Re: [VM] Tail recursion and multiple values

[Andy Wingo <wingo@pobox.com>]

Heya,

On Mon 02 Mar 2009 00:48, ludo@gnu.org (Ludovic Courtès) writes:

>>   1) It is expected that you don't have tail recursion between
>>      interpreted and VM code.
>>
>>   2) This particular problem manifests itself in that call-with-values
>>      is VM code (when r5rs.scm is compiled).
>
> (The latter is what I meant to say in my message.)
>
> As for (1), I'm unsure.  The issue is that as long as running code with
> the interpreter is the default, people may hit this kind of problem,
> which is, well, problematic.  Now, I have no idea how this could be
> solved without resorting to dirty hacks such as the one you suggested.

Yeah. It is certainly a counterintuitive situation. The compiler
recognizes both call-with-values and @call-with-values, so we could just
not compile call-with-values; less nasty, but still nasty, and penalizes
the vm in the (apply call-with-values ...) case.

> As a side note, I think it makes sense to keep the interpreter as the
> default when evaluating `.scm' files

Sure, for now -- or we could do what python does, and automatically
create .go files as needed (and if possible). Then it would certainly
pay off over time, and the compilation time would probably be a wash
because in that case the .scm probably isn't even in the disk cache.

> the program is short-lived

This would be the normal case

> if the compiler performs smart optimizations,

Hahaahaha!

More seriously, I think that the bar for including optimizations in the
normal compilation path will be if they actually speed up the compiler
as well (since the compiler is self-compiled).

Cheers,

Andy
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