target-ppc: improve correctness of the fsel instruction

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6139 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
index 922060b..876b517 100644
--- a/target-ppc/op_helper.c
+++ b/target-ppc/op_helper.c
@@ -1561,7 +1561,7 @@
 
     farg1.ll = arg1;
 
-    if (!float64_is_neg(farg1.d) || float64_is_zero(farg1.d))
+    if ((!float64_is_neg(farg1.d) || float64_is_zero(farg1.d)) && !float64_is_nan(farg1.d))
         return arg2;
     else
         return arg3;