stuff.rs

// Data Processing or PSR transfer
pub fn PSR(cpu: &mut Cpu, opcode: u32) {
  let immediate = as_extra_flag(opcode);
  let set_condition_flags = (opcode & 0x0010_0000) != 0;
  let (rn, rd, _, _, _) = as_usizes(opcode);
  let (_, _, third_byte, second_byte, lowest_byte) = as_bytes(opcode);
  let rn = *cpu.reg_mut(rn);
  let psr_opcode = ((opcode & 0x01E0_0000) >> 25) as u8;
  let op2: u32 = if immediate {
    let ror_shift = second_byte & 0x0007;
    (lowest_byte as u32).rotate_right(ror_shift as u32) // TODO: Im fairly sure this is wrong
  } else {
    let register_value: u32 = cpu.regs[lowest_byte as usize];
    let shift_by_register = (opcode & 0x0000_0010) != 0;
    let shift_amount = if (shift_by_register) {
      cpu.regs[third_byte as usize]
    } else {
      ((third_byte as u32) * 2 + ((second_byte & 0x80) as u32))
    };
    let shift_type = ((opcode & 0x0000_0060) >> 6) as u8;
    match shift_type {
      0 => register_value.overflowing_shl(shift_amount).0,
      1 => register_value.overflowing_shr(shift_amount).0,
      1 => register_value.overflowing_shr(shift_amount).0,
      2 => (register_value as i32).overflowing_shr(shift_amount).0 as u32,
      3 => register_value.rotate_right(shift_amount),
      _ => unimplemented!("Impossible"),
    }
  };
  let mut res = &mut cpu.regs[rd];
  let mut void = 0u32; // For use by tst and teq
  match psr_opcode as u8 {
    0 => {
      *res = rn & op2;
    }
    1 => {
      *res = rn ^ op2;
    }
    2 => {
      *res = rn - op2;
    }
    3 => {
      *res = op2 - rn;
    }
    4 => {
      *res = rn + op2;
    }
    5 => {
      *res = rn + op2 + (cpu.cpsr.C() as u32);
    }
    6 => {
      *res = rn - op2 + (cpu.cpsr.C() as u32) - 1;
    }
    7 => {
      *res = op2 - rn + (cpu.cpsr.C() as u32) - 1;
    }
    8 => {
      res = &mut void;
      //tst
      unimplemented!();
    }
    9 => {
      res = &mut void;
      //teq
      unimplemented!();
    }
    10 => {
      //cmp
      unimplemented!();
    }
    11 => {
      //cmn
      unimplemented!();
    }
    12 => {
      *res = rn | op2;
    }
    13 => {
      *res = op2;
    }
    14 => {
      *res = rn & (!op2);
    }
    15 => {
      *res = !op2;
    }
    _ => unimplemented!("Impossible"),
  }
  if set_condition_flags {
    unimplemented!();
    // TODO: conditions
  }
  cpu.clocks += 0; // todo:clocks
}