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+;;; -*- Mode:Emacs-Lisp -*-
+;;; The optimization passes of the emacs-lisp byte compiler.
+
+;; By Jamie Zawinski <jwz@lucid.com> and Hallvard Furuseth <hbf@ulrik.uio.no>.
+;; last modified 29-oct-91.
+
+;; 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)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but 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.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; ========================================================================
+;;; "No matter how hard you try, you can't make a racehorse out of a pig.
+;;; you can, however, make a faster pig."
+;;;
+;;; Or, to put it another way, the emacs byte compiler is a VW Bug.  This code
+;;; makes it be a VW Bug with fuel injection and a turbocharger...  You're 
+;;; still not going to make it go faster than 70 mph, but it might be easier
+;;; to get it there.
+;;;
+
+;;; TO DO:
+;;;
+;;; (apply '(lambda (x &rest y) ...) 1 (foo))
+;;;
+;;; collapse common subexpressions
+;;;
+;;; maintain a list of functions known not to access any global variables
+;;; (actually, give them a 'dynamically-safe property) and then
+;;;   (let ( v1 v2 ... vM vN ) <...dynamically-safe...> )  ==>
+;;;   (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
+;;; by recursing on this, we might be able to eliminate the entire let.
+;;; However certain variables should never have their bindings optimized
+;;; away, because they affect everything.
+;;;   (put 'debug-on-error 'binding-is-magic t)
+;;;   (put 'debug-on-abort 'binding-is-magic t)
+;;;   (put 'inhibit-quit 'binding-is-magic t)
+;;;   (put 'quit-flag 'binding-is-magic t)
+;;; others?
+;;;
+;;; Simple defsubsts often produce forms like
+;;;    (let ((v1 (f1)) (v2 (f2)) ...)
+;;;       (FN v1 v2 ...))
+;;; It would be nice if we could optimize this to 
+;;;    (FN (f1) (f2) ...)
+;;; but we can't unless FN is dynamically-safe (it might be dynamically
+;;; referring to the bindings that the lambda arglist established.)
+;;; One of the uncountable lossages introduced by dynamic scope...
+;;;
+;;; Maybe there should be a control-structure that says "turn on 
+;;; fast-and-loose type-assumptive optimizations here."  Then when
+;;; we see a form like (car foo) we can from then on assume that
+;;; the variable foo is of type cons, and optimize based on that.
+;;; But, this won't win much because of (you guessed it) dynamic 
+;;; scope.  Anything down the stack could change the value.
+;;;
+;;; It would be nice if redundant sequences could be factored out as well,
+;;; when they are known to have no side-effects:
+;;;   (list (+ a b c) (+ a b c))   -->  a b add c add dup list-2
+;;; 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.
+;;;
+;;; Here is an example of an elisp function which could safely be
+;;; byte-compiled tail-recursively:
+;;;
+;;;  (defun tail-map (fn list)
+;;;    (cond (list
+;;;           (funcall fn (car list))
+;;;           (tail-map fn (cdr list)))))
+;;;
+;;; However, if there was even a single let-binding around the COND,
+;;; it could not be byte-compiled, because there would be an "unbind"
+;;; byte-op between the final "call" and "return."  Adding a 
+;;; Bunbind_all byteop would fix this.
+;;;
+;;;   (defun foo (x y z) ... (foo a b c))
+;;;   ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
+;;;   ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
+;;;   ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
+;;;
+;;; this also can be considered tail recursion:
+;;;
+;;;   ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
+;;; could generalize this by doing the optimization
+;;;   (goto X) ... X: (return)  -->  (return)
+;;;
+;;; But this doesn't solve all of the problems: although by doing tail-
+;;; recursion elimination in this way, the call-stack does not grow, the
+;;; binding-stack would grow with each recursive step, and would eventually
+;;; overflow.  I don't believe there is any way around this without lexical
+;;; scope.
+;;;
+;;; Wouldn't it be nice if elisp 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 
+;;; that file, "let" would establish lexical bindings, and "let-dynamic"
+;;; would do things the old way.  (Or we could use CL "declare" forms.)
+;;; We'd have to notice defvars and defconsts, since those variables should
+;;; always be dynamic, and attempting to do a lexical binding of them
+;;; should simply do a dynamic binding instead.
+;;; But!  We need to know about variables that were not necessarily defvarred
+;;; in the file being compiled (doing a boundp check isn't good enough.)
+;;; Fdefvar() would have to be modified to add something to the plist.
+;;;
+;;; A major disadvantage of this scheme is that the interpreter and compiler 
+;;; would have different semantics for files compiled with (dynamic-scope).  
+;;; Since this would be a file-local optimization, there would be no way to
+;;; modify the interpreter to obey this (unless the loader was hacked 
+;;; in some grody way, but that's a really bad idea.)
+;;;
+;;; Really the Right Thing is to make lexical scope the default across
+;;; the board, in the interpreter and compiler, and just FIX all of 
+;;; the code that relies on dynamic scope of non-defvarred variables.
+
+
+(require 'byte-compile "bytecomp")
+
+(or (fboundp 'byte-compile-lapcode)
+    (error "loading bytecomp got the wrong version of the compiler."))
+
+(defun byte-compile-log-lap-1 (format &rest args)
+  (if (aref byte-code-vector 0)
+      (error "The old version of the disassembler is loaded.  Reload new-bytecomp as well."))
+  (byte-compile-log-1
+   (apply 'format format
+     (let (c a)
+       (mapcar '(lambda (arg)
+		  (if (not (consp arg))
+		      (if (and (symbolp arg)
+			       (string-match "^byte-" (symbol-name arg)))
+			  (intern (substring (symbol-name arg) 5))
+			arg)
+		    (if (integerp (setq c (car arg)))
+			(error "non-symbolic byte-op %s" c))
+		    (if (eq c 'TAG)
+			(setq c arg)
+		      (setq a (cond ((memq c byte-goto-ops)
+				     (car (cdr (cdr arg))))
+				    ((memq c byte-constref-ops)
+				     (car (cdr arg)))
+				    (t (cdr arg))))
+		      (setq c (symbol-name c))
+		      (if (string-match "^byte-." c)
+			  (setq c (intern (substring c 5)))))
+		    (if (eq c 'constant) (setq c 'const))
+		    (if (and (eq (cdr arg) 0)
+			     (not (memq c '(unbind call const))))
+			c
+		      (format "(%s %s)" c a))))
+	       args)))))
+
+(defmacro byte-compile-log-lap (format-string &rest args)
+  (list 'and
+	'(memq byte-optimize-log '(t byte))
+	(cons 'byte-compile-log-lap-1
+	      (cons format-string args))))
+
+
+;;; byte-compile optimizers to support inlining
+
+(put 'inline 'byte-optimizer 'byte-optimize-inline-handler)
+
+(defun byte-optimize-inline-handler (form)
+  "byte-optimize-handler for the `inline' special-form."
+  (cons 'progn
+	(mapcar
+	 '(lambda (sexp)
+	    (let ((fn (car-safe sexp)))
+	      (if (and (symbolp fn)
+		    (or (cdr (assq fn byte-compile-function-environment))
+		      (and (fboundp fn)
+			(not (or (cdr (assq fn byte-compile-macro-environment))
+				 (and (consp (setq fn (symbol-function fn)))
+				      (eq (car fn) 'macro))
+				 (subrp fn))))))
+		  (byte-compile-inline-expand sexp)
+		sexp)))
+	 (cdr form))))
+
+
+(defun byte-inline-lapcode (lap)
+  "splice the given lap code into the current instruction stream.
+If it has any labels in it, you're responsible for making sure there
+are no collisions, and that byte-compile-tag-number is reasonable
+after this is spliced in.  the provided list is destroyed."
+  (setq byte-compile-output (nconc (nreverse lap) byte-compile-output)))
+
+
+(defun byte-compile-inline-expand (form)
+  (let* ((name (car form))
+	 (fn (or (cdr (assq name byte-compile-function-environment))
+		 (and (fboundp name) (symbol-function name)))))
+    (if (null fn)
+	(progn
+	  (byte-compile-warn "attempt to inline %s before it was defined" name)
+	  form)
+      ;; else
+      (if (and (consp fn) (eq (car fn) 'autoload))
+	  (load (nth 1 fn)))
+      (if (and (consp fn) (eq (car fn) 'autoload))
+	  (error "file \"%s\" didn't define \"%s\"" (nth 1 fn) name))
+      (if (symbolp fn)
+	  (byte-compile-inline-expand (cons fn (cdr form)))
+	(if (compiled-function-p fn)
+	    (cons (list 'lambda (aref fn 0)
+			(list 'byte-code (aref fn 1) (aref fn 2) (aref fn 3)))
+		  (cdr form))
+	  (if (not (eq (car fn) 'lambda)) (error "%s is not a lambda" name))
+	  (cons fn (cdr form)))))))
+
+;;; ((lambda ...) ...)
+;;; 
+(defun byte-compile-unfold-lambda (form &optional name)
+  (or name (setq name "anonymous lambda"))
+  (let ((lambda (car form))
+	(values (cdr form)))
+    (if (compiled-function-p lambda)
+	(setq lambda (list 'lambda (nth 0 form)
+			   (list 'byte-code
+				 (nth 1 form) (nth 2 form) (nth 3 form)))))
+    (let ((arglist (nth 1 lambda))
+	  (body (cdr (cdr lambda)))
+	  optionalp restp
+	  bindings)
+      (if (and (stringp (car body)) (cdr body))
+	  (setq body (cdr body)))
+      (if (and (consp (car body)) (eq 'interactive (car (car body))))
+	  (setq body (cdr body)))
+      (while arglist
+	(cond ((eq (car arglist) '&optional)
+	       ;; ok, I'll let this slide because funcall_lambda() does...
+	       ;; (if optionalp (error "multiple &optional keywords in %s" name))
+	       (if restp (error "&optional found after &rest in %s" name))
+	       (if (null (cdr arglist))
+		   (error "nothing after &optional in %s" name))
+	       (setq optionalp t))
+	      ((eq (car arglist) '&rest)
+	       ;; ...but it is by no stretch of the imagination a reasonable
+	       ;; thing that funcall_lambda() allows (&rest x y) and
+	       ;; (&rest x &optional y) in arglists.
+	       (if (null (cdr arglist))
+		   (error "nothing after &rest in %s" name))
+	       (if (cdr (cdr arglist))
+		   (error "multiple vars after &rest in %s" name))
+	       (setq restp t))
+	      (restp
+	       (setq bindings (cons (list (car arglist)
+					  (and values (cons 'list values)))
+				    bindings)
+		     values nil))
+	      ((and (not optionalp) (null values))
+	       (byte-compile-warn "attempt to open-code %s with too few arguments" name)
+	       (setq arglist nil values 'too-few))
+	      (t
+	       (setq bindings (cons (list (car arglist) (car values))
+				    bindings)
+		     values (cdr values))))
+	(setq arglist (cdr arglist)))
+      (if values
+	  (progn
+	    (or (eq values 'too-few)
+		(byte-compile-warn
+		 "attempt to open-code %s with too many arguments" name))
+	    form)
+	(let ((newform 
+	       (if bindings
+		   (cons 'let (cons (nreverse bindings) body))
+		 (cons 'progn body))))
+	  (byte-compile-log "  %s\t==>\t%s" form newform)
+	  newform)))))
+
+
+;;; implementing source-level optimizers
+
+(defun byte-optimize-form-code-walker (form for-effect)
+  ;;
+  ;; For normal function calls, We can just mapcar the optimizer the cdr.  But
+  ;; we need to have special knowledge of the syntax of the special forms
+  ;; like let and defun (that's why they're special forms :-).  (Actually,
+  ;; the important aspect is that they are subrs that don't evaluate all of
+  ;; their args.)
+  ;;
+  (let ((fn (car-safe form))
+	tmp)
+    (cond ((not (consp form))
+	   (if (not (and for-effect
+			 (or byte-compile-delete-errors
+			     (not (symbolp form))
+			     (eq form t))))
+	     form))
+	  ((eq fn 'quote)
+	   (if (cdr (cdr form))
+	       (byte-compile-warn "malformed quote form: %s"
+				  (prin1-to-string form)))
+	   ;; map (quote nil) to nil to simplify optimizer logic.
+	   ;; map quoted constants to nil if for-effect (just because).
+	   (and (nth 1 form)
+		(not for-effect)
+		form))
+	  ((or (compiled-function-p fn)
+	       (eq 'lambda (car-safe fn)))
+	   (byte-compile-unfold-lambda form))
+	  ((memq fn '(let let*))
+	   ;; recursively enter the optimizer for the bindings and body
+	   ;; of a let or let*.  This for depth-firstness: forms that
+	   ;; are more deeply nested are optimized first.
+	   (cons fn
+	     (cons
+	      (mapcar '(lambda (binding)
+			 (if (symbolp binding)
+			     binding
+			   (if (cdr (cdr binding))
+			       (byte-compile-warn "malformed let binding: %s"
+						  (prin1-to-string binding)))
+			   (list (car binding)
+				 (byte-optimize-form (nth 1 binding) nil))))
+		      (nth 1 form))
+	      (byte-optimize-body (cdr (cdr form)) for-effect))))
+	  ((eq fn 'cond)
+	   (cons fn
+		 (mapcar '(lambda (clause)
+			    (if (consp clause)
+				(cons
+				 (byte-optimize-form (car clause) nil)
+				 (byte-optimize-body (cdr clause) for-effect))
+			      (byte-compile-warn "malformed cond form: %s"
+						 (prin1-to-string clause))
+			      clause))
+			 (cdr form))))
+	  ((eq fn 'progn)
+	   ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
+	   (if (cdr (cdr form))
+	       (progn
+		 (setq tmp (byte-optimize-body (cdr form) for-effect))
+		 (if (cdr tmp) (cons 'progn tmp) (car tmp)))
+	     (byte-optimize-form (nth 1 form) for-effect)))
+	  ((eq fn 'prog1)
+	   (if (cdr (cdr form))
+	       (cons 'prog1
+		     (cons (byte-optimize-form (nth 1 form) for-effect)
+			   (byte-optimize-body (cdr (cdr form)) t)))
+	     (byte-optimize-form (nth 1 form) for-effect)))
+	  ((eq fn 'prog2)
+	   (cons 'prog2
+	     (cons (byte-optimize-form (nth 1 form) t)
+	       (cons (byte-optimize-form (nth 2 form) for-effect)
+		     (byte-optimize-body (cdr (cdr (cdr form))) t)))))
+	  
+	  ((memq fn '(save-excursion save-restriction))
+	   ;; those subrs which have an implicit progn; it's not quite good
+	   ;; enough to treat these like normal function calls.
+	   ;; This can turn (save-excursion ...) into (save-excursion) which
+	   ;; will be optimized away in the lap-optimize pass.
+	   (cons fn (byte-optimize-body (cdr form) for-effect)))
+	  
+	  ((eq fn 'with-output-to-temp-buffer)
+	   ;; this is just like the above, except for the first argument.
+	   (cons fn
+	     (cons
+	      (byte-optimize-form (nth 1 form) nil)
+	      (byte-optimize-body (cdr (cdr form)) for-effect))))
+	  
+	  ((eq fn 'if)
+	   (cons fn
+	     (cons (byte-optimize-form (nth 1 form) nil)
+	       (cons
+		(byte-optimize-form (nth 2 form) for-effect)
+		(byte-optimize-body (nthcdr 3 form) for-effect)))))
+	  
+	  ((memq fn '(and or))  ; remember, and/or are control structures.
+	   ;; take forms off the back until we can't any more.
+	   ;; In the future it could concievably be a problem that the
+	   ;; subexpressions of these forms are optimized in the reverse
+	   ;; order, but it's ok for now.
+	   (if for-effect
+	       (let ((backwards (reverse (cdr form))))
+		 (while (and backwards
+			     (null (setcar backwards
+					   (byte-optimize-form (car backwards)
+							       for-effect))))
+		   (setq backwards (cdr backwards)))
+		 (if (and (cdr form) (null backwards))
+		     (byte-compile-log
+		      "  all subforms of %s called for effect; deleted" form))
+		 (and backwards
+		      (cons fn (nreverse backwards))))
+	     (cons fn (mapcar 'byte-optimize-form (cdr form)))))
+
+	  ((eq fn 'interactive)
+	   (byte-compile-warn "misplaced interactive spec: %s"
+			      (prin1-to-string form))
+	   nil)
+	  
+	  ((memq fn '(defun defmacro function
+		      condition-case save-window-excursion))
+	   ;; These forms are compiled as constants or by breaking out
+	   ;; all the subexpressions and compiling them separately.
+	   form)
+
+	  ((eq fn 'unwind-protect)
+	   ;; the "protected" part of an unwind-protect is compiled (and thus
+	   ;; optimized) as a top-level form, so don't do it here.  But the
+	   ;; non-protected part has the same for-effect status as the
+	   ;; unwind-protect itself.  (The protected part is always for effect,
+	   ;; but that isn't handled properly yet.)
+	   (cons fn
+		 (cons (byte-optimize-form (nth 1 form) for-effect)
+		       (cdr (cdr form)))))
+	   
+	  ((eq fn 'catch)
+	   ;; the body of a catch is compiled (and thus optimized) as a
+	   ;; top-level form, so don't do it here.  The tag is never
+	   ;; for-effect.  The body should have the same for-effect status
+	   ;; as the catch form itself, but that isn't handled properly yet.
+	   (cons fn
+		 (cons (byte-optimize-form (nth 1 form) nil)
+		       (cdr (cdr form)))))
+
+	  ;; If optimization is on, this is the only place that macros are
+	  ;; expanded.  If optimization is off, then macroexpansion happens
+	  ;; in byte-compile-form.  Otherwise, the macros are already expanded
+	  ;; by the time that is reached.
+	  ((not (eq form
+		    (setq form (macroexpand form
+					    byte-compile-macro-environment))))
+	   (byte-optimize-form form for-effect))
+	  
+	  ((not (symbolp fn))
+	   (or (eq 'mocklisp (car-safe fn)) ; ha!
+	       (byte-compile-warn "%s is a malformed function"
+				  (prin1-to-string fn)))
+	   form)
+
+	  ((and for-effect (setq tmp (get fn 'side-effect-free))
+		(or byte-compile-delete-errors
+		    (eq tmp 'error-free)
+		    (progn
+		      (byte-compile-warn "%s called for effect"
+					 (prin1-to-string form))
+		      nil)))
+	   (byte-compile-log "  %s called for effect; deleted" fn)
+	   ;; appending a nil here might not be necessary, but it can't hurt.
+	   (byte-optimize-form
+	    (cons 'progn (append (cdr form) '(nil))) t))
+	  
+	  (t
+	   ;; Otherwise, no args can be considered to be for-effect,
+	   ;; even if the called function is for-effect, because we
+	   ;; don't know anything about that function.
+	   (cons fn (mapcar 'byte-optimize-form (cdr form)))))))
+
+
+(defun byte-optimize-form (form &optional for-effect)
+  "The source-level pass of the optimizer."
+  ;;
+  ;; First, optimize all sub-forms of this one.
+  (setq form (byte-optimize-form-code-walker form for-effect))
+  ;;
+  ;; after optimizing all subforms, optimize this form until it doesn't
+  ;; optimize any further.  This means that some forms will be passed through
+  ;; the optimizer many times, but that's necessary to make the for-effect
+  ;; processing do as much as possible.
+  ;;
+  (let (opt new)
+    (if (and (consp form)
+	     (symbolp (car form))
+	     (or (and for-effect
+		      ;; we don't have any of these yet, but we might.
+		      (setq opt (get (car form) 'byte-for-effect-optimizer)))
+		 (setq opt (get (car form) 'byte-optimizer)))
+	     (not (eq form (setq new (funcall opt form)))))
+	(progn
+;;	  (if (equal form new) (error "bogus optimizer -- %s" opt))
+	  (byte-compile-log "  %s\t==>\t%s" form new)
+	  (setq new (byte-optimize-form new for-effect))
+	  new)
+      form)))
+
+
+(defun byte-optimize-body (forms all-for-effect)
+  ;; optimize the cdr of a progn or implicit progn; all forms is a list of
+  ;; forms, all but the last of which are optimized with the assumption that
+  ;; they are being called for effect.  the last is for-effect as well if
+  ;; all-for-effect is true.  returns a new list of forms.
+  (let ((rest forms)
+	(result nil)
+	fe new)
+    (while rest
+      (setq fe (or all-for-effect (cdr rest)))
+      (setq new (and (car rest) (byte-optimize-form (car rest) fe)))
+      (if (or new (not fe))
+	  (setq result (cons new result)))
+      (setq rest (cdr rest)))
+    (nreverse result)))
+
+
+;;; some source-level optimizers
+;;;
+;;; when writing optimizers, be VERY careful that the optimizer returns
+;;; something not EQ to its argument if and ONLY if it has made a change.
+;;; This implies that you cannot simply destructively modify the list;
+;;; you must return something not EQ to it if you make an optimization.
+;;;
+;;; It is now safe to optimize code such that it introduces new bindings.
+
+;; I'd like this to be a defsubst, but let's not be self-referental...
+(defmacro byte-compile-trueconstp (form)
+  ;; Returns non-nil if FORM is a non-nil constant.
+  (` (cond ((consp (, form)) (eq (car (, form)) 'quote))
+	   ((not (symbolp (, form))))
+	   ((eq (, form) t)))))
+
+(defun byte-optimize-associative-math (form)
+  "If the function is being called with constant numeric args,
+evaluate as much as possible at compile-time.  This optimizer 
+assumes that the function is associative, like + or *."
+  (let ((args nil)
+	(constants nil)
+	(rest (cdr form)))
+    (while rest
+      (if (numberp (car rest))
+	  (setq constants (cons (car rest) constants))
+	  (setq args (cons (car rest) args)))
+      (setq rest (cdr rest)))
+    (if (cdr constants)
+	(if args
+	    (list (car form)
+		  (apply (car form) constants)
+		  (if (cdr args)
+		      (cons (car form) (nreverse args))
+		      (car args)))
+	    (apply (car form) constants))
+	form)))
+
+(defun byte-optimize-nonassociative-math (form)
+  "If the function is being called with constant numeric args,
+evaluate as much as possible at compile-time.  This optimizer 
+assumes that the function is nonassociative, like - or /."
+  (if (or (not (numberp (car (cdr form))))
+	  (not (numberp (car (cdr (cdr form))))))
+      form
+    (let ((constant (car (cdr form)))
+	  (rest (cdr (cdr form))))
+      (while (numberp (car rest))
+	(setq constant (funcall (car form) constant (car rest))
+	      rest (cdr rest)))
+      (if rest
+	  (cons (car form) (cons constant rest))
+	  constant))))
+
+;;(defun byte-optimize-associative-two-args-math (form)
+;;  (setq form (byte-optimize-associative-math form))
+;;  (if (consp form)
+;;      (byte-optimize-two-args-left form)
+;;      form))
+
+;;(defun byte-optimize-nonassociative-two-args-math (form)
+;;  (setq form (byte-optimize-nonassociative-math form))
+;;  (if (consp form)
+;;      (byte-optimize-two-args-right form)
+;;      form))
+
+(defun byte-optimize-delay-constants-math (form start fun)
+  ;; Merge all FORM's constants from number START, call FUN on them
+  ;; and put the result at the end.
+  (let ((rest (nthcdr (1- start) form)))
+    (while (cdr (setq rest (cdr rest)))
+      (if (numberp (car rest))
+	  (let (constants)
+	    (setq form (copy-sequence form)
+		  rest (nthcdr (1- start) form))
+	    (while (setq rest (cdr rest))
+	      (cond ((numberp (car rest))
+		     (setq constants (cons (car rest) constants))
+		     (setcar rest nil))))
+	    (setq form (nconc (delq nil form)
+			      (list (apply fun (nreverse constants))))))))
+    form))
+
+(defun byte-optimize-plus (form)
+  (setq form (byte-optimize-delay-constants-math form 1 '+))
+  (if (memq 0 form) (setq form (delq 0 (copy-sequence form))))
+  ;;(setq form (byte-optimize-associative-two-args-math form))
+  (cond ((null (cdr form))
+	 (condition-case ()
+	     (eval form)
+	   (error form)))
+	((null (cdr (cdr form))) (nth 1 form))
+	(t form)))
+
+(defun byte-optimize-minus (form)
+  ;; Put constants at the end, except the last constant.
+  (setq form (byte-optimize-delay-constants-math form 2 '+))
+  ;; Now only first and last element can be a number.
+  (let ((last (car (reverse (nthcdr 3 form)))))
+    (cond ((eq 0 last)
+	   ;; (- x y ... 0)  --> (- x y ...)
+	   (setq form (copy-sequence form))
+	   (setcdr (cdr (cdr form)) (delq 0 (nthcdr 3 form))))
+	  ;; If form is (- CONST foo... CONST), merge first and last.
+	  ((and (numberp (nth 1 form))
+		(numberp last))
+	   (setq form (nconc (list '- (- (nth 1 form) last) (nth 2 form))
+			     (delq last (copy-sequence (nthcdr 3 form))))))))
+  (if (eq (nth 2 form) 0)
+      (nth 1 form)			; (- x 0)  -->  x
+    (byte-optimize-predicate
+     (if (and (null (cdr (cdr (cdr form))))
+	      (eq (nth 1 form) 0))	; (- 0 x)  -->  (- x)
+	 (cons (car form) (cdr (cdr form)))
+       form))))
+
+(defun byte-optimize-multiply (form)
+  (setq form (byte-optimize-delay-constants-math form 1 '*))
+  ;; If there is a constant in FORM, it is now the last element.
+  (cond ((null (cdr form)) 1)
+	((null (cdr (cdr form))) (nth 1 form))
+	((let ((last (car (reverse form))))
+	   (cond ((eq 0 last)  (list 'progn (cdr form)))
+		 ((eq 1 last)  (delq 1 (copy-sequence form)))
+		 ((eq -1 last) (list '- (delq -1 (copy-sequence form))))
+		 ((and (eq 2 last)
+		       (memq t (mapcar 'symbolp (cdr form))))
+		  (prog1 (setq form (delq 2 (copy-sequence form)))
+		    (while (not (symbolp (car (setq form (cdr form))))))
+		    (setcar form (list '+ (car form) (car form)))))
+		 (form))))))
+
+(defsubst byte-compile-butlast (form)
+  (nreverse (cdr (reverse form))))
+
+(defun byte-optimize-divide (form)
+  (setq form (byte-optimize-delay-constants-math form 2 '*))
+  (let ((last (car (reverse (cdr (cdr form))))))
+    (if (numberp last)
+	(cond ((= last 1)
+	       (setq form (byte-compile-butlast form)))
+	      ((numberp (nth 1 form))
+	       (setq form (cons (car form)
+				(cons (/ (nth 1 form) last)
+				      (byte-compile-butlast (cdr (cdr form)))))
+		     last nil))))
+    (cond ((null (cdr (cdr form)))
+	   (nth 1 form))
+	  ((eq (nth 1 form) 0)
+	   (append '(progn) (cdr (cdr form)) '(0)))
+	  ((eq last -1)
+	   (list '- (if (nthcdr 3 form)
+			(byte-compile-butlast form)
+		      (nth 1 form))))
+	  (form))))
+
+(defun byte-optimize-logmumble (form)
+  (setq form (byte-optimize-delay-constants-math form 1 (car form)))
+  (byte-optimize-predicate
+   (cond ((memq 0 form)
+	  (setq form (if (eq (car form) 'logand)
+			 (cons 'progn (cdr form))
+		       (delq 0 (copy-sequence form)))))
+	 ((and (eq (car-safe form) 'logior)
+	       (memq -1 form))
+	  (delq -1 (copy-sequence form)))
+	 (form))))
+
+
+(defun byte-optimize-binary-predicate (form)
+  (if (byte-compile-constp (nth 1 form))
+      (if (byte-compile-constp (nth 2 form))
+	  (condition-case ()
+	      (list 'quote (eval form))
+	    (error form))
+	;; This can enable some lapcode optimizations.
+	(list (car form) (nth 2 form) (nth 1 form)))
+    form))
+
+(defun byte-optimize-predicate (form)
+  (let ((ok t)
+	(rest (cdr form)))
+    (while (and rest ok)
+      (setq ok (byte-compile-constp (car rest))
+	    rest (cdr rest)))
+    (if ok
+	(condition-case ()
+	    (list 'quote (eval form))
+	  (error form))
+	form)))
+
+(defun byte-optimize-identity (form)
+  (if (and (cdr form) (null (cdr (cdr form))))
+      (nth 1 form)
+    (byte-compile-warn "identity called with %d arg%s, but requires 1"
+		       (length (cdr form))
+		       (if (= 1 (length (cdr form))) "" "s"))
+    form))
+
+(put 'identity 'byte-optimizer 'byte-optimize-identity)
+
+(put '+   'byte-optimizer 'byte-optimize-plus)
+(put '*   'byte-optimizer 'byte-optimize-multiply)
+(put '-   'byte-optimizer 'byte-optimize-minus)
+(put '/   'byte-optimizer 'byte-optimize-divide)
+(put 'max 'byte-optimizer 'byte-optimize-associative-math)
+(put 'min 'byte-optimizer 'byte-optimize-associative-math)
+
+(put '=   'byte-optimizer 'byte-optimize-binary-predicate)
+(put 'eq  'byte-optimizer 'byte-optimize-binary-predicate)
+(put 'eql 'byte-optimizer 'byte-optimize-binary-predicate)
+(put 'equal   'byte-optimizer 'byte-optimize-binary-predicate)
+(put 'string= 'byte-optimizer 'byte-optimize-binary-predicate)
+(put 'string-equal 'byte-optimizer 'byte-optimize-binary-predicate)
+
+(put '<   'byte-optimizer 'byte-optimize-predicate)
+(put '>   'byte-optimizer 'byte-optimize-predicate)
+(put '<=  'byte-optimizer 'byte-optimize-predicate)
+(put '>=  'byte-optimizer 'byte-optimize-predicate)
+(put '1+  'byte-optimizer 'byte-optimize-predicate)
+(put '1-  'byte-optimizer 'byte-optimize-predicate)
+(put 'not 'byte-optimizer 'byte-optimize-predicate)
+(put 'null  'byte-optimizer 'byte-optimize-predicate)
+(put 'memq  'byte-optimizer 'byte-optimize-predicate)
+(put 'consp 'byte-optimizer 'byte-optimize-predicate)
+(put 'listp 'byte-optimizer 'byte-optimize-predicate)
+(put 'symbolp 'byte-optimizer 'byte-optimize-predicate)
+(put 'stringp 'byte-optimizer 'byte-optimize-predicate)
+(put 'string< 'byte-optimizer 'byte-optimize-predicate)
+(put 'string-lessp 'byte-optimizer 'byte-optimize-predicate)
+
+(put 'logand 'byte-optimizer 'byte-optimize-logmumble)
+(put 'logior 'byte-optimizer 'byte-optimize-logmumble)
+(put 'logxor 'byte-optimizer 'byte-optimize-logmumble)
+(put 'lognot 'byte-optimizer 'byte-optimize-predicate)
+
+(put 'car 'byte-optimizer 'byte-optimize-predicate)
+(put 'cdr 'byte-optimizer 'byte-optimize-predicate)
+(put 'car-safe 'byte-optimizer 'byte-optimize-predicate)
+(put 'cdr-safe 'byte-optimizer 'byte-optimize-predicate)
+
+
+;; I'm not convinced that this is necessary.  Doesn't the optimizer loop 
+;; take care of this? - Jamie
+;; I think this may some times be necessary to reduce ie (quote 5) to 5,
+;; so arithmetic optimizers recognize the numerinc constant.  - Hallvard
+(put 'quote 'byte-optimizer 'byte-optimize-quote)
+(defun byte-optimize-quote (form)
+  (if (or (consp (nth 1 form))
+	  (and (symbolp (nth 1 form))
+	       (not (memq (nth 1 form) '(nil t)))))
+      form
+    (nth 1 form)))
+
+(defun byte-optimize-zerop (form)
+  (cond ((numberp (nth 1 form))
+	 (eval form))
+	(byte-compile-delete-errors
+	 (list '= (nth 1 form) 0))
+	(form)))
+
+(put 'zerop 'byte-optimizer 'byte-optimize-zerop)
+
+(defun byte-optimize-and (form)
+  ;; Simplify if less than 2 args.
+  ;; if there is a literal nil in the args to `and', throw it and following
+  ;; forms away, and surround the `and' with (progn ... nil).
+  (cond ((null (cdr form)))
+	((memq nil form)
+	 (list 'progn
+	       (byte-optimize-and
+		(prog1 (setq form (copy-sequence form))
+		  (while (nth 1 form)
+		    (setq form (cdr form)))
+		  (setcdr form nil)))
+	       nil))
+	((null (cdr (cdr form)))
+	 (nth 1 form))
+	((byte-optimize-predicate form))))
+
+(defun byte-optimize-or (form)
+  ;; Throw away nil's, and simplify if less than 2 args.
+  ;; If there is a literal non-nil constant in the args to `or', throw away all
+  ;; following forms.
+  (if (memq nil form)
+      (setq form (delq nil (copy-sequence form))))
+  (let ((rest form))
+    (while (cdr (setq rest (cdr rest)))
+      (if (byte-compile-trueconstp (car rest))
+	  (setq form (copy-sequence form)
+		rest (setcdr (memq (car rest) form) nil))))
+    (if (cdr (cdr form))
+	(byte-optimize-predicate form)
+      (nth 1 form))))
+
+(defun byte-optimize-cond (form)
+  ;; if any clauses have a literal nil as their test, throw them away.
+  ;; if any clause has a literal non-nil constant as its test, throw
+  ;; away all following clauses.
+  (let (rest)
+    ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
+    (while (setq rest (assq nil (cdr form)))
+      (setq form (delq rest (copy-sequence form))))
+    (if (memq nil (cdr form))
+	(setq form (delq nil (copy-sequence form))))
+    (setq rest form)
+    (while (setq rest (cdr rest))
+      (cond ((byte-compile-trueconstp (car-safe (car rest)))
+	     (cond ((eq rest (cdr form))
+		    (setq form
+			  (if (cdr (car rest))
+			      (if (cdr (cdr (car rest)))
+				  (cons 'progn (cdr (car rest)))
+				(nth 1 (car rest)))
+			    (car (car rest)))))
+		   ((cdr rest)
+		    (setq form (copy-sequence form))
+		    (setcdr (memq (car rest) form) nil)))
+	     (setq rest nil)))))
+  ;;
+  ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
+  (if (eq 'cond (car-safe form))
+      (let ((clauses (cdr form)))
+	(if (and (consp (car clauses))
+		 (null (cdr (car clauses))))
+	    (list 'or (car (car clauses))
+		  (byte-optimize-cond
+		   (cons (car form) (cdr (cdr form)))))
+	  form))
+    form))
+
+(defun byte-optimize-if (form)
+  ;; (if <true-constant> <then> <else...>) ==> <then>
+  ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
+  ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
+  ;; (if <test> <then> nil) ==> (if <test> <then>)
+  (let ((clause (nth 1 form)))
+    (cond ((byte-compile-trueconstp clause)
+	   (nth 2 form))
+	  ((null clause)
+	   (if (nthcdr 4 form)
+	       (cons 'progn (nthcdr 3 form))
+	     (nth 3 form)))
+	  ((nth 2 form)
+	   (if (equal '(nil) (nthcdr 3 form))
+	       (list 'if clause (nth 2 form))
+	     form))
+	  ((or (nth 3 form) (nthcdr 4 form))
+	   (list 'if (list 'not clause)
+		 (if (nthcdr 4 form)
+		     (cons 'progn (nthcdr 3 form))
+		   (nth 3 form))))
+	  (t
+	   (list 'progn clause nil)))))
+
+(defun byte-optimize-while (form)
+  (if (nth 1 form)
+      form))
+
+(put 'and   'byte-optimizer 'byte-optimize-and)
+(put 'or    'byte-optimizer 'byte-optimize-or)
+(put 'cond  'byte-optimizer 'byte-optimize-cond)
+(put 'if    'byte-optimizer 'byte-optimize-if)
+(put 'while 'byte-optimizer 'byte-optimize-while)
+
+;; byte-compile-negation-optimizer lives in bytecomp.el
+(put '/= 'byte-optimizer 'byte-compile-negation-optimizer)
+(put 'atom 'byte-optimizer 'byte-compile-negation-optimizer)
+(put 'nlistp 'byte-optimizer 'byte-compile-negation-optimizer)
+
+
+(defun byte-optimize-funcall (form)
+  ;; (funcall '(lambda ...) ...) ==> ((lambda ...) ...)
+  ;; (funcall 'foo ...) ==> (foo ...)
+  (let ((fn (nth 1 form)))
+    (if (memq (car-safe fn) '(quote function))
+	(cons (nth 1 fn) (cdr (cdr form)))
+	form)))
+
+(defun byte-optimize-apply (form)
+  ;; If the last arg is a literal constant, turn this into a funcall.
+  ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
+  (let ((fn (nth 1 form))
+	(last (nth (1- (length form)) form))) ; I think this really is fastest
+    (or (if (or (null last)
+		(eq (car-safe last) 'quote))
+	    (if (listp (nth 1 last))
+		(let ((butlast (nreverse (cdr (reverse (cdr (cdr form)))))))
+		  (nconc (list 'funcall fn) butlast (nth 1 last)))
+	      (byte-compile-warn
+	       "last arg to apply can't be a literal atom: %s"
+	       (prin1-to-string last))
+	      nil))
+	form)))
+
+(put 'funcall 'byte-optimizer 'byte-optimize-funcall)
+(put 'apply   'byte-optimizer 'byte-optimize-apply)
+
+
+(put 'let 'byte-optimizer 'byte-optimize-letX)
+(put 'let* 'byte-optimizer 'byte-optimize-letX)
+(defun byte-optimize-letX (form)
+  (cond ((null (nth 1 form))
+	 ;; No bindings
+	 (cons 'progn (cdr (cdr form))))
+	((or (nth 2 form) (nthcdr 3 form))
+	 form)
+	 ;; The body is nil
+	((eq (car form) 'let)
+	 (append '(progn) (mapcar 'car (mapcar 'cdr (nth 1 form))) '(nil)))
+	(t
+	 (let ((binds (reverse (nth 1 form))))
+	   (list 'let* (reverse (cdr binds)) (nth 1 (car binds)) nil)))))
+
+
+(put 'nth 'byte-optimizer 'byte-optimize-nth)
+(defun byte-optimize-nth (form)
+  (if (memq (nth 1 form) '(0 1))
+      (list 'car (if (zerop (nth 1 form))
+		     (nth 2 form)
+		   (list 'cdr (nth 2 form))))
+    (byte-optimize-predicate form)))
+
+(put 'nthcdr 'byte-optimizer 'byte-optimize-nthcdr)
+(defun byte-optimize-nthcdr (form)
+  (let ((count (nth 1 form)))
+    (if (not (memq count '(0 1 2)))
+	(byte-optimize-predicate form)
+      (setq form (nth 2 form))
+      (while (natnump (setq count (1- count)))
+	(setq form (list 'cdr form)))
+      form)))
+
+;;; enumerating those functions which need not be called if the returned 
+;;; value is not used.  That is, something like
+;;;    (progn (list (something-with-side-effects) (yow))
+;;;           (foo))
+;;; may safely be turned into
+;;;    (progn (progn (something-with-side-effects) (yow))
+;;;           (foo))
+;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
+
+;;; I wonder if I missed any :-\)
+(let ((side-effect-free-fns
+       '(% * + / /= 1+ < <= = > >= append aref ash assoc assq boundp
+	 buffer-file-name buffer-local-variables buffer-modified-p
+	 buffer-substring capitalize car cdr concat coordinates-in-window-p
+	 copy-marker count-lines documentation downcase elt fboundp featurep
+	 file-directory-p file-exists-p file-locked-p file-name-absolute-p
+	 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
+	 format get get-buffer get-buffer-window getenv get-file-buffer length
+	 logand logior lognot logxor lsh marker-buffer max member memq min mod
+	 next-window nth nthcdr previous-window rassq regexp-quote reverse
+	 string< string= string-lessp string-equal substring user-variable-p
+	 window-buffer window-edges window-height window-hscroll window-width
+	 zerop))
+      ;; could also add plusp, minusp, signum.  If anyone ever defines
+      ;; these, they will certainly be side-effect free.
+      (side-effect-and-error-free-fns
+       '(arrayp atom bobp bolp buffer-end buffer-list buffer-size
+	 buffer-string bufferp char-or-string-p commandp cons consp
+	 current-buffer dot dot-marker eobp eolp eq eql equal
+	 get-largest-window identity integerp integer-or-marker-p
+	 interactive-p keymapp list listp make-marker mark mark-marker
+	 markerp minibuffer-window natnump nlistp not null numberp
+	 one-window-p point point-marker processp selected-window sequencep
+	 stringp subrp symbolp syntax-table-p vector vectorp windowp)))
+  (while side-effect-free-fns
+    (put (car side-effect-free-fns) 'side-effect-free t)
+    (setq side-effect-free-fns (cdr side-effect-free-fns)))
+  (while side-effect-and-error-free-fns
+    (put (car side-effect-and-error-free-fns) 'side-effect-free 'error-free)
+    (setq side-effect-and-error-free-fns (cdr side-effect-and-error-free-fns)))
+  nil)
+
+
+(defun byte-compile-splice-in-already-compiled-code (form)
+  ;; form is (byte-code "..." [...] n)
+  (if (not (memq byte-optimize '(t lap)))
+      (byte-compile-normal-call form)
+    (byte-inline-lapcode
+     (byte-decompile-bytecode-1 (nth 1 form) (nth 2 form) t))
+    (setq byte-compile-maxdepth (max (+ byte-compile-depth (nth 3 form))
+				     byte-compile-maxdepth))
+    (setq byte-compile-depth (1+ byte-compile-depth))))
+
+(put 'byte-code 'byte-compile 'byte-compile-splice-in-already-compiled-code)
+
+
+(defconst byte-constref-ops
+  '(byte-constant byte-constant2 byte-varref byte-varset byte-varbind))
+
+;;; This function extracts the bitfields from variable-length opcodes.
+;;; Originally defined in disass.el (which no longer uses it.)
+
+(defun disassemble-offset ()
+  "Don't call this!"
+  ;; fetch and return the offset for the current opcode.
+  ;; return NIL if this opcode has no offset
+  ;; OP, PTR and BYTES are used and set dynamically
+  (defvar op)
+  (defvar ptr)
+  (defvar bytes)
+  (cond ((< op byte-nth)
+	 (let ((tem (logand op 7)))
+	   (setq op (logand op 248))
+	   (cond ((eq tem 6)
+		  (setq ptr (1+ ptr))	;offset in next byte
+		  (aref bytes ptr))
+		 ((eq tem 7)
+		  (setq ptr (1+ ptr))	;offset in next 2 bytes
+		  (+ (aref bytes ptr)
+		     (progn (setq ptr (1+ ptr))
+			    (lsh (aref bytes ptr) 8))))
+		 (t tem))))		;offset was in opcode
+	((>= op byte-constant)
+	 (prog1 (- op byte-constant)	;offset in opcode
+	   (setq op byte-constant)))
+	((and (>= op byte-constant2)
+	      (<= op byte-goto-if-not-nil-else-pop))
+	 (setq ptr (1+ ptr))		;offset in next 2 bytes
+	 (+ (aref bytes ptr)
+	    (progn (setq ptr (1+ ptr))
+		   (lsh (aref bytes ptr) 8))))
+	((and (>= op byte-rel-goto)
+	      (<= op byte-insertN))
+	 (setq ptr (1+ ptr))		;offset in next byte
+	 (aref bytes ptr))))
+
+
+;;; This de-compiler is used for inline expansion of compiled functions,
+;;; and by the disassembler.
+;;;
+(defun byte-decompile-bytecode (bytes constvec)
+  "Turns BYTECODE into lapcode, refering to CONSTVEC."
+  (let ((byte-compile-constants nil)
+	(byte-compile-variables nil)
+	(byte-compile-tag-number 0))
+    (byte-decompile-bytecode-1 bytes constvec)))
+
+(defun byte-decompile-bytecode-1 (bytes constvec &optional make-splicable)
+  "As byte-decompile-bytecode, but updates
+byte-compile-{constants, variables, tag-number}.
+If the optional 3rd arg is true, then `return' opcodes are replaced
+with `goto's destined for the end of the code."
+  (let ((length (length bytes))
+	(ptr 0) optr tag tags op offset
+	lap tmp
+	endtag
+	(retcount 0))
+    (while (not (= ptr length))
+      (setq op (aref bytes ptr)
+	    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)))
+	     ;; it's a pc
+	     (setq offset
+		   (cdr (or (assq offset tags)
+			    (car (setq tags
+				       (cons (cons offset
+						   (byte-compile-make-tag))
+					     tags)))))))
+	    ((cond ((eq op 'byte-constant2) (setq op 'byte-constant) t)
+		   ((memq op byte-constref-ops)))
+	     (setq tmp (aref constvec offset)
+		   offset (if (eq op 'byte-constant)
+			      (byte-compile-get-constant tmp)
+			    (or (assq tmp byte-compile-variables)
+				(car (setq byte-compile-variables
+					   (cons (list tmp)
+						 byte-compile-variables)))))))
+	    ((and make-splicable
+		  (eq op 'byte-return))
+	     (if (= ptr (1- length))
+		 (setq op nil)
+	       (setq offset (or endtag (setq endtag (byte-compile-make-tag)))
+		     op 'byte-goto))))
+      ;; lap = ( [ (pc . (op . arg)) ]* )
+      (setq lap (cons (cons optr (cons op (or offset 0)))
+		      lap))
+      (setq ptr (1+ ptr)))
+    ;; take off the dummy nil op that we replaced a trailing "return" with.
+    (let ((rest lap))
+      (while rest
+	(cond ((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))
+    (if (null (car (cdr (car lap))))
+	(setq lap (cdr lap)))
+    (if endtag
+	(setq lap (cons (cons nil endtag) lap)))
+    ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
+    (mapcar 'cdr (nreverse lap))))
+
+
+;;; peephole optimizer
+
+(defconst byte-tagref-ops (cons 'TAG byte-goto-ops))
+
+(defconst byte-conditional-ops
+  '(byte-goto-if-nil byte-goto-if-not-nil byte-goto-if-nil-else-pop
+    byte-goto-if-not-nil-else-pop))
+
+(defconst byte-after-unbind-ops
+   '(byte-constant byte-dup
+     byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
+     byte-eq byte-equal byte-not
+     byte-cons byte-list1 byte-list2	; byte-list3 byte-list4
+     byte-interactive-p
+     ;; How about other side-effect-free-ops?  Is it safe to move an
+     ;; error invocation (such as from nth) out of an unwind-protect?
+     "Byte-codes that can be moved past an unbind."))
+
+(defconst byte-compile-side-effect-and-error-free-ops
+  '(byte-constant byte-dup byte-symbolp byte-consp byte-stringp byte-listp
+    byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
+    byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
+    byte-point-min byte-following-char byte-preceding-char
+    byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
+    byte-current-buffer byte-interactive-p))
+
+(defconst byte-compile-side-effect-free-ops
+  (nconc 
+   '(byte-varref byte-nth byte-memq byte-car byte-cdr byte-length byte-aref
+     byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
+     byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
+     byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
+     byte-buffer-substring byte-string= byte-string< byte-nthcdr byte-elt
+     byte-member byte-assq byte-quo byte-rem)
+   byte-compile-side-effect-and-error-free-ops))
+
+;;; This piece of shit is because of the way DEFVAR_BOOL() variables work.
+;;; Consider the code
+;;;
+;;;	(defun foo (flag)
+;;;	  (let ((old-pop-ups pop-up-windows)
+;;;		(pop-up-windows flag))
+;;;	    (cond ((not (eq pop-up-windows old-pop-ups))
+;;;		   (setq old-pop-ups pop-up-windows)
+;;;		   ...))))
+;;;
+;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
+;;; something else.  But if we optimize
+;;;
+;;;	varref flag
+;;;	varbind pop-up-windows
+;;;	varref pop-up-windows
+;;;	not
+;;; to
+;;;	varref flag
+;;;	dup
+;;;	varbind pop-up-windows
+;;;	not
+;;;
+;;; we break the program, because it will appear that pop-up-windows and 
+;;; old-pop-ups are not EQ when really they are.  So we have to know what
+;;; 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)
+  "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.")
+
+(defun byte-optimize-lapcode (lap &optional for-effect)
+  "Simple peephole optimizer.  LAP is both modified and returned."
+  (let (lap0 off0
+	lap1 off1
+	lap2 off2
+	(keep-going 'first-time)
+	(add-depth 0)
+	rest tmp tmp2 tmp3
+	(side-effect-free (if byte-compile-delete-errors
+			      byte-compile-side-effect-free-ops
+			    byte-compile-side-effect-and-error-free-ops)))
+    (while keep-going
+      (or (eq keep-going 'first-time)
+	  (byte-compile-log-lap "  ---- next pass"))
+      (setq rest lap
+	    keep-going nil)
+      (while rest
+	(setq lap0 (car rest)
+	      lap1 (nth 1 rest)
+	      lap2 (nth 2 rest))
+
+	;; You may notice that sequences like "dup varset discard" are
+	;; optimized but sequences like "dup varset TAG1: discard" are not.
+	;; You may be tempted to change this; resist that temptation.
+	(cond ;;
+	      ;; <side-effect-free> pop -->  <deleted>
+	      ;;  ...including:
+	      ;; const-X pop   -->  <deleted>
+	      ;; varref-X pop  -->  <deleted>
+	      ;; dup pop       -->  <deleted>
+	      ;;
+	      ((and (eq 'byte-discard (car lap1))
+		    (memq (car lap0) side-effect-free))
+	       (setq keep-going t)
+	       (setq tmp (aref byte-stack+-info (symbol-value (car lap0))))
+	       (setq rest (cdr rest))
+	       (cond ((= tmp 1)
+		      (byte-compile-log-lap
+ 		       "  %s discard\t-->\t<deleted>" lap0)
+		      (setq lap (delq lap0 (delq lap1 lap))))
+		     ((= tmp 0)
+		      (byte-compile-log-lap
+		       "  %s discard\t-->\t<deleted> discard" lap0)
+		      (setq lap (delq lap0 lap)))
+		     ((= tmp -1)
+		      (byte-compile-log-lap
+		       "  %s discard\t-->\tdiscard discard" lap0)
+		      (setcar lap0 'byte-discard)
+		      (setcdr lap0 0))
+		     ((error "Optimizer error: too much on the stack"))))
+	      ;;
+	      ;; goto*-X X:  -->  X:
+	      ;;
+	      ((and (memq (car lap0) byte-goto-ops)
+		    (eq (cdr lap0) lap1))
+	       (cond ((eq (car lap0) 'byte-goto)
+		      (setq lap (delq lap0 lap))
+		      (setq tmp "<deleted>"))
+		     ((memq (car lap0) byte-goto-always-pop-ops)
+		      (setcar lap0 (setq tmp 'byte-discard))
+		      (setcdr lap0 0))
+		     ((error "Depth conflict at tag %d" (nth 2 lap0))))
+	       (and (memq byte-optimize-log '(t byte))
+		    (byte-compile-log "  (goto %s) %s:\t-->\t%s %s:"
+				      (nth 1 lap1) (nth 1 lap1)
+				      tmp (nth 1 lap1)))
+	       (setq keep-going t))
+	      ;;
+	      ;; varset-X varref-X  -->  dup varset-X
+	      ;; varbind-X varref-X  -->  dup varbind-X
+	      ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
+	      ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
+	      ;; The latter two can enable other optimizations.
+	      ;;
+	      ((and (eq 'byte-varref (car lap2))
+		    (eq (cdr lap1) (cdr lap2))
+		    (memq (car lap1) '(byte-varset byte-varbind)))
+	       (if (and (setq tmp (memq (car (cdr lap2)) byte-boolean-vars))
+			(not (eq (car lap0) 'byte-constant)))
+		   nil
+		 (setq keep-going t)
+		 (if (memq (car lap0) '(byte-constant byte-dup))
+		     (progn
+		       (setq tmp (if (or (not tmp)
+					 (memq (car (cdr lap0)) '(nil t)))
+				     (cdr lap0)
+				   (byte-compile-get-constant t)))
+		       (byte-compile-log-lap "  %s %s %s\t-->\t%s %s %s"
+					     lap0 lap1 lap2 lap0 lap1
+					     (cons (car lap0) tmp))
+		       (setcar lap2 (car lap0))
+		       (setcdr lap2 tmp))
+		   (byte-compile-log-lap "  %s %s\t-->\tdup %s" lap1 lap2 lap1)
+		   (setcar lap2 (car lap1))
+		   (setcar lap1 'byte-dup)
+		   (setcdr lap1 0)
+		   ;; The stack depth gets locally increased, so we will
+		   ;; increase maxdepth in case depth = maxdepth here.
+		   ;; This can cause the third argument to byte-code to
+		   ;; be larger than necessary.
+		   (setq add-depth 1))))
+	      ;;
+	      ;; dup varset-X discard  -->  varset-X
+	      ;; dup varbind-X discard  -->  varbind-X
+	      ;; (the varbind variant can emerge from other optimizations)
+	      ;;
+	      ((and (eq 'byte-dup (car lap0))
+		    (eq 'byte-discard (car lap2))
+		    (memq (car lap1) '(byte-varset byte-varbind)))
+	       (byte-compile-log-lap "  dup %s discard\t-->\t%s" lap1 lap1)
+	       (setq keep-going t
+		     rest (cdr rest))
+	       (setq lap (delq lap0 (delq lap2 lap))))
+	      ;;
+	      ;; not goto-X-if-nil              -->  goto-X-if-non-nil
+	      ;; not goto-X-if-non-nil          -->  goto-X-if-nil
+	      ;;
+	      ;; it is wrong to do the same thing for the -else-pop variants.
+	      ;;
+	      ((and (eq 'byte-not (car lap0))
+		    (or (eq 'byte-goto-if-nil (car lap1))
+			(eq 'byte-goto-if-not-nil (car lap1))))
+	       (byte-compile-log-lap "  not %s\t-->\t%s"
+				     lap1
+				     (cons
+				      (if (eq (car lap1) 'byte-goto-if-nil)
+					  'byte-goto-if-not-nil
+					'byte-goto-if-nil)
+				      (cdr lap1)))
+	       (setcar lap1 (if (eq (car lap1) 'byte-goto-if-nil)
+				'byte-goto-if-not-nil
+				'byte-goto-if-nil))
+	       (setq lap (delq lap0 lap))
+	       (setq keep-going t))
+	      ;;
+	      ;; goto-X-if-nil     goto-Y X:  -->  goto-Y-if-non-nil X:
+	      ;; goto-X-if-non-nil goto-Y X:  -->  goto-Y-if-nil     X:
+	      ;;
+	      ;; it is wrong to do the same thing for the -else-pop variants.
+	      ;; 
+	      ((and (or (eq 'byte-goto-if-nil (car lap0))
+			(eq 'byte-goto-if-not-nil (car lap0)))	; gotoX
+		    (eq 'byte-goto (car lap1))			; gotoY
+		    (eq (cdr lap0) lap2))			; TAG X
+	       (let ((inverse (if (eq 'byte-goto-if-nil (car lap0))
+				  'byte-goto-if-not-nil 'byte-goto-if-nil)))
+		 (byte-compile-log-lap "  %s %s %s:\t-->\t%s %s:"
+				       lap0 lap1 lap2
+				       (cons inverse (cdr lap1)) lap2)
+		 (setq lap (delq lap0 lap))
+		 (setcar lap1 inverse)
+		 (setq keep-going t)))
+	      ;;
+	      ;; const goto-if-* --> whatever
+	      ;;
+	      ((and (eq 'byte-constant (car lap0))
+		    (memq (car lap1) byte-conditional-ops))
+	       (cond ((if (or (eq (car lap1) 'byte-goto-if-nil)
+			      (eq (car lap1) 'byte-goto-if-nil-else-pop))
+			  (car (cdr lap0))
+			(not (car (cdr lap0))))
+		      (byte-compile-log-lap "  %s %s\t-->\t<deleted>"
+					    lap0 lap1)
+		      (setq rest (cdr rest)
+			    lap (delq lap0 (delq lap1 lap))))
+		     (t
+		      (if (memq (car lap1) byte-goto-always-pop-ops)
+			  (progn
+			    (byte-compile-log-lap "  %s %s\t-->\t%s"
+			     lap0 lap1 (cons 'byte-goto (cdr lap1)))
+			    (setq lap (delq lap0 lap)))
+			(byte-compile-log-lap "  %s %s\t-->\t%s" lap0 lap1
+			 (cons 'byte-goto (cdr lap1))))
+		      (setcar lap1 'byte-goto)))
+	       (setq keep-going t))
+	      ;;
+	      ;; varref-X varref-X  -->  varref-X dup
+	      ;; varref-X [dup ...] varref-X  -->  varref-X [dup ...] dup
+	      ;; We don't optimize the const-X variations on this here,
+	      ;; because that would inhibit some goto optimizations; we
+	      ;; optimize the const-X case after all other optimizations.
+	      ;;
+	      ((and (eq 'byte-varref (car lap0))
+		    (progn
+		      (setq tmp (cdr rest))
+		      (while (eq (car (car tmp)) 'byte-dup)
+			(setq tmp (cdr tmp)))
+		      t)
+		    (eq (cdr lap0) (cdr (car tmp)))
+		    (eq 'byte-varref (car (car tmp))))
+	       (if (memq byte-optimize-log '(t byte))
+		   (let ((str ""))
+		     (setq tmp2 (cdr rest))
+		     (while (not (eq tmp tmp2))
+		       (setq tmp2 (cdr tmp2)
+			     str (concat str " dup")))
+		     (byte-compile-log-lap "  %s%s %s\t-->\t%s%s dup"
+					   lap0 str lap0 lap0 str)))
+	       (setq keep-going t)
+	       (setcar (car tmp) 'byte-dup)
+	       (setcdr (car tmp) 0)
+	       (setq rest tmp))
+	      ;;
+	      ;; TAG1: TAG2: --> TAG1: <deleted>
+	      ;; (and other references to TAG2 are replaced with TAG1)
+	      ;;
+	      ((and (eq (car lap0) 'TAG)
+		    (eq (car lap1) 'TAG))
+	       (and (memq byte-optimize-log '(t byte))
+		    (byte-compile-log "  adjascent tags %d and %d merged"
+				      (nth 1 lap1) (nth 1 lap0)))
+	       (setq tmp3 lap)
+	       (while (setq tmp2 (rassq lap0 tmp3))
+		 (setcdr tmp2 lap1)
+		 (setq tmp3 (cdr (memq tmp2 tmp3))))
+	       (setq lap (delq lap0 lap)
+		     keep-going t))
+	      ;;
+	      ;; unused-TAG: --> <deleted>
+	      ;;
+	      ((and (eq 'TAG (car lap0))
+		    (not (rassq lap0 lap)))
+	       (and (memq byte-optimize-log '(t byte))
+		    (byte-compile-log "  unused tag %d removed" (nth 1 lap0)))
+	       (setq lap (delq lap0 lap)
+		     keep-going t))
+	      ;;
+	      ;; goto   ... --> goto   <delete until TAG or end>
+	      ;; return ... --> return <delete until TAG or end>
+	      ;;
+	      ((and (memq (car lap0) '(byte-goto byte-return))
+		    (not (memq (car lap1) '(TAG nil))))
+	       (setq tmp rest)
+	       (let ((i 0)
+		     (opt-p (memq byte-optimize-log '(t lap)))
+		     str deleted)
+		 (while (and (setq tmp (cdr tmp))
+			     (not (eq 'TAG (car (car tmp)))))
+		   (if opt-p (setq deleted (cons (car tmp) deleted)
+				   str (concat str " %s")
+				   i (1+ i))))
+		 (if opt-p
+		     (let ((tagstr 
+			    (if (eq 'TAG (car (car tmp)))
+				(format "%d:" (cdr (car tmp)))
+			      (or (car tmp) ""))))
+		       (if (< i 6)
+			   (apply 'byte-compile-log-lap-1
+				  (concat "  %s" str
+					  " %s\t-->\t%s <deleted> %s")
+				  lap0
+				  (nconc (nreverse deleted)
+					 (list tagstr lap0 tagstr)))
+			 (byte-compile-log-lap
+			  "  %s <%d unreachable op%s> %s\t-->\t%s <deleted> %s"
+			  lap0 i (if (= i 1) "" "s")
+			  tagstr lap0 tagstr))))
+		 (rplacd rest tmp))
+	       (setq keep-going t))
+	      ;;
+	      ;; <safe-op> unbind --> unbind <safe-op>
+	      ;; (this may enable other optimizations.)
+	      ;;
+	      ((and (eq 'byte-unbind (car lap1))
+		    (memq (car lap0) byte-after-unbind-ops))
+	       (byte-compile-log-lap "  %s %s\t-->\t%s %s" lap0 lap1 lap1 lap0)
+	       (setcar rest lap1)
+	       (setcar (cdr rest) lap0)
+	       (setq keep-going t))
+	      ;;
+	      ;; varbind-X unbind-N         -->  discard unbind-(N-1)
+	      ;; save-excursion unbind-N    -->  unbind-(N-1)
+	      ;; save-restriction unbind-N  -->  unbind-(N-1)
+	      ;;
+	      ((and (eq 'byte-unbind (car lap1))
+		    (memq (car lap0) '(byte-varbind byte-save-excursion
+				       byte-save-restriction))
+		    (< 0 (cdr lap1)))
+	       (if (zerop (setcdr lap1 (1- (cdr lap1))))
+		   (delq lap1 rest))
+	       (if (eq (car lap0) 'byte-varbind)
+		   (setcar rest (cons 'byte-discard 0))
+		 (setq lap (delq lap0 lap)))
+	       (byte-compile-log-lap "  %s %s\t-->\t%s %s"
+		 lap0 (cons (car lap1) (1+ (cdr lap1)))
+		 (if (eq (car lap0) 'byte-varbind)
+		     (car rest)
+		   (car (cdr rest)))
+		 (if (and (/= 0 (cdr lap1))
+			  (eq (car lap0) 'byte-varbind))
+		     (car (cdr rest))
+		   ""))
+	       (setq keep-going t))
+	      ;;
+	      ;; goto*-X ... X: goto-Y  --> goto*-Y
+	      ;; goto-X ...  X: return  --> return
+	      ;;
+	      ((and (memq (car lap0) byte-goto-ops)
+		    (memq (car (setq tmp (nth 1 (memq (cdr lap0) lap))))
+			  '(byte-goto byte-return)))
+	       (cond ((and (not (eq tmp lap0))
+			   (or (eq (car lap0) 'byte-goto)
+			       (eq (car tmp) 'byte-goto)))
+		      (byte-compile-log-lap "  %s [%s]\t-->\t%s"
+					    (car lap0) tmp tmp)
+		      (if (eq (car tmp) 'byte-return)
+			  (setcar lap0 'byte-return))
+		      (setcdr lap0 (cdr tmp))
+		      (setq keep-going t))))
+	      ;;
+	      ;; goto-*-else-pop X ... X: goto-if-* --> whatever
+	      ;; goto-*-else-pop X ... X: discard --> whatever
+	      ;;
+	      ((and (memq (car lap0) '(byte-goto-if-nil-else-pop
+				       byte-goto-if-not-nil-else-pop))
+		    (memq (car (car (setq tmp (cdr (memq (cdr lap0) lap)))))
+			  (eval-when-compile
+			   (cons 'byte-discard byte-conditional-ops)))
+		    (not (eq lap0 (car tmp))))
+	       (setq tmp2 (car tmp))
+	       (setq tmp3 (assq (car lap0) '((byte-goto-if-nil-else-pop
+					      byte-goto-if-nil)
+					     (byte-goto-if-not-nil-else-pop
+					      byte-goto-if-not-nil))))
+	       (if (memq (car tmp2) tmp3)
+		   (progn (setcar lap0 (car tmp2))
+			  (setcdr lap0 (cdr tmp2))
+			  (byte-compile-log-lap "  %s-else-pop [%s]\t-->\t%s"
+						(car lap0) tmp2 lap0))
+		 ;; Get rid of the -else-pop's and jump one step further.
+		 (or (eq 'TAG (car (nth 1 tmp)))
+		     (setcdr tmp (cons (byte-compile-make-tag)
+				       (cdr tmp))))
+		 (byte-compile-log-lap "  %s [%s]\t-->\t%s <skip>"
+				       (car lap0) tmp2 (nth 1 tmp3))
+		 (setcar lap0 (nth 1 tmp3))
+		 (setcdr lap0 (nth 1 tmp)))
+	       (setq keep-going t))
+	      ;;
+	      ;; const goto-X ... X: goto-if-* --> whatever
+	      ;; const goto-X ... X: discard   --> whatever
+	      ;;
+	      ((and (eq (car lap0) 'byte-constant)
+		    (eq (car lap1) 'byte-goto)
+		    (memq (car (car (setq tmp (cdr (memq (cdr lap1) lap)))))
+			  (eval-when-compile
+			    (cons 'byte-discard byte-conditional-ops)))
+		    (not (eq lap1 (car tmp))))
+	       (setq tmp2 (car tmp))
+	       (cond ((memq (car tmp2)
+			    (if (null (car (cdr lap0)))
+				'(byte-goto-if-nil byte-goto-if-nil-else-pop)
+			      '(byte-goto-if-not-nil
+				byte-goto-if-not-nil-else-pop)))
+		      (byte-compile-log-lap "  %s goto [%s]\t-->\t%s %s"
+					    lap0 tmp2 lap0 tmp2)
+		      (setcar lap1 (car tmp2))
+		      (setcdr lap1 (cdr tmp2))
+		      ;; Let next step fix the (const,goto-if*) sequence.
+		      (setq rest (cons nil rest)))
+		     (t
+		      ;; Jump one step further
+		      (byte-compile-log-lap
+		       "  %s goto [%s]\t-->\t<deleted> goto <skip>"
+		       lap0 tmp2)
+		      (or (eq 'TAG (car (nth 1 tmp)))
+			  (setcdr tmp (cons (byte-compile-make-tag)
+					    (cdr tmp))))
+		      (setcdr lap1 (car (cdr tmp)))
+		      (setq lap (delq lap0 lap))))
+	       (setq keep-going t))
+	      ;;
+	      ;; X: varref-Y    ...     varset-Y goto-X  -->
+	      ;; X: varref-Y Z: ... dup varset-Y goto-Z
+	      ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
+	      ;; (This is so usual for while loops that it is worth handling).
+	      ;;
+	      ((and (eq (car lap1) 'byte-varset)
+		    (eq (car lap2) 'byte-goto)
+		    (not (memq (cdr lap2) rest)) ;Backwards jump
+		    (eq (car (car (setq tmp (cdr (memq (cdr lap2) lap)))))
+			'byte-varref)
+		    (eq (cdr (car tmp)) (cdr lap1))
+		    (not (memq (car (cdr lap1)) byte-boolean-vars)))
+	       ;;(byte-compile-log-lap "  Pulled %s to end of loop" (car tmp))
+	       (let ((newtag (byte-compile-make-tag)))
+		 (byte-compile-log-lap
+		  "  %s: %s ... %s %s\t-->\t%s: %s %s: ... %s %s %s"
+		  (nth 1 (cdr lap2)) (car tmp)
+                  lap1 lap2
+		  (nth 1 (cdr lap2)) (car tmp)
+		  (nth 1 newtag) 'byte-dup lap1
+		  (cons 'byte-goto newtag)
+		  )
+		 (setcdr rest (cons (cons 'byte-dup 0) (cdr rest)))
+		 (setcdr tmp (cons (setcdr lap2 newtag) (cdr tmp))))
+	       (setq add-depth 1)
+	       (setq keep-going t))
+	      ;;
+	      ;; goto-X Y: ... X: goto-if*-Y  -->  goto-if-not-*-X+1 Y:
+	      ;; (This can pull the loop test to the end of the loop)
+	      ;;
+	      ((and (eq (car lap0) 'byte-goto)
+		    (eq (car lap1) 'TAG)
+		    (eq lap1
+			(cdr (car (setq tmp (cdr (memq (cdr lap0) lap))))))
+		    (memq (car (car tmp))
+			  '(byte-goto byte-goto-if-nil byte-goto-if-not-nil
+				      byte-goto-if-nil-else-pop)))
+;;	       (byte-compile-log-lap "  %s %s, %s %s  --> moved conditional"
+;;				     lap0 lap1 (cdr lap0) (car tmp))
+	       (let ((newtag (byte-compile-make-tag)))
+		 (byte-compile-log-lap
+		  "%s %s: ... %s: %s\t-->\t%s ... %s:"
+		  lap0 (nth 1 lap1) (nth 1 (cdr lap0)) (car tmp)
+		  (cons (cdr (assq (car (car tmp))
+				   '((byte-goto-if-nil . byte-goto-if-not-nil)
+				     (byte-goto-if-not-nil . byte-goto-if-nil)
+				     (byte-goto-if-nil-else-pop .
+				      byte-goto-if-not-nil-else-pop)
+				     (byte-goto-if-not-nil-else-pop .
+				      byte-goto-if-nil-else-pop))))
+			newtag)
+		  
+		  (nth 1 newtag)
+		  )
+		 (setcdr tmp (cons (setcdr lap0 newtag) (cdr tmp)))
+		 (if (eq (car (car tmp)) 'byte-goto-if-nil-else-pop)
+		     ;; We can handle this case but not the -if-not-nil case,
+		     ;; because we won't know which non-nil constant to push.
+		   (setcdr rest (cons (cons 'byte-constant
+					    (byte-compile-get-constant nil))
+				      (cdr rest))))
+	       (setcar lap0 (nth 1 (memq (car (car tmp))
+					 '(byte-goto-if-nil-else-pop
+					   byte-goto-if-not-nil
+					   byte-goto-if-nil
+					   byte-goto-if-not-nil
+					   byte-goto byte-goto))))
+	       )
+	       (setq keep-going t))
+	      )
+	(setq rest (cdr rest)))
+      )
+    ;; Cleanup stage:
+    ;; Rebuild byte-compile-constants / byte-compile-variables.
+    ;; Simple optimizations that would inhibit other optimizations if they
+    ;; were done in the optimizing loop, and optimizations which there is no
+    ;;  need to do more than once.
+    (setq byte-compile-constants nil
+	  byte-compile-variables nil)
+    (setq rest lap)
+    (while rest
+      (setq lap0 (car rest)
+	    lap1 (nth 1 rest))
+      (if (memq (car lap0) byte-constref-ops)
+	  (if (eq (cdr lap0) 'byte-constant)
+	      (or (memq (cdr lap0) byte-compile-variables)
+		  (setq byte-compile-variables (cons (cdr lap0)
+						     byte-compile-variables)))
+	    (or (memq (cdr lap0) byte-compile-constants)
+		(setq byte-compile-constants (cons (cdr lap0)
+						   byte-compile-constants)))))
+      (cond (;;
+	     ;; const-C varset-X const-C  -->  const-C dup varset-X
+	     ;; const-C varbind-X const-C  -->  const-C dup varbind-X
+	     ;;
+	     (and (eq (car lap0) 'byte-constant)
+		  (eq (car (nth 2 rest)) 'byte-constant)
+		  (eq (cdr lap0) (car (nth 2 rest)))
+		  (memq (car lap1) '(byte-varbind byte-varset)))
+	     (byte-compile-log-lap "  %s %s %s\t-->\t%s dup %s"
+				   lap0 lap1 lap0 lap0 lap1)
+	     (setcar (cdr (cdr rest)) (cons (car lap1) (cdr lap1)))
+	     (setcar (cdr rest) (cons 'byte-dup 0))
+	     (setq add-depth 1))
+	    ;;
+	    ;; const-X  [dup/const-X ...]   -->  const-X  [dup ...] dup
+	    ;; varref-X [dup/varref-X ...]  -->  varref-X [dup ...] dup
+	    ;;
+	    ((memq (car lap0) '(byte-constant byte-varref))
+	     (setq tmp rest
+		   tmp2 nil)
+	     (while (progn
+		      (while (eq 'byte-dup (car (car (setq tmp (cdr tmp))))))
+		      (and (eq (cdr lap0) (cdr (car tmp)))
+			   (eq (car lap0) (car (car tmp)))))
+	       (setcar tmp (cons 'byte-dup 0))
+	       (setq tmp2 t))
+	     (if tmp2
+		 (byte-compile-log-lap
+		  "  %s [dup/%s]... %s\t-->\t%s dup..." lap0 lap0 lap0)))
+	    ;;
+	    ;; unbind-N unbind-M  -->  unbind-(N+M)
+	    ;;
+	    ((and (eq 'byte-unbind (car lap0))
+		  (eq 'byte-unbind (car lap1)))
+	     (byte-compile-log-lap "  %s %s\t-->\t%s" lap0 lap1
+				   (cons 'byte-unbind
+					 (+ (cdr lap0) (cdr lap1))))
+	     (setq keep-going t)
+	     (setq lap (delq lap0 lap))
+	     (setcdr lap1 (+ (cdr lap1) (cdr lap0))))
+	    )
+      (setq rest (cdr rest)))
+    (setq byte-compile-maxdepth (+ byte-compile-maxdepth add-depth)))
+  lap)
+
+(provide 'byte-optimize)
+
+
+;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
+;; itself, compile some of its most used recursive functions (at load time).
+;;
+(eval-when-compile
+ (or (compiled-function-p (symbol-function 'byte-optimize-form))
+     (assq 'byte-code (symbol-function 'byte-optimize-form))
+     (let ((byte-optimize nil)
+	   (byte-compile-warnings nil))
+       (mapcar '(lambda (x)
+		  (or noninteractive (message "compiling %s..." x))
+		  (byte-compile x)
+		  (or noninteractive (message "compiling %s...done" x)))
+	       '(byte-optimize-form
+		 byte-optimize-body
+		 byte-optimize-predicate
+		 byte-optimize-binary-predicate
+		 ;; Inserted some more than necessary, to speed it up.
+		 byte-optimize-form-code-walker
+		 byte-optimize-lapcode))))
+ nil)