GH-100923: Embed jump mask in COMPARE_OP oparg

[markshannon]

Saves a few bytes in the code array.

• Issue: The "mask" stored in the cache of COMPARE_OP could be stored in the oparg. #100923

[sweeneyde]

Can the mask be added at compile time to avoid mutating the logical code?

def f():
    ...
c0 = f.__code__.replace()
# ... run the code here ...
c1 = f.__code__

assert c0 == c1              # fails?
assert hash(c0) == hash(c1)  # fails?

[sweeneyde]

Oh I see, the work is being done in PyCode_Quicken, which is already called on every code object, so we should be okay.

[markshannon]

Yes, the plan is to move PyCode_Quicken into the compiler. faster-cpython/ideas#530

[esc]

I just stumbled upon this. It seems like this PR didn't update the docs, as:

https://docs.python.org/3.12/library/dis.html#opcode-COMPARE_OP

Reads:

Perhaps the new masking mechanism could be included here? Or maybe it will suffice to update the docs to say cmp_op[opname>>4]? Would be happy to try to submit a PR if that is welcome.

[brandtbucher]

That issue is being covered in #107457.