Flag guard unbacked SymInt/SymFloat support (#94987)
I believe this fixes the AllenaiLongformerBase problem in periodic.
The longer version of the problem is here is we are currently optimistically converting all item() calls into unbacked SymInt/SymFloat, but sometimes this results in a downstream error due to a data-dependent guard. Fallbacks for this case are non-existent; this will just crash the model. This is bad. So we flag guard until we get working fallbacks.
What could these fallbacks look like? One idea I have is to optimistically make data-dependent calls unbacked, but then if it results in a crash, restart Dynamo analysis with the plan of graph breaking when the item() call immediately happened.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94987
Approved by: https://github.com/Skylion007, https://github.com/malfet
