powerpc: clang-nightly: fatal error: error in backend: Trying to obtain a reserved register "r2".

The powerpc clang-nightly version 20.0.0 build warnings / errors noticed on
the Today's Linux next-20241024 tag.

powerpc:
  build:
    * clang-nightly-maple_defconfig
    * clang-nightly-tinyconfig
    * clang-nightly-tqm8xx_defconfig
    * clang-nightly-mpc83xx_defconfig
    * clang-nightly-defconfig
    * clang-nightly-cell_defconfig
    * clang-nightly-ppc64e_defconfig
    * clang-nightly-allnoconfig

Reported-by: Linux Kernel Functional Testing <redacted>

Build errors:
----------
fatal error: error in backend: Trying to obtain a reserved register "r2".
clang: error: clang frontend command failed with exit code 70 (use -v
to see invocation)
Debian clang version 20.0.0
(++20241023112211+699ce16b6284-1~exp1~20241023112229.1038)
Target: powerpc-unknown-linux-gnu

metadata:
----------
kernel: 6.12.0-rc4
git_repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
git_sha: fd21fa4a912ebbf8a6a341c31d8456f61e7d4170
git_describe: next-20241024
Test details: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20241024
config:  https://storage.tuxsuite.com/public/linaro/lkft/builds/2ns7sv9TltSifV46KaGs3BxlB85/config
download_url: https://storage.tuxsuite.com/public/linaro/lkft/builds/2ns7sv9TltSifV46KaGs3BxlB85/
arch: powerpc
toolchain: Clang-nightly (version 20.0.0)

build log link:
------
 - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20241024/testrun/25530243/suite/build/test/clang-nightly-defconfig/log
  - https://storage.tuxsuite.com/public/linaro/lkft/builds/2ns7sv9TltSifV46KaGs3BxlB85/

steps to reproduce:
------
# tuxmake --runtime podman --target-arch powerpc --toolchain
clang-nightly --kconfig defconfig LLVM=1 LLVM_IAS=0
LD=powerpc64le-linux-gnu-ld


--
Linaro LKFT
https://lkft.linaro.org

Hi Naresh,

On Thu, Oct 24, 2024 at 08:35:11PM +0530, Naresh Kamboju wrote:

The powerpc clang-nightly version 20.0.0 build warnings / errors noticed on
the Today's Linux next-20241024 tag.

...

Build errors:
----------
fatal error: error in backend: Trying to obtain a reserved register "r2".

Thanks for the report. I reported this upstream earlier, it should be
resolved now but it will take a little bit for that to filter into
clang-nightly from Debian.

https://github.com/llvm/llvm-project/pull/112603#issuecomment-2430709704

Cheers,
Nathan