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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Nick Desaulniers <ndesaulniers@google.com>,
        Segher Boessenkool <segher@kernel.crashing.org>
Cc:     Michael Ellerman <patch-notifications@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Paul Mackerras <paulus@samba.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v4 1/2] powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'
In-Reply-To: <CAKwvOdkKywb1KZ-SDwwuvQEmbsaAzJj9mEPqVG=qw1F5Ogv8rw@mail.gmail.com>
References: <49YBKY13Szz9sT4@ozlabs.org> <20200611224355.71174-1-ndesaulniers@google.com> <20200611235256.GL31009@gate.crashing.org> <CAKwvOdkKywb1KZ-SDwwuvQEmbsaAzJj9mEPqVG=qw1F5Ogv8rw@mail.gmail.com>
Date:   Sat, 13 Jun 2020 20:47:11 +1000
Message-ID: <87366zfdjk.fsf@mpe.ellerman.id.au>
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Nick Desaulniers <ndesaulniers@google.com> writes:

> On Thu, Jun 11, 2020 at 4:53 PM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
>>
>> On Thu, Jun 11, 2020 at 03:43:55PM -0700, Nick Desaulniers wrote:
>> > Segher, Cristophe, I suspect Clang is missing support for the %L and %U
>> > output templates [1].
...
>
> IIUC the bug report correctly, it looks like LLVM is failing for the
> __put_user_asm2_goto case for -m32.  A simple reproducer:
> https://godbolt.org/z/jBBF9b

If you add `-mregnames` you get register names:

https://godbolt.org/z/MxLjhF

foo:
        stw %r3, 0(%r5)
        stw %r4, 4(%r5)
        blr


cheers