[Cryptography] Finding undocumented opcodes

[Ray Dillinger]

On 08/05/2017 08:54 PM, Dave Horsfall wrote:
> But speaking of weird opcodes, there is the "population count"
> instruction on the CDC series; it counted the number of "1" bits in a
> (60-bit) word, and was known as the "NSA Instruction" (at first glance,
> it appeared to have no use at all, but Seymour Cray wouldn't have
> included it for no reason).

This opcode calculates Hamming Weight.  It is useful in providing
an additional dimension for rapid location of data in large multiply-
indexed data structures.  I have synthesized it myself using binary
comparisons for that purpose.

				Bear






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