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selftests/bpf: Fix pyperf180 compilation failure with llvm18 #658

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selftests/bpf: Fix pyperf180 compilation failure with llvm18 #658

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danielocfb
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Pull request for series with
subject: selftests/bpf: Fix pyperf180 compilation failure with llvm18
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825

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Upstream branch: b4e59c1
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

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Upstream branch: b4e59c1
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 74ae083 to 44730f1 Compare November 9, 2023 18:00
@danielocfb danielocfb force-pushed the bpf-next_base branch 2 times, most recently from 902178a to bc1b833 Compare November 9, 2023 18:41
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Upstream branch: 3815f89
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 44730f1 to e2b91a5 Compare November 9, 2023 18:43
@danielocfb danielocfb force-pushed the bpf-next_base branch 2 times, most recently from 0fbe9f3 to b0d20d2 Compare November 9, 2023 19:02
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Upstream branch: 6f101db
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from e2b91a5 to 838b402 Compare November 9, 2023 19:04
@danielocfb danielocfb force-pushed the bpf-next_base branch 2 times, most recently from 1e02037 to a98cbca Compare November 9, 2023 19:19
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 838b402 to 1c45772 Compare November 9, 2023 19:22
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 1c45772 to 4103899 Compare November 9, 2023 20:40
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 4103899 to 32a9ec8 Compare November 9, 2023 21:07
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from 32a9ec8 to d6c14bd Compare November 9, 2023 21:16
@d-e-s-o
selftests/bpf: Fix pyperf180 compilation failure with llvm18
08dfd3a 
With latest llvm18 (main branch of llvm-project repo), when building bpf selftests,
    [~/work/bpf-next (master)]$ make -C tools/testing/selftests/bpf LLVM=1 -j

The following compilation error happens:
    fatal error: error in backend: Branch target out of insn range
    ...
    Stack dump:
    0.      Program arguments: clang -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian
      -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include
      -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -I/home/yhs/work/bpf-next/tools/include/uapi
      -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include -idirafter
      /home/yhs/work/llvm-project/llvm/build.18/install/lib/clang/18/include -idirafter /usr/local/include
      -idirafter /usr/include -Wno-compare-distinct-pointer-types -DENABLE_ATOMICS_TESTS -O2 --target=bpf
      -c progs/pyperf180.c -mcpu=v3 -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/pyperf180.bpf.o
    1.      <eof> parser at end of file
    2.      Code generation
    ...

The compilation failure only happens to cpu=v2 and cpu=v3. cpu=v4 is okay
since cpu=v4 supports 32-bit branch target offset.

The above failure is due to upstream llvm patch [1] where some inlining behavior
are changed in llvm18.

To workaround the issue, previously all 180 loop iterations are fully unrolled.
Now, the fully unrolling count is changed to 90 for llvm18 and later. This reduced
some otherwise long branch target distance, and fixed the compilation failure.

  [1] llvm/llvm-project@1a2e77c

Signed-off-by: Yonghong Song <[email protected]>
Tested-by: Eduard Zingerman <[email protected]>
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Upstream branch: 155addf
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=799825
version: 1

@danielocfb danielocfb force-pushed the series/799825=>bpf-next branch from d6c14bd to 08dfd3a Compare November 10, 2023 04:48
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=799825 expired. Closing PR.

@danielocfb danielocfb closed this Nov 10, 2023
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