Even if you're working at the PhD level, a course is only going to at best give you a survey of material instead of the latest-and-greatest papers hot off the presses at PLDI or ASPLOS or whatever conferences matter most for your field. If you're actually doing research on a particular subfield, then you are going to be finding and reading those papers on your own.
In that vein, it makes a lot more sense to focus on a solid, foundational paper than whatever incrementalism came out most recently. SLP vectorization is a good example here--yeah, the foundational paper is 20 years old at this point, but you'd rather students read and understand that than whatever the most recent addition to SLP vectorization came out in this (or last) year's PLDI. Even the other papers I think I might add or substitute for others in this course aren't going to be substantially newer than the stuff already here.