I'm playing around with AVX instructions and came accross one named vperm2f128. So here's the thing. After executing (GAS syntax)
vperm2f128 $1, %ymm0, %ymm1, %ymm2
%ymm2 becomes %ymm1 second half followed by %ymm1 first half
What exactly happens with %ymm0 ? I mean how it's used in this instruction?