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