Added support for Dim operation in ONNX export (#31928)
Summary:
While ONNX does not currently directly support the Dim operation on a
tensor, we can provide the same functionality with two ONNX operations.
This allows us to support Dim for all opsets. It may be adventageous to
add support for Dim into a future ONNX opset, and use that for more
efficient code.
While testing dim op found that there is an issue with empty blocks
withing if statements. Modified graph generation to prevent generation
of empty if blocks.
Fixes https://github.com/pytorch/pytorch/issues/27569
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31928
Reviewed By: hl475
Differential Revision: D19376602
Pulled By: houseroad
fbshipit-source-id: 111682b058a5341f5cca6c1a950c83ae412a4c6c
