Explain why we don't always use --gc-sections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220237 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index 284912c19c15c08d677c32129d252644128ccf32..127d5389d19d6a9ae0db611af96a835f7c788747 100644 (file)
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -143,10 +143,14 @@ endfunction(add_llvm_symbol_exports)
 function(add_dead_strip target_name)
   if(NOT LLVM_NO_DEAD_STRIP)
     if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
 function(add_dead_strip target_name)
   if(NOT LLVM_NO_DEAD_STRIP)
     if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")

+      # ld64's implementation of -dead_strip breaks tools that use plugins.

       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-dead_strip")
     elseif(NOT WIN32)
       # Object files are compiled with -ffunction-data-sections.
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-dead_strip")
     elseif(NOT WIN32)
       # Object files are compiled with -ffunction-data-sections.

+      # Versions of bfd ld < 2.23.1 have a bug in --gc-sections that breaks
+      # tools that use plugins. Always pass --gc-sections once we require
+      # a newer linker.

       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,--gc-sections")
     endif()
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,--gc-sections")
     endif()