Hi all, In the wake of the wowely code Andy Mark and Noah have been producing I want to lift the question of what we can do to compile some delimeted continuation code effeciently.
Delimeted continuations can be looked upon as a generalization of common lisps tagbody e.g. it's trivial to produce tagbody semantics with the help of prompts. Now a quesiton is how we should make sure that most sane code that can be compiled to goto's in the rtl backend really get that far. As I understand the cps compiler is well suited to take on this task. But we should not aim towards atgbody, but also generators and similar constructs. To see what kind of semantics to support maybe the code in https://gitorious.org/guile-coroutines/guile- coroutines/source/fc49d41dfa0cc0647aaeeddf8fb15d55dc2fb6ef:stis/coroutine.scm Can help as well as the example in the same repo, https://gitorious.org/guile-coroutines/guile- coroutines/source/fc49d41dfa0cc0647aaeeddf8fb15d55dc2fb6ef:stis/coroutine/test.scm So what can we do in rtl that we cannot do before? To note here is that in rtl we can basically allocate a region of the register space for e.g. a generator. The nice thing with rtl is that all functions are executed at the end of the register space and therefore we could basically use named gotos to jump between the different generators located at different stack areas. This is not possible in a stack based VM. So not only do we skip expensive function call's but tear down and setup of the stack is not needed. Of cause to be able to take advantage of this not all generators can be used in such a scheme. (It would be nice to get Academic references for this) but it should be doable. We would need some more one more instruction from RTL, namely named gotos. It's also perhaps possible to enlarge the ideas to separate where functions are evaluated and where the "local rigister area" of the generator is situated. E.g. An area allocated from the heap. But this lead to a complete redesign of RTL but it would could be a cool concept. WDYT?
