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Promote internal _Countl_zero to __msvc_bit_utils.hpp to reduce code duplication and improve consistency #5696

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Merged
merged 3 commits into from
Sep 10, 2025
Merged

Promote internal _Countl_zero to __msvc_bit_utils.hpp to reduce code duplication and improve consistency #5696

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d56be5a
Promote internal _Countl_zero to bit utils header
AlexGuteniev Aug 26, 2025
5ee1785
Merge branch 'main' into contr_zero_consistency
StephanTLavavej Sep 10, 2025
1c89eb5
Fix stealth merge conflict: _Countl_zero_internal => _Countl_zero
StephanTLavavej Sep 10, 2025
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18 changes: 18 additions & 0 deletions stl/inc/__msvc_bit_utils.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -352,6 +352,24 @@ constexpr decltype(auto) _Select_countr_zero_impl(_Fn _Callback) {
return _Callback([](_Ty _Val) _STATIC_LAMBDA { return _Countr_zero_fallback(_Val); });
}

template <class _Ty>
_NODISCARD constexpr int _Countl_zero(const _Ty _Val) noexcept {
_STL_INTERNAL_STATIC_ASSERT(_Is_standard_unsigned_integer<_Ty>);
#if _HAS_COUNTL_ZERO_INTRINSICS
#if (defined(_M_IX86) && !defined(_M_HYBRID_X86_ARM64)) || (defined(_M_X64) && !defined(_M_ARM64EC))
if (!_Is_constant_evaluated()) {
return _Checked_x86_x64_countl_zero(_Val);
}
#elif defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
if (!_Is_constant_evaluated()) {
return _Checked_arm64_countl_zero(_Val);
}
#endif // defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
#endif // _HAS_COUNTL_ZERO_INTRINSICS

return _Countl_zero_fallback(_Val);
}

template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> = 0>
_NODISCARD _CONSTEXPR20 int _Popcount(const _Ty _Val) noexcept {
#if _HAS_POPCNT_INTRINSICS
Expand Down
28 changes: 5 additions & 23 deletions stl/inc/__msvc_int128.hpp
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Expand Up @@ -48,24 +48,6 @@ _STD_BEGIN
#define _STL_128_DIV_INTRINSICS 0
#endif // ^^^ intrinsics unavailable ^^^

template <class _Ty>
_NODISCARD constexpr int _Countl_zero_internal(const _Ty _Val) noexcept {
_STL_INTERNAL_STATIC_ASSERT(_Is_standard_unsigned_integer<_Ty>);
#if _HAS_COUNTL_ZERO_INTRINSICS
#if (defined(_M_IX86) && !defined(_M_HYBRID_X86_ARM64)) || (defined(_M_X64) && !defined(_M_ARM64EC))
if (!_Is_constant_evaluated()) {
return _Checked_x86_x64_countl_zero(_Val);
}
#elif defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
if (!_Is_constant_evaluated()) {
return _Checked_arm64_countl_zero(_Val);
}
#endif // defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
#endif // _HAS_COUNTL_ZERO_INTRINSICS

return _Countl_zero_fallback(_Val);
}

struct alignas(16) _Base128 {
uint64_t _Word[2];

Expand Down Expand Up @@ -258,7 +240,7 @@ struct alignas(16) _Base128 {
}
#endif // _STL_128_DIV_INTRINSICS

const auto __d = _Countl_zero_internal(static_cast<uint32_t>(_Div >> 32));
const auto __d = _Countl_zero(static_cast<uint32_t>(_Div >> 32));
if (__d >= 32) { // _Div < 2^32
auto _Rem = (_High << 32) | (_Low >> 32);
auto _Result = _Rem / static_cast<uint32_t>(_Div);
Expand Down Expand Up @@ -466,7 +448,7 @@ struct alignas(16) _Base128 {
// _STL_INTERNAL_CHECK(_Den._Word[1] != 0);
// _STL_INTERNAL_CHECK(_Num._Word[1] > _Den._Word[1]);
// Normalize by shifting both left until _Den's high bit is set (So _Den's high digit is >= b / 2)
const auto __d = _Countl_zero_internal(_Den._Word[1]);
const auto __d = _Countl_zero(_Den._Word[1]);
_Den <<= __d;
auto _High_digit = __d == 0 ? 0 : _Num._Word[1] >> (64 - __d); // This creates a third digit for _Num
_Num <<= __d;
Expand Down Expand Up @@ -511,7 +493,7 @@ struct alignas(16) _Base128 {
}
return __qhat;
#else // ^^^ 128-bit intrinsics / no such intrinsics vvv
auto __d = _Countl_zero_internal(_Den._Word[1]);
auto __d = _Countl_zero(_Den._Word[1]);
const bool _Three_word_den = __d >= 32;
__d &= 31;
uint32_t __u[5]{
Expand Down Expand Up @@ -591,7 +573,7 @@ struct alignas(16) _Base128 {
// _STL_INTERNAL_CHECK(_Den._Word[1] != 0);
// _STL_INTERNAL_CHECK(_Num._Word[1] > _Den._Word[1]);
// Normalize by shifting both left until _Den's high bit is set (So _Den's high digit is >= b / 2)
const auto __d = _Countl_zero_internal(_Den._Word[1]);
const auto __d = _Countl_zero(_Den._Word[1]);
_Den <<= __d;
auto _High_digit = __d == 0 ? 0 : _Num._Word[1] >> (64 - __d); // This creates a third digit for _Num
_Num <<= __d;
Expand Down Expand Up @@ -638,7 +620,7 @@ struct alignas(16) _Base128 {
(void) _AddCarry64(_Carry, _Num._Word[1], _Den._Word[1], _Num._Word[1]);
}
#else // ^^^ 128-bit intrinsics / no such intrinsics vvv
auto __d = _Countl_zero_internal(_Den._Word[1]);
auto __d = _Countl_zero(_Den._Word[1]);
const bool _Three_word_den = __d >= 32;
__d &= 31;
uint32_t __u[5]{
Expand Down
16 changes: 2 additions & 14 deletions stl/inc/bit
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Expand Up @@ -198,24 +198,12 @@ _NODISCARD constexpr _Ty rotr(const _Ty _Val, const int _Rotation) noexcept {

_EXPORT_STD template <_Standard_unsigned_integral _Ty>
_NODISCARD constexpr int countl_zero(const _Ty _Val) noexcept {
#if _HAS_COUNTL_ZERO_INTRINSICS
#if (defined(_M_IX86) && !defined(_M_HYBRID_X86_ARM64)) || (defined(_M_X64) && !defined(_M_ARM64EC))
if (!_STD is_constant_evaluated()) {
return _Checked_x86_x64_countl_zero(_Val);
}
#elif defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
if (!_STD is_constant_evaluated()) {
return _Checked_arm64_countl_zero(_Val);
}
#endif // defined(_M_ARM64) || defined(_M_ARM64EC) || defined(_M_HYBRID_X86_ARM64)
#endif // _HAS_COUNTL_ZERO_INTRINSICS

return _Countl_zero_fallback(_Val);
return _Countl_zero(_Val);
}

_EXPORT_STD template <_Standard_unsigned_integral _Ty>
_NODISCARD constexpr int countl_one(const _Ty _Val) noexcept {
return _STD countl_zero(static_cast<_Ty>(~_Val));
return _Countl_zero(static_cast<_Ty>(~_Val));
}

_EXPORT_STD template <_Standard_unsigned_integral _Ty>
Expand Down
2 changes: 1 addition & 1 deletion stl/inc/random
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Expand Up @@ -2583,7 +2583,7 @@ _NODISCARD _Flt _Float_upper_bound(_Ty _Val) noexcept {
constexpr auto _Mask = static_cast<_Ty>(-1) << (_Ty_digits - _Flt_digits);
#ifdef _M_CEE_PURE
constexpr auto _Ty_32or64_digits = numeric_limits<_Ty_32or64>::digits;
const auto _Log_plus1 = _Ty_32or64_digits - _Countl_zero_internal(static_cast<_Ty_32or64>(_Val | _Ty{1}));
const auto _Log_plus1 = _Ty_32or64_digits - _Countl_zero(static_cast<_Ty_32or64>(_Val | _Ty{1}));
#else // ^^^ defined(_M_CEE_PURE) / !defined(_M_CEE_PURE) vvv
const auto _Log_plus1 = _Bit_scan_reverse(static_cast<_Ty_32or64>(_Val | _Ty{1}));
#endif // ^^^ !defined(_M_CEE_PURE) ^^^
Expand Down