Re: optimize lookups in snapshot [sub]xip arrays - Mailing list pgsql-hackers

From Nathan Bossart
Subject Re: optimize lookups in snapshot [sub]xip arrays
Date
Msg-id 20220730053811.GA417958@nathanxps13
Whole thread Raw
In response to Re: optimize lookups in snapshot [sub]xip arrays  (John Naylor <john.naylor@enterprisedb.com>)
Responses Re: optimize lookups in snapshot [sub]xip arrays
List pgsql-hackers
On Sat, Jul 30, 2022 at 12:02:02PM +0700, John Naylor wrote:
> On Fri, Jul 29, 2022 at 4:34 AM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>>  * I borrowed USE_SSE2 from one of John Naylor's patches [0].  I'm not
> sure
>>    whether this is committable,
> 
> I'll be the first to say it's not committable and needs some thought. Since
> there are several recently proposed patches that take advantage of SSE2, it
> seems time for me to open a new thread and get that prerequisite settled.
> I'll do that next week.

Awesome.  I will help test and review.

>> so I would welcome thoughts on the proper
>>    form.  Given the comment says that SSE2 is supported by all x86-64
>>    hardware, I'm not seeing why we need the SSE 4.2 checks.  Is it not
>>    enough to check for __x86_64__ and _M_AMD64?
> 
> That's enough for emitting instructions that the target CPU can run, but
> says nothing (I think) about the host compiler's ability to understand the
> intrinsics and associated headers. The architecture is old enough that
> maybe zero compilers in the buildfarm that target AMD64 fail to understand
> SSE2 intrinsics, but I hadn't looked into it. The SSE 4.2 intrinsics check
> is not necessary, but it was sufficient and already present, so I borrowed
> it for the PoC.

Got it, makes sense.

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



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