From: "Mattias Engdegård" <mattiase@acm.org>
To: Robert Pluim <rpluim@gmail.com>
Cc: emacs-devel@gnu.org, Po Lu <luangruo@yahoo.com>
Subject: Re: HAVE_FAST_UNALIGNED_ACCESS
Date: Thu, 30 Mar 2023 12:28:30 +0200 [thread overview]
Message-ID: <87A3D742-5B8B-4F6B-805B-67AB8B4ECFF5@acm.org> (raw)
In-Reply-To: <87sfdmlgzx.fsf@gmail.com>
30 mars 2023 kl. 11.34 skrev Robert Pluim <rpluim@gmail.com>:
> but even if unaligned access is normally permitted by a machine, it is
> still undefined behavior to dereference an unaligned pointer.
That's not necessarily a problem; we have plenty of formally undefined behaviour. What's important is whether we can be confident that it works.
> Instead, HAVE_FAST_UNALIGNED_ACCESS and UNALIGNED_LOAD_SIZE should be
> removed and memcpy used instead:
No, this isn't something we should be doing at all unless the platform allows fast unaligned access.
Ideally we shouldn't do any of this nonsense but I haven't worked out how to get the autovectorisers to kick in.
> Emacs currently
> crashes when built with various compilers performing pointer alignment
> checks.
Which compilers, exactly?
next prev parent reply other threads:[~2023-03-30 10:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 9:34 HAVE_FAST_UNALIGNED_ACCESS Robert Pluim
2023-03-30 10:26 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-03-30 11:09 ` HAVE_FAST_UNALIGNED_ACCESS Sam James
2023-03-30 12:18 ` HAVE_FAST_UNALIGNED_ACCESS Arsen Arsenović
[not found] ` <87v8ihu3t8.fsf@yahoo.com>
2023-03-31 7:15 ` HAVE_FAST_UNALIGNED_ACCESS Robert Pluim
2023-03-31 7:45 ` HAVE_FAST_UNALIGNED_ACCESS Arsen Arsenović
2023-03-31 17:29 ` HAVE_FAST_UNALIGNED_ACCESS Mattias Engdegård
2023-03-31 20:13 ` HAVE_FAST_UNALIGNED_ACCESS Arsen Arsenović
2023-03-30 10:28 ` Mattias Engdegård [this message]
2023-03-30 11:38 ` HAVE_FAST_UNALIGNED_ACCESS Vibhav Pant
2023-03-31 16:57 ` HAVE_FAST_UNALIGNED_ACCESS Mattias Engdegård
2023-03-31 17:59 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-03-31 18:03 ` HAVE_FAST_UNALIGNED_ACCESS Mattias Engdegård
2023-03-31 18:12 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 0:45 ` HAVE_FAST_UNALIGNED_ACCESS Po Lu
2023-04-01 5:43 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 6:31 ` HAVE_FAST_UNALIGNED_ACCESS Po Lu
2023-04-01 6:39 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 7:42 ` HAVE_FAST_UNALIGNED_ACCESS Mattias Engdegård
2023-04-01 8:19 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 9:17 ` HAVE_FAST_UNALIGNED_ACCESS Po Lu
2023-04-01 11:25 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 12:59 ` HAVE_FAST_UNALIGNED_ACCESS Arsen Arsenović
2023-04-01 13:33 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-01 15:22 ` HAVE_FAST_UNALIGNED_ACCESS Arsen Arsenović
2023-04-01 16:22 ` HAVE_FAST_UNALIGNED_ACCESS Eli Zaretskii
2023-04-02 0:50 ` HAVE_FAST_UNALIGNED_ACCESS Po Lu
2023-04-02 0:48 ` HAVE_FAST_UNALIGNED_ACCESS Po Lu
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