[Pytorch backend delegation] Preprocess to accept (#58873)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58873
BackenDebugInforRecorder
Prior to this PR:
In order to generate debug handles corresponding to the graph being
lowered, backend's preprocess will call generate_debug_handles and will
get map of Node*-to-debug_handles.
In order to facilitate this, to_backend will own
BackendDebugInfoRecorder and initialize thread local pointer to it.
generate_debug_handle function will query thread local pointer to see if
there is a valid BackendDebugInforRecorder for the context. If there is
it will generate debug handles.
After this PR:
Signature of preprocess is changed such that backends have to register
preprocess that accepts instance of BackendDebugInfoRecorder by
reference. generate_debug_handles is no more a free function but becomes
part of the API of BackendDebugInfoRecorder. Now backend's preprocess
function will call generate_debug_handles on BackendDebugInfoRecorder
instead of free function.
Reason for this change:
With RAII that initializes thread local pointer, results in a lose
contract with backends, which may result in backends not storing
debug information. Making it part of API results in
backends having to be aware of BackendDebugInfoRecorder and explicitly
chosing not to generate/store debug information if they chose to do so.
Test Plan:
backend tests
Imported from OSS
Reviewed By: jbschlosser, raziel
Differential Revision: D28648613
fbshipit-source-id: c9b7e7bf0f78e87023ea7bc08612cf893b08cb98
