pytorch

16d6af74 - [PyTorch] Optimize ~intrusive_ptr for the case of zero weak references (#47834)

[PyTorch] Optimize ~intrusive_ptr for the case of zero weak references (#47834) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47834 We can determine if (as is likely) there are no outstanding weak references without bothering to decrement the count. `std::shared_ptr` does this same optimization in libc++: https://github.com/llvm/llvm-project/blob/229db3647491ed2b2706a9b9ce13a97e38be6fa0/libcxx/src/memory.cpp#L69-L107 ghstack-source-id: 116576326 Test Plan: Saw time spent in TensorImpl::release_resources drop in local profiling of empty benchmark Run framework overhead benchmarks. 9-10% savings on OutOfPlace, small single digit savings on empty, essentially none on InPlace. Reviewed By: bhosmer Differential Revision: D24914763 fbshipit-source-id: 19b03f960e32123bc72f7edce63fa1d18c3c143f