gh-115999: Specialize STORE_ATTR in free-threaded builds.
#127838
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nascheme
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STORE_ATTR free-threaded builds.STORE_ATTR in free-threaded builds.
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Thanks for taking this on! This looks like a regression on the default build. I haven't had a chance to dig into it, but I suspect it might either be due to the check that Sam flagged in _STORE_ATTR_INSTANCE_VALUE or the change to when we read the type version in _Py_Specialize_StoreAttr. It looks like the richards benchmark is the most heavily affected, so that might be a good isolated benchmark to use for debugging.
Based on my benchmarking my second commit, the regression with Regarding the |
This was actually not hard to fix. I was thinking that |
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* Fix locking for `STORE_ATTR_INSTANCE_VALUE`. Create `_GUARD_TYPE_VERSION_AND_LOCK` so that object stays locked and `tp_version_tag` cannot change. Fix inverted logic bug that caused erroneous deopt. * Fix locking for `_STORE_ATTR_WITH_HINT`. Double check that `_PyObject_GetManagedDict()` hasn't disappeared since we locked the dict. - Pass `tp_version_tag` to `specialize_dict_access()`, ensuring the version we store on the cache is the correct one (in case of it changing during the specalize analysis). - Split `analyze_descriptor` into `analyze_descriptor_load` and `analyze_descriptor_store` since those don't share much logic. Add `descriptor_is_class` helper function. - In `specialize_dict_access`, double check `_PyObject_GetManagedDict()` in case we race and dict was materialized before the lock.
If the type is new and a version tag hasn't yet been assigned, we would fail to specialize it. Use `_PyType_LookupRefAndVersion()` instead of `type_get_version()`, which will assign a version.
Use provided value of `tp_version` to store in cache.
This also fixes the case if the dict is replaced with a different one.
The function is only used in with-GIL builds.
For `specialize_dict_access_inline()`, we need to lock the keys object. * Add `_PyDictKeys_StringLookupSplit` which does required locking and use in place of `_PyDictKeys_StringLookup`. * Change `_PyObject_TryGetInstanceAttribute` to use that function in the case of split keys. * Add `unicodekeys_lookup_split` helper which allows code sharing between `_Py_dict_lookup` and `_PyDictKeys_StringLookupSplit`.
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…thongh-127838) * Add `_PyDictKeys_StringLookupSplit` which does locking on dict keys and use in place of `_PyDictKeys_StringLookup`. * Change `_PyObject_TryGetInstanceAttribute` to use that function in the case of split keys. * Add `unicodekeys_lookup_split` helper which allows code sharing between `_Py_dict_lookup` and `_PyDictKeys_StringLookupSplit`. * Fix locking for `STORE_ATTR_INSTANCE_VALUE`. Create `_GUARD_TYPE_VERSION_AND_LOCK` uop so that object stays locked and `tp_version_tag` cannot change. * Pass `tp_version_tag` to `specialize_dict_access()`, ensuring the version we store on the cache is the correct one (in case of it changing during the specalize analysis). * Split `analyze_descriptor` into `analyze_descriptor_load` and `analyze_descriptor_store` since those don't share much logic. Add `descriptor_is_class` helper function. * In `specialize_dict_access`, double check `_PyObject_GetManagedDict()` in case we race and dict was materialized before the lock. * Avoid borrowed references in `_Py_Specialize_StoreAttr()`. * Use `specialize()` and `unspecialize()` helpers. * Add unit tests to ensure specializing happens as expected in FT builds. * Add unit tests to attempt to trigger data races (useful for running under TSAN). * Add `has_split_table` function to `_testinternalcapi`.
STORE_ATTR_INSTANCE_VALUE,STORE_ATTR_SLOT,STORE_ATTR_WITH_HINT). Need a combination of locks and atomics to be safe._Py_Specialize_StoreAttr. Avoid using borrowed references. Save and store thetp_version_tagfrom the beginning of the specialization process since it might change. Use helper functions to update opcode.--disable-gilbuilds #115999