blob: 21fdda5d3f6e07076a3a64ca8dabacb65b56c32d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
use super::super::arg::Condition;
/// The struct that represents an A64 conditional branch 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 |
/// | 0 1 0 1 0 1 0 0 0 |
/// | imm19........................................................... cond....... |
/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
///
pub struct BranchCond {
/// The kind of condition to check before branching.
cond: Condition,
/// The instruction offset from this instruction to branch to.
imm19: i32
}
impl BranchCond {
/// B.cond
/// https://developer.arm.com/documentation/ddi0596/2020-12/Base-Instructions/B-cond--Branch-conditionally-
pub fn bcond(cond: Condition, byte_offset: i32) -> Self {
Self { cond, imm19: byte_offset >> 2 }
}
}
/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Branches--Exception-Generating-and-System-instructions?lang=en
const FAMILY: u32 = 0b101;
impl From<BranchCond> for u32 {
/// Convert an instruction into a 32-bit value.
fn from(inst: BranchCond) -> Self {
let imm19 = (inst.imm19 as u32) & ((1 << 19) - 1);
0
| (1 << 30)
| (FAMILY << 26)
| (imm19 << 5)
| (inst.cond as u32)
}
}
impl From<BranchCond> for [u8; 4] {
/// Convert an instruction into a 4 byte array.
fn from(inst: BranchCond) -> [u8; 4] {
let result: u32 = inst.into();
result.to_le_bytes()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_b_eq() {
let result: u32 = BranchCond::bcond(Condition::EQ, 128).into();
assert_eq!(0x54000400, result);
}
#[test]
fn test_b_vs() {
let result: u32 = BranchCond::bcond(Condition::VS, 128).into();
assert_eq!(0x54000406, result);
}
#[test]
fn test_b_ne_neg() {
let result: u32 = BranchCond::bcond(Condition::NE, -128).into();
assert_eq!(0x54fffc01, result);
}
}
|
