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// Copyright (c) 2025 taitep
// SPDX-License-Identifier: MIT
//
// This file is part of TRVE (https://gitea.taitep.se/taitep/trve)
// See LICENSE file in the project root for full license text.
use crate::{
consts::{Addr, RegId, RegValue},
decode::Instruction,
instructions::find_and_exec,
mem::MemConfig,
};
// placeholder - change when exception system is in place
pub(crate) type Exception = ();
pub(crate) enum InstructionResult {
Normal,
Exception(Exception),
Pause,
}
pub struct Core {
pub(crate) x_regs: [RegValue; 32],
pub(crate) pc: Addr,
pub(crate) mem: MemConfig,
}
impl Core {
pub fn new(mem: MemConfig) -> Self {
Self {
x_regs: [0; 32],
pc: 0,
mem,
}
}
pub fn run(&mut self) {
loop {
let page = (self.pc / 4096) as usize;
let offset = (self.pc % 4096 / 4) as u16;
if !self.pc.is_multiple_of(4) {
//replace eprint with logging, replace break with exception
eprintln!("PC not aligned");
break;
}
let instr = match self.mem.read_word(page, offset) {
Ok(i) => i,
Err(_) => {
eprintln!("Memory access fault while fetching instruction");
break;
}
};
if instr == 0 {
eprintln!("Executing 0 instruction at {:X}", self.pc);
break;
}
assert_eq!(instr & 3, 3, "Compressed instructions not supported");
let instr = Instruction(instr);
let res = find_and_exec(instr, self);
if let Some(res) = res {
match res {
InstructionResult::Normal => {}
InstructionResult::Exception(_e) => {
eprintln!("Exception from instruction");
eprintln!("PC: {:016X}, instr: {:08X}", self.pc, instr.0);
break;
}
InstructionResult::Pause => {
eprintln!("Instruction asked for pause");
break;
}
}
} else {
eprintln!("Invalid Instruction {:08x} at PC: {:x}", instr.0, self.pc);
break;
}
}
}
pub fn reset(&mut self, pc: Addr) {
self.pc = pc;
}
pub(crate) fn reg_read(&self, id: RegId) -> RegValue {
self.x_regs[id as usize]
}
pub(crate) fn reg_write(&mut self, id: RegId, value: RegValue) {
if id == 0 {
return;
}
self.x_regs[id as usize] = value;
}
pub(crate) fn advance_pc(&mut self) {
self.pc = self.pc.wrapping_add(4);
}
}
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