linux-kernel - Re: [PATCH v2] powerpc: slightly improve cache helpers

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Date:   Mon, 8 Jul 2019 12:14:16 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v2] powerpc: slightly improve cache helpers

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@...nel.crashing.org>
> > Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> 
> Applied to powerpc next, thanks.
> 
> https://git.kernel.org/powerpc/c/6c5875843b87c3adea2beade9d1b8b3d4523900a
> 
> cheers

This patch causes a regression with clang:

https://travis-ci.com/ClangBuiltLinux/continuous-integration/jobs/213944668

I've attached my local bisect/build log.

Cheers,
Nathan

View attachment "bisect.log" of type "text/plain" (2679 bytes)

View attachment "build.log" of type "text/plain" (91557 bytes)