| blob | c34c88cb72d066cc4ff889a10ee80352176b9450 |
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 of the License, or
16 ;; (at your option) 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. If not, see <http://www.gnu.org/licenses/>.
26 ;;; Commentary:
28 ;; ========================================================================
29 ;; "No matter how hard you try, you can't make a racehorse out of a pig.
30 ;; You can, however, make a faster pig."
31 ;;
32 ;; Or, to put it another way, the Emacs byte compiler is a VW Bug. This code
33 ;; makes it be a VW Bug with fuel injection and a turbocharger... You're
34 ;; still not going to make it go faster than 70 mph, but it might be easier
35 ;; to get it there.
36 ;;
38 ;; TO DO:
39 ;;
40 ;; (apply (lambda (x &rest y) ...) 1 (foo))
41 ;;
42 ;; maintain a list of functions known not to access any global variables
43 ;; (actually, give them a 'dynamically-safe property) and then
44 ;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
45 ;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
46 ;; by recursing on this, we might be able to eliminate the entire let.
47 ;; However certain variables should never have their bindings optimized
48 ;; away, because they affect everything.
49 ;; (put 'debug-on-error 'binding-is-magic t)
50 ;; (put 'debug-on-abort 'binding-is-magic t)
51 ;; (put 'debug-on-next-call 'binding-is-magic t)
52 ;; (put 'inhibit-quit 'binding-is-magic t)
53 ;; (put 'quit-flag 'binding-is-magic t)
54 ;; (put 't 'binding-is-magic t)
55 ;; (put 'nil 'binding-is-magic t)
56 ;; possibly also
57 ;; (put 'gc-cons-threshold 'binding-is-magic t)
58 ;; (put 'track-mouse 'binding-is-magic t)
59 ;; others?
60 ;;
61 ;; Simple defsubsts often produce forms like
62 ;; (let ((v1 (f1)) (v2 (f2)) ...)
63 ;; (FN v1 v2 ...))
64 ;; It would be nice if we could optimize this to
65 ;; (FN (f1) (f2) ...)
66 ;; but we can't unless FN is dynamically-safe (it might be dynamically
67 ;; referring to the bindings that the lambda arglist established.)
68 ;; One of the uncountable lossages introduced by dynamic scope...
69 ;;
70 ;; Maybe there should be a control-structure that says "turn on
71 ;; fast-and-loose type-assumptive optimizations here." Then when
72 ;; we see a form like (car foo) we can from then on assume that
73 ;; the variable foo is of type cons, and optimize based on that.
74 ;; But, this won't win much because of (you guessed it) dynamic
75 ;; scope. Anything down the stack could change the value.
76 ;; (Another reason it doesn't work is that it is perfectly valid
77 ;; to call car with a null argument.) A better approach might
78 ;; be to allow type-specification of the form
79 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
80 ;; (put 'foo 'result-type 'bool)
81 ;; It should be possible to have these types checked to a certain
82 ;; degree.
83 ;;
84 ;; collapse common subexpressions
85 ;;
86 ;; It would be nice if redundant sequences could be factored out as well,
87 ;; when they are known to have no side-effects:
88 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
89 ;; but beware of traps like
90 ;; (cons (list x y) (list x y))
91 ;;
92 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
93 ;; Tail-recursion elimination is almost always impossible when all variables
94 ;; have dynamic scope, but given that the "return" byteop requires the
95 ;; binding stack to be empty (rather than emptying it itself), there can be
96 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
97 ;; make any bindings.
98 ;;
99 ;; Here is an example of an Emacs Lisp function which could safely be
100 ;; byte-compiled tail-recursively:
101 ;;
102 ;; (defun tail-map (fn list)
103 ;; (cond (list
104 ;; (funcall fn (car list))
105 ;; (tail-map fn (cdr list)))))
106 ;;
107 ;; However, if there was even a single let-binding around the COND,
108 ;; it could not be byte-compiled, because there would be an "unbind"
109 ;; byte-op between the final "call" and "return." Adding a
110 ;; Bunbind_all byteop would fix this.
111 ;;
112 ;; (defun foo (x y z) ... (foo a b c))
113 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
114 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
115 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
116 ;;
117 ;; this also can be considered tail recursion:
118 ;;
119 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
120 ;; could generalize this by doing the optimization
121 ;; (goto X) ... X: (return) --> (return)
122 ;;
123 ;; But this doesn't solve all of the problems: although by doing tail-
124 ;; recursion elimination in this way, the call-stack does not grow, the
125 ;; binding-stack would grow with each recursive step, and would eventually
126 ;; overflow. I don't believe there is any way around this without lexical
127 ;; scope.
128 ;;
129 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
130 ;;
131 ;; Idea: the form (lexical-scope) in a file means that the file may be
132 ;; compiled lexically. This proclamation is file-local. Then, within
133 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
134 ;; would do things the old way. (Or we could use CL "declare" forms.)
135 ;; We'd have to notice defvars and defconsts, since those variables should
136 ;; always be dynamic, and attempting to do a lexical binding of them
137 ;; should simply do a dynamic binding instead.
138 ;; But! We need to know about variables that were not necessarily defvarred
139 ;; in the file being compiled (doing a boundp check isn't good enough.)
140 ;; Fdefvar() would have to be modified to add something to the plist.
141 ;;
142 ;; A major disadvantage of this scheme is that the interpreter and compiler
143 ;; would have different semantics for files compiled with (dynamic-scope).
144 ;; Since this would be a file-local optimization, there would be no way to
145 ;; modify the interpreter to obey this (unless the loader was hacked
146 ;; in some grody way, but that's a really bad idea.)
148 ;; Other things to consider:
150 ;; ;; Associative math should recognize subcalls to identical function:
151 ;; (disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
152 ;; ;; This should generate the same as (1+ x) and (1- x)
154 ;; (disassemble (lambda (x) (cons (+ x 1) (- x 1))))
155 ;; ;; An awful lot of functions always return a non-nil value. If they're
156 ;; ;; error free also they may act as true-constants.
158 ;; (disassemble (lambda (x) (and (point) (foo))))
159 ;; ;; When
160 ;; ;; - all but one arguments to a function are constant
161 ;; ;; - the non-constant argument is an if-expression (cond-expression?)
162 ;; ;; then the outer function can be distributed. If the guarding
163 ;; ;; condition is side-effect-free [assignment-free] then the other
164 ;; ;; arguments may be any expressions. Since, however, the code size
165 ;; ;; can increase this way they should be "simple". Compare:
167 ;; (disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
168 ;; (disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
170 ;; ;; (car (cons A B)) -> (prog1 A B)
171 ;; (disassemble (lambda (x) (car (cons (foo) 42))))
173 ;; ;; (cdr (cons A B)) -> (progn A B)
174 ;; (disassemble (lambda (x) (cdr (cons 42 (foo)))))
176 ;; ;; (car (list A B ...)) -> (prog1 A B ...)
177 ;; (disassemble (lambda (x) (car (list (foo) 42 (bar)))))
179 ;; ;; (cdr (list A B ...)) -> (progn A (list B ...))
180 ;; (disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
183 ;;; 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
278 ;; `byte-compile-splice-in-already-compiled-code'
279 ;; takes care of inlining the body.
285 ;; Give up on inlining.
286 form))))))
288 ;; ((lambda ...) ...)
299 optionalp restp
300 bindings)
307 ;; ok, I'll let this slide because funcall_lambda() does...
308 ;; (if optionalp (error "multiple &optional keywords in %s" name))
314 ;; ...but it is by no stretch of the imagination a reasonable
315 ;; thing that funcall_lambda() allows (&rest x y) and
316 ;; (&rest x &optional y) in arglists.
325 bindings)
326 values nil))
332 bindings)
340 form)
342 ;; The following leads to infinite recursion when loading a
343 ;; file containing `(defsubst f () (f))', and then trying to
344 ;; byte-compile that file.
345 ;(setq body (mapcar 'byte-optimize-form body)))
352 newform)))))
354 \f
355 ;;; implementing source-level optimizers
358 ;;
359 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
360 ;; we need to have special knowledge of the syntax of the special forms
361 ;; like let and defun (that's why they're special forms :-). (Actually,
362 ;; the important aspect is that they are subrs that don't evaluate all of
363 ;; their args.)
364 ;;
366 tmp)
372 form))
377 ;; map (quote nil) to nil to simplify optimizer logic.
378 ;; map quoted constants to nil if for-effect (just because).
381 form))
386 for-effect))
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."
638 ;; Can't use recursion in a defsubst.
639 ;; (progn (byte-compile-trueconstp (car (last (cdr form)))))
640 ))
646 "Return non-nil if FORM always evaluates to a nil value."
652 ;; Can't use recursion in a defsubst.
653 ;; (progn (byte-compile-nilconstp (car (last (cdr form)))))
654 ))
658 ;; If the function is being called with constant numeric args,
659 ;; evaluate as much as possible at compile-time. This optimizer
660 ;; assumes that the function is associative, like + or *.
678 form)))
680 ;; If the function is being called with constant numeric args,
681 ;; evaluate as much as possible at compile-time. This optimizer
682 ;; assumes that the function satisfies
683 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
684 ;; like - and /.
688 form
696 constant))))
698 ;;(defun byte-optimize-associative-two-args-math (form)
699 ;; (setq form (byte-optimize-associative-math form))
700 ;; (if (consp form)
701 ;; (byte-optimize-two-args-left form)
702 ;; form))
704 ;;(defun byte-optimize-nonassociative-two-args-math (form)
705 ;; (setq form (byte-optimize-nonassociative-math form))
706 ;; (if (consp form)
707 ;; (byte-optimize-two-args-right form)
708 ;; form))
713 ;; Collect all the constants from FORM, after the STARTth arg,
714 ;; and apply FUN to them to make one argument at the end.
715 ;; For functions that can handle floats, that optimization
716 ;; can be incorrect because reordering can cause an overflow
717 ;; that would otherwise be avoided by encountering an arg that is a float.
718 ;; We avoid this problem by (1) not moving float constants and
719 ;; (2) not moving anything if it would cause an overflow.
721 ;; Merge all FORM's constants from number START, call FUN on them
722 ;; and put the result at the end.
725 ;; t means we must check for overflow.
736 ;; If necessary, check now for overflow
737 ;; that might be caused by reordering.
739 ;; We have overflow if the result of doing the arithmetic
740 ;; on floats is not even close to the result
741 ;; of doing it on integers.
748 form))
753 ;;(setq form (byte-optimize-associative-two-args-math form))
758 ;;; It is not safe to delete the function entirely
759 ;;; (actually, it would be safe if we know the sole arg
760 ;;; is not a marker).
761 ;;; ((null (cdr (cdr form))) (nth 1 form))
765 form))
769 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
779 other)))
783 ;; Put constants at the end, except the last constant.
785 ;; Now only first and last element can be a number.
788 ;; (- x y ... 0) --> (- x y ...)
795 ;; If form is (- CONST foo... CONST), merge first and last.
800 ;;; It is not safe to delete the function entirely
801 ;;; (actually, it would be safe if we know the sole arg
802 ;;; is not a marker).
803 ;;; (if (eq (nth 2 form) 0)
804 ;;; (nth 1 form) ; (- x 0) --> x
809 form))
810 ;;; )
811 )
815 ;; If there is a constant in FORM, it is now the last element.
817 ;;; It is not safe to delete the function entirely
818 ;;; (actually, it would be safe if we know the sole arg
819 ;;; is not a marker or if it appears in other arithmetic).
820 ;;; ((null (cdr (cdr form))) (nth 1 form))
852 last nil))))
854 ;;; ((null (cdr (cdr form)))
855 ;;; (nth 1 form))
883 ;; This can enable some lapcode optimizations.
885 form))
897 form)))
905 form))
949 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
950 ;; take care of this? - Jamie
951 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
952 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
958 form
971 ;; Simplify if less than 2 args.
972 ;; if there is a literal nil in the args to `and', throw it and following
973 ;; forms away, and surround the `and' with (progn ... nil).
982 nil))
988 ;; Throw away nil's, and simplify if less than 2 args.
989 ;; If there is a literal non-nil constant in the args to `or', throw away all
990 ;; following forms.
1003 ;; if any clauses have a literal nil as their test, throw them away.
1004 ;; if any clause has a literal non-nil constant as its test, throw
1005 ;; away all following clauses.
1007 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
1015 ;; This branch will always be taken: kill the subsequent ones.
1024 ;; This branch will never be taken: kill its body.
1026 ;;
1027 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1035 form))
1036 form))
1039 ;; (if (progn <insts> <test>) <rest>) ==> (progn <insts> (if <test> <rest>))
1040 ;; (if <true-constant> <then> <else...>) ==> <then>
1041 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1042 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1043 ;; (if <test> <then> nil) ==> (if <test> <then>)
1046 ;; `clause' is a proper list.
1049 ;; A trivial `progn'.
1062 form))
1065 ;; Don't make a double negative;
1066 ;; instead, take away the one that is there.
1081 form))
1089 ;; byte-compile-negation-optimizer lives in bytecomp.el
1096 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1097 ;; (funcall foo ...) ==> (foo ...)
1101 form)))
1104 ;; If the last arg is a literal constant, turn this into a funcall.
1105 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1115 "last arg to apply can't be a literal atom: `%s'"
1117 nil))
1118 form)))
1128 ;; No bindings
1131 form)
1132 ;; The body is nil
1149 form))
1159 form)
1161 form))
1163 ;; Fixme: delete-char -> delete-region (byte-coded)
1164 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1165 ;; string-make-multibyte for constant args.
1169 ;; Emacs-21's byte-code doesn't run under XEmacs or SXEmacs anyway, so we
1170 ;; can safely optimize away this test.
1172 nil
1174 t
1175 form)))
1188 \f
1189 ;; enumerating those functions which need not be called if the returned
1190 ;; value is not used. That is, something like
1191 ;; (progn (list (something-with-side-effects) (yow))
1192 ;; (foo))
1193 ;; may safely be turned into
1194 ;; (progn (progn (something-with-side-effects) (yow))
1195 ;; (foo))
1196 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1198 ;; Some of these functions have the side effect of allocating memory
1199 ;; and it would be incorrect to replace two calls with one.
1200 ;; But we don't try to do those kinds of optimizations,
1201 ;; so it is safe to list such functions here.
1202 ;; Some of these functions return values that depend on environment
1203 ;; state, so that constant folding them would be wrong,
1204 ;; but we don't do constant folding based on this list.
1206 ;; However, at present the only optimization we normally do
1207 ;; is delete calls that need not occur, and we only do that
1208 ;; with the error-free functions.
1210 ;; I wonder if I missed any :-\)
1213 assoc assq
1214 boundp buffer-file-name buffer-local-variables buffer-modified-p
1215 buffer-substring byte-code-function-p
1216 capitalize car-less-than-car car cdr ceiling char-after char-before
1217 char-equal char-to-string char-width
1218 compare-strings concat coordinates-in-window-p
1219 copy-alist copy-sequence copy-marker cos count-lines
1220 decode-char
1221 decode-time default-boundp default-value documentation downcase
1222 elt encode-char 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 langinfo
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 string-to-multibyte
1246 tan truncate
1247 unibyte-char-to-multibyte upcase user-full-name
1248 user-login-name user-original-login-name user-variable-p
1249 vconcat
1250 window-buffer window-dedicated-p window-edges window-height
1251 window-hscroll window-minibuffer-p window-width
1252 zerop))
1255 bobp bolp bool-vector-p
1256 buffer-end buffer-list buffer-size buffer-string bufferp
1257 car-safe case-table-p cdr-safe char-or-string-p characterp
1258 charsetp 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 max-char
1271 memory-limit minibuffer-window
1272 mouse-movement-p
1273 natnump nlistp not null number-or-marker-p numberp
1274 one-window-p overlayp
1275 point point-marker point-min point-max preceding-char primary-charset
1276 processp
1277 recent-keys recursion-depth
1278 safe-length selected-frame selected-window sequencep
1279 standard-case-table standard-syntax-table stringp subrp symbolp
1280 syntax-table syntax-table-p
1281 this-command-keys this-command-keys-vector this-single-command-keys
1282 this-single-command-raw-keys
1283 user-real-login-name user-real-uid user-uid
1284 vector vectorp visible-frame-list
1285 wholenump window-configuration-p window-live-p windowp)))
1292 nil)
1294 \f
1295 ;; pure functions are side-effect free functions whose values depend
1296 ;; only on their arguments. For these functions, calls with constant
1297 ;; arguments can be evaluated at compile time. This may shift run time
1298 ;; errors to compile time.
1305 nil)
1308 ;; form is (byte-code "..." [...] n)
1314 byte-compile-maxdepth))
1319 \f
1323 ;; This function extracts the bitfields from variable-length opcodes.
1324 ;; Originally defined in disass.el (which no longer uses it.)
1327 "Don't call this!"
1328 ;; fetch and return the offset for the current opcode.
1329 ;; return nil if this opcode has no offset
1330 ;; OP, PTR and BYTES are used and set dynamically
1361 ;; This de-compiler is used for inline expansion of compiled functions,
1362 ;; and by the disassembler.
1363 ;;
1364 ;; This list contains numbers, which are pc values,
1365 ;; before each instruction.
1367 "Turn BYTECODE into lapcode, referring to CONSTVEC."
1373 ;; As byte-decompile-bytecode, but updates
1374 ;; byte-compile-{constants, variables, tag-number}.
1375 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1376 ;; with `goto's destined for the end of the code.
1377 ;; That is for use by the compiler.
1378 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1379 ;; In that case, we put a pc value into the list
1380 ;; before each insn (or its label).
1384 lap tmp
1385 endtag)
1390 optr ptr
1394 ;; it's a pc
1400 tags)))))))
1411 byte-compile-variables)))))))
1418 ;; lap = ( [ (pc . (op . arg)) ]* )
1420 lap))
1422 ;; take off the dummy nil op that we replaced a trailing "return" with.
1427 ;; this addr is jumped to
1438 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1441 elt
1445 \f
1446 ;;; peephole optimizer
1452 byte-goto-if-not-nil-else-pop))
1456 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1457 byte-eq byte-not
1458 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1459 byte-interactive-p)
1460 ;; How about other side-effect-free-ops? Is it safe to move an
1461 ;; error invocation (such as from nth) out of an unwind-protect?
1462 ;; No, it is not, because the unwind-protect forms can alter
1463 ;; the inside of the object to which nth would apply.
1464 ;; For the same reason, byte-equal was deleted from this list.
1469 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1470 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1471 byte-point-min byte-following-char byte-preceding-char
1472 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1473 byte-current-buffer byte-interactive-p))
1478 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1479 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1480 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1482 byte-member byte-assq byte-quo byte-rem)
1483 byte-compile-side-effect-and-error-free-ops))
1485 ;; This crock is because of the way DEFVAR_BOOL variables work.
1486 ;; Consider the code
1487 ;;
1488 ;; (defun foo (flag)
1489 ;; (let ((old-pop-ups pop-up-windows)
1490 ;; (pop-up-windows flag))
1491 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1492 ;; (setq old-pop-ups pop-up-windows)
1493 ;; ...))))
1494 ;;
1495 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1496 ;; something else. But if we optimize
1497 ;;
1498 ;; varref flag
1499 ;; varbind pop-up-windows
1500 ;; varref pop-up-windows
1501 ;; not
1502 ;; to
1503 ;; varref flag
1504 ;; dup
1505 ;; varbind pop-up-windows
1506 ;; not
1507 ;;
1508 ;; we break the program, because it will appear that pop-up-windows and
1509 ;; old-pop-ups are not EQ when really they are. So we have to know what
1510 ;; the BOOL variables are, and not perform this optimization on them.
1512 ;; The variable `byte-boolean-vars' is now primitive and updated
1513 ;; automatically by DEFVAR_BOOL.
1516 "Simple peephole optimizer. LAP is both modified and returned.
1517 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1519 lap1
1520 lap2
1523 rest tmp tmp2 tmp3
1525 byte-compile-side-effect-free-ops
1526 byte-compile-side-effect-and-error-free-ops)))
1531 keep-going nil)
1537 ;; You may notice that sequences like "dup varset discard" are
1538 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1539 ;; You may be tempted to change this; resist that temptation.
1541 ;; <side-effect-free> pop --> <deleted>
1542 ;; ...including:
1543 ;; const-X pop --> <deleted>
1544 ;; varref-X pop --> <deleted>
1545 ;; dup pop --> <deleted>
1546 ;;
1566 ;;
1567 ;; goto*-X X: --> X:
1568 ;;
1583 ;;
1584 ;; varset-X varref-X --> dup varset-X
1585 ;; varbind-X varref-X --> dup varbind-X
1586 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1587 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1588 ;; The latter two can enable other optimizations.
1589 ;;
1595 nil
1605 lap0 lap1 lap2 lap0 lap1
1613 ;; The stack depth gets locally increased, so we will
1614 ;; increase maxdepth in case depth = maxdepth here.
1615 ;; This can cause the third argument to byte-code to
1616 ;; be larger than necessary.
1618 ;;
1619 ;; dup varset-X discard --> varset-X
1620 ;; dup varbind-X discard --> varbind-X
1621 ;; (the varbind variant can emerge from other optimizations)
1622 ;;
1630 ;;
1631 ;; not goto-X-if-nil --> goto-X-if-non-nil
1632 ;; not goto-X-if-non-nil --> goto-X-if-nil
1633 ;;
1634 ;; it is wrong to do the same thing for the -else-pop variants.
1635 ;;
1640 lap1
1643 'byte-goto-if-not-nil
1647 'byte-goto-if-not-nil
1651 ;;
1652 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1653 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1654 ;;
1655 ;; it is wrong to do the same thing for the -else-pop variants.
1656 ;;
1664 lap0 lap1 lap2
1669 ;;
1670 ;; const goto-if-* --> whatever
1671 ;;
1679 lap0 lap1)
1692 ;;
1693 ;; varref-X varref-X --> varref-X dup
1694 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1695 ;; We don't optimize the const-X variations on this here,
1696 ;; because that would inhibit some goto optimizations; we
1697 ;; optimize the const-X case after all other optimizations.
1698 ;;
1704 t)
1714 lap0 str lap0 lap0 str)))
1719 ;;
1720 ;; TAG1: TAG2: --> TAG1: <deleted>
1721 ;; (and other references to TAG2 are replaced with TAG1)
1722 ;;
1733 keep-going t))
1734 ;;
1735 ;; unused-TAG: --> <deleted>
1736 ;;
1742 keep-going t))
1743 ;;
1744 ;; goto ... --> goto <delete until TAG or end>
1745 ;; return ... --> return <delete until TAG or end>
1746 ;;
1752 str deleted)
1767 lap0
1773 tagstr lap0 tagstr))))
1776 ;;
1777 ;; <safe-op> unbind --> unbind <safe-op>
1778 ;; (this may enable other optimizations.)
1779 ;;
1786 ;;
1787 ;; varbind-X unbind-N --> discard unbind-(N-1)
1788 ;; save-excursion unbind-N --> unbind-(N-1)
1789 ;; save-restriction unbind-N --> unbind-(N-1)
1790 ;;
1793 byte-save-restriction))
1810 ;;
1811 ;; goto*-X ... X: goto-Y --> goto*-Y
1812 ;; goto-X ... X: return --> return
1813 ;;
1826 ;;
1827 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1828 ;; goto-*-else-pop X ... X: discard --> whatever
1829 ;;
1831 byte-goto-if-not-nil-else-pop))
1838 byte-goto-if-nil)
1840 byte-goto-if-not-nil))))
1846 ;; Get rid of the -else-pop's and jump one step further.
1855 ;;
1856 ;; const goto-X ... X: goto-if-* --> whatever
1857 ;; const goto-X ... X: discard --> whatever
1858 ;;
1870 byte-goto-if-not-nil-else-pop)))
1872 lap0 tmp2 lap0 tmp2)
1875 ;; Let next step fix the (const,goto-if*) sequence.
1878 ;; Jump one step further
1881 lap0 tmp2)
1888 ;;
1889 ;; X: varref-Y ... varset-Y goto-X -->
1890 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1891 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1892 ;; (This is so usual for while loops that it is worth handling).
1893 ;;
1901 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1906 lap1 lap2
1910 )
1915 ;;
1916 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1917 ;; (This can pull the loop test to the end of the loop)
1918 ;;
1925 byte-goto-if-nil-else-pop)))
1926 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1927 ;; lap0 lap1 (cdr lap0) (car tmp))
1936 byte-goto-if-not-nil-else-pop)
1938 byte-goto-if-nil-else-pop))))
1939 newtag)
1942 )
1945 ;; We can handle this case but not the -if-not-nil case,
1946 ;; because we won't know which non-nil constant to push.
1952 byte-goto-if-not-nil
1953 byte-goto-if-nil
1954 byte-goto-if-not-nil
1955 byte-goto byte-goto))))
1956 )
1958 )
1960 )
1961 ;; Cleanup stage:
1962 ;; Rebuild byte-compile-constants / byte-compile-variables.
1963 ;; Simple optimizations that would inhibit other optimizations if they
1964 ;; were done in the optimizing loop, and optimizations which there is no
1965 ;; need to do more than once.
1967 byte-compile-variables nil)
1977 byte-compile-constants)))
1980 byte-compile-variables)))))
1982 ;; const-C varset-X const-C --> const-C dup varset-X
1983 ;; const-C varbind-X const-C --> const-C dup varbind-X
1984 ;;
1990 lap0 lap1 lap0 lap0 lap1)
1994 ;;
1995 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1996 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1997 ;;
2000 tmp2 nil)
2010 ;;
2011 ;; unbind-N unbind-M --> unbind-(N+M)
2012 ;;
2021 )
2024 lap)
2028 \f
2029 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2030 ;; itself, compile some of its most used recursive functions (at load time).
2031 ;;
2042 byte-optimize-body
2043 byte-optimize-predicate
2044 byte-optimize-binary-predicate
2045 ;; Inserted some more than necessary, to speed it up.
2046 byte-optimize-form-code-walker
2047 byte-optimize-lapcode))))
2048 nil)
2050 ;; arch-tag: 0f14076b-737e-4bef-aae6-908826ec1ff1
2051 ;;; byte-opt.el ends here