Commit d8947b79 authored by Dan Nicolaescu's avatar Dan Nicolaescu
Browse files

* emacs-lisp/byte-opt.el (byte-compile-trueconstp): Handle more

constant forms.
(byte-compile-nilconstp): New function.
(byte-optimize-cond): Kill subsequent branches when a branch is
know to be taken or not taken.
(byte-optimize-if): Use byte-compile-nilconstp instead of hand
coding.
parent 30a308aa
2007-11-13 Stefan Monnier <monnier@iro.umontreal.ca>
* emacs-lisp/byte-opt.el (byte-compile-trueconstp): Handle more
constant forms.
(byte-compile-nilconstp): New function.
(byte-optimize-cond): Kill subsequent branches when a branch is
know to be taken or not taken.
(byte-optimize-if): Use byte-compile-nilconstp instead of hand
coding.
2007-11-13 Dan Nicolaescu <dann@ics.uci.edu>
* vc.el (vc-register): Allow registering a file passed as a
......
......@@ -185,6 +185,7 @@
;;; Code:
(require 'bytecomp)
(eval-when-compile (require 'cl))
(defun byte-compile-log-lap-1 (format &rest args)
(if (aref byte-code-vector 0)
......@@ -626,12 +627,24 @@
;; It is now safe to optimize code such that it introduces new bindings.
;; I'd like this to be a defsubst, but let's not be self-referential...
(defmacro byte-compile-trueconstp (form)
;; Returns non-nil if FORM is a non-nil constant.
`(cond ((consp ,form) (eq (car ,form) 'quote))
((not (symbolp ,form)))
((eq ,form t))
((keywordp ,form))))
(defsubst byte-compile-trueconstp (form)
"Return non-nil if FORM always evaluates to a non-nil value."
(cond ((consp form)
(case (car form)
(quote (cadr form))
(progn (byte-compile-trueconstp (car (last (cdr form)))))))
((not (symbolp form)))
((eq form t))
((keywordp form))))
(defsubst byte-compile-nilconstp (form)
"Return non-nil if FORM always evaluates to a nil value."
(cond ((consp form)
(case (car form)
(quote (null (cadr form)))
(progn (byte-compile-nilconstp (car (last (cdr form)))))))
((not (symbolp form)) nil)
((null form))))
;; If the function is being called with constant numeric args,
;; evaluate as much as possible at compile-time. This optimizer
......@@ -990,17 +1003,17 @@
(setq rest form)
(while (setq rest (cdr rest))
(cond ((byte-compile-trueconstp (car-safe (car rest)))
(cond ((eq rest (cdr form))
(setq form
(if (cdr (car rest))
(if (cdr (cdr (car rest)))
(cons 'progn (cdr (car rest)))
(nth 1 (car rest)))
(car (car rest)))))
;; This branch will always be taken: kill the subsequent ones.
(cond ((eq rest (cdr form)) ;First branch of `cond'.
(setq form `(progn ,@(car rest))))
((cdr rest)
(setq form (copy-sequence form))
(setcdr (memq (car rest) form) nil)))
(setq rest nil)))))
(setq rest nil))
((and (consp (car rest))
(byte-compile-nilconstp (caar rest)))
;; This branch will never be taken: kill its body.
(setcdr (car rest) nil)))))
;;
;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
(if (eq 'cond (car-safe form))
......@@ -1031,11 +1044,9 @@
(byte-optimize-if
`(if ,(car (last clause)) ,@(nthcdr 2 form)))))))
((byte-compile-trueconstp clause)
(nth 2 form))
((null clause)
(if (nthcdr 4 form)
(cons 'progn (nthcdr 3 form))
(nth 3 form)))
`(progn ,clause ,(nth 2 form)))
((byte-compile-nilconstp clause)
`(progn ,clause ,@(nthcdr 3 form)))
((nth 2 form)
(if (equal '(nil) (nthcdr 3 form))
(list 'if clause (nth 2 form))
......
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