[Emacs-diffs] emacs/lisp/emacs-lisp byte-opt.el

[Chong Yidong]

CVSROOT:        /sources/emacs
Module name:    emacs
Changes by:     Chong Yidong <cyd>      08/11/21 18:51:48

Modified files:
        lisp/emacs-lisp: byte-opt.el 

Log message:
        (byte-compile-butlast): Move up in file.
        (byte-optimize-plus): Don't call
        byte-optimize-delay-constants-math (bug#1334).  Use
        byte-optimize-predicate to optimize constants.
        (byte-optimize-minus): Don't call
        byte-optimize-delay-constants-math.  Remove zero arguments first
        if possible.  Call byte-optimize-predicate to optimize constants.
        (byte-optimize-multiply): Remove optimizations for arguments of 0
        and 2, which may be inaccurate.  Optimize (* x -1) to (- x).  Call
        byte-optimize-predicate.
        (byte-optimize-divide): Leave runtime errors unchanged.
        Optimize (/ x 1) to (+ x 0). Remove optimizations for arguments of
        0 and 2.0, which may be inaccurate.  Call byte-optimize-predicate.

CVSWeb URLs:
http://cvs.savannah.gnu.org/viewcvs/emacs/lisp/emacs-lisp/byte-opt.el?cvsroot=emacs&r1=1.113&r2=1.114

Patches:
Index: byte-opt.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/emacs-lisp/byte-opt.el,v
retrieving revision 1.113
retrieving revision 1.114
diff -u -b -r1.113 -r1.114
--- byte-opt.el 6 May 2008 03:21:10 -0000       1.113
+++ byte-opt.el 21 Nov 2008 18:51:48 -0000      1.114
@@ -747,119 +747,104 @@
                                (list (apply fun (nreverse constants)))))))))
     form))
 
+(defsubst byte-compile-butlast (form)
+  (nreverse (cdr (reverse form))))
+
 (defun byte-optimize-plus (form)
-  (setq form (byte-optimize-delay-constants-math form 1 '+))
+  ;; Don't call `byte-optimize-delay-constants-math' (bug#1334).
+  ;;(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))
-  (cond ((null (cdr form))
-        (condition-case ()
-            (eval form)
-          (error form)))
-;;;  It is not safe to delete the function entirely
-;;;  (actually, it would be safe if we know the sole arg
-;;;  is not a marker).
-;;;    ((null (cdr (cdr form))) (nth 1 form))
-       ((null (cddr form))
-        (if (numberp (nth 1 form))
-            (nth 1 form)
-          form))
-       ((and (null (nthcdr 3 form))
+  ;; For (+ constants...), byte-optimize-predicate does the work.
+  (when (memq nil (mapcar 'numberp (cdr form)))
+    (cond
+     ;; (+ x 1) --> (1+ x) and (+ x -1) --> (1- x).
+     ((and (= (length form) 3)
              (or (memq (nth 1 form) '(1 -1))
                  (memq (nth 2 form) '(1 -1))))
-        ;; Optimize (+ x 1) into (1+ x) and (+ x -1) into (1- x).
-        (let ((integer
+      (let (integer other)
                (if (memq (nth 1 form) '(1 -1))
-                   (nth 1 form)
-                 (nth 2 form)))
-              (other
-               (if (memq (nth 1 form) '(1 -1))
-                   (nth 2 form)
-                 (nth 1 form))))
-          (list (if (eq integer 1) '1+ '1-)
-                other)))
-       (t form)))
+           (setq integer (nth 1 form) other (nth 2 form))
+         (setq integer (nth 2 form) other (nth 1 form)))
+       (setq form
+             (list (if (eq integer 1) '1+ '1-) other))))
+     ;; Here, we could also do
+     ;;  (+ x y ... 1) --> (1+ (+ x y ...))
+     ;;  (+ x y ... -1) --> (1- (+ x y ...))
+     ;; The resulting bytecode is smaller, but is it faster? -- cyd
+     ))
+  (byte-optimize-predicate form))
 
 (defun byte-optimize-minus (form)
-  ;; Put constants at the end, except the last constant.
-  (setq form (byte-optimize-delay-constants-math form 2 '+))
-  ;; Now only first and last element can be a number.
-  (let ((last (car (reverse (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))))
+  ;; Don't call `byte-optimize-delay-constants-math' (bug#1334).
+  ;;(setq form (byte-optimize-delay-constants-math form 2 '+))
+  ;; Remove zeros.
+  (when (and (nthcdr 3 form)
+            (memq 0 (cddr form)))
+    (setq form (nconc (list (car form) (cadr form))
+                     (delq 0 (copy-sequence (cddr form)))))
+    ;; After the above, we must turn (- x) back into (- x 0)
+    (or (cddr form)
+       (setq form (nconc form (list 0)))))
+  ;; For (- constants..), byte-optimize-predicate does the work.
+  (when (memq nil (mapcar 'numberp (cdr form)))
+    (cond
+     ;; (- x 1) --> (1- x)
          ((equal (nthcdr 2 form) '(1))
           (setq form (list '1- (nth 1 form))))
+     ;; (- x -1) --> (1+ x)
          ((equal (nthcdr 2 form) '(-1))
           (setq form (list '1+ (nth 1 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))))))))
-;;;  It is not safe to delete the function entirely
-;;;  (actually, it would be safe if we know the sole arg
-;;;  is not a marker).
-;;;  (if (eq (nth 2 form) 0)
-;;;      (nth 1 form)                  ; (- x 0)  -->  x
-    (byte-optimize-predicate
-     (if (and (null (cdr (cdr (cdr form))))
-             (eq (nth 1 form) 0))      ; (- 0 x)  -->  (- x)
-        (cons (car form) (cdr (cdr form)))
-       form))
-;;;    )
-  )
+     ;; (- 0 x) --> (- x)
+     ((and (eq (nth 1 form) 0)
+          (= (length form) 3))
+      (setq form (list '- (nth 2 form))))
+     ;; Here, we could also do
+     ;;  (- x y ... 1) --> (1- (- x y ...))
+     ;;  (- x y ... -1) --> (1+ (- x y ...))
+     ;; The resulting bytecode is smaller, but is it faster? -- cyd
+     ))
+  (byte-optimize-predicate form))
 
 (defun byte-optimize-multiply (form)
   (setq form (byte-optimize-delay-constants-math form 1 '*))
-  ;; If there is a constant 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 (car (reverse form))))
-          (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))))))
-
-(defsubst byte-compile-butlast (form)
-  (nreverse (cdr (reverse form))))
+  ;; For (* constants..), byte-optimize-predicate does the work.
+  (when (memq nil (mapcar 'numberp (cdr form)))
+    ;; After `byte-optimize-predicate', if there is a INTEGER constant
+    ;; in FORM, it is in the last element.
+    (let ((last (car (reverse (cdr form)))))
+      (cond
+       ;; Would handling (* ... 0) here cause floating point errors?
+       ;; See bug#1334.
+       ((eq 1 last) (setq form (byte-compile-butlast form)))
+       ((eq -1 last)
+       (setq form (list '- (if (nthcdr 3 form)
+                               (byte-compile-butlast form)
+                             (nth 1 form))))))))
+  (byte-optimize-predicate form))
 
 (defun byte-optimize-divide (form)
   (setq form (byte-optimize-delay-constants-math form 2 '*))
+  ;; After `byte-optimize-predicate', if there is a INTEGER constant
+  ;; in FORM, it is in the last element.
   (let ((last (car (reverse (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 (byte-compile-butlast form)))
-             ((numberp (nth 1 form))
-              (setq form (cons (car form)
-                               (cons (/ (nth 1 form) last)
-                                     (byte-compile-butlast (cdr (cdr form)))))
-                    last nil))))
     (cond
-;;;      ((null (cdr (cdr form)))
-;;;       (nth 1 form))
-         ((eq (nth 1 form) 0)
-          (append '(progn) (cdr (cdr form)) '(0)))
+     ;; Runtime error (leave it intact).
+     ((or (null last)
+         (eq last 0)
+         (memql 0.0 (cddr form))))
+     ;; No constants in expression
+     ((not (numberp last)))
+     ;; For (* constants..), byte-optimize-predicate does the work.
+     ((null (memq nil (mapcar 'numberp (cdr form)))))
+     ;; (/ x y.. 1) --> (/ x y..)
+     ((and (eq last 1) (nthcdr 3 form))
+      (setq form (byte-compile-butlast form)))
+     ;; (/ x -1), (/ x .. -1)  --> (- x), (- (/ x ..))
          ((eq last -1)
-          (list '- (if (nthcdr 3 form)
+      (setq form (list '- (if (nthcdr 3 form)
                        (byte-compile-butlast form)
-                     (nth 1 form))))
-         (form))))
+                           (nth 1 form)))))))
+  (byte-optimize-predicate form))
 
 (defun byte-optimize-logmumble (form)
   (setq form (byte-optimize-delay-constants-math form 1 (car form)))