I remember the 80386 where the pushad/popad instructions could go wrong, up to locking up the whole cpu, but only if the next instruction did something specific

I remember the 80386 where the pushad/popad instructions could go wrong, up to locking up the whole cpu, but only if the next instruction did something specific to eax. So at least i386 had enough complexity to make the next instruction relevant for the previous, even if the thing had almost no pipelining.