| blob | a4a0f1ad27900d87bb9f80b5c33a8bf707675e83 |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler
3 ;; Copyright (C) 1991, 1994, 2000, 2001, 2002, 2003, 2004,
4 ;; 2005, 2006, 2007, 2008 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 3, 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., 51 Franklin Street, Fifth Floor,
26 ;; Boston, MA 02110-1301, 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:
201 arg)
217 c
219 args)))))
225 \f
226 ;;; byte-compile optimizers to support inlining
231 "byte-optimize-handler for the `inline' special-form."
244 sexp)))
248 ;; Splice the given lap code into the current instruction stream.
249 ;; If it has any labels in it, you're responsible for making sure there
250 ;; are no collisions, and that byte-compile-tag-number is reasonable
251 ;; after this is spliced in. The provided list is destroyed.
262 name)
263 form)
264 ;; else
277 ;; Isn't it an error for `string' not to be unibyte?? --stef
280 ;; `byte-compile-splice-in-already-compiled-code'
281 ;; takes care of inlining the body.
287 ;; Give up on inlining.
288 form))))))
290 ;; ((lambda ...) ...)
301 optionalp restp
302 bindings)
309 ;; ok, I'll let this slide because funcall_lambda() does...
310 ;; (if optionalp (error "multiple &optional keywords in %s" name))
316 ;; ...but it is by no stretch of the imagination a reasonable
317 ;; thing that funcall_lambda() allows (&rest x y) and
318 ;; (&rest x &optional y) in arglists.
327 bindings)
328 values nil))
334 bindings)
342 form)
344 ;; The following leads to infinite recursion when loading a
345 ;; file containing `(defsubst f () (f))', and then trying to
346 ;; byte-compile that file.
347 ;(setq body (mapcar 'byte-optimize-form body)))
354 newform)))))
356 \f
357 ;;; implementing source-level optimizers
360 ;;
361 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
362 ;; we need to have special knowledge of the syntax of the special forms
363 ;; like let and defun (that's why they're special forms :-). (Actually,
364 ;; the important aspect is that they are subrs that don't evaluate all of
365 ;; their args.)
366 ;;
368 tmp)
374 form))
379 ;; map (quote nil) to nil to simplify optimizer logic.
380 ;; map quoted constants to nil if for-effect (just because).
383 form))
388 ;; recursively enter the optimizer for the bindings and body
389 ;; of a let or let*. This for depth-firstness: forms that
390 ;; are more deeply nested are optimized first.
395 binding
412 clause))
415 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
434 ;; those subrs which have an implicit progn; it's not quite good
435 ;; enough to treat these like normal function calls.
436 ;; This can turn (save-excursion ...) into (save-excursion) which
437 ;; will be optimized away in the lap-optimize pass.
441 ;; this is just like the above, except for the first argument.
457 ;; take forms off the back until we can't any more.
458 ;; In the future it could conceivably be a problem that the
459 ;; subexpressions of these forms are optimized in the reverse
460 ;; order, but it's ok for now.
466 for-effect))))
478 nil)
481 condition-case save-window-excursion))
482 ;; These forms are compiled as constants or by breaking out
483 ;; all the subexpressions and compiling them separately.
484 form)
487 ;; the "protected" part of an unwind-protect is compiled (and thus
488 ;; optimized) as a top-level form, so don't do it here. But the
489 ;; non-protected part has the same for-effect status as the
490 ;; unwind-protect itself. (The protected part is always for effect,
491 ;; but that isn't handled properly yet.)
497 ;; the body of a catch is compiled (and thus optimized) as a
498 ;; top-level form, so don't do it here. The tag is never
499 ;; for-effect. The body should have the same for-effect status
500 ;; as the catch form itself, but that isn't handled properly yet.
506 ;; Don't treat the args to `ignore' as being
507 ;; computed for effect. We want to avoid the warnings
508 ;; that might occur if they were treated that way.
509 ;; However, don't actually bother calling `ignore'.
512 ;; If optimization is on, this is the only place that macros are
513 ;; expanded. If optimization is off, then macroexpansion happens
514 ;; in byte-compile-form. Otherwise, the macros are already expanded
515 ;; by the time that is reached.
518 byte-compile-macro-environment))))
521 ;; Support compiler macros as in cl.el.
533 form)
538 ;; Detect the expansion of (pop foo).
539 ;; There is no need to compile the call to `car' there.
553 nil)))
555 ;; appending a nil here might not be necessary, but it can't hurt.
560 ;; Otherwise, no args can be considered to be for-effect,
561 ;; even if the called function is for-effect, because we
562 ;; don't know anything about that function.
570 "Non-nil if all elements of LIST satisfy `byte-compile-constp'."
576 constant))
579 "The source-level pass of the optimizer."
580 ;;
581 ;; First, optimize all sub-forms of this one.
583 ;;
584 ;; after optimizing all subforms, optimize this form until it doesn't
585 ;; optimize any further. This means that some forms will be passed through
586 ;; the optimizer many times, but that's necessary to make the for-effect
587 ;; processing do as much as possible.
588 ;;
593 ;; we don't have any of these yet, but we might.
598 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
601 new)
602 form)))
606 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
607 ;; forms, all but the last of which are optimized with the assumption that
608 ;; they are being called for effect. the last is for-effect as well if
609 ;; all-for-effect is true. returns a new list of forms.
612 fe new)
621 \f
622 ;; some source-level optimizers
623 ;;
624 ;; when writing optimizers, be VERY careful that the optimizer returns
625 ;; something not EQ to its argument if and ONLY if it has made a change.
626 ;; This implies that you cannot simply destructively modify the list;
627 ;; you must return something not EQ to it if you make an optimization.
628 ;;
629 ;; It is now safe to optimize code such that it introduces new bindings.
632 "Return non-nil if FORM always evaluates to a non-nil value."
642 "Return non-nil if FORM always evaluates to a nil value."
650 ;; If the function is being called with constant numeric args,
651 ;; evaluate as much as possible at compile-time. This optimizer
652 ;; assumes that the function is associative, like + or *.
670 form)))
672 ;; If the function is being called with constant numeric args,
673 ;; evaluate as much as possible at compile-time. This optimizer
674 ;; assumes that the function satisfies
675 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
676 ;; like - and /.
680 form
688 constant))))
690 ;;(defun byte-optimize-associative-two-args-math (form)
691 ;; (setq form (byte-optimize-associative-math form))
692 ;; (if (consp form)
693 ;; (byte-optimize-two-args-left form)
694 ;; form))
696 ;;(defun byte-optimize-nonassociative-two-args-math (form)
697 ;; (setq form (byte-optimize-nonassociative-math form))
698 ;; (if (consp form)
699 ;; (byte-optimize-two-args-right form)
700 ;; form))
705 ;; Collect all the constants from FORM, after the STARTth arg,
706 ;; and apply FUN to them to make one argument at the end.
707 ;; For functions that can handle floats, that optimization
708 ;; can be incorrect because reordering can cause an overflow
709 ;; that would otherwise be avoided by encountering an arg that is a float.
710 ;; We avoid this problem by (1) not moving float constants and
711 ;; (2) not moving anything if it would cause an overflow.
713 ;; Merge all FORM's constants from number START, call FUN on them
714 ;; and put the result at the end.
717 ;; t means we must check for overflow.
728 ;; If necessary, check now for overflow
729 ;; that might be caused by reordering.
731 ;; We have overflow if the result of doing the arithmetic
732 ;; on floats is not even close to the result
733 ;; of doing it on integers.
740 form))
745 ;;(setq form (byte-optimize-associative-two-args-math form))
750 ;;; It is not safe to delete the function entirely
751 ;;; (actually, it would be safe if we know the sole arg
752 ;;; is not a marker).
753 ;;; ((null (cdr (cdr form))) (nth 1 form))
757 form))
761 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
771 other)))
775 ;; Put constants at the end, except the last constant.
777 ;; Now only first and last element can be a number.
780 ;; (- x y ... 0) --> (- x y ...)
787 ;; If form is (- CONST foo... CONST), merge first and last.
792 ;;; It is not safe to delete the function entirely
793 ;;; (actually, it would be safe if we know the sole arg
794 ;;; is not a marker).
795 ;;; (if (eq (nth 2 form) 0)
796 ;;; (nth 1 form) ; (- x 0) --> x
801 form))
802 ;;; )
803 )
807 ;; If there is a constant in FORM, it is now the last element.
809 ;;; It is not safe to delete the function entirely
810 ;;; (actually, it would be safe if we know the sole arg
811 ;;; is not a marker or if it appears in other arithmetic).
812 ;;; ((null (cdr (cdr form))) (nth 1 form))
844 last nil))))
846 ;;; ((null (cdr (cdr form)))
847 ;;; (nth 1 form))
875 ;; This can enable some lapcode optimizations.
877 form))
889 form)))
897 form))
941 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
942 ;; take care of this? - Jamie
943 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
944 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
950 form
963 ;; Simplify if less than 2 args.
964 ;; if there is a literal nil in the args to `and', throw it and following
965 ;; forms away, and surround the `and' with (progn ... nil).
974 nil))
980 ;; Throw away nil's, and simplify if less than 2 args.
981 ;; If there is a literal non-nil constant in the args to `or', throw away all
982 ;; following forms.
995 ;; if any clauses have a literal nil as their test, throw them away.
996 ;; if any clause has a literal non-nil constant as its test, throw
997 ;; away all following clauses.
999 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
1007 ;; This branch will always be taken: kill the subsequent ones.
1016 ;; This branch will never be taken: kill its body.
1018 ;;
1019 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1027 form))
1028 form))
1031 ;; (if (progn <insts> <test>) <rest>) ==> (progn <insts> (if <test> <rest>))
1032 ;; (if <true-constant> <then> <else...>) ==> <then>
1033 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1034 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1035 ;; (if <test> <then> nil) ==> (if <test> <then>)
1038 ;; `clause' is a proper list.
1041 ;; A trivial `progn'.
1054 form))
1057 ;; Don't make a double negative;
1058 ;; instead, take away the one that is there.
1073 form))
1081 ;; byte-compile-negation-optimizer lives in bytecomp.el
1088 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1089 ;; (funcall foo ...) ==> (foo ...)
1093 form)))
1096 ;; If the last arg is a literal constant, turn this into a funcall.
1097 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1107 "last arg to apply can't be a literal atom: `%s'"
1109 nil))
1110 form)))
1120 ;; No bindings
1123 form)
1124 ;; The body is nil
1141 form))
1151 form)
1153 form))
1155 ;; Fixme: delete-char -> delete-region (byte-coded)
1156 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1157 ;; string-make-multibyte for constant args.
1161 ;; Emacs-21's byte-code doesn't run under XEmacs or SXEmacs anyway, so we
1162 ;; can safely optimize away this test.
1164 nil
1166 t
1167 form)))
1180 \f
1181 ;; enumerating those functions which need not be called if the returned
1182 ;; value is not used. That is, something like
1183 ;; (progn (list (something-with-side-effects) (yow))
1184 ;; (foo))
1185 ;; may safely be turned into
1186 ;; (progn (progn (something-with-side-effects) (yow))
1187 ;; (foo))
1188 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1190 ;; Some of these functions have the side effect of allocating memory
1191 ;; and it would be incorrect to replace two calls with one.
1192 ;; But we don't try to do those kinds of optimizations,
1193 ;; so it is safe to list such functions here.
1194 ;; Some of these functions return values that depend on environment
1195 ;; state, so that constant folding them would be wrong,
1196 ;; but we don't do constant folding based on this list.
1198 ;; However, at present the only optimization we normally do
1199 ;; is delete calls that need not occur, and we only do that
1200 ;; with the error-free functions.
1202 ;; I wonder if I missed any :-\)
1205 assoc assq
1206 boundp buffer-file-name buffer-local-variables buffer-modified-p
1207 buffer-substring byte-code-function-p
1208 capitalize car-less-than-car car cdr ceiling char-after char-before
1209 char-equal char-to-string char-width
1210 compare-strings concat coordinates-in-window-p
1211 copy-alist copy-sequence copy-marker cos count-lines
1212 decdoe-char
1213 decode-time default-boundp default-value documentation downcase
1214 elt encode-char exp expt encode-time error-message-string
1215 fboundp fceiling featurep ffloor
1216 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1217 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1218 float float-time floor format format-time-string frame-visible-p
1219 fround ftruncate
1220 get gethash get-buffer get-buffer-window getenv get-file-buffer
1221 hash-table-count
1222 int-to-string intern-soft
1223 keymap-parent
1224 length local-variable-if-set-p local-variable-p log log10 logand
1225 logb logior lognot logxor lsh langinfo
1226 make-list make-string make-symbol
1227 marker-buffer max member memq min mod multibyte-char-to-unibyte
1228 next-window nth nthcdr number-to-string
1229 parse-colon-path plist-get plist-member
1230 prefix-numeric-value previous-window prin1-to-string propertize
1231 radians-to-degrees rassq rassoc read-from-string regexp-quote
1232 region-beginning region-end reverse round
1234 string-to-int string-to-number substring sxhash symbol-function
1235 symbol-name symbol-plist symbol-value string-make-unibyte
1236 string-make-multibyte string-as-multibyte string-as-unibyte
1237 string-to-multibyte
1238 tan truncate
1239 unibyte-char-to-multibyte upcase user-full-name
1240 user-login-name user-original-login-name user-variable-p
1241 vconcat
1242 window-buffer window-dedicated-p window-edges window-height
1243 window-hscroll window-minibuffer-p window-width
1244 zerop))
1247 bobp bolp bool-vector-p
1248 buffer-end buffer-list buffer-size buffer-string bufferp
1249 car-safe case-table-p cdr-safe char-or-string-p characterp
1250 charsetp commandp cons consp
1251 current-buffer current-global-map current-indentation
1252 current-local-map current-minor-mode-maps current-time
1253 current-time-string current-time-zone
1254 eobp eolp eq equal eventp
1255 floatp following-char framep
1256 get-largest-window get-lru-window
1257 hash-table-p
1258 identity ignore integerp integer-or-marker-p interactive-p
1259 invocation-directory invocation-name
1260 keymapp
1261 line-beginning-position line-end-position list listp
1262 make-marker mark mark-marker markerp max-char
1263 memory-limit minibuffer-window
1264 mouse-movement-p
1265 natnump nlistp not null number-or-marker-p numberp
1266 one-window-p overlayp
1267 point point-marker point-min point-max preceding-char primary-charset
1268 processp
1269 recent-keys recursion-depth
1270 safe-length selected-frame selected-window sequencep
1271 standard-case-table standard-syntax-table stringp subrp symbolp
1272 syntax-table syntax-table-p
1273 this-command-keys this-command-keys-vector this-single-command-keys
1274 this-single-command-raw-keys
1275 user-real-login-name user-real-uid user-uid
1276 vector vectorp visible-frame-list
1277 wholenump window-configuration-p window-live-p windowp)))
1284 nil)
1286 \f
1287 ;; pure functions are side-effect free functions whose values depend
1288 ;; only on their arguments. For these functions, calls with constant
1289 ;; arguments can be evaluated at compile time. This may shift run time
1290 ;; errors to compile time.
1297 nil)
1300 ;; form is (byte-code "..." [...] n)
1306 byte-compile-maxdepth))
1311 \f
1315 ;; This function extracts the bitfields from variable-length opcodes.
1316 ;; Originally defined in disass.el (which no longer uses it.)
1319 "Don't call this!"
1320 ;; fetch and return the offset for the current opcode.
1321 ;; return nil if this opcode has no offset
1322 ;; OP, PTR and BYTES are used and set dynamically
1353 ;; This de-compiler is used for inline expansion of compiled functions,
1354 ;; and by the disassembler.
1355 ;;
1356 ;; This list contains numbers, which are pc values,
1357 ;; before each instruction.
1359 "Turn BYTECODE into lapcode, referring to CONSTVEC."
1365 ;; As byte-decompile-bytecode, but updates
1366 ;; byte-compile-{constants, variables, tag-number}.
1367 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1368 ;; with `goto's destined for the end of the code.
1369 ;; That is for use by the compiler.
1370 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1371 ;; In that case, we put a pc value into the list
1372 ;; before each insn (or its label).
1376 lap tmp
1377 endtag)
1382 optr ptr
1386 ;; it's a pc
1392 tags)))))))
1403 byte-compile-variables)))))))
1410 ;; lap = ( [ (pc . (op . arg)) ]* )
1412 lap))
1414 ;; take off the dummy nil op that we replaced a trailing "return" with.
1419 ;; this addr is jumped to
1430 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1433 elt
1437 \f
1438 ;;; peephole optimizer
1444 byte-goto-if-not-nil-else-pop))
1448 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1449 byte-eq byte-not
1450 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1451 byte-interactive-p)
1452 ;; How about other side-effect-free-ops? Is it safe to move an
1453 ;; error invocation (such as from nth) out of an unwind-protect?
1454 ;; No, it is not, because the unwind-protect forms can alter
1455 ;; the inside of the object to which nth would apply.
1456 ;; For the same reason, byte-equal was deleted from this list.
1461 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1462 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1463 byte-point-min byte-following-char byte-preceding-char
1464 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1465 byte-current-buffer byte-interactive-p))
1470 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1471 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1472 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1474 byte-member byte-assq byte-quo byte-rem)
1475 byte-compile-side-effect-and-error-free-ops))
1477 ;; This crock is because of the way DEFVAR_BOOL variables work.
1478 ;; Consider the code
1479 ;;
1480 ;; (defun foo (flag)
1481 ;; (let ((old-pop-ups pop-up-windows)
1482 ;; (pop-up-windows flag))
1483 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1484 ;; (setq old-pop-ups pop-up-windows)
1485 ;; ...))))
1486 ;;
1487 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1488 ;; something else. But if we optimize
1489 ;;
1490 ;; varref flag
1491 ;; varbind pop-up-windows
1492 ;; varref pop-up-windows
1493 ;; not
1494 ;; to
1495 ;; varref flag
1496 ;; dup
1497 ;; varbind pop-up-windows
1498 ;; not
1499 ;;
1500 ;; we break the program, because it will appear that pop-up-windows and
1501 ;; old-pop-ups are not EQ when really they are. So we have to know what
1502 ;; the BOOL variables are, and not perform this optimization on them.
1504 ;; The variable `byte-boolean-vars' is now primitive and updated
1505 ;; automatically by DEFVAR_BOOL.
1508 "Simple peephole optimizer. LAP is both modified and returned.
1509 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1511 lap1
1512 lap2
1515 rest tmp tmp2 tmp3
1517 byte-compile-side-effect-free-ops
1518 byte-compile-side-effect-and-error-free-ops)))
1523 keep-going nil)
1529 ;; You may notice that sequences like "dup varset discard" are
1530 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1531 ;; You may be tempted to change this; resist that temptation.
1533 ;; <side-effect-free> pop --> <deleted>
1534 ;; ...including:
1535 ;; const-X pop --> <deleted>
1536 ;; varref-X pop --> <deleted>
1537 ;; dup pop --> <deleted>
1538 ;;
1558 ;;
1559 ;; goto*-X X: --> X:
1560 ;;
1575 ;;
1576 ;; varset-X varref-X --> dup varset-X
1577 ;; varbind-X varref-X --> dup varbind-X
1578 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1579 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1580 ;; The latter two can enable other optimizations.
1581 ;;
1587 nil
1597 lap0 lap1 lap2 lap0 lap1
1605 ;; The stack depth gets locally increased, so we will
1606 ;; increase maxdepth in case depth = maxdepth here.
1607 ;; This can cause the third argument to byte-code to
1608 ;; be larger than necessary.
1610 ;;
1611 ;; dup varset-X discard --> varset-X
1612 ;; dup varbind-X discard --> varbind-X
1613 ;; (the varbind variant can emerge from other optimizations)
1614 ;;
1622 ;;
1623 ;; not goto-X-if-nil --> goto-X-if-non-nil
1624 ;; not goto-X-if-non-nil --> goto-X-if-nil
1625 ;;
1626 ;; it is wrong to do the same thing for the -else-pop variants.
1627 ;;
1632 lap1
1635 'byte-goto-if-not-nil
1639 'byte-goto-if-not-nil
1643 ;;
1644 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1645 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1646 ;;
1647 ;; it is wrong to do the same thing for the -else-pop variants.
1648 ;;
1656 lap0 lap1 lap2
1661 ;;
1662 ;; const goto-if-* --> whatever
1663 ;;
1671 lap0 lap1)
1684 ;;
1685 ;; varref-X varref-X --> varref-X dup
1686 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1687 ;; We don't optimize the const-X variations on this here,
1688 ;; because that would inhibit some goto optimizations; we
1689 ;; optimize the const-X case after all other optimizations.
1690 ;;
1696 t)
1706 lap0 str lap0 lap0 str)))
1711 ;;
1712 ;; TAG1: TAG2: --> TAG1: <deleted>
1713 ;; (and other references to TAG2 are replaced with TAG1)
1714 ;;
1725 keep-going t))
1726 ;;
1727 ;; unused-TAG: --> <deleted>
1728 ;;
1734 keep-going t))
1735 ;;
1736 ;; goto ... --> goto <delete until TAG or end>
1737 ;; return ... --> return <delete until TAG or end>
1738 ;;
1744 str deleted)
1759 lap0
1765 tagstr lap0 tagstr))))
1768 ;;
1769 ;; <safe-op> unbind --> unbind <safe-op>
1770 ;; (this may enable other optimizations.)
1771 ;;
1778 ;;
1779 ;; varbind-X unbind-N --> discard unbind-(N-1)
1780 ;; save-excursion unbind-N --> unbind-(N-1)
1781 ;; save-restriction unbind-N --> unbind-(N-1)
1782 ;;
1785 byte-save-restriction))
1802 ;;
1803 ;; goto*-X ... X: goto-Y --> goto*-Y
1804 ;; goto-X ... X: return --> return
1805 ;;
1818 ;;
1819 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1820 ;; goto-*-else-pop X ... X: discard --> whatever
1821 ;;
1823 byte-goto-if-not-nil-else-pop))
1830 byte-goto-if-nil)
1832 byte-goto-if-not-nil))))
1838 ;; Get rid of the -else-pop's and jump one step further.
1847 ;;
1848 ;; const goto-X ... X: goto-if-* --> whatever
1849 ;; const goto-X ... X: discard --> whatever
1850 ;;
1862 byte-goto-if-not-nil-else-pop)))
1864 lap0 tmp2 lap0 tmp2)
1867 ;; Let next step fix the (const,goto-if*) sequence.
1870 ;; Jump one step further
1873 lap0 tmp2)
1880 ;;
1881 ;; X: varref-Y ... varset-Y goto-X -->
1882 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1883 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1884 ;; (This is so usual for while loops that it is worth handling).
1885 ;;
1893 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1898 lap1 lap2
1902 )
1907 ;;
1908 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1909 ;; (This can pull the loop test to the end of the loop)
1910 ;;
1917 byte-goto-if-nil-else-pop)))
1918 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1919 ;; lap0 lap1 (cdr lap0) (car tmp))
1928 byte-goto-if-not-nil-else-pop)
1930 byte-goto-if-nil-else-pop))))
1931 newtag)
1934 )
1937 ;; We can handle this case but not the -if-not-nil case,
1938 ;; because we won't know which non-nil constant to push.
1944 byte-goto-if-not-nil
1945 byte-goto-if-nil
1946 byte-goto-if-not-nil
1947 byte-goto byte-goto))))
1948 )
1950 )
1952 )
1953 ;; Cleanup stage:
1954 ;; Rebuild byte-compile-constants / byte-compile-variables.
1955 ;; Simple optimizations that would inhibit other optimizations if they
1956 ;; were done in the optimizing loop, and optimizations which there is no
1957 ;; need to do more than once.
1959 byte-compile-variables nil)
1969 byte-compile-constants)))
1972 byte-compile-variables)))))
1974 ;; const-C varset-X const-C --> const-C dup varset-X
1975 ;; const-C varbind-X const-C --> const-C dup varbind-X
1976 ;;
1982 lap0 lap1 lap0 lap0 lap1)
1986 ;;
1987 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1988 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1989 ;;
1992 tmp2 nil)
2002 ;;
2003 ;; unbind-N unbind-M --> unbind-(N+M)
2004 ;;
2013 )
2016 lap)
2020 \f
2021 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2022 ;; itself, compile some of its most used recursive functions (at load time).
2023 ;;
2034 byte-optimize-body
2035 byte-optimize-predicate
2036 byte-optimize-binary-predicate
2037 ;; Inserted some more than necessary, to speed it up.
2038 byte-optimize-form-code-walker
2039 byte-optimize-lapcode))))
2040 nil)
2042 ;; arch-tag: 0f14076b-737e-4bef-aae6-908826ec1ff1
2043 ;;; byte-opt.el ends here