Emit math functions specific to output type (#18815)

Emit math functions specific to output type (#18815)

Summary:
Stacked on https://github.com/pytorch/pytorch/pull/18811

This makes it so that we only emit the *f variants of math functions if the output value's type is FloatTensor, otherwise we call the double variants to prevent loss of precision. This fixes more numerical issues
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18815

Differential Revision: D14816965

Pulled By: jamesr66a

fbshipit-source-id: 464be644168875ede987142281fb2168f4041e81