Re: [PATCH] SVE popcount support

Nathan Bossart <nathandbossart@gmail.com>

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: 2025-03-03T23:00:52Z

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 →

Optimize popcount functions with ARM SVE intrinsics.
- 519338ace410 18.0 landed
Optimize popcount functions with ARM Neon intrinsics.
- 6be53c27673a 18.0 landed
Rename TRY_POPCNT_FAST to TRY_POPCNT_X86_64.
- 9ac6f7e7ceb6 18.0 landed

On Wed, Feb 19, 2025 at 09:31:50AM +0000, Chiranmoy.Bhattacharya@fujitsu.com wrote:
>> Hm.  Any idea why that is?  I wonder if the compiler isn't using as many
>> SVE registers as it could for this.
> 
> Not sure, we tried forcing loop unrolling using the below line in the MakeFile
> but the results are the same.
> 
> pg_popcount_sve.o: CFLAGS += ${CFLAGS_UNROLL_LOOPS} -march=native

Interesting.  I do see different assembly with the 2 and 4 register
versions, but I didn't get to testing it on a machine with SVE support
today.

Besides some additional benchmarking, I might make some small adjustments
to the patch.  But overall, it seems to be in decent shape.

-- 
nathan