[libc] [llvm] [libc][math] Refactor cbrt implementation to header-only in src/__support/math folder. (PR #151837)

Sun Aug 3 11:06:05 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-amdgpu-runtime-2` running on `rocm-worker-hw-02` while building `libc,utils` at step 5 "compile-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/10/builds/10756

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (compile-openmp) failure: build (failure)
...
1.160 [4/44/656] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.acos.dir/acos.cpp.o
1.162 [4/43/657] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.scalbnf16.dir/scalbnf16.cpp.o
1.162 [4/42/658] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.asin.dir/asin.cpp.o
1.166 [4/41/659] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.ffma.dir/ffma.cpp.o
1.170 [4/40/660] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.ffmal.dir/ffmal.cpp.o
1.184 [4/39/661] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.atan.dir/atan.cpp.o
1.194 [4/38/662] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.scalbln.dir/scalbln.cpp.o
1.196 [4/37/663] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.atan2l.dir/atan2l.cpp.o
1.197 [4/36/664] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.scalblnf16.dir/scalblnf16.cpp.o
1.201 [4/35/665] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.cbrt.dir/cbrt.cpp.o
FAILED: libc/src/math/generic/CMakeFiles/libc.src.math.generic.cbrt.dir/cbrt.cpp.o 
/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/./bin/clang++ --target=amdgcn-amd-amdhsa -DLIBC_NAMESPACE=__llvm_libc_22_0_0_git -D__LIBC_USE_FLOAT16_CONVERSION -I/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/libc -isystem /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/include/amdgcn-amd-amdhsa -O3 -DNDEBUG --target=amdgcn-amd-amdhsa -DLIBC_QSORT_IMPL=LIBC_QSORT_QUICK_SORT -DLIBC_ADD_NULL_CHECKS "-DLIBC_MATH=(LIBC_MATH_SKIP_ACCURATE_PASS | LIBC_MATH_SMALL_TABLES | LIBC_MATH_NO_ERRNO | LIBC_MATH_NO_EXCEPT)" -DLIBC_ERRNO_MODE=LIBC_ERRNO_MODE_SHARED -DLIBC_THREAD_MODE=LIBC_THREAD_MODE_SINGLE -fpie -DLIBC_FULL_BUILD -nostdlibinc -ffixed-point -fno-exceptions -fno-lax-vector-conversions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -ftrivial-auto-var-init=pattern -fno-omit-frame-pointer -Wall -Wextra -Werror -Wconversion -Wno-sign-conversion -Wdeprecated -Wno-c99-extensions -Wno-gnu-imaginary-constant -Wno-pedantic -Wimplicit-fallthrough -Wwrite-strings -Wextra-semi -Wnewline-eof -Wnonportable-system-include-path -Wstrict-prototypes -Wthread-safety -Wglobal-constructors -nogpulib -fvisibility=hidden -fconvergent-functions -flto -Wno-multi-gpu -Xclang -mcode-object-version=none -DLIBC_COPT_PUBLIC_PACKAGING -UNDEBUG -MD -MT libc/src/math/generic/CMakeFiles/libc.src.math.generic.cbrt.dir/cbrt.cpp.o -MF libc/src/math/generic/CMakeFiles/libc.src.math.generic.cbrt.dir/cbrt.cpp.o.d -o libc/src/math/generic/CMakeFiles/libc.src.math.generic.cbrt.dir/cbrt.cpp.o -c /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/libc/src/math/generic/cbrt.cpp
In file included from /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/libc/src/math/generic/cbrt.cpp:10:
/home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/libc/src/__support/math/cbrt.h:149:9: error: unused type alias 'Float128' [-Werror,-Wunused-local-typedef]
  149 |   using Float128 = fputil::DyadicFloat<128>;
      |         ^
1 error generated.
1.206 [4/34/666] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.scalblnf.dir/scalblnf.cpp.o
1.207 [4/33/667] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16sqrtf.dir/f16sqrtf.cpp.o
1.208 [4/32/668] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.scalbnl.dir/scalbnl.cpp.o
1.211 [4/31/669] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.fsqrt.dir/fsqrt.cpp.o
1.218 [4/30/670] Linking CXX executable /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.build/lib/amdgcn-amd-amdhsa/crt1.o
1.222 [4/29/671] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.fsqrtl.dir/fsqrtl.cpp.o
1.232 [4/28/672] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.atan2.dir/atan2.cpp.o
1.233 [4/27/673] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16sqrt.dir/f16sqrt.cpp.o
1.233 [4/26/674] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.fmaf16.dir/fmaf16.cpp.o
1.235 [4/25/675] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16mul.dir/f16mul.cpp.o
1.240 [4/24/676] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16sqrtl.dir/f16sqrtl.cpp.o
1.242 [4/23/677] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16divl.dir/f16divl.cpp.o
1.246 [4/22/678] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.dmull.dir/dmull.cpp.o
1.248 [4/21/679] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16div.dir/f16div.cpp.o
1.248 [4/20/680] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16divf.dir/f16divf.cpp.o
1.254 [4/19/681] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16addf.dir/f16addf.cpp.o
1.259 [4/18/682] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16subf.dir/f16subf.cpp.o
1.263 [4/17/683] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16mulf.dir/f16mulf.cpp.o
1.264 [4/16/684] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16fmal.dir/f16fmal.cpp.o
1.265 [4/15/685] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16add.dir/f16add.cpp.o
1.270 [4/14/686] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16fmaf.dir/f16fmaf.cpp.o
1.279 [4/13/687] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16subl.dir/f16subl.cpp.o
1.285 [4/12/688] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16addl.dir/f16addl.cpp.o
1.286 [4/11/689] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16sub.dir/f16sub.cpp.o
1.290 [4/10/690] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16mull.dir/f16mull.cpp.o
1.335 [4/9/691] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.f16fma.dir/f16fma.cpp.o
1.430 [4/8/692] Building CXX object libc/src/time/CMakeFiles/libc.src.time.strftime_l.dir/strftime_l.cpp.o
1.461 [4/7/693] Building CXX object libc/src/time/CMakeFiles/libc.src.time.strftime.dir/strftime.cpp.o
1.730 [4/6/694] Building CXX object libc/src/stdio/CMakeFiles/libc.src.stdio.sprintf.dir/sprintf.cpp.o
1.778 [4/5/695] Building CXX object libc/src/stdio/CMakeFiles/libc.src.stdio.vsprintf.dir/vsprintf.cpp.o
1.825 [4/4/696] Building CXX object libc/src/stdio/CMakeFiles/libc.src.stdio.snprintf.dir/snprintf.cpp.o
1.847 [4/3/697] Building CXX object libc/src/stdio/CMakeFiles/libc.src.stdio.vsnprintf.dir/vsnprintf.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/151837