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diff --git a/todo.org b/todo.org new file mode 100644 index 0000000..c0e2188 --- /dev/null +++ b/todo.org @@ -0,0 +1,38 @@ +#+title: TODOs +#+author: Aryadev Chavali +#+date: 2023-11-02 + +* TODO Write a label/jump system :ASM: +Essentially a user should be able to write arbitrary labels (maybe +through ~label x~ or ~x:~ syntax) which can be referred to by ~jump~. + +It'll purely be on the assembler side as a processing step, where the +emitted bytecode purely refers to absolute addresses; the VM should +just be dealing with absolute addresses here. +* TODO Allow relative addresses in jumps :ASM: +As requested, a special syntax for relative address jumps. Sometimes +it's a bit nicer than a label. +* TODO Calling and returning control flow :VM: :ASM: +When writing library code we won't know the addresses of where +callers are jumping from. However, most library functions want to +return control flow back to where the user had called them: we want +the code to act almost like an inline function. + +There are two ways I can think of achieving this: ++ Some extra syntax around labels (something like ~@inline <label>:~) + which tells the assembly processor to inline the label when a "jump" + to that label is given + + This requires no changes to the VM, which keeps it simple, but a + major change to the assembler to be able to inline code. However, + the work on writing a label system and relative addresses should + provide some insight into how this could be possible. ++ A /call stack/ and two new syntactic constructs ~call~ and ~ret~ + which work like so: + + When ~call <label>~ is encountered, the next program address is + pushed onto the call stack and control flow is set to the label + + During execution of the ~<label>~, when a ~ret~ is encountered, + pop an address off the call stack and set control flow to that + address + + This simulates the notion of "calling" and "returning from" a + function in classical languages, but requires more machinery on + the VM side. |