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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Thu, 11 Apr 2019 10:46:30 -0700
Message-ID: <CAKwvOdmmaxgXPQdEEEdGj7pBNeYrnME3=GpthThO1P8owsDD_w@mail.gmail.com>
Subject: Re: [PATCH 1/2] s390: only build for new CPUs with clang
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        clang-built-linux@googlegroups.com,
        Nathan Chancellor <natechancellor@gmail.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Philipp Rudo <prudo@linux.vnet.ibm.com>,
        Tony Krowiak <akrowiak@linux.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Apr 11, 2019 at 3:18 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Thu, Apr 11, 2019 at 12:20 AM 'Nick Desaulniers' via Clang Built
> Linux <clang-built-linux@googlegroups.com> wrote:
> >
> > On Wed, Apr 10, 2019 at 1:13 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > >
> > > llvm does does not understand -march=z9-109 and older target
> >
> > Please file bugs for these in LLVM's issue tracker.  It might be
> > possible to enable these additional architecture variants if they're
> > similar to existing ones and simply unrecognized.  IIRC, we had this
> > issue with armv7 variants.
>
> I really don't see that as necessary here. While generally speaking,
> it would be nice to support the widest possible range of hardware,
> and it would not be hard to add this support, it seems highly unlikely
> that anyone would actually want to use that in case of s390.
>
> The last enterprise distros to support z9 were SLES11 (end of life as
> of last month) and RHEL6 (ending its 10 year life next year). Anyone
> who is still on those releases will probably not install a brand new
> compiler, and anyone who is on newer releases won't run on prehistoric
> hardware.

Are those machine variants worth dropping kernel support for then?

>
> Debian still runs on very old hardware in theory, but even there you'd
> have a hard time finding someone to test the output of the compiler
> on an old machine.
>
>        Arnd


-- 
Thanks,
~Nick Desaulniers