Fix handling of non-finite values in topk (#35253)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/34191
`at::native::radixSelect` basically uses integer comparison which creates a defined ordering of non-finite float values. This isn't compatible with IEEE float comparison, so mixing the two leads to unwritten values in the output.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35253
Differential Revision: D20645554
Pulled By: ezyang
fbshipit-source-id: 651bcb1742ed67086ec89cc318d862caae65b981
