CMake: Allow build target arch to be overridden (#859)

* CMake: Allow build target arch to be overridden

* Add DNGRAPH_TARGET_ARCH option to install docs

CMakeLists.txt

@@ -111,8 +111,14 @@ endif()
 SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-g")
 SET(CMAKE_CXX_FLAGS_DEBUG  "-O0 -g")
 
-# Enable native CPU features
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native")
+# Enable build target CPU features
+set(NGRAPH_TARGET_ARCH native CACHE STRING "Target CPU architecture to build for. Defaults to the native CPU architecture")
+
+if (NOT "${NGRAPH_TARGET_ARCH}" STREQUAL "native")
+    message(WARNING "Build target architecture was overridden. The resulting build might not work correctly on the host CPU.")
+endif()
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=${NGRAPH_TARGET_ARCH}")
 
 # flags required for SDL-3
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O2 -fPIE -D_FORTIFY_SOURCE=2")

doc/sphinx/source/install.rst

@@ -80,7 +80,10 @@ The process documented here will work on Ubuntu\* 16.04 (LTS)
 #. Generate the GNUMakefiles in the customary manner (from within the 
    ``build`` directory). If running ``gcc-5.4.0`` or ``clang-3.9``, remember 
    that you can also append ``cmake`` with the prebuilt LLVM option to 
-   speed-up the build:
+   speed-up the build. Another option if your deployment system has Intel®
+   Advanced Vector Extensions (Intel® AVX) is to target the accelerations 
+   available directly by compiling the build as follows during the cmake 
+   step: ``-DNGRAPH_TARGET_ARCH=skylake-avx512``.
 
    .. code-block:: console