Index: compiler-rt/trunk/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/CMakeLists.txt
+++ compiler-rt/trunk/CMakeLists.txt
@@ -225,7 +225,7 @@
 # always respect the optimization flags set by CMAKE_BUILD_TYPE instead.
 if (NOT MSVC)
 
-  # Build with optimization, unless we're in debug mode. 
+  # Build with optimization, unless we're in debug mode.
   if(COMPILER_RT_DEBUG)
     list(APPEND SANITIZER_COMMON_CFLAGS -O0)
   else()
@@ -315,28 +315,16 @@
 
 add_subdirectory(include)
 
-set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/projects/libcxx)
-if(EXISTS ${COMPILER_RT_LIBCXX_PATH}/)
-  set(COMPILER_RT_HAS_LIBCXX_SOURCES TRUE)
-else()
-  set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/../libcxx)
-  if(EXISTS ${COMPILER_RT_LIBCXX_PATH}/)
-    set(COMPILER_RT_HAS_LIBCXX_SOURCES TRUE)
-  else()
-    set(COMPILER_RT_HAS_LIBCXX_SOURCES FALSE)
-  endif()
+set(COMPILER_RT_HAS_LIBCXX_SOURCES ${LLVM_PROJECT_LIBCXX_ENABLED})
+if (LLVM_PROJECT_LIBCXX_ENABLED)
+  set(COMPILER_RT_LIBCXX_PATH ${LLVM_PROJECT_LIBCXX_SOURCE_DIR})
+  message("compiler-rt libcxx enabled at ${COMPILER_RT_LIBCXX_PATH}")
 endif()
 
-set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/tools/lld)
-if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
-  set(COMPILER_RT_HAS_LLD TRUE)
-else()
-  set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/../lld)
-  if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
-    set(COMPILER_RT_HAS_LLD TRUE)
-  else()
-    set(COMPILER_RT_HAS_LLD FALSE)
-  endif()
+set(COMPILER_RT_HAS_LLD ${LLVM_PROJECT_LLD_ENABLED})
+if (LLVM_PROJECT_LLD_ENABLED)
+  set(COMPILER_RT_LLD_PATH ${LLVM_PROJECT_LLD_SOURCE_DIR})
+  message("compiler-rt lld enabled at ${COMPILER_RT_LLD_PATH}")
 endif()
 pythonize_bool(COMPILER_RT_HAS_LLD)
 
Index: llvm/trunk/CMakeLists.txt
===================================================================
--- llvm/trunk/CMakeLists.txt
+++ llvm/trunk/CMakeLists.txt
@@ -823,6 +823,25 @@
 include(AddLLVM)
 include(TableGen)
 
+
+# Find all subprojects which are either enabled in a side-by-side layout, or
+# cloned into a non-side-by-side layout.  Do this before adding any
+# subdirectories so that any project can check for the existence of any other
+# project.  Each call takes priority over the next call, so any project which
+# is enabled via LLVM_ENABLE_PROJECTS will not have its location or enabled
+# status overwritten via a subsequent call.
+
+# First look for all projects explicitly enabled at the root.
+find_llvm_enabled_projects("${LLVM_SOURCE_DIR}/.." "${LLVM_ENABLE_PROJECTS}")
+
+# Then pick up any projects explicitly cloned into llvm/projects or llvm/runtimes
+find_llvm_enabled_projects("${LLVM_SOURCE_DIR}/runtimes")
+find_llvm_enabled_projects("${LLVM_SOURCE_DIR}/projects")
+
+# Then pick up a few specific projects which can be explicit cloned into llvm/tools
+find_llvm_enabled_projects("${LLVM_SOURCE_DIR}/tools" "clang;lldb;lld")
+
+
 if( MINGW )
   # People report that -O3 is unreliable on MinGW. The traditional
   # build also uses -O2 for that reason:
Index: llvm/trunk/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/trunk/cmake/modules/AddLLVM.cmake
+++ llvm/trunk/cmake/modules/AddLLVM.cmake
@@ -687,7 +687,7 @@
     # it forces Xcode to properly link the static library.
     list(APPEND ALL_FILES "${LLVM_MAIN_SRC_DIR}/cmake/dummy.cpp")
   endif()
-  
+
   if( EXCLUDE_FROM_ALL )
     add_executable(${name} EXCLUDE_FROM_ALL ${ALL_FILES})
   else()
@@ -920,6 +920,37 @@
   set(${output} "${nameUPPER}" PARENT_SCOPE)
 endfunction(canonicalize_tool_name)
 
+macro(find_llvm_enabled_projects base_dir)
+  set(specific_project_list "${ARGN}")
+  if("${specific_project_list}" STREQUAL "")
+    file(GLOB entries "${base_dir}/*")
+    set(list_of_project_dirs "")
+    foreach(entry ${entries})
+      if(IS_DIRECTORY ${entry} AND EXISTS ${entry}/CMakeLists.txt)
+        get_filename_component(filename "${entry}" NAME)
+        list(APPEND specific_project_list "${filename}")
+      endif()
+    endforeach(entry)
+  endif()
+
+  foreach(proj ${specific_project_list})
+    canonicalize_tool_name(${proj} projUPPER)
+
+    if (${LLVM_PROJECT_${projUPPER}_ENABLED})
+      if (EXISTS "${base_dir}/${proj}")
+        message(WARNING "Project ${projUPPER} in ${base_dir}/${proj} previously found in ${LLVM_PROJECT_${projUPPER}_SOURCE_DIR}")
+      endif()
+      continue()
+    elseif(EXISTS "${LLVM_EXTERNAL_${projUPPER}_SOURCE_DIR}")
+      set(LLVM_PROJECT_${projUPPER}_ENABLED ON)
+      set(LLVM_PROJECT_${projUPPER}_SOURCE_DIR "${LLVM_EXTERNAL_${projUPPER}_SOURCE_DIR}")
+    elseif(EXISTS "${base_dir}/${proj}")
+      set(LLVM_PROJECT_${projUPPER}_ENABLED ON)
+      set(LLVM_PROJECT_${projUPPER}_SOURCE_DIR "${base_dir}/${proj}")
+    endif()
+  endforeach()
+endmacro()
+
 # Custom add_subdirectory wrapper
 # Takes in a project name (i.e. LLVM), the subdirectory name, and an optional
 # path if it differs from the name.
@@ -1350,7 +1381,7 @@
   # magic. First we grab one of the types, and a type-specific path. Then from
   # the type-specific path we find the last occurrence of the type in the path,
   # and replace it with CMAKE_CFG_INTDIR. This allows the build step to be type
-  # agnostic again. 
+  # agnostic again.
   if(NOT ARG_OUTPUT_DIR)
     # If you're not overriding the OUTPUT_DIR, we can make the link relative in
     # the same directory.