In further thought, if you have an instruction cache, adding 8 to SP is a faster way to discard the two useless values than popping them into unused registers.

In further thought, if you have an instruction cache, adding 8 to SP is a faster way to discard the two useless values than popping them into unused registers. So that part is arguably defensible. But why push them? There can't be a requirement for a 16-byte-aligned stack pointer at all times—the add would violate it.