Date: Sat, 27 Aug 2022 15:15:02 -0700
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: John Naylor <john.naylor@enterprisedb.com>,
	Andres Freund <andres@anarazel.de>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: use ARM intrinsics in pg_lfind32() where available
Message-ID: <20220827221502.GB15951@nathanxps13>
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 <20220825045729.GA1458024@nathanxps13>
 <CAFBsxsHa9QmLk33c5C-12Uuh35Ofv+qzbT+auGrqC3fQCorqBg@mail.gmail.com>
 <20220826045115.GA1638993@nathanxps13>
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 <20220826182403.GA1917683@nathanxps13>
 <CAFBsxsF=K1Vo4fZELJMCSF8GGbcrC_FnkMt3sQcBZt=MExmjPA@mail.gmail.com>
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On Sat, Aug 27, 2022 at 05:18:34PM -0400, Tom Lane wrote:
> In short, I think the critical part of 0002 needs to look more like
> this:
> 
> +#elif defined(__aarch64__) && defined(__ARM_NEON)
> +/*
> + * We use the Neon instructions if the compiler provides access to them
> + * (as indicated by __ARM_NEON) and we are on aarch64.  While Neon support is
> + * technically optional for aarch64, it appears that all available 64-bit
> + * hardware does have it.  Neon exists in some 32-bit hardware too, but
> + * we could not realistically use it there without a run-time check,
> + * which seems not worth the trouble for now.
> + */
> +#include <arm_neon.h>
> +#define USE_NEON
> ...

Thank you for the analysis!  I'll do it this way in the next patch set.

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