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

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Message-ID: <20190719032456.GA14108@archlinux-threadripper>
Date:   Thu, 18 Jul 2019 20:24:56 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        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 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).
> 
> Cheers,
> Nathan

Hi Christophe and Segher,

What disassembly/files did you need to start taking a look at this? I
can upload/send whatever you need.

If it is easier, we have a self contained clang build script available
to make it easier to reproduce this on your side (does assume an x86_64
host):

https://github.com/ClangBuiltLinux/tc-build

Cheers,
Nathan