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Jeong, YunWon 8d7d9d931c Use dict keys-version stamps and entry-index hints in LOAD_ATTR/STORE_ATTR specializations (#8350)
* Use dict keys-version stamps and entry-index hints in attr specializations

Add a keys-version stamp to Dict: a globally unique u32 assigned lazily
and reset on any key-set change (new key, deletion, clear). Value-only
updates keep the stamp.

- LoadAttrMethodWithValues / LoadAttrNondescriptorWithValues: cache the
  instance dict's stamp in the pointer cache and skip the shadow probe
  while the stamp matches.
- LoadAttrWithHint: cache the entry index at specialization time; a hit
  is an identity check on the entry key instead of a hash probe, with
  self-refresh on miss.
- StoreAttrWithHint / StoreAttrInstanceValue: replace values through the
  cached entry index via set_item_with_hint.

Fixes youknowone#42

Assisted-by: Claude

* Share keys-version stamps between dicts with identical layouts

Derive the keys-version stamp from a shape — the ordered interned-key
sequence of a hole-free dict — instead of always allocating a unique
stamp. Dicts with identical layouts (instances of the same class built
by the same __init__) now carry equal stamps, so a LOAD_ATTR cache
entry populated by one instance skips the shadow probe for every
instance sharing the layout.

Shapes are held in a fixed-size lock-free table keyed by interned key
addresses; dicts with holes, non-interned keys, or more than 32 keys
fall back to dict-unique stamps.

Assisted-by: Claude

* Address clippy and review feedback for keys-version stamps

- Use BuildHasher::hash_one for shape hashing (clippy manual_hash_one)
- Fix set_item_with_hint doc: a refreshed hint is returned on any hint
  miss, not only when the hinted slot was vacant
- Route both holey-dict instances through a single LOAD_ATTR cache site
  in the snippet test

Assisted-by: Claude

* Restore try_read_cached_descriptor doc comment to its function

The doc block and #[inline] were left attached to store_attr_dict_hinted
when it was inserted above try_read_cached_descriptor.

Assisted-by: Claude

* Specialize LoadAttrWithHint even when the entry index exceeds u16

hint_for_key returns None both for an absent key and for a present key
whose entry index does not fit in u16, so very large instance dicts
stopped specializing entirely. Use get_item_opt_refresh_hint to decide
presence, degrading an unrepresentable hint to 0: the handler then
keeps taking its full-probe fallback path.

Assisted-by: Claude
2026-07-23 16:18:09 +09:00
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