ZJIT: Refine singleton class invariant to only invalidate on method shadowing#950
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…hadowing Previously, the NoSingletonClass invariant invalidated JIT code whenever a singleton class was created for an instance of a given class. This was overly conservative—many uses of singleton classes (freeze, introspection, non-shadowing methods) don't affect method dispatch for the original class. Refine the invariant to NoSingletonClassWithShadowingMethod: only invalidate when a method is defined on a singleton class that shadows a method on the original class. The hook moves from make_singleton_class() in class.c to rb_method_entry_make() in vm_method.c, where it checks whether the newly defined method exists on the superclass chain. Correctness is always maintained by GuardType, which checks the exact class of the receiver—singleton class objects fail this check and side-exit regardless of the patchpoint.
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Summary
NoSingletonClassinvariant toNoSingletonClassWithShadowingMethod: only invalidate when a method defined on a singleton class shadows a method on the original classmake_singleton_class()in class.c torb_method_entry_make()in vm_method.c, checkingrb_method_entry(super, mid)for shadowingTest plan