Enable __builtin_bit_cast for CUDA (#3066)

Author: StephanTLavavej

stl/inc/complex

@@ -133,7 +133,7 @@ namespace _Float_multi_prec {
     // multiplication
 
     // round to 26 significant bits, ties toward zero
-    _NODISCARD _CONSTEXPR_BIT_CAST double _High_half(const double _Val) noexcept {
+    _NODISCARD constexpr double _High_half(const double _Val) noexcept {
         const auto _Bits           = _Bit_cast<unsigned long long>(_Val);
         const auto _High_half_bits = (_Bits + 0x3ff'ffffULL) & 0xffff'ffff'f800'0000ULL;
         return _Bit_cast<double>(_High_half_bits);
@@ -144,7 +144,7 @@ namespace _Float_multi_prec {
     // 1) _Prod0 is _Xval^2 faithfully rounded
     // 2) no internal overflow or underflow occurs
     // violation of condition 1 could lead to relative error on the order of epsilon
-    _NODISCARD _CONSTEXPR_BIT_CAST double _Sqr_error_fallback(const double _Xval, const double _Prod0) noexcept {
+    _NODISCARD constexpr double _Sqr_error_fallback(const double _Xval, const double _Prod0) noexcept {
         const double _Xhigh = _High_half(_Xval);
         const double _Xlow  = _Xval - _Xhigh;
         return ((_Xhigh * _Xhigh - _Prod0) + 2.0 * _Xhigh * _Xlow) + _Xlow * _Xlow;

stl/inc/xutility

@@ -43,12 +43,6 @@ _STL_DISABLE_CLANG_WARNINGS
 #endif // _USE_STD_VECTOR_ALGORITHMS
 #endif // ^^^ no support for vector algorithms ^^^
 
-#ifdef __CUDACC__
-#define _CONSTEXPR_BIT_CAST inline
-#else // ^^^ workaround ^^^ / vvv no workaround vvv
-#define _CONSTEXPR_BIT_CAST constexpr
-#endif // ^^^ no workaround ^^^
-
 #if _USE_STD_VECTOR_ALGORITHMS
 _EXTERN_C
 // The "noalias" attribute tells the compiler optimizer that pointers going into these hand-vectorized algorithms
@@ -152,14 +146,8 @@ template <class _To, class _From,
     enable_if_t<conjunction_v<bool_constant<sizeof(_To) == sizeof(_From)>, is_trivially_copyable<_To>,
                     is_trivially_copyable<_From>>,
         int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST _To _Bit_cast(const _From& _Val) noexcept {
-#ifdef __CUDACC__
-    _To _To_obj; // assumes default-init
-    _CSTD memcpy(_STD addressof(_To_obj), _STD addressof(_Val), sizeof(_To));
-    return _To_obj;
-#else // ^^^ workaround ^^^ / vvv no workaround vvv
+_NODISCARD constexpr _To _Bit_cast(const _From& _Val) noexcept {
     return __builtin_bit_cast(_To, _Val);
-#endif // ^^^ no workaround ^^^
 }
 
 template <class _Ty>
@@ -5114,7 +5102,7 @@ _NODISCARD _CONSTEXPR20 _InIt _Find_unchecked(_InIt _First, const _InIt _Last, c
 #else // ^^^ _USE_STD_VECTOR_ALGORITHMS ^^^ / vvv not _USE_STD_VECTOR_ALGORITHMS vvv
             if constexpr (sizeof(_Iter_value_t<_InIt>) == 1) {
                 const auto _First_ptr = _To_address(_First);
-                const auto _Result = static_cast<remove_reference_t<_Iter_ref_t<_InIt>>*>(
+                const auto _Result    = static_cast<remove_reference_t<_Iter_ref_t<_InIt>>*>(
                     _CSTD memchr(_First_ptr, static_cast<unsigned char>(_Val), static_cast<size_t>(_Last - _First)));
                 if constexpr (is_pointer_v<_InIt>) {
                     return _Result ? _Result : _Last;
@@ -6100,28 +6088,28 @@ struct _CXX17_DEPRECATE_ITERATOR_BASE_CLASS iterator { // base type for iterator
 };
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST auto _Float_abs_bits(const _Ty& _Xx) {
+_NODISCARD constexpr auto _Float_abs_bits(const _Ty& _Xx) {
     using _Traits    = _Floating_type_traits<_Ty>;
     using _Uint_type = typename _Traits::_Uint_type;
     const auto _Bits = _Bit_cast<_Uint_type>(_Xx);
     return _Bits & ~_Traits::_Shifted_sign_mask;
 }
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST _Ty _Float_abs(const _Ty _Xx) { // constexpr floating-point abs()
+_NODISCARD constexpr _Ty _Float_abs(const _Ty _Xx) { // constexpr floating-point abs()
     return _Bit_cast<_Ty>(_Float_abs_bits(_Xx));
 }
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST _Ty _Float_copysign(const _Ty _Magnitude, const _Ty _Sign) { // constexpr copysign()
+_NODISCARD constexpr _Ty _Float_copysign(const _Ty _Magnitude, const _Ty _Sign) { // constexpr copysign()
     using _Traits       = _Floating_type_traits<_Ty>;
     using _Uint_type    = typename _Traits::_Uint_type;
     const auto _Signbit = _Bit_cast<_Uint_type>(_Sign) & _Traits::_Shifted_sign_mask;
     return _Bit_cast<_Ty>(_Float_abs_bits(_Magnitude) | _Signbit);
 }
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST bool _Is_nan(const _Ty _Xx) { // constexpr isnan()
+_NODISCARD constexpr bool _Is_nan(const _Ty _Xx) { // constexpr isnan()
     using _Traits = _Floating_type_traits<_Ty>;
     return _Float_abs_bits(_Xx) > _Traits::_Shifted_exponent_mask;
 }
@@ -6131,20 +6119,20 @@ _NODISCARD _CONSTEXPR_BIT_CAST bool _Is_nan(const _Ty _Xx) { // constexpr isnan(
 // When the value is a 32-bit or 64-bit signaling NaN, the conversion to/from 80-bit raises FE_INVALID
 // and turns it into a quiet NaN. This behavior is undesirable if we want to test for signaling NaNs.
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST bool _Is_signaling_nan(const _Ty& _Xx) { // returns true if input is a signaling NaN
+_NODISCARD constexpr bool _Is_signaling_nan(const _Ty& _Xx) { // returns true if input is a signaling NaN
     using _Traits        = _Floating_type_traits<_Ty>;
     const auto _Abs_bits = _Float_abs_bits(_Xx);
     return _Abs_bits > _Traits::_Shifted_exponent_mask && ((_Abs_bits & _Traits::_Special_nan_mantissa_mask) == 0);
 }
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST bool _Is_inf(const _Ty _Xx) { // constexpr isinf()
+_NODISCARD constexpr bool _Is_inf(const _Ty _Xx) { // constexpr isinf()
     using _Traits = _Floating_type_traits<_Ty>;
     return _Float_abs_bits(_Xx) == _Traits::_Shifted_exponent_mask;
 }
 
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
-_NODISCARD _CONSTEXPR_BIT_CAST bool _Is_finite(const _Ty _Xx) { // constexpr isfinite()
+_NODISCARD constexpr bool _Is_finite(const _Ty _Xx) { // constexpr isfinite()
     using _Traits = _Floating_type_traits<_Ty>;
     return _Float_abs_bits(_Xx) < _Traits::_Shifted_exponent_mask;
 }