[libc] Switch to use a macro which does not insert a section for every libc function.

Summary:
The new macro also inserts the C alias for the C++ implementations
without needing an objcopy based post processing step. The CMake
rules have been updated to reflect this. More CMake cleanup can be
taken up in future rounds and appropriate TODOs have been added for them.

Reviewers: mcgrathr, sivachandra

Subscribers:

1 files changed, 26 insertions, 58 deletions

diff --git a/libc/cmake/modules/LLVMLibCObjectRules.cmake b/libc/cmake/modules/LLVMLibCObjectRules.cmake
index 32900d825531..93f772d93bb2 100644
--- a/libc/cmake/modules/LLVMLibCObjectRules.cmake
+++ b/libc/cmake/modules/LLVMLibCObjectRules.cmake
@@ -147,10 +147,26 @@ function(add_entrypoint_object target_name)
     message(FATAL_ERROR "`add_entrypoint_object` rule requires HDRS to be specified.")
   endif()
 
-  set(objects_target_name "${fq_target_name}_objects")
+  set(common_compile_options -fpie ${LLVM_CXX_STD_default} -ffreestanding ${ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS})
+  set(internal_target_name ${fq_target_name}.__internal__)
+  set(include_dirs ${LIBC_BUILD_DIR}/include ${LIBC_SOURCE_DIR} ${LIBC_BUILD_DIR})
+  get_fq_deps_list(fq_deps_list ${ADD_ENTRYPOINT_OBJ_DEPENDS})
+  set(full_deps_list ${fq_deps_list} libc.src.__support.common)
+
+  add_library(
+    ${internal_target_name}
+    # TODO: We don't need an object library for internal consumption.
+    # A future change should switch this to a normal static library.
+    OBJECT
+    ${ADD_ENTRYPOINT_OBJ_SRCS}
+    ${ADD_ENTRYPOINT_OBJ_HDRS}
+  )
+  target_compile_options(${internal_target_name} BEFORE PRIVATE ${common_compile_options})
+  target_include_directories(${internal_target_name} PRIVATE ${include_dirs})
+  add_dependencies(${internal_target_name} ${full_deps_list})
 
   add_library(
-    ${objects_target_name}
+    ${fq_target_name}
     # We want an object library as the objects will eventually get packaged into
     # an archive (like libc.a).
     OBJECT
@@ -158,68 +174,20 @@ function(add_entrypoint_object target_name)
     ${ADD_ENTRYPOINT_OBJ_HDRS}
   )
   target_compile_options(
-    ${objects_target_name}
-    BEFORE
-    PRIVATE
-      -fpie ${LLVM_CXX_STD_default} -ffreestanding
-  )
-  target_include_directories(
-    ${objects_target_name}
-    PRIVATE
-      ${LIBC_BUILD_DIR}/include
-      ${LIBC_SOURCE_DIR}
-      ${LIBC_BUILD_DIR}
+      ${fq_target_name} BEFORE PRIVATE ${common_compile_options} -DLLVM_LIBC_PUBLIC_PACKAGING
   )
-  get_fq_deps_list(fq_deps_list ${ADD_ENTRYPOINT_OBJ_DEPENDS})
-  add_dependencies(
-    ${objects_target_name}
-    libc.src.__support.common
-    ${fq_deps_list}
-  )
-
-  if(ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS)
-    target_compile_options(
-      ${objects_target_name}
-      PRIVATE ${ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS}
-    )
-  endif()
+  target_include_directories(${fq_target_name} PRIVATE ${include_dirs})
+  add_dependencies(${fq_target_name} ${full_deps_list})
 
-  set(object_file_raw "${CMAKE_CURRENT_BINARY_DIR}/${target_name}_raw.o")
-  set(object_file "${CMAKE_CURRENT_BINARY_DIR}/${target_name}.o")
-
-  set(input_objects $<TARGET_OBJECTS:${objects_target_name}>)
-  add_custom_command(
-    OUTPUT ${object_file_raw}
-    DEPENDS ${input_objects}
-    COMMAND ${CMAKE_LINKER} -r ${input_objects} -o ${object_file_raw}
-  )
-
-  set(alias_attributes "0,function,global")
-  if(ADD_ENTRYPOINT_OBJ_REDIRECTED)
-    set(alias_attributes "${alias_attributes},hidden")
-  endif()
-
-  add_custom_command(
-    OUTPUT ${object_file}
-    # We llvm-objcopy here as GNU-binutils objcopy does not support the 'hidden' flag.
-    DEPENDS ${object_file_raw} ${llvm-objcopy}
-    COMMAND $<TARGET_FILE:llvm-objcopy> --add-symbol
-            "${entrypoint_name}=.llvm.libc.entrypoint.${entrypoint_name}:${alias_attributes}"
-            ${object_file_raw} ${object_file}
-  )
-
-  add_custom_target(
-    ${fq_target_name}
-    ALL
-    DEPENDS ${object_file}
-  )
   set_target_properties(
     ${fq_target_name}
     PROPERTIES
       "ENTRYPOINT_NAME" ${entrypoint_name}
       "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
-      "OBJECT_FILE" "${object_file}"
-      "OBJECT_FILE_RAW" "${object_file_raw}"
+      "OBJECT_FILE" $<TARGET_OBJECTS:${fq_target_name}>
+      # TODO: We don't need to list internal object files if the internal
+      # target is a normal static library.
+      "OBJECT_FILE_RAW" $<TARGET_OBJECTS:${internal_target_name}>
       "DEPS" "${fq_deps_list}"
   )
 
@@ -273,7 +241,7 @@ function(add_entrypoint_object target_name)
       # crossplatform touch.
       COMMAND "${CMAKE_COMMAND}" -E touch ${lint_timestamp}
       COMMENT "Linting... ${target_name}"
-      DEPENDS clang-tidy ${objects_target_name} ${ADD_ENTRYPOINT_OBJ_SRCS}
+      DEPENDS clang-tidy ${internal_target_name} ${ADD_ENTRYPOINT_OBJ_SRCS}
       WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
     )