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use super::family::Family;
/// The struct that represents an A64 branches and system instruction that can
/// be encoded.
///
/// RET
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
/// | 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 0 1 0 1 1 0 0 1 0 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 |
/// | rn.............. rm.............. |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct BranchesAndSystem {
/// The register holding the address to be branched to.
rn: u8
}
impl BranchesAndSystem {
/// RET
/// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/RET--Return-from-subroutine-?lang=en
pub fn ret(rn: u8) -> Self {
Self { rn }
}
}
impl From<BranchesAndSystem> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: BranchesAndSystem) -> Self {
0
| (0b11 << 30)
| ((Family::BranchesAndSystem as u32) << 25)
| (0b1001011111 << 16)
| ((inst.rn as u32) << 5)
}
}
impl From<BranchesAndSystem> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: BranchesAndSystem) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_ret() {
let inst = BranchesAndSystem::ret(30);
let result: u32 = inst.into();
assert_eq!(0xd65f03C0, result);
}
#[test]
fn test_ret_rn() {
let inst = BranchesAndSystem::ret(20);
let result: u32 = inst.into();
assert_eq!(0xd65f0280, result);
}
}
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