Jed Bytecode

This repo contains a stack-machine based bytecode interpreter for my self-study projects. This will serve as the backend for many of my own languages.

Building

cargo build --release

or use cargo run, I'm not your dad.

Running

There are three commands:

• Compile: convert string Jed Bytecode to Bytecode
• Run: interpret either string Jed Bytecode or Bytecode
• Validate: parse string Jed Bytecode or Bytecode

There are also options, but they do nothing:

• --output, -o: path to the directory to save compiled files
• --debug: print debug statements

To run examples with the built program:

  jed run ./examples/helloworld.jed

or with cargo run:

  cargo run run ./examples/helloworld.jed

Hello World in Jed Bytecode

func main 0
  push_lit "Hello world!"
  call_builtin println
done

Future and Rational

This project is meant to serve as a simple RTS for various languages I decide to explore design-wise in the future. I started this project when I was working on my firstever language 'jed' then once it could finally generate code, I didn't have a backend ready. So, I made a very simple AST crawler runtime that was very annoying. So I wanted to create a bytecode interpreter that I don't have to worry about.

That's what this project is. This is not to replace any other backend, it's for my own exploration of what languages are.

However, since this a love project of mine, there are plenty of times where this is actually faster than CPython.

The Language

I am a Python developer by trade, so I tried to take some inspiration from its bytecode. I don't think I did a very good job of actually doing that, but I enjoy the way it works.

It's bad.

Objects get registered into static memory and never get removed. I...uh... added a deallocator arena but I never drop.

Structure

The VM contains a map of constants, 1 register, an object stack, a call stack, and a memory arena.

The register is referred to as the temp storage.

The call stack gets new frames with each call and each loop in a do_for or do_for_in.

Types

Literals

Type in JBC	Type in Rust
Integer	isize
Float	(isize, usize)
String	&'static [u8]
Bool	bool
Pointer	*mut &'static Object'
List	*const Object, usize
Iterator	(&'static Object, usize)
Nil	-

There is 1 truly internal types: Func. Func is essentially used as more of a "label" to jumping between and forth.

Operations

Operation	Description	Argument	Stack Arguments
bin_op	Apply a binary operation on the top 2	BinOp	2 same-typed operands
call	Call a custom defined function	Function name	Arguments (or not!) required of the function
call_builtin	Call a builtin function (ie println)	Function name	Arguments (or not!) required of the function
push_lit	Push a literal to the stack	Literal	-
push_name	Push a stored local to the stack	Variable name	-
push_temp	Push the temp storage to the stack	-	-
pop	Pop the top element off the stack	-	-
return_if	Return from function call if top element is true	Optional variable name	Bool
store_const	Store a constant with a name	Variable name	Object to store
store_name	Store a variable with a name	Variable name	Object to store
store_temp	Store an object to temp storage	-	Object to store
func	Define a function	Function name, # of args	-
done	Closing delimited for do_for and funcs	-	Return value (if wanted)
exit	Stop and clear VM	-	-
do_for	Loop for x times	-	Positive integer
do_for_in	Loop for len(LIST) times	Name of stored list	-
create_list	Create a list of the top x elements	Number of stack elements	The stack elements to use
list_push	Push onto a list	-	Object, List, Index
list_get	Get from a list	-	List, Index
list_set	Set an index of a list	-	Object, List, Index
push_range	Push int literals from x to y by z	-	Ints: Start, End, Steps
return_if_const	Return from function call with a const	Constant name	Bool
get_ptr	Add a pointer to top object to stack		Any object
read_ptr	Read the value from a pointer		Pointer
set_ptr	Change the data at the pointer		Pointer, any object
get_iter	Get iterable object from list on stack		List
iter_next	Push current index and upcycle iterator		Iterator
iter_prev	Push current index and downcycle iterator		Iterator
iter_skip	Skip n indeces of iterator		Iterator, Integer
iter_current	Push current index		Iterator
iterate	Iterate through an iterator on the stack		Iterator