Unfortunately, SSE - especially in integer-land, so I suppose we're talking SSE2 and beyond - often requires more specialist care and feeding than any automatic

Unfortunately, SSE - especially in integer-land, so I suppose we're talking SSE2 and beyond - often requires more specialist care and feeding than any automatic method (compiler or run-time) can provide. Some cases aren't hard to pick up (e.g. bulk operations on big arrays) but others require trickery of the kind that compilers usually don't (or couldn't) have. This isn't made easier by the notoriously non-orthogonal nature of the SSE integer operations and the rather limited number of ways that you can get in and out of SSE-land (to, say, affect a conditional or get something into a GPR).