`LOAD_FAST_BORROW; POP_TOP` pairs should be removed

[brijkapadia]

Feature or enhancement

Proposal:

I noticed that

def f(x):
    x

produces these instructions:

  3           RESUME                   0

  4           LOAD_FAST_BORROW         0 (x)
              POP_TOP
              LOAD_COMMON_CONSTANT     7 (None)
              RETURN_VALUE

Full reproducer

from dis import dis

def f(x):
    x

dis(f)

The compiler should get rid of any LOAD_FAST_BORROW; POP_TOP pairs.

I will work on this.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-152600: Remove LOAD_FAST/LOAD_FAST_BORROW; POP_TOP pairs #152643

[picnixz]

cc @markshannon

[markshannon]

Not a common pattern, but we might as well fix it.
LOAD_FAST and LOAD_CONSTANT as well.

[brijkapadia]

I think that constants are already removed.
Also I think this will help #145749.