xref: /freebsd/contrib/llvm-project/clang/lib/Headers/cuda_wrappers/algorithm (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)

/*===---- algorithm - CUDA wrapper for <algorithm> -------------------------===
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 *===-----------------------------------------------------------------------===
 */

#ifndef __CLANG_CUDA_WRAPPERS_ALGORITHM
#define __CLANG_CUDA_WRAPPERS_ALGORITHM

// This header defines __device__ overloads of std::min/max.
//
// Ideally we'd declare these functions only if we're <= C++11.  In C++14,
// these functions are constexpr, and so are implicitly __host__ __device__.
//
// However, the compiler being in C++14 mode does not imply that the standard
// library supports C++14.  There is no macro we can test to check that the
// stdlib has constexpr std::min/max.  Thus we have to unconditionally define
// our device overloads.
//
// A host+device function cannot be overloaded, and a constexpr function
// implicitly become host device if there's no explicitly host or device
// overload preceding it.  So the simple thing to do would be to declare our
// device min/max overloads, and then #include_next <algorithm>.  This way our
// device overloads would come first, and so if we have a C++14 stdlib, its
// min/max won't become host+device and conflict with our device overloads.
//
// But that also doesn't work.  libstdc++ is evil and declares std::min/max in
// an internal header that is included *before* <algorithm>.  Thus by the time
// we're inside of this file, std::min/max may already have been declared, and
// thus we can't prevent them from becoming host+device if they're constexpr.
//
// Therefore we perpetrate the following hack: We mark our __device__ overloads
// with __attribute__((enable_if(true, ""))).  This causes the signature of the
// function to change without changing anything else about it.  (Except that
// overload resolution will prefer it over the __host__ __device__ version
// rather than considering them equally good).

#include_next <algorithm>

// We need to define these overloads in exactly the namespace our standard
// library uses (including the right inline namespace), otherwise they won't be
// picked up by other functions in the standard library (e.g. functions in
// <complex>).  Thus the ugliness below.
#ifdef _LIBCPP_BEGIN_NAMESPACE_STD
_LIBCPP_BEGIN_NAMESPACE_STD
#else
namespace std {
#ifdef _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif
#endif

#pragma push_macro("_CPP14_CONSTEXPR")
#if __cplusplus >= 201402L
#define _CPP14_CONSTEXPR constexpr
#else
#define _CPP14_CONSTEXPR
#endif

template <class __T, class __Cmp>
__attribute__((enable_if(true, "")))
inline _CPP14_CONSTEXPR __host__ __device__ const __T &
max(const __T &__a, const __T &__b, __Cmp __cmp) {
  return __cmp(__a, __b) ? __b : __a;
}

template <class __T>
__attribute__((enable_if(true, "")))
inline _CPP14_CONSTEXPR __host__ __device__ const __T &
max(const __T &__a, const __T &__b) {
  return __a < __b ? __b : __a;
}

template <class __T, class __Cmp>
__attribute__((enable_if(true, "")))
inline _CPP14_CONSTEXPR __host__ __device__ const __T &
min(const __T &__a, const __T &__b, __Cmp __cmp) {
  return __cmp(__b, __a) ? __b : __a;
}

template <class __T>
__attribute__((enable_if(true, "")))
inline _CPP14_CONSTEXPR __host__ __device__ const __T &
min(const __T &__a, const __T &__b) {
  return __b < __a ? __b : __a;
}

#pragma pop_macro("_CPP14_CONSTEXPR")

#ifdef _LIBCPP_END_NAMESPACE_STD
_LIBCPP_END_NAMESPACE_STD
#else
#ifdef _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_END_NAMESPACE_VERSION
#endif
} // namespace std
#endif

#endif // __CLANG_CUDA_WRAPPERS_ALGORITHM