On 10/29/07, IOhannes m zmoelnig <zmoelnig@iem.at> wrote:
SSE2 is generally preferred over MMX since you can handle even more data
with single instructions (and/or other types)

A big chunk of SSE2 is a direct replacement for MMX as well.  The MMX code could serve as a template for the SSE2 replacement.  You still have the problem of nearly half a dozen SIMD variants to test for on x86 which is an ass pain.