Re: NaN divided by zero should yield NaN - Mailing list pgsql-hackers

From Tom Lane
Subject Re: NaN divided by zero should yield NaN
Date
Msg-id 767348.1595288784@sss.pgh.pa.us
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In response to Re: NaN divided by zero should yield NaN  (Dean Rasheed <dean.a.rasheed@gmail.com>)
List pgsql-hackers
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



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