public ExecutionResult Execute(Processor cpu, InstructionPackage package)
{
Instruction instruction = package.Instruction;
InstructionData data = package.Data;
Flags flags = cpu.Flags;
Registers r = cpu.Registers;
sbyte offset = (sbyte)(data.Argument1);
ByteRegister register = instruction.Target.AsByteRegister();
bool previousCarry = flags.Carry;
byte original, shifted;
if (register != ByteRegister.None)
{
original = r[register];
shifted = (byte)(original >> 1);
shifted = shifted.SetBit(7, previousCarry);
setFlags(original, shifted, original.GetBit(0));
r[register] = shifted;
}
else
{
ushort address = instruction.Prefix switch
{
0xCB => r.HL,
0xDDCB => (ushort)(r.IX + offset),
0xFDCB => (ushort)(r.IY + offset),
_ => (ushort)0xFFFF
};
original = cpu.Memory.Timed.ReadByteAt(address);
shifted = (byte)(original >> 1);
shifted = shifted.SetBit(7, previousCarry);
setFlags(original, shifted, original.GetBit(0));
if (instruction.IsIndexed)
{
cpu.Timing.InternalOperationCycle(4);
}
cpu.Memory.Timed.WriteByteAt(address, shifted);
if (instruction.CopyResultTo != ByteRegister.None)
{
r[instruction.CopyResultTo.Value] = shifted;
}
}
void setFlags(byte original, byte shifted, bool overflowBit)
{
flags = FlagLookup.BitwiseFlags(original, BitwiseOperation.RotateRightThroughCarry, previousCarry);
flags.Carry = overflowBit;
flags.HalfCarry = false;
flags.Subtract = false;
}
return(new ExecutionResult(package, flags));
}
public ExecutionResult Execute(Processor cpu, InstructionPackage package)
{
Instruction instruction = package.Instruction;
InstructionData data = package.Data;
Flags flags = cpu.Flags;
Registers r = cpu.Registers;
sbyte offset = (sbyte)(data.Argument1);
ByteRegister register = instruction.Target.AsByteRegister();
void setFlags(byte original)
{
flags = FlagLookup.BitwiseFlags(original, BitwiseOperation.ShiftLeftSetBit0, flags.Carry);
flags.Carry = original.GetBit(7);
flags.HalfCarry = false;
flags.Subtract = false;
}
byte original, shifted;
if (register != ByteRegister.None)
{
original = r[register];
shifted = (byte)((original << 1) + 1); // bit 0 is always set, adding 1 does this quicker than calling SetBit
setFlags(original);
r[register] = shifted;
}
else
{
ushort address = instruction.Prefix switch
{
0xCB => r.HL,
0xDDCB => (ushort)(r.IX + offset),
0xFDCB => (ushort)(r.IY + offset),
_ => (ushort)0xFFFF
};
original = cpu.Memory.Timed.ReadByteAt(address);
shifted = (byte)((original << 1) + 1);
setFlags(original);
cpu.Memory.Timed.WriteByteAt(address, shifted);
if (instruction.CopyResultTo != ByteRegister.None)
{
r[instruction.CopyResultTo.Value] = shifted;
}
}
return new ExecutionResult(package, flags);
}
