From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: GCC memory barriers are missing "cc" clobbers |
Date: | 2014-09-19 14:57:32 |
Message-ID: | 20140919145732.GJ4277@alap3.anarazel.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 2014-09-19 09:58:01 -0400, Tom Lane wrote:
> 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.
Fair point. It's also extremly poorly documented - my answer is from a
gcc dev, I haven't found an official document stating it. I don't really
see any need to backpatch though, do you?
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2014-09-19 14:58:56 | Re: GCC memory barriers are missing "cc" clobbers |
Previous Message | Andres Freund | 2014-09-19 14:54:15 | Re: pg_xlogdump --stats |