a mirroring abstract machine
myr is an abstract machine language and vm intended to be suitable for general code, but in particular reflection-oriented programming.
It is implemented in typescript.
- learn about what is needed to build a vm capable of introspection/reflection and analysis of "running" code
- provide a tiny tool that can be a target for small language projects
myr specifies a tiny stack machine which can be manipulated in a few basic ways.
(The current suite of stack operations is push, pop, swap, and dup.)
There is an arithmetic (add, sub...) and logic (and, or...) suite of instructions.
There are also instructions for loading and storing values in a simple scoped store (store and load).
There are even simple comparisons (cmp, cmp_gt, etc), and a small set of jumps (jump, jump_if_gt...)
There is a suite of instructions around calling functions.
These include call to invoke a function by label, but also includes a mechanism
for dynamically generating code from an ast (compile, useful for lambdas), for invoking functions
dynamically (invoke).
There is also an escape hatch (exec) for calling out to JS for things like console.log. (Note it doesn't
do anything with any values that might be returned from the 'foreign' function yet.)
Instructions can have a number of different static arguments,
and may always have a label.
A label of "main" indicates program execution should begin at that instruction.
| OpCode | Args | Description |
|---|---|---|
| push | value | Places value onto the top of the stack |
| pop | -- | Discard the top element of the stack |
| swap | -- | Juxtapose the two top elements of the stack |
| dup | -- | Take the top stack element and push it ('again', resulting in a copy of the top element placed on the stack) |
| and | -- | Logical and` the top two elements of the stack |
| or | -- | Logical or (top two) |
| not | -- | Unary logical or the top value |
| inc | -- | Increment top stack elem |
| dec | -- | Decrement top stack elem |
| add | -- | Sum of top two elements of the stack |
| sub | -- | Difference of top two elements of the stack |
| mul | -- | Product of top two elements of the stack |
| div | -- | Quotient of top two elements of the stack |
| pow | -- | Power of top two elements of the stack |
| cmp | -- | Compare top two elements of the stack, pushing 0 if equal, 1 if top is greater, -1 if lesser |
| cmp_gt | -- | Compare top two, pushing true if top is greater, false otherwise |
| cmp_lt | -- | Compare top two, pushing true if top is lesser, false otherwise |
| cmp_eq | -- | Compare top two, pushing true if equal, false otherwise |
| jump | target | Unconditional jump to label given by target |
| jump_if_zero | -- | If stack top is zero, jump to label given by target |
| jump_if_gt | -- | If stack top is greater than second from top, jump to label given by target |
| store | key | Store top stack element under key |
| load | key | Load value at key onto stack top |
| call | target | Call function beginning at label target |
| ret | -- | Return from function (pop frame and resume execution) |
| invoke | -- | If stack top is a function, call it (error otherwise) |
| exec | jsMethod, arity | Call out to jsMethod, passing arity variables from stack top |
| compile | body | Call out to external compiler to assemble instructions from AST given in body, pushing the resulting function on the stack |
| arr_get | -- | Top of stack is array, second from top is index |
| arr_put | -- | Top of stack is array, second from top is index, third is value to assign |
| hash_get | -- | Top of stack is hash, second from top is key |
| hash_put | -- | Top of stack is hash, second from top is key, third is value to assign |
| send | key | Retrieve member (if function, call it). Receiver is top of stack, key is message |
| send_eq | key | Assign to member. Value to assign is top of stack, receiver is second |
| construct | -- | Place a 'blank' object onto the top of the stack |
| dump | -- | Utility to echo out the stack |
| mark | -- | Place tombstone on the stack |
| sweep | -- | Pop stack up to and including tombstone (if not found, clears the entire stack!) |
| halt | -- | Hard stop |