code that cross integer / floating point domains (e.g. generate pxor / pand for
logical ops on floating point value, movdqa to load / store floating point SSE
values). Given that, it's better to use movaps instead of movdqa and movups
instead of movdqu. They have the same latency but the "aps" variants are one
byte shorter.
If the domain crossing problem is a real performance issue, then we will have to
fix it with dynamic programming based isel.

llvm-svn: 40076