Add support for multiple microarchitectures in single binary

 * compiler -march= parameter is changed from native to corei7
   so code is always genereted with instructions which are available
   on the Nehalem microarchitecture (up to SSE4.2)

 * compiler -mtune= parameter is added so code is optimized for
   corei7-avx which equals to Sandy Bridge microarchitecture

 * set of macros is added which allows run-time detection of available
   cpu instructions (e.g. clib_cpu_supports_avx())

 * set of macros is added which allows us to clone graph node funcitons
   where cloned function is optmized for different microarchitecture
   Those macros are using following attributes:
     __attribute__((flatten))
     __attribute__((target("arch=core-avx2)))

   I.e. If applied to foo_node_fn() macro will generate cloned
   functions foo_node_fn_avx2() and foo_node_fn_avx512() (future)
   It will also generate function void * foo_node_fn_multiarch_select()
   which detects available instruction set and returns pointer to the
   best matching function clone.

Change-Id: I2dce0ac92a5ede95fcb56f47f3d1f3c4c040bac0
Signed-off-by: Damjan Marion <damarion@cisco.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/build-root/Makefile b/build-root/Makefile
index a60cbf0a22e..97fb43d49ee 100644
--- a/build-root/Makefile
+++ b/build-root/Makefile
@@ -220,6 +220,11 @@ else
 endif
 export MARCH
 
+MTUNE = $(strip $($(PLATFORM)_mtune))
+ifeq ($(MTUNE),)
+  MTUNE = generic
+endif
+
 ######################################################################
 # Generic build stuff
 ######################################################################