more careful use of auto in sparse operations (#17958)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17958
In some places, we need 64-bit for corner cases even though it's going to be rare.
In some places, we were using 64-bit unnecessarily.
Reviewed By: hyuen
Differential Revision: D14435523
fbshipit-source-id: e01ab73029ff780133af7ff4bbbe2e17926ed5a2
