[jeffbee]

I think it's doubtful that around the time that POPCNT was added to CPUs the NSA was all that influential. Their big scary data center, which is actually tiny, wasn't built until 2014, while players like Google and Meta had much larger data centers years earlier and were undoubtedly larger buyers of AMD Barcelona / Intel Westmere where POPCNT first emerged.

[aleph_minus_one]

Here is an article about the popcnt instruction:

https://vaibhavsagar.com/blog/2019/09/08/popcount/

The author of the article believes that while popcnt was indeed used for cryptographical analysis in the 60s, but the fact that popcnt disappeared from instruction sets is seen as evidence that this usage became a lot less important over time. So the author considers the reason for the reappearance of popcnt that there simply exist lots of other useful applications of popcnt that become evident over these decades.

A German article about the same topic:

https://nickyreinert.medium.com/ne-49-popcount-ea62aa304f88

[dboreham]

Oh, when I saw this happen first-hand, it was probably 1986.

Note that the first "data center" I know of was built at Bletchley Park in the 1940s.