Note for possible future PR:

We could, at the cost of two bits intp_flags avoid the version number and combine the ALWAYS_TRUE and NONE specializations.
We need aALWAYS_TRUE_OR_FALSE and aIS_TRUE bit.
Classes that don't override__bool__ or__len__ andNone would set theALWAYS_TRUE_OR_FALSE bit. TheIS_TRUE bit would be set to 0 forNone, and to 1 for always true objects.

Rather than check the version number, check theALWAYS_TRUE_OR_FALSE, thenres = (tp_flags & IS_TRUE) ? Py_True : Py_False;

For abi4, we could add a per-object bit to handle immutable objects like ints and strings.

Merging is currently blocked on#106250.

Hey@brandtbucher, I have a question about this PR. In#106393 I had to change the code inPOP_JUMP_IF_TRUE/FALSE from

JUMPBY(oparg * Py_IsFalse(cond));

to

if (Py_IsFalse(cond)) {    JUMP_POP_DISPATCH(oparg, 1);  // Macro that wraps JUMPBY()}

The reason is that the uop executor currently exits whenever it jumps, and your original code from this PRalways jumps.

Did you (or@markshannon) have a reason to prefer theoparg * Py_IsFalse(cond) version over the conditional?

If there's no deep reason I'll keep it the way I coded it up; but if there is (maybe it came out faster in a micro-benchmark?) then I suppose I could fix it another way in the uop interpreter (e.g. only exiting if the jump offset is nonzero).

That the implementation of branches is itself branchless has a certain aesthetic appeal 🙂. TBH, that's the main reason.

The multiplication form will be quicker for unpredictable branches, and slower for predictable ones in the tier 1 interpreter.
I doubt it makes any difference in terms of overall performance, and will likely be irrelevant once the tier 2 interpreter does most of the work.