| blob | d4c21e5ddb85be13b3531eba59167ef88ed401a4 |
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:
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
279 ;; `byte-compile-splice-in-already-compiled-code'
280 ;; takes care of inlining the body.
286 ;; Give up on inlining.
287 form))))))
289 ;; ((lambda ...) ...)
300 optionalp restp
301 bindings)
308 ;; ok, I'll let this slide because funcall_lambda() does...
309 ;; (if optionalp (error "multiple &optional keywords in %s" name))
315 ;; ...but it is by no stretch of the imagination a reasonable
316 ;; thing that funcall_lambda() allows (&rest x y) and
317 ;; (&rest x &optional y) in arglists.
326 bindings)
327 values nil))
333 bindings)
341 form)
343 ;; The following leads to infinite recursion when loading a
344 ;; file containing `(defsubst f () (f))', and then trying to
345 ;; byte-compile that file.
346 ;(setq body (mapcar 'byte-optimize-form body)))
353 newform)))))
355 \f
356 ;;; implementing source-level optimizers
359 ;;
360 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
361 ;; we need to have special knowledge of the syntax of the special forms
362 ;; like let and defun (that's why they're special forms :-). (Actually,
363 ;; the important aspect is that they are subrs that don't evaluate all of
364 ;; their args.)
365 ;;
367 tmp)
373 form))
378 ;; map (quote nil) to nil to simplify optimizer logic.
379 ;; map quoted constants to nil if for-effect (just because).
382 form))
387 ;; recursively enter the optimizer for the bindings and body
388 ;; of a let or let*. This for depth-firstness: forms that
389 ;; are more deeply nested are optimized first.
394 binding
411 clause))
414 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
433 ;; those subrs which have an implicit progn; it's not quite good
434 ;; enough to treat these like normal function calls.
435 ;; This can turn (save-excursion ...) into (save-excursion) which
436 ;; will be optimized away in the lap-optimize pass.
440 ;; this is just like the above, except for the first argument.
456 ;; take forms off the back until we can't any more.
457 ;; In the future it could conceivably be a problem that the
458 ;; subexpressions of these forms are optimized in the reverse
459 ;; order, but it's ok for now.
465 for-effect))))
477 nil)
480 condition-case save-window-excursion))
481 ;; These forms are compiled as constants or by breaking out
482 ;; all the subexpressions and compiling them separately.
483 form)
486 ;; the "protected" part of an unwind-protect is compiled (and thus
487 ;; optimized) as a top-level form, so don't do it here. But the
488 ;; non-protected part has the same for-effect status as the
489 ;; unwind-protect itself. (The protected part is always for effect,
490 ;; but that isn't handled properly yet.)
496 ;; the body of a catch is compiled (and thus optimized) as a
497 ;; top-level form, so don't do it here. The tag is never
498 ;; for-effect. The body should have the same for-effect status
499 ;; as the catch form itself, but that isn't handled properly yet.
505 ;; Don't treat the args to `ignore' as being
506 ;; computed for effect. We want to avoid the warnings
507 ;; that might occur if they were treated that way.
508 ;; However, don't actually bother calling `ignore'.
511 ;; If optimization is on, this is the only place that macros are
512 ;; expanded. If optimization is off, then macroexpansion happens
513 ;; in byte-compile-form. Otherwise, the macros are already expanded
514 ;; by the time that is reached.
517 byte-compile-macro-environment))))
520 ;; Support compiler macros as in cl.el.
532 form)
537 ;; Detect the expansion of (pop foo).
538 ;; There is no need to compile the call to `car' there.
552 nil)))
554 ;; appending a nil here might not be necessary, but it can't hurt.
559 ;; Otherwise, no args can be considered to be for-effect,
560 ;; even if the called function is for-effect, because we
561 ;; don't know anything about that function.
569 "Non-nil if all elements of LIST satisfy `byte-compile-constp'."
575 constant))
578 "The source-level pass of the optimizer."
579 ;;
580 ;; First, optimize all sub-forms of this one.
582 ;;
583 ;; after optimizing all subforms, optimize this form until it doesn't
584 ;; optimize any further. This means that some forms will be passed through
585 ;; the optimizer many times, but that's necessary to make the for-effect
586 ;; processing do as much as possible.
587 ;;
592 ;; we don't have any of these yet, but we might.
597 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
600 new)
601 form)))
605 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
606 ;; forms, all but the last of which are optimized with the assumption that
607 ;; they are being called for effect. the last is for-effect as well if
608 ;; all-for-effect is true. returns a new list of forms.
611 fe new)
620 \f
621 ;; some source-level optimizers
622 ;;
623 ;; when writing optimizers, be VERY careful that the optimizer returns
624 ;; something not EQ to its argument if and ONLY if it has made a change.
625 ;; This implies that you cannot simply destructively modify the list;
626 ;; you must return something not EQ to it if you make an optimization.
627 ;;
628 ;; It is now safe to optimize code such that it introduces new bindings.
630 ;; I'd like this to be a defsubst, but let's not be self-referential...
632 ;; Returns non-nil if FORM is a non-nil constant.
638 ;; If the function is being called with constant numeric args,
639 ;; evaluate as much as possible at compile-time. This optimizer
640 ;; assumes that the function is associative, like + or *.
658 form)))
660 ;; If the function is being called with constant numeric args,
661 ;; evaluate as much as possible at compile-time. This optimizer
662 ;; assumes that the function satisfies
663 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
664 ;; like - and /.
668 form
676 constant))))
678 ;;(defun byte-optimize-associative-two-args-math (form)
679 ;; (setq form (byte-optimize-associative-math form))
680 ;; (if (consp form)
681 ;; (byte-optimize-two-args-left form)
682 ;; form))
684 ;;(defun byte-optimize-nonassociative-two-args-math (form)
685 ;; (setq form (byte-optimize-nonassociative-math form))
686 ;; (if (consp form)
687 ;; (byte-optimize-two-args-right form)
688 ;; form))
693 ;; Collect all the constants from FORM, after the STARTth arg,
694 ;; and apply FUN to them to make one argument at the end.
695 ;; For functions that can handle floats, that optimization
696 ;; can be incorrect because reordering can cause an overflow
697 ;; that would otherwise be avoided by encountering an arg that is a float.
698 ;; We avoid this problem by (1) not moving float constants and
699 ;; (2) not moving anything if it would cause an overflow.
701 ;; Merge all FORM's constants from number START, call FUN on them
702 ;; and put the result at the end.
705 ;; t means we must check for overflow.
716 ;; If necessary, check now for overflow
717 ;; that might be caused by reordering.
719 ;; We have overflow if the result of doing the arithmetic
720 ;; on floats is not even close to the result
721 ;; of doing it on integers.
728 form))
733 ;;(setq form (byte-optimize-associative-two-args-math form))
738 ;;; It is not safe to delete the function entirely
739 ;;; (actually, it would be safe if we know the sole arg
740 ;;; is not a marker).
741 ;;; ((null (cdr (cdr form))) (nth 1 form))
745 form))
749 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
759 other)))
763 ;; Put constants at the end, except the last constant.
765 ;; Now only first and last element can be a number.
768 ;; (- x y ... 0) --> (- x y ...)
775 ;; If form is (- CONST foo... CONST), merge first and last.
780 ;;; It is not safe to delete the function entirely
781 ;;; (actually, it would be safe if we know the sole arg
782 ;;; is not a marker).
783 ;;; (if (eq (nth 2 form) 0)
784 ;;; (nth 1 form) ; (- x 0) --> x
789 form))
790 ;;; )
791 )
795 ;; If there is a constant in FORM, it is now the last element.
797 ;;; It is not safe to delete the function entirely
798 ;;; (actually, it would be safe if we know the sole arg
799 ;;; is not a marker or if it appears in other arithmetic).
800 ;;; ((null (cdr (cdr form))) (nth 1 form))
832 last nil))))
834 ;;; ((null (cdr (cdr form)))
835 ;;; (nth 1 form))
863 ;; This can enable some lapcode optimizations.
865 form))
877 form)))
885 form))
929 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
930 ;; take care of this? - Jamie
931 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
932 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
938 form
951 ;; Simplify if less than 2 args.
952 ;; if there is a literal nil in the args to `and', throw it and following
953 ;; forms away, and surround the `and' with (progn ... nil).
962 nil))
968 ;; Throw away nil's, and simplify if less than 2 args.
969 ;; If there is a literal non-nil constant in the args to `or', throw away all
970 ;; following forms.
983 ;; if any clauses have a literal nil as their test, throw them away.
984 ;; if any clause has a literal non-nil constant as its test, throw
985 ;; away all following clauses.
987 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
1006 ;;
1007 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1015 form))
1016 form))
1019 ;; (if <true-constant> <then> <else...>) ==> <then>
1020 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1021 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1022 ;; (if <test> <then> nil) ==> (if <test> <then>)
1033 form))
1036 ;; Don't make a double negative;
1037 ;; instead, take away the one that is there.
1052 form))
1060 ;; byte-compile-negation-optimizer lives in bytecomp.el
1067 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1068 ;; (funcall foo ...) ==> (foo ...)
1072 form)))
1075 ;; If the last arg is a literal constant, turn this into a funcall.
1076 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1086 "last arg to apply can't be a literal atom: `%s'"
1088 nil))
1089 form)))
1099 ;; No bindings
1102 form)
1103 ;; The body is nil
1120 form))
1130 form)
1132 form))
1134 ;; Fixme: delete-char -> delete-region (byte-coded)
1135 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1136 ;; string-make-multibyte for constant args.
1140 ;; Emacs-21's byte-code doesn't run under XEmacs or SXEmacs anyway, so we
1141 ;; can safely optimize away this test.
1143 nil
1144 form))
1157 \f
1158 ;; enumerating those functions which need not be called if the returned
1159 ;; value is not used. That is, something like
1160 ;; (progn (list (something-with-side-effects) (yow))
1161 ;; (foo))
1162 ;; may safely be turned into
1163 ;; (progn (progn (something-with-side-effects) (yow))
1164 ;; (foo))
1165 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1167 ;; Some of these functions have the side effect of allocating memory
1168 ;; and it would be incorrect to replace two calls with one.
1169 ;; But we don't try to do those kinds of optimizations,
1170 ;; so it is safe to list such functions here.
1171 ;; Some of these functions return values that depend on environment
1172 ;; state, so that constant folding them would be wrong,
1173 ;; but we don't do constant folding based on this list.
1175 ;; However, at present the only optimization we normally do
1176 ;; is delete calls that need not occur, and we only do that
1177 ;; with the error-free functions.
1179 ;; I wonder if I missed any :-\)
1182 assoc assq
1183 boundp buffer-file-name buffer-local-variables buffer-modified-p
1184 buffer-substring byte-code-function-p
1185 capitalize car-less-than-car car cdr ceiling char-after char-before
1186 char-equal char-to-string char-width
1187 compare-strings concat coordinates-in-window-p
1188 copy-alist copy-sequence copy-marker cos count-lines
1189 decode-time default-boundp default-value documentation downcase
1190 elt exp expt encode-time error-message-string
1191 fboundp fceiling featurep ffloor
1192 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1193 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1194 float float-time floor format format-time-string frame-visible-p
1195 fround ftruncate
1196 get gethash get-buffer get-buffer-window getenv get-file-buffer
1197 hash-table-count
1198 int-to-string intern-soft
1199 keymap-parent
1200 length local-variable-if-set-p local-variable-p log log10 logand
1201 logb logior lognot logxor lsh
1202 make-list make-string make-symbol
1203 marker-buffer max member memq min mod multibyte-char-to-unibyte
1204 next-window nth nthcdr number-to-string
1205 parse-colon-path plist-get plist-member
1206 prefix-numeric-value previous-window prin1-to-string propertize
1207 radians-to-degrees rassq rassoc read-from-string regexp-quote
1208 region-beginning region-end reverse round
1210 string-to-int string-to-number substring sxhash symbol-function
1211 symbol-name symbol-plist symbol-value string-make-unibyte
1212 string-make-multibyte string-as-multibyte string-as-unibyte
1213 tan truncate
1214 unibyte-char-to-multibyte upcase user-full-name
1215 user-login-name user-original-login-name user-variable-p
1216 vconcat
1217 window-buffer window-dedicated-p window-edges window-height
1218 window-hscroll window-minibuffer-p window-width
1219 zerop))
1222 bobp bolp bool-vector-p
1223 buffer-end buffer-list buffer-size buffer-string bufferp
1224 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1225 current-buffer current-global-map current-indentation
1226 current-local-map current-minor-mode-maps current-time
1227 current-time-string current-time-zone
1228 eobp eolp eq equal eventp
1229 floatp following-char framep
1230 get-largest-window get-lru-window
1231 hash-table-p
1232 identity ignore integerp integer-or-marker-p interactive-p
1233 invocation-directory invocation-name
1234 keymapp
1235 line-beginning-position line-end-position list listp
1236 make-marker mark mark-marker markerp memory-limit minibuffer-window
1237 mouse-movement-p
1238 natnump nlistp not null number-or-marker-p numberp
1239 one-window-p overlayp
1240 point point-marker point-min point-max preceding-char processp
1241 recent-keys recursion-depth
1242 safe-length selected-frame selected-window sequencep
1243 standard-case-table standard-syntax-table stringp subrp symbolp
1244 syntax-table syntax-table-p
1245 this-command-keys this-command-keys-vector this-single-command-keys
1246 this-single-command-raw-keys
1247 user-real-login-name user-real-uid user-uid
1248 vector vectorp visible-frame-list
1249 wholenump window-configuration-p window-live-p windowp)))
1256 nil)
1258 \f
1259 ;; pure functions are side-effect free functions whose values depend
1260 ;; only on their arguments. For these functions, calls with constant
1261 ;; arguments can be evaluated at compile time. This may shift run time
1262 ;; errors to compile time.
1269 nil)
1272 ;; form is (byte-code "..." [...] n)
1278 byte-compile-maxdepth))
1283 \f
1287 ;; This function extracts the bitfields from variable-length opcodes.
1288 ;; Originally defined in disass.el (which no longer uses it.)
1291 "Don't call this!"
1292 ;; fetch and return the offset for the current opcode.
1293 ;; return nil if this opcode has no offset
1294 ;; OP, PTR and BYTES are used and set dynamically
1325 ;; This de-compiler is used for inline expansion of compiled functions,
1326 ;; and by the disassembler.
1327 ;;
1328 ;; This list contains numbers, which are pc values,
1329 ;; before each instruction.
1331 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1337 ;; As byte-decompile-bytecode, but updates
1338 ;; byte-compile-{constants, variables, tag-number}.
1339 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1340 ;; with `goto's destined for the end of the code.
1341 ;; That is for use by the compiler.
1342 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1343 ;; In that case, we put a pc value into the list
1344 ;; before each insn (or its label).
1348 lap tmp
1349 endtag)
1354 optr ptr
1358 ;; it's a pc
1364 tags)))))))
1375 byte-compile-variables)))))))
1382 ;; lap = ( [ (pc . (op . arg)) ]* )
1384 lap))
1386 ;; take off the dummy nil op that we replaced a trailing "return" with.
1391 ;; this addr is jumped to
1402 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1405 elt
1409 \f
1410 ;;; peephole optimizer
1416 byte-goto-if-not-nil-else-pop))
1420 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1421 byte-eq byte-not
1422 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1423 byte-interactive-p)
1424 ;; How about other side-effect-free-ops? Is it safe to move an
1425 ;; error invocation (such as from nth) out of an unwind-protect?
1426 ;; No, it is not, because the unwind-protect forms can alter
1427 ;; the inside of the object to which nth would apply.
1428 ;; For the same reason, byte-equal was deleted from this list.
1433 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1434 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1435 byte-point-min byte-following-char byte-preceding-char
1436 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1437 byte-current-buffer byte-interactive-p))
1442 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1443 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1444 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1446 byte-member byte-assq byte-quo byte-rem)
1447 byte-compile-side-effect-and-error-free-ops))
1449 ;; This crock is because of the way DEFVAR_BOOL variables work.
1450 ;; Consider the code
1451 ;;
1452 ;; (defun foo (flag)
1453 ;; (let ((old-pop-ups pop-up-windows)
1454 ;; (pop-up-windows flag))
1455 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1456 ;; (setq old-pop-ups pop-up-windows)
1457 ;; ...))))
1458 ;;
1459 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1460 ;; something else. But if we optimize
1461 ;;
1462 ;; varref flag
1463 ;; varbind pop-up-windows
1464 ;; varref pop-up-windows
1465 ;; not
1466 ;; to
1467 ;; varref flag
1468 ;; dup
1469 ;; varbind pop-up-windows
1470 ;; not
1471 ;;
1472 ;; we break the program, because it will appear that pop-up-windows and
1473 ;; old-pop-ups are not EQ when really they are. So we have to know what
1474 ;; the BOOL variables are, and not perform this optimization on them.
1476 ;; The variable `byte-boolean-vars' is now primitive and updated
1477 ;; automatically by DEFVAR_BOOL.
1480 "Simple peephole optimizer. LAP is both modified and returned.
1481 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1483 lap1
1484 lap2
1487 rest tmp tmp2 tmp3
1489 byte-compile-side-effect-free-ops
1490 byte-compile-side-effect-and-error-free-ops)))
1495 keep-going nil)
1501 ;; You may notice that sequences like "dup varset discard" are
1502 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1503 ;; You may be tempted to change this; resist that temptation.
1505 ;; <side-effect-free> pop --> <deleted>
1506 ;; ...including:
1507 ;; const-X pop --> <deleted>
1508 ;; varref-X pop --> <deleted>
1509 ;; dup pop --> <deleted>
1510 ;;
1530 ;;
1531 ;; goto*-X X: --> X:
1532 ;;
1547 ;;
1548 ;; varset-X varref-X --> dup varset-X
1549 ;; varbind-X varref-X --> dup varbind-X
1550 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1551 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1552 ;; The latter two can enable other optimizations.
1553 ;;
1559 nil
1569 lap0 lap1 lap2 lap0 lap1
1577 ;; The stack depth gets locally increased, so we will
1578 ;; increase maxdepth in case depth = maxdepth here.
1579 ;; This can cause the third argument to byte-code to
1580 ;; be larger than necessary.
1582 ;;
1583 ;; dup varset-X discard --> varset-X
1584 ;; dup varbind-X discard --> varbind-X
1585 ;; (the varbind variant can emerge from other optimizations)
1586 ;;
1594 ;;
1595 ;; not goto-X-if-nil --> goto-X-if-non-nil
1596 ;; not goto-X-if-non-nil --> goto-X-if-nil
1597 ;;
1598 ;; it is wrong to do the same thing for the -else-pop variants.
1599 ;;
1604 lap1
1607 'byte-goto-if-not-nil
1611 'byte-goto-if-not-nil
1615 ;;
1616 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1617 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1618 ;;
1619 ;; it is wrong to do the same thing for the -else-pop variants.
1620 ;;
1628 lap0 lap1 lap2
1633 ;;
1634 ;; const goto-if-* --> whatever
1635 ;;
1643 lap0 lap1)
1656 ;;
1657 ;; varref-X varref-X --> varref-X dup
1658 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1659 ;; We don't optimize the const-X variations on this here,
1660 ;; because that would inhibit some goto optimizations; we
1661 ;; optimize the const-X case after all other optimizations.
1662 ;;
1668 t)
1678 lap0 str lap0 lap0 str)))
1683 ;;
1684 ;; TAG1: TAG2: --> TAG1: <deleted>
1685 ;; (and other references to TAG2 are replaced with TAG1)
1686 ;;
1697 keep-going t))
1698 ;;
1699 ;; unused-TAG: --> <deleted>
1700 ;;
1706 keep-going t))
1707 ;;
1708 ;; goto ... --> goto <delete until TAG or end>
1709 ;; return ... --> return <delete until TAG or end>
1710 ;;
1716 str deleted)
1731 lap0
1737 tagstr lap0 tagstr))))
1740 ;;
1741 ;; <safe-op> unbind --> unbind <safe-op>
1742 ;; (this may enable other optimizations.)
1743 ;;
1750 ;;
1751 ;; varbind-X unbind-N --> discard unbind-(N-1)
1752 ;; save-excursion unbind-N --> unbind-(N-1)
1753 ;; save-restriction unbind-N --> unbind-(N-1)
1754 ;;
1757 byte-save-restriction))
1774 ;;
1775 ;; goto*-X ... X: goto-Y --> goto*-Y
1776 ;; goto-X ... X: return --> return
1777 ;;
1790 ;;
1791 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1792 ;; goto-*-else-pop X ... X: discard --> whatever
1793 ;;
1795 byte-goto-if-not-nil-else-pop))
1802 byte-goto-if-nil)
1804 byte-goto-if-not-nil))))
1810 ;; Get rid of the -else-pop's and jump one step further.
1819 ;;
1820 ;; const goto-X ... X: goto-if-* --> whatever
1821 ;; const goto-X ... X: discard --> whatever
1822 ;;
1834 byte-goto-if-not-nil-else-pop)))
1836 lap0 tmp2 lap0 tmp2)
1839 ;; Let next step fix the (const,goto-if*) sequence.
1842 ;; Jump one step further
1845 lap0 tmp2)
1852 ;;
1853 ;; X: varref-Y ... varset-Y goto-X -->
1854 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1855 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1856 ;; (This is so usual for while loops that it is worth handling).
1857 ;;
1865 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1870 lap1 lap2
1874 )
1879 ;;
1880 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1881 ;; (This can pull the loop test to the end of the loop)
1882 ;;
1889 byte-goto-if-nil-else-pop)))
1890 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1891 ;; lap0 lap1 (cdr lap0) (car tmp))
1900 byte-goto-if-not-nil-else-pop)
1902 byte-goto-if-nil-else-pop))))
1903 newtag)
1906 )
1909 ;; We can handle this case but not the -if-not-nil case,
1910 ;; because we won't know which non-nil constant to push.
1916 byte-goto-if-not-nil
1917 byte-goto-if-nil
1918 byte-goto-if-not-nil
1919 byte-goto byte-goto))))
1920 )
1922 )
1924 )
1925 ;; Cleanup stage:
1926 ;; Rebuild byte-compile-constants / byte-compile-variables.
1927 ;; Simple optimizations that would inhibit other optimizations if they
1928 ;; were done in the optimizing loop, and optimizations which there is no
1929 ;; need to do more than once.
1931 byte-compile-variables nil)
1941 byte-compile-constants)))
1944 byte-compile-variables)))))
1946 ;; const-C varset-X const-C --> const-C dup varset-X
1947 ;; const-C varbind-X const-C --> const-C dup varbind-X
1948 ;;
1954 lap0 lap1 lap0 lap0 lap1)
1958 ;;
1959 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1960 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1961 ;;
1964 tmp2 nil)
1974 ;;
1975 ;; unbind-N unbind-M --> unbind-(N+M)
1976 ;;
1985 )
1988 lap)
1992 \f
1993 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
1994 ;; itself, compile some of its most used recursive functions (at load time).
1995 ;;
2006 byte-optimize-body
2007 byte-optimize-predicate
2008 byte-optimize-binary-predicate
2009 ;; Inserted some more than necessary, to speed it up.
2010 byte-optimize-form-code-walker
2011 byte-optimize-lapcode))))
2012 nil)
2014 ;; arch-tag: 0f14076b-737e-4bef-aae6-908826ec1ff1
2015 ;;; byte-opt.el ends here