Re: [PATCH] Optimize json_lex_string by batching character copying

On Mon, Aug 15, 2022 at 08:33:21PM +0700, John Naylor wrote:
> The attached implements the above, more or less, using new pg_lfind8()
> and pg_lfind8_le(), which in turn are based on helper functions that
> act on a single vector. The pg_lfind* functions have regression tests,
> but I haven't done the same for json yet. I went the extra step to use
> bit-twiddling for non-SSE builds using uint64 as a "vector", which
> still gives a pretty good boost (test below, min of 3):

Looks pretty reasonable to me.

> +#ifdef USE_SSE2
> +        chunk = _mm_loadu_si128((const __m128i *) &base[i]);
> +#else
> +        memcpy(&chunk, &base[i], sizeof(chunk));
> +#endif                            /* USE_SSE2 */

> +#ifdef USE_SSE2
> +        chunk = _mm_loadu_si128((const __m128i *) &base[i]);
> +#else
> +        memcpy(&chunk, &base[i], sizeof(chunk));
> +#endif                            /* USE_SSE2 */

Perhaps there should be a macro or inline function for loading a vector so
that these USE_SSE2 checks can be abstracted away, too.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com