where.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
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}}}*/

#ifndef VC_COMMON_WHERE_H_
#define VC_COMMON_WHERE_H_

#include "types.h"
#include "macros.h"

namespace Vc_VERSIONED_NAMESPACE
{

namespace WhereImpl
{

    template<typename _Mask, typename _LValue> struct MaskedLValue
    {
        typedef _Mask Mask;
        typedef _LValue LValue;

        const Mask &mask;
        LValue &lhs;

        // the ctors must be present, otherwise GCC fails to warn for Vc_WARN_UNUSED_RESULT
        constexpr MaskedLValue(const Mask &m, LValue &l) : mask(m), lhs(l) {}
        MaskedLValue(const MaskedLValue &) = delete;
        constexpr MaskedLValue(MaskedLValue &&) = default;

        /* It is intentional that the assignment operators return void: When a bool is used for the
         * mask the code might get skipped completely, thus nothing can be returned. This would be
         * like requiring an if statement to return a value.
         */
        template<typename T> Vc_ALWAYS_INLINE void operator  =(T &&rhs) { conditional_assign<Operator::          Assign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator +=(T &&rhs) { conditional_assign<Operator::      PlusAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator -=(T &&rhs) { conditional_assign<Operator::     MinusAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator *=(T &&rhs) { conditional_assign<Operator::  MultiplyAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator /=(T &&rhs) { conditional_assign<Operator::    DivideAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator %=(T &&rhs) { conditional_assign<Operator:: RemainderAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator ^=(T &&rhs) { conditional_assign<Operator::       XorAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator &=(T &&rhs) { conditional_assign<Operator::       AndAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator |=(T &&rhs) { conditional_assign<Operator::        OrAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator<<=(T &&rhs) { conditional_assign<Operator:: LeftShiftAssign>(lhs, mask, std::forward<T>(rhs)); }
        template<typename T> Vc_ALWAYS_INLINE void operator>>=(T &&rhs) { conditional_assign<Operator::RightShiftAssign>(lhs, mask, std::forward<T>(rhs)); }
        Vc_ALWAYS_INLINE void operator++()    { conditional_assign<Operator:: PreIncrement>(lhs, mask); }
        Vc_ALWAYS_INLINE void operator++(int) { conditional_assign<Operator::PostIncrement>(lhs, mask); }
        Vc_ALWAYS_INLINE void operator--()    { conditional_assign<Operator:: PreDecrement>(lhs, mask); }
        Vc_ALWAYS_INLINE void operator--(int) { conditional_assign<Operator::PostDecrement>(lhs, mask); }
    };

    template <typename _Mask, typename T_, typename I_, typename S_>
    struct MaskedLValue<_Mask, Common::SubscriptOperation<T_, I_, S_, true>>
    {
        typedef _Mask Mask;
        typedef Common::SubscriptOperation<T_, I_, S_, true> SO;

        const Mask &mask;
        const SO lhs;

        template <typename T> using Decay = typename std::decay<T>::type;

        // the ctors must be present, otherwise GCC fails to warn for Vc_WARN_UNUSED_RESULT
        constexpr MaskedLValue(const Mask &m, SO &&l) : mask(m), lhs(l) {}
        MaskedLValue(const MaskedLValue &) = delete;
        constexpr MaskedLValue(MaskedLValue &&) = default;

        /* It is intentional that the assignment operators return void: When a bool is used for the
         * mask the code might get skipped completely, thus nothing can be returned. This would be
         * like requiring an if statement to return a value.
         */
        template<typename T> Vc_ALWAYS_INLINE void operator  =(T &&rhs) { std::forward<T>(rhs).scatter(lhs.scatterArguments(), mask); }
        /*
         * The following operators maybe make some sense. But only if implemented directly on the
         * scalar objects in memory. Thus, the user is probably better of with a manual loop.
         *
         * If implemented the operators would need to do a masked gather, one operation, and a
         * masked scatter. There is no way this is going to be efficient.
         *
        template<typename T> Vc_ALWAYS_INLINE void operator +=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  + std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator -=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  - std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator *=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  * std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator /=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  / std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator %=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  % std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator ^=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  ^ std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator &=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  & std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator |=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask)  | std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator<<=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask) << std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        template<typename T> Vc_ALWAYS_INLINE void operator>>=(T &&rhs) { (Decay<T>(lhs.gatherArguments(), mask) >> std::forward<T>(rhs)).scatter(lhs.scatterArguments(), mask); }
        Vc_ALWAYS_INLINE void operator++()    { ++lhs(mask); }
        Vc_ALWAYS_INLINE void operator++(int) { lhs(mask)++; }
        Vc_ALWAYS_INLINE void operator--()    { --lhs(mask); }
        Vc_ALWAYS_INLINE void operator--(int) { lhs(mask)--; }
        */
    };

    template<typename _LValue> struct MaskedLValue<bool, _LValue>
    {
        typedef bool Mask;
        typedef _LValue LValue;

        const Mask &mask;
        LValue &lhs;

        // the ctors must be present, otherwise GCC fails to warn for Vc_WARN_UNUSED_RESULT
        constexpr MaskedLValue(const Mask &m, LValue &l) : mask(m), lhs(l) {}
        MaskedLValue(const MaskedLValue &) = delete;
        constexpr MaskedLValue(MaskedLValue &&) = default;

        template<typename T> Vc_ALWAYS_INLINE void operator  =(T &&rhs) { if (mask) lhs   = std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator +=(T &&rhs) { if (mask) lhs  += std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator -=(T &&rhs) { if (mask) lhs  -= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator *=(T &&rhs) { if (mask) lhs  *= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator /=(T &&rhs) { if (mask) lhs  /= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator %=(T &&rhs) { if (mask) lhs  %= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator ^=(T &&rhs) { if (mask) lhs  ^= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator &=(T &&rhs) { if (mask) lhs  &= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator |=(T &&rhs) { if (mask) lhs  |= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator<<=(T &&rhs) { if (mask) lhs <<= std::forward<T>(rhs); }
        template<typename T> Vc_ALWAYS_INLINE void operator>>=(T &&rhs) { if (mask) lhs >>= std::forward<T>(rhs); }
        Vc_ALWAYS_INLINE void operator++()    { if (mask) ++lhs; }
        Vc_ALWAYS_INLINE void operator++(int) { if (mask) lhs++; }
        Vc_ALWAYS_INLINE void operator--()    { if (mask) --lhs; }
        Vc_ALWAYS_INLINE void operator--(int) { if (mask) lhs--; }
    };

    template<typename _Mask> struct WhereMask
    {
        typedef _Mask Mask;
        const Mask &mask;

        // the ctors must be present, otherwise GCC fails to warn for Vc_WARN_UNUSED_RESULT
        constexpr WhereMask(const Mask &m) : mask(m) {}
        WhereMask(const WhereMask &) = delete;

        template <typename T, typename I, typename S>
        constexpr Vc_WARN_UNUSED_RESULT
            MaskedLValue<Mask, Common::SubscriptOperation<T, I, S, true>>
            operator|(Common::SubscriptOperation<T, I, S, true> &&lhs) const
        {
            static_assert(!std::is_const<T>::value,
                          "masked scatter to constant memory not possible.");
            return {mask, std::move(lhs)};
        }

        template<typename T> constexpr Vc_WARN_UNUSED_RESULT MaskedLValue<Mask, T> operator|(T &&lhs) const
        {
            static_assert(std::is_lvalue_reference<T>::value, "Syntax error: Incorrect use of Vc::where. Maybe operator precedence got you by surprise. Examples of correct usage:\n"
                    "  Vc::where(x < 2) | x += 1;\n"
                    "  (Vc::where(x < 2) | x)++;\n"
                    "  Vc::where(x < 2)(x) += 1;\n"
                    "  Vc::where(x < 2)(x)++;\n"
                    );
            return { mask, lhs };
        }

        template<typename T> constexpr Vc_WARN_UNUSED_RESULT MaskedLValue<Mask, T> operator()(T &&lhs) const
        {
            return operator|(std::forward<T>(lhs));
        }
    };
}  // namespace WhereImpl

template<typename M> constexpr Vc_WARN_UNUSED_RESULT WhereImpl::WhereMask<M> where(const M &mask)
{
    return { mask };
}

template<typename M> constexpr Vc_WARN_UNUSED_RESULT WhereImpl::WhereMask<M> _if(const M &m)
{
    return { m };
}

}  // namespace Vc

#endif // VC_COMMON_WHERE_H_