Currently, we specialize FOR_ITER for both tuple and list. We also handle tuple and lists specially in GET_ITER to support this specialization.

We should extend this specialization of iteration over sequences, using virtual iterators to bytes, str, bytesarray and others.
To do this, we should:

• Add a tp_getiteritem slots to PyTypeObject for sequences that can be efficiently indexed and cannot raise except for out-of-bounds access.
• Add a specialization of FOR_ITER for these classes.
• Specialize GET_ITER for:
  • iterators
  • indexable sequences (those classes with a tp_getiteritem slot)
• Specialize SEND for indexable sequences which should also improve JIT coverage, as unspecialized _SEND is currently a major cause of jit optimization failures.

Combined with #145667 this will allow effective specialization of a wider range of iterables and allow that specialization not only for for loops, but also for yield from loops.
It will add 3 instructions (4 new, 1 removed) which a reasonable

Linked PRs

• gh-145668: Optimize FOR_ITER virtual iterators for bytes, bytearray, … #145670