X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fx86%2Farith.lisp;h=25d7091516689865b545ec57491501053c7d4e92;hb=6ab9c60f1c53cc7cc912d644658bc23453a82ac4;hp=565a2e920e6fcdfd7f6b4e6617fe26bd6cfd6304;hpb=201e598b805d3b8f3a1206bc487cbb25180cef30;p=sbcl.git

diff --git a/src/compiler/x86/arith.lisp b/src/compiler/x86/arith.lisp
index 565a2e9..25d7091 100644
--- a/src/compiler/x86/arith.lisp
+++ b/src/compiler/x86/arith.lisp
@@ -176,9 +176,16 @@
 		  (:translate ,translate)
 		  (:generator ,untagged-penalty
 		  (move r x)
-		  (inst ,op r y))))))
-
-  ;;(define-binop + 4 add)
+		  ,(if (eq translate 'logand)
+		       ;; for the -C/UNSIGNED=>UNSIGNED VOP, this case
+		       ;; is optimized away as an identity somewhere
+		       ;; along the lines.  However, this VOP is used in
+		       ;; -C/SIGNED=>UNSIGNED, below, when the
+		       ;; higher-level lisp code can't optimize away the
+		       ;; non-trivial identity.
+		       `(unless (= y #.(1- (ash 1 n-word-bits)))
+			  (inst ,op r y))
+		       `(inst ,op r y)))))))
   (define-binop - 4 sub)
   (define-binop logand 2 and)
   (define-binop logior 2 or)
@@ -249,7 +256,6 @@
 	   (move r x)
 	   (inst add r y)))))
 
-
 ;;;; Special logand cases: (logand signed unsigned) => unsigned
 
 (define-vop (fast-logand/signed-unsigned=>unsigned