bpo-44338: Port LOAD_GLOBAL to PEP 659 adaptive interpreter #26638
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markshannon
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Python/ceval.c
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| STAT_INC(loadglobal_deferred); | ||
| cache->adaptive.counter--; | ||
| oparg = cache->adaptive.original_oparg; | ||
| JUMP_TO_INSTRUCTION(LOAD_GLOBAL); |
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This is also virtual identical, right? Will that be the case for all the XXXX_ADAPTIVE opcodes?
Python/specialize.c
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| goto fail; | ||
| } | ||
| cache1->module_keys_version = keys_version; | ||
| cache0->index = index; |
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Yeah, I was going to ask about this (Py_ssize_t -> uint16_t) but looks like GHA beat me to it. :) Does this limit us on the size of the builtins/globals dicts or are dicts already constrained to 2^16 entries?
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We just can't optimize access to variables with index > 64k.
If your module has more than 64k variables, then you have plenty of other problems 🙂
| SpecializedCacheEntry *caches = GET_CACHE(); | ||
| _PyAdaptiveEntry *cache0 = &caches[0].adaptive; | ||
| _PyLoadGlobalCache *cache1 = &caches[-1].load_global; | ||
| DEOPT_IF(dict->ma_keys->dk_version != cache1->module_keys_version, LOAD_GLOBAL); |
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Do we also need to check the case where it's a different globals dict? It can't be done from Python (except if someone creates a new function using the code object from another function, or passes the code object to exec()) but can easily be done from C. There is the remote chance that (in that already unlikely case) the keys version is the same.
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If the keys version is the same, then it has the same keys in the same order and is the same kind of dict.
In which case it doesn't matter if it is a different dictionary, because we cache the index, not the value.
As an aside, you can get different dictionaries with the same keys as module dicts at different times.
class C: pass
d1 = C().__dict__
d2 = C().__dict__
# d1 and d2 should share keys
m = ModuleType()
m.__dict__ = d1
# Specialize
m.__dict__ = d2
# globals in m would see same keys as when specialized
…-26638) * Add specializations of LOAD_GLOBAL. * Add more stats. * Remove old opcache; it is no longer used. * Add NEWS
Adds two specializations of
LOAD_GLOBAL:LOAD_GLOBAL_MODULEfor module variablesLOAD_GLOBAL_BUILTINfor builtins.Removes the old "opcache" mechanism.
Adds a few more stats (hidden behind a compile-time flag).
https://bugs.python.org/issue44338