[Libomptarget] Make libomptarget an LLVM library

This patch makes libomptarget depend on LLVM libraries to be built. The
reason for this is because we already have an implicit dependency on
LLVM headers for ELF identification and extraction as well as an
optional dependenly on the LLVMSupport library for time tracing
information. Furthermore, there are changes in the future that require
using more LLVM libraries, and will heavily simplify some future code as
well as open up the large amount of useful LLVM libraries to
libomptarget.

This will make "standalone" builds of `libomptarget' more difficult for
vendors wishing to ship their own. This will require a sufficiently new
version of LLVM to be installed on the system that should be picked up
by the existing handling for the implicit headers.

The things this patch changes are as follows:
  - `libomptarget.so` links against LLVMSupport and LLVMObject
  - `libomptarget.so` is a symbolic link to `libomptarget.so.15`
  - If using a shared library build, user applications will depend on LLVM
    libraries as well
  - We can now use LLVM resources in Libomptarget.

Note that this patch only changes this to apply to libomptarget itself,
not the plugins. Additional patches will be necessary for that.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D129875

openmp/libomptarget/CMakeLists.txt

@@ -86,7 +86,8 @@ set(LIBOMPTARGET_OPENMP_HEADER_FOLDER "${LIBOMP_INCLUDE_DIR}" CACHE STRING
   "Path to folder containing omp.h")
 set(LIBOMPTARGET_OPENMP_HOST_RTL_FOLDER "${LIBOMP_LIBRARY_DIR}" CACHE STRING
   "Path to folder containing libomp.so, and libLLVMSupport.so with profiling enabled")
-
+set(LIBOMPTARGET_LLVM_LIBRARY_DIR "${LLVM_LIBRARY_DIR}" CACHE STRING
+  "Path to folder containing llvm library libomptarget.so")
 
 # Build offloading plugins and device RTLs if they are available.
 add_subdirectory(plugins)

openmp/libomptarget/src/CMakeLists.txt

@@ -12,35 +12,32 @@
 
 libomptarget_say("Building offloading runtime library libomptarget.")
 
-set(LIBOMPTARGET_SRC_FILES
-  ${CMAKE_CURRENT_SOURCE_DIR}/api.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/device.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/interface.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/interop.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/omptarget.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/rtl.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/LegacyAPI.cpp
-)
+add_llvm_library(omptarget
+  SHARED
 
-set(LIBOMPTARGET_SRC_FILES ${LIBOMPTARGET_SRC_FILES} PARENT_SCOPE)
+  api.cpp
+  device.cpp
+  interface.cpp
+  interop.cpp
+  omptarget.cpp
+  rtl.cpp
+  LegacyAPI.cpp
 
-# Build libomptarget library with libdl dependency.
-add_library(omptarget SHARED ${LIBOMPTARGET_SRC_FILES})
-set_target_properties(omptarget PROPERTIES INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN")
-if (OPENMP_ENABLE_LIBOMPTARGET_PROFILING)
-  # Add LLVMSupport dependency if profiling is enabled.
-  # Linking with LLVM component libraries also requires
-  # aligning the compile flags.
-  llvm_update_compile_flags(omptarget)
-  target_compile_definitions(omptarget PUBLIC OMPTARGET_PROFILE_ENABLED)
-  target_link_libraries(omptarget PRIVATE LLVMSupport)
-endif()
-target_include_directories(omptarget PRIVATE
-  ${LIBOMPTARGET_INCLUDE_DIR})
-target_link_libraries(omptarget PRIVATE
+  ADDITIONAL_HEADER_DIRS
+  ${LIBOMPTARGET_INCLUDE_DIR}
+
+  LINK_COMPONENTS
+  Support
+  Object
+
+  LINK_LIBS
   ${CMAKE_DL_LIBS}
-  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports")
+  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports"
+  NO_INSTALL_RPATH
+)
+target_include_directories(omptarget PRIVATE ${LIBOMPTARGET_INCLUDE_DIR})
 
-# Install libomptarget under the lib destination folder.
-install(TARGETS omptarget LIBRARY COMPONENT omptarget
-  DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+# libomptarget.so needs to be aware of where the plugins live as they
+# are now separated in the build directory.
+set_target_properties(omptarget PROPERTIES INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
+install(TARGETS omptarget LIBRARY COMPONENT omptarget DESTINATION "${OPENMP_INSTALL_LIBDIR}")

openmp/libomptarget/test/lit.cfg

@@ -98,6 +98,7 @@ elif config.operating_system == 'Darwin':
 else: # Unices
     config.test_flags += " -Wl,-rpath," + config.library_dir
     config.test_flags += " -Wl,-rpath," + config.omp_host_rtl_directory
+    config.test_flags += " -Wl,-rpath," + config.llvm_lib_directory
     if config.cuda_libdir:
         config.test_flags += " -Wl,-rpath," + config.cuda_libdir
     if config.libomptarget_current_target.startswith('amdgcn'):

openmp/libomptarget/test/lit.site.cfg.in

@@ -12,6 +12,7 @@ config.libomptarget_obj_root = "@CMAKE_CURRENT_BINARY_DIR@/@CURRENT_TARGET@"
 config.library_dir = "@LIBOMPTARGET_LIBRARY_DIR@"
 config.omp_header_directory = "@LIBOMPTARGET_OPENMP_HEADER_FOLDER@"
 config.omp_host_rtl_directory = "@LIBOMPTARGET_OPENMP_HOST_RTL_FOLDER@"
+config.llvm_lib_directory = "@LIBOMPTARGET_LLVM_LIBRARY_DIR@"
 config.operating_system = "@CMAKE_SYSTEM_NAME@"
 config.libomptarget_all_targets = "@LIBOMPTARGET_ALL_TARGETS@".split()
 config.libomptarget_current_target = "@CURRENT_TARGET@"