Re: GCC memory barriers are missing "cc" clobbers

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: GCC memory barriers are missing "cc" clobbers
Date: 2014-09-19 13:58:01
Message-ID: 23561.1411135081@sss.pgh.pa.us
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Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2014-09-19 12:00:16 +0200, Andres Freund wrote:
>> But addl sets condition flags. So this really also needs a "cc" clobber?
>> Or am I missing something?

> What I missed is that x86 has an implied "cc" clobber for every inline
> assembly statement. So forget that.

While it might not be buggy as it stands, I think we should add the "cc"
rather than rely on it being implicit. One reason is that people will
look at the x86 cases when developing code for other architectures, and
they could easily forget to add "cc" on machines where it does matter.

regards, tom lane

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