[libc] Implement FLAGS option for generating all combinations for targets.

Add FLAGS option for add_header_library, add_object_library,
add_entrypoint_object, and add_libc_unittest.

In general, a flag is a string provided for supported functions under the
multi-valued option `FLAGS`.  It should be one of the following forms:
  FLAG_NAME
  FLAG_NAME__NO
  FLAG_NAME__ONLY
A target will inherit all the flags of its upstream dependency.

When we create a target `TARGET_NAME` with a flag using (add_header_library,
add_object_library, ...), its behavior will depend on the flag form as follow:
- FLAG_NAME: The following 2 targets will be generated:
    `TARGET_NAME` that has `FLAG_NAME` in its `FLAGS` property.
    `TARGET_NAME.__NO_FLAG_NAME` that depends on `DEP.__NO_FLAG_NAME` if
       `TARGET_NAME` depends on `DEP` and `DEP` has `FLAG_NAME` in its `FLAGS`
       property.
- FLAG_NAME__ONLY: Only generate 1 target `TARGET_NAME` that has `FLAG_NAME`
    in its `FLAGS` property.
- FLAG_NAME__NO: Only generate 1 target `TARGET_NAME.__NO_FLAG_NAME` that
    depends on `DEP.__NO_FLAG_NAME` if `DEP` is in its DEPENDS list and `DEP`
    has `FLAG_NAME` in its `FLAGS` property.

To show all the targets generated, pass SHOW_INTERMEDIATE_OBJECTS=ON to cmake.
To show all the targets' dependency and flags, pass
`SHOW_INTERMEDIATE_OBJECTS=DEPS` to cmake.

To completely disable a flag FLAG_NAME expansion, set the variable
`SKIP_FLAG_EXPANSION_FLAG_NAME=TRUE`.

Reviewed By: michaelrj, sivachandra

Differential Revision: https://reviews.llvm.org/D125174

1 files changed, 258 insertions, 43 deletions

diff --git a/libc/cmake/modules/LLVMLibCObjectRules.cmake b/libc/cmake/modules/LLVMLibCObjectRules.cmake
index 8e2f489752a6..ae49e136615e 100644
--- a/libc/cmake/modules/LLVMLibCObjectRules.cmake
+++ b/libc/cmake/modules/LLVMLibCObjectRules.cmake
@@ -1,7 +1,7 @@
 set(OBJECT_LIBRARY_TARGET_TYPE "OBJECT_LIBRARY")
 
 function(_get_common_compile_options output_var)
-  set(compile_options ${LLVM_CXX_STD_default} ${LIBC_COMPILE_OPTIONS_DEFAULT} ${ARGN})
+  set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${ARGN})
   if(NOT ${LIBC_TARGET_OS} STREQUAL "windows")
     set(compile_options ${compile_options} -fpie -ffreestanding)
   endif()
@@ -26,12 +26,13 @@ endfunction()
 #       SRCS <list of source files>
 #       DEPENDS <list of dependencies>
 #       COMPILE_OPTIONS <optional list of special compile options for this target>
-function(add_object_library target_name)
+#       FLAGS <optional list of flags>
+function(create_object_library fq_target_name)
   cmake_parse_arguments(
     "ADD_OBJECT"
     "" # No optional arguments
     "CXX_STANDARD" # Single value arguments
-    "SRCS;HDRS;COMPILE_OPTIONS;DEPENDS" # Multivalue arguments
+    "SRCS;HDRS;COMPILE_OPTIONS;DEPENDS;FLAGS" # Multivalue arguments
     ${ARGN}
   )
 
@@ -39,7 +40,6 @@ function(add_object_library target_name)
     message(FATAL_ERROR "'add_object_library' rule requires SRCS to be specified.")
   endif()
 
-  get_fq_target_name(${target_name} fq_target_name)
   add_library(
     ${fq_target_name}
     EXCLUDE_FROM_ALL
@@ -58,24 +58,126 @@ function(add_object_library target_name)
   target_compile_options(${fq_target_name} PRIVATE ${compile_options})
 
   get_fq_deps_list(fq_deps_list ${ADD_OBJECT_DEPENDS})
+
+  if(SHOW_INTERMEDIATE_OBJECTS)
+    message(STATUS "Adding object library ${fq_target_name}")
+    if(${SHOW_INTERMEDIATE_OBJECTS} STREQUAL "DEPS")
+      foreach(dep IN LISTS ADD_OBJECT_DEPENDS)
+        message(STATUS "  ${fq_target_name} depends on ${dep}")
+      endforeach()
+    endif()
+  endif()
+
   if(fq_deps_list)
     add_dependencies(${fq_target_name} ${fq_deps_list})
   endif()
 
-  if(ADD_OBJECT_CXX_STANDARD)
-    set_target_properties(
-      ${fq_target_name}
-      PROPERTIES
-        CXX_STANDARD ${ADD_OBJECT_CXX_STANDARD}
-    )
+  if(NOT ADD_OBJECT_CXX_STANDARD)
+    set(ADD_OBJECT_CXX_STANDARD ${CMAKE_CXX_STANDARD})
   endif()
-
+  
   set_target_properties(
     ${fq_target_name}
     PROPERTIES
-      "TARGET_TYPE" ${OBJECT_LIBRARY_TARGET_TYPE}
-      "OBJECT_FILES" "$<TARGET_OBJECTS:${fq_target_name}>"
-      "DEPS" "${fq_deps_list}"
+      TARGET_TYPE ${OBJECT_LIBRARY_TARGET_TYPE}
+      OBJECT_FILES "$<TARGET_OBJECTS:${fq_target_name}>"
+      CXX_STANDARD ${ADD_OBJECT_CXX_STANDARD}
+      DEPS "${fq_deps_list}"
+      FLAGS "${ADD_OBJECT_FLAGS}"
+  )
+endfunction(create_object_library)
+
+# Internal function, used by `add_object_library`.
+function(expand_flags_for_object_library target_name flags)
+  cmake_parse_arguments(
+    "EXPAND_FLAGS"
+    "IGNORE_MARKER" # Optional arguments
+    "" # Single-value arguments
+    "DEPENDS;FLAGS" # Multi-value arguments
+    ${ARGN}
+  )
+
+  list(LENGTH flags nflags)
+  if(NOT ${nflags})
+    create_object_library(
+      ${target_name}
+      DEPENDS ${EXPAND_FLAGS_DEPENDS}
+      FLAGS ${EXPAND_FLAGS_FLAGS}
+      ${EXPAND_FLAGS_UNPARSED_ARGUMENTS}
+    )
+    return()
+  endif()
+
+  list(POP_FRONT flags flag)
+  extract_flag_modifier(${flag} real_flag modifier)
+
+  if(NOT "${modifier}" STREQUAL "NO")
+    expand_flags_for_object_library(
+      ${target_name}
+      "${flags}"
+      DEPENDS "${EXPAND_FLAGS_DEPENDS}" IGNORE_MARKER
+      FLAGS "${EXPAND_FLAGS_FLAGS}" IGNORE_MARKER
+      "${EXPAND_FLAGS_UNPARSED_ARGUMENTS}"
+    )
+  endif()
+
+  if("${real_flag}" STREQUAL "" OR "${modifier}" STREQUAL "ONLY")
+    return()
+  endif()
+
+  set(NEW_FLAGS ${EXPAND_FLAGS_FLAGS})
+  list(REMOVE_ITEM NEW_FLAGS ${flag})
+  get_fq_dep_list_without_flag(NEW_DEPS ${real_flag} ${EXPAND_FLAGS_DEPENDS})
+
+  # Only target with `flag` has `.__NO_flag` target, `flag__NO` and
+  # `flag__ONLY` do not.
+  if(NOT "${modifier}")
+    set(TARGET_NAME "${target_name}.__NO_${flag}")
+  else()
+    set(TARGET_NAME "${target_name}")
+  endif()
+
+  expand_flags_for_object_library(
+    ${TARGET_NAME}
+    "${flags}"
+    DEPENDS "${NEW_DEPS}" IGNORE_MARKER
+    FLAGS "${NEW_FLAGS}" IGNORE_MARKER
+    "${EXPAND_FLAGS_UNPARSED_ARGUMENTS}"
+  )
+endfunction(expand_flags_for_object_library)
+
+function(add_object_library target_name)
+  cmake_parse_arguments(
+    "ADD_TO_EXPAND"
+    "" # Optional arguments
+    "" # Single value arguments
+    "DEPENDS;FLAGS" # Multi-value arguments
+    ${ARGN}
+  )
+
+  get_fq_target_name(${target_name} fq_target_name)
+
+  if(ADD_TO_EXPAND_DEPENDS AND ("${SHOW_INTERMEDIATE_OBJECTS}" STREQUAL "DEPS"))
+    message(STATUS "Gathering FLAGS from dependencies for ${fq_target_name}")
+  endif()
+
+  get_fq_deps_list(fq_deps_list ${ADD_TO_EXPAND_DEPENDS})
+  get_flags_from_dep_list(deps_flag_list ${fq_deps_list})
+
+  list(APPEND ADD_TO_EXPAND_FLAGS ${deps_flag_list})
+  remove_duplicated_flags("${ADD_TO_EXPAND_FLAGS}" flags)
+  list(SORT flags)
+
+  if(SHOW_INTERMEDIATE_OBJECTS AND flags)
+    message(STATUS "Object library ${fq_target_name} has FLAGS: ${flags}")
+  endif()
+
+  expand_flags_for_object_library(
+    ${fq_target_name}
+    "${flags}"
+    DEPENDS "${fq_deps_list}" IGNORE_MARKER
+    FLAGS "${flags}" IGNORE_MARKER
+    ${ADD_TO_EXPAND_UNPARSED_ARGUMENTS}
   )
 endfunction(add_object_library)
 
@@ -92,29 +194,24 @@ set(ENTRYPOINT_OBJ_TARGET_TYPE "ENTRYPOINT_OBJ")
 #       DEPENDS <list of dependencies>
 #       COMPILE_OPTIONS <optional list of special compile options for this target>
 #       SPECIAL_OBJECTS <optional list of special object targets added by the rule `add_object`>
+#       FLAGS <optional list of flags>
 #     )
-function(add_entrypoint_object target_name)
+function(create_entrypoint_object fq_target_name)
   cmake_parse_arguments(
     "ADD_ENTRYPOINT_OBJ"
     "ALIAS;REDIRECTED" # Optional argument
     "NAME;CXX_STANDARD" # Single value arguments
-    "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS"  # Multi value arguments
+    "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS;FLAGS"  # Multi value arguments
     ${ARGN}
   )
 
-  get_fq_target_name(${target_name} fq_target_name)
-  set(entrypoint_name ${target_name})
-  if(ADD_ENTRYPOINT_OBJ_NAME)
-    set(entrypoint_name ${ADD_ENTRYPOINT_OBJ_NAME})
-  endif()
-
-  list(FIND TARGET_ENTRYPOINT_NAME_LIST ${entrypoint_name} entrypoint_name_index)
+  list(FIND TARGET_ENTRYPOINT_NAME_LIST ${ADD_ENTRYPOINT_OBJ_NAME} entrypoint_name_index)
   if(${entrypoint_name_index} EQUAL -1)
     add_custom_target(${fq_target_name})
     set_target_properties(
       ${fq_target_name}
       PROPERTIES
-        "ENTRYPOINT_NAME" ${entrypoint_name}
+        "ENTRYPOINT_NAME" ${ADD_ENTRYPOINT_OBJ_NAME}
         "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
         "OBJECT_FILE" ""
         "OBJECT_FILE_RAW" ""
@@ -134,6 +231,12 @@ function(add_entrypoint_object target_name)
     endif()
     list(GET ADD_ENTRYPOINT_OBJ_DEPENDS 0 dep_target)
     get_fq_dep_name(fq_dep_name ${dep_target})
+
+    if(SHOW_INTERMEDIATE_OBJECTS)
+      message(STATUS "Adding entrypoint object ${fq_target_name} as an alias of"
+              " ${fq_dep_name}")
+    endif()
+
     if(NOT TARGET ${fq_dep_name})
       message(WARNING "Aliasee ${fq_dep_name} for entrypoint alias ${target_name} missing; "
                       "Target ${target_name} will be ignored.")
@@ -152,12 +255,13 @@ function(add_entrypoint_object target_name)
     set_target_properties(
       ${fq_target_name}
       PROPERTIES
-        "ENTRYPOINT_NAME" ${entrypoint_name}
-        "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
-        "IS_ALIAS" "YES"
-        "OBJECT_FILE" ""
-        "OBJECT_FILE_RAW" ""
-        "DEPS" "${fq_dep_name}"
+        ENTRYPOINT_NAME ${ADD_ENTRYPOINT_OBJ_NAME}
+        TARGET_TYPE ${ENTRYPOINT_OBJ_TARGET_TYPE}
+        IS_ALIAS "YES"
+        OBJECT_FILE ""
+        OBJECT_FILE_RAW ""
+        DEPS "${fq_dep_name}"
+        FLAGS "${ADD_ENTRYPOINT_OBJ_FLAGS}"
     )
     return()
   endif()
@@ -168,6 +272,9 @@ function(add_entrypoint_object target_name)
   if(NOT ADD_ENTRYPOINT_OBJ_HDRS)
     message(FATAL_ERROR "`add_entrypoint_object` rule requires HDRS to be specified.")
   endif()
+  if(NOT ADD_ENTRYPOINT_OBJ_CXX_STANDARD)
+    set(ADD_ENTRYPOINT_OBJ_CXX_STANDARD ${CMAKE_CXX_STANDARD})
+  endif()
 
   _get_common_compile_options(common_compile_options ${ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS})
   set(internal_target_name ${fq_target_name}.__internal__)
@@ -175,6 +282,15 @@ function(add_entrypoint_object target_name)
   get_fq_deps_list(fq_deps_list ${ADD_ENTRYPOINT_OBJ_DEPENDS})
   set(full_deps_list ${fq_deps_list} libc.src.__support.common)
 
+  if(SHOW_INTERMEDIATE_OBJECTS)
+    message(STATUS "Adding entrypoint object ${fq_target_name}")
+    if(${SHOW_INTERMEDIATE_OBJECTS} STREQUAL "DEPS")
+      foreach(dep IN LISTS ADD_OBJECT_DEPENDS)
+        message(STATUS "  ${fq_target_name} depends on ${dep}")
+      endforeach()
+    endif()
+  endif()
+
   add_library(
     ${internal_target_name}
     # TODO: We don't need an object library for internal consumption.
@@ -187,6 +303,12 @@ function(add_entrypoint_object target_name)
   target_compile_options(${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})
+  set_target_properties(
+    ${internal_target_name}
+    PROPERTIES
+      CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
+      FLAGS "${ADD_ENTRYPOINT_OBJ_FLAGS}"
+  )
 
   add_library(
     ${fq_target_name}
@@ -201,24 +323,18 @@ function(add_entrypoint_object target_name)
   target_include_directories(${fq_target_name} PRIVATE ${include_dirs})
   add_dependencies(${fq_target_name} ${full_deps_list})
 
-  if(ADD_ENTRYPOINT_OBJ_CXX_STANDARD)
-    set_target_properties(
-      ${fq_target_name} ${internal_target_name}
-      PROPERTIES
-        CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
-    )
-  endif()
-
   set_target_properties(
     ${fq_target_name}
     PROPERTIES
-      "ENTRYPOINT_NAME" ${entrypoint_name}
-      "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
-      "OBJECT_FILE" $<TARGET_OBJECTS:${fq_target_name}>
+      ENTRYPOINT_NAME ${ADD_ENTRYPOINT_OBJ_NAME}
+      TARGET_TYPE ${ENTRYPOINT_OBJ_TARGET_TYPE}
+      OBJECT_FILE "$<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" "${fq_deps_list}"
+      OBJECT_FILE_RAW "$<TARGET_OBJECTS:${internal_target_name}>"
+      CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
+      DEPS "${fq_deps_list}"
+      FLAGS "${ADD_ENTRYPOINT_OBJ_FLAGS}"
   )
 
   if(LLVM_LIBC_ENABLE_LINTING)
@@ -280,6 +396,105 @@ function(add_entrypoint_object target_name)
     )
   endif()
 
+endfunction(create_entrypoint_object)
+
+# Internal function, used by `add_entrypoint_object`.
+function(expand_flags_for_entrypoint_object target_name flags)
+  cmake_parse_arguments(
+    "EXPAND_FLAGS"
+    "IGNORE_MARKER" # Optional arguments
+    "" # Single-value arguments
+    "DEPENDS;FLAGS" # Multi-value arguments
+    ${ARGN}
+  )
+
+  list(LENGTH flags nflags)
+  if(NOT ${nflags})
+    create_entrypoint_object(
+      ${target_name}
+      DEPENDS ${EXPAND_FLAGS_DEPENDS}
+      FLAGS ${EXPAND_FLAGS_FLAGS}
+      ${EXPAND_FLAGS_UNPARSED_ARGUMENTS}
+    )
+    return()
+  endif()
+
+  list(POP_FRONT flags flag)
+  extract_flag_modifier(${flag} real_flag modifier)
+
+  if(NOT "${modifier}" STREQUAL "NO")
+    expand_flags_for_entrypoint_object(
+      ${target_name}
+      "${flags}"
+      DEPENDS "${EXPAND_FLAGS_DEPENDS}" IGNORE_MARKER
+      FLAGS "${EXPAND_FLAGS_FLAGS}" IGNORE_MARKER
+      "${EXPAND_FLAGS_UNPARSED_ARGUMENTS}"
+    )
+  endif()
+
+  if("${real_flag}" STREQUAL "" OR "${modifier}" STREQUAL "ONLY")
+    return()
+  endif()
+
+  set(NEW_FLAGS ${EXPAND_FLAGS_FLAGS})
+  list(REMOVE_ITEM NEW_FLAGS ${flag})
+  get_fq_dep_list_without_flag(NEW_DEPS ${real_flag} ${EXPAND_FLAGS_DEPENDS})
+
+  # Only target with `flag` has `.__NO_flag` target, `flag__NO` and
+  # `flag__ONLY` do not.
+  if(NOT "${modifier}")
+    set(TARGET_NAME "${target_name}.__NO_${flag}")
+  else()
+    set(TARGET_NAME "${target_name}")
+  endif()
+
+  expand_flags_for_entrypoint_object(
+    ${TARGET_NAME}
+    "${flags}"
+    DEPENDS "${NEW_DEPS}" IGNORE_MARKER
+    FLAGS "${NEW_FLAGS}" IGNORE_MARKER
+    "${EXPAND_FLAGS_UNPARSED_ARGUMENTS}"
+  )
+endfunction(expand_flags_for_entrypoint_object)
+
+function(add_entrypoint_object target_name)
+  cmake_parse_arguments(
+    "ADD_TO_EXPAND"
+    "" # Optional arguments
+    "NAME" # Single value arguments
+    "DEPENDS;FLAGS" # Multi-value arguments
+    ${ARGN}
+  )
+
+  get_fq_target_name(${target_name} fq_target_name)
+
+  if(ADD_TO_EXPAND_DEPENDS AND ("${SHOW_INTERMEDIATE_OBJECTS}" STREQUAL "DEPS"))
+    message(STATUS "Gathering FLAGS from dependencies for ${fq_target_name}")
+  endif()
+
+  get_fq_deps_list(fq_deps_list ${ADD_TO_EXPAND_DEPENDS})
+  get_flags_from_dep_list(deps_flag_list ${fq_deps_list})
+
+  list(APPEND ADD_TO_EXPAND_FLAGS ${deps_flag_list})
+  remove_duplicated_flags("${ADD_TO_EXPAND_FLAGS}" flags)
+  list(SORT flags)
+
+  if(SHOW_INTERMEDIATE_OBJECTS AND flags)
+    message(STATUS "Object library ${fq_target_name} has FLAGS: ${flags}")
+  endif()
+
+  if(NOT ADD_TO_EXPAND_NAME)
+    set(ADD_TO_EXPAND_NAME ${target_name})
+  endif()
+
+  expand_flags_for_entrypoint_object(
+    ${fq_target_name}
+    "${flags}"
+    NAME ${ADD_TO_EXPAND_NAME} IGNORE_MARKER
+    DEPENDS "${fq_deps_list}" IGNORE_MARKER
+    FLAGS "${flags}" IGNORE_MARKER
+    ${ADD_TO_EXPAND_UNPARSED_ARGUMENTS}
+  )
 endfunction(add_entrypoint_object)
 
 set(ENTRYPOINT_EXT_TARGET_TYPE "ENTRYPOINT_EXT")