//--------------------------------------------------------------
// Purpose: Calculates the address to reference for Load/Store instructions
// Returns: The uint value of the address to reference
//--------------------------------------------------------------
private static uint GetLdStoreAddress(LdStore instr)
{
uint refAddress, offset;
if (Memory.ExtractBits(instr.instructionData, 25, 25) == 0)
{
offset = (uint)instr.immediateVal; // immediate offset
}
else
{
offset = BarrelShifter.rotateVal(Computer.GetCPU().registers.ReadWord((uint)(instr.RM * 4)), instr.shiftType, instr.shiftVal); // imm shifted register
}
if (instr.RN * 4 == (int)regs.PC)
{
offset += 4; // to take into account PC reference
}
if (!instr.U)
{
refAddress = Computer.GetCPU().registers.ReadWord((uint)(instr.RN * 4)) - offset;
}
else
{
uint val = Computer.GetCPU().registers.ReadWord((uint)(instr.RN * 4));
refAddress = val + offset;
}
return(refAddress);
}
//--------------------------------------------------------------
// Purpose: Computes the value of operand2 in data processing instructions
// Returns: The uint value of the instruction's operand2
//--------------------------------------------------------------
private static uint ComputeValue(Data instr)
{
op2Type op2 = Operation.CheckOperand2(instr);
shiftType shift = Operation.CheckShiftType(instr);
Memory registers = Computer.GetCPU().registers;
uint value = 0, adjustPC = 0;
if (instr.RM * 4 == (int)regs.PC || instr.RS * 4 == (int)regs.PC)
{
adjustPC = 4;
}
switch (op2)
{
case op2Type.imm:
value = BarrelShifter.rotateVal((uint)instr.immediateVal, (byte)shiftType.ror, (uint)instr.rotateVal * 2);
break;
case op2Type.reg_imm:
value = BarrelShifter.rotateVal(registers.ReadWord((uint)instr.RM * 4) + adjustPC, instr.shiftType, instr.shiftVal);
break;
case op2Type.reg_reg:
value = BarrelShifter.rotateVal(registers.ReadWord((uint)instr.RM * 4) + adjustPC, instr.shiftType, registers.ReadWord((uint)instr.RS * 4) + adjustPC);
break;
}
return(value);
}
private static uint ComputeBranchAddress(Branch instr)
{
uint val = (uint)instr.immediateVal;
uint val2 = val << 8;
uint addr = BarrelShifter.rotateVal((uint)instr.immediateVal << 8, 0x02, 6);
//addr <<= 2;
uint PC = Computer.GetCPU().registers.ReadWord((uint)regs.PC) + 8;
addr += Computer.GetCPU().registers.ReadWord((uint)regs.PC) + 8;
return(addr);
}
