Function: byte-decompile-bytecode-1

byte-decompile-bytecode-1 is a byte-compiled function defined in byte-opt.el.gz.

Signature

(byte-decompile-bytecode-1 BYTES CONSTVEC &optional MAKE-SPLICEABLE)

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/byte-opt.el.gz
;; As byte-decompile-bytecode, but updates
;; byte-compile-{constants, variables, tag-number}.
;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
;; with `goto's destined for the end of the code.
;; That is for use by the compiler.
;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
;; In that case, we put a pc value into the list
;; before each insn (or its label).
(defun byte-decompile-bytecode-1 (bytes constvec &optional make-spliceable)
  (let ((length (length bytes))
        (bytedecomp-ptr 0) optr tags bytedecomp-op offset
	lap tmp last-constant)
    (while (not (= bytedecomp-ptr length))
      (or make-spliceable
	  (push bytedecomp-ptr lap))
      (setq bytedecomp-op (aref bytes bytedecomp-ptr)
	    optr bytedecomp-ptr
            ;; This uses dynamic-scope magic.
            offset (disassemble-offset bytes))
      (let ((opcode (aref byte-code-vector bytedecomp-op)))
	(cl-assert opcode)
	(setq bytedecomp-op opcode))
      (cond ((memq bytedecomp-op byte-goto-ops)
	     ;; It's a pc.
	     (setq offset
		   (cdr (or (assq offset tags)
                            (let ((new (cons offset (byte-compile-make-tag))))
                              (push new tags)
                              new)))))
	    ((cond ((eq bytedecomp-op 'byte-constant2)
		    (setq bytedecomp-op 'byte-constant) t)
		   ((memq bytedecomp-op byte-constref-ops)))
	     (setq tmp (if (>= offset (length constvec))
			   (list 'out-of-range offset)
			 (aref constvec offset))
		   offset (if (eq bytedecomp-op 'byte-constant)
			      (byte-compile-get-constant tmp)
			    (or (assq tmp byte-compile-variables)
                                (let ((new (list tmp)))
                                  (push new byte-compile-variables)
                                  new)))
                   last-constant tmp))
	    ((eq bytedecomp-op 'byte-stack-set2)
	     (setq bytedecomp-op 'byte-stack-set))
	    ((and (eq bytedecomp-op 'byte-discardN) (>= offset #x80))
	     ;; The top bit of the operand for byte-discardN is a flag,
	     ;; saying whether the top-of-stack is preserved.  In
	     ;; lapcode, we represent this by using a different opcode
	     ;; (with the flag removed from the operand).
	     (setq bytedecomp-op 'byte-discardN-preserve-tos)
	     (setq offset (- offset #x80)))
            ((eq bytedecomp-op 'byte-switch)
             (cl-assert (hash-table-p last-constant) nil
                        "byte-switch used without preceding hash table")
             ;; We cannot use the original hash table referenced in the op,
             ;; so we create a copy of it, and replace the addresses with
             ;; TAGs.
             (let ((orig-table last-constant))
               (setq last-constant (copy-hash-table last-constant))
               ;; Replace all addresses with TAGs.
               (maphash #'(lambda (value offset)
                            (let ((match (assq offset tags)))
                              (puthash value
                                       (if match
                                           (cdr match)
                                         (let ((tag (byte-compile-make-tag)))
                                           (push (cons offset tag) tags)
                                           tag))
                                       last-constant)))
                        last-constant)
               ;; Replace the hash table referenced in the lapcode with our
               ;; modified one.
               (cl-loop for el in-ref lap
                        when (and (listp el) ;; make sure we're at the correct op
                                  (eq (nth 1 el) 'byte-constant)
                                  (eq (nth 2 el) orig-table))
                        ;; Jump tables are never reused, so do this exactly
                        ;; once.
                        do (setf (nth 2 el) last-constant) and return nil))))
      ;; lap = ( [ (pc . (op . arg)) ]* )
      (push (cons optr (cons bytedecomp-op (or offset 0)))
            lap)
      (setq bytedecomp-ptr (1+ bytedecomp-ptr)))
    (let ((rest lap))
      (while rest
	(cond ((numberp (car rest)))
	      ((setq tmp (assq (car (car rest)) tags))
	       ;; This addr is jumped to.
	       (setcdr rest (cons (cons nil (cdr tmp))
				  (cdr rest)))
	       (setq tags (delq tmp tags))
	       (setq rest (cdr rest))))
	(setq rest (cdr rest))))
    (if tags (error "Optimizer error: missed tags %s" tags))
    ;; Remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
    (mapcar (lambda (elt)
              (if (numberp elt)
                  elt
                (cdr elt)))
	    (nreverse lap))))