pytorch

a4d86e0d - [quant][fx][perf] improve runtime of prepare step for large models (#61132)

[quant][fx][perf] improve runtime of prepare step for large models (#61132) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/61132 For large models, the insert_observers_for_model function was taking a long time, especially for the case where not all the nodes are being quantized For example for a model with 21000 nodes of which only ~50 are being quantized the breakdown of prepare_fx vs convert fx was prepare_fx 979 seconds convert_fx 9 seconds The main reason was because we were doing some unnecessary computation for all nodes in this function, this PR just moves them to where they are actually used After this PR prepare_fx 26 seconds convert_fx 9 seconds Test Plan: Existing tests Imported from OSS Reviewed By: raghuramank100 Differential Revision: D29522303 fbshipit-source-id: 7ce12582a859d02ff763abebf4a592d28e0764ca