[libc] add option to use SCUDO as the allocator

[michaelrj]

Summary

This patch adds LLVM_LIBC_INCLUDE_SCUDO as a flag. When enabled it
should link in the standalone version of SCUDO as the allocator for LLVM
libc.

[sivachandra]

As a follow up to this patch, we should add some kind of integration test to make sure that what is getting packaged is actually usable and works as expected.

libc/cmake/modules/LLVMLibCLibraryRules.cmake

82

Before we extract the objects from the dep, we should verify that the dep is an object library. Else, report a failure. One way could be to use the TYPE property to decide if the dep is an OBJECT_LIBRARY: https://cmake.org/cmake/help/v3.13/prop_tgt/TYPE.html

Most of this is already done in the code above from lines 65 to 78. So, we might just be able make use of the DEPENDS option with small adjustments.

[michaelrj]

added a comment explaining EXT_DEPS.

libc/cmake/modules/LLVMLibCLibraryRules.cmake

82

We can't check the properties of the dep since it may not be defined yet. The libc cmake scripts are evaluated before the compiler-rt scripts. This means we can't check the type of anything in EXT_DEPS, which means that combining EXT_DEPS and DEPENDS wouldn't work.

[cheng.w]

libc/CMakeLists.txt

74

What about set this option ON by default?

[sivachandra]

@cryptoad - This adds a build level dependency across projects. Do you see any problems which this arrangement? We will also start testing this arrangement via integration tests on the LLVM libc buildbot workers.

libc/CMakeLists.txt

74

Not sure if ON or OFF is the correct default value while LLVM libc is not complete. When it is complete enough, I think default ON makes more sense. That said, if you have a reason to make it ON do share here.

[cryptoad]

In D106502#2895464, @sivachandra wrote:

@cryptoad - This adds a build level dependency across projects. Do you see any problems which this arrangement? We will also start testing this arrangement via integration tests on the LLVM libc buildbot workers.

No problem with this, thank you!

[michaelrj]

libc/CMakeLists.txt

74

I like OFF as a default value, so that if someone is trying to build LLVM libc for the first time they don't get unexpected errors due to not including compiler-rt.

[cheng.w]

libc/CMakeLists.txt

74

Agree. I have no other reasons.

libc/CMakeLists.txt

 elseif(LLVM_LIBC_FULL_BUILD)
   message(WARNING "
     Linting for libc is currently disabled.
 
     This is not recommended, to enable set LLVM_LIBC_ENABLE_LINTING to ON
     (pass -DLLVM_LIBC_ENABLE_LINTING=ON to cmake).")
 endif()
 
+option(LLVM_LIBC_INCLUDE_SCUDO "Include the SCUDO standalone as the allocator for LLVM libc" OFF)
+if(LLVM_LIBC_INCLUDE_SCUDO)
+  if (NOT "compiler-rt" IN_LIST LLVM_ENABLE_PROJECTS)
+    message(FATAL_ERROR "SCUDO cannot be included without adding compiler-rt to LLVM_ENABLE_PROJECTS")
+  endif()
+endif()
+
 include(CMakeParseArguments)
 include(LLVMLibCRules)
 include(LLVMLibCCheckCpuFeatures)
 
 if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
   set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
 elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")
   set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")

libc/cmake/modules/LLVMLibCLibraryRules.cmake

if(${target_type} STREQUAL ${ENTRYPOINT_OBJ_TARGET_TYPE})
     return()
   endif()
 endfunction(collect_object_file_deps)
 
 # A rule to build a library from a collection of entrypoint objects.
 # Usage:
 #     add_entrypoint_library(
 #       DEPENDS <list of add_entrypoint_object targets>
+#       EXT_DEPS <list of external object targets, no type checking is done>
 #     )
 #
 # NOTE: If one wants an entrypoint to be availabe in a library, then they will
 # have to list the entrypoint target explicitly in the DEPENDS list. Implicit
 # entrypoint dependencies will not be added to the library.
 function(add_entrypoint_library target_name)
   cmake_parse_arguments(
     "ENTRYPOINT_LIBRARY"
     "" # No optional arguments
     "" # No single value arguments
-    "DEPENDS" # Multi-value arguments
+    "DEPENDS;EXT_DEPS" # Multi-value arguments
     ${ARGN}
   )
   if(NOT ENTRYPOINT_LIBRARY_DEPENDS)
     message(FATAL_ERROR "'add_entrypoint_library' target requires a DEPENDS list "
                         "of 'add_entrypoint_object' targets.")
   endif()
 
   get_fq_deps_list(fq_deps_list ${ENTRYPOINT_LIBRARY_DEPENDS})
   set(all_deps "")
   foreach(dep IN LISTS fq_deps_list)
     get_target_property(dep_type ${dep} "TARGET_TYPE")
     if(NOT (${dep_type} STREQUAL ${ENTRYPOINT_OBJ_TARGET_TYPE}))
       message(FATAL_ERROR "Dependency '${dep}' of 'add_entrypoint_collection' is "
                           "not an 'add_entrypoint_object' target.")
     endif()
     collect_object_file_deps(${dep} recursive_deps)
     list(APPEND all_deps ${recursive_deps})
   endforeach(dep)
   list(REMOVE_DUPLICATES all_deps)
   set(objects "")
   foreach(dep IN LISTS all_deps)
     list(APPEND objects $<TARGET_OBJECTS:${dep}>)
   endforeach(dep)
+
+  foreach(dep IN LISTS ENTRYPOINT_LIBRARY_EXT_DEPS)
+    list(APPEND objects $<TARGET_OBJECTS:${dep}>)
+  endforeach(dep)
+
   add_library(
     ${target_name}
     STATIC
     ${objects}
   )
   set_target_properties(${target_name}  PROPERTIES ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 endfunction(add_entrypoint_library)
 

libc/lib/CMakeLists.txt

+set(SCUDO_DEP "")
+
+if(LLVM_LIBC_INCLUDE_SCUDO)
+  list(APPEND SCUDO_DEP RTScudoStandalone.${LIBC_TARGET_ARCHITECTURE})
+endif()
+
 add_entrypoint_library(
   llvmlibc
   DEPENDS
   ${TARGET_LLVMLIBC_ENTRYPOINTS}
+  EXT_DEPS
+  ${SCUDO_DEP}
 )
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
   set(LIBC_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE})
 else()
   set(LIBC_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX})
 endif()