[cmake/AIX] Enhance cmake files to support compiling with gcc on AIX

[Kai]

Summary

This PR allows compiling LLVM on AIX using gcc. Additions are:

• Pass -allow-shlib-undefined to linker
• Export functions with -Wl,-bE:
• Do not pass -O3 and -z defs to linker
• Use -bgc to garbage collect unused code sections

[Kai]

Adding you as reviewers.

[Kai]

Ping.

[jmolloy]

CMakeLists.txt

592

This doesn't match your description. This should mean that AIX does NOT set -Wl,-allow-shlib-undefined, but you said above you wanted -allow-shlib-undefined to be set.

This makes me suspect that CMake is not interpreting your regex correctly.

[Kai]

Superceded by latest additions for AIX.

CMakeLists.txt

set(CMAKE_MODULE_LINKER_FLAGS
     "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-lto_library -Wl,${DARWIN_LTO_LIBRARY}")
 endif()
 
 # Work around a broken bfd ld behavior. When linking a binary with a
 # foo.so library, it will try to find any library that foo.so uses and
 # check its symbols. This is wasteful (the check was done when foo.so
 # was created) and can fail since it is not the dynamic linker and
 # doesn't know how to handle search paths correctly.
-if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS|AIX")
   set(CMAKE_EXE_LINKER_FLAGS
       "${CMAKE_EXE_LINKER_FLAGS} -Wl,-allow-shlib-undefined")
 endif()
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
 include_directories( ${LLVM_INCLUDE_DIR} ${LLVM_MAIN_INCLUDE_DIR})
 
 # when crosscompiling import the executable targets from a file

cmake/modules/AddLLVM.cmake

add_custom_command(OUTPUT ${native_export_file}
       COMMAND echo "  local: *;" >> ${native_export_file}
       COMMAND echo "};" >> ${native_export_file}
       DEPENDS ${export_file}
       VERBATIM
       COMMENT "Creating export file for ${target_name}")
     if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS "  -Wl,-M,${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
+    elseif (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+      set_property(TARGET ${target_name} APPEND_STRING PROPERTY
+                   LINK_FLAGS "  -Wl,-bE:${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
     else()
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS "  -Wl,--version-script,${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
     endif()
   else()
     set(native_export_file "${target_name}.def")
 
     add_custom_command(OUTPUT ${native_export_file}

 
 function(add_link_opts target_name)
   # Don't use linker optimizations in debug builds since it slows down the
   # linker in a context where the optimizations are not important.
   if (NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
 
     # Pass -O3 to the linker. This enabled different optimizations on different
     # linkers.
-    if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS" OR WIN32))
+    if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS|AIX" OR WIN32))
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-O3")
     endif()
 
     if(LLVM_LINKER_IS_GOLD)
       # With gold gc-sections is always safe.
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,--gc-sections")
       # Note that there is a bug with -Wl,--icf=safe so it is not safe
       # to enable. See https://sourceware.org/bugzilla/show_bug.cgi?id=17704.
     endif()
 
     if(NOT LLVM_NO_DEAD_STRIP)
       if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
         # ld64's implementation of -dead_strip breaks tools that use plugins.
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,-dead_strip")
       elseif(${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,-z -Wl,discard-unused=sections")
+      elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+        set_property(TARGET ${target_name} APPEND_STRING PROPERTY
+                     LINK_FLAGS " -Wl,-bgc")
       elseif(NOT WIN32 AND NOT LLVM_LINKER_IS_GOLD)
         # Object files are compiled with -ffunction-data-sections.
         # Versions of bfd ld < 2.23.1 have a bug in --gc-sections that breaks
         # tools that use plugins. Always pass --gc-sections once we require
         # a newer linker.
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,--gc-sections")
       endif()

cmake/modules/HandleLLVMOptions.cmake

if(APPLE)
   # Darwin-specific linker flags for loadable modules.
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()
 
 # Pass -Wl,-z,defs. This makes sure all symbols are defined. Otherwise a DSO
 # build might work on ELF but fail on MachO/COFF.
 if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR CYGWIN OR
         ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD" OR
-        ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD") AND
+        ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD" OR
+        ${CMAKE_SYSTEM_NAME} MATCHES "AIX") AND
    NOT LLVM_USE_SANITIZER)
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")
 endif()
 
 
 function(append value)
   foreach(variable ${ARGN})
     set(${variable} "${${variable}} ${value}" PARENT_SCOPE)