I'm writing some code that should utilize some type of vectorized instructions in order to compare two arrays consisting of 64-bit integers. I'm thinking of utilizing the SSE2 variant for cmpeq. The term I am getting stuck on is the term 'packed'.

Reading this post, I get the sense that packed simply means that there is no space between variables. This makes sense for me. However, reading assembly code for memcmp, they talk about alignment (note that the function compares bytes, and not 64-bit integers).

So, if I would like to compare the register xmm0 to something in the memory, does the memory address have to be 128-bit aligned, or is it okay for it to be only 64-bit aligned?