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
>