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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2013, 2014, 2015, 2017, 2018 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:
;;;
;;; This pass kills dead expressions: code that has no side effects, and
;;; whose value is unused. It does so by marking all live values, and
;;; then discarding other values as dead. This happens recursively
;;; through procedures, so it should be possible to elide dead
;;; procedures as well.
;;;
;;; Code:
(define-module (language cps type-checks)
#:use-module (ice-9 match)
#:use-module (language cps)
#:use-module (language cps effects-analysis)
#:use-module (language cps types)
#:use-module (language cps intmap)
#:export (elide-type-checks
compute-effects/elide-type-checks))
(define (elide-type-checks conts kfun effects)
"Elide &type-check effects from EFFECTS for the function starting at
KFUN where we can prove that no assertion will be raised at run-time."
(let ((types (infer-types conts kfun)))
(define (visit-primcall effects fx label name param args)
(if (primcall-types-check? types label name param args)
(intmap-replace! effects label (logand fx (lognot &type-check)))
effects))
(persistent-intmap
(intmap-fold (lambda (label types effects)
(let ((fx (intmap-ref effects label)))
(cond
((causes-all-effects? fx) effects)
((causes-effect? fx &type-check)
(match (intmap-ref conts label)
(($ $kargs names vars
($ $continue k src ($ $primcall name param args)))
(visit-primcall effects fx label name param args))
(($ $kargs names vars
($ $branch kf kt src name param args))
(visit-primcall effects fx label name param args))
(_ effects)))
(else effects))))
types
effects))))
(define (compute-effects/elide-type-checks conts)
(intmap-fold (lambda (label cont effects)
(match cont
(($ $kfun) (elide-type-checks conts label effects))
(_ effects)))
conts
(compute-effects conts)))