Andy Wingo <wi...@pobox.com> skribis:
> +;;; Commentary:
> +;;;
> +;;; A pass to adapt expressions to the arities of their continuations,
> +;;; and to rewrite some tail expressions as primcalls to "return".
> +;;;
> +;;; Code:
[...]
> + (define (adapt-exp nvals k exp)
> + (match nvals
> + (0
> + (rewrite-cps-term (lookup-cont k conts)
> + (($ $ktail)
> + ,(let-gensyms (kvoid kunspec unspec)
> + (build-cps-term
> + ($letk* ((kunspec #f ($kargs (unspec) (unspec)
> + ($continue k
> + ($primcall 'return (unspec)))))
> + (kvoid #f ($kargs () ()
> + ($continue kunspec ($void)))))
> + ($continue kvoid ,exp)))))
[...]
> + (let ((drop-result
> + (lambda (kseq)
> + (let-gensyms (k* drop)
> + (build-cps-term
> + ($letk ((k* #f ($kargs ('drop) (drop)
> + ($continue kseq ($values ())))))
> + ($continue k* ,exp)))))))
Are ($void) and ($values ()) both equivalent to *unspecified*?
> + (rewrite-cps-term (lookup-cont k conts)
> + (($ $ktail)
> + ,(rewrite-cps-term exp
> + (($var sym)
> + ($continue ktail ($primcall 'return (sym))))
> + (_
> + ,(let-gensyms (k* v)
> + (build-cps-term
> + ($letk ((k* #f ($kargs (v) (v)
> + ($continue k
> + ($primcall 'return (v))))))
> + ($continue k* ,exp)))))))
> + (($ $ktrunc ($ $arity () () #f () #f) kseq)
> + ,(drop-result kseq))
> + (($ $kargs () () _)
> + ,(drop-result k))
> + (_
> + ($continue k ,exp)))))))
Perhaps that happens in the Tree-IL->CPS pass, but is there/could there
be an effect analysis when truncating multiple-value returns?
Such that (f (values 1 2 3)) reduces to (f 1).
Ludo’.
