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/*
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::luma::device::{Device, Log};
impl Device {
pub fn arm_branch(&mut self, offset: i32, l: bool) {
// Add the offset to r15 (pc). Conditionally link.
if l { self.arm_link() }
let (address, _) = self.registers[0xF].overflowing_add_signed(offset);
// Add extra offset to move to the new fetch
// instruction.
self.registers[0xF] = address + 0x8;
self.log(Log::Branch, format!("pc => pc{offset:+}+8 ({:#010X})", self.registers[0xF]));
}
pub fn arm_branch_exchange(&mut self, register: u8) {
// Use the address stored in 'register' as the new
// value in r15 (pc).
let value = self.registers[register as usize];
let t = value & 0b00000000000000000000000000000001 != 0x0;
self.cpsr = self.cpsr & 0b11111111111111111111111111011111 | (t as u32) << 0x5;
self.exchange(t);
// Add extra offset to move to the new fetch
// instruction.
let pc_offset: u32 = match t {
false => 0x8,
true => 0x4,
};
self.registers[0xF] = (value & 0b11111111111111111111111111111110) + pc_offset;
self.log(Log::Branch, format!("pc => r{register}{pc_offset:+} ({:#010X})", self.registers[0xF]));
}
pub fn thumb_branch(&mut self, offset: i32) {
let (address, _) = self.registers[0xF].overflowing_add_signed(offset);
self.registers[0xF] = address + 0x4;
self.log(Log::Branch, format!("pc => pc{offset:+}+4 ({:#010X})", self.registers[0xF]));
}
pub fn thumb_branch_exchange(&mut self, register: u8) {
let value = self.registers[register as usize];
let t = value & 0b00000000000000000000000000000001 != 0x0;
self.cpsr = self.cpsr & 0b11111111111111111111111111011111 | (t as u32) << 0x5;
self.exchange(t);
// Add extra offset to move to the new fetch
// instruction.
let pc_offset: u32 = match t {
false => 0x8,
true => 0x4,
};
self.registers[0xF] = (value & 0b11111111111111111111111111111110) + pc_offset;
self.log(Log::Branch, format!("pc => r{register}{pc_offset:+} ({:#010X})", self.registers[0xF]));
}
pub fn thumb_branch_link0(&mut self, offset: i32) {
let (address, _) = self.registers[0xF].overflowing_add_signed(offset);
self.registers[0xE] = address;
self.log(Log::Branch, format!("lr => pc{offset:+}+4 ({:#010X})", self.registers[0xF]));
}
pub fn thumb_branch_link1(&mut self, offset: i32) {
let (address, _) = self.registers[0xE].overflowing_add_signed(offset);
self.thumb_link();
(self.registers[0xF], _) = address.overflowing_add(0x4);
self.log(Log::Branch, format!("pc => pc{offset:+}+4 ({:#010X})", self.registers[0xF]));
}
}
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