[cmake] Simplify llvm_update_compile_flags

[Trass3r]

Summary

Using modern CMake for language-specific flags.

[ldionne]

LGTM but I have never used that function. I don't think the runtimes make use of it.

llvm/cmake/modules/AddLLVM.cmake

 include(GNUInstallDirs)
 include(LLVMDistributionSupport)
 include(LLVMProcessSources)
 include(LLVM-Config)
 include(DetermineGCCCompatible)
 
 function(llvm_update_compile_flags name)
-  get_property(sources TARGET ${name} PROPERTY SOURCES)
-  if("${sources}" MATCHES "\\.c(;|$)")
-    set(update_src_props ON)
-  endif()
-
-  list(APPEND LLVM_COMPILE_CFLAGS " ${LLVM_COMPILE_FLAGS}")
+  target_compile_options(${name} PRIVATE ${LLVM_COMPILE_FLAGS})
 
   # LLVM_REQUIRES_EH is an internal flag that individual targets can use to
   # force EH
   if(LLVM_REQUIRES_EH OR LLVM_ENABLE_EH)
     if(NOT (LLVM_REQUIRES_RTTI OR LLVM_ENABLE_RTTI))
       message(AUTHOR_WARNING "Exception handling requires RTTI. Enabling RTTI for ${name}")
       set(LLVM_REQUIRES_RTTI ON)
     endif()
elseif (MSVC)
       list(APPEND LLVM_COMPILE_FLAGS "/GR-")
     elseif (CMAKE_CXX_COMPILER_ID MATCHES "XL")
       list(APPEND LLVM_COMPILE_FLAGS "-qnortti")
     endif ()
   elseif(MSVC)
     list(APPEND LLVM_COMPILE_FLAGS "/GR")
   endif()
 
-  # Assume that;
-  #   - LLVM_COMPILE_FLAGS is list.
-  #   - PROPERTY COMPILE_FLAGS is string.
-  string(REPLACE ";" " " target_compile_flags " ${LLVM_COMPILE_FLAGS}")
-  string(REPLACE ";" " " target_compile_cflags " ${LLVM_COMPILE_CFLAGS}")
-
-  if(update_src_props)
-    foreach(fn ${sources})
-      get_filename_component(suf ${fn} EXT)
-      if("${suf}" STREQUAL ".cpp")
-        set_property(SOURCE ${fn} APPEND_STRING PROPERTY
-          COMPILE_FLAGS "${target_compile_flags}")
-      endif()
-      if("${suf}" STREQUAL ".c")
-        set_property(SOURCE ${fn} APPEND_STRING PROPERTY
-          COMPILE_FLAGS "${target_compile_cflags}")
-      endif()
-    endforeach()
-  else()
-    # Update target props, since all sources are C++.
-    set_property(TARGET ${name} APPEND_STRING PROPERTY
-      COMPILE_FLAGS "${target_compile_flags}")
-  endif()
-
-  set_property(TARGET ${name} APPEND PROPERTY COMPILE_DEFINITIONS ${LLVM_COMPILE_DEFINITIONS})
+  target_compile_options(${name} PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${LLVM_COMPILE_FLAGS}>)
+  target_compile_definitions(${name} PRIVATE ${LLVM_COMPILE_DEFINITIONS})
 endfunction()
 
 function(add_llvm_symbol_exports target_name export_file)
   if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
     set(native_export_file "${target_name}.exports")
     add_custom_command(OUTPUT ${native_export_file}
       COMMAND sed -e "s/^/_/" < ${export_file} > ${native_export_file}
       DEPENDS ${export_file}