[CMake][AIX] Adjust plugin library externsion used on AIX

[Xiangling_L]

Summary

As stated in the CMake manual,
we are supposed to use MODULE rules to generate plugin libraries:

MODULE libraries are plugins that are not linked into other targets but may be loaded dynamically at runtime using dlopen-like functionality

Besides, LLVM's plugin infrastructure fits with the AIX treatment of .so shared objects more than it fits with the AIX treatment of .a library archives (which may contain shared objects).

[hubert.reinterpretcast]

llvm/cmake/modules/HandleLLVMOptions.cmake

155–161

Update comment to encompass the block.

llvm/unittests/Support/DynamicLibrary/CMakeLists.txt

26

The CI failure looks to be related: https://reviews.llvm.org/harbormaster/unit/view/324484/

[stevewan]

llvm/cmake/modules/HandleLLVMOptions.cmake

157–159

My experiment (i.e., cmake --system-information) with cmake3.15.7 on an AIX7.2 machine shown that CMAKE_SHARED_LIBRARY_SUFFIX expanded to .so, am I missing part of the story?

Also, is CMAKE_SHARED_MODULE_SUFFIX a viable option here?

[Xiangling_L]

llvm/cmake/modules/HandleLLVMOptions.cmake

157–159

Yes, before cmake 3.16.0, they use .so as shared library suffix due to consistency with other platforms.

157–159

Yes, before 3.16.0 cmake implements shared library as .so on AIX due to consistency with other platforms. [https://gitlab.kitware.com/cmake/cmake/-/issues/19494] This issue explains more about why cmake is implementing shared library as .a archive library since cmake 3.16.0. In brief, typically in AIX system shared libraries are archive files. This makes it easier to provide updates to the system libraries with minimum impact to the applications.

So we'd like to take advantage of this cmake updates in this patch.

Regading CMAKE_SHARED_MODULE_SUFFIX, I think it's a viable option. It's better than hardcoding .so. Thanks.

[Xiangling_L]

Fix the regression on Linux;

[Xiangling_L]

minor: adjusted the comment;

[daltenty]

LGTM, thanks!

[thakis]

what does LTDL_SHLIB_EXT expand to on aix?

[thakis]

Or, asked differently, is it intentional that llvm/tools/bugpoint/ToolRunner.cpp still uses LTDL_SHLIB_EXT?

[Xiangling_L]

In D96282#2603768, @thakis wrote:

what does LTDL_SHLIB_EXT expand to on aix?

It depends on the cmake version you use. If <3.16.0, it's ".so" shared objects. If >= 3.16.0, it's ".a" archive file

[Xiangling_L]

In D96282#2603772, @thakis wrote:

Or, asked differently, is it intentional that llvm/tools/bugpoint/ToolRunner.cpp still uses LTDL_SHLIB_EXT?

We haven't encountered issues with this so far. And my understanding of MakeSharedObject is more like making a shared library, so LTDL_SHLIB_EXT is a good fit here for AIX.

llvm/cmake/modules/HandleLLVMOptions.cmake

 
 if (CMAKE_SYSTEM_NAME MATCHES "OS390")
   set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
 endif()
 
 set(EXEEXT ${CMAKE_EXECUTABLE_SUFFIX})
 set(LTDL_SHLIB_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
 
 # We use *.dylib rather than *.so on darwin.
+if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  set(LLVM_PLUGIN_EXT ${CMAKE_SHARED_MODULE_SUFFIX})
+else()
   set(LLVM_PLUGIN_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
+endif()
 
 if(APPLE)
   if(LLVM_ENABLE_LLD AND LLVM_ENABLE_LTO)
     message(FATAL_ERROR "lld does not support LTO on Darwin")
   endif()
   # Darwin-specific linker flags for loadable modules.
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()
 

llvm/include/llvm/Config/config.h.cmake

 #cmakedefine01 LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
 
 /* Define if libxml2 is supported on this platform. */
 #cmakedefine LLVM_ENABLE_LIBXML2 ${LLVM_ENABLE_LIBXML2}
 
 /* Define to the extension used for shared libraries, say, ".so". */
 #cmakedefine LTDL_SHLIB_EXT "${LTDL_SHLIB_EXT}"
 
+/* Define to the extension used for plugin libraries, say, ".so". */
+#cmakedefine LLVM_PLUGIN_EXT "${LLVM_PLUGIN_EXT}"
+
 /* Define to the address where bug reports for this package should be sent. */
 #cmakedefine PACKAGE_BUGREPORT "${PACKAGE_BUGREPORT}"
 
 /* Define to the full name of this package. */
 #cmakedefine PACKAGE_NAME "${PACKAGE_NAME}"
 
 /* Define to the full name and version of this package. */
 #cmakedefine PACKAGE_STRING "${PACKAGE_STRING}"

llvm/unittests/Support/DynamicLibrary/CMakeLists.txt

 
 add_llvm_unittest(DynamicLibraryTests
   DynamicLibraryTest.cpp
   )
 target_link_libraries(DynamicLibraryTests PRIVATE DynamicLibraryLib)
 export_executable_symbols(DynamicLibraryTests)
 
 function(dynlib_add_module NAME)
-  add_library(${NAME} SHARED
+  add_library(${NAME} MODULE
     PipSqueak.cpp
     )
   set_target_properties(${NAME} PROPERTIES FOLDER "Tests")
 
   set_output_directory(${NAME}
     BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}
     LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}
     )
 
   set_target_properties(${NAME}
     PROPERTIES PREFIX ""
-    SUFFIX ${LTDL_SHLIB_EXT}
+    SUFFIX ${LLVM_PLUGIN_EXT}
     )
 
   add_dependencies(DynamicLibraryTests ${NAME})
   
   if(LLVM_INTEGRATED_CRT_ALLOC)
     # We need to link in the Support lib for the Memory allocator override,
     # otherwise the DynamicLibrary.Shutdown test will fail, because it would
     # allocate memory with the CRT allocator, and release it with our custom
     # allocator (see llvm/lib/Support/Windows/Memory.inc).
     # /INCLUDE:malloc is there to force searching into LLVMSupport before libucrt
     llvm_map_components_to_libnames(llvm_libs Support)
     target_link_libraries(${NAME} ${llvm_libs} "-INCLUDE:malloc")
   endif()
   
 endfunction(dynlib_add_module)
 
 # Revert -Wl,-z,nodelete on this test since it relies on the file
 # being unloaded.
 if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
-  string(REPLACE "-Wl,-z,nodelete" "" CMAKE_SHARED_LINKER_FLAGS
-    ${CMAKE_SHARED_LINKER_FLAGS})
+  string(REPLACE "-Wl,-z,nodelete" "" CMAKE_MODULE_LINKER_FLAGS
+    ${CMAKE_MODULE_LINKER_FLAGS})
 endif()
 
 dynlib_add_module(PipSqueak)
 dynlib_add_module(SecondLib)

llvm/unittests/Support/DynamicLibrary/DynamicLibraryTest.cpp

 std::string LibPath(const std::string Name = "PipSqueak") {
   const std::vector<testing::internal::string> &Argvs =
       testing::internal::GetArgvs();
   const char *Argv0 =
       Argvs.size() > 0 ? Argvs[0].c_str() : "DynamicLibraryTests";
   void *Ptr = (void*)(intptr_t)TestA;
   std::string Path = fs::getMainExecutable(Argv0, Ptr);
   llvm::SmallString<256> Buf(path::parent_path(Path));
-  path::append(Buf, (Name + LTDL_SHLIB_EXT).c_str());
+  path::append(Buf, (Name + LLVM_PLUGIN_EXT).c_str());
   return std::string(Buf.str());
 }
 
 #if defined(_WIN32) || (defined(HAVE_DLFCN_H) && defined(HAVE_DLOPEN))
 
 typedef void (*SetStrings)(std::string &GStr, std::string &LStr);
 typedef void (*TestOrder)(std::vector<std::string> &V);
 typedef const char *(*GetString)();