[NNC] Fix an issue with half-scalar vars coerced to float (Take 2) (#47448)
Summary:
Take 2 of this fix, I removed the repro from the issue which is a bit flaky due to parallelism. It broke on Windows but isn't specific to Windows or this fix, I think. I'll make sure all the tests pass this time (cc zou3519).
Fixes an issue where fp16 scalars created by the registerizer could be referenced as floats - causing invalid conversions which would crash in the NVRTX compile. I also noticed that we were inserting patterns like float(half(float(X))) and added a pass to collapse those down inside the CudaHalfScalarRewriter.
Fixes https://github.com/pytorch/pytorch/issues/47138
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47448
Reviewed By: glaringlee
Differential Revision: D24765070
Pulled By: nickgg
fbshipit-source-id: 5297e647534d53657bef81f4798e8aa6a93d1fbd
