Use ninja pools to limit the number of concurrent compile/link jobs.

This change makes use of the new "job pool" capability in cmake 3.0
with ninja generator to allow limiting the number of concurrent jobs
of a certain type.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222341 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -24,6 +24,21 @@ endif()
 
 project(LLVM)
 
+# The following only works with the Ninja generator in CMake >= 3.0.
+set(LLVM_PARALLEL_COMPILE_JOBS "" CACHE STRING
+  "Define the maximum number of concurrent compilation jobs.")
+if(LLVM_PARALLEL_COMPILE_JOBS)
+  set_property(GLOBAL APPEND PROPERTY JOB_POOLS compile_job_pool=${LLVM_PARALLEL_COMPILE_JOBS})
+  set(CMAKE_JOB_POOL_COMPILE compile_job_pool)
+endif()
+
+set(LLVM_PARALLEL_LINK_JOBS "" CACHE STRING
+  "Define the maximum number of concurrent link jobs.")
+if(LLVM_PARALLEL_LINK_JOBS)
+  set_property(GLOBAL APPEND PROPERTY JOB_POOLS link_job_pool=${LLVM_PARALLEL_LINK_JOBS})
+  set(CMAKE_JOB_POOL_LINK link_job_pool)
+endif()
+
 # Add path for custom modules
 set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}

docs/CMake.rst

@@ -291,6 +291,12 @@ LLVM-specific variables
   are ``Address``, ``Memory``, ``MemoryWithOrigins`` and ``Undefined``.
   Defaults to empty string.
 
+**LLVM_PARALLEL_COMPILE_JOBS**:STRING
+  Define the maximum number of concurrent compilation jobs.
+
+**LLVM_PARALLEL_LINK_JOBS**:STRING
+  Define the maximum number of concurrent link jobs.
+
 **LLVM_BUILD_DOCS**:BOOL
   Enables all enabled documentation targets (i.e. Doxgyen and Sphinx targets) to
   be built as part of the normal build. If the ``install`` target is run then