* An alpha IEEE bug
@ 1998-02-07 12:43 RHS Linux User
1998-02-07 14:47 ` Richard Henderson
1998-02-09 2:33 ` Klaus Kaempf
0 siblings, 2 replies; 5+ messages in thread
From: RHS Linux User @ 1998-02-07 12:43 UTC (permalink / raw)
To: egcs; +Cc: rth
Hi,
There is a bug in the IEEE math on linux/alpha:
# gcc -mieee ieee.c
# a.out
7f800000
1
# gcc -mieee ieee.c -O
# a.out
zsh: 744 abort ./a.out
# gdb a.out
GDB is free software and you are welcome to distribute copies of it
under certain conditions; type "show copying" to see the conditions.
There is absolutely no warranty for GDB; type "show warranty" for details.
GDB 4.16 (alpha-redhat-linux), Copyright 1996 Free Software Foundation, Inc...
(gdb) b isinff
Breakpoint 1 at 0x120000780: file ieee.c, line 16.
(gdb) r
Starting program: /home/work/alpha/bugs/math/a.out
Breakpoint 1, isinff (x=Erroneous arithmetic operation.) at ieee.c:16
16 if (ix == 0)
(gdb)
Can someone please run this on other alpha platforms?
Thanks.
--
H.J. Lu (hjl@gnu.org)
----
#include <stdio.h>
typedef int int32_t __attribute__ ((__mode__ ( __SI__ ))) ;
typedef union
{
float value;
int32_t word;
} ieee_float_shape_type;
int isinff(float x)
{
int32_t ix,t;
ieee_float_shape_type gf_u;
gf_u.value = x;
ix = gf_u.word;
if (ix == 0)
abort ();
else
printf ("%x\n", ix);
t = ix & 0x7fffffff;
t ^= 0x7f800000;
t |= -t;
return ~(t >> 31) & (1 - ((ix & 0x80000000) >> 30));
}
main ()
{
float x = 1.0 / 0.0;
printf ("%d\n", isinff (x));
return 0;
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: An alpha IEEE bug
1998-02-07 12:43 An alpha IEEE bug RHS Linux User
@ 1998-02-07 14:47 ` Richard Henderson
1998-02-09 2:33 ` Klaus Kaempf
1 sibling, 0 replies; 5+ messages in thread
From: Richard Henderson @ 1998-02-07 14:47 UTC (permalink / raw)
To: RHS Linux User; +Cc: egcs, rth
On Sat, Feb 07, 1998 at 12:28:16PM -0800, RHS Linux User wrote:
> There is a bug in the IEEE math on linux/alpha:
It is a bug in combine. Look at -O without -mieee -- it doesn't
abort but it gives wrong results.
I'll see what I can do.
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: An alpha IEEE bug
1998-02-07 12:43 An alpha IEEE bug RHS Linux User
1998-02-07 14:47 ` Richard Henderson
@ 1998-02-09 2:33 ` Klaus Kaempf
1998-02-09 14:22 ` Richard Henderson
1 sibling, 1 reply; 5+ messages in thread
From: Klaus Kaempf @ 1998-02-09 2:33 UTC (permalink / raw)
To: RHS Linux User; +Cc: egcs
>
> Hi,
>
> There is a bug in the IEEE math on linux/alpha:
>
> # gcc -mieee ieee.c
> # a.out
> 7f800000
> 1
> # gcc -mieee ieee.c -O
> # a.out
> zsh: 744 abort ./a.out
On openVMS/Alpha I get a different output (without optimization):
3f800000
0
It also calls abort() when compiled with optimization.
Klaus
--
proGIS Software E-Mail: kkaempf@progis.de
Dipl.-Inform. Klaus K"ampf Fax: 0241-47067-29
Jakobstr. 117 Voice: 0241-47067-11
D-52064 Aachen WWW: http://www.progis.de
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: An alpha IEEE bug
1998-02-09 2:33 ` Klaus Kaempf
@ 1998-02-09 14:22 ` Richard Henderson
1998-02-10 0:53 ` Klaus Kaempf
0 siblings, 1 reply; 5+ messages in thread
From: Richard Henderson @ 1998-02-09 14:22 UTC (permalink / raw)
To: Klaus Kaempf; +Cc: RHS Linux User, egcs
On Mon, Feb 09, 1998 at 11:27:24AM +0100, Klaus Kaempf wrote:
> On openVMS/Alpha I get a different output (without optimization):
>
> 3f800000
> 0
OpenVMS uses F and G format floats, no?
> It also calls abort() when compiled with optimization.
Probably the same combine problem though.
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: An alpha IEEE bug
1998-02-09 14:22 ` Richard Henderson
@ 1998-02-10 0:53 ` Klaus Kaempf
0 siblings, 0 replies; 5+ messages in thread
From: Klaus Kaempf @ 1998-02-10 0:53 UTC (permalink / raw)
To: rth; +Cc: egcs
>
> On Mon, Feb 09, 1998 at 11:27:24AM +0100, Klaus Kaempf wrote:
> > On openVMS/Alpha I get a different output (without optimization):
> >
> > 3f800000
> > 0
>
> OpenVMS uses F and G format floats, no?
>
No ! GNU C on openVMS/Alpha uses IEEE floats, I never tried to get it running
with the old VAX floating formats.
--
proGIS Software E-Mail: kkaempf@progis.de
Dipl.-Inform. Klaus K"ampf Fax: 0241-47067-29
Jakobstr. 117 Voice: 0241-47067-11
D-52064 Aachen WWW: http://www.progis.de
^ permalink raw reply [flat|nested] 5+ messages in thread
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1998-02-07 12:43 An alpha IEEE bug RHS Linux User
1998-02-07 14:47 ` Richard Henderson
1998-02-09 2:33 ` Klaus Kaempf
1998-02-09 14:22 ` Richard Henderson
1998-02-10 0:53 ` Klaus Kaempf
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