LOAD_ATTR_WITH_HINT and STORE_ATTR_WITH_HINT have internal branching.

[markshannon]

https://github.com/python/cpython/blob/main/InternalDocs/adaptive.md describes how specialized instructions should be a series of guards followed by simple, linear code.
Both instructions have two different paths with guards on each path. We should eliminate one of the branches.
Since the instance dictionary is almost certain to have only str keys, we should choose that path.

Linked PRs

• GH-122616: Simplify LOAD_ATTR_WITH_HINT and STORE_ATTR_WITH_HINT #122620

[hugovk]

Triage: closing because the linked PR is merged, please re-open if still needed.

[scoder]

As already mentioned in the PR, this change introduced behavioural differences, making existing Python code fail with an exception. See cython/cython#6426 (comment)