standards/59797: Implement C99's round[f]() math fucntions

[David Schultz]

The following reply was made to PR standards/59797; it has been noted by GNATS.

From: David Schultz <das at FreeBSD.ORG>
To: "Steven G. Kargl" <kargl at troutmask.apl.washington.edu>
Cc: FreeBSD-gnats-submit at FreeBSD.ORG, freebsd-standards at FreeBSD.ORG
Subject: Re: standards/59797: Implement C99's round[f]() math fucntions
Date: Sun, 6 Jun 2004 23:38:43 -0700

 On Sun, Jun 06, 2004, Steven G. Kargl wrote:
 > I would have to go back and review the PR for all the discussion,
 > but I thought bde had proposed using rint(3) with an appropriate
 > rounding mode.  Anyway, whatever you decide to do is fine with
 > me. 
 
 I found that setting the rounding mode and calling rint(3) is
 significantly slower on x87, and that's not counting the special
 handling for the halfway cases.  The bit-fiddling approach is a
 little bit faster than yours (I compared against ceil()), but it's
 much harder to maintain.  Consider that rintf() still has bugs,
 and it has been around for over a decade!
 
 > I looked at the glibc implementation of round().  It does
 > bit twiddling, but I would definitely recommend not using
 > the glibc version because of licensing and possible copyright
 > infringement concerns [hiint compare glibc's round() with
 > fdlibm's ceil()].
 
 Hmmm...the glibc implementation does indeed appear to be
 plagiarized.  Perhaps someone should let the glibc folks know.