| blob | c60ae46a9973e23c69e445719e0d61ef6f7b835a |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler.
3 ;;; Copyright (c) 1991, 1994 Free Software Foundation, Inc.
5 ;; Author: Jamie Zawinski <jwz@lucid.com>
6 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
7 ;; Keywords: internal
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation; either version 2, or (at your option)
14 ;; any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs; see the file COPYING. If not, write to the
23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
24 ;; Boston, MA 02111-1307, USA.
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 'mocklisp-arguments '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.
263 form)
264 ;; else
285 ;; Give up on inlining.
286 form))))))
288 ;;; ((lambda ...) ...)
289 ;;;
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)
348 newform)))))
350 \f
351 ;;; implementing source-level optimizers
354 ;;
355 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
356 ;; we need to have special knowledge of the syntax of the special forms
357 ;; like let and defun (that's why they're special forms :-). (Actually,
358 ;; the important aspect is that they are subrs that don't evaluate all of
359 ;; their args.)
360 ;;
362 tmp)
368 form))
373 ;; map (quote nil) to nil to simplify optimizer logic.
374 ;; map quoted constants to nil if for-effect (just because).
377 form))
382 ;; recursively enter the optimizer for the bindings and body
383 ;; of a let or let*. This for depth-firstness: forms that
384 ;; are more deeply nested are optimized first.
389 binding
406 clause))
409 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
428 ;; those subrs which have an implicit progn; it's not quite good
429 ;; enough to treat these like normal function calls.
430 ;; This can turn (save-excursion ...) into (save-excursion) which
431 ;; will be optimized away in the lap-optimize pass.
435 ;; this is just like the above, except for the first argument.
449 ;; take forms off the back until we can't any more.
450 ;; In the future it could conceivably be a problem that the
451 ;; subexpressions of these forms are optimized in the reverse
452 ;; order, but it's ok for now.
458 for-effect))))
470 nil)
473 condition-case save-window-excursion))
474 ;; These forms are compiled as constants or by breaking out
475 ;; all the subexpressions and compiling them separately.
476 form)
479 ;; the "protected" part of an unwind-protect is compiled (and thus
480 ;; optimized) as a top-level form, so don't do it here. But the
481 ;; non-protected part has the same for-effect status as the
482 ;; unwind-protect itself. (The protected part is always for effect,
483 ;; but that isn't handled properly yet.)
489 ;; the body of a catch is compiled (and thus optimized) as a
490 ;; top-level form, so don't do it here. The tag is never
491 ;; for-effect. The body should have the same for-effect status
492 ;; as the catch form itself, but that isn't handled properly yet.
497 ;; If optimization is on, this is the only place that macros are
498 ;; expanded. If optimization is off, then macroexpansion happens
499 ;; in byte-compile-form. Otherwise, the macros are already expanded
500 ;; by the time that is reached.
503 byte-compile-macro-environment))))
506 ;; Support compiler macros as in cl.el.
518 form)
526 nil)))
528 ;; appending a nil here might not be necessary, but it can't hurt.
533 ;; Otherwise, no args can be considered to be for-effect,
534 ;; even if the called function is for-effect, because we
535 ;; don't know anything about that function.
540 "The source-level pass of the optimizer."
541 ;;
542 ;; First, optimize all sub-forms of this one.
544 ;;
545 ;; after optimizing all subforms, optimize this form until it doesn't
546 ;; optimize any further. This means that some forms will be passed through
547 ;; the optimizer many times, but that's necessary to make the for-effect
548 ;; processing do as much as possible.
549 ;;
554 ;; we don't have any of these yet, but we might.
559 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
562 new)
563 form)))
567 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
568 ;; forms, all but the last of which are optimized with the assumption that
569 ;; they are being called for effect. the last is for-effect as well if
570 ;; all-for-effect is true. returns a new list of forms.
573 fe new)
582 \f
583 ;;; some source-level optimizers
584 ;;;
585 ;;; when writing optimizers, be VERY careful that the optimizer returns
586 ;;; something not EQ to its argument if and ONLY if it has made a change.
587 ;;; This implies that you cannot simply destructively modify the list;
588 ;;; you must return something not EQ to it if you make an optimization.
589 ;;;
590 ;;; It is now safe to optimize code such that it introduces new bindings.
592 ;; I'd like this to be a defsubst, but let's not be self-referential...
594 ;; Returns non-nil if FORM is a non-nil constant.
599 ;; If the function is being called with constant numeric args,
600 ;; evaluate as much as possible at compile-time. This optimizer
601 ;; assumes that the function is associative, like + or *.
619 form)))
621 ;; If the function is being called with constant numeric args,
622 ;; evaluate as much as possible at compile-time. This optimizer
623 ;; assumes that the function satisfies
624 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
625 ;; like - and /.
629 form
637 constant))))
639 ;;(defun byte-optimize-associative-two-args-math (form)
640 ;; (setq form (byte-optimize-associative-math form))
641 ;; (if (consp form)
642 ;; (byte-optimize-two-args-left form)
643 ;; form))
645 ;;(defun byte-optimize-nonassociative-two-args-math (form)
646 ;; (setq form (byte-optimize-nonassociative-math form))
647 ;; (if (consp form)
648 ;; (byte-optimize-two-args-right form)
649 ;; form))
654 ;; Collect all the constants from FORM, after the STARTth arg,
655 ;; and apply FUN to them to make one argument at the end.
656 ;; For functions that can handle floats, that optimization
657 ;; can be incorrect because reordering can cause an overflow
658 ;; that would otherwise be avoided by encountering an arg that is a float.
659 ;; We avoid this problem by (1) not moving float constants and
660 ;; (2) not moving anything if it would cause an overflow.
662 ;; Merge all FORM's constants from number START, call FUN on them
663 ;; and put the result at the end.
666 ;; t means we must check for overflow.
677 ;; If necessary, check now for overflow
678 ;; that might be caused by reordering.
680 ;; We have overflow if the result of doing the arithmetic
681 ;; on floats is not even close to the result
682 ;; of doing it on integers.
689 form))
694 ;;(setq form (byte-optimize-associative-two-args-math form))
699 ;;; It is not safe to delete the function entirely
700 ;;; (actually, it would be safe if we know the sole arg
701 ;;; is not a marker).
702 ;; ((null (cdr (cdr form))) (nth 1 form))
706 form))
710 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
720 other)))
724 ;; Put constants at the end, except the last constant.
726 ;; Now only first and last element can be a number.
729 ;; (- x y ... 0) --> (- x y ...)
736 ;; If form is (- CONST foo... CONST), merge first and last.
741 ;;; It is not safe to delete the function entirely
742 ;;; (actually, it would be safe if we know the sole arg
743 ;;; is not a marker).
744 ;;; (if (eq (nth 2 form) 0)
745 ;;; (nth 1 form) ; (- x 0) --> x
750 form))
751 ;;; )
752 )
756 ;; If there is a constant in FORM, it is now the last element.
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 or if it appears in other arithmetic).
761 ;;; ((null (cdr (cdr form))) (nth 1 form))
793 last nil))))
795 ;;; ((null (cdr (cdr form)))
796 ;;; (nth 1 form))
824 ;; This can enable some lapcode optimizations.
826 form))
838 form)))
846 form))
891 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
892 ;; take care of this? - Jamie
893 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
894 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
900 form
913 ;; Simplify if less than 2 args.
914 ;; if there is a literal nil in the args to `and', throw it and following
915 ;; forms away, and surround the `and' with (progn ... nil).
924 nil))
930 ;; Throw away nil's, and simplify if less than 2 args.
931 ;; If there is a literal non-nil constant in the args to `or', throw away all
932 ;; following forms.
945 ;; if any clauses have a literal nil as their test, throw them away.
946 ;; if any clause has a literal non-nil constant as its test, throw
947 ;; away all following clauses.
949 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
968 ;;
969 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
977 form))
978 form))
981 ;; (if <true-constant> <then> <else...>) ==> <then>
982 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
983 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
984 ;; (if <test> <then> nil) ==> (if <test> <then>)
995 form))
998 ;; Don't make a double negative;
999 ;; instead, take away the one that is there.
1012 form))
1020 ;; byte-compile-negation-optimizer lives in bytecomp.el
1027 ;; (funcall '(lambda ...) ...) ==> ((lambda ...) ...)
1028 ;; (funcall 'foo ...) ==> (foo ...)
1032 form)))
1035 ;; If the last arg is a literal constant, turn this into a funcall.
1036 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1046 "last arg to apply can't be a literal atom: %s"
1048 nil))
1049 form)))
1059 ;; No bindings
1062 form)
1063 ;; The body is nil
1088 form)))
1100 form)))
1101 \f
1102 ;;; enumerating those functions which need not be called if the returned
1103 ;;; value is not used. That is, something like
1104 ;;; (progn (list (something-with-side-effects) (yow))
1105 ;;; (foo))
1106 ;;; may safely be turned into
1107 ;;; (progn (progn (something-with-side-effects) (yow))
1108 ;;; (foo))
1109 ;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1111 ;;; I wonder if I missed any :-\)
1114 assoc assq
1115 boundp buffer-file-name buffer-local-variables buffer-modified-p
1116 buffer-substring
1117 capitalize car-less-than-car car cdr ceiling concat coordinates-in-window-p
1118 copy-marker cos count-lines
1119 default-boundp default-value documentation downcase
1120 elt exp expt fboundp featurep
1121 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1122 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1123 float floor format
1124 get get-buffer get-buffer-window getenv get-file-buffer
1125 int-to-string
1126 length log log10 logand logb logior lognot logxor lsh
1127 marker-buffer max member memq min mod
1128 next-window nth nthcdr number-to-string
1129 parse-colon-path previous-window
1130 radians-to-degrees rassq regexp-quote reverse round
1132 string-to-int string-to-number substring symbol-plist
1133 tan upcase user-variable-p vconcat
1134 window-buffer window-dedicated-p window-edges window-height
1135 window-hscroll window-minibuffer-p window-width
1136 zerop))
1139 bobp bolp buffer-end buffer-list buffer-size buffer-string bufferp
1140 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1141 current-buffer
1142 dot dot-marker eobp eolp eq eql equal eventp floatp framep
1143 get-largest-window get-lru-window
1144 identity ignore integerp integer-or-marker-p interactive-p
1145 invocation-directory invocation-name
1146 keymapp list listp
1147 make-marker mark mark-marker markerp memory-limit minibuffer-window
1148 mouse-movement-p
1149 natnump nlistp not null number-or-marker-p numberp
1150 one-window-p overlayp
1151 point point-marker point-min point-max processp
1152 selected-window sequencep stringp subrp symbolp syntax-table-p
1153 user-full-name user-login-name user-original-login-name
1154 user-real-login-name user-real-uid user-uid
1155 vector vectorp
1156 window-configuration-p window-live-p windowp)))
1163 nil)
1167 ;; form is (byte-code "..." [...] n)
1173 byte-compile-maxdepth))
1178 \f
1182 ;;; This function extracts the bitfields from variable-length opcodes.
1183 ;;; Originally defined in disass.el (which no longer uses it.)
1186 "Don't call this!"
1187 ;; fetch and return the offset for the current opcode.
1188 ;; return NIL if this opcode has no offset
1189 ;; OP, PTR and BYTES are used and set dynamically
1220 ;;; This de-compiler is used for inline expansion of compiled functions,
1221 ;;; and by the disassembler.
1222 ;;;
1223 ;;; This list contains numbers, which are pc values,
1224 ;;; before each instruction.
1226 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1232 ;; As byte-decompile-bytecode, but updates
1233 ;; byte-compile-{constants, variables, tag-number}.
1234 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1235 ;; with `goto's destined for the end of the code.
1236 ;; That is for use by the compiler.
1237 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1238 ;; In that case, we put a pc value into the list
1239 ;; before each insn (or its label).
1243 lap tmp
1244 endtag
1250 optr ptr
1254 ;; it's a pc
1260 tags)))))))
1271 byte-compile-variables)))))))
1278 ;; lap = ( [ (pc . (op . arg)) ]* )
1280 lap))
1282 ;; take off the dummy nil op that we replaced a trailing "return" with.
1287 ;; this addr is jumped to
1298 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1301 elt
1305 \f
1306 ;;; peephole optimizer
1312 byte-goto-if-not-nil-else-pop))
1316 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1317 byte-eq byte-not
1318 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1319 byte-interactive-p)
1320 ;; How about other side-effect-free-ops? Is it safe to move an
1321 ;; error invocation (such as from nth) out of an unwind-protect?
1322 ;; No, it is not, because the unwind-protect forms can alter
1323 ;; the inside of the object to which nth would apply.
1324 ;; For the same reason, byte-equal was deleted from this list.
1329 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1330 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1331 byte-point-min byte-following-char byte-preceding-char
1332 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1333 byte-current-buffer byte-interactive-p))
1338 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1339 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1340 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1342 byte-member byte-assq byte-quo byte-rem)
1343 byte-compile-side-effect-and-error-free-ops))
1345 ;;; This crock is because of the way DEFVAR_BOOL variables work.
1346 ;;; Consider the code
1347 ;;;
1348 ;;; (defun foo (flag)
1349 ;;; (let ((old-pop-ups pop-up-windows)
1350 ;;; (pop-up-windows flag))
1351 ;;; (cond ((not (eq pop-up-windows old-pop-ups))
1352 ;;; (setq old-pop-ups pop-up-windows)
1353 ;;; ...))))
1354 ;;;
1355 ;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1356 ;;; something else. But if we optimize
1357 ;;;
1358 ;;; varref flag
1359 ;;; varbind pop-up-windows
1360 ;;; varref pop-up-windows
1361 ;;; not
1362 ;;; to
1363 ;;; varref flag
1364 ;;; dup
1365 ;;; varbind pop-up-windows
1366 ;;; not
1367 ;;;
1368 ;;; we break the program, because it will appear that pop-up-windows and
1369 ;;; old-pop-ups are not EQ when really they are. So we have to know what
1370 ;;; the BOOL variables are, and not perform this optimization on them.
1371 ;;;
1374 cannot-suspend check-markers-debug-flag completion-auto-help
1375 completion-ignore-case cursor-in-echo-area debug-on-next-call
1376 debug-on-quit delete-exited-processes enable-recursive-minibuffers
1377 garbage-collection-messages highlight-nonselected-windows
1378 indent-tabs-mode inherit-process-coding-system inhibit-eol-conversion
1379 inhibit-local-menu-bar-menus insert-default-directory inverse-video
1380 keyword-symbols-constant-flag load-convert-to-unibyte
1381 load-force-doc-strings load-in-progress menu-prompting
1382 minibuffer-allow-text-properties minibuffer-auto-raise
1383 mode-line-inverse-video multiple-frames no-redraw-on-reenter
1384 noninteractive parse-sexp-ignore-comments parse-sexp-lookup-properties
1385 pop-up-frames pop-up-windows print-escape-multibyte
1386 print-escape-newlines
1387 print-escape-nonascii print-quoted scroll-preserve-screen-position
1388 system-uses-terminfo truncate-partial-width-windows
1389 unibyte-display-via-language-environment use-dialog-box
1390 visible-bell vms-stmlf-recfm words-include-escapes)
1391 "DEFVAR_BOOL variables. Giving these any non-nil value sets them to t.
1392 If this does not enumerate all DEFVAR_BOOL variables, the byte-optimizer
1396 "Simple peephole optimizer. LAP is both modified and returned."
1398 lap1 off1
1399 lap2 off2
1402 rest tmp tmp2 tmp3
1404 byte-compile-side-effect-free-ops
1405 byte-compile-side-effect-and-error-free-ops)))
1410 keep-going nil)
1416 ;; You may notice that sequences like "dup varset discard" are
1417 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1418 ;; You may be tempted to change this; resist that temptation.
1420 ;; <side-effect-free> pop --> <deleted>
1421 ;; ...including:
1422 ;; const-X pop --> <deleted>
1423 ;; varref-X pop --> <deleted>
1424 ;; dup pop --> <deleted>
1425 ;;
1445 ;;
1446 ;; goto*-X X: --> X:
1447 ;;
1462 ;;
1463 ;; varset-X varref-X --> dup varset-X
1464 ;; varbind-X varref-X --> dup varbind-X
1465 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1466 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1467 ;; The latter two can enable other optimizations.
1468 ;;
1474 nil
1483 lap0 lap1 lap2 lap0 lap1
1491 ;; The stack depth gets locally increased, so we will
1492 ;; increase maxdepth in case depth = maxdepth here.
1493 ;; This can cause the third argument to byte-code to
1494 ;; be larger than necessary.
1496 ;;
1497 ;; dup varset-X discard --> varset-X
1498 ;; dup varbind-X discard --> varbind-X
1499 ;; (the varbind variant can emerge from other optimizations)
1500 ;;
1508 ;;
1509 ;; not goto-X-if-nil --> goto-X-if-non-nil
1510 ;; not goto-X-if-non-nil --> goto-X-if-nil
1511 ;;
1512 ;; it is wrong to do the same thing for the -else-pop variants.
1513 ;;
1518 lap1
1521 'byte-goto-if-not-nil
1525 'byte-goto-if-not-nil
1529 ;;
1530 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1531 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1532 ;;
1533 ;; it is wrong to do the same thing for the -else-pop variants.
1534 ;;
1542 lap0 lap1 lap2
1547 ;;
1548 ;; const goto-if-* --> whatever
1549 ;;
1557 lap0 lap1)
1570 ;;
1571 ;; varref-X varref-X --> varref-X dup
1572 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1573 ;; We don't optimize the const-X variations on this here,
1574 ;; because that would inhibit some goto optimizations; we
1575 ;; optimize the const-X case after all other optimizations.
1576 ;;
1582 t)
1592 lap0 str lap0 lap0 str)))
1597 ;;
1598 ;; TAG1: TAG2: --> TAG1: <deleted>
1599 ;; (and other references to TAG2 are replaced with TAG1)
1600 ;;
1611 keep-going t))
1612 ;;
1613 ;; unused-TAG: --> <deleted>
1614 ;;
1620 keep-going t))
1621 ;;
1622 ;; goto ... --> goto <delete until TAG or end>
1623 ;; return ... --> return <delete until TAG or end>
1624 ;;
1630 str deleted)
1645 lap0
1651 tagstr lap0 tagstr))))
1654 ;;
1655 ;; <safe-op> unbind --> unbind <safe-op>
1656 ;; (this may enable other optimizations.)
1657 ;;
1664 ;;
1665 ;; varbind-X unbind-N --> discard unbind-(N-1)
1666 ;; save-excursion unbind-N --> unbind-(N-1)
1667 ;; save-restriction unbind-N --> unbind-(N-1)
1668 ;;
1671 byte-save-restriction))
1688 ;;
1689 ;; goto*-X ... X: goto-Y --> goto*-Y
1690 ;; goto-X ... X: return --> return
1691 ;;
1704 ;;
1705 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1706 ;; goto-*-else-pop X ... X: discard --> whatever
1707 ;;
1709 byte-goto-if-not-nil-else-pop))
1716 byte-goto-if-nil)
1718 byte-goto-if-not-nil))))
1724 ;; Get rid of the -else-pop's and jump one step further.
1733 ;;
1734 ;; const goto-X ... X: goto-if-* --> whatever
1735 ;; const goto-X ... X: discard --> whatever
1736 ;;
1748 byte-goto-if-not-nil-else-pop)))
1750 lap0 tmp2 lap0 tmp2)
1753 ;; Let next step fix the (const,goto-if*) sequence.
1756 ;; Jump one step further
1759 lap0 tmp2)
1766 ;;
1767 ;; X: varref-Y ... varset-Y goto-X -->
1768 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1769 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1770 ;; (This is so usual for while loops that it is worth handling).
1771 ;;
1779 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1784 lap1 lap2
1788 )
1793 ;;
1794 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1795 ;; (This can pull the loop test to the end of the loop)
1796 ;;
1803 byte-goto-if-nil-else-pop)))
1804 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1805 ;; lap0 lap1 (cdr lap0) (car tmp))
1814 byte-goto-if-not-nil-else-pop)
1816 byte-goto-if-nil-else-pop))))
1817 newtag)
1820 )
1823 ;; We can handle this case but not the -if-not-nil case,
1824 ;; because we won't know which non-nil constant to push.
1830 byte-goto-if-not-nil
1831 byte-goto-if-nil
1832 byte-goto-if-not-nil
1833 byte-goto byte-goto))))
1834 )
1836 )
1838 )
1839 ;; Cleanup stage:
1840 ;; Rebuild byte-compile-constants / byte-compile-variables.
1841 ;; Simple optimizations that would inhibit other optimizations if they
1842 ;; were done in the optimizing loop, and optimizations which there is no
1843 ;; need to do more than once.
1845 byte-compile-variables nil)
1854 byte-compile-variables)))
1857 byte-compile-constants)))))
1859 ;; const-C varset-X const-C --> const-C dup varset-X
1860 ;; const-C varbind-X const-C --> const-C dup varbind-X
1861 ;;
1867 lap0 lap1 lap0 lap0 lap1)
1871 ;;
1872 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1873 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1874 ;;
1877 tmp2 nil)
1887 ;;
1888 ;; unbind-N unbind-M --> unbind-(N+M)
1889 ;;
1898 )
1901 lap)
1905 \f
1906 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
1907 ;; itself, compile some of its most used recursive functions (at load time).
1908 ;;
1919 byte-optimize-body
1920 byte-optimize-predicate
1921 byte-optimize-binary-predicate
1922 ;; Inserted some more than necessary, to speed it up.
1923 byte-optimize-form-code-walker
1924 byte-optimize-lapcode))))
1925 nil)
1927 ;;; byte-opt.el ends here