Date: Tuesday, January 11, 2011 @ 19:41:34 Author: rtoy Path: /project/cmucl/cvsroot/src/compiler
Modified: srctran.lisp
Transform (EQ foo NIL) to the equivalent (IF foo NIL T). Optimization suggested by Helmut Eller on cmucl-imp, 2011-01-08.
--------------+ srctran.lisp | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)
Index: src/compiler/srctran.lisp diff -u src/compiler/srctran.lisp:1.173 src/compiler/srctran.lisp:1.174 --- src/compiler/srctran.lisp:1.173 Tue Apr 20 13:57:46 2010 +++ src/compiler/srctran.lisp Tue Jan 11 19:41:34 2011 @@ -5,7 +5,7 @@ ;;; Carnegie Mellon University, and has been placed in the public domain. ;;; (ext:file-comment - "$Header: /project/cmucl/cvsroot/src/compiler/srctran.lisp,v 1.173 2010-04-20 17:57:46 rtoy Rel $") + "$Header: /project/cmucl/cvsroot/src/compiler/srctran.lisp,v 1.174 2011-01-12 00:41:34 rtoy Exp $") ;;; ;;; ********************************************************************** ;;; @@ -2945,6 +2945,29 @@ (%deftransform x '(function * *) #'commutative-arg-swap "place constant arg last."))
+;;; Convert (EQ foo NIL) and (EQ NIL foo) into the equivalent (if foo +;;; nil t), like we do for NULL and NOT so that IF optimizations will +;;; eliminate redundant negations. +(deftransform eq ((x y) (t t) * :when :both) + ;; It would be nice to use commutative-arg-swap above for this. + ;; Then we only need to handle one case. But if we do that + ;; commutative-arg-swap converts (eq 'declare x) to (eq x declare), + ;; losing the quote on declare. I'm too lazy to fix that in + ;; commutative-arg-swap, so we do everything here. + (cond ((and (constant-continuation-p x) + (not (constant-continuation-p y)) + (eq nil (continuation-value x))) + ;; (EQ NIL foo) case + `(if y nil t)) + ((and (constant-continuation-p y) + (not (constant-continuation-p x)) + (eq nil (continuation-value y))) + ;; (EQ foo NIL) case + `(if x nil t)) + (t + ;; Give up on all others. + (give-up)))) + ;;; Handle the case of a constant boole-code. ;;; (deftransform boole ((op x y) * * :when :both)