| blob | da8e7583438b47a5d155e091f3d4c5d767191dcb |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler
3 ;; Copyright (c) 1991,1994,2000,01,02,2004 Free Software Foundation, Inc.
5 ;; Author: Jamie Zawinski <jwz@lucid.com>
6 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
7 ;; Maintainer: FSF
8 ;; Keywords: internal
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software; you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation; either version 2, or (at your option)
15 ;; any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs; see the file COPYING. If not, write to the
24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
25 ;; Boston, MA 02111-1307, USA.
27 ;;; Commentary:
29 ;; ========================================================================
30 ;; "No matter how hard you try, you can't make a racehorse out of a pig.
31 ;; You can, however, make a faster pig."
32 ;;
33 ;; Or, to put it another way, the emacs byte compiler is a VW Bug. This code
34 ;; makes it be a VW Bug with fuel injection and a turbocharger... You're
35 ;; still not going to make it go faster than 70 mph, but it might be easier
36 ;; to get it there.
37 ;;
39 ;; TO DO:
40 ;;
41 ;; (apply (lambda (x &rest y) ...) 1 (foo))
42 ;;
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 'debug-on-next-call 'binding-is-magic t)
53 ;; (put 'inhibit-quit 'binding-is-magic t)
54 ;; (put 'quit-flag 'binding-is-magic t)
55 ;; (put 't 'binding-is-magic t)
56 ;; (put 'nil 'binding-is-magic t)
57 ;; possibly also
58 ;; (put 'gc-cons-threshold 'binding-is-magic t)
59 ;; (put 'track-mouse 'binding-is-magic t)
60 ;; others?
61 ;;
62 ;; Simple defsubsts often produce forms like
63 ;; (let ((v1 (f1)) (v2 (f2)) ...)
64 ;; (FN v1 v2 ...))
65 ;; It would be nice if we could optimize this to
66 ;; (FN (f1) (f2) ...)
67 ;; but we can't unless FN is dynamically-safe (it might be dynamically
68 ;; referring to the bindings that the lambda arglist established.)
69 ;; One of the uncountable lossages introduced by dynamic scope...
70 ;;
71 ;; Maybe there should be a control-structure that says "turn on
72 ;; fast-and-loose type-assumptive optimizations here." Then when
73 ;; we see a form like (car foo) we can from then on assume that
74 ;; the variable foo is of type cons, and optimize based on that.
75 ;; But, this won't win much because of (you guessed it) dynamic
76 ;; scope. Anything down the stack could change the value.
77 ;; (Another reason it doesn't work is that it is perfectly valid
78 ;; to call car with a null argument.) A better approach might
79 ;; be to allow type-specification of the form
80 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
81 ;; (put 'foo 'result-type 'bool)
82 ;; It should be possible to have these types checked to a certain
83 ;; degree.
84 ;;
85 ;; collapse common subexpressions
86 ;;
87 ;; It would be nice if redundant sequences could be factored out as well,
88 ;; when they are known to have no side-effects:
89 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
90 ;; but beware of traps like
91 ;; (cons (list x y) (list x y))
92 ;;
93 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
94 ;; Tail-recursion elimination is almost always impossible when all variables
95 ;; have dynamic scope, but given that the "return" byteop requires the
96 ;; binding stack to be empty (rather than emptying it itself), there can be
97 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
98 ;; make any bindings.
99 ;;
100 ;; Here is an example of an Emacs Lisp function which could safely be
101 ;; byte-compiled tail-recursively:
102 ;;
103 ;; (defun tail-map (fn list)
104 ;; (cond (list
105 ;; (funcall fn (car list))
106 ;; (tail-map fn (cdr list)))))
107 ;;
108 ;; However, if there was even a single let-binding around the COND,
109 ;; it could not be byte-compiled, because there would be an "unbind"
110 ;; byte-op between the final "call" and "return." Adding a
111 ;; Bunbind_all byteop would fix this.
112 ;;
113 ;; (defun foo (x y z) ... (foo a b c))
114 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
115 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
116 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
117 ;;
118 ;; this also can be considered tail recursion:
119 ;;
120 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
121 ;; could generalize this by doing the optimization
122 ;; (goto X) ... X: (return) --> (return)
123 ;;
124 ;; But this doesn't solve all of the problems: although by doing tail-
125 ;; recursion elimination in this way, the call-stack does not grow, the
126 ;; binding-stack would grow with each recursive step, and would eventually
127 ;; overflow. I don't believe there is any way around this without lexical
128 ;; scope.
129 ;;
130 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
131 ;;
132 ;; Idea: the form (lexical-scope) in a file means that the file may be
133 ;; compiled lexically. This proclamation is file-local. Then, within
134 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
135 ;; would do things the old way. (Or we could use CL "declare" forms.)
136 ;; We'd have to notice defvars and defconsts, since those variables should
137 ;; always be dynamic, and attempting to do a lexical binding of them
138 ;; should simply do a dynamic binding instead.
139 ;; But! We need to know about variables that were not necessarily defvarred
140 ;; in the file being compiled (doing a boundp check isn't good enough.)
141 ;; Fdefvar() would have to be modified to add something to the plist.
142 ;;
143 ;; A major disadvantage of this scheme is that the interpreter and compiler
144 ;; would have different semantics for files compiled with (dynamic-scope).
145 ;; Since this would be a file-local optimization, there would be no way to
146 ;; modify the interpreter to obey this (unless the loader was hacked
147 ;; in some grody way, but that's a really bad idea.)
149 ;; Other things to consider:
151 ;; ;; Associative math should recognize subcalls to identical function:
152 ;; (disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
153 ;; ;; This should generate the same as (1+ x) and (1- x)
155 ;; (disassemble (lambda (x) (cons (+ x 1) (- x 1))))
156 ;; ;; An awful lot of functions always return a non-nil value. If they're
157 ;; ;; error free also they may act as true-constants.
159 ;; (disassemble (lambda (x) (and (point) (foo))))
160 ;; ;; When
161 ;; ;; - all but one arguments to a function are constant
162 ;; ;; - the non-constant argument is an if-expression (cond-expression?)
163 ;; ;; then the outer function can be distributed. If the guarding
164 ;; ;; condition is side-effect-free [assignment-free] then the other
165 ;; ;; arguments may be any expressions. Since, however, the code size
166 ;; ;; can increase this way they should be "simple". Compare:
168 ;; (disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
169 ;; (disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
171 ;; ;; (car (cons A B)) -> (prog1 A B)
172 ;; (disassemble (lambda (x) (car (cons (foo) 42))))
174 ;; ;; (cdr (cons A B)) -> (progn A B)
175 ;; (disassemble (lambda (x) (cdr (cons 42 (foo)))))
177 ;; ;; (car (list A B ...)) -> (prog1 A B ...)
178 ;; (disassemble (lambda (x) (car (list (foo) 42 (bar)))))
180 ;; ;; (cdr (list A B ...)) -> (progn A (list B ...))
181 ;; (disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
184 ;;; Code:
199 arg)
215 c
217 args)))))
223 \f
224 ;;; byte-compile optimizers to support inlining
229 "byte-optimize-handler for the `inline' special-form."
242 sexp)))
246 ;; Splice the given lap code into the current instruction stream.
247 ;; If it has any labels in it, you're responsible for making sure there
248 ;; are no collisions, and that byte-compile-tag-number is reasonable
249 ;; after this is spliced in. The provided list is destroyed.
260 name)
261 form)
262 ;; else
275 ;; Isn't it an error for `string' not to be unibyte?? --stef
283 ;; Give up on inlining.
284 form))))))
286 ;; ((lambda ...) ...)
297 optionalp restp
298 bindings)
305 ;; ok, I'll let this slide because funcall_lambda() does...
306 ;; (if optionalp (error "multiple &optional keywords in %s" name))
312 ;; ...but it is by no stretch of the imagination a reasonable
313 ;; thing that funcall_lambda() allows (&rest x y) and
314 ;; (&rest x &optional y) in arglists.
323 bindings)
324 values nil))
330 bindings)
338 form)
340 ;; The following leads to infinite recursion when loading a
341 ;; file containing `(defsubst f () (f))', and then trying to
342 ;; byte-compile that file.
343 ;(setq body (mapcar 'byte-optimize-form body)))
350 newform)))))
352 \f
353 ;;; implementing source-level optimizers
356 ;;
357 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
358 ;; we need to have special knowledge of the syntax of the special forms
359 ;; like let and defun (that's why they're special forms :-). (Actually,
360 ;; the important aspect is that they are subrs that don't evaluate all of
361 ;; their args.)
362 ;;
364 tmp)
370 form))
375 ;; map (quote nil) to nil to simplify optimizer logic.
376 ;; map quoted constants to nil if for-effect (just because).
379 form))
384 ;; recursively enter the optimizer for the bindings and body
385 ;; of a let or let*. This for depth-firstness: forms that
386 ;; are more deeply nested are optimized first.
391 binding
408 clause))
411 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
430 ;; those subrs which have an implicit progn; it's not quite good
431 ;; enough to treat these like normal function calls.
432 ;; This can turn (save-excursion ...) into (save-excursion) which
433 ;; will be optimized away in the lap-optimize pass.
437 ;; this is just like the above, except for the first argument.
453 ;; take forms off the back until we can't any more.
454 ;; In the future it could conceivably be a problem that the
455 ;; subexpressions of these forms are optimized in the reverse
456 ;; order, but it's ok for now.
462 for-effect))))
474 nil)
477 condition-case save-window-excursion))
478 ;; These forms are compiled as constants or by breaking out
479 ;; all the subexpressions and compiling them separately.
480 form)
483 ;; the "protected" part of an unwind-protect is compiled (and thus
484 ;; optimized) as a top-level form, so don't do it here. But the
485 ;; non-protected part has the same for-effect status as the
486 ;; unwind-protect itself. (The protected part is always for effect,
487 ;; but that isn't handled properly yet.)
493 ;; the body of a catch is compiled (and thus optimized) as a
494 ;; top-level form, so don't do it here. The tag is never
495 ;; for-effect. The body should have the same for-effect status
496 ;; as the catch form itself, but that isn't handled properly yet.
502 ;; Don't treat the args to `ignore' as being
503 ;; computed for effect. We want to avoid the warnings
504 ;; that might occur if they were treated that way.
505 ;; However, don't actually bother calling `ignore'.
508 ;; If optimization is on, this is the only place that macros are
509 ;; expanded. If optimization is off, then macroexpansion happens
510 ;; in byte-compile-form. Otherwise, the macros are already expanded
511 ;; by the time that is reached.
514 byte-compile-macro-environment))))
517 ;; Support compiler macros as in cl.el.
528 form)
533 ;; Detect the expansion of (pop foo).
534 ;; There is no need to compile the call to `car' there.
548 nil)))
550 ;; appending a nil here might not be necessary, but it can't hurt.
555 ;; Otherwise, no args can be considered to be for-effect,
556 ;; even if the called function is for-effect, because we
557 ;; don't know anything about that function.
562 "The source-level pass of the optimizer."
563 ;;
564 ;; First, optimize all sub-forms of this one.
566 ;;
567 ;; after optimizing all subforms, optimize this form until it doesn't
568 ;; optimize any further. This means that some forms will be passed through
569 ;; the optimizer many times, but that's necessary to make the for-effect
570 ;; processing do as much as possible.
571 ;;
576 ;; we don't have any of these yet, but we might.
581 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
584 new)
585 form)))
589 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
590 ;; forms, all but the last of which are optimized with the assumption that
591 ;; they are being called for effect. the last is for-effect as well if
592 ;; all-for-effect is true. returns a new list of forms.
595 fe new)
604 \f
605 ;; some source-level optimizers
606 ;;
607 ;; when writing optimizers, be VERY careful that the optimizer returns
608 ;; something not EQ to its argument if and ONLY if it has made a change.
609 ;; This implies that you cannot simply destructively modify the list;
610 ;; you must return something not EQ to it if you make an optimization.
611 ;;
612 ;; It is now safe to optimize code such that it introduces new bindings.
614 ;; I'd like this to be a defsubst, but let's not be self-referential...
616 ;; Returns non-nil if FORM is a non-nil constant.
622 ;; If the function is being called with constant numeric args,
623 ;; evaluate as much as possible at compile-time. This optimizer
624 ;; assumes that the function is associative, like + or *.
642 form)))
644 ;; If the function is being called with constant numeric args,
645 ;; evaluate as much as possible at compile-time. This optimizer
646 ;; assumes that the function satisfies
647 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
648 ;; like - and /.
652 form
660 constant))))
662 ;;(defun byte-optimize-associative-two-args-math (form)
663 ;; (setq form (byte-optimize-associative-math form))
664 ;; (if (consp form)
665 ;; (byte-optimize-two-args-left form)
666 ;; form))
668 ;;(defun byte-optimize-nonassociative-two-args-math (form)
669 ;; (setq form (byte-optimize-nonassociative-math form))
670 ;; (if (consp form)
671 ;; (byte-optimize-two-args-right form)
672 ;; form))
677 ;; Collect all the constants from FORM, after the STARTth arg,
678 ;; and apply FUN to them to make one argument at the end.
679 ;; For functions that can handle floats, that optimization
680 ;; can be incorrect because reordering can cause an overflow
681 ;; that would otherwise be avoided by encountering an arg that is a float.
682 ;; We avoid this problem by (1) not moving float constants and
683 ;; (2) not moving anything if it would cause an overflow.
685 ;; Merge all FORM's constants from number START, call FUN on them
686 ;; and put the result at the end.
689 ;; t means we must check for overflow.
700 ;; If necessary, check now for overflow
701 ;; that might be caused by reordering.
703 ;; We have overflow if the result of doing the arithmetic
704 ;; on floats is not even close to the result
705 ;; of doing it on integers.
712 form))
717 ;;(setq form (byte-optimize-associative-two-args-math form))
722 ;;; It is not safe to delete the function entirely
723 ;;; (actually, it would be safe if we know the sole arg
724 ;;; is not a marker).
725 ;;; ((null (cdr (cdr form))) (nth 1 form))
729 form))
733 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
743 other)))
747 ;; Put constants at the end, except the last constant.
749 ;; Now only first and last element can be a number.
752 ;; (- x y ... 0) --> (- x y ...)
759 ;; If form is (- CONST foo... CONST), merge first and last.
764 ;;; It is not safe to delete the function entirely
765 ;;; (actually, it would be safe if we know the sole arg
766 ;;; is not a marker).
767 ;;; (if (eq (nth 2 form) 0)
768 ;;; (nth 1 form) ; (- x 0) --> x
773 form))
774 ;;; )
775 )
779 ;; If there is a constant in FORM, it is now the last element.
781 ;;; It is not safe to delete the function entirely
782 ;;; (actually, it would be safe if we know the sole arg
783 ;;; is not a marker or if it appears in other arithmetic).
784 ;;; ((null (cdr (cdr form))) (nth 1 form))
816 last nil))))
818 ;;; ((null (cdr (cdr form)))
819 ;;; (nth 1 form))
847 ;; This can enable some lapcode optimizations.
849 form))
861 form)))
869 form))
913 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
914 ;; take care of this? - Jamie
915 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
916 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
922 form
935 ;; Simplify if less than 2 args.
936 ;; if there is a literal nil in the args to `and', throw it and following
937 ;; forms away, and surround the `and' with (progn ... nil).
946 nil))
952 ;; Throw away nil's, and simplify if less than 2 args.
953 ;; If there is a literal non-nil constant in the args to `or', throw away all
954 ;; following forms.
967 ;; if any clauses have a literal nil as their test, throw them away.
968 ;; if any clause has a literal non-nil constant as its test, throw
969 ;; away all following clauses.
971 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
990 ;;
991 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
999 form))
1000 form))
1003 ;; (if <true-constant> <then> <else...>) ==> <then>
1004 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1005 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1006 ;; (if <test> <then> nil) ==> (if <test> <then>)
1017 form))
1020 ;; Don't make a double negative;
1021 ;; instead, take away the one that is there.
1036 form))
1044 ;; byte-compile-negation-optimizer lives in bytecomp.el
1051 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1052 ;; (funcall foo ...) ==> (foo ...)
1056 form)))
1059 ;; If the last arg is a literal constant, turn this into a funcall.
1060 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1070 "last arg to apply can't be a literal atom: `%s'"
1072 nil))
1073 form)))
1083 ;; No bindings
1086 form)
1087 ;; The body is nil
1104 form))
1114 form)
1116 form))
1123 "Do constant folding for pure functions.
1124 This assumes that the function will not have any side-effects and that
1125 its return value depends solely on its arguments.
1126 If the function can signal an error, this might change the semantics
1127 of FORM by signalling the error at compile-time."
1136 form)))
1138 ;; Avoid having to write forward-... with a negative arg for speed.
1139 ;; Fixme: don't be limited to constant args.
1166 ;; Fixme: delete-char -> delete-region (byte-coded)
1167 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1168 ;; string-make-multibyte for constant args.
1172 ;; Emacs-21's byte-code doesn't run under XEmacs anyway, so we can
1173 ;; safely optimize away this test.
1175 nil
1176 form))
1189 \f
1190 ;; enumerating those functions which need not be called if the returned
1191 ;; value is not used. That is, something like
1192 ;; (progn (list (something-with-side-effects) (yow))
1193 ;; (foo))
1194 ;; may safely be turned into
1195 ;; (progn (progn (something-with-side-effects) (yow))
1196 ;; (foo))
1197 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1199 ;; Some of these functions have the side effect of allocating memory
1200 ;; and it would be incorrect to replace two calls with one.
1201 ;; But we don't try to do those kinds of optimizations,
1202 ;; so it is safe to list such functions here.
1203 ;; Some of these functions return values that depend on environment
1204 ;; state, so that constant folding them would be wrong,
1205 ;; but we don't do constant folding based on this list.
1207 ;; However, at present the only optimization we normally do
1208 ;; is delete calls that need not occur, and we only do that
1209 ;; with the error-free functions.
1211 ;; I wonder if I missed any :-\)
1214 assoc assq
1215 boundp buffer-file-name buffer-local-variables buffer-modified-p
1216 buffer-substring byte-code-function-p
1217 capitalize car-less-than-car car cdr ceiling char-after char-before
1218 char-equal char-to-string char-width
1219 compare-strings concat coordinates-in-window-p
1220 copy-alist copy-sequence copy-marker cos count-lines
1221 decode-time default-boundp default-value documentation downcase
1222 elt exp expt encode-time error-message-string
1223 fboundp fceiling featurep ffloor
1224 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1225 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1226 float float-time floor format format-time-string frame-visible-p
1227 fround ftruncate
1228 get gethash get-buffer get-buffer-window getenv get-file-buffer
1229 hash-table-count
1230 int-to-string intern-soft
1231 keymap-parent
1232 length local-variable-if-set-p local-variable-p log log10 logand
1233 logb logior lognot logxor lsh
1234 make-list make-string make-symbol
1235 marker-buffer max member memq min mod multibyte-char-to-unibyte
1236 next-window nth nthcdr number-to-string
1237 parse-colon-path plist-get plist-member
1238 prefix-numeric-value previous-window prin1-to-string propertize
1239 radians-to-degrees rassq rassoc read-from-string regexp-quote
1240 region-beginning region-end reverse round
1242 string-to-int string-to-number substring sxhash symbol-function
1243 symbol-name symbol-plist symbol-value string-make-unibyte
1244 string-make-multibyte string-as-multibyte string-as-unibyte
1245 tan truncate
1246 unibyte-char-to-multibyte upcase user-full-name
1247 user-login-name user-original-login-name user-variable-p
1248 vconcat
1249 window-buffer window-dedicated-p window-edges window-height
1250 window-hscroll window-minibuffer-p window-width
1251 zerop))
1254 bobp bolp bool-vector-p
1255 buffer-end buffer-list buffer-size buffer-string bufferp
1256 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1257 current-buffer current-global-map current-indentation
1258 current-local-map current-minor-mode-maps current-time
1259 current-time-string current-time-zone
1260 eobp eolp eq equal eventp
1261 floatp following-char framep
1262 get-largest-window get-lru-window
1263 hash-table-p
1264 identity ignore integerp integer-or-marker-p interactive-p
1265 invocation-directory invocation-name
1266 keymapp
1267 line-beginning-position line-end-position list listp
1268 make-marker mark mark-marker markerp memory-limit minibuffer-window
1269 mouse-movement-p
1270 natnump nlistp not null number-or-marker-p numberp
1271 one-window-p overlayp
1272 point point-marker point-min point-max preceding-char processp
1273 recent-keys recursion-depth
1274 safe-length selected-frame selected-window sequencep
1275 standard-case-table standard-syntax-table stringp subrp symbolp
1276 syntax-table syntax-table-p
1277 this-command-keys this-command-keys-vector this-single-command-keys
1278 this-single-command-raw-keys
1279 user-real-login-name user-real-uid user-uid
1280 vector vectorp visible-frame-list
1281 wholenump window-configuration-p window-live-p windowp)))
1288 nil)
1292 ;; form is (byte-code "..." [...] n)
1298 byte-compile-maxdepth))
1303 \f
1307 ;; This function extracts the bitfields from variable-length opcodes.
1308 ;; Originally defined in disass.el (which no longer uses it.)
1311 "Don't call this!"
1312 ;; fetch and return the offset for the current opcode.
1313 ;; return nil if this opcode has no offset
1314 ;; OP, PTR and BYTES are used and set dynamically
1345 ;; This de-compiler is used for inline expansion of compiled functions,
1346 ;; and by the disassembler.
1347 ;;
1348 ;; This list contains numbers, which are pc values,
1349 ;; before each instruction.
1351 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1357 ;; As byte-decompile-bytecode, but updates
1358 ;; byte-compile-{constants, variables, tag-number}.
1359 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1360 ;; with `goto's destined for the end of the code.
1361 ;; That is for use by the compiler.
1362 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1363 ;; In that case, we put a pc value into the list
1364 ;; before each insn (or its label).
1368 lap tmp
1369 endtag
1375 optr ptr
1379 ;; it's a pc
1385 tags)))))))
1396 byte-compile-variables)))))))
1403 ;; lap = ( [ (pc . (op . arg)) ]* )
1405 lap))
1407 ;; take off the dummy nil op that we replaced a trailing "return" with.
1412 ;; this addr is jumped to
1423 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1426 elt
1430 \f
1431 ;;; peephole optimizer
1437 byte-goto-if-not-nil-else-pop))
1441 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1442 byte-eq byte-not
1443 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1444 byte-interactive-p)
1445 ;; How about other side-effect-free-ops? Is it safe to move an
1446 ;; error invocation (such as from nth) out of an unwind-protect?
1447 ;; No, it is not, because the unwind-protect forms can alter
1448 ;; the inside of the object to which nth would apply.
1449 ;; For the same reason, byte-equal was deleted from this list.
1454 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1455 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1456 byte-point-min byte-following-char byte-preceding-char
1457 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1458 byte-current-buffer byte-interactive-p))
1463 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1464 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1465 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1467 byte-member byte-assq byte-quo byte-rem)
1468 byte-compile-side-effect-and-error-free-ops))
1470 ;; This crock is because of the way DEFVAR_BOOL variables work.
1471 ;; Consider the code
1472 ;;
1473 ;; (defun foo (flag)
1474 ;; (let ((old-pop-ups pop-up-windows)
1475 ;; (pop-up-windows flag))
1476 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1477 ;; (setq old-pop-ups pop-up-windows)
1478 ;; ...))))
1479 ;;
1480 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1481 ;; something else. But if we optimize
1482 ;;
1483 ;; varref flag
1484 ;; varbind pop-up-windows
1485 ;; varref pop-up-windows
1486 ;; not
1487 ;; to
1488 ;; varref flag
1489 ;; dup
1490 ;; varbind pop-up-windows
1491 ;; not
1492 ;;
1493 ;; we break the program, because it will appear that pop-up-windows and
1494 ;; old-pop-ups are not EQ when really they are. So we have to know what
1495 ;; the BOOL variables are, and not perform this optimization on them.
1497 ;; The variable `byte-boolean-vars' is now primitive and updated
1498 ;; automatically by DEFVAR_BOOL.
1501 "Simple peephole optimizer. LAP is both modified and returned.
1502 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1504 lap1
1505 lap2
1508 rest tmp tmp2 tmp3
1510 byte-compile-side-effect-free-ops
1511 byte-compile-side-effect-and-error-free-ops)))
1516 keep-going nil)
1522 ;; You may notice that sequences like "dup varset discard" are
1523 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1524 ;; You may be tempted to change this; resist that temptation.
1526 ;; <side-effect-free> pop --> <deleted>
1527 ;; ...including:
1528 ;; const-X pop --> <deleted>
1529 ;; varref-X pop --> <deleted>
1530 ;; dup pop --> <deleted>
1531 ;;
1551 ;;
1552 ;; goto*-X X: --> X:
1553 ;;
1568 ;;
1569 ;; varset-X varref-X --> dup varset-X
1570 ;; varbind-X varref-X --> dup varbind-X
1571 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1572 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1573 ;; The latter two can enable other optimizations.
1574 ;;
1580 nil
1590 lap0 lap1 lap2 lap0 lap1
1598 ;; The stack depth gets locally increased, so we will
1599 ;; increase maxdepth in case depth = maxdepth here.
1600 ;; This can cause the third argument to byte-code to
1601 ;; be larger than necessary.
1603 ;;
1604 ;; dup varset-X discard --> varset-X
1605 ;; dup varbind-X discard --> varbind-X
1606 ;; (the varbind variant can emerge from other optimizations)
1607 ;;
1615 ;;
1616 ;; not goto-X-if-nil --> goto-X-if-non-nil
1617 ;; not goto-X-if-non-nil --> goto-X-if-nil
1618 ;;
1619 ;; it is wrong to do the same thing for the -else-pop variants.
1620 ;;
1625 lap1
1628 'byte-goto-if-not-nil
1632 'byte-goto-if-not-nil
1636 ;;
1637 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1638 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1639 ;;
1640 ;; it is wrong to do the same thing for the -else-pop variants.
1641 ;;
1649 lap0 lap1 lap2
1654 ;;
1655 ;; const goto-if-* --> whatever
1656 ;;
1664 lap0 lap1)
1677 ;;
1678 ;; varref-X varref-X --> varref-X dup
1679 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1680 ;; We don't optimize the const-X variations on this here,
1681 ;; because that would inhibit some goto optimizations; we
1682 ;; optimize the const-X case after all other optimizations.
1683 ;;
1689 t)
1699 lap0 str lap0 lap0 str)))
1704 ;;
1705 ;; TAG1: TAG2: --> TAG1: <deleted>
1706 ;; (and other references to TAG2 are replaced with TAG1)
1707 ;;
1718 keep-going t))
1719 ;;
1720 ;; unused-TAG: --> <deleted>
1721 ;;
1727 keep-going t))
1728 ;;
1729 ;; goto ... --> goto <delete until TAG or end>
1730 ;; return ... --> return <delete until TAG or end>
1731 ;;
1737 str deleted)
1752 lap0
1758 tagstr lap0 tagstr))))
1761 ;;
1762 ;; <safe-op> unbind --> unbind <safe-op>
1763 ;; (this may enable other optimizations.)
1764 ;;
1771 ;;
1772 ;; varbind-X unbind-N --> discard unbind-(N-1)
1773 ;; save-excursion unbind-N --> unbind-(N-1)
1774 ;; save-restriction unbind-N --> unbind-(N-1)
1775 ;;
1778 byte-save-restriction))
1795 ;;
1796 ;; goto*-X ... X: goto-Y --> goto*-Y
1797 ;; goto-X ... X: return --> return
1798 ;;
1811 ;;
1812 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1813 ;; goto-*-else-pop X ... X: discard --> whatever
1814 ;;
1816 byte-goto-if-not-nil-else-pop))
1823 byte-goto-if-nil)
1825 byte-goto-if-not-nil))))
1831 ;; Get rid of the -else-pop's and jump one step further.
1840 ;;
1841 ;; const goto-X ... X: goto-if-* --> whatever
1842 ;; const goto-X ... X: discard --> whatever
1843 ;;
1855 byte-goto-if-not-nil-else-pop)))
1857 lap0 tmp2 lap0 tmp2)
1860 ;; Let next step fix the (const,goto-if*) sequence.
1863 ;; Jump one step further
1866 lap0 tmp2)
1873 ;;
1874 ;; X: varref-Y ... varset-Y goto-X -->
1875 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1876 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1877 ;; (This is so usual for while loops that it is worth handling).
1878 ;;
1886 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1891 lap1 lap2
1895 )
1900 ;;
1901 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1902 ;; (This can pull the loop test to the end of the loop)
1903 ;;
1910 byte-goto-if-nil-else-pop)))
1911 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1912 ;; lap0 lap1 (cdr lap0) (car tmp))
1921 byte-goto-if-not-nil-else-pop)
1923 byte-goto-if-nil-else-pop))))
1924 newtag)
1927 )
1930 ;; We can handle this case but not the -if-not-nil case,
1931 ;; because we won't know which non-nil constant to push.
1937 byte-goto-if-not-nil
1938 byte-goto-if-nil
1939 byte-goto-if-not-nil
1940 byte-goto byte-goto))))
1941 )
1943 )
1945 )
1946 ;; Cleanup stage:
1947 ;; Rebuild byte-compile-constants / byte-compile-variables.
1948 ;; Simple optimizations that would inhibit other optimizations if they
1949 ;; were done in the optimizing loop, and optimizations which there is no
1950 ;; need to do more than once.
1952 byte-compile-variables nil)
1962 byte-compile-constants)))
1965 byte-compile-variables)))))
1967 ;; const-C varset-X const-C --> const-C dup varset-X
1968 ;; const-C varbind-X const-C --> const-C dup varbind-X
1969 ;;
1975 lap0 lap1 lap0 lap0 lap1)
1979 ;;
1980 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1981 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1982 ;;
1985 tmp2 nil)
1995 ;;
1996 ;; unbind-N unbind-M --> unbind-(N+M)
1997 ;;
2006 )
2009 lap)
2013 \f
2014 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2015 ;; itself, compile some of its most used recursive functions (at load time).
2016 ;;
2027 byte-optimize-body
2028 byte-optimize-predicate
2029 byte-optimize-binary-predicate
2030 ;; Inserted some more than necessary, to speed it up.
2031 byte-optimize-form-code-walker
2032 byte-optimize-lapcode))))
2033 nil)
2035 ;;; arch-tag: 0f14076b-737e-4bef-aae6-908826ec1ff1
2036 ;;; byte-opt.el ends here