I'm pretty sure that your PR has disabled all SSE optimizations. AFAIK gcc does not enable SSE3 and SSE4 on X86_64 by default.

$ gcc -dM -E - < /dev/null | grep SSE
#define __SSE2_MATH__ 1
#define __SSE_MATH__ 1
#define __SSE2__ 1
#define __SSE__ 1

You have to set a compiler flag like -msse4

$ gcc -msse4 -dM -E - < /dev/null | grep SSE
#define __SSE4_1__ 1
#define __SSE4_2__ 1
#define __SSE2_MATH__ 1
#define __SSE_MATH__ 1
#define __SSE2__ 1
#define __SSSE3__ 1
#define __SSE__ 1
#define __SSE3__ 1