Merge branch 'users/meinersbur/flang_runtime' into users/meinersbur/flang_runtime_shared

Author: Meinersbur

flang-rt/CMakeLists.txt

@@ -234,6 +234,9 @@ endif ()
 # but some older versions of CMake don't define it for GCC itself.
 check_cxx_compiler_flag("-UTESTFLAG" FLANG_RT_SUPPORTS_UNDEFINE_FLAG)
 
+# Check whether -fno-lto is supported.
+check_cxx_compiler_flag(-fno-lto FLANG_RT_HAS_FNO_LTO_FLAG)
+
 
 # function checks
 find_package(Backtrace)

flang-rt/cmake/modules/AddFlangRT.cmake

@@ -237,6 +237,13 @@ function (add_flangrt_library name)
       target_compile_options(${tgtname} PUBLIC -U_LIBCPP_ENABLE_ASSERTIONS)
     endif ()
 
+    # When building the flang runtime if LTO is enabled the archive file
+    # contains LLVM IR rather than object code. Currently flang is not
+    # LTO aware so cannot link this file to compiled Fortran code.
+    if (FLANG_RT_HAS_FNO_LTO_FLAG)
+      target_compile_options(${tgtname} PRIVATE -fno-lto)
+    endif ()
+
     # Flang/Clang (including clang-cl) -compiled programs targeting the MSVC ABI
     # should only depend on msvcrt/ucrt. LLVM still emits libgcc/compiler-rt
     # functions in some cases like 128-bit integer math (__udivti3, __modti3,