neonene <nicesal...@gmail.com> added the comment:
>What exactly does "pgo hard reject" mean? In my recognition, "pgo hard reject" is based on the PGOptimizer's heuristic, "reject" is related to the probe count (hot/cold). https://developercommunity.visualstudio.com/t/1531987#T-N1535774 And there was a reply from MSVC team, closing the issue. MSVC won't be fixed in the near future. https://developercommunity.visualstudio.com/t/1595341#T-N1695626 >From the reply and my investigation, 3.11 would need the following: 1. Some callsites such as tp_* pointer should not inline its fastpaths in the eval switch-case. They often conflict. Each pointer needs to be wrapped with a function or maybe _PyEval_EvalFrameDefault needs to be enclosed with "inline_depth(0)" pragma. 2. __assume(0) should be replaced with other function, inside the eval switch-case or in the inlined paths of callees. This is critical with PGO. 3. For inlining, use __forceinline / macro / const function pointer. MSVC's stuck can be avoided in many ways, when force-inlining in the evalloop a ton of Py_DECREF()s, unless tp_dealloc does not create a inlined callsite: void _Py_Dealloc(PyObject *op) { ... #pragma inline_depth(0) // effects from here, PGO accepts only 0. (*dealloc)(op); // conflicts when inlined. } #pragma inline_depth() // can be reset only outside the func. * Virtual Call Speculation: https://docs.microsoft.com/en-us/cpp/build/profile-guided-optimizations?view=msvc-170#optimizations-performed-by-pgo * The profiler runs under /GENPROFILE:PATH option, but at the big ceval-func, the optimizer merges the profiles into one like /GENPROFILE:NOPATH mode. https://docs.microsoft.com/en-us/cpp/build/reference/genprofile-fastgenprofile-generate-profiling-instrumented-build?view=msvc-170#arguments * __assume(0) (Py_UNREACHABLE): https://devblogs.microsoft.com/cppblog/visual-studio-2017-throughput-improvements-and-advice/#remove-usages-of-__assume ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue45116> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
