| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de> |
| Subject: | Re: NaN divided by zero should yield NaN |
| Date: | 2020-07-20 23:46:24 |
| Message-ID: | 767348.1595288784@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> writes:
> On Thu, 16 Jul 2020 at 20:29, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
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