[CMake] Add option LLVM_EXTERNALIZE_DEBUGINFO

[beanz]

Summary

This adds support for generating dSYM files and stripping debug info from executables and dylibs. It also supports passing -object_path_lto to the linker to generate dSYMs for LTO builds.

[beanz]

For LTO builds, dsymutil doesn't need to run against the intermediate object, we just need to make sure it sticks around.

[friss]

From what I understand this looks fine, but I fear that I'm not CMake-savvy enough to approve it.

cmake/modules/AddLLVM.cmake

1183 ↗

(On Diff #41660)

I would make that ${name}-lto.o just to make it clear what it is if someone looks at the directory and is concerned about that huge object file.

[beanz]

Updated object name to ${name}-lto.o as per Fred's suggestion.

[beanz]

Updates based on feedback from bogner.

llvm/trunk/CMakeLists.txt

if( NOT CMAKE_SYSTEM_NAME MATCHES "Windows" AND NOT CMAKE_SYSTEM_NAME MATCHES "Linux" )
     message(FATAL_ERROR
       "Intel JIT API support is available on Linux and Windows only.")
   endif()
 endif( LLVM_USE_INTEL_JITEVENTS )
 
 option(LLVM_USE_OPROFILE
   "Use opagent JIT interface to inform OProfile about JIT code" OFF)
 
+option(LLVM_EXTERNALIZE_DEBUGINFO
+  "Generate dSYM files and strip executables and libraries (Darwin Only)" OFF)
+
 # If enabled, verify we are on a platform that supports oprofile.
 if( LLVM_USE_OPROFILE )
   if( NOT CMAKE_SYSTEM_NAME MATCHES "Linux" )
     message(FATAL_ERROR "OProfile support is available on Linux only.")
   endif( NOT CMAKE_SYSTEM_NAME MATCHES "Linux" )
 endif( LLVM_USE_OPROFILE )
 
 set(LLVM_USE_SANITIZER "" CACHE STRING

llvm/trunk/cmake/modules/AddLLVM.cmake

function(llvm_add_library name)
   if(LLVM_COMMON_DEPENDS)
     add_dependencies(${name} ${LLVM_COMMON_DEPENDS})
     # Add dependencies also to objlibs.
     # CMake issue 14747 --  add_dependencies() might be ignored to objlib's user.
     foreach(objlib ${objlibs})
       add_dependencies(${objlib} ${LLVM_COMMON_DEPENDS})
     endforeach()
   endif()
+
+  if(ARG_SHARED OR ARG_MODULE)
+    llvm_externalize_debuginfo(${name})
+  endif()
 endfunction()
 
 macro(add_llvm_library name)
   cmake_parse_arguments(ARG
     "SHARED"
     ""
     ""
     ${ARGN})
macro(add_llvm_executable name)
   endif()
 
   set(EXCLUDE_FROM_ALL OFF)
   set_output_directory(${name} BINARY_DIR ${LLVM_RUNTIME_OUTPUT_INTDIR} LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
   llvm_config( ${name} ${USE_SHARED} ${LLVM_LINK_COMPONENTS} )
   if( LLVM_COMMON_DEPENDS )
     add_dependencies( ${name} ${LLVM_COMMON_DEPENDS} )
   endif( LLVM_COMMON_DEPENDS )
+
+  llvm_externalize_debuginfo(${name})
 endmacro(add_llvm_executable name)
 
 function(export_executable_symbols target)
   if (NOT MSVC) # MSVC's linker doesn't support exporting all symbols.
     set_target_properties(${target} PROPERTIES ENABLE_EXPORTS 1)
     if (APPLE)
       set_target_properties(${target} PROPERTIES
         LINK_FLAGS "-rdynamic")
else()
     # tool and its parent tool are in LLVM_TOOLCHAIN_TOOLS
     if (LLVM_IS_${name}_TOOLCHAIN_TOOL GREATER -1 OR NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
       if( LLVM_BUILD_TOOLS )
         llvm_install_symlink(${name} ${dest})
       endif()
     endif()
   endif()
 endfunction()
+
+function(llvm_externalize_debuginfo name)
+  if(NOT LLVM_EXTERNALIZE_DEBUGINFO)
+    return()
+  endif()
+
+  if(APPLE)
+    if(CMAKE_CXX_FLAGS MATCHES "-flto"
+      OR CMAKE_CXX_FLAGS_${uppercase_CMAKE_BUILD_TYPE} MATCHES "-flto")
+
+      set(lto_object ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/${name}-lto.o)
+      set_target_properties(${name} PROPERTIES
+        LINK_FLAGS "-Wl,-object_path_lto -Wl,${lto_object}")
+    endif()
+    add_custom_command(TARGET ${name} POST_BUILD
+      COMMAND xcrun dsymutil $<TARGET_FILE:${name}>
+      COMMAND xcrun strip -Sl $<TARGET_FILE:${name}>)
+  else()
+    message(FATAL_ERROR "LLVM_EXTERNALIZE_DEBUGINFO isn't implemented for non-darwin platforms!")
+  endif()
+endfunction()