From: Nathan Chancellor <natechancellor@gmail.com>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powerpc: slightly improve cache helpers
Date: Mon, 8 Jul 2019 23:49:52 -0700 [thread overview]
Message-ID: <20190709064952.GA40851@archlinux-threadripper> (raw)
In-Reply-To: <a5864549-40c3-badd-8c41-d5b7bf3c4f3c@c-s.fr>
On Tue, Jul 09, 2019 at 07:04:43AM +0200, Christophe Leroy wrote:
>
>
> Le 08/07/2019 à 21:14, Nathan Chancellor a écrit :
> > On Mon, Jul 08, 2019 at 11:19:30AM +1000, Michael Ellerman wrote:
> > > On Fri, 2019-05-10 at 09:24:48 UTC, Christophe Leroy wrote:
> > > > Cache instructions (dcbz, dcbi, dcbf and dcbst) take two registers
> > > > that are summed to obtain the target address. Using 'Z' constraint
> > > > and '%y0' argument gives GCC the opportunity to use both registers
> > > > instead of only one with the second being forced to 0.
> > > >
> > > > Suggested-by: Segher Boessenkool <segher@kernel.crashing.org>
> > > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> > >
> > > Applied to powerpc next, thanks.
> > >
> > > https://git.kernel.org/powerpc/c/6c5875843b87c3adea2beade9d1b8b3d4523900a
> > >
> > > cheers
> >
> > This patch causes a regression with clang:
>
> Is that a Clang bug ?
No idea, it happens with clang-8 and clang-9 though (pretty sure there
were fixes for PowerPC in clang-8 so something before it probably won't
work but I haven't tried).
>
> Do you have a disassembly of the code both with and without this patch in
> order to compare ?
I can give you whatever disassembly you want (or I can upload the raw
files if that is easier).
Cheers,
Nathan
>
> Segher, any idea ?
>
> Christophe
>
> >
> > https://travis-ci.com/ClangBuiltLinux/continuous-integration/jobs/213944668
> >
> > I've attached my local bisect/build log.
> >
> > Cheers,
> > Nathan
> >
next prev parent reply other threads:[~2019-07-09 6:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-10 9:24 [PATCH v2] powerpc: slightly improve cache helpers Christophe Leroy
2019-07-08 1:19 ` Michael Ellerman
2019-07-08 19:14 ` Nathan Chancellor
2019-07-09 5:04 ` Christophe Leroy
2019-07-09 6:49 ` Nathan Chancellor [this message]
2019-07-19 3:24 ` Nathan Chancellor
2019-07-19 15:23 ` Segher Boessenkool
2019-07-19 16:04 ` Nathan Chancellor
2019-07-21 7:58 ` Nathan Chancellor
2019-07-21 18:01 ` Segher Boessenkool
2019-07-22 2:41 ` Nathan Chancellor
2019-07-22 6:19 ` Segher Boessenkool
2019-07-22 17:21 ` Nick Desaulniers
2019-07-22 17:58 ` Segher Boessenkool
2019-07-25 21:30 ` Nick Desaulniers
2019-07-29 20:28 ` Nick Desaulniers
2019-07-22 10:15 ` Michael Ellerman
2019-07-22 15:18 ` Segher Boessenkool
2019-07-22 23:21 ` Michael Ellerman
2019-07-25 13:22 ` Segher Boessenkool
2019-07-22 0:53 ` [PATCH] powerpc: Test broken dcbz kbuild test robot
2019-07-09 13:35 ` [PATCH v2] powerpc: slightly improve cache helpers Segher Boessenkool
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