| blob | 1a34fa78aefe14e4277ab9d7e56593e61515654f |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler -*- lexical-binding: t -*-
3 ;; Copyright (C) 1991, 1994, 2000-2015 Free Software Foundation, Inc.
5 ;; Author: Jamie Zawinski <jwz@lucid.com>
6 ;; Hallvard Furuseth <hbf@ulrik.uio.no>
7 ;; Maintainer: emacs-devel@gnu.org
8 ;; Keywords: internal
9 ;; Package: emacs
11 ;; This file is part of GNU Emacs.
13 ;; GNU Emacs is free software: you can redistribute it and/or modify
14 ;; it under the terms of the GNU General Public License as published by
15 ;; the Free Software Foundation, either version 3 of the License, or
16 ;; (at your option) any later version.
18 ;; GNU Emacs is distributed in the hope that it will be useful,
19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ;; GNU General Public License for more details.
23 ;; You should have received a copy of the GNU General Public License
24 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
26 ;;; Commentary:
28 ;; ========================================================================
29 ;; "No matter how hard you try, you can't make a racehorse out of a pig.
30 ;; You can, however, make a faster pig."
31 ;;
32 ;; Or, to put it another way, the Emacs byte compiler is a VW Bug. This code
33 ;; makes it be a VW Bug with fuel injection and a turbocharger... You're
34 ;; still not going to make it go faster than 70 mph, but it might be easier
35 ;; to get it there.
36 ;;
38 ;; TO DO:
39 ;;
40 ;; (apply (lambda (x &rest y) ...) 1 (foo))
41 ;;
42 ;; maintain a list of functions known not to access any global variables
43 ;; (actually, give them a 'dynamically-safe property) and then
44 ;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
45 ;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
46 ;; by recursing on this, we might be able to eliminate the entire let.
47 ;; However certain variables should never have their bindings optimized
48 ;; away, because they affect everything.
49 ;; (put 'debug-on-error 'binding-is-magic t)
50 ;; (put 'debug-on-abort 'binding-is-magic t)
51 ;; (put 'debug-on-next-call 'binding-is-magic t)
52 ;; (put 'inhibit-quit 'binding-is-magic t)
53 ;; (put 'quit-flag 'binding-is-magic t)
54 ;; (put 't 'binding-is-magic t)
55 ;; (put 'nil 'binding-is-magic t)
56 ;; possibly also
57 ;; (put 'gc-cons-threshold 'binding-is-magic t)
58 ;; (put 'track-mouse 'binding-is-magic t)
59 ;; others?
60 ;;
61 ;; Simple defsubsts often produce forms like
62 ;; (let ((v1 (f1)) (v2 (f2)) ...)
63 ;; (FN v1 v2 ...))
64 ;; It would be nice if we could optimize this to
65 ;; (FN (f1) (f2) ...)
66 ;; but we can't unless FN is dynamically-safe (it might be dynamically
67 ;; referring to the bindings that the lambda arglist established.)
68 ;; One of the uncountable lossages introduced by dynamic scope...
69 ;;
70 ;; Maybe there should be a control-structure that says "turn on
71 ;; fast-and-loose type-assumptive optimizations here." Then when
72 ;; we see a form like (car foo) we can from then on assume that
73 ;; the variable foo is of type cons, and optimize based on that.
74 ;; But, this won't win much because of (you guessed it) dynamic
75 ;; scope. Anything down the stack could change the value.
76 ;; (Another reason it doesn't work is that it is perfectly valid
77 ;; to call car with a null argument.) A better approach might
78 ;; be to allow type-specification of the form
79 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
80 ;; (put 'foo 'result-type 'bool)
81 ;; It should be possible to have these types checked to a certain
82 ;; degree.
83 ;;
84 ;; collapse common subexpressions
85 ;;
86 ;; It would be nice if redundant sequences could be factored out as well,
87 ;; when they are known to have no side-effects:
88 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
89 ;; but beware of traps like
90 ;; (cons (list x y) (list x y))
91 ;;
92 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
93 ;; Tail-recursion elimination is almost always impossible when all variables
94 ;; have dynamic scope, but given that the "return" byteop requires the
95 ;; binding stack to be empty (rather than emptying it itself), there can be
96 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
97 ;; make any bindings.
98 ;;
99 ;; Here is an example of an Emacs Lisp function which could safely be
100 ;; byte-compiled tail-recursively:
101 ;;
102 ;; (defun tail-map (fn list)
103 ;; (cond (list
104 ;; (funcall fn (car list))
105 ;; (tail-map fn (cdr list)))))
106 ;;
107 ;; However, if there was even a single let-binding around the COND,
108 ;; it could not be byte-compiled, because there would be an "unbind"
109 ;; byte-op between the final "call" and "return." Adding a
110 ;; Bunbind_all byteop would fix this.
111 ;;
112 ;; (defun foo (x y z) ... (foo a b c))
113 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
114 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
115 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
116 ;;
117 ;; this also can be considered tail recursion:
118 ;;
119 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
120 ;; could generalize this by doing the optimization
121 ;; (goto X) ... X: (return) --> (return)
122 ;;
123 ;; But this doesn't solve all of the problems: although by doing tail-
124 ;; recursion elimination in this way, the call-stack does not grow, the
125 ;; binding-stack would grow with each recursive step, and would eventually
126 ;; overflow. I don't believe there is any way around this without lexical
127 ;; scope.
128 ;;
129 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
130 ;;
131 ;; Idea: the form (lexical-scope) in a file means that the file may be
132 ;; compiled lexically. This proclamation is file-local. Then, within
133 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
134 ;; would do things the old way. (Or we could use CL "declare" forms.)
135 ;; We'd have to notice defvars and defconsts, since those variables should
136 ;; always be dynamic, and attempting to do a lexical binding of them
137 ;; should simply do a dynamic binding instead.
138 ;; But! We need to know about variables that were not necessarily defvared
139 ;; in the file being compiled (doing a boundp check isn't good enough.)
140 ;; Fdefvar() would have to be modified to add something to the plist.
141 ;;
142 ;; A major disadvantage of this scheme is that the interpreter and compiler
143 ;; would have different semantics for files compiled with (dynamic-scope).
144 ;; Since this would be a file-local optimization, there would be no way to
145 ;; modify the interpreter to obey this (unless the loader was hacked
146 ;; in some grody way, but that's a really bad idea.)
148 ;; Other things to consider:
150 ;; ;; Associative math should recognize subcalls to identical function:
151 ;; (disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
152 ;; ;; This should generate the same as (1+ x) and (1- x)
154 ;; (disassemble (lambda (x) (cons (+ x 1) (- x 1))))
155 ;; ;; An awful lot of functions always return a non-nil value. If they're
156 ;; ;; error free also they may act as true-constants.
158 ;; (disassemble (lambda (x) (and (point) (foo))))
159 ;; ;; When
160 ;; ;; - all but one arguments to a function are constant
161 ;; ;; - the non-constant argument is an if-expression (cond-expression?)
162 ;; ;; then the outer function can be distributed. If the guarding
163 ;; ;; condition is side-effect-free [assignment-free] then the other
164 ;; ;; arguments may be any expressions. Since, however, the code size
165 ;; ;; can increase this way they should be "simple". Compare:
167 ;; (disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
168 ;; (disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
170 ;; ;; (car (cons A B)) -> (prog1 A B)
171 ;; (disassemble (lambda (x) (car (cons (foo) 42))))
173 ;; ;; (cdr (cons A B)) -> (progn A B)
174 ;; (disassemble (lambda (x) (cdr (cons 42 (foo)))))
176 ;; ;; (car (list A B ...)) -> (prog1 A B ...)
177 ;; (disassemble (lambda (x) (car (list (foo) 42 (bar)))))
179 ;; ;; (cdr (list A B ...)) -> (progn A (list B ...))
180 ;; (disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
183 ;;; Code:
190 ;; Newer byte codes for stack-ref make the slot 0 non-nil again.
191 ;; But the "old disassembler" is *really* ancient by now.
192 ;; (if (aref byte-code-vector 0)
193 ;; (error "The old version of the disassembler is loaded. Reload new-bytecomp as well"))
202 arg)
218 c
220 args)))))
226 \f
227 ;;; byte-compile optimizers to support inlining
232 "byte-optimize-handler for the `inline' special-form."
245 sexp)))
257 (`nil
259 name)
260 form)
266 ;; (message "Inlining byte-code for %S!" name)
267 ;; The byte-code will be really inlined in byte-compile-unfold-bcf.
273 ;; While byte-compile-unfold-bcf can inline dynbind byte-code into
274 ;; letbind byte-code (or any other combination for that matter), we
275 ;; can only inline dynbind source into dynbind source or letbind
276 ;; source into letbind source.
278 ;; We can of course byte-compile the inlined function
279 ;; first, and then inline its byte-code.
283 ;; If `fn' is from the same file, it has already
284 ;; been preprocessed!
290 ;; This can happen because of macroexp-warn-and-return &co.
293 form))))
296 form))))
298 ;; ((lambda ...) ...)
300 ;; In lexical-binding mode, let and functions don't bind vars in the same way
301 ;; (let obey special-variable-p, but functions don't). But luckily, this
302 ;; doesn't matter here, because function's behavior is underspecified so it
303 ;; can safely be turned into a `let', even though the reverse is not true.
309 optionalp restp
310 bindings)
315 ;; FIXME: The checks below do not belong in an optimization phase.
318 ;; ok, I'll let this slide because funcall_lambda() does...
319 ;; (if optionalp (error "multiple &optional keywords in %s" name))
325 ;; ...but it is by no stretch of the imagination a reasonable
326 ;; thing that funcall_lambda() allows (&rest x y) and
327 ;; (&rest x &optional y) in arglists.
336 bindings)
337 values nil))
343 bindings)
351 form)
353 ;; The following leads to infinite recursion when loading a
354 ;; file containing `(defsubst f () (f))', and then trying to
355 ;; byte-compile that file.
356 ;(setq body (mapcar 'byte-optimize-form body)))
363 newform))))
365 \f
366 ;;; implementing source-level optimizers
369 ;;
370 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
371 ;; we need to have special knowledge of the syntax of the special forms
372 ;; like let and defun (that's why they're special forms :-). (Actually,
373 ;; the important aspect is that they are subrs that don't evaluate all of
374 ;; their args.)
375 ;;
377 tmp)
383 form))
388 ;; map (quote nil) to nil to simplify optimizer logic.
389 ;; map quoted constants to nil if for-effect (just because).
392 form))
396 ;; Some error occurred, avoid infinite recursion
397 form
401 ;; recursively enter the optimizer for the bindings and body
402 ;; of a let or let*. This for depth-firstness: forms that
403 ;; are more deeply nested are optimized first.
408 binding
425 clause))
428 ;; As an extra added bonus, this simplifies (progn <x>) --> <x>.
445 ;; those subrs which have an implicit progn; it's not quite good
446 ;; enough to treat these like normal function calls.
447 ;; This can turn (save-excursion ...) into (save-excursion) which
448 ;; will be optimized away in the lap-optimize pass.
452 ;; this is just like the above, except for the first argument.
468 ;; Take forms off the back until we can't any more.
469 ;; In the future it could conceivably be a problem that the
470 ;; subexpressions of these forms are optimized in the reverse
471 ;; order, but it's ok for now.
477 for-effect))))
484 backwards)))))
490 nil)
493 ;; This forms is compiled as constant or by breaking out
494 ;; all the subexpressions and compiling them separately.
495 form)
499 ;; Will be optimized later.
500 form
509 ;; the "protected" part of an unwind-protect is compiled (and thus
510 ;; optimized) as a top-level form, so don't do it here. But the
511 ;; non-protected part has the same for-effect status as the
512 ;; unwind-protect itself. (The protected part is always for effect,
513 ;; but that isn't handled properly yet.)
522 ;; The body of a catch is compiled (and thus
523 ;; optimized) as a top-level form, so don't do it
524 ;; here.
529 ;; Don't treat the args to `ignore' as being
530 ;; computed for effect. We want to avoid the warnings
531 ;; that might occur if they were treated that way.
532 ;; However, don't actually bother calling `ignore'.
535 ;; Needed as long as we run byte-optimize-form after cconv.
544 form)
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 `macroexp-const-p'."
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.
593 ;; (setq opt (get (car form)
594 ;; 'byte-for-effect-optimizer)))
598 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
601 new)
602 form)))
606 ;; Optimize the cdr of a progn or implicit progn; all forms is a list of
607 ;; forms, all but the last of which are optimized with the assumption that
608 ;; they are being called for effect. the last is for-effect as well if
609 ;; all-for-effect is true. returns a new list of forms.
612 fe new)
621 \f
622 ;; some source-level optimizers
623 ;;
624 ;; when writing optimizers, be VERY careful that the optimizer returns
625 ;; something not EQ to its argument if and ONLY if it has made a change.
626 ;; This implies that you cannot simply destructively modify the list;
627 ;; you must return something not EQ to it if you make an optimization.
628 ;;
629 ;; It is now safe to optimize code such that it introduces new bindings.
632 "Return non-nil if FORM always evaluates to a non-nil value."
638 ;; Can't use recursion in a defsubst.
639 ;; (`progn (byte-compile-trueconstp (car (last (cdr form)))))
640 ))
646 "Return non-nil if FORM always evaluates to a nil value."
652 ;; Can't use recursion in a defsubst.
653 ;; (`progn (byte-compile-nilconstp (car (last (cdr form)))))
654 ))
658 ;; If the function is being called with constant numeric args,
659 ;; evaluate as much as possible at compile-time. This optimizer
660 ;; assumes that the function is associative, like + or *.
678 form)))
680 ;; If the function is being called with constant numeric args,
681 ;; evaluate as much as possible at compile-time. This optimizer
682 ;; assumes that the function satisfies
683 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
684 ;; like - and /.
688 form
696 constant))))
698 ;;(defun byte-optimize-associative-two-args-math (form)
699 ;; (setq form (byte-optimize-associative-math form))
700 ;; (if (consp form)
701 ;; (byte-optimize-two-args-left form)
702 ;; form))
704 ;;(defun byte-optimize-nonassociative-two-args-math (form)
705 ;; (setq form (byte-optimize-nonassociative-math form))
706 ;; (if (consp form)
707 ;; (byte-optimize-two-args-right form)
708 ;; form))
713 ;; Collect all the constants from FORM, after the STARTth arg,
714 ;; and apply FUN to them to make one argument at the end.
715 ;; For functions that can handle floats, that optimization
716 ;; can be incorrect because reordering can cause an overflow
717 ;; that would otherwise be avoided by encountering an arg that is a float.
718 ;; We avoid this problem by (1) not moving float constants and
719 ;; (2) not moving anything if it would cause an overflow.
721 ;; Merge all FORM's constants from number START, call FUN on them
722 ;; and put the result at the end.
725 ;; t means we must check for overflow.
736 ;; If necessary, check now for overflow
737 ;; that might be caused by reordering.
739 ;; We have overflow if the result of doing the arithmetic
740 ;; on floats is not even close to the result
741 ;; of doing it on integers.
748 form))
754 ;; Don't call `byte-optimize-delay-constants-math' (bug#1334).
755 ;;(setq form (byte-optimize-delay-constants-math form 1 '+))
757 ;; For (+ constants...), byte-optimize-predicate does the work.
760 ;; (+ x 1) --> (1+ x) and (+ x -1) --> (1- x).
770 ;; Here, we could also do
771 ;; (+ x y ... 1) --> (1+ (+ x y ...))
772 ;; (+ x y ... -1) --> (1- (+ x y ...))
773 ;; The resulting bytecode is smaller, but is it faster? -- cyd
774 ))
778 ;; Don't call `byte-optimize-delay-constants-math' (bug#1334).
779 ;;(setq form (byte-optimize-delay-constants-math form 2 '+))
780 ;; Remove zeros.
785 ;; After the above, we must turn (- x) back into (- x 0)
788 ;; For (- constants..), byte-optimize-predicate does the work.
791 ;; (- x 1) --> (1- x)
794 ;; (- x -1) --> (1+ x)
797 ;; (- 0 x) --> (- x)
801 ;; Here, we could also do
802 ;; (- x y ... 1) --> (1- (- x y ...))
803 ;; (- x y ... -1) --> (1+ (- x y ...))
804 ;; The resulting bytecode is smaller, but is it faster? -- cyd
805 ))
810 ;; For (* constants..), byte-optimize-predicate does the work.
812 ;; After `byte-optimize-predicate', if there is a INTEGER constant
813 ;; in FORM, it is in the last element.
816 ;; Would handling (* ... 0) here cause floating point errors?
817 ;; See bug#1334.
827 ;; After `byte-optimize-predicate', if there is a INTEGER constant
828 ;; in FORM, it is in the last element.
831 ;; Runtime error (leave it intact).
835 ;; No constants in expression
837 ;; For (* constants..), byte-optimize-predicate does the work.
839 ;; (/ x y.. 1) --> (/ x y..)
842 ;; (/ x -1), (/ x .. -1) --> (- x), (- (/ x ..))
866 form)
884 form)))
892 form))
936 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
937 ;; take care of this? - Jamie
938 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
939 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
945 form
949 ;; Simplify if less than 2 args.
950 ;; if there is a literal nil in the args to `and', throw it and following
951 ;; forms away, and surround the `and' with (progn ... nil).
960 nil))
966 ;; Throw away nil's, and simplify if less than 2 args.
967 ;; If there is a literal non-nil constant in the args to `or', throw away all
968 ;; following forms.
981 ;; if any clauses have a literal nil as their test, throw them away.
982 ;; if any clause has a literal non-nil constant as its test, throw
983 ;; away all following clauses.
985 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
993 ;; This branch will always be taken: kill the subsequent ones.
1002 ;; This branch will never be taken: kill its body.
1004 ;;
1005 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
1013 form))
1014 form))
1017 ;; (if (progn <insts> <test>) <rest>) ==> (progn <insts> (if <test> <rest>))
1018 ;; (if <true-constant> <then> <else...>) ==> <then>
1019 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
1020 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
1021 ;; (if <test> <then> nil) ==> (if <test> <then>)
1024 ;; `clause' is a proper list.
1027 ;; A trivial `progn'.
1040 form))
1043 ;; Don't make a double negative;
1044 ;; instead, take away the one that is there.
1059 form))
1067 ;; byte-compile-negation-optimizer lives in bytecomp.el
1074 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1075 ;; (funcall foo ...) ==> (foo ...)
1079 form)))
1082 ;; If the last arg is a literal constant, turn this into a funcall.
1083 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1093 "last arg to apply can't be a literal atom: `%s'"
1095 nil))
1096 form)))
1106 ;; No bindings
1109 form)
1110 ;; The body is nil
1127 form))
1137 form)
1139 form))
1141 ;; Fixme: delete-char -> delete-region (byte-coded)
1142 ;; optimize string-as-unibyte, string-as-multibyte, string-make-unibyte,
1143 ;; string-make-multibyte for constant args.
1156 \f
1157 ;; enumerating those functions which need not be called if the returned
1158 ;; value is not used. That is, something like
1159 ;; (progn (list (something-with-side-effects) (yow))
1160 ;; (foo))
1161 ;; may safely be turned into
1162 ;; (progn (progn (something-with-side-effects) (yow))
1163 ;; (foo))
1164 ;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1166 ;; Some of these functions have the side effect of allocating memory
1167 ;; and it would be incorrect to replace two calls with one.
1168 ;; But we don't try to do those kinds of optimizations,
1169 ;; so it is safe to list such functions here.
1170 ;; Some of these functions return values that depend on environment
1171 ;; state, so that constant folding them would be wrong,
1172 ;; but we don't do constant folding based on this list.
1174 ;; However, at present the only optimization we normally do
1175 ;; is delete calls that need not occur, and we only do that
1176 ;; with the error-free functions.
1178 ;; I wonder if I missed any :-\)
1181 assoc assq
1182 boundp buffer-file-name buffer-local-variables buffer-modified-p
1183 buffer-substring byte-code-function-p
1184 capitalize car-less-than-car car cdr ceiling char-after char-before
1185 char-equal char-to-string char-width compare-strings
1186 compare-window-configurations concat coordinates-in-window-p
1187 copy-alist copy-sequence copy-marker cos count-lines
1188 decode-char
1189 decode-time default-boundp default-value documentation downcase
1190 elt encode-char 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-first-window
1195 frame-root-window frame-selected-window
1196 frame-visible-p fround ftruncate
1197 get gethash get-buffer get-buffer-window getenv get-file-buffer
1198 hash-table-count
1199 int-to-string intern-soft
1200 keymap-parent
1201 length local-variable-if-set-p local-variable-p log log10 logand
1202 logb logior lognot logxor lsh langinfo
1203 make-list make-string make-symbol marker-buffer max member memq min
1204 minibuffer-selected-window minibuffer-window
1205 mod multibyte-char-to-unibyte next-window nth nthcdr number-to-string
1206 parse-colon-path plist-get plist-member
1207 prefix-numeric-value previous-window prin1-to-string propertize
1208 degrees-to-radians
1209 radians-to-degrees rassq rassoc read-from-string regexp-quote
1210 region-beginning region-end reverse round
1212 string-to-int string-to-number substring sxhash symbol-function
1213 symbol-name symbol-plist symbol-value string-make-unibyte
1214 string-make-multibyte string-as-multibyte string-as-unibyte
1215 string-to-multibyte
1216 tan truncate
1217 unibyte-char-to-multibyte upcase user-full-name
1218 user-login-name user-original-login-name custom-variable-p
1219 vconcat
1220 window-absolute-pixel-edges window-at window-body-height
1221 window-body-width window-buffer window-dedicated-p window-display-table
1222 window-combination-limit window-edges window-frame window-fringes
1223 window-height window-hscroll window-inside-edges
1224 window-inside-absolute-pixel-edges window-inside-pixel-edges
1225 window-left-child window-left-column window-margins window-minibuffer-p
1226 window-next-buffers window-next-sibling window-new-normal
1227 window-new-total window-normal-size window-parameter window-parameters
1228 window-parent window-pixel-edges window-point window-prev-buffers
1229 window-prev-sibling window-redisplay-end-trigger window-scroll-bars
1230 window-start window-text-height window-top-child window-top-line
1231 window-total-height window-total-width window-use-time window-vscroll
1232 window-width zerop))
1235 bobp bolp bool-vector-p
1236 buffer-end buffer-list buffer-size buffer-string bufferp
1237 car-safe case-table-p cdr-safe char-or-string-p characterp
1238 charsetp commandp cons consp
1239 current-buffer current-global-map current-indentation
1240 current-local-map current-minor-mode-maps current-time
1241 current-time-string current-time-zone
1242 eobp eolp eq equal eventp
1243 floatp following-char framep
1244 get-largest-window get-lru-window
1245 hash-table-p
1246 identity ignore integerp integer-or-marker-p interactive-p
1247 invocation-directory invocation-name
1248 keymapp
1249 line-beginning-position line-end-position list listp
1250 make-marker mark mark-marker markerp max-char
1251 memory-limit minibuffer-window
1252 mouse-movement-p
1253 natnump nlistp not null number-or-marker-p numberp
1254 one-window-p overlayp
1255 point point-marker point-min point-max preceding-char primary-charset
1256 processp
1257 recent-keys recursion-depth
1258 safe-length selected-frame selected-window sequencep
1259 standard-case-table standard-syntax-table stringp subrp symbolp
1260 syntax-table syntax-table-p
1261 this-command-keys this-command-keys-vector this-single-command-keys
1262 this-single-command-raw-keys
1263 user-real-login-name user-real-uid user-uid
1264 vector vectorp visible-frame-list
1265 wholenump window-configuration-p window-live-p
1266 window-valid-p windowp)))
1273 nil)
1275 \f
1276 ;; pure functions are side-effect free functions whose values depend
1277 ;; only on their arguments. For these functions, calls with constant
1278 ;; arguments can be evaluated at compile time. This may shift run time
1279 ;; errors to compile time.
1286 nil)
1287 \f
1291 ;; Used and set dynamically in byte-decompile-bytecode-1.
1295 ;; This function extracts the bitfields from variable-length opcodes.
1296 ;; Originally defined in disass.el (which no longer uses it.)
1298 "Don't call this!"
1299 ;; Fetch and return the offset for the current opcode.
1300 ;; Return nil if this opcode has no offset.
1305 ;; Offset in next byte.
1309 ;; Offset in next 2 bytes.
1322 byte-pushconditioncase))))
1323 ;; Offset in next 2 bytes.
1335 ;; This de-compiler is used for inline expansion of compiled functions,
1336 ;; and by the disassembler.
1337 ;;
1338 ;; This list contains numbers, which are pc values,
1339 ;; before each instruction.
1341 "Turn BYTECODE into lapcode, referring to CONSTVEC."
1347 ;; As byte-decompile-bytecode, but updates
1348 ;; byte-compile-{constants, variables, tag-number}.
1349 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1350 ;; with `goto's destined for the end of the code.
1351 ;; That is for use by the compiler.
1352 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1353 ;; In that case, we put a pc value into the list
1354 ;; before each insn (or its label).
1358 lap tmp)
1363 optr bytedecomp-ptr
1364 ;; This uses dynamic-scope magic.
1370 ;; It's a pc.
1375 new)))))
1387 new)))))
1391 ;; The top bit of the operand for byte-discardN is a flag,
1392 ;; saying whether the top-of-stack is preserved. In
1393 ;; lapcode, we represent this by using a different opcode
1394 ;; (with the flag removed from the operand).
1397 ;; lap = ( [ (pc . (op . arg)) ]* )
1399 lap)
1405 ;; This addr is jumped to.
1412 ;; Remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1415 elt
1419 \f
1420 ;;; peephole optimizer
1426 byte-goto-if-not-nil-else-pop))
1430 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1431 byte-eq byte-not
1432 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1433 byte-interactive-p)
1434 ;; How about other side-effect-free-ops? Is it safe to move an
1435 ;; error invocation (such as from nth) out of an unwind-protect?
1436 ;; No, it is not, because the unwind-protect forms can alter
1437 ;; the inside of the object to which nth would apply.
1438 ;; For the same reason, byte-equal was deleted from this list.
1443 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1444 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1445 byte-point-min byte-following-char byte-preceding-char
1446 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1447 byte-current-buffer byte-stack-ref))
1452 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1453 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1454 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1456 byte-member byte-assq byte-quo byte-rem)
1457 byte-compile-side-effect-and-error-free-ops))
1459 ;; This crock is because of the way DEFVAR_BOOL variables work.
1460 ;; Consider the code
1461 ;;
1462 ;; (defun foo (flag)
1463 ;; (let ((old-pop-ups pop-up-windows)
1464 ;; (pop-up-windows flag))
1465 ;; (cond ((not (eq pop-up-windows old-pop-ups))
1466 ;; (setq old-pop-ups pop-up-windows)
1467 ;; ...))))
1468 ;;
1469 ;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1470 ;; something else. But if we optimize
1471 ;;
1472 ;; varref flag
1473 ;; varbind pop-up-windows
1474 ;; varref pop-up-windows
1475 ;; not
1476 ;; to
1477 ;; varref flag
1478 ;; dup
1479 ;; varbind pop-up-windows
1480 ;; not
1481 ;;
1482 ;; we break the program, because it will appear that pop-up-windows and
1483 ;; old-pop-ups are not EQ when really they are. So we have to know what
1484 ;; the BOOL variables are, and not perform this optimization on them.
1486 ;; The variable `byte-boolean-vars' is now primitive and updated
1487 ;; automatically by DEFVAR_BOOL.
1490 "Simple peephole optimizer. LAP is both modified and returned.
1491 If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
1493 lap1
1494 lap2
1497 rest tmp tmp2 tmp3
1499 byte-compile-side-effect-free-ops
1500 byte-compile-side-effect-and-error-free-ops)))
1505 keep-going nil)
1511 ;; You may notice that sequences like "dup varset discard" are
1512 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1513 ;; You may be tempted to change this; resist that temptation.
1515 ;; <side-effect-free> pop --> <deleted>
1516 ;; ...including:
1517 ;; const-X pop --> <deleted>
1518 ;; varref-X pop --> <deleted>
1519 ;; dup pop --> <deleted>
1520 ;;
1540 ;;
1541 ;; goto*-X X: --> X:
1542 ;;
1557 ;;
1558 ;; varset-X varref-X --> dup varset-X
1559 ;; varbind-X varref-X --> dup varbind-X
1560 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1561 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1562 ;; The latter two can enable other optimizations.
1563 ;;
1564 ;; For lexical variables, we could do the same
1565 ;; stack-set-X+1 stack-ref-X --> dup stack-set-X+2
1566 ;; but this is a very minor gain, since dup is stack-ref-0,
1567 ;; i.e. it's only better if X>5, and even then it comes
1568 ;; at the cost of an extra stack slot. Let's not bother.
1574 nil
1584 lap0 lap1 lap2 lap0 lap1
1592 ;; The stack depth gets locally increased, so we will
1593 ;; increase maxdepth in case depth = maxdepth here.
1594 ;; This can cause the third argument to byte-code to
1595 ;; be larger than necessary.
1597 ;;
1598 ;; dup varset-X discard --> varset-X
1599 ;; dup varbind-X discard --> varbind-X
1600 ;; dup stack-set-X discard --> stack-set-X-1
1601 ;; (the varbind variant can emerge from other optimizations)
1602 ;;
1606 byte-stack-set)))
1612 ;;
1613 ;; not goto-X-if-nil --> goto-X-if-non-nil
1614 ;; not goto-X-if-non-nil --> goto-X-if-nil
1615 ;;
1616 ;; it is wrong to do the same thing for the -else-pop variants.
1617 ;;
1621 lap1
1624 'byte-goto-if-not-nil
1628 'byte-goto-if-not-nil
1632 ;;
1633 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1634 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1635 ;;
1636 ;; it is wrong to do the same thing for the -else-pop variants.
1637 ;;
1645 lap0 lap1 lap2
1650 ;;
1651 ;; const goto-if-* --> whatever
1652 ;;
1655 ;; If the `byte-constant's cdr is not a cons cell, it has
1656 ;; to be an index into the constant pool); even though
1657 ;; it'll be a constant, that constant is not known yet
1658 ;; (it's typically a free variable of a closure, so will
1659 ;; only be known when the closure will be built at
1660 ;; run-time).
1663 byte-goto-if-nil-else-pop))
1667 lap0 lap1)
1672 lap0 lap1
1678 ;;
1679 ;; varref-X varref-X --> varref-X dup
1680 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1681 ;; stackref-X [dup ...] stackref-X+N --> stackref-X [dup ...] dup
1682 ;; We don't optimize the const-X variations on this here,
1683 ;; because that would inhibit some goto optimizations; we
1684 ;; optimize the const-X case after all other optimizations.
1685 ;;
1693 t)
1706 lap0 str lap0 lap0 str)))
1711 ;;
1712 ;; TAG1: TAG2: --> TAG1: <deleted>
1713 ;; (and other references to TAG2 are replaced with TAG1)
1714 ;;
1725 keep-going t))
1726 ;;
1727 ;; unused-TAG: --> <deleted>
1728 ;;
1734 keep-going t))
1735 ;;
1736 ;; goto ... --> goto <delete until TAG or end>
1737 ;; return ... --> return <delete until TAG or end>
1738 ;;
1744 str deleted)
1759 lap0
1765 tagstr lap0 tagstr))))
1768 ;;
1769 ;; <safe-op> unbind --> unbind <safe-op>
1770 ;; (this may enable other optimizations.)
1771 ;;
1778 ;;
1779 ;; varbind-X unbind-N --> discard unbind-(N-1)
1780 ;; save-excursion unbind-N --> unbind-(N-1)
1781 ;; save-restriction unbind-N --> unbind-(N-1)
1782 ;;
1785 byte-save-restriction))
1802 ;;
1803 ;; goto*-X ... X: goto-Y --> goto*-Y
1804 ;; goto-X ... X: return --> return
1805 ;;
1818 ;;
1819 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1820 ;; goto-*-else-pop X ... X: discard --> whatever
1821 ;;
1823 byte-goto-if-not-nil-else-pop))
1830 byte-goto-if-nil)
1832 byte-goto-if-not-nil))))
1838 ;; Get rid of the -else-pop's and jump one step further.
1847 ;;
1848 ;; const goto-X ... X: goto-if-* --> whatever
1849 ;; const goto-X ... X: discard --> whatever
1850 ;;
1863 byte-goto-if-not-nil-else-pop))))
1865 lap0 tmp2 lap0 tmp2)
1868 ;; Let next step fix the (const,goto-if*) sequence.
1873 ;; Jump one step further
1876 lap0 tmp2)
1883 ;;
1884 ;; X: varref-Y ... varset-Y goto-X -->
1885 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1886 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1887 ;; (This is so usual for while loops that it is worth handling).
1888 ;;
1889 ;; Here again, we could do it for stack-ref/stack-set, but
1890 ;; that's replacing a stack-ref-Y with a stack-ref-0, which
1891 ;; is a very minor improvement (if any), at the cost of
1892 ;; more stack use and more byte-code. Let's not do it.
1893 ;;
1901 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1906 lap1 lap2
1910 )
1915 ;;
1916 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1917 ;; (This can pull the loop test to the end of the loop)
1918 ;;
1925 byte-goto-if-nil-else-pop)))
1926 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1927 ;; lap0 lap1 (cdr lap0) (car tmp))
1936 byte-goto-if-not-nil-else-pop)
1938 byte-goto-if-nil-else-pop))))
1939 newtag)
1942 )
1945 ;; We can handle this case but not the -if-not-nil case,
1946 ;; because we won't know which non-nil constant to push.
1952 byte-goto-if-not-nil
1953 byte-goto-if-nil
1954 byte-goto-if-not-nil
1955 byte-goto byte-goto))))
1956 )
1958 )
1960 )
1961 ;; Cleanup stage:
1962 ;; Rebuild byte-compile-constants / byte-compile-variables.
1963 ;; Simple optimizations that would inhibit other optimizations if they
1964 ;; were done in the optimizing loop, and optimizations which there is no
1965 ;; need to do more than once.
1967 byte-compile-variables nil)
1977 byte-compile-constants)))
1980 byte-compile-variables)))))
1982 ;; const-C varset-X const-C --> const-C dup varset-X
1983 ;; const-C varbind-X const-C --> const-C dup varbind-X
1984 ;;
1990 lap0 lap1 lap0 lap0 lap1)
1994 ;;
1995 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1996 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1997 ;;
2000 tmp2 nil)
2010 ;;
2011 ;; unbind-N unbind-M --> unbind-(N+M)
2012 ;;
2021 ;;
2022 ;; stack-set-M [discard/discardN ...] --> discardN-preserve-tos
2023 ;; stack-set-M [discard/discardN ...] --> discardN
2024 ;;
2028 ;; See if enough discard operations follow to expose or
2029 ;; destroy the value stored by the stack-set.
2036 1
2040 ;; Do the optimization.
2044 ;; The value stored is the new TOS, so pop one more
2045 ;; value (to get rid of the old value) using the
2046 ;; TOS-preserving discard operator.
2047 'byte-discardN-preserve-tos
2048 ;; Otherwise, the value stored is lost, so just use a
2049 ;; normal discard.
2054 lap0 lap1))
2056 ;;
2057 ;; discard/discardN/discardN-preserve-tos-X discard/discardN-Y -->
2058 ;; discardN-(X+Y)
2059 ;;
2062 byte-discardN-preserve-tos))
2067 lap0 lap1
2074 ;;
2075 ;; discardN-preserve-tos-X discardN-preserve-tos-Y -->
2076 ;; discardN-preserve-tos-(X+Y)
2077 ;;
2084 ;;
2085 ;; discardN-preserve-tos return --> return
2086 ;; dup return --> return
2087 ;; stack-set-N return --> return ; where N is TOS-1
2088 ;;
2093 ;; The byte-code interpreter will pop the stack for us, so
2094 ;; we can just leave stuff on it.
2097 )
2100 lap)
2104 \f
2105 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
2106 ;; itself, compile some of its most used recursive functions (at load time).
2107 ;;
2118 byte-optimize-body
2119 byte-optimize-predicate
2120 byte-optimize-binary-predicate
2121 ;; Inserted some more than necessary, to speed it up.
2122 byte-optimize-form-code-walker
2123 byte-optimize-lapcode))))
2124 nil)
2126 ;;; byte-opt.el ends here