loadstoreflags.h

/*  This file is part of the Vc library. {{{
Copyright © 2013-2015 Matthias Kretz <kretz@kde.org>

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      derived from this software without specific prior written permission.

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}}}*/

#ifndef VC_COMMON_LOADSTOREFLAGS_H_
#define VC_COMMON_LOADSTOREFLAGS_H_

#include "../traits/type_traits.h"

namespace Vc_VERSIONED_NAMESPACE
{

struct Exclusive {};
struct Shared {};

namespace LoadStoreFlags
{

struct StreamingFlag {};
struct UnalignedFlag {};
struct PrefetchFlagBase {};
// TODO: determine a good default for typical CPU use
template <size_t L1 = 16 * 64, size_t L2 = 128 * 64, typename ExclusiveOrShared_ = void>
struct PrefetchFlag : public PrefetchFlagBase {
    typedef ExclusiveOrShared_ ExclusiveOrShared;
    static constexpr size_t L1Stride = L1;
    static constexpr size_t L2Stride = L2;
    static constexpr bool IsExclusive = std::is_same<ExclusiveOrShared, Exclusive>::value;
    static constexpr bool IsShared = std::is_same<ExclusiveOrShared, Shared>::value;
};

template<typename Base, typename Default, typename... LoadStoreFlags> struct ExtractType
{
    typedef Default type;
};
template<typename Base, typename Default, typename T, typename... LoadStoreFlags> struct ExtractType<Base, Default, T, LoadStoreFlags...>
{
    typedef typename std::conditional<std::is_base_of<Base, T>::value, T, typename ExtractType<Base, Default, LoadStoreFlags...>::type>::type type;
};

// ICC warns about the constexpr members in LoadStoreFlags: member "LoadStoreFlags<Flags...>::IsAligned" was declared but never referenced
// who needs that warning, especially if it was referenced...
// The warning cannot be reenabled because it gets emitted whenever the LoadStoreFlags is instantiated
// somewhere, so it could be anywhere.
#ifdef Vc_ICC
#pragma warning(disable: 177)
#endif

template<typename... Flags> struct LoadStoreFlags
{
private:
    // ICC doesn't grok this line:
    //template<typename Test> using TestFlag = std::is_same<typename ExtractType<StreamingFlag, void, Flags...>::type, void>;
    typedef typename ExtractType<PrefetchFlagBase, PrefetchFlag<0, 0>, Flags...>::type Prefetch;

public:
    constexpr LoadStoreFlags() {}

    static constexpr bool IsStreaming = !std::is_same<typename ExtractType<StreamingFlag, void, Flags...>::type, void>::value;
    static constexpr bool IsUnaligned = !std::is_same<typename ExtractType<UnalignedFlag, void, Flags...>::type, void>::value;
    static constexpr bool IsAligned = !IsUnaligned;
    static constexpr bool IsPrefetch = !std::is_same<typename ExtractType<PrefetchFlagBase, void, Flags...>::type, void>::value;
    static constexpr bool IsExclusivePrefetch = Prefetch::IsExclusive;
    static constexpr bool IsSharedPrefetch = Prefetch::IsShared;
    static constexpr size_t L1Stride = Prefetch::L1Stride;
    static constexpr size_t L2Stride = Prefetch::L2Stride;

    typedef LoadStoreFlags<typename std::conditional<std::is_same<Flags, UnalignedFlag>::value, void, Flags>::type...> UnalignedRemoved;

    // The following EnableIf* convenience types cannot use enable_if because then no LoadStoreFlags type
    // could ever be instantiated. Instead these types are defined either as void* or void. The
    // function that does SFINAE then assigns "= nullptr" to this type. Thus, the ones with just
    // void result in substitution failure.
    typedef typename std::conditional<IsAligned   && !IsStreaming, void *, void>::type EnableIfAligned;
    typedef typename std::conditional<IsAligned   &&  IsStreaming, void *, void>::type EnableIfStreaming;
    typedef typename std::conditional<IsUnaligned && !IsStreaming, void *, void>::type EnableIfUnalignedNotStreaming;
    typedef typename std::conditional<IsUnaligned &&  IsStreaming, void *, void>::type EnableIfUnalignedAndStreaming;
    typedef typename std::conditional<IsUnaligned                , void *, void>::type EnableIfUnaligned;
    typedef typename std::conditional<!IsUnaligned               , void *, void>::type EnableIfNotUnaligned;
    typedef typename std::conditional<IsPrefetch                 , void *, void>::type EnableIfPrefetch;
    typedef typename std::conditional<!IsPrefetch                , void *, void>::type EnableIfNotPrefetch;
};

template<> struct LoadStoreFlags<>
{
    constexpr LoadStoreFlags() {}

    static constexpr bool IsStreaming = false;
    static constexpr bool IsUnaligned = false;
    static constexpr bool IsAligned = !IsUnaligned;
    static constexpr bool IsPrefetch = false;
    static constexpr bool IsExclusivePrefetch = false;
    static constexpr bool IsSharedPrefetch = false;
    static constexpr size_t L1Stride = 0;
    static constexpr size_t L2Stride = 0;
    typedef void* EnableIfAligned;
    typedef void* EnableIfNotUnaligned;
    typedef void* EnableIfNotPrefetch;
};

template<typename... LFlags, typename... RFlags>
constexpr LoadStoreFlags<LFlags..., RFlags...> operator|(LoadStoreFlags<LFlags...>, LoadStoreFlags<RFlags...>)
{
    return LoadStoreFlags<LFlags..., RFlags...>();
}

} // LoadStoreFlags namespace

using LoadStoreFlags::PrefetchFlag;

typedef LoadStoreFlags::LoadStoreFlags<> AlignedTag;
typedef LoadStoreFlags::LoadStoreFlags<LoadStoreFlags::StreamingFlag> StreamingTag;
typedef LoadStoreFlags::LoadStoreFlags<LoadStoreFlags::UnalignedFlag> UnalignedTag;

typedef UnalignedTag DefaultLoadTag;
typedef UnalignedTag DefaultStoreTag;

constexpr AlignedTag Aligned;

constexpr UnalignedTag Unaligned;

constexpr StreamingTag Streaming;

constexpr LoadStoreFlags::LoadStoreFlags<PrefetchFlag<>> PrefetchDefault;

template <size_t L1 = PrefetchFlag<>::L1Stride,
          size_t L2 = PrefetchFlag<>::L2Stride,
          typename ExclusiveOrShared = PrefetchFlag<>::ExclusiveOrShared>
struct Prefetch : public LoadStoreFlags::LoadStoreFlags<PrefetchFlag<L1, L2, ExclusiveOrShared>>
{
};

namespace Traits
{
template <typename... Ts>
struct is_loadstoreflag_internal<LoadStoreFlags::LoadStoreFlags<Ts...>> : public std::true_type
{
};
template <size_t L1, size_t L2, typename ExclusiveOrShared>
struct is_loadstoreflag_internal<Prefetch<L1, L2, ExclusiveOrShared>> : public std::true_type
{
};
}  // namespace Traits
}  // namespace Vc

#endif // VC_COMMON_LOADSTOREFLAGS_H_