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Hi @encukou , could you please review this PR?

Oh, wait, I missed that this only fails on 3.13.
We generally don't backport fixes to maintenance branches, the same would apply to a 3.13-only fix. But we can make an exception; and I guess we should, for this hard-to-diagnose issue.

@ayappanec, as the AIX expert, does this look good?

I guess this issue happens with OpenXL compiler (IBM's clang compiler) which by default passes "-maltivec" that enforces strict alignment rules.
@encukou The changes looks good.

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.13 (tier-1) has failed when building commit 793a86f.

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/1441/builds/1856) and take a look at the build logs.
4. Check if the failure is related to this commit (793a86f) 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/1441/builds/1856

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

==

Traceback (most recent call last):
  File "/root/buildarea/3.13.angelico-debian-amd64/build/Lib/test/support/__init__.py", line 856, in gc_collect
    gc.collect()
ResourceWarning: unclosed file <_io.FileIO name=13 mode='wb' closefd=True>


Traceback (most recent call last):
  File "/root/buildarea/3.13.angelico-debian-amd64/build/Lib/test/support/__init__.py", line 856, in gc_collect
    gc.collect()
ResourceWarning: unclosed file <_io.FileIO name=11 mode='wb' closefd=True>