strat1.scm

;;---------------------------------------------------------------------------
;;
;;  Copyright (c) 2015, Baptiste Saleil. All rights reserved.
;;
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;;  modification, are permitted provided that the following conditions are
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;;      products derived from this software without specific prior written
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;;  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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;;  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
;;  NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
;;  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
;;  NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;;  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
;;  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;
;;---------------------------------------------------------------------------

;; This is the most simple strategy
;; Generate lazy-code objects with given contexts until hard limit is reached
;; Then fallback to a generic version

(define lazy-code-entry? #f)

(define lco_versions (make-table test: eq?))
(define lco_generic  (make-table test: eq?))

;;------------------------------------------------------------------------------
;; PUBLIC

(define (lazy-code-versions lco)
  (let ((versions (table-ref lco_versions lco #f)))
    (or versions
        (let ((versions (make-table)))
          (table-set! lco_versions lco versions)
          versions))))

(define (lazy-code-versions-ctx lco)
  (let ((ctxs (map car (keep cddr (table->list (lazy-code-versions lco))))))
    ctxs))

(define (lazy-code-nb-versions lazy-code)
  (table-length (lazy-code-versions lazy-code)))

(define (lazy-code-nb-real-versions lazy-code)
  (count (table->list (lazy-code-versions lazy-code)) cddr))

(define (strat-get-options)
  strat-options)

;;------------------------------------------------------------------------------
;; PRIVATE

(define opt-max-versions #f) ;; Limit of number of versions (#f=no limit, 0=only generic, ...)
(define opt-regalloc-vers #t)

;; Options specific to this strat
(define strat-options `(
  (--max-versions
    "Set a limit on the number of versions of lazy code objects"
    ,(lambda (args) (set! opt-max-versions (string->number (cadr args)))
                    (set! args (cdr args))
                    args))
  (--disable-regalloc-vers
    "Do not use register allocation information to specialize generated code"
    ,(lambda (args) (set! opt-regalloc-vers #f)
                    (set! get-version nregalloc-get-version)
                    (set! put-version nregalloc-put-version)
                    args))))

(define (lazy-code-generic lco)
  (table-ref lco_generic lco #f))

(define (lazy-code-generic-set! lco ctx version)
  (table-set! lco_generic lco (cons ctx version)))

(define (get-version lazy-code ctx)
  (let* ((key ctx)
         (versions (lazy-code-versions lazy-code))
         (version  (table-ref versions key #f)))
    (and version (cons #f (car version)))))

(define (put-version lazy-code ctx version real-version?)
  (let ((key ctx)
        (versions (lazy-code-versions lazy-code))
        (k (cons version real-version?)))
    (table-set! versions key k)
    k))

;;------------------------------------------------------------------------------
;; !regalloc versioning

(define (version-key ctx)
  (list (ctx-stack ctx)
        (ctx-fs ctx)
        (ctx-ffs ctx)
        (map (lambda (ident) (list (car ident) (identifier-sslots (cdr ident)) (identifier-stype (cdr ident))))
             (ctx-env ctx))))

(define (nregalloc-get-version lazy-code ctx)
  (let* ((key (version-key ctx))
         (versions (lazy-code-versions lazy-code))
         (version  (table-ref versions key #f)))
    (if version
        (cons (car version) (cadr version))
        #f)))

(define (nregalloc-put-version lazy-code ctx version real-version?)
  (let* ((key (version-key ctx))
         (versions (lazy-code-versions lazy-code))
         (k (cons ctx (cons version real-version?))))
    (table-set! versions key k)
    (cdr k)))

;; !regalloc versioning
;;------------------------------------------------------------------------------

(define (strat-label-from-stack lco stack)
  (let ((versions (lazy-code-versions lco)))
    (if versions
        (let loop ((versions (table->list versions)))
          (if (null? versions)
              #f
              (let ((cstack (if opt-regalloc-vers
                                (ctx-stack (caar versions))
                                (caaar versions)))
                    (label  (if opt-regalloc-vers
                                (cadar versions)
                                (caddar versions))))
                (if (equal? cstack stack)
                    label
                    (loop (cdr versions))))))
        #f)))

(define (limit-reached? lco)
  (and opt-max-versions
       (let ((nb-versions (lazy-code-nb-real-versions lco)))
         (>= nb-versions opt-max-versions))))

(define (strat-get-version lco ctx)

  ;; CASE 1: a version exists for this ctx, use it
  (define (case-use-version dst-ctx version)
    (if dst-ctx
        (let ((k (put-version lco ctx #f #f)))
          (list version dst-ctx (lambda (label) (set-car! k label))))
        (list version ctx (lambda (r) r))))

  ;; CASE 2: no version for this ctx, and limit is not reached
  ;; then generate a new version
  (define (case-gen-version)
    (let ((k (put-version lco ctx #f #t)))
      (list #f ctx (lambda (label) (set-car! k label)))))

  ;; CASE 3: no version for this ctx, limit reached, generic exists
  ;; then use the generic version
  (define (case-use-generic generic)
    (let ((callback (lambda (label-merge) (put-version lco ctx label-merge #f))))
      (list (cdr generic) (car generic) callback)))

  ;; CASE 4: no version for this ctx, limit reached, generic does not exist
  ;; then generate the generic version
  (define (case-gen-generic)
    (let* ((gctx (ctx-generic ctx))
           (callback (lambda (label-merge label-version)
                       (put-version lco ctx label-merge #f)
                       (lazy-code-generic-set! lco gctx label-version))))
      (list #f gctx callback)))

  (let* ((r (get-version lco ctx))
         (dst-ctx (and r (car r)))
         (version (and r (cdr r))))

    (if version
        (case-use-version dst-ctx version) ;; CASE 1
        (if (not (limit-reached? lco))
            (case-gen-version)     ;; CASE 2
            (let ((generic (lazy-code-generic lco)))
              (if generic
                  (case-use-generic generic) ;; CASE 3
                  (case-gen-generic)))))))   ;; CASE 4