[flang][runtime] Support for offload build of FortranDecimal.

flang/cmake/modules/AddFlangOffloadRuntime.cmake

@@ -0,0 +1,132 @@
+option(FLANG_EXPERIMENTAL_CUDA_RUNTIME
+  "Compile Fortran runtime as CUDA sources (experimental)" OFF
+  )
+
+set(FLANG_LIBCUDACXX_PATH "" CACHE PATH "Path to libcu++ package installation")
+
+set(FLANG_EXPERIMENTAL_OMP_OFFLOAD_BUILD "off" CACHE STRING
+  "Compile Fortran runtime as OpenMP target offload sources (experimental). Valid options are 'off', 'host_device', 'nohost'")
+
+set(FLANG_OMP_DEVICE_ARCHITECTURES "all" CACHE STRING
+  "List of OpenMP device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')")
+
+macro(enable_cuda_compilation files)
+  if (FLANG_EXPERIMENTAL_CUDA_RUNTIME)
+    if (BUILD_SHARED_LIBS)
+      message(FATAL_ERROR
+        "BUILD_SHARED_LIBS is not supported for CUDA build of Fortran runtime"
+        )
+    endif()
+
+    enable_language(CUDA)
+
+    # TODO: figure out how to make target property CUDA_SEPARABLE_COMPILATION
+    # work, and avoid setting CMAKE_CUDA_SEPARABLE_COMPILATION.
+    set(CMAKE_CUDA_SEPARABLE_COMPILATION ON)
+
+    # Treat all supported sources as CUDA files.
+    set_source_files_properties(${files} PROPERTIES LANGUAGE CUDA)
+    set(CUDA_COMPILE_OPTIONS)
+    if ("${CMAKE_CUDA_COMPILER_ID}" MATCHES "Clang")
+      # Allow varargs.
+      set(CUDA_COMPILE_OPTIONS
+        -Xclang -fcuda-allow-variadic-functions
+        )
+    endif()
+    if ("${CMAKE_CUDA_COMPILER_ID}" MATCHES "NVIDIA")
+      set(CUDA_COMPILE_OPTIONS
+        --expt-relaxed-constexpr
+        # Disable these warnings:
+        #   'long double' is treated as 'double' in device code
+        -Xcudafe --diag_suppress=20208
+        -Xcudafe --display_error_number
+        )
+    endif()
+    set_source_files_properties(${files} PROPERTIES COMPILE_OPTIONS
+      "${CUDA_COMPILE_OPTIONS}"
+      )
+
+    if (EXISTS "${FLANG_LIBCUDACXX_PATH}/include")
+      # When using libcudacxx headers files, we have to use them
+      # for all files of F18 runtime.
+      include_directories(AFTER ${FLANG_LIBCUDACXX_PATH}/include)
+      add_compile_definitions(RT_USE_LIBCUDACXX=1)
+    endif()
+  endif()
+endmacro()
+
+macro(enable_omp_offload_compilation files)
+  if (NOT FLANG_EXPERIMENTAL_OMP_OFFLOAD_BUILD STREQUAL "off")
+    # 'host_device' build only works with Clang compiler currently.
+    # The build is done with the CMAKE_C/CXX_COMPILER, i.e. it does not use
+    # the in-tree built Clang. We may have a mode that would use the in-tree
+    # built Clang.
+    #
+    # 'nohost' is supposed to produce an LLVM Bitcode library,
+    # and it has to be done with a C/C++ compiler producing LLVM Bitcode
+    # compatible with the LLVM toolchain version distributed with the Flang
+    # compiler.
+    # In general, the in-tree built Clang should be used for 'nohost' build.
+    # Note that 'nohost' build does not produce the host version of Flang
+    # runtime library, so there will be two separate distributable objects.
+    # 'nohost' build is a TODO.
+
+    if (NOT FLANG_EXPERIMENTAL_OMP_OFFLOAD_BUILD STREQUAL "host_device")
+      message(FATAL_ERROR "Unsupported OpenMP offload build of Flang runtime")
+    endif()
+    if (BUILD_SHARED_LIBS)
+      message(FATAL_ERROR
+        "BUILD_SHARED_LIBS is not supported for OpenMP offload build of Fortran runtime"
+        )
+    endif()
+
+    if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" AND
+        "${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
+
+      set(all_amdgpu_architectures
+        "gfx700;gfx701;gfx801;gfx803;gfx900;gfx902;gfx906"
+        "gfx908;gfx90a;gfx90c;gfx940;gfx1010;gfx1030"
+        "gfx1031;gfx1032;gfx1033;gfx1034;gfx1035;gfx1036"
+        "gfx1100;gfx1101;gfx1102;gfx1103;gfx1150;gfx1151"
+        )
+      set(all_nvptx_architectures
+        "sm_35;sm_37;sm_50;sm_52;sm_53;sm_60;sm_61;sm_62"
+        "sm_70;sm_72;sm_75;sm_80;sm_86;sm_89;sm_90"
+        )
+      set(all_gpu_architectures
+        "${all_amdgpu_architectures};${all_nvptx_architectures}"
+        )
+      # TODO: support auto detection on the build system.
+      if (FLANG_OMP_DEVICE_ARCHITECTURES STREQUAL "all")
+        set(FLANG_OMP_DEVICE_ARCHITECTURES ${all_gpu_architectures})
+      endif()
+      list(REMOVE_DUPLICATES FLANG_OMP_DEVICE_ARCHITECTURES)
+
+      string(REPLACE ";" "," compile_for_architectures
+        "${FLANG_OMP_DEVICE_ARCHITECTURES}"
+        )
+
+      set(OMP_COMPILE_OPTIONS
+        -fopenmp
+        -fvisibility=hidden
+        -fopenmp-cuda-mode
+        --offload-arch=${compile_for_architectures}
+        # Force LTO for the device part.
+        -foffload-lto
+        )
+      set_source_files_properties(${files} PROPERTIES COMPILE_OPTIONS
+        "${OMP_COMPILE_OPTIONS}"
+        )
+
+      # Enable "declare target" in the source code.
+      set_source_files_properties(${files}
+        PROPERTIES COMPILE_DEFINITIONS OMP_OFFLOAD_BUILD
+        )
+    else()
+      message(FATAL_ERROR
+        "Flang runtime build is not supported for these compilers:\n"
+        "CMAKE_CXX_COMPILER_ID: ${CMAKE_CXX_COMPILER_ID}\n"
+        "CMAKE_C_COMPILER_ID: ${CMAKE_C_COMPILER_ID}")
+    endif()
+  endif()
+endmacro()

flang/lib/Decimal/CMakeLists.txt

@@ -49,11 +49,17 @@ endif()
 # avoid an unwanted dependency on libstdc++.so.
 add_definitions(-U_GLIBCXX_ASSERTIONS)
 
-add_flang_library(FortranDecimal INSTALL_WITH_TOOLCHAIN
+set(sources
   binary-to-decimal.cpp
   decimal-to-binary.cpp
 )
 
+include(AddFlangOffloadRuntime)
+enable_cuda_compilation("${sources}")
+enable_omp_offload_compilation("${sources}")
+
+add_flang_library(FortranDecimal INSTALL_WITH_TOOLCHAIN ${sources})
+
 if (DEFINED MSVC)
   set(CMAKE_MSVC_RUNTIME_LIBRARY MultiThreaded)
   add_flang_library(FortranDecimal.static INSTALL_WITH_TOOLCHAIN
@@ -77,4 +83,4 @@ if (DEFINED MSVC)
   )
   add_dependencies(FortranDecimal FortranDecimal.static FortranDecimal.dynamic
     FortranDecimal.static_dbg FortranDecimal.dynamic_dbg)
-endif()
+endif()