25 Sep
2020
25 Sep
'20
10:24 a.m.
Jeffrey Walton noloader@gmail.com writes:
I believe the 64-bit adds (addudm) and subtracts (subudm) require POWER8.
I don't think there are any 64-bit adds in my chacha code, only 32-bit, vadduwm. The chacha state is fundamentally 16 32-bit words, with operations very friendly to 4-way simd.
Using 64-bit adds might be useful for later code doing multiple blocks, for updating the counter (for the original 64-bit counter variant of chacha). Might make sense to do manual carry handling to keep it working on power7.
So it would make sense to add the code to a new directory powerpc64/p7/ ?
Regards, /Niels
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Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
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