gh-131798: JIT: Narrow the return type of isinstance for some known arguments
#133172
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tomasr8
commented
Apr 29, 2025
| // isinstance(obj, cls) where both obj and cls have known types | ||
| // We can deduce either True or False | ||
| PyTypeObject *inst_type = sym_get_type(inst_sym); | ||
| if (sym_matches_type(inst_sym, cls) || PyType_IsSubtype(inst_type, cls)) { |
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This simulates PyObject_TypeCheck
| @@ -886,6 +886,44 @@ dummy_func(void) { | |||
| } | |||
| } | |||
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| op(_CALL_ISINSTANCE, (callable, self_or_null, args[oparg] -- res)) { | |||
| if (sym_is_null(self_or_null) || sym_is_not_null(self_or_null)) { | |||
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I've seen this guard used elsewhere with self_or_null but it's not clear to me whether it is needed here as well?
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In this PR:
isintance(obj, cls)toTrueif obj is a known type and cls is a known class and obj is a subclass of cls (and vice versa forFalse)isinstancetobool.Brandt also suggested adding an optimization for tuples which I'd like to add in a followup in order to keep the sizes of the individual PRs smaller. Though if you prefer to have it in one PR I can do it as well :)