| blob | acb882dd9a34ba43b40fc2bed8030e052698ef10 |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler
3 ;; Copyright (c) 1991, 1994, 2000, 2001, 2002, 2004
4 ;; Free Software Foundation, Inc.
6 ;; Author: Jamie Zawinski <jwz@lucid.com>
7 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
8 ;; Maintainer: FSF
9 ;; Keywords: internal
11 ;; This file is part of GNU Emacs.
13 ;; GNU Emacs is free software; you can redistribute it and/or modify
14 ;; it under the terms of the GNU General Public License as published by
15 ;; the Free Software Foundation; either version 2, or (at your option)
16 ;; any later version.
18 ;; GNU Emacs is distributed in the hope that it will be useful,
19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ;; GNU General Public License for more details.
23 ;; You should have received a copy of the GNU General Public License
24 ;; along with GNU Emacs; see the file COPYING. If not, write to the
25 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
26 ;; Boston, MA 02111-1307, USA.
28 ;;; Commentary:
30 ;; ========================================================================
31 ;; "No matter how hard you try, you can't make a racehorse out of a pig.
32 ;; You can, however, make a faster pig."
33 ;;
34 ;; Or, to put it another way, the emacs byte compiler is a VW Bug. This code
35 ;; makes it be a VW Bug with fuel injection and a turbocharger... You're
36 ;; still not going to make it go faster than 70 mph, but it might be easier
37 ;; to get it there.
38 ;;
40 ;; TO DO:
41 ;;
42 ;; (apply (lambda (x &rest y) ...) 1 (foo))
43 ;;
44 ;; maintain a list of functions known not to access any global variables
45 ;; (actually, give them a 'dynamically-safe property) and then
46 ;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
47 ;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
48 ;; by recursing on this, we might be able to eliminate the entire let.
49 ;; However certain variables should never have their bindings optimized
50 ;; away, because they affect everything.
51 ;; (put 'debug-on-error 'binding-is-magic t)
52 ;; (put 'debug-on-abort 'binding-is-magic t)
53 ;; (put 'debug-on-next-call 'binding-is-magic t)
54 ;; (put 'inhibit-quit 'binding-is-magic t)
55 ;; (put 'quit-flag 'binding-is-magic t)
56 ;; (put 't 'binding-is-magic t)
57 ;; (put 'nil 'binding-is-magic t)
58 ;; possibly also
59 ;; (put 'gc-cons-threshold 'binding-is-magic t)
60 ;; (put 'track-mouse 'binding-is-magic t)
61 ;; others?
62 ;;
63 ;; Simple defsubsts often produce forms like
64 ;; (let ((v1 (f1)) (v2 (f2)) ...)
65 ;; (FN v1 v2 ...))
66 ;; It would be nice if we could optimize this to
67 ;; (FN (f1) (f2) ...)
68 ;; but we can't unless FN is dynamically-safe (it might be dynamically
69 ;; referring to the bindings that the lambda arglist established.)
70 ;; One of the uncountable lossages introduced by dynamic scope...
71 ;;
72 ;; Maybe there should be a control-structure that says "turn on
73 ;; fast-and-loose type-assumptive optimizations here." Then when
74 ;; we see a form like (car foo) we can from then on assume that
75 ;; the variable foo is of type cons, and optimize based on that.
76 ;; But, this won't win much because of (you guessed it) dynamic
77 ;; scope. Anything down the stack could change the value.
78 ;; (Another reason it doesn't work is that it is perfectly valid
79 ;; to call car with a null argument.) A better approach might
80 ;; be to allow type-specification of the form
81 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
82 ;; (put 'foo 'result-type 'bool)
83 ;; It should be possible to have these types checked to a certain
84 ;; degree.
85 ;;
86 ;; collapse common subexpressions
87 ;;
88 ;; It would be nice if redundant sequences could be factored out as well,
89 ;; when they are known to have no side-effects:
90 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
91 ;; but beware of traps like
92 ;; (cons (list x y) (list x y))
93 ;;
94 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
95 ;; Tail-recursion elimination is almost always impossible when all variables
96 ;; have dynamic scope, but given that the "return" byteop requires the
97 ;; binding stack to be empty (rather than emptying it itself), there can be
98 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
99 ;; make any bindings.
100 ;;
101 ;; Here is an example of an Emacs Lisp function which could safely be
102 ;; byte-compiled tail-recursively:
103 ;;
104 ;; (defun tail-map (fn list)
105 ;; (cond (list
106 ;; (funcall fn (car list))
107 ;; (tail-map fn (cdr list)))))
108 ;;
109 ;; However, if there was even a single let-binding around the COND,
110 ;; it could not be byte-compiled, because there would be an "unbind"
111 ;; byte-op between the final "call" and "return." Adding a
112 ;; Bunbind_all byteop would fix this.
113 ;;
114 ;; (defun foo (x y z) ... (foo a b c))
115 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
116 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
117 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
118 ;;
119 ;; this also can be considered tail recursion:
120 ;;
121 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
122 ;; could generalize this by doing the optimization
123 ;; (goto X) ... X: (return) --> (return)
124 ;;
125 ;; But this doesn't solve all of the problems: although by doing tail-
126 ;; recursion elimination in this way, the call-stack does not grow, the
127 ;; binding-stack would grow with each recursive step, and would eventually
128 ;; overflow. I don't believe there is any way around this without lexical
129 ;; scope.
130 ;;
131 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
132 ;;
133 ;; Idea: the form (lexical-scope) in a file means that the file may be
134 ;; compiled lexically. This proclamation is file-local. Then, within
135 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
136 ;; would do things the old way. (Or we could use CL "declare" forms.)
137 ;; We'd have to notice defvars and defconsts, since those variables should
138 ;; always be dynamic, and attempting to do a lexical binding of them
139 ;; should simply do a dynamic binding instead.
140 ;; But! We need to know about variables that were not necessarily defvarred
141 ;; in the file being compiled (doing a boundp check isn't good enough.)
142 ;; Fdefvar() would have to be modified to add something to the plist.
143 ;;
144 ;; A major disadvantage of this scheme is that the interpreter and compiler
145 ;; would have different semantics for files compiled with (dynamic-scope).
146 ;; Since this would be a file-local optimization, there would be no way to
147 ;; modify the interpreter to obey this (unless the loader was hacked
148 ;; in some grody way, but that's a really bad idea.)
150 ;; Other things to consider:
152 ;; ;; Associative math should recognize subcalls to identical function:
153 ;; (disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
154 ;; ;; This should generate the same as (1+ x) and (1- x)
156 ;; (disassemble (lambda (x) (cons (+ x 1) (- x 1))))
157 ;; ;; An awful lot of functions always return a non-nil value. If they're
158 ;; ;; error free also they may act as true-constants.
160 ;; (disassemble (lambda (x) (and (point) (foo))))
161 ;; ;; When
162 ;; ;; - all but one arguments to a function are constant
163 ;; ;; - the non-constant argument is an if-expression (cond-expression?)
164 ;; ;; then the outer function can be distributed. If the guarding
165 ;; ;; condition is side-effect-free [assignment-free] then the other
166 ;; ;; arguments may be any expressions. Since, however, the code size
167 ;; ;; can increase this way they should be "simple". Compare:
169 ;; (disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
170 ;; (disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
172 ;; ;; (car (cons A B)) -> (prog1 A B)
173 ;; (disassemble (lambda (x) (car (cons (foo) 42))))
175 ;; ;; (cdr (cons A B)) -> (progn A B)
176 ;; (disassemble (lambda (x) (cdr (cons 42 (foo)))))
178 ;; ;; (car (list A B ...)) -> (prog1 A B ...)
179 ;; (disassemble (lambda (x) (car (list (foo) 42 (bar)))))
181 ;; ;; (cdr (list A B ...)) -> (progn A (list B ...))
182 ;; (disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
185 ;;; Code:
200 arg)
216 c
218 args)))))
224 \f
225 ;;; byte-compile optimizers to support inlining
230 "byte-optimize-handler for the `inline' special-form."
243 sexp)))
247 ;; Splice the given lap code into the current instruction stream.
248 ;; If it has any labels in it, you're responsible for making sure there
249 ;; are no collisions, and that byte-compile-tag-number is reasonable
250 ;; after this is spliced in. The provided list is destroyed.
261 name)
262 form)
263 ;; else
276 ;; Isn't it an error for `string' not to be unibyte?? --stef
284 ;; Give up on inlining.
285 form))))))
287 ;; ((lambda ...) ...)
298 optionalp restp
299 bindings)
306 ;; ok, I'll let this slide because funcall_lambda() does...
307 ;; (if optionalp (error "multiple &optional keywords in %s" name))
313 ;; ...but it is by no stretch of the imagination a reasonable
314 ;; thing that funcall_lambda() allows (&rest x y) and
315 ;; (&rest x &optional y) in arglists.
324 bindings)
325 values nil))
331 bindings)
339 form)
341 ;; The following leads to infinite recursion when loading a
342 ;; file containing `(defsubst f () (f))', and then trying to
343 ;; byte-compile that file.
344 ;(setq body (mapcar 'byte-optimize-form body)))
351 newform)))))
353 \f
354 ;;; implementing source-level optimizers
357 ;;
358 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
359 ;; we need to have special knowledge of the syntax of the special forms
360 ;; like let and defun (that's why they're special forms :-). (Actually,
361 ;; the important aspect is that they are subrs that don't evaluate all of
362 ;; their args.)
363 ;;
365 tmp)
371 form))
376 ;; map (quote nil) to nil to simplify optimizer logic.
377 ;; map quoted constants to nil if for-effect (just because).
380 form))
385 ;; recursively enter the optimizer for the bindings and body
386 ;; of a let or let*. This for depth-firstness: forms that
387 ;; are more deeply nested are optimized first.
392 binding
409 clause))
412 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
431 ;; those subrs which have an implicit progn; it's not quite good
432 ;; enough to treat these like normal function calls.
433 ;; This can turn (save-excursion ...) into (save-excursion) which
434 ;; will be optimized away in the lap-optimize pass.
438 ;; this is just like the above, except for the first argument.
454 ;; take forms off the back until we can't any more.
455 ;; In the future it could conceivably be a problem that the
456 ;; subexpressions of these forms are optimized in the reverse
457 ;; order, but it's ok for now.
463 for-effect))))
475 nil)
478 condition-case save-window-excursion))
479 ;; These forms are compiled as constants or by breaking out
480 ;; all the subexpressions and compiling them separately.
481 form)
484 ;; the "protected" part of an unwind-protect is compiled (and thus
485 ;; optimized) as a top-level form, so don't do it here. But the
486 ;; non-protected part has the same for-effect status as the
487 ;; unwind-protect itself. (The protected part is always for effect,
488 ;; but that isn't handled properly yet.)
494 ;; the body of a catch is compiled (and thus optimized) as a
495 ;; top-level form, so don't do it here. The tag is never
496 ;; for-effect. The body should have the same for-effect status
497 ;; as the catch form itself, but that isn't handled properly yet.
503 ;; Don't treat the args to `ignore' as being
504 ;; computed for effect. We want to avoid the warnings
505 ;; that might occur if they were treated that way.
506 ;; However, don't actually bother calling `ignore'.
509 ;; If optimization is on, this is the only place that macros are
510 ;; expanded. If optimization is off, then macroexpansion happens
511 ;; in byte-compile-form. Otherwise, the macros are already expanded
512 ;; by the time that is reached.
515 byte-compile-macro-environment))))
518 ;; Support compiler macros as in cl.el.
530 form)
535 ;; Detect the expansion of (pop foo).
536 ;; There is no need to compile the call to `car' there.
550 nil)))
552 ;; appending a nil here might not be necessary, but it can't hurt.
557 ;; Otherwise, no args can be considered to be for-effect,
558 ;; even if the called function is for-effect, because we
559 ;; don't know anything about that function.
564 "The source-level pass of the optimizer."
565 ;;
566 ;; First, optimize all sub-forms of this one.
568 ;;
569 ;; after optimizing all subforms, optimize this form until it doesn't
570 ;; optimize any further. This means that some forms will be passed through
571 ;; the optimizer many times, but that's necessary to make the for-effect
572 ;; processing do as much as possible.
573 ;;
578 ;; we don't have any of these yet, but we might.
583 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
586 new)
587 form)))
591 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
592 ;; forms, all but the last of which are optimized with the assumption that
593 ;; they are being called for effect. the last is for-effect as well if
594 ;; all-for-effect is true. returns a new list of forms.
597 fe new)
606 \f
607 ;; some source-level optimizers
608 ;;
609 ;; when writing optimizers, be VERY careful that the optimizer returns
610 ;; something not EQ to its argument if and ONLY if it has made a change.
611 ;; This implies that you cannot simply destructively modify the list;
612 ;; you must return something not EQ to it if you make an optimization.
613 ;;
614 ;; It is now safe to optimize code such that it introduces new bindings.
616 ;; I'd like this to be a defsubst, but let's not be self-referential...
618 ;; Returns non-nil if FORM is a non-nil constant.
624 ;; If the function is being called with constant numeric args,
625 ;; evaluate as much as possible at compile-time. This optimizer
626 ;; assumes that the function is associative, like + or *.
644 form)))
646 ;; If the function is being called with constant numeric args,
647 ;; evaluate as much as possible at compile-time. This optimizer
648 ;; assumes that the function satisfies
649 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
650 ;; like - and /.
654 form
662 constant))))
664 ;;(defun byte-optimize-associative-two-args-math (form)
665 ;; (setq form (byte-optimize-associative-math form))
666 ;; (if (consp form)
667 ;; (byte-optimize-two-args-left form)
668 ;; form))
670 ;;(defun byte-optimize-nonassociative-two-args-math (form)
671 ;; (setq form (byte-optimize-nonassociative-math form))
672 ;; (if (consp form)
673 ;; (byte-optimize-two-args-right form)
674 ;; form))
679 ;; Collect all the constants from FORM, after the STARTth arg,
680 ;; and apply FUN to them to make one argument at the end.
681 ;; For functions that can handle floats, that optimization
682 ;; can be incorrect because reordering can cause an overflow
683 ;; that would otherwise be avoided by encountering an arg that is a float.
684 ;; We avoid this problem by (1) not moving float constants and
685 ;; (2) not moving anything if it would cause an overflow.
687 ;; Merge all FORM's constants from number START, call FUN on them
688 ;; and put the result at the end.
691 ;; t means we must check for overflow.
702 ;; If necessary, check now for overflow
703 ;; that might be caused by reordering.
705 ;; We have overflow if the result of doing the arithmetic
706 ;; on floats is not even close to the result
707 ;; of doing it on integers.
714 form))
719 ;;(setq form (byte-optimize-associative-two-args-math form))
724 ;;; It is not safe to delete the function entirely
725 ;;; (actually, it would be safe if we know the sole arg
726 ;;; is not a marker).
727 ;;; ((null (cdr (cdr form))) (nth 1 form))
731 form))
735 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
745 other)))
749 ;; Put constants at the end, except the last constant.
751 ;; Now only first and last element can be a number.
754 ;; (- x y ... 0) --> (- x y ...)
761 ;; If form is (- CONST foo... CONST), merge first and last.
766 ;;; It is not safe to delete the function entirely
767 ;;; (actually, it would be safe if we know the sole arg
768 ;;; is not a marker).
769 ;;; (if (eq (nth 2 form) 0)
770 ;;; (nth 1 form) ; (- x 0) --> x
775 form))
776 ;;; )
777 )
781 ;; If there is a constant in FORM, it is now the last element.
783 ;;; It is not safe to delete the function entirely
784 ;;; (actually, it would be safe if we know the sole arg
785 ;;; is not a marker or if it appears in other arithmetic).
786 ;;; ((null (cdr (cdr form))) (nth 1 form))
818 last nil))))
820 ;;; ((null (cdr (cdr form)))
821 ;;; (nth 1 form))
849 ;; This can enable some lapcode optimizations.
851 form))
863 form)))
871 form))
915 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
916 ;; take care of this? - Jamie
917 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
918 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
924 form
937 ;; Simplify if less than 2 args.
938 ;; if there is a literal nil in the args to `and', throw it and following
939 ;; forms away, and surround the `and' with (progn ... nil).
948 nil))
954 ;; Throw away nil's, and simplify if less than 2 args.
955 ;; If there is a literal non-nil constant in the args to `or', throw away all
956 ;; following forms.
969 ;; if any clauses have a literal nil as their test, throw them away.
970 ;; if any clause has a literal non-nil constant as its test, throw
971 ;; away all following clauses.
973 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
992 ;;
993 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1001 form))
1002 form))
1005 ;; (if <true-constant> <then> <else...>) ==> <then>
1006 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1007 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1008 ;; (if <test> <then> nil) ==> (if <test> <then>)
1019 form))
1022 ;; Don't make a double negative;
1023 ;; instead, take away the one that is there.
1038 form))
1046 ;; byte-compile-negation-optimizer lives in bytecomp.el
1053 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1054 ;; (funcall foo ...) ==> (foo ...)
1058 form)))
1061 ;; If the last arg is a literal constant, turn this into a funcall.
1062 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1072 "last arg to apply can't be a literal atom: `%s'"
1074 nil))
1075 form)))
1085 ;; No bindings
1088 form)
1089 ;; The body is nil
1106 form))
1116 form)
1118 form))
1125 "Do constant folding for pure functions.
1126 This assumes that the function will not have any side-effects and that
1127 its return value depends solely on its arguments.
1128 If the function can signal an error, this might change the semantics
1129 of FORM by signalling the error at compile-time."
1138 form)))
1140 ;; Avoid having to write forward-... with a negative arg for speed.
1141 ;; Fixme: don't be limited to constant args.
1168 ;; Fixme: delete-char -> delete-region (byte-coded)
1169 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1170 ;; string-make-multibyte for constant args.
1174 ;; Emacs-21's byte-code doesn't run under XEmacs anyway, so we can
1175 ;; safely optimize away this test.
1177 nil
1178 form))
1191 \f
1192 ;; enumerating those functions which need not be called if the returned
1193 ;; value is not used. That is, something like
1194 ;; (progn (list (something-with-side-effects) (yow))
1195 ;; (foo))
1196 ;; may safely be turned into
1197 ;; (progn (progn (something-with-side-effects) (yow))
1198 ;; (foo))
1199 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1201 ;; Some of these functions have the side effect of allocating memory
1202 ;; and it would be incorrect to replace two calls with one.
1203 ;; But we don't try to do those kinds of optimizations,
1204 ;; so it is safe to list such functions here.
1205 ;; Some of these functions return values that depend on environment
1206 ;; state, so that constant folding them would be wrong,
1207 ;; but we don't do constant folding based on this list.
1209 ;; However, at present the only optimization we normally do
1210 ;; is delete calls that need not occur, and we only do that
1211 ;; with the error-free functions.
1213 ;; I wonder if I missed any :-\)
1216 assoc assq
1217 boundp buffer-file-name buffer-local-variables buffer-modified-p
1218 buffer-substring byte-code-function-p
1219 capitalize car-less-than-car car cdr ceiling char-after char-before
1220 char-equal char-to-string char-width
1221 compare-strings concat coordinates-in-window-p
1222 copy-alist copy-sequence copy-marker cos count-lines
1223 decode-time default-boundp default-value documentation downcase
1224 elt exp expt encode-time error-message-string
1225 fboundp fceiling featurep ffloor
1226 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1227 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1228 float float-time floor format format-time-string frame-visible-p
1229 fround ftruncate
1230 get gethash get-buffer get-buffer-window getenv get-file-buffer
1231 hash-table-count
1232 int-to-string intern-soft
1233 keymap-parent
1234 length local-variable-if-set-p local-variable-p log log10 logand
1235 logb logior lognot logxor lsh
1236 make-list make-string make-symbol
1237 marker-buffer max member memq min mod multibyte-char-to-unibyte
1238 next-window nth nthcdr number-to-string
1239 parse-colon-path plist-get plist-member
1240 prefix-numeric-value previous-window prin1-to-string propertize
1241 radians-to-degrees rassq rassoc read-from-string regexp-quote
1242 region-beginning region-end reverse round
1244 string-to-int string-to-number substring sxhash symbol-function
1245 symbol-name symbol-plist symbol-value string-make-unibyte
1246 string-make-multibyte string-as-multibyte string-as-unibyte
1247 tan truncate
1248 unibyte-char-to-multibyte upcase user-full-name
1249 user-login-name user-original-login-name user-variable-p
1250 vconcat
1251 window-buffer window-dedicated-p window-edges window-height
1252 window-hscroll window-minibuffer-p window-width
1253 zerop))
1256 bobp bolp bool-vector-p
1257 buffer-end buffer-list buffer-size buffer-string bufferp
1258 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1259 current-buffer current-global-map current-indentation
1260 current-local-map current-minor-mode-maps current-time
1261 current-time-string current-time-zone
1262 eobp eolp eq equal eventp
1263 floatp following-char framep
1264 get-largest-window get-lru-window
1265 hash-table-p
1266 identity ignore integerp integer-or-marker-p interactive-p
1267 invocation-directory invocation-name
1268 keymapp
1269 line-beginning-position line-end-position list listp
1270 make-marker mark mark-marker markerp memory-limit minibuffer-window
1271 mouse-movement-p
1272 natnump nlistp not null number-or-marker-p numberp
1273 one-window-p overlayp
1274 point point-marker point-min point-max preceding-char processp
1275 recent-keys recursion-depth
1276 safe-length selected-frame selected-window sequencep
1277 standard-case-table standard-syntax-table stringp subrp symbolp
1278 syntax-table syntax-table-p
1279 this-command-keys this-command-keys-vector this-single-command-keys
1280 this-single-command-raw-keys
1281 user-real-login-name user-real-uid user-uid
1282 vector vectorp visible-frame-list
1283 wholenump window-configuration-p window-live-p windowp)))
1290 nil)
1294 ;; form is (byte-code "..." [...] n)
1300 byte-compile-maxdepth))
1305 \f
1309 ;; This function extracts the bitfields from variable-length opcodes.
1310 ;; Originally defined in disass.el (which no longer uses it.)
1313 "Don't call this!"
1314 ;; fetch and return the offset for the current opcode.
1315 ;; return nil if this opcode has no offset
1316 ;; OP, PTR and BYTES are used and set dynamically
1347 ;; This de-compiler is used for inline expansion of compiled functions,
1348 ;; and by the disassembler.
1349 ;;
1350 ;; This list contains numbers, which are pc values,
1351 ;; before each instruction.
1353 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1359 ;; As byte-decompile-bytecode, but updates
1360 ;; byte-compile-{constants, variables, tag-number}.
1361 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1362 ;; with `goto's destined for the end of the code.
1363 ;; That is for use by the compiler.
1364 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1365 ;; In that case, we put a pc value into the list
1366 ;; before each insn (or its label).
1370 lap tmp
1371 endtag)
1376 optr ptr
1380 ;; it's a pc
1386 tags)))))))
1397 byte-compile-variables)))))))
1404 ;; lap = ( [ (pc . (op . arg)) ]* )
1406 lap))
1408 ;; take off the dummy nil op that we replaced a trailing "return" with.
1413 ;; this addr is jumped to
1424 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1427 elt
1431 \f
1432 ;;; peephole optimizer
1438 byte-goto-if-not-nil-else-pop))
1442 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1443 byte-eq byte-not
1444 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1445 byte-interactive-p)
1446 ;; How about other side-effect-free-ops? Is it safe to move an
1447 ;; error invocation (such as from nth) out of an unwind-protect?
1448 ;; No, it is not, because the unwind-protect forms can alter
1449 ;; the inside of the object to which nth would apply.
1450 ;; For the same reason, byte-equal was deleted from this list.
1455 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1456 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1457 byte-point-min byte-following-char byte-preceding-char
1458 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1459 byte-current-buffer byte-interactive-p))
1464 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1465 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1466 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1468 byte-member byte-assq byte-quo byte-rem)
1469 byte-compile-side-effect-and-error-free-ops))
1471 ;; This crock is because of the way DEFVAR_BOOL variables work.
1472 ;; Consider the code
1473 ;;
1474 ;; (defun foo (flag)
1475 ;; (let ((old-pop-ups pop-up-windows)
1476 ;; (pop-up-windows flag))
1477 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1478 ;; (setq old-pop-ups pop-up-windows)
1479 ;; ...))))
1480 ;;
1481 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1482 ;; something else. But if we optimize
1483 ;;
1484 ;; varref flag
1485 ;; varbind pop-up-windows
1486 ;; varref pop-up-windows
1487 ;; not
1488 ;; to
1489 ;; varref flag
1490 ;; dup
1491 ;; varbind pop-up-windows
1492 ;; not
1493 ;;
1494 ;; we break the program, because it will appear that pop-up-windows and
1495 ;; old-pop-ups are not EQ when really they are. So we have to know what
1496 ;; the BOOL variables are, and not perform this optimization on them.
1498 ;; The variable `byte-boolean-vars' is now primitive and updated
1499 ;; automatically by DEFVAR_BOOL.
1502 "Simple peephole optimizer. LAP is both modified and returned.
1503 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1505 lap1
1506 lap2
1509 rest tmp tmp2 tmp3
1511 byte-compile-side-effect-free-ops
1512 byte-compile-side-effect-and-error-free-ops)))
1517 keep-going nil)
1523 ;; You may notice that sequences like "dup varset discard" are
1524 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1525 ;; You may be tempted to change this; resist that temptation.
1527 ;; <side-effect-free> pop --> <deleted>
1528 ;; ...including:
1529 ;; const-X pop --> <deleted>
1530 ;; varref-X pop --> <deleted>
1531 ;; dup pop --> <deleted>
1532 ;;
1552 ;;
1553 ;; goto*-X X: --> X:
1554 ;;
1569 ;;
1570 ;; varset-X varref-X --> dup varset-X
1571 ;; varbind-X varref-X --> dup varbind-X
1572 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1573 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1574 ;; The latter two can enable other optimizations.
1575 ;;
1581 nil
1591 lap0 lap1 lap2 lap0 lap1
1599 ;; The stack depth gets locally increased, so we will
1600 ;; increase maxdepth in case depth = maxdepth here.
1601 ;; This can cause the third argument to byte-code to
1602 ;; be larger than necessary.
1604 ;;
1605 ;; dup varset-X discard --> varset-X
1606 ;; dup varbind-X discard --> varbind-X
1607 ;; (the varbind variant can emerge from other optimizations)
1608 ;;
1616 ;;
1617 ;; not goto-X-if-nil --> goto-X-if-non-nil
1618 ;; not goto-X-if-non-nil --> goto-X-if-nil
1619 ;;
1620 ;; it is wrong to do the same thing for the -else-pop variants.
1621 ;;
1626 lap1
1629 'byte-goto-if-not-nil
1633 'byte-goto-if-not-nil
1637 ;;
1638 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1639 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1640 ;;
1641 ;; it is wrong to do the same thing for the -else-pop variants.
1642 ;;
1650 lap0 lap1 lap2
1655 ;;
1656 ;; const goto-if-* --> whatever
1657 ;;
1665 lap0 lap1)
1678 ;;
1679 ;; varref-X varref-X --> varref-X dup
1680 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1681 ;; We don't optimize the const-X variations on this here,
1682 ;; because that would inhibit some goto optimizations; we
1683 ;; optimize the const-X case after all other optimizations.
1684 ;;
1690 t)
1700 lap0 str lap0 lap0 str)))
1705 ;;
1706 ;; TAG1: TAG2: --> TAG1: <deleted>
1707 ;; (and other references to TAG2 are replaced with TAG1)
1708 ;;
1719 keep-going t))
1720 ;;
1721 ;; unused-TAG: --> <deleted>
1722 ;;
1728 keep-going t))
1729 ;;
1730 ;; goto ... --> goto <delete until TAG or end>
1731 ;; return ... --> return <delete until TAG or end>
1732 ;;
1738 str deleted)
1753 lap0
1759 tagstr lap0 tagstr))))
1762 ;;
1763 ;; <safe-op> unbind --> unbind <safe-op>
1764 ;; (this may enable other optimizations.)
1765 ;;
1772 ;;
1773 ;; varbind-X unbind-N --> discard unbind-(N-1)
1774 ;; save-excursion unbind-N --> unbind-(N-1)
1775 ;; save-restriction unbind-N --> unbind-(N-1)
1776 ;;
1779 byte-save-restriction))
1796 ;;
1797 ;; goto*-X ... X: goto-Y --> goto*-Y
1798 ;; goto-X ... X: return --> return
1799 ;;
1812 ;;
1813 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1814 ;; goto-*-else-pop X ... X: discard --> whatever
1815 ;;
1817 byte-goto-if-not-nil-else-pop))
1824 byte-goto-if-nil)
1826 byte-goto-if-not-nil))))
1832 ;; Get rid of the -else-pop's and jump one step further.
1841 ;;
1842 ;; const goto-X ... X: goto-if-* --> whatever
1843 ;; const goto-X ... X: discard --> whatever
1844 ;;
1856 byte-goto-if-not-nil-else-pop)))
1858 lap0 tmp2 lap0 tmp2)
1861 ;; Let next step fix the (const,goto-if*) sequence.
1864 ;; Jump one step further
1867 lap0 tmp2)
1874 ;;
1875 ;; X: varref-Y ... varset-Y goto-X -->
1876 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1877 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1878 ;; (This is so usual for while loops that it is worth handling).
1879 ;;
1887 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1892 lap1 lap2
1896 )
1901 ;;
1902 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1903 ;; (This can pull the loop test to the end of the loop)
1904 ;;
1911 byte-goto-if-nil-else-pop)))
1912 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1913 ;; lap0 lap1 (cdr lap0) (car tmp))
1922 byte-goto-if-not-nil-else-pop)
1924 byte-goto-if-nil-else-pop))))
1925 newtag)
1928 )
1931 ;; We can handle this case but not the -if-not-nil case,
1932 ;; because we won't know which non-nil constant to push.
1938 byte-goto-if-not-nil
1939 byte-goto-if-nil
1940 byte-goto-if-not-nil
1941 byte-goto byte-goto))))
1942 )
1944 )
1946 )
1947 ;; Cleanup stage:
1948 ;; Rebuild byte-compile-constants / byte-compile-variables.
1949 ;; Simple optimizations that would inhibit other optimizations if they
1950 ;; were done in the optimizing loop, and optimizations which there is no
1951 ;; need to do more than once.
1953 byte-compile-variables nil)
1963 byte-compile-constants)))
1966 byte-compile-variables)))))
1968 ;; const-C varset-X const-C --> const-C dup varset-X
1969 ;; const-C varbind-X const-C --> const-C dup varbind-X
1970 ;;
1976 lap0 lap1 lap0 lap0 lap1)
1980 ;;
1981 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1982 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1983 ;;
1986 tmp2 nil)
1996 ;;
1997 ;; unbind-N unbind-M --> unbind-(N+M)
1998 ;;
2007 )
2010 lap)
2014 \f
2015 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2016 ;; itself, compile some of its most used recursive functions (at load time).
2017 ;;
2028 byte-optimize-body
2029 byte-optimize-predicate
2030 byte-optimize-binary-predicate
2031 ;; Inserted some more than necessary, to speed it up.
2032 byte-optimize-form-code-walker
2033 byte-optimize-lapcode))))
2034 nil)
2036 ;; arch-tag: 0f14076b-737e-4bef-aae6-908826ec1ff1
2037 ;;; byte-opt.el ends here