Vc/common/utility.h

0001 /*  This file is part of the Vc library. {{{
0002 Copyright © 2014-2015 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_UTILITY_H_
0029 #define VC_COMMON_UTILITY_H_
0030
0031 #include "macros.h"
0032
0033 namespace Vc_VERSIONED_NAMESPACE
0034 {
0035 namespace Common
0036 {
0037 /**
0038  * \internal
0039  * Returns the next power of 2 larger than or equal to \p x.
0040  */
0041 template <size_t x, bool = (x & (x - 1)) == 0> struct NextPowerOfTwo;
0042 template <size_t x>
0043 struct NextPowerOfTwo<x, true> : public std::integral_constant<size_t, x> {
0044 };
0045 template <size_t x>
0046 struct NextPowerOfTwo<x, false>
0047     : public std::integral_constant<
0048           size_t, NextPowerOfTwo<(x | (x >> 1) | (x >> 2) | (x >> 5)) + 1>::value> {
0049 };
0050
0051 /**
0052  * \internal
0053  * Enforce an upper bound to an alignment value. This is necessary because some compilers
0054  * implement such an upper bound and emit a warning if it is encountered.
0055  */
0056 template <size_t A>
0057 struct BoundedAlignment : public std::integral_constant<size_t,
0058 #if defined Vc_MSVC || defined Vc_GCC
0059                                                         ((A - 1) &
0060 #ifdef Vc_MSVC
0061                                                          31
0062 #elif defined __AVX__
0063                                                          255
0064 #else
0065                                                          127
0066 #endif
0067                                                          ) + 1
0068 #else
0069                                                         A
0070 #endif
0071                                                         > {
0072 };
0073
0074 /**
0075  * \internal
0076  * Returns the size of the left/first SimdArray member.
0077  */
0078 template <std::size_t N> static constexpr std::size_t left_size()
0079 {
0080     return Common::NextPowerOfTwo<(N + 1) / 2>::value;
0081 }
0082 /**
0083  * \internal
0084  * Returns the size of the right/second SimdArray member.
0085  */
0086 template <std::size_t N> static constexpr std::size_t right_size()
0087 {
0088     return N - left_size<N>();
0089 }
0090
0091 }  // namespace Common
0092 }  // namespace Vc
0093
0094 #endif  // VC_COMMON_UTILITY_H_
0095
0096 // vim: foldmethod=marker