From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
        Andres Freund <andres@anarazel.de>
Subject: Re: NaN divided by zero should yield NaN
In-reply-to: 
 <CAEZATCX2-2doB6LTexN7LzAxQ6oSv2CbWZ=hCUqR-N2WN8n+zA@mail.gmail.com>
References: <3421746.1594927785@sss.pgh.pa.us>
 <CAEZATCX2-2doB6LTexN7LzAxQ6oSv2CbWZ=hCUqR-N2WN8n+zA@mail.gmail.com>
Comments: In-reply-to Dean Rasheed <dean.a.rasheed@gmail.com>
	message dated "Fri, 17 Jul 2020 19:08:53 +0100"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <767347.1595288784.1@sss.pgh.pa.us>
Date: Mon, 20 Jul 2020 19:46:24 -0400
Message-ID: <767348.1595288784@sss.pgh.pa.us>
Precedence: bulk

Dean Rasheed <dean.a.rasheed@gmail.com> writes:
> On Thu, 16 Jul 2020 at 20:29, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> One thing that's not very clear to me is which of these spellings
>> is preferable:
>> 	if (unlikely(val2 == 0.0) && !isnan(val1))
>> 	if (unlikely(val2 == 0.0 && !isnan(val1)))

> My guess is that the first would be better, since it would tell the
> compiler that it's unlikely to need to do the NaN test,

Yeah, that's the straightforward way to think about it, but I've
found that gcc is sometimes less than straightforward ;-).  Still,
there's no obvious reason to do it the second way, so I pushed the
first way.

			regards, tom lane