Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!sun-spots-request
From: grunwald@flute.cs.uiuc.edu
Newsgroups: comp.sys.sun
Subject: Re: libm in SunOS 4.0
Keywords: Software
Message-ID: <GRUNWALD.89May3100917@flute.cs.uiuc.edu>
Date: 9 May 89 23:10:54 GMT
References: <8904130100.AA14938@dgh.sun.com>
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Organization: University of Illinois, Urbana-Champaign
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Original-Date: 3 May 89 15:09:17 GMT
X-Sun-Spots-Digest: Volume 7, Issue 279, message 5 of 23

I would like to point out that with Gnu C 1.35, using the 68881 version of
math.h with inlined math functions, Gnu C produces exactly the same code
that David Hugh posted, modulo label names.

An example inline specification for Gnu C is:

__inline static const double sin (double x)
{
  double value;
  __asm ("fsin%.x %1,%0" : "=f" (value) : "f" (x));
  return value;
}

which has similar advantages to the .il template method mentioned;
however, it has further advantages, similar to the ones mentioned for
FORTRAN. Most notably, CSE and code hoisting can move the function out of
loops, although I imagine this would rarely occur for math functions.
There are other advantages of combining inline & smarter asm() notation :
you can inline other time-critical functions (e.g. spl(), spinlock loops,
etc).


--
Dirk Grunwald
Univ. of Illinois
grunwald@flute.cs.uiuc.edu