Revert "restore x0, x1"
Revert "restore x0, x1"

This reverts commit 06c28c0a3273a41290cf13638bea0015160a9b97.

niboshi/chainer,ktnyt/chainer,jnishi/chainer,wkentaro/chainer,keisuke-umezawa/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,tkerola/chainer,jnishi/chainer,ktnyt/chainer,chainer/chainer,chainer/chainer,okuta/chainer,niboshi/chainer,pfnet/chainer,anaruse/chainer,keisuke-umezawa/chainer,chainer/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,wkentaro/chainer,hvy/chainer,wkentaro/chainer,ronekko/chainer,okuta/chainer,jnishi/chainer,ktnyt/chainer,ktnyt/chainer,keisuke-umezawa/chainer,jnishi/chainer,hvy/chainer,chainer/chainer,rezoo/chainer,keisuke-umezawa/chainer,hvy/chainer