[libc] Build two different static archives libc.a and libm.a under full build.

[sivachandra]

Summary

We currently put everything in one single archive libc.a which breaks in
certain situations where the compiler drivers expect libm.a also. With
this change, we separate out libc.a and libm.a functions as is done
conventionally and put them in two different static archives.

One will now have to build two targets, libc and libm which produce
libc.a and libm.a respectively. Under default build, one still builds only
one target named libc which produces libllvmlibc.a.

[jhuber6]

libc/lib/CMakeLists.txt

6

Does this omit libm if there are no entrypoints for it enabled? Right now I haven't begun working on any libm related stuff.

[sivachandra]

Skip adding an archive target if the archive's entrypoint list is not present.

[sivachandra]

libc/lib/CMakeLists.txt

6

That's a good point. I have updated now to skip adding an archive target if the correspond entrypoint list is missing.

[jhuber6]

libc/lib/CMakeLists.txt

1–3

Is this necessary? Won't CMake just create an empty one if it doesn't exist?

[sivachandra]

libc/lib/CMakeLists.txt

1–3

Yes, in most contexts that is correct. But, I just do it as a practice because we cannot really control var-name leakage from the parent. As in, if the parent uses the same names for its local logic, they will come here already initialized to some value. As a policy though, we name vars having global semantics in UPPER_SNAKE_CASE.

[jhuber6]

LG

libc/CMakeLists.txt

if(${last_dot_loc} EQUAL -1)
     message(FATAL "Invalid entrypoint target name ${entrypoint}; Expected a '.' "
                   "(dot) in the name.")
   endif()
   math(EXPR name_loc "${last_dot_loc} + 1")
   string(SUBSTRING ${entrypoint} ${name_loc} -1 entrypoint_name)
   list(APPEND TARGET_ENTRYPOINT_NAME_LIST ${entrypoint_name})
 endforeach()
 
-set(LIBC_TARGET)
-set(LIBC_COMPONENT)
 set(LIBC_INSTALL_DEPENDS)
-set(LIBC_INSTALL_TARGET)
 if(LLVM_LIBC_FULL_BUILD)
   set(LIBC_INSTALL_DEPENDS "install-libc-static-archives;install-libc-headers")
   if(NOT LIBC_TARGET_OS_IS_BAREMETAL)
     # For now we will disable libc-startup installation for baremetal. The
     # correct way to do it would be to make a hookable startup for baremetal
     # and install it as part of the libc installation.
     list(APPEND LIBC_INSTALL_DEPENDS "libc-startup")
   endif()
-  if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-    set(LIBC_ARCHIVE_NAME cgpu)
-  else()
-    set(LIBC_ARCHIVE_NAME c)
-  endif()
 else()
   set(LIBC_INSTALL_DEPENDS install-libc-static-archives)
-  set(LIBC_ARCHIVE_NAME llvmlibc)
 endif()
 
 add_subdirectory(include)
 add_subdirectory(config)
 add_subdirectory(src)
 add_subdirectory(utils)
 
 if(LLVM_LIBC_FULL_BUILD)

libc/lib/CMakeLists.txt

+set(libc_archive_targets "")
+set(libc_archive_names "")
+set(libc_archive_entrypoint_lists "")
+if(LLVM_LIBC_FULL_BUILD)
+  if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
+    list(APPEND libc_archive_names cgpu mgpu)
+  else()
+    list(APPEND libc_archive_names c m)
+  endif()
+  list(APPEND libc_archive_targets libc libm)
+  list(APPEND libc_archive_entrypoint_lists
+       TARGET_LIBC_ENTRYPOINTS TARGET_LIBM_ENTRYPOINTS)
+else()
+  list(APPEND libc_archive_names llvmlibc)
+  list(APPEND libc_archive_targets libc)
+  list(APPEND libc_archive_entrypoint_lists TARGET_LLVMLIBC_ENTRYPOINTS)
+endif()
+
+set(added_archive_targets "")
+foreach(archive IN ZIP_LISTS
+        libc_archive_names libc_archive_targets libc_archive_entrypoint_lists)
+  if(NOT ${archive_2})
+    # If an entrypoint list is missing, then skip adding targets for it.
+    continue()
+  endif()
   add_entrypoint_library(
-  libc
+    ${archive_1}
     DEPENDS
-  ${TARGET_LLVMLIBC_ENTRYPOINTS}
+      ${${archive_2}}
   )
   set_target_properties(
-  libc
+    ${archive_1}
     PROPERTIES
-    ARCHIVE_OUTPUT_NAME ${LIBC_ARCHIVE_NAME}
+      ARCHIVE_OUTPUT_NAME ${archive_0}
   )
+  list(APPEND added_archive_targets ${archive_1})
+endforeach()
 
 if(LIBC_TARGET_TRIPLE)
   set(LIBC_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBC_TARGET_TRIPLE})
 elseif(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT LIBC_GPU_BUILD)
   set(LIBC_INSTALL_LIBRARY_DIR
       lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE})
 else()
   set(LIBC_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX})
 endif()
 
 install(
-  TARGETS libc
+  TARGETS ${added_archive_targets}
   ARCHIVE DESTINATION ${LIBC_INSTALL_LIBRARY_DIR}
   COMPONENT libc-static-archives
 )
 
 add_llvm_install_targets(
   install-libc-static-archives
-  DEPENDS libc
+  DEPENDS ${added_archive_targets}
   COMPONENT libc-static-archives
 )

libc/startup/linux/CMakeLists.txt

 add_custom_target(libc-startup)
 set(startup_components crt1 crti crtn)
 foreach(target IN LISTS startup_components)
   set(fq_target_name libc.startup.linux.${target})
   add_dependencies(libc-startup ${fq_target_name})
   get_target_property(startup_object ${fq_target_name} STARTUP_OBJECT)
   install(FILES ${startup_object}
           DESTINATION ${CMAKE_INSTALL_LIBDIR}
-          COMPONENT ${LIBC_COMPONENT})
+          COMPONENT libc)
 endforeach()