Date: Thu, 29 Jul 1999 09:59:36 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Jeff Wheat <jeff@cetlink.net> Cc: freebsd-alpha@freebsd.org Subject: Re: 3.2-RELEASE problems IEEE Math Message-ID: <Pine.BSF.4.10.9907290957400.385-100000@salmon.nlsystems.com> In-Reply-To: <XFMail.990728144524.jeff@cetlink.net>
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On Wed, 28 Jul 1999, Jeff Wheat wrote:
> Hi there. I am new to this list as recently installing 3.2
> on my alphastation 250 4/266. I must start by saying it was
> amazingly simple to install considering I was using the serial
> console!
>
> Anyhow, I am attempting to compile a package that uses IEEE math
> and I am running into trouble.
>
> Here is the test program:
>
> #include <signal.h>
> #include <floatingpoint.h>
> int main(void){
> double a;
> double b=22.0;
> double c;
> signal(SIGFPE,SIG_IGN);
> //# fpsetmask(0);
> a=0.0/0.0;
>
> c=b/a;
> if (!isnan(c)) return 1;
> c=a==c?1.0:0.0;
> if (c>0.0) return 1;
> c=a==c?1.0:0.0;
> if (c>0.0) return 1;
> c=a>c?1.0:0.0;
> if (c>0.0) return 1;
> c=a<c?1.0:0.0;
> if (c>0.0) return 1;
> c=a>=c?1.0:0.0;
> if (c>0.0) return 1;
> c=a<=c?1.0:0.0;
> if (c>0.0) return 1;
> return 0;
> }
>
> Here are the results:
> alpha# gcc nantest.c -o nantest ; ./nantest ; echo $?
> 1
> alpha# gcc nantest.c -O -o nantest ; ./nantest ; echo $?
> 0
> alpha# gcc nantest.c -O1 -o nantest ; ./nantest ; echo $?
> 0
> alpha# gcc nantest.c -O2 -o nantest ; ./nantest ; echo $?
> 0
> alpha# gcc nantest.c -ieee -o nantest ; ./nantest ; echo $?
> 1
>
> This seems odd that optimization would cause these differences.
>
> Can anyone suggest what the problem is?
The problem is that the alpha requires floating point code to be written
in a special way to allow NaNs. INFs and denorms to work properly.
Unfortunately the compiler in 3.2-RELEASE is not able to generate the
right code. This is fixed in -current (use the -mieee flag) and will be
fixed in 3.3 (different flags which I can't remember right now).
--
Doug Rabson Mail: dfr@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 442 9037
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