;;;; the definitions of VOPs used for non-local exit (THROW, lexical
;;;; exit, etc.)

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB-VM")

;;; Make a TN for the argument count passing location for a
;;; non-local entry.
(defun make-nlx-entry-arg-start-location ()
  (make-wired-tn *fixnum-primitive-type* immediate-arg-scn ocfp-offset))

;;;; save and restoring the dynamic environment
;;;;
;;;; These VOPs are used in the reentered function to restore the
;;;; appropriate dynamic environment. Currently we only save the
;;;; CURRENT-CATCH and binding stack pointer. We don't need to
;;;; save/restore the current UNWIND-PROTECT, since UNWIND-PROTECTS
;;;; are implicitly processed during unwinding. If there were any
;;;; additional stacks (as e.g. there was an interpreter "eval stack"
;;;; before sbcl-0.7.0), then this would be the place to restore the
;;;; top pointers.

(define-vop (save-dynamic-state)
  (:results (catch :scs (descriptor-reg))
            (nfp :scs (descriptor-reg))
            (nsp :scs (descriptor-reg)))
  (:vop-var vop)
  (:generator 13
    (load-symbol-value catch *current-catch-block*)
    (let ((cur-nfp (current-nfp-tn vop)))
      (when cur-nfp
        (inst mskll cur-nfp 4 nfp)))
    (inst mskll nsp-tn 4 nsp)))

(define-vop (restore-dynamic-state)
  (:args (catch :scs (descriptor-reg))
         (nfp :scs (descriptor-reg))
         (nsp :scs (descriptor-reg)))
  (:vop-var vop)
  (:temporary (:sc any-reg) temp)
  (:generator 10
    (store-symbol-value catch *current-catch-block*)
    (inst mskll nsp-tn 0 temp)
    (let ((cur-nfp (current-nfp-tn vop)))
      (when cur-nfp
        (inst bis nfp temp cur-nfp)))
    (inst bis nsp temp nsp-tn)))

(define-vop (current-stack-pointer)
  (:results (res :scs (any-reg descriptor-reg)))
  (:generator 1
    (move csp-tn res)))

(define-vop (current-binding-pointer)
  (:results (res :scs (any-reg descriptor-reg)))
  (:generator 1
    (move bsp-tn res)))

(define-vop (current-nsp)
  (:results (res :scs (any-reg descriptor-reg)))
  (:generator 1
    (move res nsp-tn)))

(define-vop (set-nsp)
  (:args (nsp :scs (any-reg descriptor-reg)))
  (:generator 1
    (move nsp-tn nsp)))

;;;; unwind block hackery

;;; Compute the address of the catch block from its TN, then store
;;; into the block the current Fp, Env, Unwind-Protect, and the entry PC.
(define-vop (make-unwind-block)
  (:args (tn))
  (:info entry-label)
  (:results (block :scs (any-reg)))
  (:temporary (:scs (descriptor-reg)) temp)
  (:temporary (:scs (non-descriptor-reg)) ndescr)
  (:generator 22
    (inst lda block (* (tn-offset tn) n-word-bytes) cfp-tn)
    (load-symbol-value temp *current-unwind-protect-block*)
    (storew temp block unwind-block-uwp-slot)
    (storew cfp-tn block unwind-block-cfp-slot)
    (storew code-tn block unwind-block-code-slot)
    (inst compute-lra-from-code temp code-tn entry-label ndescr)
    (storew temp block catch-block-entry-pc-slot)))


;;; This is like Make-Unwind-Block, except that we also store in the
;;; specified tag, and link the block into the Current-Catch list.
(define-vop (make-catch-block)
  (:args (tn)
         (tag :scs (any-reg descriptor-reg)))
  (:info entry-label)
  (:results (block :scs (any-reg)))
  (:temporary (:scs (descriptor-reg)) temp)
  (:temporary (:scs (descriptor-reg) :target block :to (:result 0)) result)
  (:temporary (:scs (non-descriptor-reg)) ndescr)
  (:generator 44
    (inst lda result (* (tn-offset tn) n-word-bytes) cfp-tn)
    (load-symbol-value temp *current-unwind-protect-block*)
    (storew temp result catch-block-uwp-slot)
    (storew cfp-tn result catch-block-cfp-slot)
    (storew code-tn result catch-block-code-slot)
    (inst compute-lra-from-code temp code-tn entry-label ndescr)
    (storew temp result catch-block-entry-pc-slot)

    (storew tag result catch-block-tag-slot)
    (load-symbol-value temp *current-catch-block*)
    (storew temp result catch-block-previous-catch-slot)
    (store-symbol-value result *current-catch-block*)

    (move result block)))

;;; Just set the current unwind-protect to UWP. This
;;; instantiates an unwind block as an unwind-protect.
(define-vop (set-unwind-protect)
  (:args (uwp :scs (any-reg)))
  (:generator 7
    (store-symbol-value uwp *current-unwind-protect-block*)))

(define-vop (unlink-catch-block)
  (:temporary (:scs (any-reg)) block)
  (:policy :fast-safe)
  (:translate %catch-breakup)
  (:generator 17
    (load-symbol-value block *current-catch-block*)
    (loadw block block catch-block-previous-catch-slot)
    (store-symbol-value block *current-catch-block*)))

(define-vop (unlink-unwind-protect)
  (:temporary (:scs (any-reg)) block)
  (:policy :fast-safe)
  (:translate %unwind-protect-breakup)
  (:generator 17
    (load-symbol-value block *current-unwind-protect-block*)
    (loadw block block unwind-block-uwp-slot)
    (store-symbol-value block *current-unwind-protect-block*)))

;;;; NLX entry VOPs

(define-vop (nlx-entry)
  (:args (sp) ; Note: we can't list an sc-restriction, 'cause any load vops
              ; would be inserted before the LRA.
         (start)
         (count))
  (:results (values :more t))
  (:temporary (:scs (descriptor-reg)) move-temp)
  (:temporary (:sc non-descriptor-reg) temp)
  (:info label nvals)
  (:save-p :force-to-stack)
  (:vop-var vop)
  (:generator 30
    (emit-return-pc label)
    (note-this-location vop :non-local-entry)
    (cond ((zerop nvals))
          ((= nvals 1)
           (let ((no-values (gen-label)))
             (move null-tn (tn-ref-tn values))
             (inst beq count no-values)
             (loadw (tn-ref-tn values) start)
             (emit-label no-values)))
          (t
           (collect ((defaults))
             (do ((i 0 (1+ i))
                  (tn-ref values (tn-ref-across tn-ref)))
                 ((null tn-ref))
               (let ((default-lab (gen-label))
                     (tn (tn-ref-tn tn-ref)))
                 (defaults (cons default-lab tn))

                 (inst move count temp)
                 (inst lda count (fixnumize -1) count)
                 (inst beq temp default-lab)
                 (sc-case tn
                          ((descriptor-reg any-reg)
                           (loadw tn start i))
                          (control-stack
                           (loadw move-temp start i)
                           (store-stack-tn tn move-temp)))))

             (let ((defaulting-done (gen-label)))

               (emit-label defaulting-done)

               (assemble (:elsewhere)
                 (dolist (def (defaults))
                   (emit-label (car def))
                   (let ((tn (cdr def)))
                     (sc-case tn
                              ((descriptor-reg any-reg)
                               (move null-tn tn))
                              (control-stack
                               (store-stack-tn tn null-tn)))))
                 (inst br zero-tn defaulting-done))))))
    (load-stack-tn csp-tn sp)))

(define-vop (nlx-entry-multiple)
  (:args (top :target dst) (start :target src) (count :target num))
  ;; Again, no SC restrictions for the args, 'cause the loading would
  ;; happen before the entry label.
  (:info label)
  (:temporary (:scs (any-reg) :from (:argument 0)) dst)
  (:temporary (:scs (any-reg) :from (:argument 1)) src)
  (:temporary (:scs (any-reg) :from (:argument 2)) num)
  (:temporary (:scs (descriptor-reg)) temp)
  (:results (new-start) (new-count))
  (:save-p :force-to-stack)
  (:vop-var vop)
  (:generator 30
    (emit-return-pc label)
    (note-this-location vop :non-local-entry)
    (let ((loop (gen-label))
          (done (gen-label)))

      ;; Copy args.
      (load-stack-tn dst top)
      (move start src)
      (move count num)

      ;; Establish results.
      (sc-case new-start
        (any-reg (move dst new-start))
        (control-stack (store-stack-tn new-start dst)))
      (sc-case new-count
        (any-reg (inst move num new-count))
        (control-stack (store-stack-tn new-count num)))
      (inst beq num done)

      ;; Copy stuff on stack.
      (emit-label loop)
      (loadw temp src)
      (inst lda src n-word-bytes src)
      (storew temp dst)
      (inst lda num (fixnumize -1) num)
      (inst lda dst n-word-bytes dst)
      (inst bne num loop)

      (emit-label done)
      (inst move dst csp-tn))))

;;; This VOP is just to force the TNs used in the cleanup onto the stack.
(define-vop (uwp-entry)
  (:info label)
  (:save-p :force-to-stack)
  (:results (block) (start) (count))
  (:ignore block start count)
  (:vop-var vop)
  (:generator 0
    (emit-return-pc label)
    (note-this-location vop :non-local-entry)))
