1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler.
3 ;;; Copyright (c) 1991 Free Software Foundation, Inc.
5 ;; Author: Jamie Zawinski <jwz@lucid.com>
6 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation; either version 2, or (at your option)
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs; see the file COPYING. If not, write to
23 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
27 ;;; ========================================================================
28 ;;; "No matter how hard you try, you can't make a racehorse out of a pig.
29 ;;; you can, however, make a faster pig."
31 ;;; Or, to put it another way, the emacs byte compiler is a VW Bug. This code
32 ;;; makes it be a VW Bug with fuel injection and a turbocharger... You're
33 ;;; still not going to make it go faster than 70 mph, but it might be easier
39 ;;; (apply '(lambda (x &rest y) ...) 1 (foo))
41 ;;; collapse common subexpressions
43 ;;; maintain a list of functions known not to access any global variables
44 ;;; (actually, give them a 'dynamically-safe property) and then
45 ;;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
46 ;;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
47 ;;; by recursing on this, we might be able to eliminate the entire let.
48 ;;; However certain variables should never have their bindings optimized
49 ;;; away, because they affect everything.
50 ;;; (put 'debug-on-error 'binding-is-magic t)
51 ;;; (put 'debug-on-abort 'binding-is-magic t)
52 ;;; (put 'inhibit-quit 'binding-is-magic t)
53 ;;; (put 'quit-flag 'binding-is-magic t)
56 ;;; Simple defsubsts often produce forms like
57 ;;; (let ((v1 (f1)) (v2 (f2)) ...)
59 ;;; It would be nice if we could optimize this to
60 ;;; (FN (f1) (f2) ...)
61 ;;; but we can't unless FN is dynamically-safe (it might be dynamically
62 ;;; referring to the bindings that the lambda arglist established.)
63 ;;; One of the uncountable lossages introduced by dynamic scope...
65 ;;; Maybe there should be a control-structure that says "turn on
66 ;;; fast-and-loose type-assumptive optimizations here." Then when
67 ;;; we see a form like (car foo) we can from then on assume that
68 ;;; the variable foo is of type cons, and optimize based on that.
69 ;;; But, this won't win much because of (you guessed it) dynamic
70 ;;; scope. Anything down the stack could change the value.
72 ;;; It would be nice if redundant sequences could be factored out as well,
73 ;;; when they are known to have no side-effects:
74 ;;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
75 ;;; but beware of traps like
76 ;;; (cons (list x y) (list x y))
78 ;;; Tail-recursion elimination is not really possible in Emacs Lisp.
79 ;;; Tail-recursion elimination is almost always impossible when all variables
80 ;;; have dynamic scope, but given that the "return" byteop requires the
81 ;;; binding stack to be empty (rather than emptying it itself), there can be
82 ;;; no truly tail-recursive Emacs Lisp functions that take any arguments or
83 ;;; make any bindings.
85 ;;; Here is an example of an Emacs Lisp function which could safely be
86 ;;; byte-compiled tail-recursively:
88 ;;; (defun tail-map (fn list)
90 ;;; (funcall fn (car list))
91 ;;; (tail-map fn (cdr list)))))
93 ;;; However, if there was even a single let-binding around the COND,
94 ;;; it could not be byte-compiled, because there would be an "unbind"
95 ;;; byte-op between the final "call" and "return." Adding a
96 ;;; Bunbind_all byteop would fix this.
98 ;;; (defun foo (x y z) ... (foo a b c))
99 ;;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
100 ;;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
101 ;;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
103 ;;; this also can be considered tail recursion:
105 ;;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
106 ;;; could generalize this by doing the optimization
107 ;;; (goto X) ... X: (return) --> (return)
109 ;;; But this doesn't solve all of the problems: although by doing tail-
110 ;;; recursion elimination in this way, the call-stack does not grow, the
111 ;;; binding-stack would grow with each recursive step, and would eventually
112 ;;; overflow. I don't believe there is any way around this without lexical
115 ;;; Wouldn't it be nice if Emacs Lisp had lexical scope.
117 ;;; Idea: the form (lexical-scope) in a file means that the file may be
118 ;;; compiled lexically. This proclamation is file-local. Then, within
119 ;;; that file, "let" would establish lexical bindings, and "let-dynamic"
120 ;;; would do things the old way. (Or we could use CL "declare" forms.)
121 ;;; We'd have to notice defvars and defconsts, since those variables should
122 ;;; always be dynamic, and attempting to do a lexical binding of them
123 ;;; should simply do a dynamic binding instead.
124 ;;; But! We need to know about variables that were not necessarily defvarred
125 ;;; in the file being compiled (doing a boundp check isn't good enough.)
126 ;;; Fdefvar() would have to be modified to add something to the plist.
128 ;;; A major disadvantage of this scheme is that the interpreter and compiler
129 ;;; would have different semantics for files compiled with (dynamic-scope).
130 ;;; Since this would be a file-local optimization, there would be no way to
131 ;;; modify the interpreter to obey this (unless the loader was hacked
132 ;;; in some grody way, but that's a really bad idea.)
134 ;;; Really the Right Thing is to make lexical scope the default across
135 ;;; the board, in the interpreter and compiler, and just FIX all of
136 ;;; the code that relies on dynamic scope of non-defvarred variables.
140 (defun byte-compile-log-lap-1 (format &rest args)
141 (if (aref byte-code-vector 0)
142 (error "The old version of the disassembler is loaded. Reload new-bytecomp as well."))
144 (apply 'format format
146 (mapcar '(lambda (arg)
147 (if (not (consp arg))
148 (if (and (symbolp arg)
149 (string-match "^byte-" (symbol-name arg)))
150 (intern (substring (symbol-name arg) 5))
152 (if (integerp (setq c (car arg)))
153 (error "non-symbolic byte-op %s" c))
156 (setq a (cond ((memq c byte-goto-ops)
157 (car (cdr (cdr arg))))
158 ((memq c byte-constref-ops)
161 (setq c (symbol-name c))
162 (if (string-match "^byte-." c)
163 (setq c (intern (substring c 5)))))
164 (if (eq c 'constant) (setq c 'const))
165 (if (and (eq (cdr arg) 0)
166 (not (memq c '(unbind call const))))
168 (format "(%s %s)" c a))))
171 (defmacro byte-compile-log-lap (format-string &rest args)
173 '(memq byte-optimize-log '(t byte))
174 (cons 'byte-compile-log-lap-1
175 (cons format-string args))))
178 ;;; byte-compile optimizers to support inlining
180 (put 'inline 'byte-optimizer 'byte-optimize-inline-handler)
182 (defun byte-optimize-inline-handler (form)
183 "byte-optimize-handler for the `inline' special-form."
187 (let ((fn (car-safe sexp)))
188 (if (and (symbolp fn)
189 (or (cdr (assq fn byte-compile-function-environment))
191 (not (or (cdr (assq fn byte-compile-macro-environment))
192 (and (consp (setq fn (symbol-function fn)))
193 (eq (car fn) 'macro))
195 (byte-compile-inline-expand sexp)
200 ;; Splice the given lap code into the current instruction stream.
201 ;; If it has any labels in it, you're responsible for making sure there
202 ;; are no collisions, and that byte-compile-tag-number is reasonable
203 ;; after this is spliced in. The provided list is destroyed.
204 (defun byte-inline-lapcode (lap)
205 (setq byte-compile-output (nconc (nreverse lap) byte-compile-output)))
208 (defun byte-compile-inline-expand (form)
209 (let* ((name (car form))
210 (fn (or (cdr (assq name byte-compile-function-environment))
211 (and (fboundp name) (symbol-function name)))))
214 (byte-compile-warn "attempt to inline %s before it was defined" name)
217 (if (and (consp fn) (eq (car fn) 'autoload))
219 (if (and (consp fn) (eq (car fn) 'autoload))
220 (error "file \"%s\" didn't define \"%s\"" (nth 1 fn) name))
222 (byte-compile-inline-expand (cons fn (cdr form)))
223 (if (compiled-function-p fn)
224 (cons (list 'lambda (aref fn 0)
225 (list 'byte-code (aref fn 1) (aref fn 2) (aref fn 3)))
227 (if (not (eq (car fn) 'lambda)) (error "%s is not a lambda" name))
228 (cons fn (cdr form)))))))
230 ;;; ((lambda ...) ...)
232 (defun byte-compile-unfold-lambda (form &optional name)
233 (or name (setq name "anonymous lambda"))
234 (let ((lambda (car form))
236 (if (compiled-function-p lambda)
237 (setq lambda (list 'lambda (aref lambda 0)
238 (list 'byte-code (aref lambda 1)
239 (aref lambda 2) (aref lambda 3)))))
240 (let ((arglist (nth 1 lambda))
241 (body (cdr (cdr lambda)))
244 (if (and (stringp (car body)) (cdr body))
245 (setq body (cdr body)))
246 (if (and (consp (car body)) (eq 'interactive (car (car body))))
247 (setq body (cdr body)))
249 (cond ((eq (car arglist) '&optional)
250 ;; ok, I'll let this slide because funcall_lambda() does...
251 ;; (if optionalp (error "multiple &optional keywords in %s" name))
252 (if restp (error "&optional found after &rest in %s" name))
253 (if (null (cdr arglist))
254 (error "nothing after &optional in %s" name))
256 ((eq (car arglist) '&rest)
257 ;; ...but it is by no stretch of the imagination a reasonable
258 ;; thing that funcall_lambda() allows (&rest x y) and
259 ;; (&rest x &optional y) in arglists.
260 (if (null (cdr arglist))
261 (error "nothing after &rest in %s" name))
262 (if (cdr (cdr arglist))
263 (error "multiple vars after &rest in %s" name))
266 (setq bindings (cons (list (car arglist)
267 (and values (cons 'list values)))
270 ((and (not optionalp) (null values))
271 (byte-compile-warn "attempt to open-code %s with too few arguments" name)
272 (setq arglist nil values 'too-few))
274 (setq bindings (cons (list (car arglist) (car values))
276 values (cdr values))))
277 (setq arglist (cdr arglist)))
280 (or (eq values 'too-few)
282 "attempt to open-code %s with too many arguments" name))
286 (cons 'let (cons (nreverse bindings) body))
287 (cons 'progn body))))
288 (byte-compile-log " %s\t==>\t%s" form newform)
292 ;;; implementing source-level optimizers
294 (defun byte-optimize-form-code-walker (form for-effect)
296 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
297 ;; we need to have special knowledge of the syntax of the special forms
298 ;; like let and defun (that's why they're special forms :-). (Actually,
299 ;; the important aspect is that they are subrs that don't evaluate all of
302 (let ((fn (car-safe form))
304 (cond ((not (consp form))
305 (if (not (and for-effect
306 (or byte-compile-delete-errors
312 (byte-compile-warn "malformed quote form: %s"
313 (prin1-to-string form)))
314 ;; map (quote nil) to nil to simplify optimizer logic.
315 ;; map quoted constants to nil if for-effect (just because).
319 ((or (compiled-function-p fn)
320 (eq 'lambda (car-safe fn)))
321 (byte-compile-unfold-lambda form))
322 ((memq fn '(let let*))
323 ;; recursively enter the optimizer for the bindings and body
324 ;; of a let or let*. This for depth-firstness: forms that
325 ;; are more deeply nested are optimized first.
328 (mapcar '(lambda (binding)
329 (if (symbolp binding)
331 (if (cdr (cdr binding))
332 (byte-compile-warn "malformed let binding: %s"
333 (prin1-to-string binding)))
335 (byte-optimize-form (nth 1 binding) nil))))
337 (byte-optimize-body (cdr (cdr form)) for-effect))))
340 (mapcar '(lambda (clause)
343 (byte-optimize-form (car clause) nil)
344 (byte-optimize-body (cdr clause) for-effect))
345 (byte-compile-warn "malformed cond form: %s"
346 (prin1-to-string clause))
350 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
353 (setq tmp (byte-optimize-body (cdr form) for-effect))
354 (if (cdr tmp) (cons 'progn tmp) (car tmp)))
355 (byte-optimize-form (nth 1 form) for-effect)))
359 (cons (byte-optimize-form (nth 1 form) for-effect)
360 (byte-optimize-body (cdr (cdr form)) t)))
361 (byte-optimize-form (nth 1 form) for-effect)))
364 (cons (byte-optimize-form (nth 1 form) t)
365 (cons (byte-optimize-form (nth 2 form) for-effect)
366 (byte-optimize-body (cdr (cdr (cdr form))) t)))))
368 ((memq fn '(save-excursion save-restriction))
369 ;; those subrs which have an implicit progn; it's not quite good
370 ;; enough to treat these like normal function calls.
371 ;; This can turn (save-excursion ...) into (save-excursion) which
372 ;; will be optimized away in the lap-optimize pass.
373 (cons fn (byte-optimize-body (cdr form) for-effect)))
375 ((eq fn 'with-output-to-temp-buffer)
376 ;; this is just like the above, except for the first argument.
379 (byte-optimize-form (nth 1 form) nil)
380 (byte-optimize-body (cdr (cdr form)) for-effect))))
384 (cons (byte-optimize-form (nth 1 form) nil)
386 (byte-optimize-form (nth 2 form) for-effect)
387 (byte-optimize-body (nthcdr 3 form) for-effect)))))
389 ((memq fn '(and or)) ; remember, and/or are control structures.
390 ;; take forms off the back until we can't any more.
391 ;; In the future it could concievably be a problem that the
392 ;; subexpressions of these forms are optimized in the reverse
393 ;; order, but it's ok for now.
395 (let ((backwards (reverse (cdr form))))
396 (while (and backwards
397 (null (setcar backwards
398 (byte-optimize-form (car backwards)
400 (setq backwards (cdr backwards)))
401 (if (and (cdr form) (null backwards))
403 " all subforms of %s called for effect; deleted" form))
405 (cons fn (nreverse backwards))))
406 (cons fn (mapcar 'byte-optimize-form (cdr form)))))
408 ((eq fn 'interactive)
409 (byte-compile-warn "misplaced interactive spec: %s"
410 (prin1-to-string form))
413 ((memq fn '(defun defmacro function
414 condition-case save-window-excursion))
415 ;; These forms are compiled as constants or by breaking out
416 ;; all the subexpressions and compiling them separately.
419 ((eq fn 'unwind-protect)
420 ;; the "protected" part of an unwind-protect is compiled (and thus
421 ;; optimized) as a top-level form, so don't do it here. But the
422 ;; non-protected part has the same for-effect status as the
423 ;; unwind-protect itself. (The protected part is always for effect,
424 ;; but that isn't handled properly yet.)
426 (cons (byte-optimize-form (nth 1 form) for-effect)
430 ;; the body of a catch is compiled (and thus optimized) as a
431 ;; top-level form, so don't do it here. The tag is never
432 ;; for-effect. The body should have the same for-effect status
433 ;; as the catch form itself, but that isn't handled properly yet.
435 (cons (byte-optimize-form (nth 1 form) nil)
438 ;; If optimization is on, this is the only place that macros are
439 ;; expanded. If optimization is off, then macroexpansion happens
440 ;; in byte-compile-form. Otherwise, the macros are already expanded
441 ;; by the time that is reached.
443 (setq form (macroexpand form
444 byte-compile-macro-environment))))
445 (byte-optimize-form form for-effect))
448 (or (eq 'mocklisp (car-safe fn)) ; ha!
449 (byte-compile-warn "%s is a malformed function"
450 (prin1-to-string fn)))
453 ((and for-effect (setq tmp (get fn 'side-effect-free))
454 (or byte-compile-delete-errors
457 (byte-compile-warn "%s called for effect"
458 (prin1-to-string form))
460 (byte-compile-log " %s called for effect; deleted" fn)
461 ;; appending a nil here might not be necessary, but it can't hurt.
463 (cons 'progn (append (cdr form) '(nil))) t))
466 ;; Otherwise, no args can be considered to be for-effect,
467 ;; even if the called function is for-effect, because we
468 ;; don't know anything about that function.
469 (cons fn (mapcar 'byte-optimize-form (cdr form)))))))
472 (defun byte-optimize-form (form &optional for-effect)
473 "The source-level pass of the optimizer."
475 ;; First, optimize all sub-forms of this one.
476 (setq form (byte-optimize-form-code-walker form for-effect))
478 ;; after optimizing all subforms, optimize this form until it doesn't
479 ;; optimize any further. This means that some forms will be passed through
480 ;; the optimizer many times, but that's necessary to make the for-effect
481 ;; processing do as much as possible.
484 (if (and (consp form)
487 ;; we don't have any of these yet, but we might.
488 (setq opt (get (car form) 'byte-for-effect-optimizer)))
489 (setq opt (get (car form) 'byte-optimizer)))
490 (not (eq form (setq new (funcall opt form)))))
492 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
493 (byte-compile-log " %s\t==>\t%s" form new)
494 (setq new (byte-optimize-form new for-effect))
499 (defun byte-optimize-body (forms all-for-effect)
500 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
501 ;; forms, all but the last of which are optimized with the assumption that
502 ;; they are being called for effect. the last is for-effect as well if
503 ;; all-for-effect is true. returns a new list of forms.
508 (setq fe (or all-for-effect (cdr rest)))
509 (setq new (and (car rest) (byte-optimize-form (car rest) fe)))
510 (if (or new (not fe))
511 (setq result (cons new result)))
512 (setq rest (cdr rest)))
516 ;;; some source-level optimizers
518 ;;; when writing optimizers, be VERY careful that the optimizer returns
519 ;;; something not EQ to its argument if and ONLY if it has made a change.
520 ;;; This implies that you cannot simply destructively modify the list;
521 ;;; you must return something not EQ to it if you make an optimization.
523 ;;; It is now safe to optimize code such that it introduces new bindings.
525 ;; I'd like this to be a defsubst, but let's not be self-referental...
526 (defmacro byte-compile-trueconstp (form)
527 ;; Returns non-nil if FORM is a non-nil constant.
528 (` (cond ((consp (, form)) (eq (car (, form)) 'quote))
529 ((not (symbolp (, form))))
532 ;; If the function is being called with constant numeric args,
533 ;; evaluate as much as possible at compile-time. This optimizer
534 ;; assumes that the function is associative, like + or *.
535 (defun byte-optimize-associative-math (form)
540 (if (numberp (car rest))
541 (setq constants (cons (car rest) constants))
542 (setq args (cons (car rest) args)))
543 (setq rest (cdr rest)))
547 (apply (car form) constants)
549 (cons (car form) (nreverse args))
551 (apply (car form) constants))
554 ;; If the function is being called with constant numeric args,
555 ;; evaluate as much as possible at compile-time. This optimizer
556 ;; assumes that the function is nonassociative, like - or /.
557 (defun byte-optimize-nonassociative-math (form)
558 (if (or (not (numberp (car (cdr form))))
559 (not (numberp (car (cdr (cdr form))))))
561 (let ((constant (car (cdr form)))
562 (rest (cdr (cdr form))))
563 (while (numberp (car rest))
564 (setq constant (funcall (car form) constant (car rest))
567 (cons (car form) (cons constant rest))
570 ;;(defun byte-optimize-associative-two-args-math (form)
571 ;; (setq form (byte-optimize-associative-math form))
573 ;; (byte-optimize-two-args-left form)
576 ;;(defun byte-optimize-nonassociative-two-args-math (form)
577 ;; (setq form (byte-optimize-nonassociative-math form))
579 ;; (byte-optimize-two-args-right form)
582 (defun byte-optimize-delay-constants-math (form start fun)
583 ;; Merge all FORM's constants from number START, call FUN on them
584 ;; and put the result at the end.
585 (let ((rest (nthcdr (1- start) form)))
586 (while (cdr (setq rest (cdr rest)))
587 (if (numberp (car rest))
589 (setq form (copy-sequence form)
590 rest (nthcdr (1- start) form))
591 (while (setq rest (cdr rest))
592 (cond ((numberp (car rest))
593 (setq constants (cons (car rest) constants))
595 (setq form (nconc (delq nil form)
596 (list (apply fun (nreverse constants))))))))
599 (defun byte-optimize-plus (form)
600 (setq form (byte-optimize-delay-constants-math form 1 '+))
601 (if (memq 0 form) (setq form (delq 0 (copy-sequence form))))
602 ;;(setq form (byte-optimize-associative-two-args-math form))
603 (cond ((null (cdr form))
607 ;;; It is not safe to delete the function entirely
608 ;;; (actually, it would be safe if we know the sole arg
609 ;;; is not a marker).
610 ;; ((null (cdr (cdr form))) (nth 1 form))
613 (defun byte-optimize-minus (form)
614 ;; Put constants at the end, except the last constant.
615 (setq form (byte-optimize-delay-constants-math form 2 '+))
616 ;; Now only first and last element can be a number.
617 (let ((last (car (reverse (nthcdr 3 form)))))
619 ;; (- x y ... 0) --> (- x y ...)
620 (setq form (copy-sequence form))
621 (setcdr (cdr (cdr form)) (delq 0 (nthcdr 3 form))))
622 ;; If form is (- CONST foo... CONST), merge first and last.
623 ((and (numberp (nth 1 form))
625 (setq form (nconc (list '- (- (nth 1 form) last) (nth 2 form))
626 (delq last (copy-sequence (nthcdr 3 form))))))))
627 ;;; It is not safe to delete the function entirely
628 ;;; (actually, it would be safe if we know the sole arg
629 ;;; is not a marker).
630 ;;; (if (eq (nth 2 form) 0)
631 ;;; (nth 1 form) ; (- x 0) --> x
632 (byte-optimize-predicate
633 (if (and (null (cdr (cdr (cdr form))))
634 (eq (nth 1 form) 0)) ; (- 0 x) --> (- x)
635 (cons (car form) (cdr (cdr form)))
640 (defun byte-optimize-multiply (form)
641 (setq form (byte-optimize-delay-constants-math form 1 '*))
642 ;; If there is a constant in FORM, it is now the last element.
643 (cond ((null (cdr form)) 1)
644 ;;; It is not safe to delete the function entirely
645 ;;; (actually, it would be safe if we know the sole arg
646 ;;; is not a marker or if it appears in other arithmetic).
647 ;;; ((null (cdr (cdr form))) (nth 1 form))
648 ((let ((last (car (reverse form))))
649 (cond ((eq 0 last) (list 'progn (cdr form)))
650 ((eq 1 last) (delq 1 (copy-sequence form)))
651 ((eq -1 last) (list '- (delq -1 (copy-sequence form))))
653 (memq t (mapcar 'symbolp (cdr form))))
654 (prog1 (setq form (delq 2 (copy-sequence form)))
655 (while (not (symbolp (car (setq form (cdr form))))))
656 (setcar form (list '+ (car form) (car form)))))
659 (defsubst byte-compile-butlast (form)
660 (nreverse (cdr (reverse form))))
662 (defun byte-optimize-divide (form)
663 (setq form (byte-optimize-delay-constants-math form 2 '*))
664 (let ((last (car (reverse (cdr (cdr form))))))
667 (setq form (byte-compile-butlast form)))
668 ((numberp (nth 1 form))
669 (setq form (cons (car form)
670 (cons (/ (nth 1 form) last)
671 (byte-compile-butlast (cdr (cdr form)))))
674 ;;; ((null (cdr (cdr form)))
677 (append '(progn) (cdr (cdr form)) '(0)))
679 (list '- (if (nthcdr 3 form)
680 (byte-compile-butlast form)
684 (defun byte-optimize-logmumble (form)
685 (setq form (byte-optimize-delay-constants-math form 1 (car form)))
686 (byte-optimize-predicate
688 (setq form (if (eq (car form) 'logand)
689 (cons 'progn (cdr form))
690 (delq 0 (copy-sequence form)))))
691 ((and (eq (car-safe form) 'logior)
693 (delq -1 (copy-sequence form)))
697 (defun byte-optimize-binary-predicate (form)
698 (if (byte-compile-constp (nth 1 form))
699 (if (byte-compile-constp (nth 2 form))
701 (list 'quote (eval form))
703 ;; This can enable some lapcode optimizations.
704 (list (car form) (nth 2 form) (nth 1 form)))
707 (defun byte-optimize-predicate (form)
711 (setq ok (byte-compile-constp (car rest))
715 (list 'quote (eval form))
719 (defun byte-optimize-identity (form)
720 (if (and (cdr form) (null (cdr (cdr form))))
722 (byte-compile-warn "identity called with %d arg%s, but requires 1"
724 (if (= 1 (length (cdr form))) "" "s"))
727 (put 'identity 'byte-optimizer 'byte-optimize-identity)
729 (put '+ 'byte-optimizer 'byte-optimize-plus)
730 (put '* 'byte-optimizer 'byte-optimize-multiply)
731 (put '- 'byte-optimizer 'byte-optimize-minus)
732 (put '/ 'byte-optimizer 'byte-optimize-divide)
733 (put 'max 'byte-optimizer 'byte-optimize-associative-math)
734 (put 'min 'byte-optimizer 'byte-optimize-associative-math)
736 (put '= 'byte-optimizer 'byte-optimize-binary-predicate)
737 (put 'eq 'byte-optimizer 'byte-optimize-binary-predicate)
738 (put 'eql 'byte-optimizer 'byte-optimize-binary-predicate)
739 (put 'equal 'byte-optimizer 'byte-optimize-binary-predicate)
740 (put 'string= 'byte-optimizer 'byte-optimize-binary-predicate)
741 (put 'string-equal 'byte-optimizer 'byte-optimize-binary-predicate)
743 (put '< 'byte-optimizer 'byte-optimize-predicate)
744 (put '> 'byte-optimizer 'byte-optimize-predicate)
745 (put '<= 'byte-optimizer 'byte-optimize-predicate)
746 (put '>= 'byte-optimizer 'byte-optimize-predicate)
747 (put '1+ 'byte-optimizer 'byte-optimize-predicate)
748 (put '1- 'byte-optimizer 'byte-optimize-predicate)
749 (put 'not 'byte-optimizer 'byte-optimize-predicate)
750 (put 'null 'byte-optimizer 'byte-optimize-predicate)
751 (put 'memq 'byte-optimizer 'byte-optimize-predicate)
752 (put 'consp 'byte-optimizer 'byte-optimize-predicate)
753 (put 'listp 'byte-optimizer 'byte-optimize-predicate)
754 (put 'symbolp 'byte-optimizer 'byte-optimize-predicate)
755 (put 'stringp 'byte-optimizer 'byte-optimize-predicate)
756 (put 'string< 'byte-optimizer 'byte-optimize-predicate)
757 (put 'string-lessp 'byte-optimizer 'byte-optimize-predicate)
759 (put 'logand 'byte-optimizer 'byte-optimize-logmumble)
760 (put 'logior 'byte-optimizer 'byte-optimize-logmumble)
761 (put 'logxor 'byte-optimizer 'byte-optimize-logmumble)
762 (put 'lognot 'byte-optimizer 'byte-optimize-predicate)
764 (put 'car 'byte-optimizer 'byte-optimize-predicate)
765 (put 'cdr 'byte-optimizer 'byte-optimize-predicate)
766 (put 'car-safe 'byte-optimizer 'byte-optimize-predicate)
767 (put 'cdr-safe 'byte-optimizer 'byte-optimize-predicate)
770 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
771 ;; take care of this? - Jamie
772 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
773 ;; so arithmetic optimizers recognize the numerinc constant. - Hallvard
774 (put 'quote 'byte-optimizer 'byte-optimize-quote)
775 (defun byte-optimize-quote (form)
776 (if (or (consp (nth 1 form))
777 (and (symbolp (nth 1 form))
778 (not (memq (nth 1 form) '(nil t)))))
782 (defun byte-optimize-zerop (form)
783 (cond ((numberp (nth 1 form))
785 (byte-compile-delete-errors
786 (list '= (nth 1 form) 0))
789 (put 'zerop 'byte-optimizer 'byte-optimize-zerop)
791 (defun byte-optimize-and (form)
792 ;; Simplify if less than 2 args.
793 ;; if there is a literal nil in the args to `and', throw it and following
794 ;; forms away, and surround the `and' with (progn ... nil).
795 (cond ((null (cdr form)))
799 (prog1 (setq form (copy-sequence form))
801 (setq form (cdr form)))
804 ((null (cdr (cdr form)))
806 ((byte-optimize-predicate form))))
808 (defun byte-optimize-or (form)
809 ;; Throw away nil's, and simplify if less than 2 args.
810 ;; If there is a literal non-nil constant in the args to `or', throw away all
813 (setq form (delq nil (copy-sequence form))))
815 (while (cdr (setq rest (cdr rest)))
816 (if (byte-compile-trueconstp (car rest))
817 (setq form (copy-sequence form)
818 rest (setcdr (memq (car rest) form) nil))))
820 (byte-optimize-predicate form)
823 (defun byte-optimize-cond (form)
824 ;; if any clauses have a literal nil as their test, throw them away.
825 ;; if any clause has a literal non-nil constant as its test, throw
826 ;; away all following clauses.
828 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
829 (while (setq rest (assq nil (cdr form)))
830 (setq form (delq rest (copy-sequence form))))
831 (if (memq nil (cdr form))
832 (setq form (delq nil (copy-sequence form))))
834 (while (setq rest (cdr rest))
835 (cond ((byte-compile-trueconstp (car-safe (car rest)))
836 (cond ((eq rest (cdr form))
839 (if (cdr (cdr (car rest)))
840 (cons 'progn (cdr (car rest)))
844 (setq form (copy-sequence form))
845 (setcdr (memq (car rest) form) nil)))
848 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
849 (if (eq 'cond (car-safe form))
850 (let ((clauses (cdr form)))
851 (if (and (consp (car clauses))
852 (null (cdr (car clauses))))
853 (list 'or (car (car clauses))
855 (cons (car form) (cdr (cdr form)))))
859 (defun byte-optimize-if (form)
860 ;; (if <true-constant> <then> <else...>) ==> <then>
861 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
862 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
863 ;; (if <test> <then> nil) ==> (if <test> <then>)
864 (let ((clause (nth 1 form)))
865 (cond ((byte-compile-trueconstp clause)
869 (cons 'progn (nthcdr 3 form))
872 (if (equal '(nil) (nthcdr 3 form))
873 (list 'if clause (nth 2 form))
875 ((or (nth 3 form) (nthcdr 4 form))
876 (list 'if (list 'not clause)
878 (cons 'progn (nthcdr 3 form))
881 (list 'progn clause nil)))))
883 (defun byte-optimize-while (form)
887 (put 'and 'byte-optimizer 'byte-optimize-and)
888 (put 'or 'byte-optimizer 'byte-optimize-or)
889 (put 'cond 'byte-optimizer 'byte-optimize-cond)
890 (put 'if 'byte-optimizer 'byte-optimize-if)
891 (put 'while 'byte-optimizer 'byte-optimize-while)
893 ;; byte-compile-negation-optimizer lives in bytecomp.el
894 (put '/= 'byte-optimizer 'byte-compile-negation-optimizer)
895 (put 'atom 'byte-optimizer 'byte-compile-negation-optimizer)
896 (put 'nlistp 'byte-optimizer 'byte-compile-negation-optimizer)
899 (defun byte-optimize-funcall (form)
900 ;; (funcall '(lambda ...) ...) ==> ((lambda ...) ...)
901 ;; (funcall 'foo ...) ==> (foo ...)
902 (let ((fn (nth 1 form)))
903 (if (memq (car-safe fn) '(quote function))
904 (cons (nth 1 fn) (cdr (cdr form)))
907 (defun byte-optimize-apply (form)
908 ;; If the last arg is a literal constant, turn this into a funcall.
909 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
910 (let ((fn (nth 1 form))
911 (last (nth (1- (length form)) form))) ; I think this really is fastest
912 (or (if (or (null last)
913 (eq (car-safe last) 'quote))
914 (if (listp (nth 1 last))
915 (let ((butlast (nreverse (cdr (reverse (cdr (cdr form)))))))
916 (nconc (list 'funcall fn) butlast
917 (mapcar '(lambda (x) (list 'quote x)) (nth 1 last))))
919 "last arg to apply can't be a literal atom: %s"
920 (prin1-to-string last))
924 (put 'funcall 'byte-optimizer 'byte-optimize-funcall)
925 (put 'apply 'byte-optimizer 'byte-optimize-apply)
928 (put 'let 'byte-optimizer 'byte-optimize-letX)
929 (put 'let* 'byte-optimizer 'byte-optimize-letX)
930 (defun byte-optimize-letX (form)
931 (cond ((null (nth 1 form))
933 (cons 'progn (cdr (cdr form))))
934 ((or (nth 2 form) (nthcdr 3 form))
937 ((eq (car form) 'let)
938 (append '(progn) (mapcar 'car (mapcar 'cdr (nth 1 form))) '(nil)))
940 (let ((binds (reverse (nth 1 form))))
941 (list 'let* (reverse (cdr binds)) (nth 1 (car binds)) nil)))))
944 (put 'nth 'byte-optimizer 'byte-optimize-nth)
945 (defun byte-optimize-nth (form)
946 (if (memq (nth 1 form) '(0 1))
947 (list 'car (if (zerop (nth 1 form))
949 (list 'cdr (nth 2 form))))
950 (byte-optimize-predicate form)))
952 (put 'nthcdr 'byte-optimizer 'byte-optimize-nthcdr)
953 (defun byte-optimize-nthcdr (form)
954 (let ((count (nth 1 form)))
955 (if (not (memq count '(0 1 2)))
956 (byte-optimize-predicate form)
957 (setq form (nth 2 form))
958 (while (natnump (setq count (1- count)))
959 (setq form (list 'cdr form)))
962 ;;; enumerating those functions which need not be called if the returned
963 ;;; value is not used. That is, something like
964 ;;; (progn (list (something-with-side-effects) (yow))
966 ;;; may safely be turned into
967 ;;; (progn (progn (something-with-side-effects) (yow))
969 ;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
971 ;;; I wonder if I missed any :-\)
972 (let ((side-effect-free-fns
973 '(% * + / /= 1+ < <= = > >= append aref ash assoc assq boundp
974 buffer-file-name buffer-local-variables buffer-modified-p
975 buffer-substring capitalize car cdr concat coordinates-in-window-p
976 copy-marker count-lines documentation downcase elt fboundp featurep
977 file-directory-p file-exists-p file-locked-p file-name-absolute-p
978 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
979 format get get-buffer get-buffer-window getenv get-file-buffer length
980 logand logior lognot logxor lsh marker-buffer max member memq min mod
981 next-window nth nthcdr previous-window rassq regexp-quote reverse
982 string< string= string-lessp string-equal substring user-variable-p
983 window-buffer window-edges window-height window-hscroll window-width
985 ;; could also add plusp, minusp, signum. If anyone ever defines
986 ;; these, they will certainly be side-effect free.
987 (side-effect-and-error-free-fns
988 '(arrayp atom bobp bolp buffer-end buffer-list buffer-size
989 buffer-string bufferp char-or-string-p commandp cons consp
990 current-buffer dot dot-marker eobp eolp eq eql equal
991 get-largest-window identity integerp integer-or-marker-p
992 interactive-p keymapp list listp make-marker mark mark-marker
993 markerp minibuffer-window natnump nlistp not null numberp
994 one-window-p point point-marker processp selected-window sequencep
995 stringp subrp symbolp syntax-table-p vector vectorp windowp)))
996 (while side-effect-free-fns
997 (put (car side-effect-free-fns) 'side-effect-free t)
998 (setq side-effect-free-fns (cdr side-effect-free-fns)))
999 (while side-effect-and-error-free-fns
1000 (put (car side-effect-and-error-free-fns) 'side-effect-free 'error-free)
1001 (setq side-effect-and-error-free-fns (cdr side-effect-and-error-free-fns)))
1005 (defun byte-compile-splice-in-already-compiled-code (form)
1006 ;; form is (byte-code "..." [...] n)
1007 (if (not (memq byte-optimize '(t lap)))
1008 (byte-compile-normal-call form)
1009 (byte-inline-lapcode
1010 (byte-decompile-bytecode-1 (nth 1 form) (nth 2 form) t))
1011 (setq byte-compile-maxdepth (max (+ byte-compile-depth (nth 3 form))
1012 byte-compile-maxdepth))
1013 (setq byte-compile-depth (1+ byte-compile-depth))))
1015 (put 'byte-code 'byte-compile 'byte-compile-splice-in-already-compiled-code)
1018 (defconst byte-constref-ops
1019 '(byte-constant byte-constant2 byte-varref byte-varset byte-varbind))
1021 ;;; This function extracts the bitfields from variable-length opcodes.
1022 ;;; Originally defined in disass.el (which no longer uses it.)
1024 (defun disassemble-offset ()
1026 ;; fetch and return the offset for the current opcode.
1027 ;; return NIL if this opcode has no offset
1028 ;; OP, PTR and BYTES are used and set dynamically
1032 (cond ((< op byte-nth)
1033 (let ((tem (logand op 7)))
1034 (setq op (logand op 248))
1036 (setq ptr (1+ ptr)) ;offset in next byte
1039 (setq ptr (1+ ptr)) ;offset in next 2 bytes
1041 (progn (setq ptr (1+ ptr))
1042 (lsh (aref bytes ptr) 8))))
1043 (t tem)))) ;offset was in opcode
1044 ((>= op byte-constant)
1045 (prog1 (- op byte-constant) ;offset in opcode
1046 (setq op byte-constant)))
1047 ((and (>= op byte-constant2)
1048 (<= op byte-goto-if-not-nil-else-pop))
1049 (setq ptr (1+ ptr)) ;offset in next 2 bytes
1051 (progn (setq ptr (1+ ptr))
1052 (lsh (aref bytes ptr) 8))))
1053 ((and (>= op byte-listN)
1054 (<= op byte-insertN))
1055 (setq ptr (1+ ptr)) ;offset in next byte
1059 ;;; This de-compiler is used for inline expansion of compiled functions,
1060 ;;; and by the disassembler.
1062 (defun byte-decompile-bytecode (bytes constvec)
1063 "Turns BYTECODE into lapcode, refering to CONSTVEC."
1064 (let ((byte-compile-constants nil)
1065 (byte-compile-variables nil)
1066 (byte-compile-tag-number 0))
1067 (byte-decompile-bytecode-1 bytes constvec)))
1069 ;; As byte-decompile-bytecode, but updates
1070 ;; byte-compile-{constants, variables, tag-number}.
1071 ;; If the optional 3rd arg is true, then `return' opcodes are replaced
1072 ;; with `goto's destined for the end of the code.
1073 (defun byte-decompile-bytecode-1 (bytes constvec &optional make-splicable)
1074 (let ((length (length bytes))
1075 (ptr 0) optr tag tags op offset
1079 (while (not (= ptr length))
1080 (setq op (aref bytes ptr)
1082 offset (disassemble-offset)) ; this does dynamic-scope magic
1083 (setq op (aref byte-code-vector op))
1084 (cond ((memq op byte-goto-ops)
1087 (cdr (or (assq offset tags)
1090 (byte-compile-make-tag))
1092 ((cond ((eq op 'byte-constant2) (setq op 'byte-constant) t)
1093 ((memq op byte-constref-ops)))
1094 (setq tmp (aref constvec offset)
1095 offset (if (eq op 'byte-constant)
1096 (byte-compile-get-constant tmp)
1097 (or (assq tmp byte-compile-variables)
1098 (car (setq byte-compile-variables
1100 byte-compile-variables)))))))
1101 ((and make-splicable
1102 (eq op 'byte-return))
1103 (if (= ptr (1- length))
1105 (setq offset (or endtag (setq endtag (byte-compile-make-tag)))
1107 ;; lap = ( [ (pc . (op . arg)) ]* )
1108 (setq lap (cons (cons optr (cons op (or offset 0)))
1110 (setq ptr (1+ ptr)))
1111 ;; take off the dummy nil op that we replaced a trailing "return" with.
1114 (cond ((setq tmp (assq (car (car rest)) tags))
1115 ;; this addr is jumped to
1116 (setcdr rest (cons (cons nil (cdr tmp))
1118 (setq tags (delq tmp tags))
1119 (setq rest (cdr rest))))
1120 (setq rest (cdr rest))))
1121 (if tags (error "optimizer error: missed tags %s" tags))
1122 (if (null (car (cdr (car lap))))
1123 (setq lap (cdr lap)))
1125 (setq lap (cons (cons nil endtag) lap)))
1126 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1127 (mapcar 'cdr (nreverse lap))))
1130 ;;; peephole optimizer
1132 (defconst byte-tagref-ops (cons 'TAG byte-goto-ops))
1134 (defconst byte-conditional-ops
1135 '(byte-goto-if-nil byte-goto-if-not-nil byte-goto-if-nil-else-pop
1136 byte-goto-if-not-nil-else-pop))
1138 (defconst byte-after-unbind-ops
1139 '(byte-constant byte-dup
1140 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1141 byte-eq byte-equal byte-not
1142 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1144 ;; How about other side-effect-free-ops? Is it safe to move an
1145 ;; error invocation (such as from nth) out of an unwind-protect?
1146 "Byte-codes that can be moved past an unbind."))
1148 (defconst byte-compile-side-effect-and-error-free-ops
1149 '(byte-constant byte-dup byte-symbolp byte-consp byte-stringp byte-listp
1150 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1151 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1152 byte-point-min byte-following-char byte-preceding-char
1153 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1154 byte-current-buffer byte-interactive-p))
1156 (defconst byte-compile-side-effect-free-ops
1158 '(byte-varref byte-nth byte-memq byte-car byte-cdr byte-length byte-aref
1159 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1160 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1161 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1162 byte-buffer-substring byte-string= byte-string< byte-nthcdr byte-elt
1163 byte-member byte-assq byte-quo byte-rem)
1164 byte-compile-side-effect-and-error-free-ops))
1166 ;;; This piece of shit is because of the way DEFVAR_BOOL() variables work.
1167 ;;; Consider the code
1169 ;;; (defun foo (flag)
1170 ;;; (let ((old-pop-ups pop-up-windows)
1171 ;;; (pop-up-windows flag))
1172 ;;; (cond ((not (eq pop-up-windows old-pop-ups))
1173 ;;; (setq old-pop-ups pop-up-windows)
1176 ;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1177 ;;; something else. But if we optimize
1180 ;;; varbind pop-up-windows
1181 ;;; varref pop-up-windows
1186 ;;; varbind pop-up-windows
1189 ;;; we break the program, because it will appear that pop-up-windows and
1190 ;;; old-pop-ups are not EQ when really they are. So we have to know what
1191 ;;; the BOOL variables are, and not perform this optimization on them.
1193 (defconst byte-boolean-vars
1194 '(abbrev-all-caps abbrevs-changed byte-metering-on
1195 check-protected-fields completion-auto-help completion-ignore-case
1196 cursor-in-echo-area debug-on-next-call debug-on-quit
1197 defining-kbd-macro delete-exited-processes
1198 enable-recursive-minibuffers indent-tabs-mode
1199 insert-default-directory inverse-video load-in-progress
1200 menu-prompting mode-line-inverse-video no-redraw-on-reenter
1201 noninteractive parse-sexp-ignore-comments pop-up-frames
1202 pop-up-windows print-escape-newlines print-escape-newlines
1203 truncate-partial-width-windows visible-bell vms-stmlf-recfm
1204 words-include-escapes x-save-under)
1205 "DEFVAR_BOOL variables. Giving these any non-nil value sets them to t.
1206 If this does not enumerate all DEFVAR_BOOL variables, the byte-optimizer
1207 may generate incorrect code.")
1209 (defun byte-optimize-lapcode (lap &optional for-effect)
1210 "Simple peephole optimizer. LAP is both modified and returned."
1214 (keep-going 'first-time)
1217 (side-effect-free (if byte-compile-delete-errors
1218 byte-compile-side-effect-free-ops
1219 byte-compile-side-effect-and-error-free-ops)))
1221 (or (eq keep-going 'first-time)
1222 (byte-compile-log-lap " ---- next pass"))
1226 (setq lap0 (car rest)
1230 ;; You may notice that sequences like "dup varset discard" are
1231 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1232 ;; You may be tempted to change this; resist that temptation.
1234 ;; <side-effect-free> pop --> <deleted>
1236 ;; const-X pop --> <deleted>
1237 ;; varref-X pop --> <deleted>
1238 ;; dup pop --> <deleted>
1240 ((and (eq 'byte-discard (car lap1))
1241 (memq (car lap0) side-effect-free))
1243 (setq tmp (aref byte-stack+-info (symbol-value (car lap0))))
1244 (setq rest (cdr rest))
1246 (byte-compile-log-lap
1247 " %s discard\t-->\t<deleted>" lap0)
1248 (setq lap (delq lap0 (delq lap1 lap))))
1250 (byte-compile-log-lap
1251 " %s discard\t-->\t<deleted> discard" lap0)
1252 (setq lap (delq lap0 lap)))
1254 (byte-compile-log-lap
1255 " %s discard\t-->\tdiscard discard" lap0)
1256 (setcar lap0 'byte-discard)
1258 ((error "Optimizer error: too much on the stack"))))
1260 ;; goto*-X X: --> X:
1262 ((and (memq (car lap0) byte-goto-ops)
1263 (eq (cdr lap0) lap1))
1264 (cond ((eq (car lap0) 'byte-goto)
1265 (setq lap (delq lap0 lap))
1266 (setq tmp "<deleted>"))
1267 ((memq (car lap0) byte-goto-always-pop-ops)
1268 (setcar lap0 (setq tmp 'byte-discard))
1270 ((error "Depth conflict at tag %d" (nth 2 lap0))))
1271 (and (memq byte-optimize-log '(t byte))
1272 (byte-compile-log " (goto %s) %s:\t-->\t%s %s:"
1273 (nth 1 lap1) (nth 1 lap1)
1275 (setq keep-going t))
1277 ;; varset-X varref-X --> dup varset-X
1278 ;; varbind-X varref-X --> dup varbind-X
1279 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1280 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1281 ;; The latter two can enable other optimizations.
1283 ((and (eq 'byte-varref (car lap2))
1284 (eq (cdr lap1) (cdr lap2))
1285 (memq (car lap1) '(byte-varset byte-varbind)))
1286 (if (and (setq tmp (memq (car (cdr lap2)) byte-boolean-vars))
1287 (not (eq (car lap0) 'byte-constant)))
1290 (if (memq (car lap0) '(byte-constant byte-dup))
1292 (setq tmp (if (or (not tmp)
1293 (memq (car (cdr lap0)) '(nil t)))
1295 (byte-compile-get-constant t)))
1296 (byte-compile-log-lap " %s %s %s\t-->\t%s %s %s"
1297 lap0 lap1 lap2 lap0 lap1
1298 (cons (car lap0) tmp))
1299 (setcar lap2 (car lap0))
1301 (byte-compile-log-lap " %s %s\t-->\tdup %s" lap1 lap2 lap1)
1302 (setcar lap2 (car lap1))
1303 (setcar lap1 'byte-dup)
1305 ;; The stack depth gets locally increased, so we will
1306 ;; increase maxdepth in case depth = maxdepth here.
1307 ;; This can cause the third argument to byte-code to
1308 ;; be larger than necessary.
1309 (setq add-depth 1))))
1311 ;; dup varset-X discard --> varset-X
1312 ;; dup varbind-X discard --> varbind-X
1313 ;; (the varbind variant can emerge from other optimizations)
1315 ((and (eq 'byte-dup (car lap0))
1316 (eq 'byte-discard (car lap2))
1317 (memq (car lap1) '(byte-varset byte-varbind)))
1318 (byte-compile-log-lap " dup %s discard\t-->\t%s" lap1 lap1)
1321 (setq lap (delq lap0 (delq lap2 lap))))
1323 ;; not goto-X-if-nil --> goto-X-if-non-nil
1324 ;; not goto-X-if-non-nil --> goto-X-if-nil
1326 ;; it is wrong to do the same thing for the -else-pop variants.
1328 ((and (eq 'byte-not (car lap0))
1329 (or (eq 'byte-goto-if-nil (car lap1))
1330 (eq 'byte-goto-if-not-nil (car lap1))))
1331 (byte-compile-log-lap " not %s\t-->\t%s"
1334 (if (eq (car lap1) 'byte-goto-if-nil)
1335 'byte-goto-if-not-nil
1338 (setcar lap1 (if (eq (car lap1) 'byte-goto-if-nil)
1339 'byte-goto-if-not-nil
1341 (setq lap (delq lap0 lap))
1342 (setq keep-going t))
1344 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1345 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1347 ;; it is wrong to do the same thing for the -else-pop variants.
1349 ((and (or (eq 'byte-goto-if-nil (car lap0))
1350 (eq 'byte-goto-if-not-nil (car lap0))) ; gotoX
1351 (eq 'byte-goto (car lap1)) ; gotoY
1352 (eq (cdr lap0) lap2)) ; TAG X
1353 (let ((inverse (if (eq 'byte-goto-if-nil (car lap0))
1354 'byte-goto-if-not-nil 'byte-goto-if-nil)))
1355 (byte-compile-log-lap " %s %s %s:\t-->\t%s %s:"
1357 (cons inverse (cdr lap1)) lap2)
1358 (setq lap (delq lap0 lap))
1359 (setcar lap1 inverse)
1360 (setq keep-going t)))
1362 ;; const goto-if-* --> whatever
1364 ((and (eq 'byte-constant (car lap0))
1365 (memq (car lap1) byte-conditional-ops))
1366 (cond ((if (or (eq (car lap1) 'byte-goto-if-nil)
1367 (eq (car lap1) 'byte-goto-if-nil-else-pop))
1369 (not (car (cdr lap0))))
1370 (byte-compile-log-lap " %s %s\t-->\t<deleted>"
1372 (setq rest (cdr rest)
1373 lap (delq lap0 (delq lap1 lap))))
1375 (if (memq (car lap1) byte-goto-always-pop-ops)
1377 (byte-compile-log-lap " %s %s\t-->\t%s"
1378 lap0 lap1 (cons 'byte-goto (cdr lap1)))
1379 (setq lap (delq lap0 lap)))
1380 (byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1
1381 (cons 'byte-goto (cdr lap1))))
1382 (setcar lap1 'byte-goto)))
1383 (setq keep-going t))
1385 ;; varref-X varref-X --> varref-X dup
1386 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1387 ;; We don't optimize the const-X variations on this here,
1388 ;; because that would inhibit some goto optimizations; we
1389 ;; optimize the const-X case after all other optimizations.
1391 ((and (eq 'byte-varref (car lap0))
1393 (setq tmp (cdr rest))
1394 (while (eq (car (car tmp)) 'byte-dup)
1395 (setq tmp (cdr tmp)))
1397 (eq (cdr lap0) (cdr (car tmp)))
1398 (eq 'byte-varref (car (car tmp))))
1399 (if (memq byte-optimize-log '(t byte))
1401 (setq tmp2 (cdr rest))
1402 (while (not (eq tmp tmp2))
1403 (setq tmp2 (cdr tmp2)
1404 str (concat str " dup")))
1405 (byte-compile-log-lap " %s%s %s\t-->\t%s%s dup"
1406 lap0 str lap0 lap0 str)))
1408 (setcar (car tmp) 'byte-dup)
1409 (setcdr (car tmp) 0)
1412 ;; TAG1: TAG2: --> TAG1: <deleted>
1413 ;; (and other references to TAG2 are replaced with TAG1)
1415 ((and (eq (car lap0) 'TAG)
1416 (eq (car lap1) 'TAG))
1417 (and (memq byte-optimize-log '(t byte))
1418 (byte-compile-log " adjascent tags %d and %d merged"
1419 (nth 1 lap1) (nth 1 lap0)))
1421 (while (setq tmp2 (rassq lap0 tmp3))
1423 (setq tmp3 (cdr (memq tmp2 tmp3))))
1424 (setq lap (delq lap0 lap)
1427 ;; unused-TAG: --> <deleted>
1429 ((and (eq 'TAG (car lap0))
1430 (not (rassq lap0 lap)))
1431 (and (memq byte-optimize-log '(t byte))
1432 (byte-compile-log " unused tag %d removed" (nth 1 lap0)))
1433 (setq lap (delq lap0 lap)
1436 ;; goto ... --> goto <delete until TAG or end>
1437 ;; return ... --> return <delete until TAG or end>
1439 ((and (memq (car lap0) '(byte-goto byte-return))
1440 (not (memq (car lap1) '(TAG nil))))
1443 (opt-p (memq byte-optimize-log '(t lap)))
1445 (while (and (setq tmp (cdr tmp))
1446 (not (eq 'TAG (car (car tmp)))))
1447 (if opt-p (setq deleted (cons (car tmp) deleted)
1448 str (concat str " %s")
1452 (if (eq 'TAG (car (car tmp)))
1453 (format "%d:" (cdr (car tmp)))
1454 (or (car tmp) ""))))
1456 (apply 'byte-compile-log-lap-1
1458 " %s\t-->\t%s <deleted> %s")
1460 (nconc (nreverse deleted)
1461 (list tagstr lap0 tagstr)))
1462 (byte-compile-log-lap
1463 " %s <%d unreachable op%s> %s\t-->\t%s <deleted> %s"
1464 lap0 i (if (= i 1) "" "s")
1465 tagstr lap0 tagstr))))
1467 (setq keep-going t))
1469 ;; <safe-op> unbind --> unbind <safe-op>
1470 ;; (this may enable other optimizations.)
1472 ((and (eq 'byte-unbind (car lap1))
1473 (memq (car lap0) byte-after-unbind-ops))
1474 (byte-compile-log-lap " %s %s\t-->\t%s %s" lap0 lap1 lap1 lap0)
1476 (setcar (cdr rest) lap0)
1477 (setq keep-going t))
1479 ;; varbind-X unbind-N --> discard unbind-(N-1)
1480 ;; save-excursion unbind-N --> unbind-(N-1)
1481 ;; save-restriction unbind-N --> unbind-(N-1)
1483 ((and (eq 'byte-unbind (car lap1))
1484 (memq (car lap0) '(byte-varbind byte-save-excursion
1485 byte-save-restriction))
1487 (if (zerop (setcdr lap1 (1- (cdr lap1))))
1489 (if (eq (car lap0) 'byte-varbind)
1490 (setcar rest (cons 'byte-discard 0))
1491 (setq lap (delq lap0 lap)))
1492 (byte-compile-log-lap " %s %s\t-->\t%s %s"
1493 lap0 (cons (car lap1) (1+ (cdr lap1)))
1494 (if (eq (car lap0) 'byte-varbind)
1497 (if (and (/= 0 (cdr lap1))
1498 (eq (car lap0) 'byte-varbind))
1501 (setq keep-going t))
1503 ;; goto*-X ... X: goto-Y --> goto*-Y
1504 ;; goto-X ... X: return --> return
1506 ((and (memq (car lap0) byte-goto-ops)
1507 (memq (car (setq tmp (nth 1 (memq (cdr lap0) lap))))
1508 '(byte-goto byte-return)))
1509 (cond ((and (not (eq tmp lap0))
1510 (or (eq (car lap0) 'byte-goto)
1511 (eq (car tmp) 'byte-goto)))
1512 (byte-compile-log-lap " %s [%s]\t-->\t%s"
1514 (if (eq (car tmp) 'byte-return)
1515 (setcar lap0 'byte-return))
1516 (setcdr lap0 (cdr tmp))
1517 (setq keep-going t))))
1519 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1520 ;; goto-*-else-pop X ... X: discard --> whatever
1522 ((and (memq (car lap0) '(byte-goto-if-nil-else-pop
1523 byte-goto-if-not-nil-else-pop))
1524 (memq (car (car (setq tmp (cdr (memq (cdr lap0) lap)))))
1526 (cons 'byte-discard byte-conditional-ops)))
1527 (not (eq lap0 (car tmp))))
1528 (setq tmp2 (car tmp))
1529 (setq tmp3 (assq (car lap0) '((byte-goto-if-nil-else-pop
1531 (byte-goto-if-not-nil-else-pop
1532 byte-goto-if-not-nil))))
1533 (if (memq (car tmp2) tmp3)
1534 (progn (setcar lap0 (car tmp2))
1535 (setcdr lap0 (cdr tmp2))
1536 (byte-compile-log-lap " %s-else-pop [%s]\t-->\t%s"
1537 (car lap0) tmp2 lap0))
1538 ;; Get rid of the -else-pop's and jump one step further.
1539 (or (eq 'TAG (car (nth 1 tmp)))
1540 (setcdr tmp (cons (byte-compile-make-tag)
1542 (byte-compile-log-lap " %s [%s]\t-->\t%s <skip>"
1543 (car lap0) tmp2 (nth 1 tmp3))
1544 (setcar lap0 (nth 1 tmp3))
1545 (setcdr lap0 (nth 1 tmp)))
1546 (setq keep-going t))
1548 ;; const goto-X ... X: goto-if-* --> whatever
1549 ;; const goto-X ... X: discard --> whatever
1551 ((and (eq (car lap0) 'byte-constant)
1552 (eq (car lap1) 'byte-goto)
1553 (memq (car (car (setq tmp (cdr (memq (cdr lap1) lap)))))
1555 (cons 'byte-discard byte-conditional-ops)))
1556 (not (eq lap1 (car tmp))))
1557 (setq tmp2 (car tmp))
1558 (cond ((memq (car tmp2)
1559 (if (null (car (cdr lap0)))
1560 '(byte-goto-if-nil byte-goto-if-nil-else-pop)
1561 '(byte-goto-if-not-nil
1562 byte-goto-if-not-nil-else-pop)))
1563 (byte-compile-log-lap " %s goto [%s]\t-->\t%s %s"
1564 lap0 tmp2 lap0 tmp2)
1565 (setcar lap1 (car tmp2))
1566 (setcdr lap1 (cdr tmp2))
1567 ;; Let next step fix the (const,goto-if*) sequence.
1568 (setq rest (cons nil rest)))
1570 ;; Jump one step further
1571 (byte-compile-log-lap
1572 " %s goto [%s]\t-->\t<deleted> goto <skip>"
1574 (or (eq 'TAG (car (nth 1 tmp)))
1575 (setcdr tmp (cons (byte-compile-make-tag)
1577 (setcdr lap1 (car (cdr tmp)))
1578 (setq lap (delq lap0 lap))))
1579 (setq keep-going t))
1581 ;; X: varref-Y ... varset-Y goto-X -->
1582 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1583 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1584 ;; (This is so usual for while loops that it is worth handling).
1586 ((and (eq (car lap1) 'byte-varset)
1587 (eq (car lap2) 'byte-goto)
1588 (not (memq (cdr lap2) rest)) ;Backwards jump
1589 (eq (car (car (setq tmp (cdr (memq (cdr lap2) lap)))))
1591 (eq (cdr (car tmp)) (cdr lap1))
1592 (not (memq (car (cdr lap1)) byte-boolean-vars)))
1593 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1594 (let ((newtag (byte-compile-make-tag)))
1595 (byte-compile-log-lap
1596 " %s: %s ... %s %s\t-->\t%s: %s %s: ... %s %s %s"
1597 (nth 1 (cdr lap2)) (car tmp)
1599 (nth 1 (cdr lap2)) (car tmp)
1600 (nth 1 newtag) 'byte-dup lap1
1601 (cons 'byte-goto newtag)
1603 (setcdr rest (cons (cons 'byte-dup 0) (cdr rest)))
1604 (setcdr tmp (cons (setcdr lap2 newtag) (cdr tmp))))
1606 (setq keep-going t))
1608 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1609 ;; (This can pull the loop test to the end of the loop)
1611 ((and (eq (car lap0) 'byte-goto)
1612 (eq (car lap1) 'TAG)
1614 (cdr (car (setq tmp (cdr (memq (cdr lap0) lap))))))
1615 (memq (car (car tmp))
1616 '(byte-goto byte-goto-if-nil byte-goto-if-not-nil
1617 byte-goto-if-nil-else-pop)))
1618 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1619 ;; lap0 lap1 (cdr lap0) (car tmp))
1620 (let ((newtag (byte-compile-make-tag)))
1621 (byte-compile-log-lap
1622 "%s %s: ... %s: %s\t-->\t%s ... %s:"
1623 lap0 (nth 1 lap1) (nth 1 (cdr lap0)) (car tmp)
1624 (cons (cdr (assq (car (car tmp))
1625 '((byte-goto-if-nil . byte-goto-if-not-nil)
1626 (byte-goto-if-not-nil . byte-goto-if-nil)
1627 (byte-goto-if-nil-else-pop .
1628 byte-goto-if-not-nil-else-pop)
1629 (byte-goto-if-not-nil-else-pop .
1630 byte-goto-if-nil-else-pop))))
1635 (setcdr tmp (cons (setcdr lap0 newtag) (cdr tmp)))
1636 (if (eq (car (car tmp)) 'byte-goto-if-nil-else-pop)
1637 ;; We can handle this case but not the -if-not-nil case,
1638 ;; because we won't know which non-nil constant to push.
1639 (setcdr rest (cons (cons 'byte-constant
1640 (byte-compile-get-constant nil))
1642 (setcar lap0 (nth 1 (memq (car (car tmp))
1643 '(byte-goto-if-nil-else-pop
1644 byte-goto-if-not-nil
1646 byte-goto-if-not-nil
1647 byte-goto byte-goto))))
1649 (setq keep-going t))
1651 (setq rest (cdr rest)))
1654 ;; Rebuild byte-compile-constants / byte-compile-variables.
1655 ;; Simple optimizations that would inhibit other optimizations if they
1656 ;; were done in the optimizing loop, and optimizations which there is no
1657 ;; need to do more than once.
1658 (setq byte-compile-constants nil
1659 byte-compile-variables nil)
1662 (setq lap0 (car rest)
1664 (if (memq (car lap0) byte-constref-ops)
1665 (if (eq (cdr lap0) 'byte-constant)
1666 (or (memq (cdr lap0) byte-compile-variables)
1667 (setq byte-compile-variables (cons (cdr lap0)
1668 byte-compile-variables)))
1669 (or (memq (cdr lap0) byte-compile-constants)
1670 (setq byte-compile-constants (cons (cdr lap0)
1671 byte-compile-constants)))))
1673 ;; const-C varset-X const-C --> const-C dup varset-X
1674 ;; const-C varbind-X const-C --> const-C dup varbind-X
1676 (and (eq (car lap0) 'byte-constant)
1677 (eq (car (nth 2 rest)) 'byte-constant)
1678 (eq (cdr lap0) (car (nth 2 rest)))
1679 (memq (car lap1) '(byte-varbind byte-varset)))
1680 (byte-compile-log-lap " %s %s %s\t-->\t%s dup %s"
1681 lap0 lap1 lap0 lap0 lap1)
1682 (setcar (cdr (cdr rest)) (cons (car lap1) (cdr lap1)))
1683 (setcar (cdr rest) (cons 'byte-dup 0))
1686 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1687 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1689 ((memq (car lap0) '(byte-constant byte-varref))
1693 (while (eq 'byte-dup (car (car (setq tmp (cdr tmp))))))
1694 (and (eq (cdr lap0) (cdr (car tmp)))
1695 (eq (car lap0) (car (car tmp)))))
1696 (setcar tmp (cons 'byte-dup 0))
1699 (byte-compile-log-lap
1700 " %s [dup/%s]... %s\t-->\t%s dup..." lap0 lap0 lap0)))
1702 ;; unbind-N unbind-M --> unbind-(N+M)
1704 ((and (eq 'byte-unbind (car lap0))
1705 (eq 'byte-unbind (car lap1)))
1706 (byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1
1708 (+ (cdr lap0) (cdr lap1))))
1710 (setq lap (delq lap0 lap))
1711 (setcdr lap1 (+ (cdr lap1) (cdr lap0))))
1713 (setq rest (cdr rest)))
1714 (setq byte-compile-maxdepth (+ byte-compile-maxdepth add-depth)))
1717 (provide 'byte-optimize)
1720 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
1721 ;; itself, compile some of its most used recursive functions (at load time).
1724 (or (compiled-function-p (symbol-function 'byte-optimize-form))
1725 (assq 'byte-code (symbol-function 'byte-optimize-form))
1726 (let ((byte-optimize nil)
1727 (byte-compile-warnings nil))
1728 (mapcar '(lambda (x)
1729 (or noninteractive (message "compiling %s..." x))
1731 (or noninteractive (message "compiling %s...done" x)))
1732 '(byte-optimize-form
1734 byte-optimize-predicate
1735 byte-optimize-binary-predicate
1736 ;; Inserted some more than necessary, to speed it up.
1737 byte-optimize-form-code-walker
1738 byte-optimize-lapcode))))
1741 ;;; byte-opt.el ends here