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Enable vectorized minmax_element using Neon on ARM64 #5949

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Merged
StephanTLavavej merged 20 commits into from
Jan 8, 2026
Merged

Enable vectorized minmax_element using Neon on ARM64 #5949

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e9ad403
Enable vectorized minmax_element using Neon on ARM64
hazzlim Dec 5, 2025
2329cc4
Roll into _Is_min_max_optimization_safe
hazzlim Dec 9, 2025
58f953b
Don't const-qualify unnamed parameter
hazzlim Dec 9, 2025
9b849a3
Don't define minmax,is_sorted_until on ARM64 for now
hazzlim Dec 9, 2025
b3cd60c
Remove _Traits_8_neon and don't define *_8 functions
hazzlim Dec 9, 2025
05f1ee9
Use non-floating point types where necessary in _Traits_d_neon
hazzlim Dec 9, 2025
1f1ee32
Unify _Get_v_pos interface
hazzlim Dec 9, 2025
3a0a371
Use _tzcnt_u32/_lzcnt_u32 on avx
hazzlim Dec 9, 2025
0b93055
Don't declare _8 functions
hazzlim Dec 9, 2025
017caa1
Add missing const qualifiers
hazzlim Dec 10, 2025
f995cbc
Don't add dispatch for minmax,is_sorted_until for now
hazzlim Dec 10, 2025
d139232
Merge branch 'main' into minmax-element-pr
StephanTLavavej Jan 6, 2026
cce3375
Cleanup handling of 64-bit integers on ARM64.
StephanTLavavej Jan 6, 2026
61327c0
`_Get_first_h_pos()`, `_Get_last_h_pos()`: const params, noexcept.
StephanTLavavej Jan 6, 2026
460655f
Drop `const` for template param `bool _Sign`.
StephanTLavavej Jan 6, 2026
a889815
Uglify: `m` => `_Mx`, `M` => `_Mx`, `r` => `_Rx`
StephanTLavavej Jan 6, 2026
bd21ec9
Fix preprocessor comments.
StephanTLavavej Jan 6, 2026
981bb91
Chain together ARM64 and ARM64EC preprocessor conditionals.
StephanTLavavej Jan 6, 2026
8051595
(Pre-existing) Chain together ARM64 and ARM64EC preprocessor conditio…
StephanTLavavej Jan 6, 2026
3893d1b
Don't modify `_Minmax_impl` to inspect `_Traits::_Has_unsigned_cmp` yet.
StephanTLavavej Jan 6, 2026
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6 changes: 6 additions & 0 deletions stl/inc/algorithm
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,9 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_8(
_Min_max_element_t __stdcall __std_minmax_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
_Min_max_element_t __stdcall __std_minmax_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
_Min_max_element_t __stdcall __std_minmax_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
#ifndef _M_ARM64
_Min_max_element_t __stdcall __std_minmax_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
#endif // ^^^ !defined(_M_ARM64) ^^^
_Min_max_element_t __stdcall __std_minmax_element_f(const void* _First, const void* _Last, bool _Unused) noexcept;
_Min_max_element_t __stdcall __std_minmax_element_d(const void* _First, const void* _Last, bool _Unused) noexcept;
#endif // ^^^ _VECTORIZED_MINMAX_ELEMENT ^^^
Expand Down Expand Up @@ -212,7 +214,11 @@ pair<_Ty*, _Ty*> _Minmax_element_vectorized(_Ty* const _First, _Ty* const _Last)
} else if constexpr (sizeof(_Ty) == 4) {
_Res = ::__std_minmax_element_4(_First, _Last, _Signed);
} else if constexpr (sizeof(_Ty) == 8) {
#ifdef _M_ARM64
static_assert(false, "unexpected size; 64-bit integers on ARM64 should not take this codepath");
#else // ^^^ defined(_M_ARM64) / !defined(_M_ARM64) vvv
_Res = ::__std_minmax_element_8(_First, _Last, _Signed);
#endif // ^^^ !defined(_M_ARM64) ^^^
} else {
static_assert(false, "unexpected size");
}
Expand Down
27 changes: 25 additions & 2 deletions stl/inc/xutility
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ _STL_DISABLE_CLANG_WARNINGS
#define _VECTORIZED_INCLUDES _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_IS_SORTED_UNTIL _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_MINMAX _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_MINMAX_ELEMENT _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_MINMAX_ELEMENT _VECTORIZED_FOR_X64_X86_ARM64
#define _VECTORIZED_MISMATCH _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_REMOVE _VECTORIZED_FOR_X64_X86
#define _VECTORIZED_REMOVE_COPY _VECTORIZED_FOR_X64_X86
Expand Down Expand Up @@ -207,14 +207,18 @@ const void* __stdcall __std_find_end_8(
const void* __stdcall __std_min_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
const void* __stdcall __std_min_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
const void* __stdcall __std_min_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
#ifndef _M_ARM64
const void* __stdcall __std_min_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
#endif // ^^^ !defined(_M_ARM64) ^^^
const void* __stdcall __std_min_element_f(const void* _First, const void* _Last, bool _Unused) noexcept;
const void* __stdcall __std_min_element_d(const void* _First, const void* _Last, bool _Unused) noexcept;

const void* __stdcall __std_max_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
const void* __stdcall __std_max_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
const void* __stdcall __std_max_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
#ifndef _M_ARM64
const void* __stdcall __std_max_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
#endif // ^^^ !defined(_M_ARM64) ^^^
const void* __stdcall __std_max_element_f(const void* _First, const void* _Last, bool _Unused) noexcept;
const void* __stdcall __std_max_element_d(const void* _First, const void* _Last, bool _Unused) noexcept;
#endif // ^^^ _VECTORIZED_MINMAX_ELEMENT ^^^
Expand Down Expand Up @@ -416,7 +420,11 @@ _Ty* _Min_element_vectorized(_Ty* const _First, _Ty* const _Last) noexcept {
} else if constexpr (sizeof(_Ty) == 4) {
return const_cast<_Ty*>(static_cast<const _Ty*>(::__std_min_element_4(_First, _Last, _Signed)));
} else if constexpr (sizeof(_Ty) == 8) {
#ifdef _M_ARM64
static_assert(false, "unexpected size; 64-bit integers on ARM64 should not take this codepath");
#else // ^^^ defined(_M_ARM64) / !defined(_M_ARM64) vvv
return const_cast<_Ty*>(static_cast<const _Ty*>(::__std_min_element_8(_First, _Last, _Signed)));
#endif // ^^^ !defined(_M_ARM64) ^^^
} else {
static_assert(false, "unexpected size");
}
Expand All @@ -437,7 +445,11 @@ _Ty* _Max_element_vectorized(_Ty* const _First, _Ty* const _Last) noexcept {
} else if constexpr (sizeof(_Ty) == 4) {
return const_cast<_Ty*>(static_cast<const _Ty*>(::__std_max_element_4(_First, _Last, _Signed)));
} else if constexpr (sizeof(_Ty) == 8) {
#ifdef _M_ARM64
static_assert(false, "unexpected size; 64-bit integers on ARM64 should not take this codepath");
#else // ^^^ defined(_M_ARM64) / !defined(_M_ARM64) vvv
return const_cast<_Ty*>(static_cast<const _Ty*>(::__std_max_element_8(_First, _Last, _Signed)));
#endif // ^^^ !defined(_M_ARM64) ^^^
} else {
static_assert(false, "unexpected size");
}
Expand Down Expand Up @@ -7281,9 +7293,20 @@ constexpr bool _Is_predicate_greater = _Is_any_of_v<_Pr,
#endif // _HAS_CXX20
greater<>, greater<_Iter_value_t<_Iter>>>;

#ifdef _M_ARM64
// We choose not to vectorize minmax_element for 64-bit integers on ARM64
// as this does not improve performance over the scalar code.
template <class _Ty>
_INLINE_VAR constexpr bool _Is_64bit_int_on_arm64_v = sizeof(_Ty) == 8 && !is_floating_point_v<_Ty>;
#else // ^^^ defined(_M_ARM64) / !defined(_M_ARM64) vvv
template <class _Ty>
_INLINE_VAR constexpr bool _Is_64bit_int_on_arm64_v = false;
#endif // ^^^ !defined(_M_ARM64) ^^^

template <class _Iter, class _Pr>
constexpr bool _Is_min_max_optimization_safe = // Activate the vector algorithms for min_/max_element?
_Is_min_max_iterators_safe<_Iter> && _Is_predicate_less<_Iter, _Pr>;
_Is_min_max_iterators_safe<_Iter> && _Is_predicate_less<_Iter, _Pr>
&& !_Is_64bit_int_on_arm64_v<_Iter_value_t<_Iter>>;

// Unlike the position-based vectorized implementation, the value-based vectorized implementation
// does not always produce the expected results for floating-point types.
Expand Down
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