Vc/common/const.h

0001 /*  This file is part of the Vc library. {{{
0002 Copyright © 2013-2015 Matthias Kretz <kretz@kde.org>
0003
0004 Redistribution and use in source and binary forms, with or without
0005 modification, are permitted provided that the following conditions are met:
0006     * Redistributions of source code must retain the above copyright
0007       notice, this list of conditions and the following disclaimer.
0008     * Redistributions in binary form must reproduce the above copyright
0009       notice, this list of conditions and the following disclaimer in the
0010       documentation and/or other materials provided with the distribution.
0011     * Neither the names of contributing organizations nor the
0012       names of its contributors may be used to endorse or promote products
0013       derived from this software without specific prior written permission.
0014
0015 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
0016 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
0017 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
0018 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
0019 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
0020 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
0021 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
0022 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
0023 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
0024 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
0025
0026 }}}*/
0027
0028 #ifndef VC_COMMON_CONST_H_
0029 #define VC_COMMON_CONST_H_
0030
0031 #include <type_traits>
0032 #include "../global.h"
0033
0034 namespace Vc_VERSIONED_NAMESPACE
0035 {
0036 namespace Detail
0037 {
0038
0039 template <int exponent> constexpr double exponentToFloat(std::integral_constant<bool, true>);
0040 template <int exponent> constexpr double exponentToFloat(std::integral_constant<bool, false>);
0041 template <> constexpr double exponentToFloat<0>(std::integral_constant<bool, true>)
0042 {
0043     return 1.;
0044 }
0045 template <> constexpr double exponentToFloat<0>(std::integral_constant<bool, false>)
0046 {
0047     return 1.;
0048 }
0049 template <> constexpr double exponentToFloat<-32>(std::integral_constant<bool, true>)
0050 {
0051     return 1. / (65536. * 65536.);
0052 }
0053 template <> constexpr double exponentToFloat<32>(std::integral_constant<bool, false>)
0054 {
0055     return 65536. * 65536.;
0056 }
0057 template <> constexpr double exponentToFloat<-64>(std::integral_constant<bool, true>)
0058 {
0059     return 1. / (65536. * 65536. * 65536. * 65536.);
0060 }
0061 template <> constexpr double exponentToFloat<64>(std::integral_constant<bool, false>)
0062 {
0063     return 65536. * 65536. * 65536. * 65536.;
0064 }
0065 template <int exponent>
0066 constexpr double exponentToFloat(std::integral_constant<bool, false> negative)
0067 {
0068     return exponentToFloat<exponent - 1>(negative) * 2.0;
0069 }
0070 template <int exponent>
0071 constexpr double exponentToFloat(std::integral_constant<bool, true> negative)
0072 {
0073     return exponentToFloat<exponent + 1>(negative) * 0.5;
0074 }
0075 template <int sign, unsigned long long mantissa, int exponent> constexpr double doubleConstant()
0076 {
0077     return (static_cast<double>((mantissa & 0x000fffffffffffffull) | 0x0010000000000000ull) /
0078             0x0010000000000000ull) *
0079            exponentToFloat<exponent>(std::integral_constant<bool, (exponent < 0)>()) * sign;
0080 }
0081 template <int sign, unsigned int mantissa, int exponent> constexpr float floatConstant()
0082 {
0083     return (static_cast<float>((mantissa & 0x007fffffu) | 0x00800000u) / 0x00800000u) *
0084            static_cast<float>(
0085                exponentToFloat<exponent>(std::integral_constant<bool, (exponent < 0)>())) *
0086            sign;
0087 }
0088
0089 }  // namespace Detail
0090 }  // namespace Vc
0091
0092 #endif // VC_COMMON_CONST_H_