[AIX][compiler-rt] Build and install standalone libatomic

On AIX, we have to ship `libatomic.a` for compatibility. First, a new `clang_rt.atomic` is added. Second, use added cmake modules for AIX, we are able to build a compatible libatomic.a for AIX. The second step can't be perfectly implemented with cmake now since AIX's archive approach is kinda unique, i.e., archiving shared libraries into a static archive file.

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D102155

compiler-rt/cmake/Modules/CompilerRTAIXUtils.cmake

@@ -0,0 +1,53 @@
+include(CMakeParseArguments)
+include(CompilerRTUtils)
+
+function(get_aix_libatomic_default_link_flags link_flags export_list)
+  set(${link_flags}
+    "-Wl,-H512 -Wl,-D0 \
+     -Wl,-T512 -Wl,-bhalt:4 -Wl,-bernotok \
+     -Wl,-bnoentry -Wl,-bexport:${export_list} \
+     -Wl,-bmodtype:SRE -Wl,-lc" PARENT_SCOPE)
+endfunction()
+
+macro(archive_aix_libatomic name)
+  cmake_parse_arguments(LIB
+    ""
+    ""
+    "ARCHS;PARENT_TARGET"
+    ${ARGN})
+  set(shared_libraries_to_archive "")
+  foreach (arch ${LIB_ARCHS})
+    if(CAN_TARGET_${arch})
+      set(output_dir "${CMAKE_CURRENT_BINARY_DIR}/libatomic-${arch}.dir")
+      # FIXME: Target name should be kept consistent with definition
+      # in AddCompilerRT.cmake added by
+      # add_compiler_rt_runtime(<name> SHARED ...)
+      set(target ${name}-dynamic-${arch})
+      if(TARGET ${target})
+        file(MAKE_DIRECTORY ${output_dir})
+        add_custom_command(OUTPUT "${output_dir}/libatomic.so.1"
+                           POST_BUILD
+                           COMMAND ${CMAKE_COMMAND} -E
+                           copy "$<TARGET_FILE:${target}>"
+                                "${output_dir}/libatomic.so.1"
+                           DEPENDS ${target})
+        list(APPEND shared_libraries_to_archive "${output_dir}/libatomic.so.1")
+      endif()
+    endif()
+  endforeach()
+  if(shared_libraries_to_archive)
+    set(output_dir "")
+    set(install_dir "")
+    get_compiler_rt_output_dir(${COMPILER_RT_DEFAULT_TARGET_ARCH} output_dir)
+    get_compiler_rt_install_dir(${COMPILER_RT_DEFAULT_TARGET_ARCH} install_dir)
+    add_custom_command(OUTPUT "${output_dir}/libatomic.a"
+                       COMMAND ${CMAKE_AR} -X32_64 r "${output_dir}/libatomic.a"
+                       ${shared_libraries_to_archive}
+                       DEPENDS ${shared_libraries_to_archive})
+    install(FILES "${output_dir}/libatomic.a"
+            DESTINATION ${install_dir})
+    add_custom_target(aix-libatomic
+                      DEPENDS "${output_dir}/libatomic.a")
+  endif()
+  add_dependencies(${LIB_PARENT_TARGET} aix-libatomic)
+endmacro()

compiler-rt/lib/builtins/CMakeLists.txt

@@ -48,6 +48,10 @@ endif()
 
 include(builtin-config-ix)
 
+if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  include(CompilerRTAIXUtils)
+endif()
+
 option(COMPILER_RT_BUILTINS_HIDE_SYMBOLS
   "Do not export any symbols from the static library." ON)
 
@@ -747,4 +751,42 @@ else ()
   endforeach ()
 endif ()
 
+option(COMPILER_RT_BUILD_STANDALONE_LIBATOMIC
+  "Build standalone shared atomic library."
+  OFF)
+
+if(COMPILER_RT_BUILD_STANDALONE_LIBATOMIC)
+  add_custom_target(builtins-standalone-atomic)
+  set(BUILTIN_DEPS "")
+  if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+    if(NOT COMPILER_RT_LIBATOMIC_LINK_FLAGS)
+      get_aix_libatomic_default_link_flags(COMPILER_RT_LIBATOMIC_LINK_FLAGS
+        "${CMAKE_CURRENT_SOURCE_DIR}/ppc/atomic.exp")
+    endif()
+    # The compiler needs builtins to link any other binaries, so let
+    # clang_rt.atomic be built after builtins.
+    set(BUILTIN_DEPS builtins)
+  endif()
+  foreach (arch ${BUILTIN_SUPPORTED_ARCH})
+    if(CAN_TARGET_${arch})
+      add_compiler_rt_runtime(clang_rt.atomic
+                              SHARED
+                              ARCHS ${arch}
+                              SOURCES atomic.c
+                              LINK_FLAGS ${COMPILER_RT_LIBATOMIC_LINK_FLAGS}
+                              DEPS ${BUILTIN_DEPS}
+                              PARENT_TARGET builtins-standalone-atomic)
+    endif()
+  endforeach()
+  # FIXME: On AIX, we have to archive built shared libraries into a static
+  # archive, i.e., libatomic.a. Once cmake adds support of such usage for AIX,
+  # this ad-hoc part can be removed.
+  if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+    archive_aix_libatomic(clang_rt.atomic
+                          ARCHS ${BUILTIN_SUPPORTED_ARCH}
+                          PARENT_TARGET builtins-standalone-atomic)
+  endif()
+  add_dependencies(compiler-rt builtins-standalone-atomic)
+endif()
+
 add_dependencies(compiler-rt builtins)

compiler-rt/lib/builtins/ppc/atomic.exp

@@ -0,0 +1,41 @@
+__atomic_compare_exchange
+__atomic_compare_exchange_1
+__atomic_compare_exchange_2
+__atomic_compare_exchange_4
+__atomic_compare_exchange_8
+__atomic_exchange
+__atomic_exchange_1
+__atomic_exchange_2
+__atomic_exchange_4
+__atomic_exchange_8
+__atomic_fetch_add_1
+__atomic_fetch_add_2
+__atomic_fetch_add_4
+__atomic_fetch_add_8
+__atomic_fetch_and_1
+__atomic_fetch_and_2
+__atomic_fetch_and_4
+__atomic_fetch_and_8
+__atomic_fetch_or_1
+__atomic_fetch_or_2
+__atomic_fetch_or_4
+__atomic_fetch_or_8
+__atomic_fetch_sub_1
+__atomic_fetch_sub_2
+__atomic_fetch_sub_4
+__atomic_fetch_sub_8
+__atomic_fetch_xor_1
+__atomic_fetch_xor_2
+__atomic_fetch_xor_4
+__atomic_fetch_xor_8
+__atomic_is_lock_free
+__atomic_load
+__atomic_load_1
+__atomic_load_2
+__atomic_load_4
+__atomic_load_8
+__atomic_store
+__atomic_store_1
+__atomic_store_2
+__atomic_store_4
+__atomic_store_8