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/// The size of the register operands to this instruction.
enum Size {
/// Using 32-bit registers.
Size32 = 0b10,
/// Using 64-bit registers.
Size64 = 0b11
}
/// A convenience function so that we can convert the number of bits of an
/// register operand directly into a Size enum variant.
impl From<u8> for Size {
fn from(num_bits: u8) -> Self {
match num_bits {
64 => Size::Size64,
32 => Size::Size32,
_ => panic!("Invalid number of bits: {}", num_bits)
}
}
}
/// The struct that represents an A64 atomic instruction that can be encoded.
///
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
/// | 31 30 29 28 | 27 26 25 24 | 23 22 21 20 | 19 18 17 16 | 15 14 13 12 | 11 10 09 08 | 07 06 05 04 | 03 02 01 00 |
/// | 1 1 1 0 0 0 1 1 1 0 0 0 0 0 0 |
/// | size rs.............. rn.............. rt.............. |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct Atomic {
/// The register holding the value to be loaded.
rt: u8,
/// The base register.
rn: u8,
/// The register holding the data value to be operated on.
rs: u8,
/// The size of the registers used in this instruction.
size: Size
}
impl Atomic {
/// LDADDAL
/// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/LDADD--LDADDA--LDADDAL--LDADDL--Atomic-add-on-word-or-doubleword-in-memory-?lang=en
pub fn ldaddal(rs: u8, rt: u8, rn: u8, num_bits: u8) -> Self {
Self { rt, rn, rs, size: num_bits.into() }
}
}
/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Loads-and-Stores?lang=en
const FAMILY: u32 = 0b0100;
impl From<Atomic> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: Atomic) -> Self {
0
| ((inst.size as u32) << 30)
| (0b11 << 28)
| (FAMILY << 25)
| (0b111 << 21)
| ((inst.rs as u32) << 16)
| ((inst.rn as u32) << 5)
| (inst.rt as u32)
}
}
impl From<Atomic> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: Atomic) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_ldaddal() {
let result: u32 = Atomic::ldaddal(20, 21, 22, 64).into();
assert_eq!(0xf8f402d5, result);
}
}
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