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|
/// The size of the operands being operated on.
enum Size {
Size32 = 0b10,
Size64 = 0b11,
}
/// A convenience function so that we can convert the number of bits of an
/// register operand directly into an Sf 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 store instruction that can be encoded.
///
/// STUR
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
/// | 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 0 0 0 0 0 |
/// | size. imm9.......................... rn.............. rt.............. |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct Store {
/// The number of the register to be transferred.
rt: u8,
/// The register holding the memory location.
rn: u8,
/// The optional signed immediate byte offset from the base register.
imm9: i16,
/// The size of the operands being operated on.
size: Size
}
impl Store {
/// STUR (store register, unscaled)
/// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/STUR--Store-Register--unscaled--?lang=en
pub fn stur(rt: u8, rn: u8, imm9: i16, num_bits: u8) -> Self {
Self {
rt,
rn,
imm9,
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<Store> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: Store) -> Self {
let imm9 = (inst.imm9 as u32) & ((1 << 9) - 1);
0
| ((inst.size as u32) << 30)
| (0b11 << 28)
| (FAMILY << 25)
| (imm9 << 12)
| ((inst.rn as u32) << 5)
| (inst.rt as u32)
}
}
impl From<Store> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: Store) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_stur() {
let inst = Store::stur(0, 1, 0, 64);
let result: u32 = inst.into();
assert_eq!(0xf8000020, result);
}
#[test]
fn test_stur_negative_offset() {
let inst = Store::stur(0, 1, -1, 64);
let result: u32 = inst.into();
assert_eq!(0xf81ff020, result);
}
#[test]
fn test_stur_positive_offset() {
let inst = Store::stur(0, 1, 255, 64);
let result: u32 = inst.into();
assert_eq!(0xf80ff020, result);
}
}
|
