Function handle_atomic

crates/virtual-machine/src/cpu/pipeline/memory.rs:349–404

(
    bus: &mut SystemBus,
    reservation: &mut Option<u64>,
    funct5: u8,
    funct3: u8,
    rd: usize,
    addr: u64,
    val: u64,
)

                    .map_err(|_| VmError::LoadAccessFault(addr))?;
                (w as i32) as i64 as u64
            } else {
                bus.read_doubleword(addr)
                    .map_err(|_| VmError::LoadAccessFault(addr))?
            };
            Ok(result)
        }
        // SC
        0x03 => {
            if *reservation == Some(addr) {
                *reservation = None;
                if is_word {
                    bus.write_word(addr, val as u32)
                        .map_err(|_| VmError::StoreAccessFault(addr))?;
                } else {
                    bus.write_doubleword(addr, val)
                        .map_err(|_| VmError::StoreAccessFault(addr))?;
                }
                Ok(0) // success
            } else {
                Ok(1) // failure
            }
        }
        // AMOs
        _ => {
            // Suppress unused rd warning, it's used by the caller
            let _ = rd;
            amo_op(bus, funct5, funct3, addr, val)
        }
    }
}

fn amo_op(
    bus: &mut SystemBus,
    funct5: u8,
    funct3: u8,
    addr: u64,
    val: u64,
) -> Result<u64, VmError> {
    let is_word = funct3 == 2;

    if is_word {
        // 32-bit AMO
        let old_w = bus
            .read_word(addr)
            .map_err(|_| VmError::LoadAccessFault(addr))?;
        let old_i = old_w as i32;
        let val_i = val as i32;

        let new_i: i32 = match funct5 {
            0x00 => old_i.wrapping_add(val_i), // AMOADD.W
            0x01 => val_i,                     // AMOSWAP.W
            0x04 => old_i ^ val_i,             // AMOXOR.W
            0x08 => old_i | val_i,             // AMOOR.W
            0x0C => old_i & val_i,             // AMOAND.W
            0x10 => old_i.min(val_i),          // AMOMIN.W
            0x14 => old_i.max(val_i),          // AMOMAX.W
            0x18 => {
                let old_u = old_w;