Now that we have 64-bit C code, courtesy of fiat-crypto, the tradeoff
for carrying the assembly changes:
Assembly:
Did 16000 Curve25519 base-point multiplication operations in 1059932us (15095.3 ops/sec)
Did 16000 Curve25519 arbitrary point multiplication operations in 1060023us (15094.0 ops/sec)
fiat64:
Did 39000 Curve25519 base-point multiplication operations in 1004712us (38817.1 ops/sec)
Did 14000 Curve25519 arbitrary point multiplication operations in 1006827us (13905.1 ops/sec)
The assembly is still about 9% faster than fiat64, but fiat64 gets to
use the Ed25519 tables for the base point multiplication, so overall it
is actually faster to disable the assembly:
>>> 1/(1/15094.0 + 1/15095.3)
7547.324986004976
>>> 1/(1/38817.1 + 1/13905.1)
10237.73016319501
(At the cost of touching a 30kB table.)
The assembly implementation is no longer pulling its weight. Remove it
and use the fiat code in all build configurations.
Change-Id: Id736873177d5568bb16ea06994b9fcb1af104e33
Reviewed-on: https://boringssl-review.googlesource.com/25524
Reviewed-by: Adam Langley <agl@google.com>
884086e0e2