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// Copyright 2024 Gabriel Bjørnager Jensen.
//
// This file is part of Pollex.
//
// Pollex is free software: you can redistribute it
// and/or modify it under the terms of the GNU Af-
// fero General Public License as published by the
// Free Software Foundation, either version 3 of
// the License, or (at your option) any later ver-
// sion.
//
// Pollex is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without
// even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Af-
// fero General Public License along with Pollex.
// If not, see <https://www.gnu.org/licenses/>.
use alloc::borrow::ToOwned;
use crate::Error;
use core::fmt::Display;
use core::mem::transmute;
use core::str::FromStr;
/// An Arm register.
///
/// Some opcodes can only encode specific registers.
/// And yet other opcodes only encode a single register (which is then inferred from the opcode in question).
///
/// # Low registers
///
/// The registers whose identifiers can fit into `3` bits (i.e. registers from `r0` to `r7`, inclusive) are called *low* registers.
///
/// Some instructions (primarily on Thumb) can only encode low registers.
/// In the case of Thumb, a few instructions can be used to move values to and from low registers.
///
/// # High registers
///
/// In contrast to low registers, registers that can only be addressed using `4` bíts are called *high registers*.
///
/// Some instructions are pedantic about combining both low and high registers.
#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
#[repr(u8)]
pub enum Register {
R0 = 0b0000,
R1 = 0b0001,
R2 = 0b0010,
R3 = 0b0011,
R4 = 0b0100,
R5 = 0b0101,
R6 = 0b0110,
R7 = 0b0111,
R8 = 0b1000,
R9 = 0b1001, // Sb
R10 = 0b1010, // Sl
R11 = 0b1011,
R12 = 0b1100, // Ip
Sp = 0b1101, // R13
Lr = 0b1110, // R14
Pc = 0b1111, // R15
}
impl Register {
/// Converts the provided byte into a register identifier.
/// If the byte's value is not a valid identifier, [`None`] is returned.
///
/// This conversion is valid for all `4`-bit values.
#[inline]
#[must_use]
pub const fn from_u8(value: u8) -> Option<Self> {
if value <= 0b1111 {
Some(unsafe { transmute::<u8, Self>(value) })
} else {
None
}
}
/// Checks if the register is a low register.
///
/// That is, it is any of `r0`, `r1`, `r2`, `r3`, `r4`, `r5`, `r6`, or `r7` -- or any alias herof.
/// See also [`is_high`](Self::is_high).
#[inline(always)]
#[must_use]
pub const fn is_low(self) -> bool { (self as u8) <= 0x7 }
/// Checks if the register is a high register.
///
/// That is, it is any of `r8`, `r9`, `r10`, `r11`, `r12`, `sp`, `lr`, or `pc` -- or any alias herof.
/// See also [`is_low`](Self::is_low).
#[inline(always)]
#[must_use]
pub const fn is_high(self) -> bool { (self as u8) > 0x7 }
}
impl Display for Register {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
use Register::*;
match *self {
R0 => write!(f, "r0"),
R1 => write!(f, "r1"),
R2 => write!(f, "r2"),
R3 => write!(f, "r3"),
R4 => write!(f, "r4"),
R5 => write!(f, "r5"),
R6 => write!(f, "r6"),
R7 => write!(f, "r7"),
R8 => write!(f, "r8"),
R9 => write!(f, "r9"),
R10 => write!(f, "r10"),
R11 => write!(f, "r11"),
R12 => write!(f, "r12"),
Sp => write!(f, "sp"),
Lr => write!(f, "lr"),
Pc => write!(f, "pc"),
}
}
}
impl FromStr for Register {
type Err = Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
use Register::*;
match s.to_lowercase().as_str() {
| "r0"
| "a1"
=> Ok(R0),
| "r1"
| "a2"
=> Ok(R1),
| "r2"
| "a3"
=> Ok(R2),
| "r3"
| "a4"
=> Ok(R3),
| "r4"
| "v1"
=> Ok(R4),
| "r5"
| "v2"
=> Ok(R5),
| "r6"
| "v3"
=> Ok(R6),
| "r7"
| "v4"
=> Ok(R7),
| "r8"
| "v5"
=> Ok(R8),
| "r9"
| "sb"
| "v6"
=> Ok(R9),
| "r10"
| "sl"
| "v7"
=> Ok(R10),
| "r11"
| "v8"
=> Ok(R11),
| "ip"
| "r12"
=> Ok(R12),
| "r13"
| "sp"
=> Ok(Sp),
| "lr"
| "r14"
=> Ok(Lr),
| "pc"
| "r15"
=> Ok(Pc),
_ => Err(Error::UnknownRegister(s.to_owned()))
}
}
}
|
