scatterinterface.h

/*  This file is part of the Vc library. {{{
Copyright © 2014-2015 Matthias Kretz <kretz@kde.org>

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///////////////////////////////////////////////////////////////////////////////////////////
// scatters
// A scatter takes the following arguments:
// 1. A pointer to memory of any type that EntryType can convert to.
// 2. An indexes “vector”. The requirement is that the type implements the subscript operator,
//    stores «Size» valid index values, and each offset to the pointer above yields a valid
//    memory location for reading.
// 3. Optionally the third argument may be a mask. The mask disables several memory stores and
//    thus removes the requirements in (2.) for the disabled entries.

private:
    /**\internal
     * This function implements a scatter given a pointer to memory \p mem and some
     * container object storing the scatter \p indexes.
     *
     * \param mem This pointer must be aligned correctly for the type \p MT. This is the
     * natural behavior of C++, so this is typically the case.
     * \param indexes This object contains at least \VSize{T} indexes that denote the
     * offset in \p mem where the components for the current vector should be copied to.
     * The offset is not in Bytes, but in multiples of `sizeof(MT)`.
     */
    // enable_if<std::can_convert<MT, EntryType>::value && has_subscript_operator<IT>::value>
    template <typename MT, typename IT>
    inline void scatterImplementation(MT *mem, IT &&indexes) const;

    /**\internal
     * This overload of the above function adds a \p mask argument to disable memory
     * accesses at the \p indexes offsets where \p mask is \c false.
     */
    template <typename MT, typename IT>
    inline void scatterImplementation(MT *mem, IT &&indexes, MaskArgument mask) const;

public:
#define Vc_ASSERT_SCATTER_PARAMETER_TYPES_                                               \
    static_assert(                                                                       \
        std::is_convertible<EntryType, MT>::value,                                       \
        "The memory pointer needs to point to a type that the EntryType of this "        \
        "SIMD vector type can be converted to.");                                        \
    static_assert(                                                                       \
        Vc::Traits::has_subscript_operator<IT>::value,                                   \
        "The indexes argument must be a type that implements the subscript operator.");  \
    static_assert(                                                                       \
        !Traits::is_simd_vector<IT>::value ||                                            \
            Traits::simd_vector_size<IT>::value >= Size,                                 \
        "If you use a SIMD vector for the indexes parameter, the index vector must "     \
        "have at least as many entries as this SIMD vector.");                           \
    static_assert(                                                                       \
        !std::is_array<T>::value ||                                                      \
            (std::rank<T>::value == 1 &&                                                 \
             (std::extent<T>::value == 0 || std::extent<T>::value >= Size)),             \
        "If you use a simple array for the indexes parameter, the array must have "      \
        "at least as many entries as this SIMD vector.")

    /**
     * \name Scatter functions
     *
     * Stores a vector to the objects at `mem[indexes[0]]`, `mem[indexes[1]]`,
     * `mem[indexes[2]]`, ...
     *
     * \param mem A pointer to memory which contains objects of type \p MT at the offsets
     *            given by \p indexes.
     * \param indexes
     * \param mask
     */
    ///@{

    /// Scatter function
    template <typename MT,
              typename IT,
              typename = enable_if<Vc::Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC void scatter(MT *mem, IT &&indexes) const
    {
        Vc_ASSERT_SCATTER_PARAMETER_TYPES_;
        scatterImplementation(mem, std::forward<IT>(indexes));
    }

    /// Masked scatter function
    template <typename MT,
              typename IT,
              typename = enable_if<Vc::Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC void scatter(MT *mem, IT &&indexes, MaskArgument mask) const
    {
        Vc_ASSERT_SCATTER_PARAMETER_TYPES_;
        scatterImplementation(mem, std::forward<IT>(indexes), mask);
    }
    ///@}

#include "scatterinterface_deprecated.h"

    /**\internal
     * \name Scatter function to use from Vc::Common::subscript_operator
     *
     * \param args
     * \param mask
     */
    ///@{
    template <typename MT, typename IT>
    Vc_INTRINSIC void scatter(const Common::ScatterArguments<MT, IT> &args) const
    {
        scatter(args.address, args.indexes);
    }

    template <typename MT, typename IT>
    Vc_INTRINSIC void scatter(const Common::ScatterArguments<MT, IT> &args, MaskArgument mask) const
    {
        scatter(args.address, args.indexes, mask);
    }
    ///@}
#undef Vc_ASSERT_SCATTER_PARAMETER_TYPES_