gh-131798: JIT: Narrow the return type of _CALL_LEN to int

[diegorusso]

Reduce unnecessary guards whenever len() is called and used in arithmetic operations.

• Issue: Better uop coverage in the JIT optimizer #131798

[Fidget-Spinner]

Thanks!

[Fidget-Spinner]

Windows JIT builds might've been broken by #132852. That PR did not trigger JIT CI.

[tomasr8]

I don't know if it's needed in this case, but for other tests there's normally a 'control' variable that checks that the result is still correct even with the optimization. Something like this:

Suggested change

	a = [1, 2, 3, 4]
	for _ in range(n):
	_ = len(a) - 1
	_, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
	x = 0
	a = [1, 2, 3, 4]
	for _ in range(n):
	_ = len(a) - 1
	if _ == 3:
	x += 1
	_, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
	self.assertEqual(res, TIER2_THRESHOLD)

[diegorusso]

Good point, I'll do it.

[diegorusso]

OK the problem is if I add this, _GUARD_TOS_INT and _GUARD_NOS_INT are appearing in the uops list.

[Fidget-Spinner]

Yeah we can't do it. x is from outside the loop (trace), so the first x += 1 has to have a guard somewhere.