[llvm] [cmake] Skip driver-related code unless LLVM_TOOL_LLVM_DRIVER_BUILD

[mgorny]

Summary

Disable the code responsible for preparing object libraries
for the driver and filling LLVM_DRIVER_* properties
if LLVM_TOOL_LLVM_DRIVER_BUILD is disabled. These properties are
consumed only by tools/llvm-driver, and so they are not used at all
if LLVM_TOOL_LLVM_DRIVER_BUILD is not enabled. At the same time,
the related code breaks standalone clang builds against LLVM built
with LLVM_LINK_LLVM_DYLIB.

[mgorny]

@abrachet, I've did a quick test locally using in-tree build with LLVM_TOOL_LLVM_DRIVER_BUILD enabled but could you double-check that everything works on top of this patch, please?

[MaskRay]

I don't understand what happened, but LG

[phosek]

LGTM

[abrachet]

In D130158#3665269, @mgorny wrote:

@abrachet, I've did a quick test locally using in-tree build with LLVM_TOOL_LLVM_DRIVER_BUILD enabled but could you double-check that everything works on top of this patch, please?

Works with both LLVM_TOOL_LLVM_DRIVER_BUILD={On,Off}. Thanks a lot and sorry for the hassle.

llvm/cmake/modules/AddLLVM.cmake

 macro(generate_llvm_objects name)
   cmake_parse_arguments(ARG "GENERATE_DRIVER" "" "DEPENDS" ${ARGN})
 
   llvm_process_sources( ALL_FILES ${ARG_UNPARSED_ARGUMENTS} )
 
   list(APPEND LLVM_COMMON_DEPENDS ${ARG_DEPENDS})
 
   # Generate objlib
-  if(LLVM_ENABLE_OBJLIB OR ARG_GENERATE_DRIVER)
+  if(LLVM_ENABLE_OBJLIB OR (ARG_GENERATE_DRIVER AND LLVM_TOOL_LLVM_DRIVER_BUILD))
     # Generate an obj library for both targets.
     set(obj_name "obj.${name}")
     add_library(${obj_name} OBJECT EXCLUDE_FROM_ALL
       ${ALL_FILES}
       )
     llvm_update_compile_flags(${obj_name})
     set(ALL_FILES "$<TARGET_OBJECTS:${obj_name}>")
     if(ARG_DEPENDS)
foreach(path ${CMAKE_MODULE_PATH})
           ${path}/llvm-driver-template.cpp.in
           ${CMAKE_CURRENT_BINARY_DIR}/${name}-driver.cpp)
         break()
       endif()
     endforeach()
 
     list(APPEND ALL_FILES ${CMAKE_CURRENT_BINARY_DIR}/${name}-driver.cpp)
 
+    if (LLVM_TOOL_LLVM_DRIVER_BUILD)
       set_property(GLOBAL APPEND PROPERTY LLVM_DRIVER_COMPONENTS ${LLVM_LINK_COMPONENTS})
       set_property(GLOBAL APPEND PROPERTY LLVM_DRIVER_DEPS ${ARG_DEPENDS} ${LLVM_COMMON_DEPENDS})
       set_property(GLOBAL APPEND PROPERTY LLVM_DRIVER_OBJLIBS "${obj_name}")
-    
       set_property(GLOBAL APPEND PROPERTY LLVM_DRIVER_TOOLS ${name})
       target_link_libraries(${obj_name} ${LLVM_PTHREAD_LIB})
       llvm_config(${obj_name} ${USE_SHARED} ${LLVM_LINK_COMPONENTS} )
     endif()
+  endif()
 endmacro()
 
 macro(add_llvm_executable name)
   cmake_parse_arguments(ARG
     "DISABLE_LLVM_LINK_LLVM_DYLIB;IGNORE_EXTERNALIZE_DEBUGINFO;NO_INSTALL_RPATH;SUPPORT_PLUGINS"
     "ENTITLEMENTS;BUNDLE_PATH"
     ""
     ${ARGN})