[AIX] Update rpath for BUILD_SHARED_LIBS

[jsji]

Summary

BUILD_SHARED_LIBS build llvm component as shared library,
which can reduce the size a lot.

Normally, the binary use ORIGIN../lib to load component libraries,
unfortunatly, ORIGIN is not supported by AIX ld.

We hardcoded the build lib and install lib path in rpath for now
to enable BUILD_SHARED_LIBS build.

Understand that this is not perfect solution,
we can update this when we find better solution.

[hubert.reinterpretcast]

llvm/cmake/modules/AddLLVM.cmake

2113

How should LLVM_LIBRARY_DIR (used with extra_libdir) be incorporated (or not) here?

llvm/cmake/modules/HandleLLVMOptions.cmake

218

Minor wording/grammar nits.

[jsji]

llvm/cmake/modules/AddLLVM.cmake

2113

I can include extra_libdir if we want to support LLVM_INSTALL_PREFIX as well.

[hubert.reinterpretcast]

llvm/cmake/modules/AddLLVM.cmake

2113

Thanks. I think adding extra_libdir makes sense to reduce unnecessary differences.

[jsji]

Address comments.

[hubert.reinterpretcast]

LGTM; thanks!

llvm/cmake/modules/AddLLVM.cmake

if(LLVM_INSTALL_PREFIX AND NOT (LLVM_INSTALL_PREFIX STREQUAL CMAKE_INSTALL_PREFIX))
     set(extra_libdir ${LLVM_LIBRARY_DIR})
   elseif(LLVM_BUILD_LIBRARY_DIR)
     set(extra_libdir ${LLVM_LIBRARY_DIR})
   endif()
 
   if (APPLE)
     set(_install_name_dir INSTALL_NAME_DIR "@rpath")
     set(_install_rpath "@loader_path/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+  elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND BUILD_SHARED_LIBS)
+    # $ORIGIN is not interpreted at link time by aix ld.
+    # Since BUILD_SHARED_LIBS is only recommended for use by developers,
+    # hardcode the rpath to build/install lib dir first in this mode.
+    # FIXME: update this when there is better solution.
+    set(_install_rpath "${LLVM_LIBRARY_OUTPUT_INTDIR}" "${CMAKE_INSTALL_PREFIX}/lib${LLVM_LIBDIR_SUFFIX}")
   elseif(UNIX)
     set(_install_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
     if(${CMAKE_SYSTEM_NAME} MATCHES "(FreeBSD|DragonFly)")
       set_property(TARGET ${name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-z,origin ")
     endif()
     if(LLVM_LINKER_IS_GNULD)
       # $ORIGIN is not interpreted at link time by ld.bfd

llvm/cmake/modules/HandleLLVMOptions.cmake

append("-Wl,-bbigtoc"
            CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
     # The default behaviour on AIX processes dynamic initialization of non-local variables with
     # static storage duration even for archive members that are otherwise unreferenced.
     # Since `--whole-archive` is not used by the LLVM build to keep such initializations for Linux,
     # we can limit the processing for archive members to only those that are otherwise referenced.
     append("-bcdtors:mbr"
            CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
   endif()
+  if(BUILD_SHARED_LIBS)
+    # See rpath handling in AddLLVM.cmake
+    # FIXME: Remove this warning if this rpath is no longer hardcoded.
+    message(WARNING "Build and install environment path info may be exposed, binaries also unrelocatable.")
+  endif()
 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|FreeBSD|OpenBSD|DragonFly|AIX|SunOS|OS390" OR
         WIN32 OR CYGWIN) AND
    NOT LLVM_USE_SANITIZER)
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")