Re: y0/y1/yn and exceptions - GCC 3.4 changes

[Andreas Jaeger <aj at suse dot de>]

Andreas Schwab <schwab@suse.de> writes:

> Roger Sayle <roger@eyesopen.com> writes:
>
>> Of course, this issue applies to y0, y1 and yn, and the above changes
>> will need to be made consistently to flt-32, dbl-64, ldbl-96 and ldbl-128.
>
> The same issue exists with exp, exp10 and tgamma (on ppc):

And on x86-64 where I tested the patch below.

> Failure: exp (NaN) == NaN: Exception "Invalid operation" set
> Failure: exp10 (NaN) == NaN: Exception "Invalid operation" set
> Failure: tgamma (NaN) == NaN: Exception "Invalid operation" set

This comes from sysdeps/ieee754/dbl-64/e_exp.c:

    if (n > infint) return(zero/zero);               /* x is NaN,  return invalid */

IMO we should return just the Nan without raising execptions.

Ok to commit the appended patch?  This fixes all three problems above.

Andreas

2003-12-28  Andreas Jaeger  <aj@suse.de>

	* sysdeps/ieee754/dbl-64/e_exp.c: Do not raise execptions for
	exp(NaN).

============================================================
Index: sysdeps/ieee754/dbl-64/e_exp.c
--- sysdeps/ieee754/dbl-64/e_exp.c	26 Aug 2002 22:40:36 -0000	1.8
+++ sysdeps/ieee754/dbl-64/e_exp.c	28 Dec 2003 10:15:50 -0000
@@ -92,10 +92,10 @@ double __ieee754_exp(double x) {
   if (n <= smallint) return 1.0;
 
   if (n >= badint) {
-    if (n > infint) return(zero/zero);               /* x is NaN,  return invalid */
+    if (n > infint) return(x+x);               /* x is NaN */
     if (n < infint) return ( (x>0) ? (hhuge*hhuge) : (tiny*tiny) );
     /* x is finite,  cause either overflow or underflow  */
-    if (junk1.i[LOW_HALF] != 0)  return (zero/zero);                /*  x is NaN  */
+    if (junk1.i[LOW_HALF] != 0)  return (x+x);                /*  x is NaN  */
     return ((x>0)?inf.x:zero );             /* |x| = inf;  return either inf or 0 */
   }
 

-- 
 Andreas Jaeger, aj@suse.de, http://www.suse.de/~aj
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