[Offload][WIP] Move /openmp/libomptarget to /offload

** This is still WIP - Testing is needed **

In a nutshell, this moves our libomptarget code to create the offload
subproject. For now, we allow LLVM/Offload only as runtime. Tests and
other components still depend on OpenMP and have also not been renamed.
The results below are for a build in which OpenMP and Offload are
enabled runtimes. In addition to the pure `git mv`, I needed to adjust
some CMake files. Nothing is intended to change semantics but some of
the things likely broke other build configurations. Testers are needed.

```
ninja -C build/llvm/runtimes/runtimes-bins check-libomptarget
```
Works with the X86 and AMDGPU offload tests

```
ninja -C /build/llvm/ check-openmp
```
Still works but doesn't build offload tests anymore.

```
ls install/lib
```
Shows all expected libraries, incl.
- `libomptarget.devicertl.a`
- `libomptarget-nvptx-sm_90.bc`
- `libomptarget.rtl.amdgpu.so` -> `libomptarget.rtl.amdgpu.so.18git`
- `libomptarget.so` -> `libomptarget.so.18git`

Fixes: llvm#75124

Author: jdoerfert

llvm/CMakeLists.txt

@@ -156,7 +156,7 @@ endif()
 # As we migrate runtimes to using the bootstrapping build, the set of default runtimes
 # should grow as we remove those runtimes from LLVM_ENABLE_PROJECTS above.
 set(LLVM_DEFAULT_RUNTIMES "libcxx;libcxxabi;libunwind")
-set(LLVM_SUPPORTED_RUNTIMES "libc;libunwind;libcxxabi;pstl;libcxx;compiler-rt;openmp;llvm-libgcc")
+set(LLVM_SUPPORTED_RUNTIMES "libc;libunwind;libcxxabi;pstl;libcxx;compiler-rt;openmp;llvm-libgcc;offload")
 set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
   "Semicolon-separated list of runtimes to build, or \"all\" (${LLVM_DEFAULT_RUNTIMES}). Supported runtimes are ${LLVM_SUPPORTED_RUNTIMES}.")
 if(LLVM_ENABLE_RUNTIMES STREQUAL "all")

openmp/libomptarget/CMakeLists.txt renamed to offload/CMakeLists.txt

@@ -10,12 +10,98 @@
 #
 ##===----------------------------------------------------------------------===##
 
-if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
-  message(FATAL_ERROR "Direct configuration not supported, please use parent directory!")
+set(ENABLE_LIBOMPTARGET ON)
+# Currently libomptarget cannot be compiled on Windows or MacOS X.
+# Since the device plugins are only supported on Linux anyway,
+# there is no point in trying to compile libomptarget on other OSes.
+# 32-bit systems are not supported either.
+if (APPLE OR WIN32 OR NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES OR NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+  set(ENABLE_LIBOMPTARGET OFF)
 endif()
 
-# Add cmake directory to search for custom cmake functions.
-set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules ${CMAKE_MODULE_PATH})
+option(OPENMP_ENABLE_LIBOMPTARGET "Enable building libomptarget for offloading."
+       ${ENABLE_LIBOMPTARGET})
+if (OPENMP_ENABLE_LIBOMPTARGET)
+  # Check that the library can actually be built.
+  if (APPLE OR WIN32)
+    message(FATAL_ERROR "libomptarget cannot be built on Windows and MacOS X!")
+  elseif (NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+    message(FATAL_ERROR "Host compiler must support C++17 to build libomptarget!")
+  elseif (NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+    message(FATAL_ERROR "libomptarget on 32-bit systems are not supported!")
+  endif()
+endif()
+
+# TODO: Leftover from the move, could probably be just LLVM_LIBDIR_SUFFIX everywhere.
+set(OFFLOAD_INSTALL_LIBDIR "lib${LLVM_LIBDIR_SUFFIX}")
+
+set(LLVM_COMMON_CMAKE_UTILS ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
+
+# Add path for custom modules
+list(INSERT CMAKE_MODULE_PATH 0
+  "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
+  "${LLVM_COMMON_CMAKE_UTILS}/Modules"
+  )
+
+if (OPENMP_STANDALONE_BUILD)
+  # CMAKE_BUILD_TYPE was not set, default to Release.
+  if (NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Release)
+  endif()
+
+  # Group common settings.
+  set(OPENMP_ENABLE_WERROR FALSE CACHE BOOL
+    "Enable -Werror flags to turn warnings into errors for supporting compilers.")
+  set(OPENMP_LIBDIR_SUFFIX "" CACHE STRING
+    "Suffix of lib installation directory, e.g. 64 => lib64")
+  # Do not use OPENMP_LIBDIR_SUFFIX directly, use OPENMP_INSTALL_LIBDIR.
+  set(OPENMP_INSTALL_LIBDIR "lib${OPENMP_LIBDIR_SUFFIX}")
+
+  # Group test settings.
+  set(OPENMP_TEST_C_COMPILER ${CMAKE_C_COMPILER} CACHE STRING
+    "C compiler to use for testing OpenMP runtime libraries.")
+  set(OPENMP_TEST_CXX_COMPILER ${CMAKE_CXX_COMPILER} CACHE STRING
+    "C++ compiler to use for testing OpenMP runtime libraries.")
+  set(OPENMP_TEST_Fortran_COMPILER ${CMAKE_Fortran_COMPILER} CACHE STRING
+    "FORTRAN compiler to use for testing OpenMP runtime libraries.")
+  set(OPENMP_LLVM_TOOLS_DIR "" CACHE PATH "Path to LLVM tools for testing.")
+
+  set(CMAKE_CXX_STANDARD 17 CACHE STRING "C++ standard to conform to")
+  set(CMAKE_CXX_STANDARD_REQUIRED NO)
+  set(CMAKE_CXX_EXTENSIONS NO)
+else()
+  set(OPENMP_ENABLE_WERROR ${LLVM_ENABLE_WERROR})
+  # If building in tree, we honor the same install suffix LLVM uses.
+  set(OPENMP_INSTALL_LIBDIR "lib${LLVM_LIBDIR_SUFFIX}")
+
+  if (NOT MSVC)
+    set(OPENMP_TEST_C_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
+    set(OPENMP_TEST_CXX_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++)
+  else()
+    set(OPENMP_TEST_C_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang.exe)
+    set(OPENMP_TEST_CXX_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++.exe)
+  endif()
+
+  # Check for flang
+  if (NOT MSVC)
+    set(OPENMP_TEST_Fortran_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/flang-new)
+  else()
+    set(OPENMP_TEST_Fortran_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/flang-new.exe)
+  endif()
+
+  # Set fortran test compiler if flang is found
+  if (EXISTS "${OPENMP_TEST_Fortran_COMPILER}")
+    message("Using local flang build at ${OPENMP_TEST_Fortran_COMPILER}")
+  else()
+    unset(OPENMP_TEST_Fortran_COMPILER)
+  endif()
+
+  # If not standalone, set CMAKE_CXX_STANDARD but don't set the global cache value,
+  # only set it locally for OpenMP.
+  set(CMAKE_CXX_STANDARD 17)
+  set(CMAKE_CXX_STANDARD_REQUIRED NO)
+  set(CMAKE_CXX_EXTENSIONS NO)
+endif()
 
 # Set the path of all resulting libraries to a unified location so that it can
 # be used for testing.
@@ -36,6 +122,9 @@ include(LibomptargetUtils)
 # Get dependencies for the different components of the project.
 include(LibomptargetGetDependencies)
 
+# Set up testing infrastructure.
+include(OpenMPTesting)
+
 # LLVM source tree is required at build time for libomptarget
 if (NOT LIBOMPTARGET_LLVM_INCLUDE_DIRS)
   message(FATAL_ERROR "Missing definition for LIBOMPTARGET_LLVM_INCLUDE_DIRS")
@@ -129,11 +218,6 @@ set(LIBOMPTARGET_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)
 message(STATUS "OpenMP tools dir in libomptarget: ${LIBOMP_OMP_TOOLS_INCLUDE_DIR}")
 include_directories(${LIBOMP_OMP_TOOLS_INCLUDE_DIR})
 
-# Definitions for testing, for reuse when testing libomptarget-nvptx.
-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 "${LLVM_LIBRARY_DIR}" CACHE STRING
   "Path to folder containing llvm library libomptarget.so")
 set(LIBOMPTARGET_LLVM_LIBRARY_INTDIR "${LIBOMPTARGET_INTDIR}" CACHE STRING

openmp/libomptarget/DeviceRTL/CMakeLists.txt renamed to offload/DeviceRTL/CMakeLists.txt

@@ -228,7 +228,7 @@ function(compileDeviceRTLLibrary target_cpu target_name target_triple)
   set_property(DIRECTORY APPEND PROPERTY ADDITIONAL_MAKE_CLEAN_FILES ${bclib_name} ${LIBOMPTARGET_LIBRARY_DIR}/${bclib_name})
 
   # Install bitcode library under the lib destination folder.
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name} DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name} DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")
 
   set(target_feature "")
   if("${target_triple}" STREQUAL "nvptx64-nvidia-cuda")
@@ -307,4 +307,4 @@ set_target_properties(omptarget.devicertl PROPERTIES
 )
 target_link_libraries(omptarget.devicertl PRIVATE omptarget.devicertl.all_objs)
 
-install(TARGETS omptarget.devicertl ARCHIVE DESTINATION ${OPENMP_INSTALL_LIBDIR})
+install(TARGETS omptarget.devicertl ARCHIVE DESTINATION ${OFFLOAD_INSTALL_LIBDIR})

openmp/libomptarget/DeviceRTL/include/Allocator.h renamed to offload/DeviceRTL/include/Allocator.h

@@ -65,7 +65,7 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "${tmachine}$")
 
     # Install plugin under the lib destination folder.
     install(TARGETS "omptarget.rtl.${tmachine_libname}"
-      LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+      LIBRARY DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")
     set_target_properties("omptarget.rtl.${tmachine_libname}" PROPERTIES
       INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
       POSITION_INDEPENDENT_CODE ON

openmp/libomptarget/DeviceRTL/include/Configuration.h renamed to offload/DeviceRTL/include/Configuration.h

@@ -120,7 +120,7 @@ else()
 endif()
 
 # Install plugin under the lib destination folder.
-install(TARGETS omptarget.rtl.amdgpu LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+install(TARGETS omptarget.rtl.amdgpu LIBRARY DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.amdgpu PROPERTIES
   INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
   CXX_VISIBILITY_PRESET protected)

openmp/libomptarget/DeviceRTL/include/Debug.h renamed to offload/DeviceRTL/include/Debug.h

@@ -81,7 +81,7 @@ else()
 endif()
 
 # Install plugin under the lib destination folder.
-install(TARGETS omptarget.rtl.cuda LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+install(TARGETS omptarget.rtl.cuda LIBRARY DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.cuda PROPERTIES
   INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
   CXX_VISIBILITY_PRESET protected)

openmp/libomptarget/DeviceRTL/include/Interface.h renamed to offload/DeviceRTL/include/Interface.h

@@ -85,4 +85,4 @@ set_target_properties(omptarget PROPERTIES
                       POSITION_INDEPENDENT_CODE ON
                       INSTALL_RPATH "$ORIGIN"
                       BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
-install(TARGETS omptarget LIBRARY COMPONENT omptarget DESTINATION "${OPENMP_INSTALL_LIBDIR}")
+install(TARGETS omptarget LIBRARY COMPONENT omptarget DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")