[OpenMP] Create versioned libgomp softlinks

[ye-luo]

Add libgomp.1.dylib for MacOS and libgomp.so.1 for Linux

Linkers on Mac and Linux pick up versioned libgomp dynamic library files. The existing softlinks (libgomp.dylib for MacOS and libgomp.so for Linux) are insufficient. This helps alleviate the issue of mixing libgomp and libomp at runtime.

[shiltian]

Then change looks fine, but I'm still not clear about the motivation.

[ye-luo]

llvm openmp creates an alias libgomp.so to libomp.so. It is intended to use libomp as a drop-in replacement of libgomp.
However, I found that apps and libraries compiled with GCC and openmp links against libgomp.so.1 not libgomp.so. As a result, libgomp.so --> libomp.so is not enough to serve my needs. To make the aliases working as intended, I added the additional needed aliases.

Big picture, linking both libgomp and libomp may work but it is bad. See https://cpufun.substack.com/p/is-mixing-openmp-runtimes-safe I hit additional issues with affinity control. After fixing the alias, my app only picks up libomp at runtime even if it links a library openblas which was compiled with GCC and linked against libgomp.

[ye-luo]

Ping @shiltian

[shiltian]

If I understand your comment correctly, libgomp.so --> libomp.so, libomp.so.1 --> libomp.so. Eventually you still get the same libomp, no? Not sure if you were trying to say that there is libgomp.so.1 --> libgomp.so (GCC) such that an app eventually picks up libgomp.so.

[ye-luo]

If I understand your comment correctly, libgomp.so --> libomp.so, libomp.so.1 --> libomp.so. Eventually you still get the same libomp, no? Not sure if you were trying to say that there is libgomp.so.1 --> libgomp.so (GCC) such that an app eventually picks up libgomp.so.

Sorry for the confusing. I corrected my type in the above comment. libgomp.so --> libomp.so, libgomp.so.1 --> libomp.so. The intention is to only pick up libomp at runtime.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder openmp-offload-libc-amdgpu-runtime running on omp-vega20-1 while building openmp at step 11 "Add check check-libc-amdgcn-amd-amdhsa".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/7574

Here is the relevant piece of the build log for the reference

Step 11 (Add check check-libc-amdgcn-amd-amdhsa) failure: 1200 seconds without output running [b'ninja', b'-j 32', b'check-libc-amdgcn-amd-amdhsa'], attempting to kill
...
[2559/2681] Linking CXX executable libc/test/src/locale/libc.test.src.locale.locale_test.__hermetic__.__build__
[2560/2681] Linking CXX executable libc/test/src/time/libc.test.src.time.clock_test.__hermetic__.__build__
[2561/2681] Linking CXX executable libc/test/src/string/libc.test.src.string.strxfrm_test.__hermetic__.__build__
[2562/2681] Linking CXX executable libc/test/src/string/libc.test.src.string.strncat_test.__hermetic__.__build__
[2563/2681] Linking CXX executable libc/test/src/inttypes/libc.test.src.inttypes.strtoimax_test.__hermetic__.__build__
[2564/2681] Linking CXX executable libc/test/src/inttypes/libc.test.src.inttypes.strtoumax_test.__hermetic__.__build__
[2565/2681] Linking CXX executable libc/test/src/string/libc.test.src.string.memmove_test.__hermetic__.__build__
[2566/2681] Linking CXX executable libc/test/src/time/libc.test.src.time.clock_gettime_test.__hermetic__.__build__
[2567/2681] Linking CXX executable libc/test/src/stdio/libc.test.src.stdio.asprintf_test.__hermetic__.__build__
[2568/2681] Linking CXX executable libc/test/src/stdio/libc.test.src.stdio.vasprintf_test.__hermetic__.__build__
command timed out: 1200 seconds without output running [b'ninja', b'-j 32', b'check-libc-amdgcn-amd-amdhsa'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1469.198629

[ye-luo]

/cherry-pick eccdb24

[llvmbot]

/pull-request #115944