#| -*-Scheme-*-

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
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    2017, 2018, 2019, 2020, 2021, 2022 Massachusetts Institute of
    Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

MIT/GNU Scheme 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
General Public License for more details.

You should have received a copy of the GNU General Public License
along with MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Control Flow Graph Abstraction

(declare (usual-integrations))

;;;; Editing

(define (snode-delete! snode)
  (let ((next-edge (snode-next-edge snode)))
    (if next-edge
	(begin
	  (edges-replace-right! (node-previous-edges snode)
				(edge-right-node next-edge))
	  (edge-disconnect! next-edge))
	(edges-disconnect-right! (node-previous-edges snode)))))

(define (edge-insert-snode! edge snode)
  (let ((next (edge-right-node edge)))
    (edge-replace-right! edge snode)
    (create-edge! snode set-snode-next-edge! next)))

(define (node-insert-snode! node snode)
  (edges-replace-right! (node-previous-edges node) snode)
  (create-edge! snode set-snode-next-edge! node))

(define-integrable (node-disconnect-on-right! node)
  (edges-disconnect-right! (node-previous-edges node)))

(define (node-disconnect-on-left! node)
  (if (snode? node)
      (snode-disconnect-on-left! node)
      (pnode-disconnect-on-left! node)))

(define (snode-disconnect-on-left! node)
  (let ((edge (snode-next-edge node)))
    (if edge
	(edge-disconnect-left! edge))))

(define (pnode-disconnect-on-left! node)
  (let ((edge (pnode-consequent-edge node)))
    (if edge
	(edge-disconnect-left! edge)))
  (let ((edge (pnode-alternative-edge node)))
    (if edge
	(edge-disconnect-left! edge))))

(define (node-replace! old-node new-node)
  (if (snode? old-node)
      (snode-replace! old-node new-node)
      (pnode-replace! old-node new-node)))

(define (snode-replace! old-node new-node)
  (node-replace-on-right! old-node new-node)
  (snode-replace-on-left! old-node new-node))

(define (pnode-replace! old-node new-node)
  (node-replace-on-right! old-node new-node)
  (pnode-replace-on-left! old-node new-node))

(define-integrable (node-replace-on-right! old-node new-node)
  (edges-replace-right! (node-previous-edges old-node) new-node))

(define (node-replace-on-left! old-node new-node)
  (if (snode? old-node)
      (snode-replace-on-left! old-node new-node)
      (pnode-replace-on-left! old-node new-node)))

(define (snode-replace-on-left! old-node new-node)
  (let ((edge (snode-next-edge old-node)))
    (if edge
	(edge-replace-left! edge new-node set-snode-next-edge!))))

(define (pnode-replace-on-left! old-node new-node)
  (let ((edge (pnode-consequent-edge old-node)))
    (if edge
	(edge-replace-left! edge new-node set-pnode-consequent-edge!)))
  (let ((edge (pnode-alternative-edge old-node)))
    (if edge
	(edge-replace-left! edge new-node set-pnode-alternative-edge!))))

;;;; Previous Connections

(define-integrable (node-previous=0? node)
  (edges=0? (node-previous-edges node)))

(define (edges=0? edges)
  (cond ((null? edges) true)
	((edge-left-node (car edges)) false)
	(else (edges=0? (cdr edges)))))

(define-integrable (node-previous>0? node)
  (edges>0? (node-previous-edges node)))

(define (edges>0? edges)
  (cond ((null? edges) false)
	((edge-left-node (car edges)) true)
	(else (edges>0? (cdr edges)))))

(define-integrable (node-previous=1? node)
  (edges=1? (node-previous-edges node)))

(define (edges=1? edges)
  (if (null? edges)
      false
      ((if (edge-left-node (car edges)) edges=0? edges=1?) (cdr edges))))

(define-integrable (node-previous>1? node)
  (edges>1? (node-previous-edges node)))

(define (edges>1? edges)
  (if (null? edges)
      false
      ((if (edge-left-node (car edges)) edges>0? edges>1?) (cdr edges))))

(define-integrable (node-previous-first node)
  (edges-first-node (node-previous-edges node)))

(define (edges-first-node edges)
  (if (null? edges)
      (error "No first hook")
      (or (edge-left-node (car edges))
	  (edges-first-node (cdr edges)))))

(define (for-each-previous-node node procedure)
  (for-each (lambda (edge)
	      (let ((node (edge-left-node edge)))
		(if node
		    (procedure node))))
	    (node-previous-edges node)))

;;;; Noops

(define-integrable (cfg-node-tag/noop! tag)
  (set-vector-tag-noop! tag true))

(define-integrable (cfg-node-tag/noop? tag)
  (vector-tag-noop tag))

(define-integrable (cfg-node/noop? node)
  (cfg-node-tag/noop? (tagged-vector/tag node)))

(define noop-node-tag
  (let ((tag (make-vector-tag snode-tag 'NOOP false)))
    (cfg-node-tag/noop! tag)
    tag))

(define-integrable (make-noop-node)
  (let ((node (make-snode noop-node-tag)))
    (set! *noop-nodes* (cons node *noop-nodes*))
    node))

(define *noop-nodes*)

(define (cleanup-noop-nodes thunk)
  (fluid-let ((*noop-nodes* '()))
    (let ((value (thunk)))
      (for-each snode-delete! *noop-nodes*)
      value)))

(define (make-false-pcfg)
  (snode->pcfg-false (make-noop-node)))

(define (make-true-pcfg)
  (snode->pcfg-true (make-noop-node)))

;;;; Miscellaneous

(package (with-new-node-marks
	  node-marked?
	  node-mark!)

(define *generation*)

(define-export (with-new-node-marks thunk)
  (fluid-let ((*generation* (make-generation)))
    (thunk)))

(define make-generation
  (let ((generation 0))
    (named-lambda (make-generation)
      (let ((value generation))
	(set! generation (1+ generation))
	value))))

(define-export (node-marked? node)
  (eq? (node-generation node) *generation*))

(define-export (node-mark! node)
  (set-node-generation! node *generation*))

)