Revert "avoid selecting half-packets when unnecessary"

This reverts commit 5ca10480b0756e40b0723d90adeba8506291fc7c

Eigen/src/Core/util/XprHelper.h

diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 26aa609..fd2db56 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -195,7 +195,7 @@
 };
 
 template<int Size, typename PacketType,
-         bool Stop = Size==Dynamic || Size >= unpacket_traits<PacketType>::size || is_same<PacketType,typename unpacket_traits<PacketType>::half>::value>
+         bool Stop = Size==Dynamic || (Size%unpacket_traits<PacketType>::size)==0 || is_same<PacketType,typename unpacket_traits<PacketType>::half>::value>
 struct find_best_packet_helper;
 
 template< int Size, typename PacketType>