spec for asm toy interpreter + oo runtime

gistfile1.txt

Asm project idea: mini interpreter

LANGUAGE SPEC

types:
    64-bit int
    64-bit float (?)
    "object"   pointer
    "closure"  pointer
    c pointer (?)
    c function pointer (?)

object data layout:
    ptr ->
        0x0 classinfo ptr
        0x4 refcount
        0x8 user data...

closures are special objects w/ the following layout:
    ptr ->
        0x0 classinfo (classid, argcount, argtypes)
        0x4 refcount
        0x8 function pointer
        0xB bound arguments...

objects are ref counted, allocated from allocator:
    memory blocks: linked list of malloced SOME_SIZE mem chunks, next item
    free list:     linked list of malloced SOME_SIZE free list chunks, next item

    struct MemBlock {
        MemBlock* prev;
        size_t    head = 0;
        ubyte[SIZE] data;
    }
    struct FreeBlock {
        FreeBlock* prev;
        size_t     head = 0;
        ubyte[SIZE] data;
    }
    struct Allocator {
        MemBlock*  allocChain;
        FreeBlock* freeChain;
    }
    naive, but should work ok.
    
Allocator use: separate allocators for
    – 64-bit values (8 bytes) (?)
    – up to 16 byte values
    – up to 32 byte values
    – up to 48 byte values
    – up to 64 byte values
    – up to 128 byte values
    – up to 256 byte values
    – malloc the rest
    – store pointer type in upper bits of refcount (impl refcount as a signed 16-bit integer?)
    
EDIT: this might actually be how malloc() is implemented; should definitely bench first
to see if this approach is worthwhile (I'd hypothesize that it's at _least_ useful for 
small values, and the freelist + allocator per size type might be faster than some implementations;
plus, it would be a worthwhile exercise to implement an allocator anyways).

INSTRUCTION LIST
- integer arithmetic
- floating point arithmetic
- branch
– call address
- dereference / getfield (ptr, offset)
– call pointer (?)
– call method  (object, method index)
– push arg (closure)
– call closure (args from closure ptr)
– alloc obj (incl closure) from classinfo pointer
– retain obj (incl closure)
– release obj (incl closure)