
- long l = 43;
- V v1(42);
- const V &cv1 = v1;
- V v2(str);
- const V &cv2 = v2;
- V v3(std::move(l));
- const V &cv3 = v3;
- std::visit(obj, v1, v2, v3);
- assert((Fn::check_call<int &, S, long &>(Val)));
- std::visit(obj, cv1, cv2, std::move(v3));
- assert((Fn::check_call<const int &, S, long &&>(Val)));
- }
#endif
+ { // multi argument - multi variant
+ using V = std::variant<int, std::string, long>;
+ V v1(42), v2("hello"), v3(43l);
+ std::visit(obj, v1, v2, v3);
+ assert((Fn::check_call<int &, std::string &, long &>(Val)));
+ std::visit(obj, std::as_const(v1), std::as_const(v2), std::move(v3));
+ assert((Fn::check_call<const int &, const std::string &, long &&>(Val)));
+ }
+ {
+ using V = std::variant<int, long, double, std::string>;
+ V v1(42l), v2("hello"), v3(101), v4(1.1);
+ std::visit(obj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int &, double &>(Val)));
+ std::visit(obj, std::as_const(v1), std::as_const(v2), std::move(v3), std::move(v4));
+ assert((Fn::check_call<const long &, const std::string &, int &&, double &&>(Val)));
+ }
+ {
+ using V = std::variant<int, long, double, int*, std::string>;
+ V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
+ std::visit(obj, v1, v2, v3, v4);
+ assert((Fn::check_call<long &, std::string &, int *&, double &>(Val)));
+ std::visit(obj, std::as_const(v1), std::as_const(v2), std::move(v3), std::move(v4));
+ assert((Fn::check_call<const long &, const std::string &, int *&&, double &&>(Val)));
+ }
}
struct ReturnFirst {
@@ -250,6 +282,16 @@
constexpr V3 v3;
static_assert(std::visit(aobj, v1, v2, v3) == 3, "");
}
+ {
+ using V = std::variant<int, long, double, int *>;
+ constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
+ static_assert(std::visit(aobj, v1, v2, v3, v4) == 4, "");
+ }
+ {
+ using V = std::variant<int, long, double, long long, int *>;
+ constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
+ static_assert(std::visit(aobj, v1, v2, v3, v4) == 4, "");
+ }
}
void test_exceptions() {
@@ -295,6 +337,21 @@
makeEmpty(v2);
assert(test(v, v2));
}
+ {
+ using V = std::variant<int, long, double, MakeEmptyT>;
+ V v1(42l), v2(101), v3(202), v4(1.1);
+ makeEmpty(v1);
+ assert(test(v1, v2, v3, v4));
+ }
+ {
+ using V = std::variant<int, long, double, long long, MakeEmptyT>;
+ V v1(42l), v2(101), v3(202), v4(1.1);
+ makeEmpty(v1);
+ makeEmpty(v2);
+ makeEmpty(v3);
+ makeEmpty(v4);
+ assert(test(v1, v2, v3, v4));
+ }
#endif
}
