[CMake] Teach build system to build/test compiler-rt with a just-built Clang

With this change, one may set LLVM_BUILD_EXTERNAL_COMPILER_RT option
to build compiler-rt libraries with just-built Clang.

  make compiler-rt
in the build tree will build all compiler-rt libraries with just-built Clang
and copy them to the proper location in the Clang resource directory.

  make check-compiler-rt
will run the compiler-rt test suite using just-built Clang and runtime
libraries.

The goal is to make LLVM_BUILD_EXTERNAL_COMPILER_RT the default, so that
we can always build compiler-rt libraries with Clang, not the host compiler,
and for all the platforms Clang can target.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202367 91177308-0d34-0410-b5e6-96231b3b80d8

runtime/CMakeLists.txt

 # TODO: Set the install directory.
 
+include(ExternalProject)
+
 set(known_subdirs
-  "compiler-rt"
   "libcxx"
   )
 
@@ -10,3 +11,66 @@ foreach (dir ${known_subdirs})
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${dir})
   endif()
 endforeach()
+
+set(COMPILER_RT_SRC_ROOT ${LLVM_MAIN_SRC_DIR}/projects/compiler-rt)
+if(LLVM_BUILD_EXTERNAL_COMPILER_RT AND EXISTS ${COMPILER_RT_SRC_ROOT}/)
+  if(CMAKE_GENERATOR MATCHES "Ninja")
+    message(FATAL_ERROR
+            "Ninja generator can't build compiler-rt as ExternalProject."
+            "Unset LLVM_BUILD_EXTERNAL_COMPILER_RT, or don't use Ninja."
+            "See http://www.cmake.org/Bug/view.php?id=14771")
+  endif()
+
+  # Add compiler-rt as an external project.
+  set(COMPILER_RT_PREFIX ${CMAKE_BINARY_DIR}/projects/compiler-rt)
+  
+  ExternalProject_Add(compiler-rt
+    PREFIX ${COMPILER_RT_PREFIX}
+    SOURCE_DIR ${COMPILER_RT_SRC_ROOT}
+    CMAKE_ARGS -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
+               -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
+               -DCMAKE_BUILD_TYPE=Release
+               -DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
+               -DCOMPILER_RT_OUTPUT_DIR=${LLVM_LIBRARY_OUTPUT_INTDIR}/clang/${CLANG_VERSION}
+               -DCOMPILER_RT_EXEC_OUTPUT_DIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
+               -DCOMPILER_RT_INSTALL_PATH=lib${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}
+               -DCOMPILER_RT_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
+               -DCOMPILER_RT_ENABLE_WERROR=ON
+    INSTALL_COMMAND ""
+    )
+  # Due to a bug, DEPENDS in ExternalProject_Add doesn't work
+  # in CMake 2.8.9 and 2.8.10.
+  add_dependencies(compiler-rt llvm-config clang)
+
+  # Add a custom step to always re-configure compiler-rt (in case some of its
+  # sources have changed).
+  ExternalProject_Add_Step(compiler-rt force-reconfigure
+    DEPENDERS configure
+    ALWAYS 1
+    )
+
+  ExternalProject_Add_Step(compiler-rt clobber
+    COMMAND ${CMAKE_COMMAND} -E remove_directory <BINARY_DIR>
+    COMMAND ${CMAKE_COMMAND} -E make_directory <BINARY_DIR>
+    COMMENT "Clobberring compiler-rt build directory..."
+    DEPENDERS configure
+    DEPENDS ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
+  )
+
+  if (CMAKE_GENERATOR MATCHES "Make")
+    # Use special command for Makefiles to support parallelism.
+    set(check_command "$(MAKE)" "check-all")
+  else()
+    set(check_command ${CMAKE_COMMAND} --build . --target check-all
+                                       --config $<CONFIGURATION>)
+  endif()
+  ExternalProject_Get_Property(compiler-rt BINARY_DIR)
+  add_custom_target(check-compiler-rt
+          COMMAND ${check_command}
+          DEPENDS compiler-rt
+          WORKING_DIRECTORY ${BINARY_DIR}
+          VERBATIM)
+  # Add binaries that compiler-rt tests depend on.
+  add_dependencies(check-compiler-rt FileCheck count
+                                     not llvm-nm llvm-symbolizer)
+endif()