src/ARMeilleure/Decoders/OpCodeSimdMemSs.cs


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namespace ARMeilleure.Decoders
{
    class OpCodeSimdMemSs : OpCodeMemReg, IOpCodeSimd
    {
        public int SElems { get; }
        public int Index { get; }
        public bool Replicate { get; }
        public bool WBack { get; }

        public new static OpCode Create(InstDescriptor inst, ulong address, int opCode) => new OpCodeSimdMemSs(inst, address, opCode);

        public OpCodeSimdMemSs(InstDescriptor inst, ulong address, int opCode) : base(inst, address, opCode)
        {
            int size = (opCode >> 10) & 3;
            int s = (opCode >> 12) & 1;
            int sElems = (opCode >> 12) & 2;
            int scale = (opCode >> 14) & 3;
            int l = (opCode >> 22) & 1;
            int q = (opCode >> 30) & 1;

            sElems |= (opCode >> 21) & 1;

            sElems++;

            int index = (q << 3) | (s << 2) | size;

            switch (scale)
            {
                case 1:
                    {
                        if ((size & 1) != 0)
                        {
                            Instruction = InstDescriptor.Undefined;

                            return;
                        }

                        index >>= 1;

                        break;
                    }

                case 2:
                    {
                        if ((size & 2) != 0 ||
                           ((size & 1) != 0 && s != 0))
                        {
                            Instruction = InstDescriptor.Undefined;

                            return;
                        }

                        if ((size & 1) != 0)
                        {
                            index >>= 3;

                            scale = 3;
                        }
                        else
                        {
                            index >>= 2;
                        }

                        break;
                    }

                case 3:
                    {
                        if (l == 0 || s != 0)
                        {
                            Instruction = InstDescriptor.Undefined;

                            return;
                        }

                        scale = size;

                        Replicate = true;

                        break;
                    }
            }

            Index = index;
            SElems = sElems;
            Size = scale;

            Extend64 = false;

            WBack = ((opCode >> 23) & 1) != 0;

            RegisterSize = q != 0
                ? RegisterSize.Simd128
                : RegisterSize.Simd64;
        }
    }
}