//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="L4.IntrinsicKernel"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using StgSharp.Collections;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
using System.Text;
using System.Threading.Tasks;

namespace StgSharp.HighPerformance.Memory
{
    public unsafe partial class L4
    {

        private interface IIntrinsicKernel
        {

            static IIntrinsicKernel Instance { get; } = Create();

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public int ScanEvict(
                       short* pPtr,
                       short* mPtr,
                       int count,
                       L4 owner
            );

            private static IIntrinsicKernel Create()
            {
                if (Sse42.IsSupported)
                {
                    return new SseKernel();
                } else
                {
                    throw new PlatformNotSupportedException("No supported intrinsic kernel found for current platform.");
                }
            }

        }

        private readonly struct SseKernel : IIntrinsicKernel
        {

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public readonly int ScanEvict(
                                short* pPtr,
                                short* mPtr,
                                int count,
                                L4 owner
            )
            {
                int remain = count;
                ConcurrentFlexibleArray<IL4Predict> predictors = owner._predictors;
                predictors.RequestSpanOperation();
                Span<IL4Predict> pSpan = predictors.AsSpan();
                try
                {
                    for (int i = 0; i < CacheLineCount; i += 8)
                    {
                        Vector128<short> p = Sse2.LoadVector128(pPtr + i);
                        Vector128<short> m = Sse2.LoadVector128(mPtr + i);
                        Vector128<short> great = Sse2.CompareGreaterThan(p, m);
                        Vector128<short> le = Sse42.Xor(great, Vector128.Create<short>(-1));

                        int mask = Sse42.MoveMask(le.AsByte());
                        while ((mask != 0) && (remain > 0))
                        {
                            int bit = BitOperations.TrailingZeroCount(mask);
                            int lane = bit >> 1;

                            if (owner.TryEvictAt(i + lane, pSpan)) {
                                remain--;
                            }
                            mask &= mask - 1;
                            mask &= mask - 1;
                        }
                    }
                }
                finally
                {
                    predictors.ReleaseSpanOperation();
                }
                return remain;
            }

        }

    }
}