loadstoreflags.h

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

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the names of contributing organizations nor the
      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
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

}}}*/

#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 {};
#ifdef Vc_IMPL_MIC
template<size_t L1 = 8 * 64, size_t L2 = 64 * 64,
#else
// TODO: determine a good default for typical CPU use
template<size_t L1 = 16 * 64, size_t L2 = 128 * 64,
#endif
    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_