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

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Date:   Fri, 19 Jul 2019 09:04:55 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Christophe Leroy <christophe.leroy@....fr>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.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 Fri, Jul 19, 2019 at 10:23:03AM -0500, Segher Boessenkool wrote:
> On Thu, Jul 18, 2019 at 08:24:56PM -0700, Nathan Chancellor wrote:
> > On Mon, Jul 08, 2019 at 11:49:52PM -0700, Nathan Chancellor wrote:
> > > On Tue, Jul 09, 2019 at 07:04:43AM +0200, Christophe Leroy wrote:
> > > > 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).
> > 
> > What disassembly/files did you need to start taking a look at this? I
> > can upload/send whatever you need.
> 
> A before and after of *only this patch*.  And then look at what changed;
> it maybe be obvious what is the problem to you, as well, so look at it
> yourself first?
> 
> 
> Segher

Thanks, I will go ahead and disassemble the full kernel given that those
helpers are everywhere and see what I can find. I'll reach out again if
I can't come up with anything.

Thanks for the advice!
Nathan