| From: | Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com> |
|---|---|
| To: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
| Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, David Rowley <dgrowleyml(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: define pg_structiszero(addr, s, r) |
| Date: | 2024-11-14 12:33:20 |
| Message-ID: | ZzXuECLOduurf4NX@ip-10-97-1-34.eu-west-3.compute.internal |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On Thu, Nov 14, 2024 at 09:13:19AM -0300, Ranier Vilela wrote:
> Em qui., 14 de nov. de 2024 às 08:58, Bertrand Drouvot <
> Maybe I'm doing something wrong.
> But I'm testing in 32-bit, with the size set to 63, with v12 and I'm seeing
> the SIMD loop execute.
Yeah, that's expected and safe as each iteration reads 32 bytes on 32-bit.
> if (len < sizeof(size_t) * 8) // 8-63 bytes
> failed.
>
> I expected that with size 63, it would be solved by case 2, or am I wrong?
Case 2 should be read as "in the 4-31" bytes range on 32-bit system as all
comparisons are done in size_t.
What would be unsafe on 32-bit would be to read up to 32 bytes while len < 32
and that can not happen.
As mentioned up-thread the comments are wrong on 32-bit, indeed they must be read
as:
Case 1: len < 4 bytes
Case 2: len in the 4-31 bytes range
Case 3: len >= 32 bytes
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Alvaro Herrera | 2024-11-14 12:38:56 | Re: Difference in dump from original and restored database due to NOT NULL constraints on children |
| Previous Message | Peter Eisentraut | 2024-11-14 12:31:35 | Re: SQL:2023 JSON simplified accessor support |