1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler.
3 ;;; Copyright (c) 1991, 1994 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 (byte-code-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 (byte-code-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 (byte-code-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 conceivably 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-referential...
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))))))
666 (cond ((= (length form) 3)
667 ;; Don't shrink to less than two arguments--would get an error.
670 (setq form (byte-compile-butlast form)))
671 ((numberp (nth 1 form))
672 (setq form (cons (car form)
673 (cons (/ (nth 1 form) last)
674 (byte-compile-butlast (cdr (cdr form)))))
677 ;;; ((null (cdr (cdr form)))
680 (append '(progn) (cdr (cdr form)) '(0)))
682 (list '- (if (nthcdr 3 form)
683 (byte-compile-butlast form)
687 (defun byte-optimize-logmumble (form)
688 (setq form (byte-optimize-delay-constants-math form 1 (car form)))
689 (byte-optimize-predicate
691 (setq form (if (eq (car form) 'logand)
692 (cons 'progn (cdr form))
693 (delq 0 (copy-sequence form)))))
694 ((and (eq (car-safe form) 'logior)
696 (delq -1 (copy-sequence form)))
700 (defun byte-optimize-binary-predicate (form)
701 (if (byte-compile-constp (nth 1 form))
702 (if (byte-compile-constp (nth 2 form))
704 (list 'quote (eval form))
706 ;; This can enable some lapcode optimizations.
707 (list (car form) (nth 2 form) (nth 1 form)))
710 (defun byte-optimize-predicate (form)
714 (setq ok (byte-compile-constp (car rest))
718 (list 'quote (eval form))
722 (defun byte-optimize-identity (form)
723 (if (and (cdr form) (null (cdr (cdr form))))
725 (byte-compile-warn "identity called with %d arg%s, but requires 1"
727 (if (= 1 (length (cdr form))) "" "s"))
730 (put 'identity 'byte-optimizer 'byte-optimize-identity)
732 (put '+ 'byte-optimizer 'byte-optimize-plus)
733 (put '* 'byte-optimizer 'byte-optimize-multiply)
734 (put '- 'byte-optimizer 'byte-optimize-minus)
735 (put '/ 'byte-optimizer 'byte-optimize-divide)
736 (put 'max 'byte-optimizer 'byte-optimize-associative-math)
737 (put 'min 'byte-optimizer 'byte-optimize-associative-math)
739 (put '= 'byte-optimizer 'byte-optimize-binary-predicate)
740 (put 'eq 'byte-optimizer 'byte-optimize-binary-predicate)
741 (put 'eql 'byte-optimizer 'byte-optimize-binary-predicate)
742 (put 'equal 'byte-optimizer 'byte-optimize-binary-predicate)
743 (put 'string= 'byte-optimizer 'byte-optimize-binary-predicate)
744 (put 'string-equal 'byte-optimizer 'byte-optimize-binary-predicate)
746 (put '< 'byte-optimizer 'byte-optimize-predicate)
747 (put '> 'byte-optimizer 'byte-optimize-predicate)
748 (put '<= 'byte-optimizer 'byte-optimize-predicate)
749 (put '>= 'byte-optimizer 'byte-optimize-predicate)
750 (put '1+ 'byte-optimizer 'byte-optimize-predicate)
751 (put '1- 'byte-optimizer 'byte-optimize-predicate)
752 (put 'not 'byte-optimizer 'byte-optimize-predicate)
753 (put 'null 'byte-optimizer 'byte-optimize-predicate)
754 (put 'memq 'byte-optimizer 'byte-optimize-predicate)
755 (put 'consp 'byte-optimizer 'byte-optimize-predicate)
756 (put 'listp 'byte-optimizer 'byte-optimize-predicate)
757 (put 'symbolp 'byte-optimizer 'byte-optimize-predicate)
758 (put 'stringp 'byte-optimizer 'byte-optimize-predicate)
759 (put 'string< 'byte-optimizer 'byte-optimize-predicate)
760 (put 'string-lessp 'byte-optimizer 'byte-optimize-predicate)
762 (put 'logand 'byte-optimizer 'byte-optimize-logmumble)
763 (put 'logior 'byte-optimizer 'byte-optimize-logmumble)
764 (put 'logxor 'byte-optimizer 'byte-optimize-logmumble)
765 (put 'lognot 'byte-optimizer 'byte-optimize-predicate)
767 (put 'car 'byte-optimizer 'byte-optimize-predicate)
768 (put 'cdr 'byte-optimizer 'byte-optimize-predicate)
769 (put 'car-safe 'byte-optimizer 'byte-optimize-predicate)
770 (put 'cdr-safe 'byte-optimizer 'byte-optimize-predicate)
773 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
774 ;; take care of this? - Jamie
775 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
776 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
777 (put 'quote 'byte-optimizer 'byte-optimize-quote)
778 (defun byte-optimize-quote (form)
779 (if (or (consp (nth 1 form))
780 (and (symbolp (nth 1 form))
781 (not (memq (nth 1 form) '(nil t)))))
785 (defun byte-optimize-zerop (form)
786 (cond ((numberp (nth 1 form))
788 (byte-compile-delete-errors
789 (list '= (nth 1 form) 0))
792 (put 'zerop 'byte-optimizer 'byte-optimize-zerop)
794 (defun byte-optimize-and (form)
795 ;; Simplify if less than 2 args.
796 ;; if there is a literal nil in the args to `and', throw it and following
797 ;; forms away, and surround the `and' with (progn ... nil).
798 (cond ((null (cdr form)))
802 (prog1 (setq form (copy-sequence form))
804 (setq form (cdr form)))
807 ((null (cdr (cdr form)))
809 ((byte-optimize-predicate form))))
811 (defun byte-optimize-or (form)
812 ;; Throw away nil's, and simplify if less than 2 args.
813 ;; If there is a literal non-nil constant in the args to `or', throw away all
816 (setq form (delq nil (copy-sequence form))))
818 (while (cdr (setq rest (cdr rest)))
819 (if (byte-compile-trueconstp (car rest))
820 (setq form (copy-sequence form)
821 rest (setcdr (memq (car rest) form) nil))))
823 (byte-optimize-predicate form)
826 (defun byte-optimize-cond (form)
827 ;; if any clauses have a literal nil as their test, throw them away.
828 ;; if any clause has a literal non-nil constant as its test, throw
829 ;; away all following clauses.
831 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
832 (while (setq rest (assq nil (cdr form)))
833 (setq form (delq rest (copy-sequence form))))
834 (if (memq nil (cdr form))
835 (setq form (delq nil (copy-sequence form))))
837 (while (setq rest (cdr rest))
838 (cond ((byte-compile-trueconstp (car-safe (car rest)))
839 (cond ((eq rest (cdr form))
842 (if (cdr (cdr (car rest)))
843 (cons 'progn (cdr (car rest)))
847 (setq form (copy-sequence form))
848 (setcdr (memq (car rest) form) nil)))
851 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
852 (if (eq 'cond (car-safe form))
853 (let ((clauses (cdr form)))
854 (if (and (consp (car clauses))
855 (null (cdr (car clauses))))
856 (list 'or (car (car clauses))
858 (cons (car form) (cdr (cdr form)))))
862 (defun byte-optimize-if (form)
863 ;; (if <true-constant> <then> <else...>) ==> <then>
864 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
865 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
866 ;; (if <test> <then> nil) ==> (if <test> <then>)
867 (let ((clause (nth 1 form)))
868 (cond ((byte-compile-trueconstp clause)
872 (cons 'progn (nthcdr 3 form))
875 (if (equal '(nil) (nthcdr 3 form))
876 (list 'if clause (nth 2 form))
878 ((or (nth 3 form) (nthcdr 4 form))
879 (list 'if (list 'not clause)
881 (cons 'progn (nthcdr 3 form))
884 (list 'progn clause nil)))))
886 (defun byte-optimize-while (form)
890 (put 'and 'byte-optimizer 'byte-optimize-and)
891 (put 'or 'byte-optimizer 'byte-optimize-or)
892 (put 'cond 'byte-optimizer 'byte-optimize-cond)
893 (put 'if 'byte-optimizer 'byte-optimize-if)
894 (put 'while 'byte-optimizer 'byte-optimize-while)
896 ;; byte-compile-negation-optimizer lives in bytecomp.el
897 (put '/= 'byte-optimizer 'byte-compile-negation-optimizer)
898 (put 'atom 'byte-optimizer 'byte-compile-negation-optimizer)
899 (put 'nlistp 'byte-optimizer 'byte-compile-negation-optimizer)
902 (defun byte-optimize-funcall (form)
903 ;; (funcall '(lambda ...) ...) ==> ((lambda ...) ...)
904 ;; (funcall 'foo ...) ==> (foo ...)
905 (let ((fn (nth 1 form)))
906 (if (memq (car-safe fn) '(quote function))
907 (cons (nth 1 fn) (cdr (cdr form)))
910 (defun byte-optimize-apply (form)
911 ;; If the last arg is a literal constant, turn this into a funcall.
912 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
913 (let ((fn (nth 1 form))
914 (last (nth (1- (length form)) form))) ; I think this really is fastest
915 (or (if (or (null last)
916 (eq (car-safe last) 'quote))
917 (if (listp (nth 1 last))
918 (let ((butlast (nreverse (cdr (reverse (cdr (cdr form)))))))
919 (nconc (list 'funcall fn) butlast
920 (mapcar '(lambda (x) (list 'quote x)) (nth 1 last))))
922 "last arg to apply can't be a literal atom: %s"
923 (prin1-to-string last))
927 (put 'funcall 'byte-optimizer 'byte-optimize-funcall)
928 (put 'apply 'byte-optimizer 'byte-optimize-apply)
931 (put 'let 'byte-optimizer 'byte-optimize-letX)
932 (put 'let* 'byte-optimizer 'byte-optimize-letX)
933 (defun byte-optimize-letX (form)
934 (cond ((null (nth 1 form))
936 (cons 'progn (cdr (cdr form))))
937 ((or (nth 2 form) (nthcdr 3 form))
940 ((eq (car form) 'let)
941 (append '(progn) (mapcar 'car (mapcar 'cdr (nth 1 form))) '(nil)))
943 (let ((binds (reverse (nth 1 form))))
944 (list 'let* (reverse (cdr binds)) (nth 1 (car binds)) nil)))))
947 (put 'nth 'byte-optimizer 'byte-optimize-nth)
948 (defun byte-optimize-nth (form)
949 (if (memq (nth 1 form) '(0 1))
950 (list 'car (if (zerop (nth 1 form))
952 (list 'cdr (nth 2 form))))
953 (byte-optimize-predicate form)))
955 (put 'nthcdr 'byte-optimizer 'byte-optimize-nthcdr)
956 (defun byte-optimize-nthcdr (form)
957 (let ((count (nth 1 form)))
958 (if (not (memq count '(0 1 2)))
959 (byte-optimize-predicate form)
960 (setq form (nth 2 form))
961 (while (natnump (setq count (1- count)))
962 (setq form (list 'cdr form)))
965 ;;; enumerating those functions which need not be called if the returned
966 ;;; value is not used. That is, something like
967 ;;; (progn (list (something-with-side-effects) (yow))
969 ;;; may safely be turned into
970 ;;; (progn (progn (something-with-side-effects) (yow))
972 ;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
974 ;;; I wonder if I missed any :-\)
975 (let ((side-effect-free-fns
976 '(% * + - / /= 1+ 1- < <= = > >= abs acos append aref ash asin atan
978 boundp buffer-file-name buffer-local-variables buffer-modified-p
980 capitalize car-less-than-car car cdr ceiling concat coordinates-in-window-p
981 copy-marker cos count-lines
982 default-boundp default-value documentation downcase
983 elt exp expt fboundp featurep
984 file-directory-p file-exists-p file-locked-p file-name-absolute-p
985 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
987 get get-buffer get-buffer-window getenv get-file-buffer
989 length log log10 logand logb logior lognot logxor lsh
990 marker-buffer max member memq min mod
991 next-window nth nthcdr number-to-string
992 parse-colon-path previous-window
993 radians-to-degrees rassq regexp-quote reverse round
994 sin sqrt string< string= string-equal string-lessp string-to-char
995 string-to-int string-to-number substring symbol-plist
996 tan upcase user-variable-p vconcat
997 window-buffer window-dedicated-p window-edges window-height
998 window-hscroll window-minibuffer-p window-width
1000 (side-effect-and-error-free-fns
1002 bobp bolp buffer-end buffer-list buffer-size buffer-string bufferp
1003 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1005 dot dot-marker eobp eolp eq eql equal eventp floatp framep
1006 get-largest-window get-lru-window
1007 identity ignore integerp integer-or-marker-p interactive-p
1008 invocation-directory invocation-name
1010 make-marker mark mark-marker markerp memory-limit minibuffer-window
1012 natnump nlistp not null number-or-marker-p numberp
1013 one-window-p overlayp
1014 point point-marker point-min point-max processp
1015 selected-window sequencep stringp subrp symbolp syntax-table-p
1016 user-full-name user-login-name user-original-login-name
1017 user-real-login-name user-real-uid user-uid
1019 window-configuration-p window-live-p windowp)))
1020 (while side-effect-free-fns
1021 (put (car side-effect-free-fns) 'side-effect-free t)
1022 (setq side-effect-free-fns (cdr side-effect-free-fns)))
1023 (while side-effect-and-error-free-fns
1024 (put (car side-effect-and-error-free-fns) 'side-effect-free 'error-free)
1025 (setq side-effect-and-error-free-fns (cdr side-effect-and-error-free-fns)))
1029 (defun byte-compile-splice-in-already-compiled-code (form)
1030 ;; form is (byte-code "..." [...] n)
1031 (if (not (memq byte-optimize '(t lap)))
1032 (byte-compile-normal-call form)
1033 (byte-inline-lapcode
1034 (byte-decompile-bytecode-1 (nth 1 form) (nth 2 form) t))
1035 (setq byte-compile-maxdepth (max (+ byte-compile-depth (nth 3 form))
1036 byte-compile-maxdepth))
1037 (setq byte-compile-depth (1+ byte-compile-depth))))
1039 (put 'byte-code 'byte-compile 'byte-compile-splice-in-already-compiled-code)
1042 (defconst byte-constref-ops
1043 '(byte-constant byte-constant2 byte-varref byte-varset byte-varbind))
1045 ;;; This function extracts the bitfields from variable-length opcodes.
1046 ;;; Originally defined in disass.el (which no longer uses it.)
1048 (defun disassemble-offset ()
1050 ;; fetch and return the offset for the current opcode.
1051 ;; return NIL if this opcode has no offset
1052 ;; OP, PTR and BYTES are used and set dynamically
1056 (cond ((< op byte-nth)
1057 (let ((tem (logand op 7)))
1058 (setq op (logand op 248))
1060 (setq ptr (1+ ptr)) ;offset in next byte
1063 (setq ptr (1+ ptr)) ;offset in next 2 bytes
1065 (progn (setq ptr (1+ ptr))
1066 (lsh (aref bytes ptr) 8))))
1067 (t tem)))) ;offset was in opcode
1068 ((>= op byte-constant)
1069 (prog1 (- op byte-constant) ;offset in opcode
1070 (setq op byte-constant)))
1071 ((and (>= op byte-constant2)
1072 (<= op byte-goto-if-not-nil-else-pop))
1073 (setq ptr (1+ ptr)) ;offset in next 2 bytes
1075 (progn (setq ptr (1+ ptr))
1076 (lsh (aref bytes ptr) 8))))
1077 ((and (>= op byte-listN)
1078 (<= op byte-insertN))
1079 (setq ptr (1+ ptr)) ;offset in next byte
1083 ;;; This de-compiler is used for inline expansion of compiled functions,
1084 ;;; and by the disassembler.
1086 (defun byte-decompile-bytecode (bytes constvec)
1087 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1088 (let ((byte-compile-constants nil)
1089 (byte-compile-variables nil)
1090 (byte-compile-tag-number 0))
1091 (byte-decompile-bytecode-1 bytes constvec)))
1093 ;; As byte-decompile-bytecode, but updates
1094 ;; byte-compile-{constants, variables, tag-number}.
1095 ;; If the optional 3rd arg is true, then `return' opcodes are replaced
1096 ;; with `goto's destined for the end of the code.
1097 (defun byte-decompile-bytecode-1 (bytes constvec &optional make-splicable)
1098 (let ((length (length bytes))
1099 (ptr 0) optr tag tags op offset
1103 (while (not (= ptr length))
1104 (setq op (aref bytes ptr)
1106 offset (disassemble-offset)) ; this does dynamic-scope magic
1107 (setq op (aref byte-code-vector op))
1108 (cond ((memq op byte-goto-ops)
1111 (cdr (or (assq offset tags)
1114 (byte-compile-make-tag))
1116 ((cond ((eq op 'byte-constant2) (setq op 'byte-constant) t)
1117 ((memq op byte-constref-ops)))
1118 (setq tmp (aref constvec offset)
1119 offset (if (eq op 'byte-constant)
1120 (byte-compile-get-constant tmp)
1121 (or (assq tmp byte-compile-variables)
1122 (car (setq byte-compile-variables
1124 byte-compile-variables)))))))
1125 ((and make-splicable
1126 (eq op 'byte-return))
1127 (if (= ptr (1- length))
1129 (setq offset (or endtag (setq endtag (byte-compile-make-tag)))
1131 ;; lap = ( [ (pc . (op . arg)) ]* )
1132 (setq lap (cons (cons optr (cons op (or offset 0)))
1134 (setq ptr (1+ ptr)))
1135 ;; take off the dummy nil op that we replaced a trailing "return" with.
1138 (cond ((setq tmp (assq (car (car rest)) tags))
1139 ;; this addr is jumped to
1140 (setcdr rest (cons (cons nil (cdr tmp))
1142 (setq tags (delq tmp tags))
1143 (setq rest (cdr rest))))
1144 (setq rest (cdr rest))))
1145 (if tags (error "optimizer error: missed tags %s" tags))
1146 (if (null (car (cdr (car lap))))
1147 (setq lap (cdr lap)))
1149 (setq lap (cons (cons nil endtag) lap)))
1150 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1151 (mapcar 'cdr (nreverse lap))))
1154 ;;; peephole optimizer
1156 (defconst byte-tagref-ops (cons 'TAG byte-goto-ops))
1158 (defconst byte-conditional-ops
1159 '(byte-goto-if-nil byte-goto-if-not-nil byte-goto-if-nil-else-pop
1160 byte-goto-if-not-nil-else-pop))
1162 (defconst byte-after-unbind-ops
1163 '(byte-constant byte-dup
1164 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1165 byte-eq byte-equal byte-not
1166 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1168 ;; How about other side-effect-free-ops? Is it safe to move an
1169 ;; error invocation (such as from nth) out of an unwind-protect?
1170 "Byte-codes that can be moved past an unbind."))
1172 (defconst byte-compile-side-effect-and-error-free-ops
1173 '(byte-constant byte-dup byte-symbolp byte-consp byte-stringp byte-listp
1174 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1175 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1176 byte-point-min byte-following-char byte-preceding-char
1177 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1178 byte-current-buffer byte-interactive-p))
1180 (defconst byte-compile-side-effect-free-ops
1182 '(byte-varref byte-nth byte-memq byte-car byte-cdr byte-length byte-aref
1183 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1184 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1185 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1186 byte-buffer-substring byte-string= byte-string< byte-nthcdr byte-elt
1187 byte-member byte-assq byte-quo byte-rem)
1188 byte-compile-side-effect-and-error-free-ops))
1190 ;;; This piece of shit is because of the way DEFVAR_BOOL() variables work.
1191 ;;; Consider the code
1193 ;;; (defun foo (flag)
1194 ;;; (let ((old-pop-ups pop-up-windows)
1195 ;;; (pop-up-windows flag))
1196 ;;; (cond ((not (eq pop-up-windows old-pop-ups))
1197 ;;; (setq old-pop-ups pop-up-windows)
1200 ;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1201 ;;; something else. But if we optimize
1204 ;;; varbind pop-up-windows
1205 ;;; varref pop-up-windows
1210 ;;; varbind pop-up-windows
1213 ;;; we break the program, because it will appear that pop-up-windows and
1214 ;;; old-pop-ups are not EQ when really they are. So we have to know what
1215 ;;; the BOOL variables are, and not perform this optimization on them.
1217 (defconst byte-boolean-vars
1218 '(abbrev-all-caps abbrevs-changed byte-metering-on
1219 check-protected-fields completion-auto-help completion-ignore-case
1220 cursor-in-echo-area debug-on-next-call debug-on-quit
1221 defining-kbd-macro delete-exited-processes
1222 enable-recursive-minibuffers
1223 highlight-nonselected-windows indent-tabs-mode
1224 insert-default-directory inverse-video load-in-progress
1225 menu-prompting mode-line-inverse-video no-redraw-on-reenter
1226 noninteractive parse-sexp-ignore-comments pop-up-frames
1227 pop-up-windows print-escape-newlines print-escape-newlines
1228 truncate-partial-width-windows visible-bell vms-stmlf-recfm
1229 words-include-escapes x-save-under)
1230 "DEFVAR_BOOL variables. Giving these any non-nil value sets them to t.
1231 If this does not enumerate all DEFVAR_BOOL variables, the byte-optimizer
1232 may generate incorrect code.")
1234 (defun byte-optimize-lapcode (lap &optional for-effect)
1235 "Simple peephole optimizer. LAP is both modified and returned."
1239 (keep-going 'first-time)
1242 (side-effect-free (if byte-compile-delete-errors
1243 byte-compile-side-effect-free-ops
1244 byte-compile-side-effect-and-error-free-ops)))
1246 (or (eq keep-going 'first-time)
1247 (byte-compile-log-lap " ---- next pass"))
1251 (setq lap0 (car rest)
1255 ;; You may notice that sequences like "dup varset discard" are
1256 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1257 ;; You may be tempted to change this; resist that temptation.
1259 ;; <side-effect-free> pop --> <deleted>
1261 ;; const-X pop --> <deleted>
1262 ;; varref-X pop --> <deleted>
1263 ;; dup pop --> <deleted>
1265 ((and (eq 'byte-discard (car lap1))
1266 (memq (car lap0) side-effect-free))
1268 (setq tmp (aref byte-stack+-info (symbol-value (car lap0))))
1269 (setq rest (cdr rest))
1271 (byte-compile-log-lap
1272 " %s discard\t-->\t<deleted>" lap0)
1273 (setq lap (delq lap0 (delq lap1 lap))))
1275 (byte-compile-log-lap
1276 " %s discard\t-->\t<deleted> discard" lap0)
1277 (setq lap (delq lap0 lap)))
1279 (byte-compile-log-lap
1280 " %s discard\t-->\tdiscard discard" lap0)
1281 (setcar lap0 'byte-discard)
1283 ((error "Optimizer error: too much on the stack"))))
1285 ;; goto*-X X: --> X:
1287 ((and (memq (car lap0) byte-goto-ops)
1288 (eq (cdr lap0) lap1))
1289 (cond ((eq (car lap0) 'byte-goto)
1290 (setq lap (delq lap0 lap))
1291 (setq tmp "<deleted>"))
1292 ((memq (car lap0) byte-goto-always-pop-ops)
1293 (setcar lap0 (setq tmp 'byte-discard))
1295 ((error "Depth conflict at tag %d" (nth 2 lap0))))
1296 (and (memq byte-optimize-log '(t byte))
1297 (byte-compile-log " (goto %s) %s:\t-->\t%s %s:"
1298 (nth 1 lap1) (nth 1 lap1)
1300 (setq keep-going t))
1302 ;; varset-X varref-X --> dup varset-X
1303 ;; varbind-X varref-X --> dup varbind-X
1304 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1305 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1306 ;; The latter two can enable other optimizations.
1308 ((and (eq 'byte-varref (car lap2))
1309 (eq (cdr lap1) (cdr lap2))
1310 (memq (car lap1) '(byte-varset byte-varbind)))
1311 (if (and (setq tmp (memq (car (cdr lap2)) byte-boolean-vars))
1312 (not (eq (car lap0) 'byte-constant)))
1315 (if (memq (car lap0) '(byte-constant byte-dup))
1317 (setq tmp (if (or (not tmp)
1318 (memq (car (cdr lap0)) '(nil t)))
1320 (byte-compile-get-constant t)))
1321 (byte-compile-log-lap " %s %s %s\t-->\t%s %s %s"
1322 lap0 lap1 lap2 lap0 lap1
1323 (cons (car lap0) tmp))
1324 (setcar lap2 (car lap0))
1326 (byte-compile-log-lap " %s %s\t-->\tdup %s" lap1 lap2 lap1)
1327 (setcar lap2 (car lap1))
1328 (setcar lap1 'byte-dup)
1330 ;; The stack depth gets locally increased, so we will
1331 ;; increase maxdepth in case depth = maxdepth here.
1332 ;; This can cause the third argument to byte-code to
1333 ;; be larger than necessary.
1334 (setq add-depth 1))))
1336 ;; dup varset-X discard --> varset-X
1337 ;; dup varbind-X discard --> varbind-X
1338 ;; (the varbind variant can emerge from other optimizations)
1340 ((and (eq 'byte-dup (car lap0))
1341 (eq 'byte-discard (car lap2))
1342 (memq (car lap1) '(byte-varset byte-varbind)))
1343 (byte-compile-log-lap " dup %s discard\t-->\t%s" lap1 lap1)
1346 (setq lap (delq lap0 (delq lap2 lap))))
1348 ;; not goto-X-if-nil --> goto-X-if-non-nil
1349 ;; not goto-X-if-non-nil --> goto-X-if-nil
1351 ;; it is wrong to do the same thing for the -else-pop variants.
1353 ((and (eq 'byte-not (car lap0))
1354 (or (eq 'byte-goto-if-nil (car lap1))
1355 (eq 'byte-goto-if-not-nil (car lap1))))
1356 (byte-compile-log-lap " not %s\t-->\t%s"
1359 (if (eq (car lap1) 'byte-goto-if-nil)
1360 'byte-goto-if-not-nil
1363 (setcar lap1 (if (eq (car lap1) 'byte-goto-if-nil)
1364 'byte-goto-if-not-nil
1366 (setq lap (delq lap0 lap))
1367 (setq keep-going t))
1369 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1370 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1372 ;; it is wrong to do the same thing for the -else-pop variants.
1374 ((and (or (eq 'byte-goto-if-nil (car lap0))
1375 (eq 'byte-goto-if-not-nil (car lap0))) ; gotoX
1376 (eq 'byte-goto (car lap1)) ; gotoY
1377 (eq (cdr lap0) lap2)) ; TAG X
1378 (let ((inverse (if (eq 'byte-goto-if-nil (car lap0))
1379 'byte-goto-if-not-nil 'byte-goto-if-nil)))
1380 (byte-compile-log-lap " %s %s %s:\t-->\t%s %s:"
1382 (cons inverse (cdr lap1)) lap2)
1383 (setq lap (delq lap0 lap))
1384 (setcar lap1 inverse)
1385 (setq keep-going t)))
1387 ;; const goto-if-* --> whatever
1389 ((and (eq 'byte-constant (car lap0))
1390 (memq (car lap1) byte-conditional-ops))
1391 (cond ((if (or (eq (car lap1) 'byte-goto-if-nil)
1392 (eq (car lap1) 'byte-goto-if-nil-else-pop))
1394 (not (car (cdr lap0))))
1395 (byte-compile-log-lap " %s %s\t-->\t<deleted>"
1397 (setq rest (cdr rest)
1398 lap (delq lap0 (delq lap1 lap))))
1400 (if (memq (car lap1) byte-goto-always-pop-ops)
1402 (byte-compile-log-lap " %s %s\t-->\t%s"
1403 lap0 lap1 (cons 'byte-goto (cdr lap1)))
1404 (setq lap (delq lap0 lap)))
1405 (byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1
1406 (cons 'byte-goto (cdr lap1))))
1407 (setcar lap1 'byte-goto)))
1408 (setq keep-going t))
1410 ;; varref-X varref-X --> varref-X dup
1411 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1412 ;; We don't optimize the const-X variations on this here,
1413 ;; because that would inhibit some goto optimizations; we
1414 ;; optimize the const-X case after all other optimizations.
1416 ((and (eq 'byte-varref (car lap0))
1418 (setq tmp (cdr rest))
1419 (while (eq (car (car tmp)) 'byte-dup)
1420 (setq tmp (cdr tmp)))
1422 (eq (cdr lap0) (cdr (car tmp)))
1423 (eq 'byte-varref (car (car tmp))))
1424 (if (memq byte-optimize-log '(t byte))
1426 (setq tmp2 (cdr rest))
1427 (while (not (eq tmp tmp2))
1428 (setq tmp2 (cdr tmp2)
1429 str (concat str " dup")))
1430 (byte-compile-log-lap " %s%s %s\t-->\t%s%s dup"
1431 lap0 str lap0 lap0 str)))
1433 (setcar (car tmp) 'byte-dup)
1434 (setcdr (car tmp) 0)
1437 ;; TAG1: TAG2: --> TAG1: <deleted>
1438 ;; (and other references to TAG2 are replaced with TAG1)
1440 ((and (eq (car lap0) 'TAG)
1441 (eq (car lap1) 'TAG))
1442 (and (memq byte-optimize-log '(t byte))
1443 (byte-compile-log " adjacent tags %d and %d merged"
1444 (nth 1 lap1) (nth 1 lap0)))
1446 (while (setq tmp2 (rassq lap0 tmp3))
1448 (setq tmp3 (cdr (memq tmp2 tmp3))))
1449 (setq lap (delq lap0 lap)
1452 ;; unused-TAG: --> <deleted>
1454 ((and (eq 'TAG (car lap0))
1455 (not (rassq lap0 lap)))
1456 (and (memq byte-optimize-log '(t byte))
1457 (byte-compile-log " unused tag %d removed" (nth 1 lap0)))
1458 (setq lap (delq lap0 lap)
1461 ;; goto ... --> goto <delete until TAG or end>
1462 ;; return ... --> return <delete until TAG or end>
1464 ((and (memq (car lap0) '(byte-goto byte-return))
1465 (not (memq (car lap1) '(TAG nil))))
1468 (opt-p (memq byte-optimize-log '(t lap)))
1470 (while (and (setq tmp (cdr tmp))
1471 (not (eq 'TAG (car (car tmp)))))
1472 (if opt-p (setq deleted (cons (car tmp) deleted)
1473 str (concat str " %s")
1477 (if (eq 'TAG (car (car tmp)))
1478 (format "%d:" (cdr (car tmp)))
1479 (or (car tmp) ""))))
1481 (apply 'byte-compile-log-lap-1
1483 " %s\t-->\t%s <deleted> %s")
1485 (nconc (nreverse deleted)
1486 (list tagstr lap0 tagstr)))
1487 (byte-compile-log-lap
1488 " %s <%d unreachable op%s> %s\t-->\t%s <deleted> %s"
1489 lap0 i (if (= i 1) "" "s")
1490 tagstr lap0 tagstr))))
1492 (setq keep-going t))
1494 ;; <safe-op> unbind --> unbind <safe-op>
1495 ;; (this may enable other optimizations.)
1497 ((and (eq 'byte-unbind (car lap1))
1498 (memq (car lap0) byte-after-unbind-ops))
1499 (byte-compile-log-lap " %s %s\t-->\t%s %s" lap0 lap1 lap1 lap0)
1501 (setcar (cdr rest) lap0)
1502 (setq keep-going t))
1504 ;; varbind-X unbind-N --> discard unbind-(N-1)
1505 ;; save-excursion unbind-N --> unbind-(N-1)
1506 ;; save-restriction unbind-N --> unbind-(N-1)
1508 ((and (eq 'byte-unbind (car lap1))
1509 (memq (car lap0) '(byte-varbind byte-save-excursion
1510 byte-save-restriction))
1512 (if (zerop (setcdr lap1 (1- (cdr lap1))))
1514 (if (eq (car lap0) 'byte-varbind)
1515 (setcar rest (cons 'byte-discard 0))
1516 (setq lap (delq lap0 lap)))
1517 (byte-compile-log-lap " %s %s\t-->\t%s %s"
1518 lap0 (cons (car lap1) (1+ (cdr lap1)))
1519 (if (eq (car lap0) 'byte-varbind)
1522 (if (and (/= 0 (cdr lap1))
1523 (eq (car lap0) 'byte-varbind))
1526 (setq keep-going t))
1528 ;; goto*-X ... X: goto-Y --> goto*-Y
1529 ;; goto-X ... X: return --> return
1531 ((and (memq (car lap0) byte-goto-ops)
1532 (memq (car (setq tmp (nth 1 (memq (cdr lap0) lap))))
1533 '(byte-goto byte-return)))
1534 (cond ((and (not (eq tmp lap0))
1535 (or (eq (car lap0) 'byte-goto)
1536 (eq (car tmp) 'byte-goto)))
1537 (byte-compile-log-lap " %s [%s]\t-->\t%s"
1539 (if (eq (car tmp) 'byte-return)
1540 (setcar lap0 'byte-return))
1541 (setcdr lap0 (cdr tmp))
1542 (setq keep-going t))))
1544 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1545 ;; goto-*-else-pop X ... X: discard --> whatever
1547 ((and (memq (car lap0) '(byte-goto-if-nil-else-pop
1548 byte-goto-if-not-nil-else-pop))
1549 (memq (car (car (setq tmp (cdr (memq (cdr lap0) lap)))))
1551 (cons 'byte-discard byte-conditional-ops)))
1552 (not (eq lap0 (car tmp))))
1553 (setq tmp2 (car tmp))
1554 (setq tmp3 (assq (car lap0) '((byte-goto-if-nil-else-pop
1556 (byte-goto-if-not-nil-else-pop
1557 byte-goto-if-not-nil))))
1558 (if (memq (car tmp2) tmp3)
1559 (progn (setcar lap0 (car tmp2))
1560 (setcdr lap0 (cdr tmp2))
1561 (byte-compile-log-lap " %s-else-pop [%s]\t-->\t%s"
1562 (car lap0) tmp2 lap0))
1563 ;; Get rid of the -else-pop's and jump one step further.
1564 (or (eq 'TAG (car (nth 1 tmp)))
1565 (setcdr tmp (cons (byte-compile-make-tag)
1567 (byte-compile-log-lap " %s [%s]\t-->\t%s <skip>"
1568 (car lap0) tmp2 (nth 1 tmp3))
1569 (setcar lap0 (nth 1 tmp3))
1570 (setcdr lap0 (nth 1 tmp)))
1571 (setq keep-going t))
1573 ;; const goto-X ... X: goto-if-* --> whatever
1574 ;; const goto-X ... X: discard --> whatever
1576 ((and (eq (car lap0) 'byte-constant)
1577 (eq (car lap1) 'byte-goto)
1578 (memq (car (car (setq tmp (cdr (memq (cdr lap1) lap)))))
1580 (cons 'byte-discard byte-conditional-ops)))
1581 (not (eq lap1 (car tmp))))
1582 (setq tmp2 (car tmp))
1583 (cond ((memq (car tmp2)
1584 (if (null (car (cdr lap0)))
1585 '(byte-goto-if-nil byte-goto-if-nil-else-pop)
1586 '(byte-goto-if-not-nil
1587 byte-goto-if-not-nil-else-pop)))
1588 (byte-compile-log-lap " %s goto [%s]\t-->\t%s %s"
1589 lap0 tmp2 lap0 tmp2)
1590 (setcar lap1 (car tmp2))
1591 (setcdr lap1 (cdr tmp2))
1592 ;; Let next step fix the (const,goto-if*) sequence.
1593 (setq rest (cons nil rest)))
1595 ;; Jump one step further
1596 (byte-compile-log-lap
1597 " %s goto [%s]\t-->\t<deleted> goto <skip>"
1599 (or (eq 'TAG (car (nth 1 tmp)))
1600 (setcdr tmp (cons (byte-compile-make-tag)
1602 (setcdr lap1 (car (cdr tmp)))
1603 (setq lap (delq lap0 lap))))
1604 (setq keep-going t))
1606 ;; X: varref-Y ... varset-Y goto-X -->
1607 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1608 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1609 ;; (This is so usual for while loops that it is worth handling).
1611 ((and (eq (car lap1) 'byte-varset)
1612 (eq (car lap2) 'byte-goto)
1613 (not (memq (cdr lap2) rest)) ;Backwards jump
1614 (eq (car (car (setq tmp (cdr (memq (cdr lap2) lap)))))
1616 (eq (cdr (car tmp)) (cdr lap1))
1617 (not (memq (car (cdr lap1)) byte-boolean-vars)))
1618 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1619 (let ((newtag (byte-compile-make-tag)))
1620 (byte-compile-log-lap
1621 " %s: %s ... %s %s\t-->\t%s: %s %s: ... %s %s %s"
1622 (nth 1 (cdr lap2)) (car tmp)
1624 (nth 1 (cdr lap2)) (car tmp)
1625 (nth 1 newtag) 'byte-dup lap1
1626 (cons 'byte-goto newtag)
1628 (setcdr rest (cons (cons 'byte-dup 0) (cdr rest)))
1629 (setcdr tmp (cons (setcdr lap2 newtag) (cdr tmp))))
1631 (setq keep-going t))
1633 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1634 ;; (This can pull the loop test to the end of the loop)
1636 ((and (eq (car lap0) 'byte-goto)
1637 (eq (car lap1) 'TAG)
1639 (cdr (car (setq tmp (cdr (memq (cdr lap0) lap))))))
1640 (memq (car (car tmp))
1641 '(byte-goto byte-goto-if-nil byte-goto-if-not-nil
1642 byte-goto-if-nil-else-pop)))
1643 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1644 ;; lap0 lap1 (cdr lap0) (car tmp))
1645 (let ((newtag (byte-compile-make-tag)))
1646 (byte-compile-log-lap
1647 "%s %s: ... %s: %s\t-->\t%s ... %s:"
1648 lap0 (nth 1 lap1) (nth 1 (cdr lap0)) (car tmp)
1649 (cons (cdr (assq (car (car tmp))
1650 '((byte-goto-if-nil . byte-goto-if-not-nil)
1651 (byte-goto-if-not-nil . byte-goto-if-nil)
1652 (byte-goto-if-nil-else-pop .
1653 byte-goto-if-not-nil-else-pop)
1654 (byte-goto-if-not-nil-else-pop .
1655 byte-goto-if-nil-else-pop))))
1660 (setcdr tmp (cons (setcdr lap0 newtag) (cdr tmp)))
1661 (if (eq (car (car tmp)) 'byte-goto-if-nil-else-pop)
1662 ;; We can handle this case but not the -if-not-nil case,
1663 ;; because we won't know which non-nil constant to push.
1664 (setcdr rest (cons (cons 'byte-constant
1665 (byte-compile-get-constant nil))
1667 (setcar lap0 (nth 1 (memq (car (car tmp))
1668 '(byte-goto-if-nil-else-pop
1669 byte-goto-if-not-nil
1671 byte-goto-if-not-nil
1672 byte-goto byte-goto))))
1674 (setq keep-going t))
1676 (setq rest (cdr rest)))
1679 ;; Rebuild byte-compile-constants / byte-compile-variables.
1680 ;; Simple optimizations that would inhibit other optimizations if they
1681 ;; were done in the optimizing loop, and optimizations which there is no
1682 ;; need to do more than once.
1683 (setq byte-compile-constants nil
1684 byte-compile-variables nil)
1687 (setq lap0 (car rest)
1689 (if (memq (car lap0) byte-constref-ops)
1690 (if (eq (cdr lap0) 'byte-constant)
1691 (or (memq (cdr lap0) byte-compile-variables)
1692 (setq byte-compile-variables (cons (cdr lap0)
1693 byte-compile-variables)))
1694 (or (memq (cdr lap0) byte-compile-constants)
1695 (setq byte-compile-constants (cons (cdr lap0)
1696 byte-compile-constants)))))
1698 ;; const-C varset-X const-C --> const-C dup varset-X
1699 ;; const-C varbind-X const-C --> const-C dup varbind-X
1701 (and (eq (car lap0) 'byte-constant)
1702 (eq (car (nth 2 rest)) 'byte-constant)
1703 (eq (cdr lap0) (car (nth 2 rest)))
1704 (memq (car lap1) '(byte-varbind byte-varset)))
1705 (byte-compile-log-lap " %s %s %s\t-->\t%s dup %s"
1706 lap0 lap1 lap0 lap0 lap1)
1707 (setcar (cdr (cdr rest)) (cons (car lap1) (cdr lap1)))
1708 (setcar (cdr rest) (cons 'byte-dup 0))
1711 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1712 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1714 ((memq (car lap0) '(byte-constant byte-varref))
1718 (while (eq 'byte-dup (car (car (setq tmp (cdr tmp))))))
1719 (and (eq (cdr lap0) (cdr (car tmp)))
1720 (eq (car lap0) (car (car tmp)))))
1721 (setcar tmp (cons 'byte-dup 0))
1724 (byte-compile-log-lap
1725 " %s [dup/%s]... %s\t-->\t%s dup..." lap0 lap0 lap0)))
1727 ;; unbind-N unbind-M --> unbind-(N+M)
1729 ((and (eq 'byte-unbind (car lap0))
1730 (eq 'byte-unbind (car lap1)))
1731 (byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1
1733 (+ (cdr lap0) (cdr lap1))))
1735 (setq lap (delq lap0 lap))
1736 (setcdr lap1 (+ (cdr lap1) (cdr lap0))))
1738 (setq rest (cdr rest)))
1739 (setq byte-compile-maxdepth (+ byte-compile-maxdepth add-depth)))
1742 (provide 'byte-optimize)
1745 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
1746 ;; itself, compile some of its most used recursive functions (at load time).
1749 (or (byte-code-function-p (symbol-function 'byte-optimize-form))
1750 (assq 'byte-code (symbol-function 'byte-optimize-form))
1751 (let ((byte-optimize nil)
1752 (byte-compile-warnings nil))
1753 (mapcar '(lambda (x)
1754 (or noninteractive (message "compiling %s..." x))
1756 (or noninteractive (message "compiling %s...done" x)))
1757 '(byte-optimize-form
1759 byte-optimize-predicate
1760 byte-optimize-binary-predicate
1761 ;; Inserted some more than necessary, to speed it up.
1762 byte-optimize-form-code-walker
1763 byte-optimize-lapcode))))
1766 ;;; byte-opt.el ends here