It seems that SSE4 extensions are needed to be vulnerable, otherwise memcmp() is doing classical computations.
So you need a 64 bits system, and be sure that you are not using a virtualisation system which does clear SSSE4 flag in /proc/cpuinfo (VirtualBox does).
So you need a 64 bits system, and be sure that you are not using a virtualisation system which does clear SSSE4 flag in /proc/cpuinfo (VirtualBox does).