Index: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
@@ -17,6 +17,9 @@
   set(LINKER_IS_LLD_LINK FALSE)
 endif()
 
+set(LLVM_ENABLE_LTO OFF CACHE STRING "Build LLVM with LTO. May be specified as Thin or Full to use a particular kind of LTO")
+string(TOUPPER "${LLVM_ENABLE_LTO}" uppercase_LLVM_ENABLE_LTO)
+
 # Ninja Job Pool support
 # The following only works with the Ninja generator in CMake >= 3.0.
 set(LLVM_PARALLEL_COMPILE_JOBS "" CACHE STRING
@@ -32,16 +35,19 @@
 
 set(LLVM_PARALLEL_LINK_JOBS "" CACHE STRING
   "Define the maximum number of concurrent link jobs.")
-if(LLVM_PARALLEL_LINK_JOBS)
-  if(NOT CMAKE_MAKE_PROGRAM MATCHES "ninja")
-    message(WARNING "Job pooling is only available with Ninja generators.")
-  else()
+if(CMAKE_MAKE_PROGRAM MATCHES "ninja")
+  if(NOT LLVM_PARALLEL_LINK_JOBS AND uppercase_LLVM_ENABLE_LTO STREQUAL "THIN")
+    message(STATUS "ThinLTO provides its own parallel linking - limiting parallel link jobs to 2.")
+    set(LLVM_PARALLEL_LINK_JOBS "2")
+  endif()
+  if(LLVM_PARALLEL_LINK_JOBS)
     set_property(GLOBAL APPEND PROPERTY JOB_POOLS link_job_pool=${LLVM_PARALLEL_LINK_JOBS})
     set(CMAKE_JOB_POOL_LINK link_job_pool)
   endif()
+elseif(LLVM_PARALLEL_LINK_JOBS)
+  message(WARNING "Job pooling is only available with Ninja generators.")
 endif()
 
-
 if (LINKER_IS_LLD_LINK)
   # Pass /MANIFEST:NO so that CMake doesn't run mt.exe on our binaries.  Adding
   # manifests with mt.exe breaks LLD's symbol tables and takes as much time as
@@ -724,8 +730,6 @@
   CMAKE_EXE_LINKER_FLAGS
   CMAKE_SHARED_LINKER_FLAGS)
 
-set(LLVM_ENABLE_LTO OFF CACHE STRING "Build LLVM with LTO. May be specified as Thin or Full to use a particular kind of LTO")
-string(TOUPPER "${LLVM_ENABLE_LTO}" uppercase_LLVM_ENABLE_LTO)
 if(LLVM_ENABLE_LTO AND LLVM_ON_WIN32 AND NOT LINKER_IS_LLD_LINK)
   message(FATAL_ERROR "When compiling for Windows, LLVM_ENABLE_LTO requires using lld as the linker (point CMAKE_LINKER at lld-link.exe)")
 endif()