;;; Copyright (c) 1991, 1994 Free Software Foundation, Inc.
-;; Author: Jamie Zawinski <jwz@jwz.org>
-;; Hallvard Furuseth <hbf@ulrik.uio.no>
+;; Authors: Jamie Zawinski <jwz@jwz.org>
+;; Hallvard Furuseth <hbf@ulrik.uio.no>
+;; Martin Buchholz <martin@xemacs.org>
;; Keywords: internal
;; This file is part of XEmacs.
(progn
;; (if (equal form new) (error "bogus optimizer -- %s" opt))
(byte-compile-log " %s\t==>\t%s" form new)
- (setq new (byte-optimize-form new for-effect))
- new)
+ (byte-optimize-form new for-effect))
form)))
(list (apply fun (nreverse constants)))))))))
form))
+;;; It is not safe to optimize calls to arithmetic ops with one arg
+;;; away entirely (actually, it would be safe if we know the sole arg
+;;; is not a marker or if it appears in other arithmetic).
+
+;;; But this degree of paranoia is normally unjustified, so optimize unless
+;;; the user has done (declaim (safety 3)). Implemented in bytecomp.el.
+
(defun byte-optimize-plus (form)
- (setq form (byte-optimize-delay-constants-math form 1 '+))
- (if (memq 0 form) (setq form (delq 0 (copy-sequence form))))
- ;;(setq form (byte-optimize-associative-two-args-math form))
-
- (case (length (cdr form))
- ((0) ; (+)
- (condition-case ()
- (eval form)
- (error form)))
-
- ;; It is not safe to delete the function entirely
- ;; (actually, it would be safe if we knew the sole arg
- ;; is not a marker).
- ;; ((1)
- ;; (nth 1 form))
-
- ((2) ; (+ x y)
- (byte-optimize-predicate
- (cond
- ;; `add1' and `sub1' are a marginally fewer instructions
- ;; than `plus' and `minus', so use them when possible.
- ((eq (nth 1 form) 1) `(1+ ,(nth 2 form))) ; (+ 1 x) --> (1+ x)
- ((eq (nth 2 form) 1) `(1+ ,(nth 1 form))) ; (+ x 1) --> (1+ x)
- ((eq (nth 1 form) -1) `(1- ,(nth 2 form))) ; (+ -1 x) --> (1- x)
- ((eq (nth 2 form) -1) `(1- ,(nth 1 form))) ; (+ x -1) --> (1- x)
- (t form))))
+ (byte-optimize-predicate (byte-optimize-delay-constants-math form 1 '+)))
+
+(defun byte-optimize-multiply (form)
+ (setq form (byte-optimize-delay-constants-math form 1 '*))
+ ;; If there is a constant integer in FORM, it is now the last element.
+ (case (car (last form))
+ ;; (* x y 0) --> (progn x y 0)
+ (0 (cons 'progn (cdr form)))
(t (byte-optimize-predicate form))))
(defun byte-optimize-minus (form)
- ;; Put constants at the end, except the last constant.
+ ;; Put constants at the end, except the first arg.
(setq form (byte-optimize-delay-constants-math form 2 '+))
- ;; Now only first and last element can be an integer.
- (let ((last (last (nthcdr 3 form))))
- (cond ((eq 0 last)
- ;; (- x y ... 0) --> (- x y ...)
- (setq form (copy-sequence form))
- (setcdr (cdr (cdr form)) (delq 0 (nthcdr 3 form))))
- ;; If form is (- CONST foo... CONST), merge first and last.
- ((and (numberp (nth 1 form))
- (numberp last))
- (setq form (nconc (list '- (- (nth 1 form) last) (nth 2 form))
- (delq last (copy-sequence (nthcdr 3 form))))))))
-
- (case (length (cdr form))
- ((0) ; (-)
- (condition-case ()
- (eval form)
- (error form)))
-
- ;; It is not safe to delete the function entirely
- ;; (actually, it would be safe if we knew the sole arg
- ;; is not a marker).
- ;; ((1)
- ;; (nth 1 form)
-
- ((2) ; (+ x y)
- (byte-optimize-predicate
- (cond
- ;; `add1' and `sub1' are a marginally fewer instructions than `plus'
- ;; and `minus', so use them when possible.
- ((eq (nth 2 form) 1) `(1- ,(nth 1 form))) ; (- x 1) --> (1- x)
- ((eq (nth 2 form) -1) `(1+ ,(nth 1 form))) ; (- x -1) --> (1+ x)
- ((eq (nth 1 form) 0) `(- ,(nth 2 form))) ; (- 0 x) --> (- x)
- (t form))))
+ ;; Now only the first and last args can be integers.
+ (let ((last (car (last (nthcdr 3 form)))))
+ (cond
+ ;; If form is (- CONST foo... CONST), merge first and last.
+ ((and (numberp (nth 1 form)) (numberp last))
+ (decf (nth 1 form) last)
+ (butlast form))
- (t (byte-optimize-predicate form))))
+ ;; (- 0 x ...) --> (- (- x) ...)
+ ((and (eq 0 (nth 1 form)) (>= (length form) 3))
+ `(- (- ,(nth 2 form)) ,@(nthcdr 3 form)))
-(defun byte-optimize-multiply (form)
- (setq form (byte-optimize-delay-constants-math form 1 '*))
- ;; If there is a constant integer in FORM, it is now the last element.
- (cond ((null (cdr form)) 1)
-;;; It is not safe to delete the function entirely
-;;; (actually, it would be safe if we know the sole arg
-;;; is not a marker or if it appears in other arithmetic).
-;;; ((null (cdr (cdr form))) (nth 1 form))
- ((let ((last (last form)))
- (byte-optimize-predicate
- (cond ((eq 0 last) (cons 'progn (cdr form)))
- ((eq 1 last) (delq 1 (copy-sequence form)))
- ((eq -1 last) (list '- (delq -1 (copy-sequence form))))
- ((and (eq 2 last)
- (memq t (mapcar 'symbolp (cdr form))))
- (prog1 (setq form (delq 2 (copy-sequence form)))
- (while (not (symbolp (car (setq form (cdr form))))))
- (setcar form (list '+ (car form) (car form)))))
- (form)))))))
+ (t (byte-optimize-predicate form)))))
(defun byte-optimize-divide (form)
+ ;; Put constants at the end, except the first arg.
(setq form (byte-optimize-delay-constants-math form 2 '*))
- ;; If there is a constant integer in FORM, it is now the last element.
- (let ((last (last (cdr (cdr form)))))
- (if (numberp last)
- (cond ((= (length form) 3)
- (if (and (numberp (nth 1 form))
- (not (zerop last))
- (condition-case nil
- (/ (nth 1 form) last)
- (error nil)))
- (setq form (list 'progn (/ (nth 1 form) last)))))
- ((= last 1)
- (setq form (butlast form)))
- ((numberp (nth 1 form))
- (setq form (cons (car form)
- (cons (/ (nth 1 form) last)
- (butlast (cdr (cdr form)))))
- last nil))))
+ ;; Now only the first and last args can be integers.
+ (let ((last (car (last (nthcdr 3 form)))))
(cond
-;;; ((null (cdr (cdr form)))
-;;; (nth 1 form))
+ ;; If form is (/ CONST foo... CONST), merge first and last.
+ ((and (numberp (nth 1 form)) (numberp last))
+ (condition-case nil
+ (cons (nth 0 form)
+ (cons (/ (nth 1 form) last)
+ (butlast (cdr (cdr form)))))
+ (error form)))
+
+ ;; (/ 0 x y) --> (progn x y 0)
((eq (nth 1 form) 0)
(append '(progn) (cdr (cdr form)) '(0)))
- ((eq last -1)
- (list '- (if (nthcdr 3 form)
- (butlast form)
- (nth 1 form))))
- (form))))
+
+ ;; We don't have to check for divide-by-zero because `/' does.
+ (t (byte-optimize-predicate form)))))
(defun byte-optimize-logmumble (form)
(setq form (byte-optimize-delay-constants-math form 1 (car form)))
(setq ok (byte-compile-constp (car rest))
rest (cdr rest)))
(if ok
- (condition-case ()
+ (condition-case err
(list 'quote (eval form))
- (error form))
+ (error
+ (byte-compile-warn "evaluating %s: %s" form err)
+ form))
form)))
(defun byte-optimize-identity (form)
(put '* 'byte-optimizer 'byte-optimize-multiply)
(put '- 'byte-optimizer 'byte-optimize-minus)
(put '/ 'byte-optimizer 'byte-optimize-divide)
+(put '% 'byte-optimizer 'byte-optimize-predicate)
(put 'max 'byte-optimizer 'byte-optimize-associative-math)
(put 'min 'byte-optimizer 'byte-optimize-associative-math)
(put 'if 'byte-optimizer 'byte-optimize-if)
(put 'while 'byte-optimizer 'byte-optimize-while)
-;; Remove any reason for avoiding `char-before'.
-(defun byte-optimize-char-before (form)
- `(char-after (1- ,(or (nth 1 form) '(point))) ,@(cdr (cdr form))))
+;; The supply of bytecodes is small and constrained by backward compatibility.
+;; Several functions have byte-coded versions and hence are very efficient.
+;; Related functions which can be expressed in terms of the byte-coded
+;; ones should be transformed into bytecoded calls for efficiency.
+;; This is especially the case for functions with a backward- and
+;; forward- version, but with a bytecode only for the forward one.
-(put 'char-before 'byte-optimizer 'byte-optimize-char-before)
+;; Some programmers have hand-optimized calls like (backward-char)
+;; into the call (forward-char -1).
+;; But it's so much nicer for the byte-compiler to do this automatically!
+
+;; (char-before) ==> (char-after (1- (point)))
+(put 'char-before 'byte-optimizer 'byte-optimize-char-before)
+(defun byte-optimize-char-before (form)
+ `(char-after
+ ,(cond
+ ((null (nth 1 form))
+ '(1- (point)))
+ ((equal '(point) (nth 1 form))
+ '(1- (point)))
+ (t `(1- (or ,(nth 1 form) (point)))))
+ ,@(cdr (cdr form))))
+
+;; (backward-char n) ==> (forward-char (- n))
+(put 'backward-char 'byte-optimizer 'byte-optimize-backward-char)
+(defun byte-optimize-backward-char (form)
+ `(forward-char
+ ,(typecase (nth 1 form)
+ (null -1)
+ (integer (- (nth 1 form)))
+ (t `(- (or ,(nth 1 form) 1))))
+ ,@(cdr (cdr form))))
+
+;; (backward-word n) ==> (forward-word (- n))
+(put 'backward-word 'byte-optimizer 'byte-optimize-backward-word)
+(defun byte-optimize-backward-word (form)
+ `(forward-word
+ ,(typecase (nth 1 form)
+ (null -1)
+ (integer (- (nth 1 form)))
+ (t `(- (or ,(nth 1 form) 1))))
+ ,@(cdr (cdr form))))
+
+;; The following would be a valid optimization of the above kind, but
+;; the gain in performance is very small, since the saved funcall is
+;; counterbalanced by the necessity of adding a bytecode for (point).
+;;
+;; Also, users are more likely to have modified the behavior of
+;; delete-char via advice or some similar mechanism. This is much
+;; less of a problem for the previous functions because it wouldn't
+;; make sense to modify the behaviour of `backward-char' without also
+;; modifying `forward-char', for example.
+
+;; (delete-char n) ==> (delete-region (point) (+ (point) n))
+;; (put 'delete-char 'byte-optimizer 'byte-optimize-delete-char)
+;; (defun byte-optimize-delete-char (form)
+;; (case (length (cdr form))
+;; (0 `(delete-region (point) (1+ (point))))
+;; (1 `(delete-region (point) (+ (point) ,(nth 1 form))))
+;; (t form)))
;; byte-compile-negation-optimizer lives in bytecomp.el
;(put '/= 'byte-optimizer 'byte-compile-negation-optimizer)
(put 'atom 'byte-optimizer 'byte-compile-negation-optimizer)
(put 'nlistp 'byte-optimizer 'byte-compile-negation-optimizer)
-
(defun byte-optimize-funcall (form)
;; (funcall '(lambda ...) ...) ==> ((lambda ...) ...)
;; (funcall 'foo ...) ==> (foo ...)
(defun byte-compile-splice-in-already-compiled-code (form)
;; form is (byte-code "..." [...] n)
- (if (not (memq byte-optimize '(t lap)))
+ (if (not (memq byte-optimize '(t byte)))
(byte-compile-normal-call form)
(byte-inline-lapcode
(byte-decompile-bytecode-1 (nth 1 form) (nth 2 form) t))
projects / chise / xemacs-chise.git.1 / blobdiff