std::align for pointers

[neoblizz]

Code from RXMesh: https://github.com/owensgroup/RXMesh/blob/memcpy_async/include/rxmesh/util/util.h#L390-L411

/**
 * @brief given a pointer, this function returns a pointer to the first location
 * at the boundary of a given alignment size. This what std:align does but it
 * does not work with CUDA so this a stripped down version of it.
 * @tparam T type of the pointer
 * @param byte_alignment number of bytes to get the pointer to be aligned to
 * @param ptr input/output pointer pointing at first usable location. On return,
 * it will be properly aligned to the beginning of the first element that is
 * aligned to alignment
 */
template <typename T>
__device__ __host__ __inline__ void align(const std::size_t byte_alignment,
                                          T*&               ptr) noexcept
{
    const uint64_t intptr    = reinterpret_cast<uint64_t>(ptr);
    const uint64_t remainder = intptr % byte_alignment;
    if (remainder == 0) {
        return;
    }
    const uint64_t aligned = intptr + byte_alignment - remainder;
    ptr                    = reinterpret_cast<T*>(aligned);
}

https://nvidia.github.io/libcudacxx/extended_api/shapes/aligned_size_t.html
https://stackoverflow.com/questions/70765553/cuda-shared-memory-alignement-in-documentation