+#------------------------------------------------------------------------
+# LLVMBuild Integration
+#------------------------------------------------------------------------
+#
+# We use llvm-build to generate all the data required by the Makefile based
+# build system in one swoop:
+#
+# - We generate a file (a Makefile fragment) in the object root which contains
+# all the definitions that are required by Makefiles across the entire
+# project.
+#
+# - We generate the library table used by llvm-config.
+#
+# - We generate the dependencies for the Makefile fragment, so that we will
+# automatically reconfigure outselves.
+
+# The path to the llvm-build tool itself.
+LLVMBuildTool := $(PROJ_SRC_ROOT)/utils/llvm-build/llvm-build
+
+# The files we are going to generate using llvm-build.
+LLVMBuildMakeFrag := $(PROJ_OBJ_ROOT)/Makefile.llvmbuild
+LLVMBuildCMakeFrag := $(PROJ_OBJ_ROOT)/LLVMBuild.cmake
+LLVMBuildCMakeExportsFrag := $(PROJ_OBJ_ROOT)/cmake/modules/LLVMBuildExports.cmake
+LLVMBuildMakeFrags := \
+ $(LLVMBuildMakeFrag) \
+ $(LLVMBuildCMakeFrag) \
+ $(LLVMBuildCMakeExportsFrag)
+LLVMConfigLibraryDependenciesInc := \
+ $(PROJ_OBJ_ROOT)/tools/llvm-config/LibraryDependencies.inc
+
+# This is for temporary backwards compatibility.
+ifndef TARGET_NATIVE_ARCH
+TARGET_NATIVE_ARCH := $(ARCH)
+endif
+
+# The rule to create the LLVMBuild Makefile fragment as well as the llvm-config
+# library table.
+#
+# Note that this target gets its real dependencies generated for us by
+# llvm-build.
+#
+# We include a dependency on this Makefile to ensure that changes to the
+# generation command get picked up.
+$(LLVMBuildMakeFrags): $(PROJ_SRC_ROOT)/Makefile.rules \
+ $(PROJ_OBJ_ROOT)/Makefile.config
+ $(Echo) Constructing LLVMBuild project information.
+ $(Verb)$(PYTHON) $(LLVMBuildTool) \
+ --native-target "$(TARGET_NATIVE_ARCH)" \
+ --enable-targets "$(TARGETS_TO_BUILD)" \
+ --enable-optional-components "$(OPTIONAL_COMPONENTS)" \
+ --write-library-table $(LLVMConfigLibraryDependenciesInc) \
+ --write-make-fragment $(LLVMBuildMakeFrag) \
+ --write-cmake-fragment $(LLVMBuildCMakeFrag) \
+ --write-cmake-exports-fragment $(LLVMBuildCMakeExportsFrag)
+
+# For completeness, let Make know how the extra files are generated.
+$(LLVMConfigLibraryDependenciesInc): $(LLVMBuildMakeFrags)
+
+# Include the generated Makefile fragment.
+#
+# We currently only include the dependencies for the fragment itself if we are
+# at the top-level. Otherwise, recursive invocations would ends up doing
+# substantially more redundant stat'ing.
+#
+# This means that we won't properly regenerate things for developers used to
+# building from a subdirectory, but that is always somewhat unreliable.
+ifeq ($(LEVEL),.)
+LLVMBUILD_INCLUDE_DEPENDENCIES := 1
+
+# Clean the generated makefile fragment at the top-level.
+clean-local::
+ -$(Verb) $(RM) -f $(LLVMBuildMakeFrags)
+endif
+-include $(LLVMBuildMakeFrag)
+