#| -*-Scheme-*-

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    2017, 2018, 2019 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

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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
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WITHOUT ANY WARRANTY; without even the implied warranty of
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General Public License for more details.

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|#

;;;; Control Flow Graph Abstraction

(declare (usual-integrations))

;;;; Node Datatypes

(define cfg-node-tag (make-vector-tag #f 'CFG-NODE #f))
(define cfg-node? (tagged-vector/subclass-predicate cfg-node-tag))
(define-vector-slots node 1 generation
  subgraph-color potential-control-merge
  alist previous-edges)

(set-vector-tag-description!
 cfg-node-tag
 (lambda (node)
   (descriptor-list node node generation
		    subgraph-color potential-control-merge
		    alist previous-edges)))

(define snode-tag (make-vector-tag cfg-node-tag 'SNODE #f))
(define snode? (tagged-vector/subclass-predicate snode-tag))
(define-vector-slots snode 6 next-edge)

;;; converted to a macro.
;;; (define (make-snode tag . extra)
;;;   (list->vector (cons* tag #f #f #f '() '() #f extra)))

(set-vector-tag-description!
 snode-tag
 (lambda (snode)
   (append! ((vector-tag-description (vector-tag-parent snode-tag)) snode)
	    (descriptor-list snode snode next-edge))))

(define pnode-tag (make-vector-tag cfg-node-tag 'PNODE #f))
(define pnode? (tagged-vector/subclass-predicate pnode-tag))
(define-vector-slots pnode 6 consequent-edge alternative-edge)

;;; converted to a macro.
;;; (define (make-pnode tag . extra)
;;;   (list->vector (cons* tag #f #f #f '() '() #f #f extra)))

(set-vector-tag-description!
 pnode-tag
 (lambda (pnode)
   (append! ((vector-tag-description (vector-tag-parent pnode-tag)) pnode)
	    (descriptor-list pnode pnode consequent-edge alternative-edge))))

(define (add-node-previous-edge! node edge)
  (set-node-previous-edges! node (cons edge (node-previous-edges node))))

(define (delete-node-previous-edge! node edge)
  (set-node-previous-edges! node (delq! edge (node-previous-edges node))))

(define-integrable (snode-next snode)
  (edge-next-node (snode-next-edge snode)))

(define-integrable (pnode-consequent pnode)
  (edge-next-node (pnode-consequent-edge pnode)))

(define-integrable (pnode-alternative pnode)
  (edge-next-node (pnode-alternative-edge pnode)))

(define (cfg-node-get node key)
  (let ((entry (assq key (node-alist node))))
    (and entry
	 (cdr entry))))

(define (cfg-node-put! node key item)
  (let ((entry (assq key (node-alist node))))
    (if entry
	(set-cdr! entry item)
	(set-node-alist! node (cons (cons key item) (node-alist node))))))

(define (cfg-node-remove! node key)
  (set-node-alist! node (del-assq! key (node-alist node))))

;;;; Edge Datatype

(define-structure (edge (type vector))
  left-node
  left-connect
  right-node)

(define (create-edge! left-node left-connect right-node)
  (let ((edge (make-edge left-node left-connect right-node)))
    (if left-node
	(left-connect left-node edge))
    (if right-node
	(add-node-previous-edge! right-node edge))
    edge))

(define-integrable (node->edge node)
  (create-edge! #f #f node))

(define (edge-next-node edge)
  (and edge (edge-right-node edge)))

(define (edge-connect-left! edge left-node left-connect)
  (if (edge-left-node edge)
      (error "Attempt to doubly connect left node of edge" edge))
  (if left-node
      (begin
	(set-edge-left-node! edge left-node)
	(set-edge-left-connect! edge left-connect)
	(left-connect left-node edge))))

(define (edge-connect-right! edge right-node)
  (if (edge-right-node edge)
      (error "Attempt to doubly connect right node of edge" edge))
  (if right-node
      (begin
	(set-edge-right-node! edge right-node)
	(add-node-previous-edge! right-node edge))))

(define (edge-disconnect-left! edge)
  (let ((left-node (edge-left-node edge))
	(left-connect (edge-left-connect edge)))
    (if left-node
	(begin
	  (set-edge-left-node! edge #f)
	  (set-edge-left-connect! edge #f)
	  (left-connect left-node #f)))))

(define (edge-disconnect-right! edge)
  (let ((right-node (edge-right-node edge)))
    (if right-node
	(begin
	  (set-edge-right-node! edge #f)
	  (delete-node-previous-edge! right-node edge)))))

(define (edge-disconnect! edge)
  (edge-disconnect-left! edge)
  (edge-disconnect-right! edge))

(define (edge-replace-left! edge left-node left-connect)
  (edge-disconnect-left! edge)
  (edge-connect-left! edge left-node left-connect))

(define (edge-replace-right! edge right-node)
  (edge-disconnect-right! edge)
  (edge-connect-right! edge right-node))

(define (edges-connect-right! edges right-node)
  (for-each (lambda (edge) (edge-connect-right! edge right-node)) edges))

(define (edges-disconnect-right! edges)
  (for-each edge-disconnect-right! edges))

(define (edges-replace-right! edges right-node)
  (for-each (lambda (edge) (edge-replace-right! edge right-node)) edges))