-xmemalign=1s

There are many misaligned accesses so trap handling is too slow. 

-xmemalign=8i

There are occasional, intentional, misaligned accesses in code that is otherwise correct. 

-xmemalign=8s

There should be no misaligned accesses in the program. 

-xmemalin=2s

You want to check for possible odd-byte accesses. 

-xmemalign=2i

You want to check for possible odd-byte access and you want the program to work.