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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2013-2021 Free Software Foundation, Inc.
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;; Commentary:
;;;
;;; A pass that replaces free references to recursive functions with
;;; bound references.
;;;
;;; Code:
(define-module (language cps self-references)
#:use-module (ice-9 match)
#:use-module ((srfi srfi-1) #:select (fold))
#:use-module (language cps)
#:use-module (language cps utils)
#:use-module (language cps intmap)
#:use-module (language cps intset)
#:export (resolve-self-references))
(define* (resolve-self-references cps #:optional (label 0) (env empty-intmap))
(define (subst var)
(intmap-ref env var (lambda (var) var)))
(define (rename-exp exp)
(rewrite-exp exp
((or ($ $const) ($ $prim)) ,exp)
(($ $call proc args)
($call (subst proc) ,(map subst args)))
(($ $callk k proc args)
($callk k (and proc (subst proc)) ,(map subst args)))
(($ $calli args callee)
($calli ,(map subst args) (subst callee)))
(($ $primcall name param args)
($primcall name param ,(map subst args)))
(($ $values args)
($values ,(map subst args)))))
(define (rename-term term)
(rewrite-term term
(($ $continue k src exp)
($continue k src ,(rename-exp exp)))
(($ $branch kf kt src op param args)
($branch kf kt src op param ,(map subst args)))
(($ $switch kf kt* src arg)
($switch kf kt* src (subst arg)))
(($ $prompt k kh src escape? tag)
($prompt k kh src escape? (subst tag)))
(($ $throw src op param args)
($throw src op param ,(map subst args)))))
(define (visit-label label cps)
(match (intmap-ref cps label)
(($ $kargs _ _ ($ $continue k src ($ $fun label)))
(resolve-self-references cps label env))
(($ $kargs _ _ ($ $continue k src
($ $rec names vars (($ $fun labels) ...))))
(fold (lambda (label var cps)
(match (intmap-ref cps label)
(($ $kfun src meta self)
(resolve-self-references cps label
(intmap-add env var self)))))
cps labels vars))
(($ $kargs names vars term)
(intmap-replace! cps label
(build-cont ($kargs names vars ,(rename-term term)))))
(_ cps)))
(intset-fold visit-label (compute-function-body cps label) cps))
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