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From: Alexander Monakov <amonakov@ispras.ru>
To: Paul Koning <paulkoning@comcast.net>
Cc: "Markus Fröschle" <markus@mubf.de>, gcc@gcc.gnu.org
Subject: Re: asking for __attribute__((aligned()) clarification
Date: Wed, 21 Aug 2019 14:58:00 -0000	[thread overview]
Message-ID: <alpine.LNX.2.20.13.1908211748560.32047@monopod.intra.ispras.ru> (raw)
In-Reply-To: <0A5DAB14-F153-486B-BA04-6AD500C85E71@comcast.net>

On Wed, 21 Aug 2019, Paul Koning wrote:

> I agree, but if the new approach generates a warning for code that was written
> to the old rules, that would be unfortunate.

FWIW I don't know which GCC versions accepted 'packed' on a scalar type.
Already in 2006 GCC 3.4 would issue a warning:

$ echo 'typedef int ui __attribute__((packed));' | gcc34 -xc - -S -o-
        .file   ""
<stdin>:1: warning: `packed' attribute ignored
        .section        .note.GNU-stack,"",@progbits
        .ident  "GCC: (GNU) 3.4.6 20060404 (Red Hat 3.4.6-4)"

> Yes.  But last I tried, optimizing that for > 1 alignment is problematic
> because that information often doesn't make it down to the target code even
> though it is documented to do so.

Thanks, indeed this memcpy solution is not so well suited for that.

Alexander

  reply	other threads:[~2019-08-21 14:58 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-19 12:46 "Markus Fröschle"
2019-08-19 13:57 ` Paul Koning
2019-08-19 14:01   ` Richard Earnshaw (lists)
2019-08-19 14:08     ` Alexander Monakov
2019-08-19 14:12       ` Paul Koning
2019-08-20  5:46       ` Aw: " "Markus Fröschle"
2019-08-21 14:29         ` Alexander Monakov
2019-08-21 14:32           ` Paul Koning
2019-08-21 14:58             ` Alexander Monakov [this message]
2019-08-21 16:50               ` Paul Koning
2019-08-21 17:35                 ` Jonathan Wakely

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