gh-131798: Small improvements to remove_unneeded_uops

[tomasr8]

• Add _CHECK_PERIODIC to the list of skipped instructions. I believe this is safe to do since this instruction does not modify the stack. It is also relatively common so I think it's worth it to skip it.
• Add an extra guard to the optimizer.

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

[tomasr8]

When we are here, we know that op_without_pop[opcode] || op_without_pop_null[opcode] is true. But we should also make sure that op_without_pop[opcode] itself is true, otherwise it is possible to accidentally write 0 as the opcode.

[Fidget-Spinner]

• Add _CHECK_PERIODIC to the list of skipped instructions. I believe this is safe to do since this instruction does not modify the stack. It is also relatively common so I think it's worth it to skip it.

I read the code but just checking that I understand it right: op_skip means the instruction is still emitted, just that we "skip" it when trying to optimize away redundant push/pops right? If so that's ok the PR LGTM.

[tomasr8]

• Add _CHECK_PERIODIC to the list of skipped instructions. I believe this is safe to do since this instruction does not modify the stack. It is also relatively common so I think it's worth it to skip it.

I read the code but just checking that I understand it right: op_skip means the instruction is still emitted, just that we "skip" it when trying to optimize away redundant push/pops right? If so that's ok the PR LGTM.

Yes, that's exactly the case! This allows us to optimize for instance:

_LOAD_CONST
_CHECK_PERIODIC
_POP_TOP

into just

_NOP
_CHECK_PERIODIC
_NOP

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Fedora Stable Refleaks 3.x (tier-1) has failed when building commit 71dea74.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/320/builds/2497) and take a look at the build logs.
4. Check if the failure is related to this commit (71dea74) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/320/builds/2497

Failed tests:

• test.test_multiprocessing_fork.test_processes

Failed subtests:

• test_interrupt - test.test_multiprocessing_fork.test_processes.WithProcessesTestProcess.test_interrupt

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 320, in _bootstrap
    self.run()
    ~~~~~~~~^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 518, in _sleep_some_event
    time.sleep(100)
    ~~~~~~~~~~^^^^^
KeyboardInterrupt
k


Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 588, in test_interrupt
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 570, in _kill_process
    self.assertEqual(join(), None)
                     ~~~~^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 250, in __call__
    return self.func(*args, **kwds)
           ~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 156, in join
    res = self._popen.wait(timeout)
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/popen_fork.py", line 44, in wait
    return self.poll(os.WNOHANG if timeout == 0.0 else 0)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/popen_fork.py", line 28, in poll
    pid, sts = os.waitpid(self.pid, flag)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 566, in handler
    raise RuntimeError('join took too long: %s' % p)
RuntimeError: join took too long: <Process name='Process-3' pid=1325402 parent=1325398 started daemon>


Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 320, in _bootstrap
    self.run()
    ~~~~~~~~^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 517, in _sleep_some_event
    event.set()
    ~~~~~~~~~^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/synchronize.py", line 344, in set
    with self._cond:
         ^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/synchronize.py", line 242, in __exit__
    return self._lock.__exit__(*args)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/synchronize.py", line 100, in __exit__
    return self._semlock.__exit__(*args)
           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
KeyboardInterrupt
k


Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 588, in test_interrupt
    exitcode = self._kill_process(multiprocessing.Process.interrupt)
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 570, in _kill_process
    self.assertEqual(join(), None)
                     ~~~~^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 250, in __call__
    return self.func(*args, **kwds)
           ~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/process.py", line 156, in join
    res = self._popen.wait(timeout)
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/popen_fork.py", line 44, in wait
    return self.poll(os.WNOHANG if timeout == 0.0 else 0)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/multiprocessing/popen_fork.py", line 28, in poll
    pid, sts = os.waitpid(self.pid, flag)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-x86_64.refleak/build/Lib/test/_test_multiprocessing.py", line 566, in handler
    raise RuntimeError('join took too long: %s' % p)
RuntimeError: join took too long: <Process name='Process-1706' pid=1247987 parent=1230274 started daemon>