Sorryyyyy for another refactor. This splits `_process_dynamic_shapes` into 3 parts:
1. `_combine_args` - mostly the same thing
2. `_check_dynamic_shapes`, which is responsible for raising 99% of UserErrors if the dynamic shapes spec is invalid (minus 1 UserError with DerivedDims)
3. `_process_dynamic_shapes`, which for now, is the same thing, minus the stuff in 2.
This refactor is helpful for incoming automatic dynamic shapes work, because, we're switching to `assume_static_by_default=False`, which is what `_dynamo.export` currently does. This means any unspecified dims are allocated a symbol, in contrast to export today which keeps unspecified dims static. Historically this has been desirable - export users don't want too much dynamism. So we want to change how the spec is translated into constraints.
This means when we switch over to automatic dynamic shapes, we want to plug in something in between steps 2. and 3. which patches up the spec for `assume_static_by_default=False`, filling in static shapes for any unspecified dims, and potentially clearing out the auto-dynamic dims (since they're no-ops). We would do this in-between 2. and 3. to keep `_process_dynamic_shapes` semantically the same, since it's used with `_dynamo.export`.
We could do this without a refactor, plugging in this transform before `_process_dynamic_shapes`, but since that function's responsible for both spec checking + constraint production, moving spec checking to before we transform the specs helps guarantee we're raising errors on what the user's specified, and not an internal export bug.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/133391
Approved by: https://github.com/avikchaudhuri
a75248528f