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| author | Jonathan Wakely <jwakely@redhat.com> | 2021-04-17 22:34:09 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2021-10-01 20:34:46 +0100 |
| commit | 741c7350c08b0884689466867b6c9e711c7b109e (patch) | |
| tree | 1b0c1a73481bc0fb4cabbed8d3d5ad96bbe8d35d | |
| parent | 2a93d18da3bd79eb0be87f029eefc8b28bb66dec (diff) | |
| download | gcc-741c7350c08b0884689466867b6c9e711c7b109e.zip gcc-741c7350c08b0884689466867b6c9e711c7b109e.tar.gz gcc-741c7350c08b0884689466867b6c9e711c7b109e.tar.bz2 | |
libstdc++: Implement std::clamp with std::min and std::max [PR 96733]
The compiler doesn't know about the precondition of std::clamp that
(hi < lo) is false, and so can't optimize as well as we'd like. By using
std::min and std::max we help the compiler.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/96733
* include/bits/stl_algo.h (clamp): Use std::min and std::max.
| -rw-r--r-- | libstdc++-v3/include/bits/stl_algo.h | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h index 5d12972..90f3162 100644 --- a/libstdc++-v3/include/bits/stl_algo.h +++ b/libstdc++-v3/include/bits/stl_algo.h @@ -3621,7 +3621,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __gnu_cxx::__ops::__iter_comp_iter(__pred)); } -#if __cplusplus > 201402L +#if __cplusplus >= 201703L #define __cpp_lib_clamp 201603 @@ -3631,14 +3631,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * @param __val A value of arbitrary type. * @param __lo A lower limit of arbitrary type. * @param __hi An upper limit of arbitrary type. - * @return max(__val, __lo) if __val < __hi or min(__val, __hi) otherwise. + * @retval `__lo` if `__val < __lo` + * @retval `__hi` if `__hi < __val` + * @retval `__val` otherwise. + * @pre `_Tp` is LessThanComparable and `(__hi < __lo)` is false. */ template<typename _Tp> constexpr const _Tp& clamp(const _Tp& __val, const _Tp& __lo, const _Tp& __hi) { __glibcxx_assert(!(__hi < __lo)); - return (__val < __lo) ? __lo : (__hi < __val) ? __hi : __val; + return std::min(std::max(__val, __lo), __hi); } /** @@ -3648,15 +3651,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * @param __lo A lower limit of arbitrary type. * @param __hi An upper limit of arbitrary type. * @param __comp A comparison functor. - * @return max(__val, __lo, __comp) if __comp(__val, __hi) - * or min(__val, __hi, __comp) otherwise. + * @retval `__lo` if `__comp(__val, __lo)` + * @retval `__hi` if `__comp(__hi, __val)` + * @retval `__val` otherwise. + * @pre `__comp(__hi, __lo)` is false. */ template<typename _Tp, typename _Compare> constexpr const _Tp& clamp(const _Tp& __val, const _Tp& __lo, const _Tp& __hi, _Compare __comp) { __glibcxx_assert(!__comp(__hi, __lo)); - return __comp(__val, __lo) ? __lo : __comp(__hi, __val) ? __hi : __val; + return std::min(std::max(__val, __lo, __comp), __hi, __comp); } #endif // C++17 #endif // C++14 |