[PyTorch][JIT] Don't refcount Type singletons (#69579)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69579
This should help us avoid reference counting overhead on singleton Type subclasses without a major rewrite of the Type subsystem.
ghstack-source-id: 146643993
Test Plan:
Ran //caffe2/caffe2/fb/high_perf_models/pytorch/benchmark_framework_overheads:cpp_benchmark with arguments `--op empty -niter 40 --stressTestRecordFunction --captureRecordFunctionInputs` on devbig with turbo off.
Before:
```
I1206 13:47:15.037441 1201670 bench.cpp:144] Mean 0.737675
I1206 13:47:15.037463 1201670 bench.cpp:145] Median 0.736725
I1206 13:47:15.037468 1201670 bench.cpp:146] Min 0.722897
I1206 13:47:15.037473 1201670 bench.cpp:147] stddev 0.00508187
I1206 13:47:15.037482 1201670 bench.cpp:148] stddev / mean 0.00688903
```
After:
```
I1206 13:48:16.830123 1205612 bench.cpp:144] Mean 0.66988
I1206 13:48:16.830150 1205612 bench.cpp:145] Median 0.663956
I1206 13:48:16.830157 1205612 bench.cpp:146] Min 0.65986
I1206 13:48:16.830164 1205612 bench.cpp:147] stddev 0.0335928
I1206 13:48:16.830171 1205612 bench.cpp:148] stddev / mean 0.0501475
```
Static runtime startup is also improved; for CMF local_ro, time to initialize a predictor went from 10.01s to 9.59s.
(Note: I wish I had a production workload to demonstrate the advantage of this on. I tried ctr_mobile_feed local_ro net but it was neutral. Anything that manipulates types or List/Dict a lot might be promising.)
Reviewed By: suo
Differential Revision: D32923880
fbshipit-source-id: c82ed6689b3598e61047fbcb2149982173127ff0
