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use super::super::arg::Sf;
/// The struct that represents an A64 signed bitfield move instruction that can
/// be encoded.
///
/// SBFM
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
/// | 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 |
/// | 0 0 1 0 0 1 1 0 |
/// | sf N immr............... imms............... rn.............. rd.............. |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct SBFM {
/// The number for the general-purpose register to load the value into.
rd: u8,
/// The number for the general-purpose register to copy from.
rn: u8,
/// The leftmost bit number to be moved from the source.
imms: u8,
// The right rotate amount.
immr: u8,
/// Whether or not this is a 64-bit operation.
n: bool,
/// The size of this operation.
sf: Sf
}
impl SBFM {
/// ASR
/// https://developer.arm.com/documentation/ddi0596/2020-12/Base-Instructions/ASR--immediate---Arithmetic-Shift-Right--immediate---an-alias-of-SBFM-?lang=en
pub fn asr(rd: u8, rn: u8, shift: u8, num_bits: u8) -> Self {
let (imms, n) = if num_bits == 64 {
(0b111111, true)
} else {
(0b011111, false)
};
Self { rd, rn, immr: shift, imms, n, sf: num_bits.into() }
}
/// SXTW
/// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/SXTW--Sign-Extend-Word--an-alias-of-SBFM-?lang=en
pub fn sxtw(rd: u8, rn: u8) -> Self {
Self { rd, rn, immr: 0, imms: 31, n: true, sf: Sf::Sf64 }
}
}
/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Data-Processing----Immediate?lang=en#bitfield
const FAMILY: u32 = 0b1001;
impl From<SBFM> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: SBFM) -> Self {
let immr = (inst.immr as u32) & ((1 << 6) - 1);
let imms = (inst.imms as u32) & ((1 << 6) - 1);
0
| ((inst.sf as u32) << 31)
| (FAMILY << 25)
| (1 << 24)
| ((inst.n as u32) << 22)
| (immr << 16)
| (imms << 10)
| ((inst.rn as u32) << 5)
| inst.rd as u32
}
}
impl From<SBFM> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: SBFM) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_asr_32_bits() {
let inst = SBFM::asr(0, 1, 2, 32);
let result: u32 = inst.into();
assert_eq!(0x13027c20, result);
}
#[test]
fn test_asr_64_bits() {
let inst = SBFM::asr(10, 11, 5, 64);
let result: u32 = inst.into();
assert_eq!(0x9345fd6a, result);
}
#[test]
fn test_sxtw() {
let inst = SBFM::sxtw(0, 1);
let result: u32 = inst.into();
assert_eq!(0x93407c20, result);
}
}
|
