Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
-- >8 --
By now it's probably safe to assume supported compilers have full
concepts support in C++20 mode. And using a requires-clase instead
enable_if_t inside the return type greatly reduces the sizes of the
corresponding symbol names.
libstdc++-v3/ChangeLog:
* include/std/bit: Include <concepts>.
(byteswap): Use a requires-clause instead of enable_if_t
inside the return type.
(_If_is_unsigned_integer): Replace with ...
(__unsigned_integer): ... this.
(rotl): Use a requires-clause instead of enable_if_t
inside the return type.
(countl_zero): Likewise.
(countl_one): Likewise.
(countr_zero): Likewise.
(countr_one): Likewise.
(popcount): Likewise.
(has_single_bit): Likewise.
(bit_ceil): Likewise.
(bit_floor): Likewise.
(bit_width): Likewise.
---
libstdc++-v3/include/std/bit | 54 ++++++++++++++++++------------------
1 file changed, 27 insertions(+), 27 deletions(-)
diff --git a/libstdc++-v3/include/std/bit b/libstdc++-v3/include/std/bit
index 987b6cdbb35..dce61b440c5 100644
--- a/libstdc++-v3/include/std/bit
+++ b/libstdc++-v3/include/std/bit
@@ -33,6 +33,7 @@
#if __cplusplus >= 201402L
+#include <concepts> // for std::integral
#include <type_traits>
#if _GLIBCXX_HOSTED || __has_include(<ext/numeric_traits.h>)
@@ -103,9 +104,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @return An object of the same type, with the bytes reversed.
* @since C++23
*/
- template<typename _Tp>
+ template<integral _Tp>
[[nodiscard]]
- constexpr enable_if_t<is_integral<_Tp>::value, _Tp>
+ constexpr _Tp
byteswap(_Tp __value) noexcept
{
if constexpr (sizeof(_Tp) == 1)
@@ -378,54 +379,53 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef __cpp_lib_bitops // C++ >= 20
/// @cond undocumented
- template<typename _Tp, typename _Up = _Tp>
- using _If_is_unsigned_integer
- = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
+ template<typename _Tp>
+ concept __unsigned_integer = __is_unsigned_integer<_Tp>::value;
/// @endcond
// [bit.rot], rotating
/// Rotate `x` to the left by `s` bits.
- template<typename _Tp>
- [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
+ template<__unsigned_integer _Tp>
+ [[nodiscard]] constexpr _Tp
rotl(_Tp __x, int __s) noexcept
{ return std::__rotl(__x, __s); }
/// Rotate `x` to the right by `s` bits.
- template<typename _Tp>
- [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
+ template<__unsigned_integer _Tp>
+ [[nodiscard]] constexpr _Tp
rotr(_Tp __x, int __s) noexcept
{ return std::__rotr(__x, __s); }
// [bit.count], counting
/// The number of contiguous zero bits, starting from the highest bit.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
countl_zero(_Tp __x) noexcept
{ return std::__countl_zero(__x); }
/// The number of contiguous one bits, starting from the highest bit.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
countl_one(_Tp __x) noexcept
{ return std::__countl_one(__x); }
/// The number of contiguous zero bits, starting from the lowest bit.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
countr_zero(_Tp __x) noexcept
{ return std::__countr_zero(__x); }
/// The number of contiguous one bits, starting from the lowest bit.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
countr_one(_Tp __x) noexcept
{ return std::__countr_one(__x); }
/// The number of bits set in `x`.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
popcount(_Tp __x) noexcept
{ return std::__popcount(__x); }
#endif // __cpp_lib_bitops
@@ -434,28 +434,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// [bit.pow.two], integral powers of 2
/// True if `x` is a power of two, false otherwise.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, bool>
+ template<__unsigned_integer _Tp>
+ constexpr bool
has_single_bit(_Tp __x) noexcept
{ return std::__has_single_bit(__x); }
/// The smallest power-of-two not less than `x`.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp>
+ template<__unsigned_integer _Tp>
+ constexpr _Tp
bit_ceil(_Tp __x) noexcept
{ return std::__bit_ceil(__x); }
/// The largest power-of-two not greater than `x`.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp>
+ template<__unsigned_integer _Tp>
+ constexpr _Tp
bit_floor(_Tp __x) noexcept
{ return std::__bit_floor(__x); }
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3656. Inconsistent bit operations returning a count
/// The smallest integer greater than the base-2 logarithm of `x`.
- template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp, int>
+ template<__unsigned_integer _Tp>
+ constexpr int
bit_width(_Tp __x) noexcept
{ return std::__bit_width(__x); }
#endif // defined (__cpp_lib_int_pow2)
--
2.42.0.158.g94e83dcf5b
