lilVM

• lilVM is implementation of small virtual machine including tokenizer, parser and vm itself.
• lilVM does not try emulate real hardware or CPU

Running the VM

Either go to lilVM online playground

or run locally:

import { VirtualMachine } from './vm.js';
const vm = new VirtualMachine({ onLog: (value) => {
	 console.info(value) // onLog is called when `PRINT :REGISTER:` is called.
	},
	registerCount: 10, // registers = Int32Array(10) (10 is max)
	memorySize: 1024, // memory = Int32Array(1024)
	maxSteps: 10000, // avoiding infinite loops
});
vm.load(`YOUR CODE HERE`);
vm.run();

Supported instructions

Available registers by default: R0 - R9.

Instruction	:Description
INC RX	Increments value at register RX
DEC RX	Decrements value at register RX
SET :number: RX	Sets decimal number value in register RX
LOAD RA RD	Loads value from memory at address RA (register value) to destination register RD.
LOADIM :number: RD	Loads decimal number value to destination register RD.
STORE RA RV	Stores value to memory at address RA (register value) from value register RV.
EQ RX RY @:label:	Compares RX, RY values and if RX == RY jumps to @:label:
NEQ RX RY @:label:	Compares RX, RY values and if RX != RY jumps to @:label:
LT RX RY @:label:	Compares RX, RY values and if RX < RY jumps to @:label:
LTE RX RY @:label:	Compares RX, RY values and if RX <= RY jumps to @:label:
GT RX RY @:label:	Compares RX, RY values and if RX > RY jumps to @:label:
GTE RX RY @:label:	Compares RX, RY values and if RX >= RY jumps to @:label:
ADD RA RB RC	Adds registers RA, RB. RC = RA + RB
SUB RA RB RC	Subtracts registers RA, RB. RC = RA - RB.
MUL RA RB RC	Integer multiplication of registers RA, RB. RC = RA * RB.
DIV RA RB RC	Integer division of registers RA, RB. RC = RA / RB.
MOD RA RB RC	Mod division of registers RA, RB. RC = RA % RB.

Limitations

• Integer overflows are not handled.
• Supports only integer arithmetic.
• Writing out of bounds memory is undefined behavior.

Example program

SET 0 R0            ; init registers for loop
SET 100 R1

looplab:            ; loop label

STORE R0 R0         ; at addr R0 store R0
INC R0              ; increment R0

NEQ R0 R1 @looplab  ; if R0 != R1 jump