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Jim Blandy 1992-07-22 16:55:01 +00:00
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61
lisp/emacs-lisp/byte-opt.el
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@ -1,12 +1,16 @@
;;; The optimization passes of the emacs-lisp byte compiler.
;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler.
;;; Copyright (c) 1991 Free Software Foundation, Inc.
;; By Jamie Zawinski <jwz@lucid.com> and Hallvard Furuseth <hbf@ulrik.uio.no>.
;; Author: Jamie Zawinski <jwz@lucid.com>
;; Hallvard Furuseth <hbf@ulrik.uio.no>
;; Keywords: internal
;; This file is part of GNU Emacs.
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 1, or (at your option)
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
@ -18,6 +22,8 @@
;; along with GNU Emacs; see the file COPYING. If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
;;; Commentary:
;;; ========================================================================
;;; "No matter how hard you try, you can't make a racehorse out of a pig.
;;; you can, however, make a faster pig."
@ -69,13 +75,14 @@
;;; but beware of traps like
;;; (cons (list x y) (list x y))
;;;
;;; Tail-recursion elimination is not really possible in elisp. Tail-recursion
;;; elimination is almost always impossible when all variables have dynamic
;;; scope, but given that the "return" byteop requires the binding stack to be
;;; empty (rather than emptying it itself), there can be no truly tail-
;;; recursive elisp functions that take any arguments or make any bindings.
;;; Tail-recursion elimination is not really possible in Emacs Lisp.
;;; Tail-recursion elimination is almost always impossible when all variables
;;; have dynamic scope, but given that the "return" byteop requires the
;;; binding stack to be empty (rather than emptying it itself), there can be
;;; no truly tail-recursive Emacs Lisp functions that take any arguments or
;;; make any bindings.
;;;
;;; Here is an example of an elisp function which could safely be
;;; Here is an example of an Emacs Lisp function which could safely be
;;; byte-compiled tail-recursively:
;;;
;;; (defun tail-map (fn list)
@ -105,7 +112,7 @@
;;; overflow. I don't believe there is any way around this without lexical
;;; scope.
;;;
;;; Wouldn't it be nice if elisp had lexical scope.
;;; Wouldn't it be nice if Emacs Lisp had lexical scope.
;;;
;;; Idea: the form (lexical-scope) in a file means that the file may be
;;; compiled lexically. This proclamation is file-local. Then, within
@ -128,6 +135,7 @@
;;; the board, in the interpreter and compiler, and just FIX all of
;;; the code that relies on dynamic scope of non-defvarred variables.
;;; Code:
(defun byte-compile-log-lap-1 (format &rest args)
(if (aref byte-code-vector 0)
@ -1029,7 +1037,7 @@
(+ (aref bytes ptr)
(progn (setq ptr (1+ ptr))
(lsh (aref bytes ptr) 8))))
((and (>= op byte-rel-goto)
((and (>= op byte-listN)
(<= op byte-insertN))
(setq ptr (1+ ptr)) ;offset in next byte
(aref bytes ptr))))
@ -1060,13 +1068,7 @@
optr ptr
offset (disassemble-offset)) ; this does dynamic-scope magic
(setq op (aref byte-code-vector op))
(cond ((or (memq op byte-goto-ops)
(cond ((memq op byte-rel-goto-ops)
(setq op (aref byte-code-vector
(- (symbol-value op)
(- byte-rel-goto byte-goto))))
(setq offset (+ ptr (- offset 127)))
t)))
(cond ((memq op byte-goto-ops)
;; it's a pc
(setq offset
(cdr (or (assq offset tags)
@ -1176,16 +1178,17 @@
;;; the BOOL variables are, and not perform this optimization on them.
;;;
(defconst byte-boolean-vars
'(abbrevs-changed abbrev-all-caps inverse-video visible-bell
check-protected-fields no-redraw-on-reenter cursor-in-echo-area
noninteractive stack-trace-on-error debug-on-error debug-on-quit
debug-on-next-call insert-default-directory vms-stmlf-recfm
indent-tabs-mode meta-flag load-in-progress defining-kbd-macro
completion-auto-help completion-ignore-case enable-recursive-minibuffers
print-escape-newlines delete-exited-processes parse-sexp-ignore-comments
words-include-escapes pop-up-windows auto-new-screen
reset-terminal-on-clear truncate-partial-width-windows
mode-line-inverse-video)
'(abbrev-all-caps abbrevs-changed byte-metering-on
check-protected-fields completion-auto-help completion-ignore-case
cursor-in-echo-area debug-on-next-call debug-on-quit
defining-kbd-macro delete-exited-processes
enable-recursive-minibuffers indent-tabs-mode
insert-default-directory inverse-video load-in-progress
menu-prompting mode-line-inverse-video no-redraw-on-reenter
noninteractive parse-sexp-ignore-comments pop-up-frames
pop-up-windows print-escape-newlines print-escape-newlines
truncate-partial-width-windows visible-bell vms-stmlf-recfm
words-include-escapes x-save-under)
"DEFVAR_BOOL variables. Giving these any non-nil value sets them to t.
If this does not enumerate all DEFVAR_BOOL variables, the byte-optimizer
may generate incorrect code.")
@ -1721,3 +1724,5 @@ may generate incorrect code.")
byte-optimize-form-code-walker
byte-optimize-lapcode))))
nil)
;;; byte-opt.el ends here