Re: [PATCH] Hex-coding optimizations using SVE on ARM.

On Thu, Sep 04, 2025 at 02:55:50PM +0000, Chiranmoy(dot)Bhattacharya(at)fujitsu(dot)com wrote:
>> I see that there was some discussion about a Neon implementation upthread,
>> but I'm not sure we concluded anything. For popcount, we first added a
>> Neon version before adding the SVE version, which required more complicated
>> configure/runtime checks. Presumably Neon is available on more hardware
>> than SVE, so that could be a good place to start here, too.
>
> We have added the Neon versions of hex encode/decode.

Thanks. I noticed that this stuff is simple enough that we can use
port/simd.h (with a few added functions). This is especially nice because
it takes care of x86, too. The performance gains look similar to what you
reported for v6:

arm
buf | HEAD | patch | % diff
-------+-------+-------+--------
16 | 13 | 6 | 54
64 | 34 | 9 | 74
256 | 93 | 25 | 73
1024 | 281 | 78 | 72
4096 | 1086 | 227 | 79
16384 | 4382 | 927 | 79
65536 | 17455 | 3608 | 79

x86
buf | HEAD | patch | % diff
-------+-------+-------+--------
16 | 10 | 7 | 30
64 | 29 | 9 | 69
256 | 81 | 21 | 74
1024 | 286 | 66 | 77
4096 | 1106 | 253 | 77
16384 | 4383 | 980 | 78
65536 | 17491 | 3886 | 78

I've only modified hex_encode() for now, but I'm optimistic that we can do
something similar for hex_decode().

--
nathan