Re: define pg_structiszero(addr, s, r)
От | Bertrand Drouvot |
---|---|
Тема | Re: define pg_structiszero(addr, s, r) |
Дата | |
Msg-id | ZzXuECLOduurf4NX@ip-10-97-1-34.eu-west-3.compute.internal обсуждение исходный текст |
Ответ на | Re: define pg_structiszero(addr, s, r) (Ranier Vilela <ranier.vf@gmail.com>) |
Список | 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
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