gatherinterface.h

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

Redistribution and use in source and binary forms, with or without
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      notice, this list of conditions and the following disclaimer.
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      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
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      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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}}}*/

#ifndef Vc_CURRENT_CLASS_NAME
#error "incorrect use of common/gatherinterface.h: Vc_CURRENT_CLASS_NAME must be defined to the current class name for declaring constructors."
#endif

// gathers
// A gather takes the following arguments:
// 1. A const pointer to memory of any type that can convert to EntryType
// 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 reads and
//    thus removes the requirements in (2.) for the disabled entries.

private:
    // enable_if<std::can_convert<MT, EntryType>::value &&
    // has_subscript_operator<IT>::value>
    template <typename MT, typename IT>
    inline void gatherImplementation(const MT *mem, const IT &indexes);

    template <typename MT, typename IT>
    inline void gatherImplementation(const MT *mem, const IT &indexes, MaskArgument mask);

    template <typename IT, typename = enable_if<std::is_pointer<IT>::value ||
                                                Traits::is_simd_vector<IT>::value>>
    static Vc_INTRINSIC const IT &adjustIndexParameter(const IT &indexes)
    {
        return indexes;
    }

    template <
        typename IT,
        typename = enable_if<
            !std::is_pointer<IT>::value && !Traits::is_simd_vector<IT>::value &&
            std::is_lvalue_reference<decltype(std::declval<const IT &>()[0])>::value>>
    static Vc_INTRINSIC decltype(std::addressof(std::declval<const IT &>()[0]))
    adjustIndexParameter(const IT &i)
    {
        return std::addressof(i[0]);
    }

    template <typename IT>
    static Vc_INTRINSIC enable_if<
        !std::is_pointer<IT>::value && !Traits::is_simd_vector<IT>::value &&
            !std::is_lvalue_reference<decltype(std::declval<const IT &>()[0])>::value,
        IT>
    adjustIndexParameter(const IT &i)
    {
        return i;
    }

public:
#define Vc_ASSERT_GATHER_PARAMETER_TYPES_                                                \
    static_assert(                                                                       \
        std::is_convertible<MT, EntryType>::value,                                       \
        "The memory pointer needs to point to a type that can be converted to the "      \
        "EntryType of this SIMD vector type.");                                          \
    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.")


    template <typename MT, typename IT,
              typename = enable_if<Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC Vc_CURRENT_CLASS_NAME(const MT *mem, const IT &indexes)
    {
        Vc_ASSERT_GATHER_PARAMETER_TYPES_;
        gatherImplementation(mem, adjustIndexParameter(indexes));
    }

    template <typename MT, typename IT,
              typename = enable_if<Vc::Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC Vc_CURRENT_CLASS_NAME(const MT *mem, const IT &indexes,
                                       MaskArgument mask)
    {
        Vc_ASSERT_GATHER_PARAMETER_TYPES_;
        gatherImplementation(mem, adjustIndexParameter(indexes), mask);
    }

    template <typename MT, typename IT,
              typename = enable_if<Vc::Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC void gather(const MT *mem, const IT &indexes)
    {
        Vc_ASSERT_GATHER_PARAMETER_TYPES_;
        gatherImplementation(mem, adjustIndexParameter(indexes));
    }

    template <typename MT, typename IT,
              typename = enable_if<Vc::Traits::has_subscript_operator<IT>::value>>
    Vc_INTRINSIC void gather(const MT *mem, const IT &indexes, MaskArgument mask)
    {
        Vc_ASSERT_GATHER_PARAMETER_TYPES_;
        gatherImplementation(mem, adjustIndexParameter(indexes), mask);
    }

#include "gatherinterface_deprecated.h"

    template <typename MT, typename IT>
    Vc_INTRINSIC void gather(const Common::GatherArguments<MT, IT> &args)
    {
        gather(args.address, adjustIndexParameter(args.indexes));
    }

    template <typename MT, typename IT>
    Vc_INTRINSIC void gather(const Common::GatherArguments<MT, IT> &args, MaskArgument mask)
    {
        gather(args.address, adjustIndexParameter(args.indexes), mask);
    }

#undef Vc_ASSERT_GATHER_PARAMETER_TYPES_