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opcode: JSR/JSRR

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This commit is contained in:
dogeystamp 2024-01-06 14:32:07 -05:00
parent c137839e86
commit 519fe5a536
Signed by: dogeystamp
GPG Key ID: 7225FE3592EFFA38
1 changed files with 14 additions and 1 deletions
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15
src/vm/instruction.rs
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@ -73,7 +73,7 @@ pub fn execute_instruction(vm: &mut VM, instr: u16) {
OpCode::ADD => todo!("ADD"),
OpCode::LD => op_ld(vm, instr),
OpCode::ST => todo!("ST"),
OpCode::JSR => todo!("JSR"),
OpCode::JSR => op_jsr(vm, instr),
OpCode::AND => todo!("AND"),
OpCode::LDR => op_ldr(vm, instr),
OpCode::STR => todo!("STR"),
@ -131,6 +131,19 @@ fn op_ldr(vm: &mut VM, instr: u16) {
vm.registers.set_reg_with_cond(dr, vm.mem.get_mem(addr));
}
fn op_jsr(vm: &mut VM, instr: u16) {
// this function also includes JSRR
vm.registers.r7 = vm.registers.pc;
if (instr >> 11) & 1 == 0 {
let base_r = (instr >> 6) & 0b111;
vm.registers.pc = vm.registers.get_reg(base_r);
} else {
let offset = sign_extend(instr & 0x7ff, 11);
vm.registers.pc += offset;
}
}
fn op_trap(vm: &mut VM, instr: u16) {
// conform to spec
// (we don't actually need it in this implementation)