Add -march=native for gcc-compat on Intel

not valid on arm or other archs. Only for gcc-compatible compilers.
30% faster on small samples than -flto

Author: rurban

CMakeLists.txt

@@ -238,6 +238,21 @@ if(ipo_supported)
   message(STATUS "IPO / LTO enabled")
   set_property(GLOBAL PROPERTY INTERPROCEDURAL_OPTIMIZATION True)
   add_definitions(-DLTO)
+  if ((CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "i386")
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "i586")
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "i686")
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "amd64") # freebsd
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "AMD64") # windows
+       OR (CMAKE_SYSTEM_PROCESSOR STREQUAL "x86"))
+     set(PROCESSOR_FAMILY "Intel")
+     if(CMAKE_COMPILER_IS_GNUCC
+         OR (CMAKE_CXX_COMPILER_ID STREQUAL AppleClang)
+         OR (CMAKE_CXX_COMPILER_ID STREQUAL Clang)
+         OR (CMAKE_CXX_COMPILER_ID STREQUAL Intel))
+       add_definitions(-march=native)
+     endif()
+  endif()
 else()
   message(STATUS "IPO / LTO not supported: <${error}>")
 endif()