/*
Copyright 2021-2023 Gabriel Jensen.
This file is part of Luma.
Luma is free software: you can redistribute it
and/or modify it under the terms of the GNU
Affero General Public License as published by
the Free Software Foundation, either version 3
of the License, or (at your option) any later
version.
Luma 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
Affero General Public License along with Luma.
If not, see <https://www.gnu.org/licenses/>.
*/
use crate::instruction::Instruction;
use crate::predicate::Predicate;
use crate::shifter::Shifter;
use std::hint::unreachable_unchecked;
impl Instruction {
#[must_use]
pub fn decode_arm(opcode: u32) -> (Self, Predicate) {
use Instruction::*;
use Predicate::*;
let predicate = (opcode & 0b11110000000000000000000000000000).wrapping_shr(0x1C) as u8;
let predicate = Predicate::from_raw(predicate);
return match (opcode & 0b00001110000000000000000000000000).wrapping_shr(0x19) {
0b000 => {
match (opcode & 0b00000000000000000000000000010000).wrapping_shr(0x4) {
0b0 => {
let rd = (opcode & 0b00000000000000001111000000000000).wrapping_shr(0xC) as u8;
let rn = (opcode & 0b00000000000011110000000000000000).wrapping_shr(0x10) as u8;
let s = opcode & 0b00000000000100000000000000000000 != 0x0;
let shifter = Shifter::extract(opcode);
match (opcode & 0b00000001111000000000000000000000).wrapping_shr(0x15) {
0b0000 => (And(rd, rn, shifter, s), predicate),
0b0001 => (Eor(rd, rn, shifter, s), predicate),
0b0010 => (Sub(rd, rn, shifter,s), predicate),
0b0011 => (Rsb(rd, rn, shifter, s), predicate),
0b0100 => (Add(rd, rn, shifter, s), predicate),
0b0101 => (Adc(rd, rn, shifter, s), predicate),
0b0110 => (Sbc(rd, rn, shifter, s), predicate),
0b0111 => (Rsc(rd, rn, shifter, s), predicate),
0b1000 => (Tst(rd, shifter), predicate),
0b1001 => (Teq(rd, shifter), predicate),
0b1010 => (Cmp(rd, shifter), predicate),
0b1011 => (Cmn(rd, shifter), predicate),
0b1100 => (Orr(rd, rn, shifter, s), predicate),
0b1101 => (Mov(rd, shifter, s), predicate),
0b1110 => (Bic(rd, rn, shifter, s), predicate),
0b1111 => (Mvn(rd, shifter, s), predicate),
_ => unsafe { unreachable_unchecked() },
}
},
0b1 => {
match (opcode & 0b00000000000000000000000010000000).wrapping_shr(0x7) {
0b0 => {
match opcode & 0b00000001100100000000000000000000 {
0b00000001000000000000000000000000 => {
let rm = (opcode & 0b00000000000000000000000000001111) as u8;
match (opcode & 0b00000000011000000000000000000000).wrapping_shr(0x13) | (opcode & 0b00000000000000000000000001100000).wrapping_shr(0x5) {
0b0000 => (Undefined, Al),
0b0001 => (Undefined, Al),
0b0010 => (Undefined, Al),
0b0011 => (Undefined, Al),
0b0100 => (Bx(rm), predicate),
0b0101 => (Undefined, Al),
0b0110 => (Undefined, Al),
0b0111 => (Undefined, Al),
0b1000 => (Undefined, Al),
0b1001 => (Undefined, Al),
0b1010 => (Undefined, Al),
0b1011 => (Undefined, Al),
0b1100 => (Undefined, Al),
0b1101 => (Undefined, Al),
0b1110 => (Undefined, Al),
0b1111 => (Undefined, Al),
_ => unsafe { unreachable_unchecked() },
}
},
_ => (Undefined, Al),
}
},
0b1 => (Undefined, Al),
_ => unsafe { unreachable_unchecked() },
}
},
_ => unsafe { unreachable_unchecked() },
}
},
0b001 => {
let rd = (opcode & 0b00000000000000001111000000000000).wrapping_shr(0xC) as u8;
let rn = (opcode & 0b00000000000011110000000000000000).wrapping_shr(0x10) as u8;
let s = opcode & 0b00000000000100000000000000000000 != 0x0;
let shifter = Shifter::extract(opcode);
match (opcode & 0b00000001111000000000000000000000).wrapping_shr(0x15) {
0b0000 => (And(rd, rn, shifter, s), predicate),
0b0001 => (Eor(rd, rn, shifter, s), predicate),
0b0010 => (Sub(rd, rn, shifter, s), predicate),
0b0011 => (Rsb(rd, rn, shifter, s), predicate),
0b0100 => (Add(rd, rn, shifter, s), predicate),
0b0101 => (Adc(rd, rn, shifter, s), predicate),
0b0110 => (Sbc(rd, rn, shifter, s), predicate),
0b0111 => (Rsc(rd, rn, shifter, s), predicate),
0b1000 => (Tst(rn, shifter), predicate),
0b1001 => (Teq(rn, shifter), predicate),
0b1010 => (Cmp(rn, shifter), predicate),
0b1011 => (Cmn(rn, shifter), predicate),
0b1100 => (Orr(rd, rn, shifter, s), predicate),
0b1101 => (Mov(rd, shifter, s), predicate),
0b1110 => (Bic(rd, rn, shifter, s), predicate),
0b1111 => (Mvn(rd, shifter, s), predicate),
_ => unsafe { unreachable_unchecked() },
}
},
0b010 => {
let imm = (opcode & 0b00000000000000000000111111111111) as u16;
let register = (opcode & 0b00000000000000001111000000000000).wrapping_shr(0xC) as u8;
let base = (opcode & 0b00000000000011110000000000000000).wrapping_shr(0x10) as u8;
let l = opcode & 0b00000000000100000000000000000000 != 0x0;
let _w = opcode & 0b00000000001000000000000000000000 != 0x0;
let _b = opcode & 0b00000000010000000000000000000000 != 0x0;
let u = opcode & 0b00000000100000000000000000000000 != 0x0;
let _p = opcode & 0b00000001000000000000000000000000 != 0x0;
let imm = match u {
false => 0x0 - imm as i16,
true => imm as i16,
};
match l {
false => (StoreImmediateOffset(register, base, imm), predicate),
true => (LoadImmediateOffset( register, base, imm), predicate),
}
},
0b011 => (Undefined, Al),
0b100 => (Undefined, Al),
0b101 => {
let offset = opcode & 0b00000000111111111111111111111111;
let offset = (offset << 0x8) as i32 >> 0x6;
let l = opcode & 0b00000001000000000000000000000000 != 0x0;
match l {
false => (B(offset), predicate),
true => (Bl(offset), predicate),
}
},
0b110 => (Undefined, Al),
0b111 => {
match (opcode & 0b00000001000000000000000000000000).wrapping_shr(0x18) {
0b0 => (Undefined, Al),
0b1 => {
let imm = opcode & 0b00000000111111111111111111111111;
(Swi(imm), predicate)
},
_ => unsafe { unreachable_unchecked() },
}
},
_ => unsafe { unreachable_unchecked() },
};
}
}
