TinyVM

An MVP stack-based bytecode VM

This VM runs a simplistic, Turing complete instruction set.

In ~250 LOC with extensive comments, it's meant to be simple to understand and easily reproducible in languages other than Rust.

It also includes a rudimentary compiler which can execute programs in the test_files folder.

Instructions

Instruction	Description
Push (isize)	Pushes the argument to the top of the stack
Pop	Removes the value on top of the stack
Add	Pops the top two values and pushes their sum
Sub	Pops the top two values and pushes their difference
Mul	Pops the top two values and pushes their product
Div	Pops the top two values and pushes their quotient
Jump (label)	Sets the instruction pointer to the label
JNE (label)	Jumps if the top of the stack is not zero
JE (label)	Jumps if the top of the stack is zero
JGT (label)	Jumps if the top of the stack is greater than zero
JLT (label)	Jumps if the top of the stack is less than zero
JGE (label)	Jumps if the top of the stack is greater than or equal to zero
JLE (label)	Jumps if the top of the stack is less than or equal to zero
Call (procedure)	Calls a procedure, setting the stack offset to the current s stack length
Get (usize)	Gets index of the stack and copies it to the top
Set (usize)	Copies value at the top of the stack to the index
GetArg (usize)	Gets nth argument from top of callstack stack offset, used for procedures
SetArg (usize)	Sets nth argument from top of callstack stack offset, used for procedures
Noop	Doesn't do anything, used by comments to keep instruction pointers correspondent to lines
Print	Prints value at the top of the stack as an integer
PrintC	Prints value at the top of the stack as an ASCII character
PrintStack	Prints the whole stack, used mostly for debugging

You can also set a label with the line label $name, and you can declare a procedure by using Proc $name, Ret, and End. See test_files/procedure.bytecode or test_files/fib_recurse.bytecode for more details.

Examples

In test_files/:

hello_world.bytecode prints "Hello World"

sum.bytecode prints the sum of all integers from 0 to 100

fib.bytecode prints the first 40 fibonacci numbers

fib_recurse.bytecode recursively calculates 35th fibonacci number

Sum

Push 0
Push 0

label loop
    -- [accumulator, index]
    Get 0
    Get 1
    -- [accumulator, index, accumulator, index]
    Add
    -- [accumulator, index, accumulator + index]
    Set 0
    Pop
    -- [accumulator + index, index]

    -- [accumulator, index]
    Incr
    -- [accumulator, index + 1]

    -- [accumulator, index]
    Get 1
    Push 100
    Sub
    -- [accumulator, index, index - 100]
    JNE loop
Pop

Get 0
Print
Push 10
PrintC

> cargo run --release sum.bytecode
4950
>