SingleSource/Regression/C/Regression-C-float16-smoke FAILs to link

[rorth]

When building LLVM 17.0.0 rc1 on both Linux/x86_64 (Ubuntu 20.04) and Solaris 11.4/amd64, the SingleSource/Regression/C/Regression-C-float16-smoke test FAILed to link:

FAILED: SingleSource/Regression/C/Regression-C-float16-smoke 
[...]
Undefined                       first referenced
 symbol                             in file
__extendhfsf2                       SingleSource/Regression/C/CMakeFiles/Regression-C-float16-smoke.dir/float16-smoke.c.o
__truncsfhf2                        SingleSource/Regression/C/CMakeFiles/Regression-C-float16-smoke.dir/float16-smoke.c.o
ld: fatal: symbol referencing errors

The issue is the same, although the root cause is different in both cases. Those functions live in libgcc and were only introduced in GCC 12.

• However, on Ubuntu 20.04 the newest available version of GCC is 10.
• On Solaris 11.4, several versions of GCC are bundled in parallel, up to and including GCC 12 (which would be enough). However, there's a bug in clang that doesn't select the newest version of GCC available but a random one (first in directory order), so on the build machine GCC 10 was chosen.

This test somehow needs to check for the availability of those functions. This test-suite build failure is a regression from LLVM 16.

[tru]

Is this still something that needs to be fixed for 17 final?

[relapids]

@tru Repros for me with 17.0.1 on an Ubuntu 20.04 host. In my case I'm linking using LLD so the output is slightly different but the underlying issue is the same.

[rorth]

This still happens in LLVM 18.1.0 rc2 on Linux/x86_64 (Ubuntu 20.04).

[RamiHg]

Also happens on LLVM 18.1.3 on Windows x86-64.

[violet73]

This also happens in LLVM 18.1.8 on Linux/x86_64 (Ubuntu 18.04).

BTW, how can I pass this test using GCC 12? I have installed GCC 12 but it still failed to link.

[artagnon]

If you have a newer version of GCC installed, simply point the compiler to use that toolchain via "--gcc-install-dir=/path/to/gcc". On RHEL8, I use -DCMAKE_C_FLAGS="--gcc-install-dir=/opt/rh/gcc-toolset-14/root/usr/lib/gcc/x86_64-redhat-linux/14/" when invoking CMake for llvm-test-suite.