[all-commits] [llvm/llvm-project] 3fa94a: [compiler-rt] Fix the use of COMPILER_RT_BUILTINS_...

[Paul Osmialowski via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3fa94abb2f19065bd280a737558b6fd01f8a4168
      https://github.com/llvm/llvm-project/commit/3fa94abb2f19065bd280a737558b6fd01f8a4168
  Author: Paul Osmialowski <pawel.osmialowski at arm.com>
  Date:   2026-09-18 (Fri, 18 Sep 2026)

  Changed paths:
    M compiler-rt/cmake/config-ix.cmake

  Log Message:
  -----------
  [compiler-rt] Fix the use of COMPILER_RT_BUILTINS_LIBRARY (#224681)

When `COMPILER_RT_BUILTINS_LIBRARY` is set and a path to the builtins
library is being provided, it is still not being used, causing an
error in the COMPILER_RT_TARGET_HAS_ATOMICS test:

```
    ld.lld: error: undefined symbol: __aarch64_cas8_acq_rel
    >>> referenced by src.cxx
    >>>               CMakeFiles/cmTC_7f91d.dir/src.cxx.o:(main)
    ld.lld: error: undefined symbol: __aarch64_ldadd8_acq_rel
    >>> referenced by src.cxx
    >>>               CMakeFiles/cmTC_7f91d.dir/src.cxx.o:(main)
    >>> referenced by src.cxx
    >>>               CMakeFiles/cmTC_7f91d.dir/src.cxx.o:(main)
    clang++: error: linker command failed with exit code 1
```

Although it is visible in the
build/runtimes/runtimes-bins/CMakeFiles/CMakeConfigureLog.yaml log,
it is being ignored. This causes a cascade of subtle problems down the
line, including a faulty PGO instrumentation code being injected into
instrumented binaries, which causes race conditions whenever the
instrumented code is multi-threaded (a stub is being used instead of
the real atomics).



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