Make the SSE string operations faster

Deadlock and more importantly Unreal Engine 3 (A hat in Time is a good one) abuse the SSE string operations. Specifically pcmpistri xmm0, xmm1, 0xd in UE3 and pcmpistri xmm0, xmm1, 0xc in Deadlock.

We can make these instructions faster, especially with some SVE operations being pretty good for flag setting. Determine what it would take to convert these instructions to inline ASM rather than jumping out to a C helper.