Horton

Re: [PATCH] SVE popcount support

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: "Chiranmoy.Bhattacharya@fujitsu.com" <Chiranmoy.Bhattacharya@fujitsu.com>
Cc: "Malladi, Rama" <ramamalladi@hotmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, "Ragesh.Hajela@fujitsu.com" <Ragesh.Hajela@fujitsu.com>, Salvatore Dipietro <dipiets@amazon.com>, "Devanga.Susmitha@fujitsu.com" <Devanga.Susmitha@fujitsu.com>
Date: 2025-02-06T16:33:35Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Optimize popcount functions with ARM SVE intrinsics.

  2. Optimize popcount functions with ARM Neon intrinsics.

  3. Rename TRY_POPCNT_FAST to TRY_POPCNT_X86_64.

On Thu, Feb 06, 2025 at 08:44:35AM +0000, Chiranmoy.Bhattacharya@fujitsu.com wrote:
>> Does this hand-rolled loop unrolling offer any particular advantage?  What
>> do the numbers look like if we don't do this or if we process, say, 4
>> vectors at a time?
> 
> The unrolled version performs better than the non-unrolled one, but
> processing four vectors provides no additional benefit. The numbers
> and code used are given below.

Hm.  Any idea why that is?  I wonder if the compiler isn't using as many
SVE registers as it could for this.

-- 
nathan