/*
 * SPDX-FileCopyrightText: Copyright (c) 2021 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
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 * NVIDIA SOFTWARE LICENSE
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 * 14. GOVERNMENT USE. The SOFTWARE has been developed entirely at private expense and is “commercial items” consisting of “commercial computer software” and “commercial computer software documentation” provided with RESTRICTED RIGHTS. Use, duplication or disclosure by the U.S. Government or a U.S. Government subcontractor is subject to the restrictions in this license pursuant to DFARS 227.7202-3(a) or as set forth in subparagraphs (b)(1) and (2) of the Commercial Computer Software - Restricted Rights clause at FAR 52.227-19, as applicable. Contractor/manufacturer is NVIDIA, 2788 San Tomas Expressway, Santa Clara, CA 95051.
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 * 15. ENTIRE AGREEMENT. This license is the final, complete and exclusive agreement between the parties relating to the subject matter of this license and supersedes all prior or contemporaneous understandings and agreements relating to this subject matter, whether oral or written. If any court of competent jurisdiction determines that any provision of this license is illegal, invalid or unenforceable, the remaining provisions will remain in full force and effect. This license may only be modified in a writing signed by an authorized representative of each party.
 *
 * (v. August 20, 2021)
 */
#ifndef _CUDA_PIPELINE
#define _CUDA_PIPELINE

#include "barrier"
#include "atomic"
#include "std/chrono"

_LIBCUDACXX_BEGIN_NAMESPACE_CUDA

    // Forward declaration in barrier of pipeline
    enum class pipeline_role {
        producer,
        consumer
    };

    template<thread_scope _Scope>
    struct __pipeline_stage {
        barrier<_Scope> __produced;
        barrier<_Scope> __consumed;
    };

    template<thread_scope _Scope, uint8_t _Stages_count>
    class pipeline_shared_state {
    public:
        pipeline_shared_state() = default;
        pipeline_shared_state(const pipeline_shared_state &) = delete;
        pipeline_shared_state(pipeline_shared_state &&) = delete;
        pipeline_shared_state & operator=(pipeline_shared_state &&) = delete;
        pipeline_shared_state & operator=(const pipeline_shared_state &) =  delete;

    private:
        __pipeline_stage<_Scope> __stages[_Stages_count];
        atomic<uint32_t, _Scope> __refcount;

        template<thread_scope _Pipeline_scope>
        friend class pipeline;

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state);

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state, size_t __producer_count);

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state, pipeline_role __role);
    };

    struct __pipeline_asm_helper {
        _LIBCUDACXX_DEVICE
        static inline uint32_t __lane_id()
        {
            NV_IF_ELSE_TARGET(
                NV_IS_DEVICE,
                (
                    uint32_t __lane_id;
                    asm volatile ("mov.u32 %0, %%laneid;" : "=r"(__lane_id));
                    return __lane_id;
                ),
                (
                    return 0;
                )
            )
        }
    };

    template<thread_scope _Scope>
    class pipeline {
    public:
        pipeline(pipeline &&) = default;
        pipeline(const pipeline &) = delete;
        pipeline & operator=(pipeline &&) = delete;
        pipeline & operator=(const pipeline &) = delete;

        _LIBCUDACXX_INLINE_VISIBILITY
        ~pipeline()
        {
            if (__active) {
                (void)quit();
            }
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        bool quit()
        {
            bool __elected;
            uint32_t __sub_count;
NV_IF_TARGET(NV_IS_DEVICE,
            const uint32_t __match_mask = __match_any_sync(__activemask(), reinterpret_cast<uintptr_t>(__shared_state_get_refcount()));
            const uint32_t __elected_id = __ffs(__match_mask) - 1;
            __elected = (__pipeline_asm_helper::__lane_id() == __elected_id);
            __sub_count = __popc(__match_mask);
,
            __elected = true;
            __sub_count = 1;
)
            bool __released = false;
            if (__elected) {
                const uint32_t __old = __shared_state_get_refcount()->fetch_sub(__sub_count);
                const bool __last = (__old == __sub_count);
                if (__last) {
                    for (uint8_t __stage = 0; __stage < __stages_count; ++__stage) {
                        __shared_state_get_stage(__stage)->__produced.~barrier();
                        __shared_state_get_stage(__stage)->__consumed.~barrier();
                    }
                    __released = true;
                }
            }
            __active = false;
            return __released;
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void producer_acquire()
        {
            barrier<_Scope> & __stage_barrier = __shared_state_get_stage(__head)->__consumed;
            __stage_barrier.wait_parity(__consumed_phase_parity);
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void producer_commit()
        {
            barrier<_Scope> & __stage_barrier = __shared_state_get_stage(__head)->__produced;
            (void)__memcpy_completion_impl::__defer(__completion_mechanism::__async_group, __single_thread_group{}, 0, __stage_barrier);
            (void)__stage_barrier.arrive();
            if (++__head == __stages_count) {
                __head = 0;
                __consumed_phase_parity = !__consumed_phase_parity;
            }
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void consumer_wait()
        {
            barrier<_Scope> & __stage_barrier = __shared_state_get_stage(__tail)->__produced;
            __stage_barrier.wait_parity(__produced_phase_parity);
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void consumer_release()
        {
            (void)__shared_state_get_stage(__tail)->__consumed.arrive();
            if (++__tail == __stages_count) {
                __tail = 0;
                __produced_phase_parity = !__produced_phase_parity;
            }
        }

        template<class _Rep, class _Period>
        _LIBCUDACXX_INLINE_VISIBILITY
        bool consumer_wait_for(const _CUDA_VSTD::chrono::duration<_Rep, _Period> & __duration)
        {
            barrier<_Scope> & __stage_barrier = __shared_state_get_stage(__tail)->__produced;
            return _CUDA_VSTD::__libcpp_thread_poll_with_backoff(
                        _CUDA_VSTD::__barrier_poll_tester_parity<barrier<_Scope>>(
                            &__stage_barrier,
                            __produced_phase_parity),
                        _CUDA_VSTD::chrono::duration_cast<_CUDA_VSTD::chrono::nanoseconds>(__duration)
            );
        }

        template<class _Clock, class _Duration>
        _LIBCUDACXX_INLINE_VISIBILITY
        bool consumer_wait_until(const _CUDA_VSTD::chrono::time_point<_Clock, _Duration> & __time_point)
        {
            return consumer_wait_for(__time_point - _Clock::now());
        }

    private:
        uint8_t __head               : 8;
        uint8_t __tail               : 8;
        const uint8_t __stages_count : 8;
        bool __consumed_phase_parity : 1;
        bool __produced_phase_parity : 1;
        bool __active                : 1;
        // TODO: Remove partitioned on next ABI break
        const bool __partitioned     : 1;
        char * const __shared_state;


        _LIBCUDACXX_INLINE_VISIBILITY
        pipeline(char * __shared_state, uint8_t __stages_count, bool __partitioned)
            : __head(0)
            , __tail(0)
            , __stages_count(__stages_count)
            , __consumed_phase_parity(true)
            , __produced_phase_parity(false)
            , __active(true)
            , __partitioned(__partitioned)
            , __shared_state(__shared_state)
        {}

        _LIBCUDACXX_INLINE_VISIBILITY
        __pipeline_stage<_Scope> * __shared_state_get_stage(uint8_t __stage)
        {
            ptrdiff_t __stage_offset = __stage * sizeof(__pipeline_stage<_Scope>);
            return reinterpret_cast<__pipeline_stage<_Scope>*>(__shared_state + __stage_offset);
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        atomic<uint32_t, _Scope> * __shared_state_get_refcount()
        {
            ptrdiff_t __refcount_offset = __stages_count * sizeof(__pipeline_stage<_Scope>);
            return reinterpret_cast<atomic<uint32_t, _Scope>*>(__shared_state + __refcount_offset);
        }

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state);

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state, size_t __producer_count);

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state, pipeline_role __role);
    };

    template<class _Group, thread_scope _Scope, uint8_t _Stages_count>
    _LIBCUDACXX_INLINE_VISIBILITY
    pipeline<_Scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Scope, _Stages_count> * __shared_state)
    {
        const uint32_t __group_size = static_cast<uint32_t>(__group.size());
        const uint32_t __thread_rank = static_cast<uint32_t>(__group.thread_rank());

        if (__thread_rank == 0) {
            for (uint8_t __stage = 0; __stage < _Stages_count; ++__stage) {
                init(&__shared_state->__stages[__stage].__consumed, __group_size);
                init(&__shared_state->__stages[__stage].__produced, __group_size);
            }
            __shared_state->__refcount.store(__group_size, std::memory_order_relaxed);
        }
        __group.sync();

        return pipeline<_Scope>(reinterpret_cast<char*>(__shared_state->__stages), _Stages_count, false);
    }

    template<class _Group, thread_scope _Scope, uint8_t _Stages_count>
    _LIBCUDACXX_INLINE_VISIBILITY
    pipeline<_Scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Scope, _Stages_count> * __shared_state, size_t __producer_count)
    {
        const uint32_t __group_size = static_cast<uint32_t>(__group.size());
        const uint32_t __thread_rank = static_cast<uint32_t>(__group.thread_rank());

        if (__thread_rank == 0) {
            const size_t __consumer_count = __group_size - __producer_count;
            for (uint8_t __stage = 0; __stage < _Stages_count; ++__stage) {
                init(&__shared_state->__stages[__stage].__consumed, __consumer_count);
                init(&__shared_state->__stages[__stage].__produced, __producer_count);
            }
            __shared_state->__refcount.store(__group_size, std::memory_order_relaxed);
        }
        __group.sync();

        return pipeline<_Scope>(reinterpret_cast<char*>(__shared_state->__stages), _Stages_count, true);
    }

    template<class _Group, thread_scope _Scope, uint8_t _Stages_count>
    _LIBCUDACXX_INLINE_VISIBILITY
    pipeline<_Scope> make_pipeline(const _Group & __group, pipeline_shared_state<_Scope, _Stages_count> * __shared_state, pipeline_role __role)
    {
        const uint32_t __group_size = static_cast<uint32_t>(__group.size());
        const uint32_t __thread_rank = static_cast<uint32_t>(__group.thread_rank());

        if (__thread_rank == 0) {
            __shared_state->__refcount.store(0, std::memory_order_relaxed);
        }
        __group.sync();

        if (__role == pipeline_role::producer) {
            bool __elected;
            uint32_t __add_count;
NV_IF_TARGET(NV_IS_DEVICE,
            const uint32_t __match_mask = __match_any_sync(__activemask(), reinterpret_cast<uintptr_t>(&__shared_state->__refcount));
            const uint32_t __elected_id = __ffs(__match_mask) - 1;
            __elected = (__pipeline_asm_helper::__lane_id() == __elected_id);
            __add_count = __popc(__match_mask);
,
            __elected = true;
            __add_count = 1;
)
            if (__elected) {
                (void)__shared_state->__refcount.fetch_add(__add_count, std::memory_order_relaxed);
            }
        }
        __group.sync();

        if (__thread_rank == 0) {
            const uint32_t __producer_count = __shared_state->__refcount.load(std::memory_order_relaxed);
            const uint32_t __consumer_count = __group_size - __producer_count;
            for (uint8_t __stage = 0; __stage < _Stages_count; ++__stage) {
                init(&__shared_state->__stages[__stage].__consumed, __consumer_count);
                init(&__shared_state->__stages[__stage].__produced, __producer_count);
            }
            __shared_state->__refcount.store(__group_size, std::memory_order_relaxed);
        }
        __group.sync();

        return pipeline<_Scope>(reinterpret_cast<char*>(__shared_state->__stages), _Stages_count, true);
    }

_LIBCUDACXX_END_NAMESPACE_CUDA

_LIBCUDACXX_BEGIN_NAMESPACE_CUDA_DEVICE

    template<uint8_t _Prior>
    _LIBCUDACXX_DEVICE
    void __pipeline_consumer_wait(pipeline<thread_scope_thread> & __pipeline);

    _LIBCUDACXX_DEVICE
    inline void __pipeline_consumer_wait(pipeline<thread_scope_thread> & __pipeline, uint8_t __prior);

_LIBCUDACXX_END_NAMESPACE_CUDA_DEVICE

_LIBCUDACXX_BEGIN_NAMESPACE_CUDA

    template<>
    class pipeline<thread_scope_thread> {
    public:
        pipeline(pipeline &&) = default;
        pipeline(const pipeline &) = delete;
        pipeline & operator=(pipeline &&) = delete;
        pipeline & operator=(const pipeline &) = delete;

        _LIBCUDACXX_INLINE_VISIBILITY
        ~pipeline() {}

        _LIBCUDACXX_INLINE_VISIBILITY
        bool quit()
        {
            return true;
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void producer_acquire() {}

        _LIBCUDACXX_INLINE_VISIBILITY
        void producer_commit()
        {
NV_IF_TARGET(NV_PROVIDES_SM_80,
            asm volatile ("cp.async.commit_group;");
            ++__head;
)
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void consumer_wait()
        {
NV_IF_TARGET(NV_PROVIDES_SM_80,
            if (__head == __tail) {
                return;
            }

            const uint8_t __prior = __head - __tail - 1;
            device::__pipeline_consumer_wait(*this, __prior);
            ++__tail;
)
        }

        _LIBCUDACXX_INLINE_VISIBILITY
        void consumer_release() {}

        template<class _Rep, class _Period>
        _LIBCUDACXX_INLINE_VISIBILITY
        bool consumer_wait_for(const _CUDA_VSTD::chrono::duration<_Rep, _Period> & __duration)
        {
            (void)__duration;
            consumer_wait();
            return true;
        }

        template<class _Clock, class _Duration>
        _LIBCUDACXX_INLINE_VISIBILITY
        bool consumer_wait_until(const _CUDA_VSTD::chrono::time_point<_Clock, _Duration> & __time_point)
        {
            (void)__time_point;
            consumer_wait();
            return true;
        }

    private:
        uint8_t __head;
        uint8_t __tail;

        _LIBCUDACXX_INLINE_VISIBILITY
        pipeline()
            : __head(0)
            , __tail(0)
        {}

        friend _LIBCUDACXX_INLINE_VISIBILITY inline pipeline<thread_scope_thread> make_pipeline();

        template<uint8_t _Prior>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        void pipeline_consumer_wait_prior(pipeline<thread_scope_thread> & __pipeline);

        template<class _Group, thread_scope _Pipeline_scope, uint8_t _Pipeline_stages_count>
        friend _LIBCUDACXX_INLINE_VISIBILITY
        pipeline<_Pipeline_scope> __make_pipeline(const _Group & __group, pipeline_shared_state<_Pipeline_scope, _Pipeline_stages_count> * __shared_state);
    };

_LIBCUDACXX_END_NAMESPACE_CUDA

_LIBCUDACXX_BEGIN_NAMESPACE_CUDA_DEVICE

    template<uint8_t _Prior>
    _LIBCUDACXX_DEVICE
    void __pipeline_consumer_wait(pipeline<thread_scope_thread> & __pipeline)
    {
        (void)__pipeline;
NV_IF_TARGET(NV_PROVIDES_SM_80,
        constexpr uint8_t __max_prior = 8;

        asm volatile ("cp.async.wait_group %0;"
            :
            : "n"(_Prior < __max_prior ? _Prior : __max_prior));
)
    }

    _LIBCUDACXX_DEVICE
    inline void __pipeline_consumer_wait(pipeline<thread_scope_thread> & __pipeline, uint8_t __prior)
    {
        switch (__prior) {
        case 0:  device::__pipeline_consumer_wait<0>(__pipeline); break;
        case 1:  device::__pipeline_consumer_wait<1>(__pipeline); break;
        case 2:  device::__pipeline_consumer_wait<2>(__pipeline); break;
        case 3:  device::__pipeline_consumer_wait<3>(__pipeline); break;
        case 4:  device::__pipeline_consumer_wait<4>(__pipeline); break;
        case 5:  device::__pipeline_consumer_wait<5>(__pipeline); break;
        case 6:  device::__pipeline_consumer_wait<6>(__pipeline); break;
        case 7:  device::__pipeline_consumer_wait<7>(__pipeline); break;
        default: device::__pipeline_consumer_wait<8>(__pipeline); break;
        }
    }

_LIBCUDACXX_END_NAMESPACE_CUDA_DEVICE

_LIBCUDACXX_BEGIN_NAMESPACE_CUDA

    _LIBCUDACXX_INLINE_VISIBILITY
    inline pipeline<thread_scope_thread> make_pipeline()
    {
        return pipeline<thread_scope_thread>();
    }

    template<uint8_t _Prior>
    _LIBCUDACXX_INLINE_VISIBILITY
    void pipeline_consumer_wait_prior(pipeline<thread_scope_thread> & __pipeline)
    {
        NV_IF_TARGET(NV_PROVIDES_SM_80,
            device::__pipeline_consumer_wait<_Prior>(__pipeline);
            __pipeline.__tail = __pipeline.__head - _Prior;
        )
    }

    template<thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    void pipeline_producer_commit(pipeline<thread_scope_thread> & __pipeline, barrier<_Scope> & __barrier)
    {
        (void)__pipeline;
        NV_IF_TARGET(NV_PROVIDES_SM_80,(
            (void)__memcpy_completion_impl::__defer(__completion_mechanism::__async_group, __single_thread_group{}, 0, __barrier);
        ));
    }

    template<typename _Group, class _Tp, typename _Size, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment __memcpy_async_pipeline(_Group const & __group, _Tp * __destination, _Tp const * __source, _Size __size, pipeline<_Scope> & __pipeline) {
        // 1. Set the completion mechanisms that can be used.
        //
        //    Do not (yet) allow async_bulk_group completion. Do not allow
        //    mbarrier_complete_tx completion, even though it may be possible if
        //    the pipeline has stage barriers in shared memory.
        _CUDA_VSTD::uint32_t __allowed_completions = _CUDA_VSTD::uint32_t(__completion_mechanism::__async_group);

        // Alignment: Use the maximum of the alignment of _Tp and that of a possible cuda::aligned_size_t.
        constexpr _CUDA_VSTD::size_t __size_align = __get_size_align<_Size>::align;
        constexpr _CUDA_VSTD::size_t __align = (alignof(_Tp) < __size_align) ? __size_align : alignof(_Tp);
        // Cast to char pointers. We don't need the type for alignment anymore and
        // erasing the types reduces the number of instantiations of down-stream
        // functions.
        char * __dest_char = reinterpret_cast<char*>(__destination);
        char const * __src_char = reinterpret_cast<char const *>(__source);

        // 2. Issue actual copy instructions.
        auto __cm =  __dispatch_memcpy_async<__align>(__group, __dest_char, __src_char, __size, __allowed_completions);

        // 3. No need to synchronize with copy instructions.
        return __memcpy_completion_impl::__defer(__cm, __group, __size, __pipeline);
    }

    template<typename _Group, class _Type, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(_Group const & __group, _Type * __destination, _Type const * __source, std::size_t __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__group, __destination, __source, __size, __pipeline);
    }

    template<typename _Group, class _Type, std::size_t _Alignment, thread_scope _Scope, std::size_t _Larger_alignment = (alignof(_Type) > _Alignment) ? alignof(_Type) : _Alignment>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(_Group const & __group, _Type * __destination, _Type const * __source, aligned_size_t<_Alignment> __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__group, __destination, __source, __size, __pipeline);
    }

    template<class _Type, typename _Size, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(_Type * __destination, _Type const * __source, _Size __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__single_thread_group{}, __destination, __source, __size, __pipeline);
    }

    template<typename _Group, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(_Group const & __group, void * __destination, void const * __source, std::size_t __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__group, reinterpret_cast<char *>(__destination), reinterpret_cast<char const *>(__source), __size, __pipeline);
    }

    template<typename _Group, std::size_t _Alignment, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(_Group const & __group, void * __destination, void const * __source, aligned_size_t<_Alignment> __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__group, reinterpret_cast<char*>(__destination), reinterpret_cast<char const *>(__source), __size, __pipeline);
    }

    template<typename _Size, thread_scope _Scope>
    _LIBCUDACXX_INLINE_VISIBILITY
    async_contract_fulfillment memcpy_async(void * __destination, void const * __source, _Size __size, pipeline<_Scope> & __pipeline) {
        return __memcpy_async_pipeline(__single_thread_group{}, reinterpret_cast<char*>(__destination), reinterpret_cast<char const *>(__source), __size, __pipeline);
    }

_LIBCUDACXX_END_NAMESPACE_CUDA

#endif //_CUDA_PIPELINE