From: Tony Ambardar <tony.ambardar@gmail.com>
To: Yonghong Song <yonghong.song@linux.dev>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>,
bpf@vger.kernel.org, linux-s390@vger.kernel.org,
llvm@lists.linux.dev, Alexei Starovoitov <ast@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>
Subject: Re: Problem testing with S390x under QEMU on x86_64
Date: Mon, 26 Aug 2024 03:50:28 -0700 [thread overview]
Message-ID: <Zsxd9HskofXttp+p@kodidev-ubuntu> (raw)
In-Reply-To: <c8c590b2-40b2-4cc0-9eb7-410dbd080a49@linux.dev>
On Sun, Aug 25, 2024 at 01:23:51PM -0700, Yonghong Song wrote:
>
> On 8/24/24 4:21 PM, Tony Ambardar wrote:
[snip]
> >
> > Test '#525 verif_scale_pyperf600:FAIL' was caused by clang miscompilation
> > exposed by my use of clang-19 and clang-20. The test passes when built
> > with clang-17 (used by BPF CI) or clang-18 which I switched to use.
>
> x86 has the same issue where clang19 generated code will cause verification
> failure. Eduard is working on this.
>
> >
> > One symptom of the problem is easily seen by manually compiling:
> >
> > $ clang-18 -g -Wall -Werror -D__TARGET_ARCH_s390 -mbig-endian -Itools/testing/selftests/bpf/tools/include -Itools/testing/selftests/bpf -Itools/include/uapi -Itools/testing/selftests/usr/include -Wno-compare-distinct-pointer-types -idirafter /usr/lib/llvm-18/lib/clang/18/include -idirafter /usr/local/include -idirafter /usr/lib/gcc-cross/s390x-linux-gnu/11/../../../../s390x-linux-gnu/include -idirafter /usr/include/s390x-linux-gnu -idirafter /usr/include -DENABLE_ATOMICS_TESTS -O2 --target=bpfeb -c tools/testing/selftests/bpf/progs/pyperf600.c -mcpu=v3 -o pyperf600.clang18.bpf.o
> >
> > $ clang-19 -g -Wall -Werror -D__TARGET_ARCH_s390 -mbig-endian -Itools/testing/selftests/bpf/tools/include -Itools/testing/selftests/bpf -Itools/include/uapi -Itools/testing/selftests/usr/include -Wno-compare-distinct-pointer-types -idirafter /usr/lib/llvm-19/lib/clang/19/include -idirafter /usr/local/include -idirafter /usr/lib/gcc-cross/s390x-linux-gnu/11/../../../../s390x-linux-gnu/include -idirafter /usr/include/s390x-linux-gnu -idirafter /usr/include -DENABLE_ATOMICS_TESTS -O2 --target=bpfeb -c tools/testing/selftests/bpf/progs/pyperf600.c -mcpu=v3 -o pyperf600.clang19.bpf.o
> >
> > $ llvm-readelf-18 -S pyperf600.clang{18,19}.bpf.o |grep .symtab
> > [27] .symtab SYMTAB 0000000000000000 1739d0 01ad60 18 1 4572 8
> > [27] .symtab SYMTAB 0000000000000000 14f048 0001e0 18 1 12 8
> >
> > Notice that the .symtab has shrunk by ~200X for example going to clang-19!
> > (CCing llvm maintainers)
>
> This is a known issue. In llvm18, all labels (to identify basic blocks) are in symbol table.
> Those labels are removed from symbol table in llvm19.
Glad to hear this a known issue being looked at now. A quick search on my part found nothing, so sorry for the noise and thanks for clarifying.
>
> >
> >
> > Kind regards,
> > Tony
> >
prev parent reply other threads:[~2024-08-26 10:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-17 21:57 Problem testing with S390x under QEMU on x86_64 Tony Ambardar
2024-08-19 9:15 ` Ilya Leoshkevich
2024-08-21 0:38 ` Tony Ambardar
2024-08-21 17:28 ` Ilya Leoshkevich
2024-08-23 13:29 ` Leon Hwang
2024-08-24 23:21 ` Tony Ambardar
2024-08-25 20:23 ` Yonghong Song
2024-08-26 10:50 ` Tony Ambardar [this message]
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