From: "H. Peter Anvin" <hpa@zytor.com>
To: Jike Song <albcamus@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>,
tglx@linutronix.de, mingo@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: fix inline assembly constraints
Date: Thu, 30 Oct 2008 07:51:05 -0700 [thread overview]
Message-ID: <4909C9D9.7040105@zytor.com> (raw)
In-Reply-To: <df9815e70810292340g52d38e83t47dffd02125b4fe3@mail.gmail.com>
Jike Song wrote:
>
> Yes, sometimes gcc did have bugs with its obscure inline asm
> conventions. But I think the change of x86-64 atomic operations should
> be OK. Anyway, the "+" constraint is more clear than a "=m" output and
> a "m" input.
>
> The 32-bit atomic ops were already changed to "+m".(commit
> b862f3b099f3ea672c7438c0b282ce8201d39dfc)
>
You *THINK*. It's very easy to *THINK* that gcc won't do something
utterly moronic, and you'd be wrong.
Just changing it for the sake of churn is pointless... if there is a
bug, then we have to take the risk anyway, but if it is already correct,
then there is no point in provoking a bug. Not *your* bug, because your
code is correct, but gcc's bug.
FWIW, the reason that code doesn't use "+m" is because a version of gcc
which we no longer support didn't handle it. That by itself isn't a
reason to keep it, but there is also no reason to just "tidy" it, IMNSHO.
-hpa
next prev parent reply other threads:[~2008-10-30 14:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-29 16:32 [PATCH] x86: fix inline assembly constraints Jike Song
2008-10-29 16:32 ` Jike Song
2008-10-29 16:34 ` Ingo Molnar
2008-10-30 2:31 ` Jike Song
2008-10-30 3:54 ` H. Peter Anvin
2008-10-30 6:40 ` Jike Song
2008-10-30 14:51 ` H. Peter Anvin [this message]
2008-10-30 19:29 ` Ingo Molnar
2008-10-31 2:12 ` Jike Song
[not found] <fa.IZJ3RdF6xWbbMqWVWyYRstzZBsk@ifi.uio.no>
[not found] ` <fa.L4yER0Vo1brqQzpHIySgWqUN5UM@ifi.uio.no>
[not found] ` <fa.rs0w7okAn1If1ilwD81OTzT4rKg@ifi.uio.no>
2008-10-30 3:52 ` Robert Hancock
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