2017-04-01 5:44 GMT+02:00 Eric Biggers <ebigge...@gmail.com>: > Also, I realized that for gf128mul_x_lle() now that we aren't using the table > we > don't need to shift '_tt' but rather can use the constant 0xe100000000000000: > > /* equivalent to (u64)gf128mul_table_le[(b << 7) & 0xff] << 48 > * (see crypto/gf128mul.c): */ > u64 _tt = gf128mul_mask_from_bit(b, 0) & 0xe100000000000000; > > r->b = cpu_to_be64((b >> 1) | (a << 63)); > r->a = cpu_to_be64((a >> 1) ^ _tt); > > I think that would be better and you could send a v4 to do it that way if you > want. It's not a huge deal though.
Yes, I was hoping the compiler would be wise enough to fold the shift into the constant, but I didn't actually check the assembly output... I took the time to write a quick benchmark and the version without shift is indeed notably faster. That said, I'll go the extra mile and send a v4. Thanks for the review! O.M.
