>Number:         8315
>Category:       lib
>Synopsis:       ARM32 bad floating point comparisons with NaNs
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people (Library Bug People)
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep  3 04:35:01 1999
>Last-Modified:
>Originator:     Richard Earnshaw
>Organization:
ARM
-- 
>Release:        -current <NetBSD-current source date>
>Environment:
	
System: NetBSD shark1 1.4K NetBSD 1.4K (SHARK) #44: Mon Aug 30 17:37:22 BST 1999 rearnsha@shark1:/usr/src/sys/arch/arm32/compile/SHARK arm32


>Description:
	The soft-float library for the arm32 port gets comparisons with NaNs
	wrong.  This is because it assumes that "<" can be implemented as
	"Not (>=)".  This is invalid if either operand is a NaN, since
	such comparisons are unordered should always be false.

	An additional enhancement could also be made to the soft-float code,
	in that the implementation has hooks to raise an exception, but
	currently doesn't do anything.  It would be reasonable for this hook
	to "raise(SIGFPE)".

	
>How-To-Repeat:

	The following test case demonstrates the problem, note it also 
	applies if double is replaced with float.

#include <signal.h>
double nan = 1.0/0.0 - 1.0/0.0;
double x = 1.0;

void leave ()
{
  exit (0);
}

main ()
{
  signal (SIGFPE, leave);
  /* NaN is an IEEE unordered operand.  All these test should be false.  */
  if (nan == nan)
    abort ();
  if (nan != x)  x = 1.0;
  else           abort ();

  if (nan < x)   abort ();
  if (nan > x)   abort ();
  if (nan <= x)  abort ();
  if (nan >= x)  abort ();
  if (nan == x)  abort ();
  exit (0);
}

	
>Fix:

	The __gtsf __gesf __gtdf & __gedf functions all need to take NaNs
	into correctly account.  It isn't correct to use the corresponding
	less-than function and reverse the result.
	
>Audit-Trail:
>Unformatted: