Re: [PATCH 1/3] crypto: X25519 low-level primitives for ppc64le.

Andy Polyakov
2024-05-15T09:07:01Z

Hi,

> +SYM_FUNC_START(x25519_fe51_sqr_times)
> ...
> +
> +.Lsqr_times_loop:
> ...
> +
> + std 9,16(3)
> + std 10,24(3)
> + std 11,32(3)
> + std 7,0(3)
> + std 8,8(3)
> + bdnz .Lsqr_times_loop

I see no reason for why the stores can't be moved outside the loop in
question.

> +SYM_FUNC_START(x25519_fe51_frombytes)
> +.align 5
> +
> + li 12, -1
> + srdi 12, 12, 13 # 0x7ffffffffffff
> +
> + ld 5, 0(4)
> + ld 6, 8(4)
> + ld 7, 16(4)
> + ld 8, 24(4)

Is there actual guarantee that the byte input is 64-bit aligned? While
it is true that processor is obliged to handle misaligned loads and
stores by the ISA specification, them being inefficient doesn't go
against it. Most notably inefficiency is likely to be noted at the page
boundaries. What I'm trying to say is that it would be more appropriate
to avoid the unaligned loads (and stores).

Cheers.