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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2014, 2015, 2017 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 simple pass to prune unneeded top-level scopes.
;;;
;;; Code:
(define-module (language cps prune-top-level-scopes)
#:use-module (ice-9 match)
#:use-module (language cps)
#:use-module (language cps utils)
#:use-module (language cps intmap)
#:use-module (language cps intset)
#:export (prune-top-level-scopes))
(define (compute-used-scopes conts)
(persistent-intset
(intmap-fold
(lambda (label cont used-scopes)
(match cont
(($ $kargs _ _
($ $continue k src
($ $primcall 'cached-toplevel-box (scope name bound?))))
(intset-add! used-scopes scope))
(_
used-scopes)))
conts
empty-intset)))
(define (prune-top-level-scopes conts)
(let* ((used-scopes (compute-used-scopes conts)))
(intmap-map
(lambda (label cont)
(match cont
(($ $kargs names vars
($ $continue k src
($ $primcall 'cache-current-module! (scope-id) (module))))
(if (intset-ref used-scopes scope-id)
cont
(build-cont ($kargs names vars
($continue k src ($values ()))))))
(_
cont)))
conts)))
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