[OpenMP] Don't use MSVC workaround with MinGW

[jdoerfert]

This looks fine to me but it doesn't impact me at all TBH.

@AndreyChurbanov WDYT?

[AndreyChurbanov]

LGTM

Though I didn't test this as I don't have MinGW environment at hand.

[mati865]

Little background:
Recent CMake versions changed behaviour on MinGW and treat .a as static libs only. Currently CMake creates omp.a as the import library and new CMake doesn't like that.

To fix it it's enough to do this change:

-set(LIBOMP_IMP_LIB_FILE ${LIBOMP_LIB_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX})
+set(LIBOMP_IMP_LIB_FILE ${LIBOMP_LIB_NAME}${CMAKE_IMPORT_LIBRARY_SUFFIX})

But I've thought it'd be nice to avoid MSVC hack entirely when targeting MinGW.

[mati865]

At MSYS2 we are using older revision of this patch: https://github.com/msys2/MINGW-packages/commit/e071f276d31a8d214c2f30530eb9ac3ed44fffc7#diff-7f8e056c3dca04423132b5e4e1d36813

If you all agree could you commit the patch, please? I don't have permission to LLVM repo.

[mati865]

Thank you!

[mstorsjo]

@hans - I think this one might be cherrypick-worthy

[hans]

In D85210#2194427, @mstorsjo wrote:

@hans - I think this one might be cherrypick-worthy

Pushed to 11.x as d11e17309414b91c2e7dfc611f098041a62de201. Thanks!

[mati865]

@mstorsjo @hans I apologize but we will have to backport https://reviews.llvm.org/D86552 (should affect only MinGW so it's rather low risk) or revert this cherry-pick on LLVM 11 branch.

[hans]

In D85210#2236706, @mati865 wrote:

@mstorsjo @hans I apologize but we will have to backport https://reviews.llvm.org/D86552 (should affect only MinGW so it's rather low risk) or revert this cherry-pick on LLVM 11 branch.

Okay, I'll backport it once it lands (or revert if it drags out).

[hans]

In D85210#2239033, @hans wrote:

In D85210#2236706, @mati865 wrote:

@mstorsjo @hans I apologize but we will have to backport https://reviews.llvm.org/D86552 (should affect only MinGW so it's rather low risk) or revert this cherry-pick on LLVM 11 branch.

Okay, I'll backport it once it lands (or revert if it drags out).

It's been cherry-picked as 522d80ab553b42e2feadfd4178932069dfc51d3f.

openmp/runtime/cmake/LibompExports.cmake

 endif()
 add_custom_command(TARGET omp POST_BUILD
   COMMAND ${CMAKE_COMMAND} -E make_directory ${LIBOMP_EXPORTS_LIB_DIR}
   COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:omp> ${LIBOMP_EXPORTS_LIB_DIR}
 )
 
 # Copy Windows import library into exports/ directory post build
 if(WIN32)
-  get_target_property(LIBOMPIMP_OUTPUT_DIRECTORY ompimp ARCHIVE_OUTPUT_DIRECTORY)
+  get_target_property(LIBOMPIMP_OUTPUT_DIRECTORY ${LIBOMP_IMP_LIB_TARGET} ARCHIVE_OUTPUT_DIRECTORY)
   if(NOT LIBOMPIMP_OUTPUT_DIRECTORY)
     set(LIBOMPIMP_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
   endif()
-  add_custom_command(TARGET ompimp POST_BUILD
+  add_custom_command(TARGET ${LIBOMP_IMP_LIB_TARGET} POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E make_directory ${LIBOMP_EXPORTS_LIB_DIR}
     COMMAND ${CMAKE_COMMAND} -E copy ${LIBOMPIMP_OUTPUT_DIRECTORY}/${LIBOMP_IMP_LIB_FILE} ${LIBOMP_EXPORTS_LIB_DIR}
   )
 endif()

openmp/runtime/cmake/LibompMicroTests.cmake

 #  - Fails if sees a dependence not listed in td_exp variable below
 #  - Program dependencies: perl, (unix)readelf, (mac)otool[64], (windows)link.exe
 #  - Available for Unix,Mac,Windows, Intel(R) MIC Architecture dynamic builds and Windows
 #    static builds. Not available otherwise.
 
 # get library location
 if(WIN32)
   get_target_property(LIBOMP_OUTPUT_DIRECTORY omp RUNTIME_OUTPUT_DIRECTORY)
-  get_target_property(LIBOMPIMP_OUTPUT_DIRECTORY ompimp ARCHIVE_OUTPUT_DIRECTORY)
+  get_target_property(LIBOMPIMP_OUTPUT_DIRECTORY ${LIBOMP_IMP_LIB_TARGET} ARCHIVE_OUTPUT_DIRECTORY)
   if(NOT LIBOMPIMP_OUTPUT_DIRECTORY)
     set(LIBOMPIMP_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
   endif()
 else()
   get_target_property(LIBOMP_OUTPUT_DIRECTORY omp LIBRARY_OUTPUT_DIRECTORY)
 endif()
 if(NOT LIBOMP_OUTPUT_DIRECTORY)
   set(LIBOMP_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})

openmp/runtime/src/CMakeLists.txt

if(WIN32)
   set_source_files_properties(kmp_import.cpp PROPERTIES COMPILE_FLAGS "${LIBOMP_CONFIGURED_CXXFLAGS}")
   set(LIBOMP_IMP_LIB_FILE ${LIBOMP_LIB_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX})
   set(LIBOMP_GENERATED_IMP_LIB_FILENAME ${LIBOMP_LIB_FILE}${CMAKE_STATIC_LIBRARY_SUFFIX})
   set_target_properties(omp PROPERTIES
     VERSION ${LIBOMP_VERSION_MAJOR}.${LIBOMP_VERSION_MINOR} # uses /version flag
     IMPORT_PREFIX "" IMPORT_SUFFIX "" # control generated import library name when building omp
     ARCHIVE_OUTPUT_NAME ${LIBOMP_GENERATED_IMP_LIB_FILENAME}
   )
+
+  if(MSVC)
     # Get generated import library from creating omp
     get_target_property(LIBOMP_IMPORT_LIB_DIRECTORY omp ARCHIVE_OUTPUT_DIRECTORY)
     if(LIBOMP_IMPORT_LIB_DIRECTORY)
       set(LIBOMP_GENERATED_IMP_LIB ${LIBOMP_IMPORT_LIB_DIRECTORY}/${LIBOMP_GENERATED_IMP_LIB_FILENAME})
     else()
       set(LIBOMP_GENERATED_IMP_LIB ${CMAKE_CURRENT_BINARY_DIR}/${LIBOMP_GENERATED_IMP_LIB_FILENAME})
     endif()
     set_source_files_properties(${LIBOMP_GENERATED_IMP_LIB} PROPERTIES GENERATED TRUE EXTERNAL_OBJECT TRUE)
     # Create new import library that is just the previously created one + kmp_import.cpp
     add_library(ompimp STATIC ${LIBOMP_GENERATED_IMP_LIB} kmp_import.cpp)
     set_target_properties(ompimp PROPERTIES
       PREFIX "" SUFFIX "" OUTPUT_NAME "${LIBOMP_IMP_LIB_FILE}"
       LINKER_LANGUAGE C
     )
     add_dependencies(ompimp omp) # ensure generated import library is created first
+    set(LIBOMP_IMP_LIB_TARGET ompimp)
+  else()
+    set(LIBOMP_IMP_LIB_TARGET omp)
+  endif()
 
   # Create def file to designate exported functions
   libomp_get_gdflags(LIBOMP_GDFLAGS) # generate-def.pl flags (Windows only)
   libomp_string_to_list("${LIBOMP_GDFLAGS}" LIBOMP_GDFLAGS)
   add_custom_command(
     OUTPUT  ${LIBOMP_LIB_NAME}.def
     COMMAND ${PERL_EXECUTABLE} ${LIBOMP_TOOLS_DIR}/generate-def.pl ${LIBOMP_GDFLAGS}
       -o ${LIBOMP_LIB_NAME}.def ${CMAKE_CURRENT_SOURCE_DIR}/dllexports

 if(${OPENMP_STANDALONE_BUILD})
   set(LIBOMP_HEADERS_INSTALL_PATH include)
 else()
   string(REGEX MATCH "[0-9]+\\.[0-9]+(\\.[0-9]+)?" CLANG_VERSION ${PACKAGE_VERSION})
   set(LIBOMP_HEADERS_INSTALL_PATH "${OPENMP_INSTALL_LIBDIR}/clang/${CLANG_VERSION}/include")
 endif()
 if(WIN32)
   install(TARGETS omp RUNTIME DESTINATION bin)
-  install(TARGETS ompimp ARCHIVE DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+  install(TARGETS ${LIBOMP_IMP_LIB_TARGET} ARCHIVE DESTINATION "${OPENMP_INSTALL_LIBDIR}")
   # Create aliases (regular copies) of the library for backwards compatibility
   set(LIBOMP_ALIASES "libiomp5md")
   foreach(alias IN LISTS LIBOMP_ALIASES)
     install(CODE "execute_process(COMMAND \"\${CMAKE_COMMAND}\" -E copy \"${LIBOMP_LIB_FILE}\"
       \"${alias}${LIBOMP_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/bin)")
     install(CODE "execute_process(COMMAND \"\${CMAKE_COMMAND}\" -E copy \"${LIBOMP_IMP_LIB_FILE}\"
       \"${alias}${CMAKE_STATIC_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/${OPENMP_INSTALL_LIBDIR})")
   endforeach()