3-arg AVX ops with a memory arg can only have it in src2,
whereas SSE emulation of 3-arg prefers to have it in src1 (i.e. the move).
So, if the op is symmetric and the wrong one is memory, swap them.
Eliminates redundant moves in some cases when using 3-operand without AVX with memory arguments.
Also fix movss and movsd in some cases, and flag shufps correctly as float.