| blob | e1cc0db3f368c2a4f27b7a6c3d7ae4ac3c8266f6 |
1 ;;; byte-opt.el --- the optimization passes of the emacs-lisp byte compiler.
3 ;;; Copyright (c) 1991, 1994, 2000 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 'mocklisp-arguments 'binding-is-magic t)
54 ;; (put 'inhibit-quit 'binding-is-magic t)
55 ;; (put 'quit-flag 'binding-is-magic t)
56 ;; (put 't 'binding-is-magic t)
57 ;; (put 'nil 'binding-is-magic t)
58 ;; possibly also
59 ;; (put 'gc-cons-threshold 'binding-is-magic t)
60 ;; (put 'track-mouse 'binding-is-magic t)
61 ;; others?
62 ;;
63 ;; Simple defsubsts often produce forms like
64 ;; (let ((v1 (f1)) (v2 (f2)) ...)
65 ;; (FN v1 v2 ...))
66 ;; It would be nice if we could optimize this to
67 ;; (FN (f1) (f2) ...)
68 ;; but we can't unless FN is dynamically-safe (it might be dynamically
69 ;; referring to the bindings that the lambda arglist established.)
70 ;; One of the uncountable lossages introduced by dynamic scope...
71 ;;
72 ;; Maybe there should be a control-structure that says "turn on
73 ;; fast-and-loose type-assumptive optimizations here." Then when
74 ;; we see a form like (car foo) we can from then on assume that
75 ;; the variable foo is of type cons, and optimize based on that.
76 ;; But, this won't win much because of (you guessed it) dynamic
77 ;; scope. Anything down the stack could change the value.
78 ;; (Another reason it doesn't work is that it is perfectly valid
79 ;; to call car with a null argument.) A better approach might
80 ;; be to allow type-specification of the form
81 ;; (put 'foo 'arg-types '(float (list integer) dynamic))
82 ;; (put 'foo 'result-type 'bool)
83 ;; It should be possible to have these types checked to a certain
84 ;; degree.
85 ;;
86 ;; collapse common subexpressions
87 ;;
88 ;; It would be nice if redundant sequences could be factored out as well,
89 ;; when they are known to have no side-effects:
90 ;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
91 ;; but beware of traps like
92 ;; (cons (list x y) (list x y))
93 ;;
94 ;; Tail-recursion elimination is not really possible in Emacs Lisp.
95 ;; Tail-recursion elimination is almost always impossible when all variables
96 ;; have dynamic scope, but given that the "return" byteop requires the
97 ;; binding stack to be empty (rather than emptying it itself), there can be
98 ;; no truly tail-recursive Emacs Lisp functions that take any arguments or
99 ;; make any bindings.
100 ;;
101 ;; Here is an example of an Emacs Lisp function which could safely be
102 ;; byte-compiled tail-recursively:
103 ;;
104 ;; (defun tail-map (fn list)
105 ;; (cond (list
106 ;; (funcall fn (car list))
107 ;; (tail-map fn (cdr list)))))
108 ;;
109 ;; However, if there was even a single let-binding around the COND,
110 ;; it could not be byte-compiled, because there would be an "unbind"
111 ;; byte-op between the final "call" and "return." Adding a
112 ;; Bunbind_all byteop would fix this.
113 ;;
114 ;; (defun foo (x y z) ... (foo a b c))
115 ;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
116 ;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
117 ;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
118 ;;
119 ;; this also can be considered tail recursion:
120 ;;
121 ;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
122 ;; could generalize this by doing the optimization
123 ;; (goto X) ... X: (return) --> (return)
124 ;;
125 ;; But this doesn't solve all of the problems: although by doing tail-
126 ;; recursion elimination in this way, the call-stack does not grow, the
127 ;; binding-stack would grow with each recursive step, and would eventually
128 ;; overflow. I don't believe there is any way around this without lexical
129 ;; scope.
130 ;;
131 ;; Wouldn't it be nice if Emacs Lisp had lexical scope.
132 ;;
133 ;; Idea: the form (lexical-scope) in a file means that the file may be
134 ;; compiled lexically. This proclamation is file-local. Then, within
135 ;; that file, "let" would establish lexical bindings, and "let-dynamic"
136 ;; would do things the old way. (Or we could use CL "declare" forms.)
137 ;; We'd have to notice defvars and defconsts, since those variables should
138 ;; always be dynamic, and attempting to do a lexical binding of them
139 ;; should simply do a dynamic binding instead.
140 ;; But! We need to know about variables that were not necessarily defvarred
141 ;; in the file being compiled (doing a boundp check isn't good enough.)
142 ;; Fdefvar() would have to be modified to add something to the plist.
143 ;;
144 ;; A major disadvantage of this scheme is that the interpreter and compiler
145 ;; would have different semantics for files compiled with (dynamic-scope).
146 ;; Since this would be a file-local optimization, there would be no way to
147 ;; modify the interpreter to obey this (unless the loader was hacked
148 ;; in some grody way, but that's a really bad idea.)
150 ;; Other things to consider:
152 ;;;;; Associative math should recognize subcalls to identical function:
153 ;;;(disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
154 ;;;;; This should generate the same as (1+ x) and (1- x)
156 ;;;(disassemble (lambda (x) (cons (+ x 1) (- x 1))))
157 ;;;;; An awful lot of functions always return a non-nil value. If they're
158 ;;;;; error free also they may act as true-constants.
160 ;;;(disassemble (lambda (x) (and (point) (foo))))
161 ;;;;; When
162 ;;;;; - all but one arguments to a function are constant
163 ;;;;; - the non-constant argument is an if-expression (cond-expression?)
164 ;;;;; then the outer function can be distributed. If the guarding
165 ;;;;; condition is side-effect-free [assignment-free] then the other
166 ;;;;; arguments may be any expressions. Since, however, the code size
167 ;;;;; can increase this way they should be "simple". Compare:
169 ;;;(disassemble (lambda (x) (eq (if (point) 'a 'b) 'c)))
170 ;;;(disassemble (lambda (x) (if (point) (eq 'a 'c) (eq 'b 'c))))
172 ;;;;; (car (cons A B)) -> (progn B A)
173 ;;;(disassemble (lambda (x) (car (cons (foo) 42))))
175 ;;;;; (cdr (cons A B)) -> (progn A B)
176 ;;;(disassemble (lambda (x) (cdr (cons 42 (foo)))))
178 ;;;;; (car (list A B ...)) -> (progn B ... A)
179 ;;;(disassemble (lambda (x) (car (list (foo) 42 (bar)))))
181 ;;;;; (cdr (list A B ...)) -> (progn A (list B ...))
182 ;;;(disassemble (lambda (x) (cdr (list 42 (foo) (bar)))))
185 ;;; Code:
200 arg)
216 c
218 args)))))
226 \f
227 ;;; byte-compile optimizers to support inlining
232 "byte-optimize-handler for the `inline' special-form."
245 sexp)))
249 ;; Splice the given lap code into the current instruction stream.
250 ;; If it has any labels in it, you're responsible for making sure there
251 ;; are no collisions, and that byte-compile-tag-number is reasonable
252 ;; after this is spliced in. The provided list is destroyed.
264 name)
265 form)
266 ;; else
286 ;; Give up on inlining.
287 form))))))
289 ;;; ((lambda ...) ...)
290 ;;;
301 optionalp restp
302 bindings)
309 ;; ok, I'll let this slide because funcall_lambda() does...
310 ;; (if optionalp (error "multiple &optional keywords in %s" name))
316 ;; ...but it is by no stretch of the imagination a reasonable
317 ;; thing that funcall_lambda() allows (&rest x y) and
318 ;; (&rest x &optional y) in arglists.
327 bindings)
328 values nil))
334 bindings)
342 form)
349 newform)))))
351 \f
352 ;;; implementing source-level optimizers
355 ;;
356 ;; For normal function calls, We can just mapcar the optimizer the cdr. But
357 ;; we need to have special knowledge of the syntax of the special forms
358 ;; like let and defun (that's why they're special forms :-). (Actually,
359 ;; the important aspect is that they are subrs that don't evaluate all of
360 ;; their args.)
361 ;;
363 tmp)
369 form))
374 ;; map (quote nil) to nil to simplify optimizer logic.
375 ;; map quoted constants to nil if for-effect (just because).
378 form))
383 ;; recursively enter the optimizer for the bindings and body
384 ;; of a let or let*. This for depth-firstness: forms that
385 ;; are more deeply nested are optimized first.
390 binding
407 clause))
410 ;; as an extra added bonus, this simplifies (progn <x>) --> <x>
429 ;; those subrs which have an implicit progn; it's not quite good
430 ;; enough to treat these like normal function calls.
431 ;; This can turn (save-excursion ...) into (save-excursion) which
432 ;; will be optimized away in the lap-optimize pass.
436 ;; this is just like the above, except for the first argument.
450 ;; take forms off the back until we can't any more.
451 ;; In the future it could conceivably be a problem that the
452 ;; subexpressions of these forms are optimized in the reverse
453 ;; order, but it's ok for now.
459 for-effect))))
471 nil)
474 condition-case save-window-excursion))
475 ;; These forms are compiled as constants or by breaking out
476 ;; all the subexpressions and compiling them separately.
477 form)
480 ;; the "protected" part of an unwind-protect is compiled (and thus
481 ;; optimized) as a top-level form, so don't do it here. But the
482 ;; non-protected part has the same for-effect status as the
483 ;; unwind-protect itself. (The protected part is always for effect,
484 ;; but that isn't handled properly yet.)
490 ;; the body of a catch is compiled (and thus optimized) as a
491 ;; top-level form, so don't do it here. The tag is never
492 ;; for-effect. The body should have the same for-effect status
493 ;; as the catch form itself, but that isn't handled properly yet.
498 ;; If optimization is on, this is the only place that macros are
499 ;; expanded. If optimization is off, then macroexpansion happens
500 ;; in byte-compile-form. Otherwise, the macros are already expanded
501 ;; by the time that is reached.
504 byte-compile-macro-environment))))
507 ;; Support compiler macros as in cl.el.
519 form)
527 nil)))
529 ;; appending a nil here might not be necessary, but it can't hurt.
534 ;; Otherwise, no args can be considered to be for-effect,
535 ;; even if the called function is for-effect, because we
536 ;; don't know anything about that function.
541 "The source-level pass of the optimizer."
542 ;;
543 ;; First, optimize all sub-forms of this one.
545 ;;
546 ;; after optimizing all subforms, optimize this form until it doesn't
547 ;; optimize any further. This means that some forms will be passed through
548 ;; the optimizer many times, but that's necessary to make the for-effect
549 ;; processing do as much as possible.
550 ;;
555 ;; we don't have any of these yet, but we might.
560 ;; (if (equal form new) (error "bogus optimizer -- %s" opt))
563 new)
564 form)))
568 ;; optimize the cdr of a progn or implicit progn; all forms is a list of
569 ;; forms, all but the last of which are optimized with the assumption that
570 ;; they are being called for effect. the last is for-effect as well if
571 ;; all-for-effect is true. returns a new list of forms.
574 fe new)
583 \f
584 ;;; some source-level optimizers
585 ;;;
586 ;;; when writing optimizers, be VERY careful that the optimizer returns
587 ;;; something not EQ to its argument if and ONLY if it has made a change.
588 ;;; This implies that you cannot simply destructively modify the list;
589 ;;; you must return something not EQ to it if you make an optimization.
590 ;;;
591 ;;; It is now safe to optimize code such that it introduces new bindings.
593 ;; I'd like this to be a defsubst, but let's not be self-referential...
595 ;; Returns non-nil if FORM is a non-nil constant.
601 ;; If the function is being called with constant numeric args,
602 ;; evaluate as much as possible at compile-time. This optimizer
603 ;; assumes that the function is associative, like + or *.
621 form)))
623 ;; If the function is being called with constant numeric args,
624 ;; evaluate as much as possible at compile-time. This optimizer
625 ;; assumes that the function satisfies
626 ;; (op x1 x2 ... xn) == (op ...(op (op x1 x2) x3) ...xn)
627 ;; like - and /.
631 form
639 constant))))
641 ;;(defun byte-optimize-associative-two-args-math (form)
642 ;; (setq form (byte-optimize-associative-math form))
643 ;; (if (consp form)
644 ;; (byte-optimize-two-args-left form)
645 ;; form))
647 ;;(defun byte-optimize-nonassociative-two-args-math (form)
648 ;; (setq form (byte-optimize-nonassociative-math form))
649 ;; (if (consp form)
650 ;; (byte-optimize-two-args-right form)
651 ;; form))
656 ;; Collect all the constants from FORM, after the STARTth arg,
657 ;; and apply FUN to them to make one argument at the end.
658 ;; For functions that can handle floats, that optimization
659 ;; can be incorrect because reordering can cause an overflow
660 ;; that would otherwise be avoided by encountering an arg that is a float.
661 ;; We avoid this problem by (1) not moving float constants and
662 ;; (2) not moving anything if it would cause an overflow.
664 ;; Merge all FORM's constants from number START, call FUN on them
665 ;; and put the result at the end.
668 ;; t means we must check for overflow.
679 ;; If necessary, check now for overflow
680 ;; that might be caused by reordering.
682 ;; We have overflow if the result of doing the arithmetic
683 ;; on floats is not even close to the result
684 ;; of doing it on integers.
691 form))
696 ;;(setq form (byte-optimize-associative-two-args-math form))
701 ;;; It is not safe to delete the function entirely
702 ;;; (actually, it would be safe if we know the sole arg
703 ;;; is not a marker).
704 ;; ((null (cdr (cdr form))) (nth 1 form))
708 form))
712 ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
722 other)))
726 ;; Put constants at the end, except the last constant.
728 ;; Now only first and last element can be a number.
731 ;; (- x y ... 0) --> (- x y ...)
738 ;; If form is (- CONST foo... CONST), merge first and last.
743 ;;; It is not safe to delete the function entirely
744 ;;; (actually, it would be safe if we know the sole arg
745 ;;; is not a marker).
746 ;;; (if (eq (nth 2 form) 0)
747 ;;; (nth 1 form) ; (- x 0) --> x
752 form))
753 ;;; )
754 )
758 ;; If there is a constant in FORM, it is now the last element.
760 ;;; It is not safe to delete the function entirely
761 ;;; (actually, it would be safe if we know the sole arg
762 ;;; is not a marker or if it appears in other arithmetic).
763 ;;; ((null (cdr (cdr form))) (nth 1 form))
795 last nil))))
797 ;;; ((null (cdr (cdr form)))
798 ;;; (nth 1 form))
826 ;; This can enable some lapcode optimizations.
828 form))
840 form)))
848 form))
892 ;; I'm not convinced that this is necessary. Doesn't the optimizer loop
893 ;; take care of this? - Jamie
894 ;; I think this may some times be necessary to reduce ie (quote 5) to 5,
895 ;; so arithmetic optimizers recognize the numeric constant. - Hallvard
901 form
914 ;; Simplify if less than 2 args.
915 ;; if there is a literal nil in the args to `and', throw it and following
916 ;; forms away, and surround the `and' with (progn ... nil).
925 nil))
931 ;; Throw away nil's, and simplify if less than 2 args.
932 ;; If there is a literal non-nil constant in the args to `or', throw away all
933 ;; following forms.
946 ;; if any clauses have a literal nil as their test, throw them away.
947 ;; if any clause has a literal non-nil constant as its test, throw
948 ;; away all following clauses.
950 ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
969 ;;
970 ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
978 form))
979 form))
982 ;; (if <true-constant> <then> <else...>) ==> <then>
983 ;; (if <false-constant> <then> <else...>) ==> (progn <else...>)
984 ;; (if <test> nil <else...>) ==> (if (not <test>) (progn <else...>))
985 ;; (if <test> <then> nil) ==> (if <test> <then>)
996 form))
999 ;; Don't make a double negative;
1000 ;; instead, take away the one that is there.
1013 form))
1021 ;; byte-compile-negation-optimizer lives in bytecomp.el
1028 ;; (funcall (lambda ...) ...) ==> ((lambda ...) ...)
1029 ;; (funcall foo ...) ==> (foo ...)
1033 form)))
1036 ;; If the last arg is a literal constant, turn this into a funcall.
1037 ;; The funcall optimizer can then transform (funcall 'foo ...) -> (foo ...).
1047 "Last arg to apply can't be a literal atom: `%s'"
1049 nil))
1050 form)))
1060 ;; No bindings
1063 form)
1064 ;; The body is nil
1089 form)))
1101 form)))
1103 ;; Avoid having to write forward-... with a negative arg for speed.
1129 \f
1130 ;;; enumerating those functions which need not be called if the returned
1131 ;;; value is not used. That is, something like
1132 ;;; (progn (list (something-with-side-effects) (yow))
1133 ;;; (foo))
1134 ;;; may safely be turned into
1135 ;;; (progn (progn (something-with-side-effects) (yow))
1136 ;;; (foo))
1137 ;;; Further optimizations will turn (progn (list 1 2 3) 'foo) into 'foo.
1139 ;;; I wonder if I missed any :-\)
1142 assoc assq
1143 boundp buffer-file-name buffer-local-variables buffer-modified-p
1144 buffer-substring
1145 capitalize car-less-than-car car cdr ceiling char-after char-before
1146 concat coordinates-in-window-p
1147 char-width copy-marker cos count-lines
1148 default-boundp default-value documentation downcase
1149 elt exp expt fboundp featurep
1150 file-directory-p file-exists-p file-locked-p file-name-absolute-p
1151 file-newer-than-file-p file-readable-p file-symlink-p file-writable-p
1152 float floor format frame-visible-p
1153 get gethash get-buffer get-buffer-window getenv get-file-buffer
1154 hash-table-count
1155 int-to-string
1156 keymap-parent
1157 length local-variable-if-set-p local-variable-p log log10 logand
1158 logb logior lognot logxor lsh
1159 marker-buffer max member memq min mod
1160 next-window nth nthcdr number-to-string
1161 parse-colon-path prefix-numeric-value previous-window propertize
1162 radians-to-degrees rassq regexp-quote reverse round
1164 string-to-int string-to-number substring symbol-function symbol-plist
1165 symbol-value
1166 tan unibyte-char-to-multibyte upcase user-variable-p vconcat
1167 window-buffer window-dedicated-p window-edges window-height
1168 window-hscroll window-minibuffer-p window-width
1169 zerop))
1172 bobp bolp buffer-end buffer-list buffer-size buffer-string bufferp
1173 car-safe case-table-p cdr-safe char-or-string-p commandp cons consp
1174 current-buffer current-global-map current-indentation
1175 current-local-map current-minor-mode-maps
1176 dot dot-marker eobp eolp eq equal eventp
1177 floatp following-char framep
1178 get-largest-window get-lru-window
1179 hash-table-p
1180 identity ignore integerp integer-or-marker-p interactive-p
1181 invocation-directory invocation-name
1182 keymapp
1183 line-beginning-position line-end-position list listp
1184 make-marker mark mark-marker markerp memory-limit minibuffer-window
1185 mouse-movement-p
1186 natnump nlistp not null number-or-marker-p numberp
1187 one-window-p overlayp
1188 point point-marker point-min point-max preceding-char processp
1189 recent-keys recursion-depth
1190 selected-frame selected-window sequencep stringp subrp symbolp
1191 standard-case-table standard-syntax-table syntax-table-p
1192 this-command-keys this-command-keys-vector this-single-command-keys
1193 this-single-command-raw-keys
1194 user-full-name user-login-name user-original-login-name
1195 user-real-login-name user-real-uid user-uid
1196 vector vectorp visible-frame-list
1197 window-configuration-p window-live-p windowp)))
1204 nil)
1208 ;; form is (byte-code "..." [...] n)
1214 byte-compile-maxdepth))
1219 \f
1223 ;;; This function extracts the bitfields from variable-length opcodes.
1224 ;;; Originally defined in disass.el (which no longer uses it.)
1227 "Don't call this!"
1228 ;; fetch and return the offset for the current opcode.
1229 ;; return NIL if this opcode has no offset
1230 ;; OP, PTR and BYTES are used and set dynamically
1261 ;;; This de-compiler is used for inline expansion of compiled functions,
1262 ;;; and by the disassembler.
1263 ;;;
1264 ;;; This list contains numbers, which are pc values,
1265 ;;; before each instruction.
1267 "Turns BYTECODE into lapcode, referring to CONSTVEC."
1273 ;; As byte-decompile-bytecode, but updates
1274 ;; byte-compile-{constants, variables, tag-number}.
1275 ;; If MAKE-SPLICEABLE is true, then `return' opcodes are replaced
1276 ;; with `goto's destined for the end of the code.
1277 ;; That is for use by the compiler.
1278 ;; If MAKE-SPLICEABLE is nil, we are being called for the disassembler.
1279 ;; In that case, we put a pc value into the list
1280 ;; before each insn (or its label).
1284 lap tmp
1285 endtag
1291 optr ptr
1295 ;; it's a pc
1301 tags)))))))
1312 byte-compile-variables)))))))
1319 ;; lap = ( [ (pc . (op . arg)) ]* )
1321 lap))
1323 ;; take off the dummy nil op that we replaced a trailing "return" with.
1328 ;; this addr is jumped to
1339 ;; remove addrs, lap = ( [ (op . arg) | (TAG tagno) ]* )
1342 elt
1346 \f
1347 ;;; peephole optimizer
1353 byte-goto-if-not-nil-else-pop))
1357 byte-symbolp byte-consp byte-stringp byte-listp byte-numberp byte-integerp
1358 byte-eq byte-not
1359 byte-cons byte-list1 byte-list2 ; byte-list3 byte-list4
1360 byte-interactive-p)
1361 ;; How about other side-effect-free-ops? Is it safe to move an
1362 ;; error invocation (such as from nth) out of an unwind-protect?
1363 ;; No, it is not, because the unwind-protect forms can alter
1364 ;; the inside of the object to which nth would apply.
1365 ;; For the same reason, byte-equal was deleted from this list.
1370 byte-integerp byte-numberp byte-eq byte-equal byte-not byte-car-safe
1371 byte-cdr-safe byte-cons byte-list1 byte-list2 byte-point byte-point-max
1372 byte-point-min byte-following-char byte-preceding-char
1373 byte-current-column byte-eolp byte-eobp byte-bolp byte-bobp
1374 byte-current-buffer byte-interactive-p))
1379 byte-symbol-value byte-get byte-concat2 byte-concat3 byte-sub1 byte-add1
1380 byte-eqlsign byte-gtr byte-lss byte-leq byte-geq byte-diff byte-negate
1381 byte-plus byte-max byte-min byte-mult byte-char-after byte-char-syntax
1383 byte-member byte-assq byte-quo byte-rem)
1384 byte-compile-side-effect-and-error-free-ops))
1386 ;;; This crock is because of the way DEFVAR_BOOL variables work.
1387 ;;; Consider the code
1388 ;;;
1389 ;;; (defun foo (flag)
1390 ;;; (let ((old-pop-ups pop-up-windows)
1391 ;;; (pop-up-windows flag))
1392 ;;; (cond ((not (eq pop-up-windows old-pop-ups))
1393 ;;; (setq old-pop-ups pop-up-windows)
1394 ;;; ...))))
1395 ;;;
1396 ;;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
1397 ;;; something else. But if we optimize
1398 ;;;
1399 ;;; varref flag
1400 ;;; varbind pop-up-windows
1401 ;;; varref pop-up-windows
1402 ;;; not
1403 ;;; to
1404 ;;; varref flag
1405 ;;; dup
1406 ;;; varbind pop-up-windows
1407 ;;; not
1408 ;;;
1409 ;;; we break the program, because it will appear that pop-up-windows and
1410 ;;; old-pop-ups are not EQ when really they are. So we have to know what
1411 ;;; the BOOL variables are, and not perform this optimization on them.
1413 ;;; The variable `byte-boolean-vars' is now primitive and updated
1414 ;;; automatically by DEFVAR_BOOL.
1417 "Simple peephole optimizer. LAP is both modified and returned."
1419 lap1 off1
1420 lap2 off2
1423 rest tmp tmp2 tmp3
1425 byte-compile-side-effect-free-ops
1426 byte-compile-side-effect-and-error-free-ops)))
1431 keep-going nil)
1437 ;; You may notice that sequences like "dup varset discard" are
1438 ;; optimized but sequences like "dup varset TAG1: discard" are not.
1439 ;; You may be tempted to change this; resist that temptation.
1441 ;; <side-effect-free> pop --> <deleted>
1442 ;; ...including:
1443 ;; const-X pop --> <deleted>
1444 ;; varref-X pop --> <deleted>
1445 ;; dup pop --> <deleted>
1446 ;;
1466 ;;
1467 ;; goto*-X X: --> X:
1468 ;;
1483 ;;
1484 ;; varset-X varref-X --> dup varset-X
1485 ;; varbind-X varref-X --> dup varbind-X
1486 ;; const/dup varset-X varref-X --> const/dup varset-X const/dup
1487 ;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
1488 ;; The latter two can enable other optimizations.
1489 ;;
1495 nil
1505 lap0 lap1 lap2 lap0 lap1
1513 ;; The stack depth gets locally increased, so we will
1514 ;; increase maxdepth in case depth = maxdepth here.
1515 ;; This can cause the third argument to byte-code to
1516 ;; be larger than necessary.
1518 ;;
1519 ;; dup varset-X discard --> varset-X
1520 ;; dup varbind-X discard --> varbind-X
1521 ;; (the varbind variant can emerge from other optimizations)
1522 ;;
1530 ;;
1531 ;; not goto-X-if-nil --> goto-X-if-non-nil
1532 ;; not goto-X-if-non-nil --> goto-X-if-nil
1533 ;;
1534 ;; it is wrong to do the same thing for the -else-pop variants.
1535 ;;
1540 lap1
1543 'byte-goto-if-not-nil
1547 'byte-goto-if-not-nil
1551 ;;
1552 ;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
1553 ;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
1554 ;;
1555 ;; it is wrong to do the same thing for the -else-pop variants.
1556 ;;
1564 lap0 lap1 lap2
1569 ;;
1570 ;; const goto-if-* --> whatever
1571 ;;
1579 lap0 lap1)
1592 ;;
1593 ;; varref-X varref-X --> varref-X dup
1594 ;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
1595 ;; We don't optimize the const-X variations on this here,
1596 ;; because that would inhibit some goto optimizations; we
1597 ;; optimize the const-X case after all other optimizations.
1598 ;;
1604 t)
1614 lap0 str lap0 lap0 str)))
1619 ;;
1620 ;; TAG1: TAG2: --> TAG1: <deleted>
1621 ;; (and other references to TAG2 are replaced with TAG1)
1622 ;;
1633 keep-going t))
1634 ;;
1635 ;; unused-TAG: --> <deleted>
1636 ;;
1642 keep-going t))
1643 ;;
1644 ;; goto ... --> goto <delete until TAG or end>
1645 ;; return ... --> return <delete until TAG or end>
1646 ;;
1652 str deleted)
1667 lap0
1673 tagstr lap0 tagstr))))
1676 ;;
1677 ;; <safe-op> unbind --> unbind <safe-op>
1678 ;; (this may enable other optimizations.)
1679 ;;
1686 ;;
1687 ;; varbind-X unbind-N --> discard unbind-(N-1)
1688 ;; save-excursion unbind-N --> unbind-(N-1)
1689 ;; save-restriction unbind-N --> unbind-(N-1)
1690 ;;
1693 byte-save-restriction))
1710 ;;
1711 ;; goto*-X ... X: goto-Y --> goto*-Y
1712 ;; goto-X ... X: return --> return
1713 ;;
1726 ;;
1727 ;; goto-*-else-pop X ... X: goto-if-* --> whatever
1728 ;; goto-*-else-pop X ... X: discard --> whatever
1729 ;;
1731 byte-goto-if-not-nil-else-pop))
1738 byte-goto-if-nil)
1740 byte-goto-if-not-nil))))
1746 ;; Get rid of the -else-pop's and jump one step further.
1755 ;;
1756 ;; const goto-X ... X: goto-if-* --> whatever
1757 ;; const goto-X ... X: discard --> whatever
1758 ;;
1770 byte-goto-if-not-nil-else-pop)))
1772 lap0 tmp2 lap0 tmp2)
1775 ;; Let next step fix the (const,goto-if*) sequence.
1778 ;; Jump one step further
1781 lap0 tmp2)
1788 ;;
1789 ;; X: varref-Y ... varset-Y goto-X -->
1790 ;; X: varref-Y Z: ... dup varset-Y goto-Z
1791 ;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
1792 ;; (This is so usual for while loops that it is worth handling).
1793 ;;
1801 ;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
1806 lap1 lap2
1810 )
1815 ;;
1816 ;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
1817 ;; (This can pull the loop test to the end of the loop)
1818 ;;
1825 byte-goto-if-nil-else-pop)))
1826 ;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
1827 ;; lap0 lap1 (cdr lap0) (car tmp))
1836 byte-goto-if-not-nil-else-pop)
1838 byte-goto-if-nil-else-pop))))
1839 newtag)
1842 )
1845 ;; We can handle this case but not the -if-not-nil case,
1846 ;; because we won't know which non-nil constant to push.
1852 byte-goto-if-not-nil
1853 byte-goto-if-nil
1854 byte-goto-if-not-nil
1855 byte-goto byte-goto))))
1856 )
1858 )
1860 )
1861 ;; Cleanup stage:
1862 ;; Rebuild byte-compile-constants / byte-compile-variables.
1863 ;; Simple optimizations that would inhibit other optimizations if they
1864 ;; were done in the optimizing loop, and optimizations which there is no
1865 ;; need to do more than once.
1867 byte-compile-variables nil)
1876 byte-compile-variables)))
1879 byte-compile-constants)))))
1881 ;; const-C varset-X const-C --> const-C dup varset-X
1882 ;; const-C varbind-X const-C --> const-C dup varbind-X
1883 ;;
1889 lap0 lap1 lap0 lap0 lap1)
1893 ;;
1894 ;; const-X [dup/const-X ...] --> const-X [dup ...] dup
1895 ;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
1896 ;;
1899 tmp2 nil)
1909 ;;
1910 ;; unbind-N unbind-M --> unbind-(N+M)
1911 ;;
1920 )
1923 lap)
1927 \f
1928 ;; To avoid "lisp nesting exceeds max-lisp-eval-depth" when this file compiles
1929 ;; itself, compile some of its most used recursive functions (at load time).
1930 ;;
1941 byte-optimize-body
1942 byte-optimize-predicate
1943 byte-optimize-binary-predicate
1944 ;; Inserted some more than necessary, to speed it up.
1945 byte-optimize-form-code-walker
1946 byte-optimize-lapcode))))
1947 nil)
1949 ;;; byte-opt.el ends here