pytorch

65bfa138 - [PyTorch Mobile] Do not create a static variable in Dispatcher::singleton() (#52447)

[PyTorch Mobile] Do not create a static variable in Dispatcher::singleton() (#52447) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/52447 Currently, `Dispatcher::singleton()` is always inlined. Additionally, `Dispatcher::singleton()` contains a static variable, which means that the generated code calls `__cxa_guard_acquire` and `__cxa_guard_release` which help implement exactly once semantics for the initialization of the `static Dispatcher& s` variable. For `C10_MOBILE`, we should not create the additional static ref within the inlined function to save binary size since it results in a lot of additional code being generated by the compiler. The `Dispatcher::singleton()` method is called from the generated method stubs for all aten opertors that are code-generated and potentially also from other operators that hand off execution to the kernel function for the right backend via the PyTorch Dispatcher. This is a classic space/time (efficiency) tradeoff, so feedback would be welcome. kimishpatel, I'll need your expertise in figuring out how to perf-test this change, specifically for mobile. Here's the godbolt link in case you wish to check out the generated code for a `static` variable within a function: https://godbolt.org/z/cdsG3v {F375631117} ghstack-source-id: 121989311 Test Plan: Build + BSB ### lightspeed-messenger *Divide the number below by 2* ``` D26507049-V1 (https://www.internalfb.com/intern/diff/D26507049/?dest_number=121944956) messenger-experimental-optimized-device: Succeeded Change in Download Size for arm64 + 3x assets variation: -21.7 KiB Change in Uncompressed Size for arm64 + 3x assets variation: -65.4 KiB Mbex Comparison: https://our.intern.facebook.com/intern/mbex/bsb:243392763936025@base/bsb:243392763936025@diff/ ``` ### igios ``` D26507049-V1 (https://www.internalfb.com/intern/diff/D26507049/?dest_number=121944956) igios: Succeeded Change in Download Size for arm64 + 3x assets variation: -15.6 KiB Change in Uncompressed Size for arm64 + 3x assets variation: -34.3 KiB Mbex Comparison: https://our.intern.facebook.com/intern/mbex/bsb:882756935844095@base/bsb:882756935844095@diff/ ``` ### fbios-pika ``` D26507049-V1 (https://www.internalfb.com/intern/diff/D26507049/?dest_number=121944956) fbios-pika: Succeeded Change in Download Size for arm64 + 3x assets variation: -8.6 KiB Change in Uncompressed Size for arm64 + 3x assets variation: -29.1 KiB Mbex Comparison: https://our.intern.facebook.com/intern/mbex/bsb:832297083999539@base/bsb:832297083999539@diff/ ``` Reviewed By: swolchok Differential Revision: D26507049 fbshipit-source-id: 0d2f55ea2d42a0782fb69aabfa517f2ec60c8036