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|
/// Which operation to perform for the PC-relative instruction.
enum Op {
/// Form a PC-relative address.
ADR = 0,
/// Form a PC-relative address to a 4KB page.
ADRP = 1
}
/// The struct that represents an A64 PC-relative address instruction that can
/// be encoded.
///
/// ADR
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
/// | 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 0 0 0 0 |
/// | op immlo immhi........................................................... rd.............. |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct PCRelative {
/// The number for the general-purpose register to load the address into.
rd: u8,
/// The number of bytes to add to the PC to form the address.
imm: i32,
/// Which operation to perform for this instruction.
op: Op
}
impl PCRelative {
/// ADR
/// https://developer.arm.com/documentation/ddi0602/2022-03/Base-Instructions/ADR--Form-PC-relative-address-
pub fn adr(rd: u8, imm: i32) -> Self {
Self { rd, imm, op: Op::ADR }
}
/// ADRP
/// https://developer.arm.com/documentation/ddi0602/2022-03/Base-Instructions/ADRP--Form-PC-relative-address-to-4KB-page-
pub fn adrp(rd: u8, imm: i32) -> Self {
Self { rd, imm: imm >> 12, op: Op::ADRP }
}
}
/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Data-Processing----Immediate?lang=en
const FAMILY: u32 = 0b1000;
impl From<PCRelative> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: PCRelative) -> Self {
let immlo = (inst.imm & 0b11) as u32;
let mut immhi = ((inst.imm >> 2) & ((1 << 18) - 1)) as u32;
// Toggle the sign bit if necessary.
if inst.imm < 0 {
immhi |= 1 << 18;
}
0
| ((inst.op as u32) << 31)
| (immlo << 29)
| (FAMILY << 25)
| (immhi << 5)
| inst.rd as u32
}
}
impl From<PCRelative> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: PCRelative) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_adr_positive() {
let inst = PCRelative::adr(0, 5);
let result: u32 = inst.into();
assert_eq!(0x30000020, result);
}
#[test]
fn test_adr_negative() {
let inst = PCRelative::adr(0, -5);
let result: u32 = inst.into();
assert_eq!(0x70ffffc0, result);
}
#[test]
fn test_adrp_positive() {
let inst = PCRelative::adrp(0, 0x4000);
let result: u32 = inst.into();
assert_eq!(0x90000020, result);
}
#[test]
fn test_adrp_negative() {
let inst = PCRelative::adrp(0, -0x4000);
let result: u32 = inst.into();
assert_eq!(0x90ffffe0, result);
}
}
|
