#| -*-Scheme-*-

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    2017, 2018, 2019, 2020 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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
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|#

;;;; Right (Hand Side) Values
;;; package: (compiler)

(declare (usual-integrations))

(define-root-type rvalue
  %passed-out?)

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

(define-enumeration rvalue-type
  (block
   constant
   expression
   procedure
   reference
   unassigned-test))

(define (rvalue-values rvalue)
  (if (rvalue/reference? rvalue)
      (reference-values rvalue)
      (list rvalue)))

(define (rvalue-passed-in? rvalue)
  (and (rvalue/reference? rvalue)
       (reference-passed-in? rvalue)))

(define (rvalue-passed-out? rvalue)
  (if (rvalue/reference? rvalue)
      (reference-passed-out? rvalue)
      (rvalue-%passed-out? rvalue)))

(define (rvalue-known-value rvalue)
  (if (rvalue/reference? rvalue)
      (reference-known-value rvalue)
      rvalue))

(define (rvalue-known-constant? rvalue)
  (let ((value (rvalue-known-value rvalue)))
    (and value
	 (rvalue/constant? value))))

(define (rvalue-constant-value rvalue)
  (constant-value (rvalue-known-value rvalue)))

(define (rvalue=? rvalue rvalue*)
  (if (rvalue/reference? rvalue)
      (if (rvalue/reference? rvalue*)
	  (lvalue=? (reference-lvalue rvalue) (reference-lvalue rvalue*))
	  (eq? (lvalue-known-value (reference-lvalue rvalue)) rvalue*))
      (if (rvalue/reference? rvalue*)
	  (eq? rvalue (lvalue-known-value (reference-lvalue rvalue*)))
	  (eq? rvalue rvalue*))))

;;;; Constant

(define-rvalue constant
  value)

(define *constants*)

(define (make-constant value)
  (let ((entry (assv value *constants*)))
    (if entry
	(cdr entry)
	(let ((constant (make-rvalue constant-tag value)))
	  (set! *constants* (cons (cons value constant) *constants*))
	  constant))))

(define-vector-tag-unparser constant-tag
  (standard-print-method "LIAR:constant"
    (lambda (constant)
      (list (constant-value constant)))))

(define-integrable (rvalue/constant? rvalue)
  (eq? (tagged-vector/tag rvalue) constant-tag))

;;;; Reference

(define-rvalue reference
  context
  lvalue
  safe?)

(define (make-reference block lvalue safe?)
  (make-rvalue reference-tag block lvalue safe?))

(define-vector-tag-unparser reference-tag
  (standard-print-method "LIAR:reference"
    (lambda (reference)
      (list (variable-name (reference-lvalue reference))))))

(define-integrable (rvalue/reference? rvalue)
  (eq? (tagged-vector/tag rvalue) reference-tag))

(define-integrable (reference-values reference)
  (lvalue-values (reference-lvalue reference)))

(define-integrable (reference-passed-in? reference)
  (lvalue-passed-in? (reference-lvalue reference)))

(define-integrable (reference-passed-out? reference)
  (lvalue-passed-out? (reference-lvalue reference)))

(define-integrable (reference-known-value reference)
  (lvalue-known-value (reference-lvalue reference)))

(define (reference-to-known-location? reference)
  (variable-in-known-location? (reference-context reference)
			       (reference-lvalue reference)))

;;; This type is only important while we use the `unassigned?' special
;;; form to perform optional argument defaulting.  When we switch over
;;; to the new optional argument proposal we can flush this since the
;;; efficiency of this construct won't matter anymore.

(define-rvalue unassigned-test
  context
  lvalue)

(define (make-unassigned-test block lvalue)
  (make-rvalue unassigned-test-tag block lvalue))

(define-vector-tag-unparser unassigned-test-tag
  (standard-print-method "LIAR:unassigned-test"
    (lambda (unassigned-test)
      (list (unassigned-test-lvalue unassigned-test)))))

(define-integrable (rvalue/unassigned-test? rvalue)
  (eq? (tagged-vector/tag rvalue) unassigned-test-tag))

;;;; Expression

(define-rvalue expression
  block
  continuation
  entry-edge
  label
  debugging-info)

(define *expressions*)

(define (make-expression block continuation scfg)
  (let ((expression
	 (make-rvalue expression-tag block continuation
		      (node->edge (cfg-entry-node scfg))
		      (generate-label 'EXPRESSION) #f)))
    (set! *expressions* (cons expression *expressions*))
    (set-block-procedure! block expression)
    expression))

(define-integrable (rvalue/expression? rvalue)
  (eq? (tagged-vector/tag rvalue) expression-tag))

(define-integrable (expression-entry-node expression)
  (edge-next-node (expression-entry-edge expression)))