| blob | c02e8b02dea904356fa7202b114099998c5746d9 |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler
3 ;;; Copyright (c) 1991, 1994, 2000, 2001, 2002 Free Software Foundation, Inc.
5 ;; Author: Jamie Zawinski <jwz@lucid.com>
6 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
7 ;; Maintainer: FSF
8 ;; Keywords: internal
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software; you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation; either version 2, or (at your option)
15 ;; any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs; see the file COPYING. If not, write to the
24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
25 ;; Boston, MA 02111-1307, USA.
27 ;;; Commentary:
29 ;; ========================================================================
30 ;; "No matter how hard you try, you can't make a racehorse out of a pig.
31 ;; You can, however, make a faster pig."
32 ;;
33 ;; Or, to put it another way, the emacs byte compiler is a VW Bug. This code
34 ;; makes it be a VW Bug with fuel injection and a turbocharger... You're
35 ;; still not going to make it go faster than 70 mph, but it might be easier
36 ;; to get it there.
37 ;;
39 ;; TO DO:
40 ;;
41 ;; (apply (lambda (x &rest y) ...) 1 (foo))
42 ;;
43 ;; maintain a list of functions known not to access any global variables
44 ;; (actually, give them a 'dynamically-safe property) and then
45 ;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
46 ;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
47 ;; by recursing on this, we might be able to eliminate the entire let.
48 ;; However certain variables should never have their bindings optimized
49 ;; away, because they affect everything.
50 ;; (put 'debug-on-error 'binding-is-magic t)
51 ;; (put 'debug-on-abort 'binding-is-magic t)
52 ;; (put 'debug-on-next-call 'binding-is-magic t)
53 ;; (put 'inhibit-quit 'binding-is-magic t)
54 ;; (put 'quit-flag 'binding-is-magic t)
55 ;; (put 't 'binding-is-magic t)
56 ;; (put 'nil 'binding-is-magic t)
57 ;; possibly also
58 ;; (put 'gc-cons-threshold 'binding-is-magic t)
59 ;; (put 'track-mouse 'binding-is-magic t)
60 ;; others?
61 ;;
62 ;; Simple defsubsts often produce forms like
63 ;; (let ((v1 (f1)) (v2 (f2)) ...)
64 ;; (FN v1 v2 ...))
65 ;; It would be nice if we could optimize this to
66 ;; (FN (f1) (f2) ...)
67 ;; but we can't unless FN is dynamically-safe (it might be dynamically
68 ;; referring to the bindings that the lambda arglist established.)
69 ;; One of the uncountable lossages introduced by dynamic scope...
70 ;;
71 ;; Maybe there should be a control-structure that says "turn on
72 ;; fast-and-loose type-assumptive optimizations here." Then when
73 ;; we see a form like (car foo) we can from then on assume that
74 ;; the variable foo is of type cons, and optimize based on that.
75 ;; But, this won't win much because of (you guessed it) dynamic
76 ;; scope. Anything down the stack could change the value.
77 ;; (Another reason it doesn't work is that it is perfectly valid
78 ;; to call car with a null argument.) A better approach might
79 ;; be to allow type-specification of the form
80 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
81 ;; (put 'foo 'result-type 'bool)
82 ;; It should be possible to have these types checked to a certain
83 ;; degree.
84 ;;
85 ;; collapse common subexpressions
86 ;;
87 ;; It would be nice if redundant sequences could be factored out as well,
88 ;; when they are known to have no side-effects:
89 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
90 ;; but beware of traps like
91 ;; (cons (list x y) (list x y))
92 ;;
93 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
94 ;; Tail-recursion elimination is almost always impossible when all variables
95 ;; have dynamic scope, but given that the "return" byteop requires the
96 ;; binding stack to be empty (rather than emptying it itself), there can be
97 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
98 ;; make any bindings.
99 ;;
100 ;; Here is an example of an Emacs Lisp function which could safely be
101 ;; byte-compiled tail-recursively:
102 ;;
103 ;; (defun tail-map (fn list)
104 ;; (cond (list
105 ;; (funcall fn (car list))
106 ;; (tail-map fn (cdr list)))))
107 ;;
108 ;; However, if there was even a single let-binding around the COND,
109 ;; it could not be byte-compiled, because there would be an "unbind"
110 ;; byte-op between the final "call" and "return." Adding a
111 ;; Bunbind_all byteop would fix this.
112 ;;
113 ;; (defun foo (x y z) ... (foo a b c))
114 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
115 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
116 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
117 ;;
118 ;; this also can be considered tail recursion:
119 ;;
120 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
121 ;; could generalize this by doing the optimization
122 ;; (goto X) ... X: (return) --> (return)
123 ;;
124 ;; But this doesn't solve all of the problems: although by doing tail-
125 ;; recursion elimination in this way, the call-stack does not grow, the
126 ;; binding-stack would grow with each recursive step, and would eventually
127 ;; overflow. I don't believe there is any way around this without lexical
128 ;; scope.
129 ;;
130 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
131 ;;
132 ;; Idea: the form (lexical-scope) in a file means that the file may be
133 ;; compiled lexically. This proclamation is file-local. Then, within
134 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
135 ;; would do things the old way. (Or we could use CL "declare" forms.)
136 ;; We'd have to notice defvars and defconsts, since those variables should
137 ;; always be dynamic, and attempting to do a lexical binding of them
138 ;; should simply do a dynamic binding instead.
139 ;; But! We need to know about variables that were not necessarily defvarred
140 ;; in the file being compiled (doing a boundp check isn't good enough.)
141 ;; Fdefvar() would have to be modified to add something to the plist.
142 ;;
143 ;; A major disadvantage of this scheme is that the interpreter and compiler
144 ;; would have different semantics for files compiled with (dynamic-scope).
145 ;; Since this would be a file-local optimization, there would be no way to
146 ;; modify the interpreter to obey this (unless the loader was hacked
147 ;; in some grody way, but that's a really bad idea.)
149 ;; Other things to consider:
151 ;;;;; Associative math should recognize subcalls to identical function:
152 ;;;(disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
153 ;;;;; This should generate the same as (1+ x) and (1- x)
155 ;;;(disassemble (lambda (x) (cons (+ x 1) (- x 1))))
156 ;;;;; An awful lot of functions always return a non-nil value. If they're
157 ;;;;; error free also they may act as true-constants.
159 ;;;(disassemble (lambda (x) (and (point) (foo))))
160 ;;;;; When
161 ;;;;; - all but one arguments to a function are constant
162 ;;;;; - the non-constant argument is an if-expression (cond-expression?)
163 ;;;;; then the outer function can be distributed. If the guarding
164 ;;;;; condition is side-effect-free [assignment-free] then the other
165 ;;;;; arguments may be any expressions. Since, however, the code size
166 ;;;;; can increase this way they should be "simple". Compare:
168 ;;;(disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
169 ;;;(disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
171 ;;;;; (car (cons A B)) -> (progn B A)
172 ;;;(disassemble (lambda (x) (car (cons (foo) 42))))
174 ;;;;; (cdr (cons A B)) -> (progn A B)
175 ;;;(disassemble (lambda (x) (cdr (cons 42 (foo)))))
177 ;;;;; (car (list A B ...)) -> (progn B ... A)
178 ;;;(disassemble (lambda (x) (car (list (foo) 42 (bar)))))
180 ;;;;; (cdr (list A B ...)) -> (progn A (list B ...))
181 ;;;(disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
184 ;;; Code:
199 arg)
215 c
217 args)))))
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
284 ;; Give up on inlining.
285 form))))))
287 ;;; ((lambda ...) ...)
288 ;;;
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 ;; recursively enter the optimizer for the bindings and body
387 ;; of a let or let*. This for depth-firstness: forms that
388 ;; are more deeply nested are optimized first.
393 binding
410 clause))
413 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
432 ;; those subrs which have an implicit progn; it's not quite good
433 ;; enough to treat these like normal function calls.
434 ;; This can turn (save-excursion ...) into (save-excursion) which
435 ;; will be optimized away in the lap-optimize pass.
439 ;; this is just like the above, except for the first argument.
455 ;; take forms off the back until we can't any more.
456 ;; In the future it could conceivably be a problem that the
457 ;; subexpressions of these forms are optimized in the reverse
458 ;; order, but it's ok for now.
464 for-effect))))
476 nil)
479 condition-case save-window-excursion))
480 ;; These forms are compiled as constants or by breaking out
481 ;; all the subexpressions and compiling them separately.
482 form)
485 ;; the "protected" part of an unwind-protect is compiled (and thus
486 ;; optimized) as a top-level form, so don't do it here. But the
487 ;; non-protected part has the same for-effect status as the
488 ;; unwind-protect itself. (The protected part is always for effect,
489 ;; but that isn't handled properly yet.)
495 ;; the body of a catch is compiled (and thus optimized) as a
496 ;; top-level form, so don't do it here. The tag is never
497 ;; for-effect. The body should have the same for-effect status
498 ;; as the catch form itself, but that isn't handled properly yet.
504 ;; Don't treat the args to `ignore' as being
505 ;; computed for effect. We want to avoid the warnings
506 ;; that might occur if they were treated that way.
507 ;; However, don't actually bother calling `ignore'.
510 ;; If optimization is on, this is the only place that macros are
511 ;; expanded. If optimization is off, then macroexpansion happens
512 ;; in byte-compile-form. Otherwise, the macros are already expanded
513 ;; by the time that is reached.
516 byte-compile-macro-environment))))
519 ;; Support compiler macros as in cl.el.
530 form)
535 ;; Detect the expansion of (pop foo).
536 ;; There is no need to compile the call to `car' there.
550 nil)))
552 ;; appending a nil here might not be necessary, but it can't hurt.
557 ;; Otherwise, no args can be considered to be for-effect,
558 ;; even if the called function is for-effect, because we
559 ;; don't know anything about that function.
564 "The source-level pass of the optimizer."
565 ;;
566 ;; First, optimize all sub-forms of this one.
568 ;;
569 ;; after optimizing all subforms, optimize this form until it doesn't
570 ;; optimize any further. This means that some forms will be passed through
571 ;; the optimizer many times, but that's necessary to make the for-effect
572 ;; processing do as much as possible.
573 ;;
578 ;; we don't have any of these yet, but we might.
583 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
586 new)
587 form)))
591 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
592 ;; forms, all but the last of which are optimized with the assumption that
593 ;; they are being called for effect. the last is for-effect as well if
594 ;; all-for-effect is true. returns a new list of forms.
597 fe new)
606 \f
607 ;;; some source-level optimizers
608 ;;;
609 ;;; when writing optimizers, be VERY careful that the optimizer returns
610 ;;; something not EQ to its argument if and ONLY if it has made a change.
611 ;;; This implies that you cannot simply destructively modify the list;
612 ;;; you must return something not EQ to it if you make an optimization.
613 ;;;
614 ;;; It is now safe to optimize code such that it introduces new bindings.
616 ;; I'd like this to be a defsubst, but let's not be self-referential...
618 ;; Returns non-nil if FORM is a non-nil constant.
624 ;; If the function is being called with constant numeric args,
625 ;; evaluate as much as possible at compile-time. This optimizer
626 ;; assumes that the function is associative, like + or *.
644 form)))
646 ;; If the function is being called with constant numeric args,
647 ;; evaluate as much as possible at compile-time. This optimizer
648 ;; assumes that the function satisfies
649 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
650 ;; like - and /.
654 form
662 constant))))
664 ;;(defun byte-optimize-associative-two-args-math (form)
665 ;; (setq form (byte-optimize-associative-math form))
666 ;; (if (consp form)
667 ;; (byte-optimize-two-args-left form)
668 ;; form))
670 ;;(defun byte-optimize-nonassociative-two-args-math (form)
671 ;; (setq form (byte-optimize-nonassociative-math form))
672 ;; (if (consp form)
673 ;; (byte-optimize-two-args-right form)
674 ;; form))
679 ;; Collect all the constants from FORM, after the STARTth arg,
680 ;; and apply FUN to them to make one argument at the end.
681 ;; For functions that can handle floats, that optimization
682 ;; can be incorrect because reordering can cause an overflow
683 ;; that would otherwise be avoided by encountering an arg that is a float.
684 ;; We avoid this problem by (1) not moving float constants and
685 ;; (2) not moving anything if it would cause an overflow.
687 ;; Merge all FORM's constants from number START, call FUN on them
688 ;; and put the result at the end.
691 ;; t means we must check for overflow.
702 ;; If necessary, check now for overflow
703 ;; that might be caused by reordering.
705 ;; We have overflow if the result of doing the arithmetic
706 ;; on floats is not even close to the result
707 ;; of doing it on integers.
714 form))
719 ;;(setq form (byte-optimize-associative-two-args-math form))
724 ;;; It is not safe to delete the function entirely
725 ;;; (actually, it would be safe if we know the sole arg
726 ;;; is not a marker).
727 ;; ((null (cdr (cdr form))) (nth 1 form))
731 form))
735 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
745 other)))
749 ;; Put constants at the end, except the last constant.
751 ;; Now only first and last element can be a number.
754 ;; (- x y ... 0) --> (- x y ...)
761 ;; If form is (- CONST foo... CONST), merge first and last.
766 ;;; It is not safe to delete the function entirely
767 ;;; (actually, it would be safe if we know the sole arg
768 ;;; is not a marker).
769 ;;; (if (eq (nth 2 form) 0)
770 ;;; (nth 1 form) ; (- x 0) --> x
775 form))
776 ;;; )
777 )
781 ;; If there is a constant in FORM, it is now the last element.
783 ;;; It is not safe to delete the function entirely
784 ;;; (actually, it would be safe if we know the sole arg
785 ;;; is not a marker or if it appears in other arithmetic).
786 ;;; ((null (cdr (cdr form))) (nth 1 form))
818 last nil))))
820 ;;; ((null (cdr (cdr form)))
821 ;;; (nth 1 form))
849 ;; This can enable some lapcode optimizations.
851 form))
863 form)))
871 form))
915 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
916 ;; take care of this? - Jamie
917 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
918 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
924 form
937 ;; Simplify if less than 2 args.
938 ;; if there is a literal nil in the args to `and', throw it and following
939 ;; forms away, and surround the `and' with (progn ... nil).
948 nil))
954 ;; Throw away nil's, and simplify if less than 2 args.
955 ;; If there is a literal non-nil constant in the args to `or', throw away all
956 ;; following forms.
969 ;; if any clauses have a literal nil as their test, throw them away.
970 ;; if any clause has a literal non-nil constant as its test, throw
971 ;; away all following clauses.
973 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
992 ;;
993 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1001 form))
1002 form))
1005 ;; (if <true-constant> <then> <else...>) ==> <then>
1006 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1007 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1008 ;; (if <test> <then> nil) ==> (if <test> <then>)
1019 form))
1022 ;; Don't make a double negative;
1023 ;; instead, take away the one that is there.
1038 form))
1046 ;; byte-compile-negation-optimizer lives in bytecomp.el
1053 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1054 ;; (funcall foo ...) ==> (foo ...)
1058 form)))
1061 ;; If the last arg is a literal constant, turn this into a funcall.
1062 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1072 "last arg to apply can't be a literal atom: `%s'"
1074 nil))
1075 form)))
1085 ;; No bindings
1088 form)
1089 ;; The body is nil
1106 form))
1116 form)
1118 form))
1130 form)))
1132 ;; Avoid having to write forward-... with a negative arg for speed.
1133 ;; Fixme: don't be limited to constant args.
1160 ;; Fixme: delete-char -> delete-region (byte-coded)
1161 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1162 ;; string-make-multibyte for constant args.
1166 ;; Emacs-21's byte-code doesn't run under XEmacs anyway, so we can
1167 ;; safely optimize away this test.
1169 nil
1170 form))
1183 \f
1184 ;;; enumerating those functions which need not be called if the returned
1185 ;;; value is not used. That is, something like
1186 ;;; (progn (list (something-with-side-effects) (yow))
1187 ;;; (foo))
1188 ;;; may safely be turned into
1189 ;;; (progn (progn (something-with-side-effects) (yow))
1190 ;;; (foo))
1191 ;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1193 ;;; Some of these functions have the side effect of allocating memory
1194 ;;; and it would be incorrect to replace two calls with one.
1195 ;;; But we don't try to do those kinds of optimizations,
1196 ;;; so it is safe to list such functions here.
1197 ;;; Some of these functions return values that depend on environment
1198 ;;; state, so that constant folding them would be wrong,
1199 ;;; but we don't do constant folding based on this list.
1201 ;;; However, at present the only optimization we normally do
1202 ;;; is delete calls that need not occur, and we only do that
1203 ;;; with the error-free functions.
1205 ;;; I wonder if I missed any :-\)
1208 assoc assq
1209 boundp buffer-file-name buffer-local-variables buffer-modified-p
1210 buffer-substring byte-code-function-p
1211 capitalize car-less-than-car car cdr ceiling char-after char-before
1212 char-equal char-to-string char-width
1213 compare-strings concat coordinates-in-window-p
1214 copy-alist copy-sequence copy-marker cos count-lines
1215 decode-time default-boundp default-value documentation downcase
1216 elt exp expt encode-time error-message-string
1217 fboundp fceiling featurep ffloor
1218 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1219 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1220 float float-time floor format format-time-string frame-visible-p
1221 fround ftruncate
1222 get gethash get-buffer get-buffer-window getenv get-file-buffer
1223 hash-table-count
1224 int-to-string intern-soft
1225 keymap-parent
1226 length local-variable-if-set-p local-variable-p log log10 logand
1227 logb logior lognot logxor lsh
1228 make-list make-string make-symbol
1229 marker-buffer max member memq min mod multibyte-char-to-unibyte
1230 next-window nth nthcdr number-to-string
1231 parse-colon-path plist-get plist-member
1232 prefix-numeric-value previous-window prin1-to-string propertize
1233 radians-to-degrees rassq rassoc read-from-string regexp-quote
1234 region-beginning region-end reverse round
1236 string-to-int string-to-number substring sxhash symbol-function
1237 symbol-name symbol-plist symbol-value string-make-unibyte
1238 string-make-multibyte string-as-multibyte string-as-unibyte
1239 tan truncate
1240 unibyte-char-to-multibyte upcase user-full-name
1241 user-login-name user-original-login-name user-variable-p
1242 vconcat
1243 window-buffer window-dedicated-p window-edges window-height
1244 window-hscroll window-minibuffer-p window-width
1245 zerop))
1248 bobp bolp bool-vector-p
1249 buffer-end buffer-list buffer-size buffer-string bufferp
1250 car-safe case-table-p cdr-safe char-or-string-p 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 memory-limit minibuffer-window
1263 mouse-movement-p
1264 natnump nlistp not null number-or-marker-p numberp
1265 one-window-p overlayp
1266 point point-marker point-min point-max preceding-char processp
1267 recent-keys recursion-depth
1268 safe-length selected-frame selected-window sequencep
1269 standard-case-table standard-syntax-table stringp subrp symbolp
1270 syntax-table syntax-table-p
1271 this-command-keys this-command-keys-vector this-single-command-keys
1272 this-single-command-raw-keys
1273 user-real-login-name user-real-uid user-uid
1274 vector vectorp visible-frame-list
1275 wholenump window-configuration-p window-live-p windowp)))
1282 nil)
1286 ;; form is (byte-code "..." [...] n)
1292 byte-compile-maxdepth))
1297 \f
1301 ;;; This function extracts the bitfields from variable-length opcodes.
1302 ;;; Originally defined in disass.el (which no longer uses it.)
1305 "Don't call this!"
1306 ;; fetch and return the offset for the current opcode.
1307 ;; return nil if this opcode has no offset
1308 ;; OP, PTR and BYTES are used and set dynamically
1339 ;;; This de-compiler is used for inline expansion of compiled functions,
1340 ;;; and by the disassembler.
1341 ;;;
1342 ;;; This list contains numbers, which are pc values,
1343 ;;; before each instruction.
1345 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1351 ;; As byte-decompile-bytecode, but updates
1352 ;; byte-compile-{constants, variables, tag-number}.
1353 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1354 ;; with `goto's destined for the end of the code.
1355 ;; That is for use by the compiler.
1356 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1357 ;; In that case, we put a pc value into the list
1358 ;; before each insn (or its label).
1362 lap tmp
1363 endtag
1369 optr ptr
1373 ;; it's a pc
1379 tags)))))))
1390 byte-compile-variables)))))))
1397 ;; lap = ( [ (pc . (op . arg)) ]* )
1399 lap))
1401 ;; take off the dummy nil op that we replaced a trailing "return" with.
1406 ;; this addr is jumped to
1417 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1420 elt
1424 \f
1425 ;;; peephole optimizer
1431 byte-goto-if-not-nil-else-pop))
1435 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1436 byte-eq byte-not
1437 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1438 byte-interactive-p)
1439 ;; How about other side-effect-free-ops? Is it safe to move an
1440 ;; error invocation (such as from nth) out of an unwind-protect?
1441 ;; No, it is not, because the unwind-protect forms can alter
1442 ;; the inside of the object to which nth would apply.
1443 ;; For the same reason, byte-equal was deleted from this list.
1448 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1449 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1450 byte-point-min byte-following-char byte-preceding-char
1451 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1452 byte-current-buffer byte-interactive-p))
1457 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1458 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1459 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1461 byte-member byte-assq byte-quo byte-rem)
1462 byte-compile-side-effect-and-error-free-ops))
1464 ;;; This crock is because of the way DEFVAR_BOOL variables work.
1465 ;;; Consider the code
1466 ;;;
1467 ;;; (defun foo (flag)
1468 ;;; (let ((old-pop-ups pop-up-windows)
1469 ;;; (pop-up-windows flag))
1470 ;;; (cond ((not (eq pop-up-windows old-pop-ups))
1471 ;;; (setq old-pop-ups pop-up-windows)
1472 ;;; ...))))
1473 ;;;
1474 ;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1475 ;;; something else. But if we optimize
1476 ;;;
1477 ;;; varref flag
1478 ;;; varbind pop-up-windows
1479 ;;; varref pop-up-windows
1480 ;;; not
1481 ;;; to
1482 ;;; varref flag
1483 ;;; dup
1484 ;;; varbind pop-up-windows
1485 ;;; not
1486 ;;;
1487 ;;; we break the program, because it will appear that pop-up-windows and
1488 ;;; old-pop-ups are not EQ when really they are. So we have to know what
1489 ;;; the BOOL variables are, and not perform this optimization on them.
1491 ;;; The variable `byte-boolean-vars' is now primitive and updated
1492 ;;; automatically by DEFVAR_BOOL.
1495 "Simple peephole optimizer. LAP is both modified and returned."
1497 lap1
1498 lap2
1501 rest tmp tmp2 tmp3
1503 byte-compile-side-effect-free-ops
1504 byte-compile-side-effect-and-error-free-ops)))
1509 keep-going nil)
1515 ;; You may notice that sequences like "dup varset discard" are
1516 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1517 ;; You may be tempted to change this; resist that temptation.
1519 ;; <side-effect-free> pop --> <deleted>
1520 ;; ...including:
1521 ;; const-X pop --> <deleted>
1522 ;; varref-X pop --> <deleted>
1523 ;; dup pop --> <deleted>
1524 ;;
1544 ;;
1545 ;; goto*-X X: --> X:
1546 ;;
1561 ;;
1562 ;; varset-X varref-X --> dup varset-X
1563 ;; varbind-X varref-X --> dup varbind-X
1564 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1565 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1566 ;; The latter two can enable other optimizations.
1567 ;;
1573 nil
1583 lap0 lap1 lap2 lap0 lap1
1591 ;; The stack depth gets locally increased, so we will
1592 ;; increase maxdepth in case depth = maxdepth here.
1593 ;; This can cause the third argument to byte-code to
1594 ;; be larger than necessary.
1596 ;;
1597 ;; dup varset-X discard --> varset-X
1598 ;; dup varbind-X discard --> varbind-X
1599 ;; (the varbind variant can emerge from other optimizations)
1600 ;;
1608 ;;
1609 ;; not goto-X-if-nil --> goto-X-if-non-nil
1610 ;; not goto-X-if-non-nil --> goto-X-if-nil
1611 ;;
1612 ;; it is wrong to do the same thing for the -else-pop variants.
1613 ;;
1618 lap1
1621 'byte-goto-if-not-nil
1625 'byte-goto-if-not-nil
1629 ;;
1630 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1631 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1632 ;;
1633 ;; it is wrong to do the same thing for the -else-pop variants.
1634 ;;
1642 lap0 lap1 lap2
1647 ;;
1648 ;; const goto-if-* --> whatever
1649 ;;
1657 lap0 lap1)
1670 ;;
1671 ;; varref-X varref-X --> varref-X dup
1672 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1673 ;; We don't optimize the const-X variations on this here,
1674 ;; because that would inhibit some goto optimizations; we
1675 ;; optimize the const-X case after all other optimizations.
1676 ;;
1682 t)
1692 lap0 str lap0 lap0 str)))
1697 ;;
1698 ;; TAG1: TAG2: --> TAG1: <deleted>
1699 ;; (and other references to TAG2 are replaced with TAG1)
1700 ;;
1711 keep-going t))
1712 ;;
1713 ;; unused-TAG: --> <deleted>
1714 ;;
1720 keep-going t))
1721 ;;
1722 ;; goto ... --> goto <delete until TAG or end>
1723 ;; return ... --> return <delete until TAG or end>
1724 ;;
1730 str deleted)
1745 lap0
1751 tagstr lap0 tagstr))))
1754 ;;
1755 ;; <safe-op> unbind --> unbind <safe-op>
1756 ;; (this may enable other optimizations.)
1757 ;;
1764 ;;
1765 ;; varbind-X unbind-N --> discard unbind-(N-1)
1766 ;; save-excursion unbind-N --> unbind-(N-1)
1767 ;; save-restriction unbind-N --> unbind-(N-1)
1768 ;;
1771 byte-save-restriction))
1788 ;;
1789 ;; goto*-X ... X: goto-Y --> goto*-Y
1790 ;; goto-X ... X: return --> return
1791 ;;
1804 ;;
1805 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1806 ;; goto-*-else-pop X ... X: discard --> whatever
1807 ;;
1809 byte-goto-if-not-nil-else-pop))
1816 byte-goto-if-nil)
1818 byte-goto-if-not-nil))))
1824 ;; Get rid of the -else-pop's and jump one step further.
1833 ;;
1834 ;; const goto-X ... X: goto-if-* --> whatever
1835 ;; const goto-X ... X: discard --> whatever
1836 ;;
1848 byte-goto-if-not-nil-else-pop)))
1850 lap0 tmp2 lap0 tmp2)
1853 ;; Let next step fix the (const,goto-if*) sequence.
1856 ;; Jump one step further
1859 lap0 tmp2)
1866 ;;
1867 ;; X: varref-Y ... varset-Y goto-X -->
1868 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1869 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1870 ;; (This is so usual for while loops that it is worth handling).
1871 ;;
1879 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1884 lap1 lap2
1888 )
1893 ;;
1894 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1895 ;; (This can pull the loop test to the end of the loop)
1896 ;;
1903 byte-goto-if-nil-else-pop)))
1904 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1905 ;; lap0 lap1 (cdr lap0) (car tmp))
1914 byte-goto-if-not-nil-else-pop)
1916 byte-goto-if-nil-else-pop))))
1917 newtag)
1920 )
1923 ;; We can handle this case but not the -if-not-nil case,
1924 ;; because we won't know which non-nil constant to push.
1930 byte-goto-if-not-nil
1931 byte-goto-if-nil
1932 byte-goto-if-not-nil
1933 byte-goto byte-goto))))
1934 )
1936 )
1938 )
1939 ;; Cleanup stage:
1940 ;; Rebuild byte-compile-constants / byte-compile-variables.
1941 ;; Simple optimizations that would inhibit other optimizations if they
1942 ;; were done in the optimizing loop, and optimizations which there is no
1943 ;; need to do more than once.
1945 byte-compile-variables nil)
1955 byte-compile-constants)))
1958 byte-compile-variables)))))
1960 ;; const-C varset-X const-C --> const-C dup varset-X
1961 ;; const-C varbind-X const-C --> const-C dup varbind-X
1962 ;;
1968 lap0 lap1 lap0 lap0 lap1)
1972 ;;
1973 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1974 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1975 ;;
1978 tmp2 nil)
1988 ;;
1989 ;; unbind-N unbind-M --> unbind-(N+M)
1990 ;;
1999 )
2002 lap)
2006 \f
2007 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2008 ;; itself, compile some of its most used recursive functions (at load time).
2009 ;;
2020 byte-optimize-body
2021 byte-optimize-predicate
2022 byte-optimize-binary-predicate
2023 ;; Inserted some more than necessary, to speed it up.
2024 byte-optimize-form-code-walker
2025 byte-optimize-lapcode))))
2026 nil)
2028 ;;; byte-opt.el ends here