interleavedmemory.h

/*  This file is part of the Vc library. {{{
Copyright © 2012-2015 Matthias Kretz <kretz@kde.org>

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#ifndef VC_COMMON_INTERLEAVEDMEMORY_H_
#define VC_COMMON_INTERLEAVEDMEMORY_H_

#include "macros.h"

namespace Vc_VERSIONED_NAMESPACE
{
namespace Common
{
template<typename V, typename I, bool Readonly> struct InterleavedMemoryAccessBase
{
    // Partial specialization doesn't work for functions without partial specialization of the whole
    // class. Therefore we capture the contents of InterleavedMemoryAccessBase in a macro to easily
    // copy it into its specializations.
    typedef typename std::conditional<
        Readonly, typename std::add_const<typename V::EntryType>::type,
        typename V::EntryType>::type T;
    typedef typename V::AsArg VArg;
    typedef T Ta Vc_MAY_ALIAS;
    const I m_indexes;
    Ta *const m_data;

    Vc_ALWAYS_INLINE InterleavedMemoryAccessBase(typename I::AsArg indexes, Ta *data)
        : m_indexes(indexes), m_data(data)
    {
    }

    // implementations of the following are in {scalar,sse,avx}/detail.h
    template <typename... Vs> Vc_INTRINSIC void deinterleave(Vs &&... vs) const
    {
        Impl::deinterleave(m_data, m_indexes, std::forward<Vs>(vs)...);
    }

protected:
    using Impl = Vc::Detail::InterleaveImpl<V, V::Size, sizeof(V)>;

    template <typename T, std::size_t... Indexes>
    Vc_INTRINSIC void callInterleave(T &&a, index_sequence<Indexes...>)
    {
        Impl::interleave(m_data, m_indexes, a[Indexes]...);
    }
};

// delay execution of the deinterleaving gather until operator=
template <size_t StructSize, typename V, typename I = typename V::IndexType,
          bool Readonly>
struct InterleavedMemoryReadAccess : public InterleavedMemoryAccessBase<V, I, Readonly>
{
    typedef InterleavedMemoryAccessBase<V, I, Readonly> Base;
    typedef typename Base::Ta Ta;

    Vc_ALWAYS_INLINE InterleavedMemoryReadAccess(Ta *data, typename I::AsArg indexes)
        : Base(StructSize == 1u
                   ? indexes
                   : StructSize == 2u
                         ? indexes << 1
                         : StructSize == 4u
                               ? indexes << 2
                               : StructSize == 8u
                                     ? indexes << 3
                                     : StructSize == 16u ? indexes << 4
                                                         : indexes * I(int(StructSize)),
               data)
    {
    }

    template <typename T, std::size_t... Indexes>
    Vc_ALWAYS_INLINE T deinterleave_unpack(index_sequence<Indexes...>) const
    {
        T r;
        Base::Impl::deinterleave(this->m_data, this->m_indexes, std::get<Indexes>(r)...);
        return r;
    }

    template <typename T,
              typename = enable_if<(std::is_default_constructible<T>::value &&
                                    std::is_same<V, Traits::decay<decltype(std::get<0>(
                                                        std::declval<T &>()))>>::value)>>
    Vc_ALWAYS_INLINE operator T() const
    {
        return deinterleave_unpack<T>(make_index_sequence<std::tuple_size<T>::value>());
    }
};

template<typename I> struct CheckIndexesUnique
{
#ifdef NDEBUG
    static Vc_INTRINSIC void test(const I &) {}
#else
    static void test(const I &indexes)
    {
        const I test = indexes.sorted();
        Vc_ASSERT(I::Size == 1 || (test == test.rotated(1)).isEmpty())
    }
#endif
};
template<size_t S> struct CheckIndexesUnique<SuccessiveEntries<S> >
{
    static Vc_INTRINSIC void test(const SuccessiveEntries<S> &) {}
};

template <size_t StructSize, typename V, typename I = typename V::IndexType>
struct InterleavedMemoryAccess : public InterleavedMemoryReadAccess<StructSize, V, I, false>
{
    typedef InterleavedMemoryAccessBase<V, I, false> Base;
    typedef typename Base::Ta Ta;

    Vc_ALWAYS_INLINE InterleavedMemoryAccess(Ta *data, typename I::AsArg indexes)
        : InterleavedMemoryReadAccess<StructSize, V, I, false>(data, indexes)
    {
        CheckIndexesUnique<I>::test(indexes);
    }

    template <int N> Vc_ALWAYS_INLINE void operator=(VectorReferenceArray<N, V> &&rhs)
    {
        static_assert(N <= StructSize,
                      "You_are_trying_to_scatter_more_data_into_the_struct_than_it_has");
        this->callInterleave(std::move(rhs), make_index_sequence<N>());
    }
    template <int N> Vc_ALWAYS_INLINE void operator=(VectorReferenceArray<N, const V> &&rhs)
    {
        static_assert(N <= StructSize,
                      "You_are_trying_to_scatter_more_data_into_the_struct_than_it_has");
        this->callInterleave(std::move(rhs), make_index_sequence<N>());
    }
};

template<typename S, typename V> class InterleavedMemoryWrapper
{
    typedef typename std::conditional<std::is_const<S>::value,
                                      const typename V::EntryType,
                                      typename V::EntryType>::type T;
    typedef typename V::IndexType I;
    typedef typename V::AsArg VArg;
    typedef const I &IndexType;
    static constexpr std::size_t StructSize = sizeof(S) / sizeof(T);
    using ReadAccess = InterleavedMemoryReadAccess<StructSize, V>;
    using Access =
        typename std::conditional<std::is_const<T>::value, ReadAccess,
                                  InterleavedMemoryAccess<StructSize, V>>::type;
    using ReadSuccessiveEntries =
        InterleavedMemoryReadAccess<StructSize, V, SuccessiveEntries<StructSize>>;
    using AccessSuccessiveEntries = typename std::conditional<
        std::is_const<T>::value, ReadSuccessiveEntries,
        InterleavedMemoryAccess<StructSize, V, SuccessiveEntries<StructSize>>>::type;
    typedef T Ta Vc_MAY_ALIAS;
    Ta *const m_data;

    static_assert(StructSize * sizeof(T) == sizeof(S),
                  "InterleavedMemoryAccess_does_not_support_packed_structs");

public:
    Vc_ALWAYS_INLINE InterleavedMemoryWrapper(S *s)
        : m_data(reinterpret_cast<Ta *>(s))
    {
    }

    template <typename IT>
    Vc_ALWAYS_INLINE enable_if<!std::is_convertible<IT, size_t>::value &&
                                   std::is_convertible<IT, IndexType>::value &&
                                   !std::is_const<S>::value,
                               Access>
    operator[](IT indexes)
    {
        return Access(m_data, indexes);
    }

    Vc_ALWAYS_INLINE ReadAccess operator[](IndexType indexes) const
    {
        return ReadAccess(m_data, indexes);
    }

    Vc_ALWAYS_INLINE ReadAccess gather(IndexType indexes) const { return operator[](indexes); }

    Vc_ALWAYS_INLINE ReadSuccessiveEntries operator[](size_t first) const
    {
        return ReadSuccessiveEntries(m_data, first);
    }

    Vc_ALWAYS_INLINE AccessSuccessiveEntries operator[](size_t first)
    {
        return AccessSuccessiveEntries(m_data, first);
    }

    //Vc_ALWAYS_INLINE Access scatter(I indexes, VArg v0, VArg v1);
};
}  // namespace Common

using Common::InterleavedMemoryWrapper;

template <typename V, typename S>
inline Common::InterleavedMemoryWrapper<S, V> make_interleave_wrapper(S *s)
{
    return Common::InterleavedMemoryWrapper<S, V>(s);
}
}  // namespace Vc

#endif // VC_COMMON_INTERLEAVEDMEMORY_H_