[dynamo] Compile time optimizations in tx.step() (#121790)
`python benchmarks/dynamo/microbenchmarks/dynamo_microbenchmarks.py`
- Before: `symbolic_convert_overhead_stress_test: 10.7s`
- After: `symbolic_convert_overhead_stress_test: 8.6s`
`tx.step()` is a small part of that benchmark, so likely the speedup in that isolated function is larger than the top line.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121790
Approved by: https://github.com/oulgen
