Enable tail-call interpreter

In Python 3.14 (unreleased) there is a new build option which can improve performance in combination with PGO.

This would require potentially switching to Clang > 19 unless GCC 15 also supports this.

More information available in what's new in Python 3.14.

added scopeenhancement label

added priority3-normal severity4-low statusunconfirmed labels

assigned to @jelle, @freswa, @toolybird, and @gromit

changed the description

added statusconfirmed label and removed statusunconfirmed label

unassigned @freswa, @toolybird, and @gromit

Clarification from link above: "Note: This is not to be confused with tail call optimization of Python functions, which is currently not implemented in CPython."

changed title from Enable tail call optimisations to Enable tail-call interpreter

One concern here might be that clang/llvm is not in [core] breaking the repo hierarchy

"These figures turned out to be inaccurate." Oops.. It's still an improvement.. just not as much as first thought.

https://fidget-spinner.github.io/posts/apology-tail-call.html