EricWF updated this revision to Diff 217700. EricWF added a comment. Address review comments. I think this is good to go.
CHANGES SINCE LAST ACTION https://reviews.llvm.org/D66836/new/ https://reviews.llvm.org/D66836 Files: include/math.h test/libcxx/numerics/clamp_to_integral.pass.cpp
Index: test/libcxx/numerics/clamp_to_integral.pass.cpp =================================================================== --- /dev/null +++ test/libcxx/numerics/clamp_to_integral.pass.cpp @@ -0,0 +1,57 @@ +//===----------------------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +// __clamp_to_integral<IntT>(RealT) + +// Test the conversion function that truncates floating point types to the +// closes representable value for the specified integer type, or +// numeric_limits<IntT>::max()/min() if the value isn't representable. + +#include <limits> +#include <cassert> +#include <cmath> + +template <class IntT> +void test() { + typedef std::numeric_limits<IntT> Lim; + const bool MaxIsRepresentable = sizeof(IntT) < 8; + const bool IsSigned = std::is_signed<IntT>::value; + struct TestCase { + double Input; + IntT Expect; + bool IsRepresentable; + } TestCases[] = { + {0, 0, true}, + {1, 1, true}, + {IsSigned ? static_cast<IntT>(-1) : 0, + IsSigned ? static_cast<IntT>(-1) : 0, true}, + {Lim::lowest(), Lim::lowest(), true}, + {static_cast<double>(Lim::max()), Lim::max(), MaxIsRepresentable}, + {static_cast<double>(Lim::max()) + 1, Lim::max(), false}, + {static_cast<double>(Lim::max()) + 1024, Lim::max(), false}, + {nextafter(static_cast<double>(Lim::max()), INFINITY), Lim::max(), false}, + }; + for (TestCase TC : TestCases) { + auto res = std::__clamp_to_integral<IntT>(TC.Input); + assert(res == TC.Expect); + if (TC.IsRepresentable) { + auto other = static_cast<IntT>(std::trunc(TC.Input)); + assert(res == other); + } else + assert(res == Lim::min() || res == Lim::max()); + } +} + +int main() { + test<short>(); + test<unsigned short>(); + test<int>(); + test<unsigned>(); + test<long long>(); + test<unsigned long long>(); +} Index: include/math.h =================================================================== --- include/math.h +++ include/math.h @@ -1553,6 +1553,48 @@ typename std::enable_if<std::is_integral<_A1>::value, double>::type trunc(_A1 __lcpp_x) _NOEXCEPT {return ::trunc((double)__lcpp_x);} +_LIBCPP_BEGIN_NAMESPACE_STD +template <class _IntT, class _FloatT, + bool _FloatBigger = (numeric_limits<_FloatT>::digits > numeric_limits<_IntT>::digits)> +struct __max_representable_int_for_float; + +template <class _IntT, class _FloatT> +struct __max_representable_int_for_float<_IntT, _FloatT, true> { + static_assert(is_floating_point<_FloatT>::value, "must be a floating point type"); + static_assert(is_integral<_IntT>::value, "must be an integral type"); + static_assert(numeric_limits<_FloatT>::radix == 2, "FloatT has incorrect radix"); + static _LIBCPP_CONSTEXPR _IntT __value() _NOEXCEPT { + return numeric_limits<_IntT>::max(); + } +}; + +template <class _IntT, class _FloatT> +struct __max_representable_int_for_float<_IntT, _FloatT, false> { + static_assert(is_floating_point<_FloatT>::value, "must be a floating point type"); + static_assert(is_integral<_IntT>::value, "must be an integral type"); + static_assert(numeric_limits<_FloatT>::radix == 2, "FloatT has incorrect radix"); + enum { _Bits = numeric_limits<_IntT>::digits - numeric_limits<_FloatT>::digits }; + // This also assumes two's compliment, which is fine because that's the only + // representation we support. + static _LIBCPP_CONSTEXPR _IntT __value() _NOEXCEPT { + return numeric_limits<_IntT>::max() >> _Bits << _Bits; + } +}; + +template <class _IntT, class _RealT> +_LIBCPP_INLINE_VISIBILITY +_IntT __clamp_to_integral(_RealT __r) _NOEXCEPT { + using _Lim = std::numeric_limits<_IntT>; + const _IntT _MaxVal = __max_representable_int_for_float<_IntT, _RealT>::__value(); + if (__r >= ::nextafter(static_cast<_RealT>(_MaxVal), INFINITY)) { + return _Lim::max(); + } else if (__r <= _Lim::lowest()) { + return _Lim::min(); + } + return static_cast<_IntT>(__r); +} +_LIBCPP_END_NAMESPACE_STD + } // extern "C++" #endif // __cplusplus
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