[Qemu-devel] [sparc] Floating point exception issue

[Qemu-devel] [sparc] Floating point exception issue

[Mateusz Loskot]

Hi,

Recently, I have reported mysterious issues on NetBSD 5.1
emulated on SPARC. The whole first thread is here:

http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html

I decided to investigate the problem deeper and with great help
from NetBSD folks, I managed to find reproducible test case.
Initially, it was AWK command:

# echo NaN | awk '{print "test"}'
awk: floating point exception 8
   source line number 1

and next it boiled down to simple C program (see below).
Details of the investigation are archived in the NetBSD Problem
Report #44389 here:

http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389


Here is final version of the test program which reproduces the problem:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <errno.h>

int is_number(const char *s)
{
         double r;
         char *ep;
         errno = 0;
         r = strtod(s, &ep);
         if (r == HUGE_VAL)
                 printf("X:%g\n", r);

         if (ep == s || r == HUGE_VAL || errno == ERANGE)
                 return 0;
         while (*ep == ' ' || *ep == '\t' || *ep == '\n')
                 ep++;
         if (*ep == '\0')
                 return 1;
         else
                 return 0;
}

int main(int argc, char **argv)
{
         double v;

         if (is_number("NaN")) {
                 printf("is a number\n");
                 v = atof("NaN");
         } else {
                 printf("not a number\n");
                 v = 0.0;
         }
         printf("%.4f\n", v);

         return 0;
}


On NetBSD/SPARC, the program receives SIGFPE:

$ gcc ./nan_test_2.c
  $ ./a.out
  [1]   Floating point exception (core dumped) ./a.out

Specifically, it's caused by r == HUGE_VAL condition in
   if (ep == s || r == HUGE_VAL || errno == ERANGE)
where r is NaN.

All the signs indicate there is a bug in QEMU.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org

Re: [Qemu-devel] [sparc] Floating point exception issue

[Blue Swirl]

On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot <mateusz@loskot.net> wrote:
> Hi,
>
> Recently, I have reported mysterious issues on NetBSD 5.1
> emulated on SPARC. The whole first thread is here:
>
> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>
> I decided to investigate the problem deeper and with great help
> from NetBSD folks, I managed to find reproducible test case.
> Initially, it was AWK command:
>
> # echo NaN | awk '{print "test"}'
> awk: floating point exception 8
>  source line number 1
>
> and next it boiled down to simple C program (see below).
> Details of the investigation are archived in the NetBSD Problem
> Report #44389 here:
>
> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>
>
> Here is final version of the test program which reproduces the problem:
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <math.h>
> #include <errno.h>
>
> int is_number(const char *s)
> {
>        double r;
>        char *ep;
>        errno = 0;
>        r = strtod(s, &ep);
>        if (r == HUGE_VAL)
>                printf("X:%g\n", r);
>
>        if (ep == s || r == HUGE_VAL || errno == ERANGE)
>                return 0;
>        while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>                ep++;
>        if (*ep == '\0')
>                return 1;
>        else
>                return 0;
> }
>
> int main(int argc, char **argv)
> {
>        double v;
>
>        if (is_number("NaN")) {
>                printf("is a number\n");
>                v = atof("NaN");
>        } else {
>                printf("not a number\n");
>                v = 0.0;
>        }
>        printf("%.4f\n", v);
>
>        return 0;
> }
>
>
> On NetBSD/SPARC, the program receives SIGFPE:
>
> $ gcc ./nan_test_2.c
>  $ ./a.out
>  [1]   Floating point exception (core dumped) ./a.out
>
> Specifically, it's caused by r == HUGE_VAL condition in
>  if (ep == s || r == HUGE_VAL || errno == ERANGE)
> where r is NaN.
>
> All the signs indicate there is a bug in QEMU.

I'll install 5.1, but on 4.0 which I had installed, the program works fine:
$ ./sigfpe
is a number
nan

Re: [Qemu-devel] [sparc] Floating point exception issue

[Mateusz Loskot]

On 18/01/11 17:36, Blue Swirl wrote:
> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>  wrote:
>> Hi,
>>
>> Recently, I have reported mysterious issues on NetBSD 5.1
>> emulated on SPARC. The whole first thread is here:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>
>> I decided to investigate the problem deeper and with great help
>> from NetBSD folks, I managed to find reproducible test case.
>> Initially, it was AWK command:
>>
>> # echo NaN | awk '{print "test"}'
>> awk: floating point exception 8
>>   source line number 1
>>
>> and next it boiled down to simple C program (see below).
>> Details of the investigation are archived in the NetBSD Problem
>> Report #44389 here:
>>
>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>
>>
>> Here is final version of the test program which reproduces the problem:
>>
>> #include<stdio.h>
>> #include<stdlib.h>
>> #include<math.h>
>> #include<errno.h>
>>
>> int is_number(const char *s)
>> {
>>         double r;
>>         char *ep;
>>         errno = 0;
>>         r = strtod(s,&ep);
>>         if (r == HUGE_VAL)
>>                 printf("X:%g\n", r);
>>
>>         if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>                 return 0;
>>         while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>                 ep++;
>>         if (*ep == '\0')
>>                 return 1;
>>         else
>>                 return 0;
>> }
>>
>> int main(int argc, char **argv)
>> {
>>         double v;
>>
>>         if (is_number("NaN")) {
>>                 printf("is a number\n");
>>                 v = atof("NaN");
>>         } else {
>>                 printf("not a number\n");
>>                 v = 0.0;
>>         }
>>         printf("%.4f\n", v);
>>
>>         return 0;
>> }
>>
>>
>> On NetBSD/SPARC, the program receives SIGFPE:
>>
>> $ gcc ./nan_test_2.c
>>   $ ./a.out
>>   [1]   Floating point exception (core dumped) ./a.out
>>
>> Specifically, it's caused by r == HUGE_VAL condition in
>>   if (ep == s || r == HUGE_VAL || errno == ERANGE)
>> where r is NaN.
>>
>> All the signs indicate there is a bug in QEMU.
>
> I'll install 5.1, but on 4.0 which I had installed, the program works fine:
> $ ./sigfpe
> is a number
> nan

I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use 
with NetBSD 5.1/SPARC) and it works well indeed:

mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
is a number
nan
mloskot@qemu-netbsd-50-sparc:~/tmp#

Hmm, this is becoming interesting.

I run QEMU 0.13 on Windows Vista (64-bit).
Perhaps host system and QEMU binaries are relevant here.
I will try on Linux host system later tonight.

BTW, here are my images:

http://mateusz.loskot.net/tmp/qemu/

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org

Re: [Qemu-devel] [sparc] Floating point exception issue

[Blue Swirl]

On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot <mateusz@loskot.net> wrote:
> On 18/01/11 17:36, Blue Swirl wrote:
>>
>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>  wrote:
>>>
>>> Hi,
>>>
>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>> emulated on SPARC. The whole first thread is here:
>>>
>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>
>>> I decided to investigate the problem deeper and with great help
>>> from NetBSD folks, I managed to find reproducible test case.
>>> Initially, it was AWK command:
>>>
>>> # echo NaN | awk '{print "test"}'
>>> awk: floating point exception 8
>>>  source line number 1
>>>
>>> and next it boiled down to simple C program (see below).
>>> Details of the investigation are archived in the NetBSD Problem
>>> Report #44389 here:
>>>
>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>
>>>
>>> Here is final version of the test program which reproduces the problem:
>>>
>>> #include<stdio.h>
>>> #include<stdlib.h>
>>> #include<math.h>
>>> #include<errno.h>
>>>
>>> int is_number(const char *s)
>>> {
>>>        double r;
>>>        char *ep;
>>>        errno = 0;
>>>        r = strtod(s,&ep);
>>>        if (r == HUGE_VAL)
>>>                printf("X:%g\n", r);
>>>
>>>        if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>                return 0;
>>>        while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>                ep++;
>>>        if (*ep == '\0')
>>>                return 1;
>>>        else
>>>                return 0;
>>> }
>>>
>>> int main(int argc, char **argv)
>>> {
>>>        double v;
>>>
>>>        if (is_number("NaN")) {
>>>                printf("is a number\n");
>>>                v = atof("NaN");
>>>        } else {
>>>                printf("not a number\n");
>>>                v = 0.0;
>>>        }
>>>        printf("%.4f\n", v);
>>>
>>>        return 0;
>>> }
>>>
>>>
>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>
>>> $ gcc ./nan_test_2.c
>>>  $ ./a.out
>>>  [1]   Floating point exception (core dumped) ./a.out
>>>
>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>  if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>> where r is NaN.
>>>
>>> All the signs indicate there is a bug in QEMU.
>>
>> I'll install 5.1, but on 4.0 which I had installed, the program works
>> fine:
>> $ ./sigfpe
>> is a number
>> nan
>
> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use with
> NetBSD 5.1/SPARC) and it works well indeed:
>
> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
> is a number
> nan
> mloskot@qemu-netbsd-50-sparc:~/tmp#
>
> Hmm, this is becoming interesting.
>
> I run QEMU 0.13 on Windows Vista (64-bit).
> Perhaps host system and QEMU binaries are relevant here.
> I will try on Linux host system later tonight.
>
> BTW, here are my images:
>
> http://mateusz.loskot.net/tmp/qemu/

The problem was with NaN handling in fcmped instruction. I've
committed a patch that fixes the problem, please test. Thanks for
reporting and the test case.

Re: [Qemu-devel] [sparc] Floating point exception issue

[Mateusz Loskot]

On 18/01/11 21:51, Blue Swirl wrote:
> On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot<mateusz@loskot.net>  wrote:
>> On 18/01/11 17:36, Blue Swirl wrote:
>>>
>>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>>   wrote:
>>>>
>>>> Hi,
>>>>
>>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>>> emulated on SPARC. The whole first thread is here:
>>>>
>>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>>
>>>> I decided to investigate the problem deeper and with great help
>>>> from NetBSD folks, I managed to find reproducible test case.
>>>> Initially, it was AWK command:
>>>>
>>>> # echo NaN | awk '{print "test"}'
>>>> awk: floating point exception 8
>>>>   source line number 1
>>>>
>>>> and next it boiled down to simple C program (see below).
>>>> Details of the investigation are archived in the NetBSD Problem
>>>> Report #44389 here:
>>>>
>>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>>
>>>>
>>>> Here is final version of the test program which reproduces the problem:
>>>>
>>>> #include<stdio.h>
>>>> #include<stdlib.h>
>>>> #include<math.h>
>>>> #include<errno.h>
>>>>
>>>> int is_number(const char *s)
>>>> {
>>>>         double r;
>>>>         char *ep;
>>>>         errno = 0;
>>>>         r = strtod(s,&ep);
>>>>         if (r == HUGE_VAL)
>>>>                 printf("X:%g\n", r);
>>>>
>>>>         if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>                 return 0;
>>>>         while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>>                 ep++;
>>>>         if (*ep == '\0')
>>>>                 return 1;
>>>>         else
>>>>                 return 0;
>>>> }
>>>>
>>>> int main(int argc, char **argv)
>>>> {
>>>>         double v;
>>>>
>>>>         if (is_number("NaN")) {
>>>>                 printf("is a number\n");
>>>>                 v = atof("NaN");
>>>>         } else {
>>>>                 printf("not a number\n");
>>>>                 v = 0.0;
>>>>         }
>>>>         printf("%.4f\n", v);
>>>>
>>>>         return 0;
>>>> }
>>>>
>>>>
>>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>>
>>>> $ gcc ./nan_test_2.c
>>>>   $ ./a.out
>>>>   [1]   Floating point exception (core dumped) ./a.out
>>>>
>>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>>   if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>> where r is NaN.
>>>>
>>>> All the signs indicate there is a bug in QEMU.
>>>
>>> I'll install 5.1, but on 4.0 which I had installed, the program works
>>> fine:
>>> $ ./sigfpe
>>> is a number
>>> nan
>>
>> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use with
>> NetBSD 5.1/SPARC) and it works well indeed:
>>
>> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
>> is a number
>> nan
>> mloskot@qemu-netbsd-50-sparc:~/tmp#
>>
>> Hmm, this is becoming interesting.
>>
>> I run QEMU 0.13 on Windows Vista (64-bit).
>> Perhaps host system and QEMU binaries are relevant here.
>> I will try on Linux host system later tonight.
>>
>> BTW, here are my images:
>>
>> http://mateusz.loskot.net/tmp/qemu/
>
> The problem was with NaN handling in fcmped instruction. I've
> committed a patch that fixes the problem, please test.

I'm having problems with building qemu under MinGW, so I will need to 
wait for someone to update binaries.

Stefan, are you planning to update your binaries?
I would be grateful.

> Thanks for reporting and the test case.

Thanks for fixing!

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org

Re: [Qemu-devel] [sparc] Floating point exception issue

[Mateusz Loskot]

On 18/01/11 21:51, Blue Swirl wrote:
> On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot <mateusz@loskot.net> wrote:
>> On 18/01/11 17:36, Blue Swirl wrote:
>>>
>>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>>  wrote:
>>>>
>>>> Hi,
>>>>
>>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>>> emulated on SPARC. The whole first thread is here:
>>>>
>>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>>
>>>> I decided to investigate the problem deeper and with great help
>>>> from NetBSD folks, I managed to find reproducible test case.
>>>> Initially, it was AWK command:
>>>>
>>>> # echo NaN | awk '{print "test"}'
>>>> awk: floating point exception 8
>>>>  source line number 1
>>>>
>>>> and next it boiled down to simple C program (see below).
>>>> Details of the investigation are archived in the NetBSD Problem
>>>> Report #44389 here:
>>>>
>>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>>
>>>>
>>>> Here is final version of the test program which reproduces the problem:
>>>>
>>>> #include<stdio.h>
>>>> #include<stdlib.h>
>>>> #include<math.h>
>>>> #include<errno.h>
>>>>
>>>> int is_number(const char *s)
>>>> {
>>>>        double r;
>>>>        char *ep;
>>>>        errno = 0;
>>>>        r = strtod(s,&ep);
>>>>        if (r == HUGE_VAL)
>>>>                printf("X:%g\n", r);
>>>>
>>>>        if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>                return 0;
>>>>        while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>>                ep++;
>>>>        if (*ep == '\0')
>>>>                return 1;
>>>>        else
>>>>                return 0;
>>>> }
>>>>
>>>> int main(int argc, char **argv)
>>>> {
>>>>        double v;
>>>>
>>>>        if (is_number("NaN")) {
>>>>                printf("is a number\n");
>>>>                v = atof("NaN");
>>>>        } else {
>>>>                printf("not a number\n");
>>>>                v = 0.0;
>>>>        }
>>>>        printf("%.4f\n", v);
>>>>
>>>>        return 0;
>>>> }
>>>>
>>>>
>>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>>
>>>> $ gcc ./nan_test_2.c
>>>>  $ ./a.out
>>>>  [1]   Floating point exception (core dumped) ./a.out
>>>>
>>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>>  if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>> where r is NaN.
>>>>
>>>> All the signs indicate there is a bug in QEMU.
>>>
>>> I'll install 5.1, but on 4.0 which I had installed, the program works
>>> fine:
>>> $ ./sigfpe
>>> is a number
>>> nan
>>
>> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use with
>> NetBSD 5.1/SPARC) and it works well indeed:
>>
>> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
>> is a number
>> nan
>> mloskot@qemu-netbsd-50-sparc:~/tmp#
>>
>> Hmm, this is becoming interesting.
>>
>> I run QEMU 0.13 on Windows Vista (64-bit).
>> Perhaps host system and QEMU binaries are relevant here.
>> I will try on Linux host system later tonight.
>>
>> BTW, here are my images:
>>
>> http://mateusz.loskot.net/tmp/qemu/
> 
> The problem was with NaN handling in fcmped instruction. I've
> committed a patch that fixes the problem, please test. Thanks for
> reporting and the test case.

FYI, this problem seems to be occurring in qemu on Windows only.
I tested git version dated before you applied the fix
and built on Linux and the problem does not happening there.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org

Re: [Qemu-devel] [sparc] Floating point exception issue

[Blue Swirl]

On Sat, Jan 22, 2011 at 3:30 PM, Mateusz Loskot <mateusz@loskot.net> wrote:
> On 18/01/11 21:51, Blue Swirl wrote:
>> On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot <mateusz@loskot.net> wrote:
>>> On 18/01/11 17:36, Blue Swirl wrote:
>>>>
>>>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>>>  wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>>>> emulated on SPARC. The whole first thread is here:
>>>>>
>>>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>>>
>>>>> I decided to investigate the problem deeper and with great help
>>>>> from NetBSD folks, I managed to find reproducible test case.
>>>>> Initially, it was AWK command:
>>>>>
>>>>> # echo NaN | awk '{print "test"}'
>>>>> awk: floating point exception 8
>>>>>  source line number 1
>>>>>
>>>>> and next it boiled down to simple C program (see below).
>>>>> Details of the investigation are archived in the NetBSD Problem
>>>>> Report #44389 here:
>>>>>
>>>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>>>
>>>>>
>>>>> Here is final version of the test program which reproduces the problem:
>>>>>
>>>>> #include<stdio.h>
>>>>> #include<stdlib.h>
>>>>> #include<math.h>
>>>>> #include<errno.h>
>>>>>
>>>>> int is_number(const char *s)
>>>>> {
>>>>>        double r;
>>>>>        char *ep;
>>>>>        errno = 0;
>>>>>        r = strtod(s,&ep);
>>>>>        if (r == HUGE_VAL)
>>>>>                printf("X:%g\n", r);
>>>>>
>>>>>        if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>>                return 0;
>>>>>        while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>>>                ep++;
>>>>>        if (*ep == '\0')
>>>>>                return 1;
>>>>>        else
>>>>>                return 0;
>>>>> }
>>>>>
>>>>> int main(int argc, char **argv)
>>>>> {
>>>>>        double v;
>>>>>
>>>>>        if (is_number("NaN")) {
>>>>>                printf("is a number\n");
>>>>>                v = atof("NaN");
>>>>>        } else {
>>>>>                printf("not a number\n");
>>>>>                v = 0.0;
>>>>>        }
>>>>>        printf("%.4f\n", v);
>>>>>
>>>>>        return 0;
>>>>> }
>>>>>
>>>>>
>>>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>>>
>>>>> $ gcc ./nan_test_2.c
>>>>>  $ ./a.out
>>>>>  [1]   Floating point exception (core dumped) ./a.out
>>>>>
>>>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>>>  if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>> where r is NaN.
>>>>>
>>>>> All the signs indicate there is a bug in QEMU.
>>>>
>>>> I'll install 5.1, but on 4.0 which I had installed, the program works
>>>> fine:
>>>> $ ./sigfpe
>>>> is a number
>>>> nan
>>>
>>> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use with
>>> NetBSD 5.1/SPARC) and it works well indeed:
>>>
>>> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
>>> is a number
>>> nan
>>> mloskot@qemu-netbsd-50-sparc:~/tmp#
>>>
>>> Hmm, this is becoming interesting.
>>>
>>> I run QEMU 0.13 on Windows Vista (64-bit).
>>> Perhaps host system and QEMU binaries are relevant here.
>>> I will try on Linux host system later tonight.
>>>
>>> BTW, here are my images:
>>>
>>> http://mateusz.loskot.net/tmp/qemu/
>>
>> The problem was with NaN handling in fcmped instruction. I've
>> committed a patch that fixes the problem, please test. Thanks for
>> reporting and the test case.
>
> FYI, this problem seems to be occurring in qemu on Windows only.
> I tested git version dated before you applied the fix
> and built on Linux and the problem does not happening there.

No, it was generic problem. I could reproduce it with your test case
and with a small assembler program which only used fcmped using user
emulator.

Re: [Qemu-devel] [sparc] Floating point exception issue

[Robert Reif]

Blue Swirl wrote:
> On Sat, Jan 22, 2011 at 3:30 PM, Mateusz Loskot<mateusz@loskot.net>  wrote:
>    
>> On 18/01/11 21:51, Blue Swirl wrote:
>>      
>>> On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot<mateusz@loskot.net>  wrote:
>>>        
>>>> On 18/01/11 17:36, Blue Swirl wrote:
>>>>          
>>>>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>>>>   wrote:
>>>>>            
>>>>>> Hi,
>>>>>>
>>>>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>>>>> emulated on SPARC. The whole first thread is here:
>>>>>>
>>>>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>>>>
>>>>>> I decided to investigate the problem deeper and with great help
>>>>>> from NetBSD folks, I managed to find reproducible test case.
>>>>>> Initially, it was AWK command:
>>>>>>
>>>>>> # echo NaN | awk '{print "test"}'
>>>>>> awk: floating point exception 8
>>>>>>   source line number 1
>>>>>>
>>>>>> and next it boiled down to simple C program (see below).
>>>>>> Details of the investigation are archived in the NetBSD Problem
>>>>>> Report #44389 here:
>>>>>>
>>>>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>>>>
>>>>>>
>>>>>> Here is final version of the test program which reproduces the problem:
>>>>>>
>>>>>> #include<stdio.h>
>>>>>> #include<stdlib.h>
>>>>>> #include<math.h>
>>>>>> #include<errno.h>
>>>>>>
>>>>>> int is_number(const char *s)
>>>>>> {
>>>>>>         double r;
>>>>>>         char *ep;
>>>>>>         errno = 0;
>>>>>>         r = strtod(s,&ep);
>>>>>>         if (r == HUGE_VAL)
>>>>>>                 printf("X:%g\n", r);
>>>>>>
>>>>>>         if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>>>                 return 0;
>>>>>>         while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>>>>                 ep++;
>>>>>>         if (*ep == '\0')
>>>>>>                 return 1;
>>>>>>         else
>>>>>>                 return 0;
>>>>>> }
>>>>>>
>>>>>> int main(int argc, char **argv)
>>>>>> {
>>>>>>         double v;
>>>>>>
>>>>>>         if (is_number("NaN")) {
>>>>>>                 printf("is a number\n");
>>>>>>                 v = atof("NaN");
>>>>>>         } else {
>>>>>>                 printf("not a number\n");
>>>>>>                 v = 0.0;
>>>>>>         }
>>>>>>         printf("%.4f\n", v);
>>>>>>
>>>>>>         return 0;
>>>>>> }
>>>>>>
>>>>>>
>>>>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>>>>
>>>>>> $ gcc ./nan_test_2.c
>>>>>>   $ ./a.out
>>>>>>   [1]   Floating point exception (core dumped) ./a.out
>>>>>>
>>>>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>>>>   if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>>> where r is NaN.
>>>>>>
>>>>>> All the signs indicate there is a bug in QEMU.
>>>>>>              
>>>>> I'll install 5.1, but on 4.0 which I had installed, the program works
>>>>> fine:
>>>>> $ ./sigfpe
>>>>> is a number
>>>>> nan
>>>>>            
>>>> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use with
>>>> NetBSD 5.1/SPARC) and it works well indeed:
>>>>
>>>> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
>>>> is a number
>>>> nan
>>>> mloskot@qemu-netbsd-50-sparc:~/tmp#
>>>>
>>>> Hmm, this is becoming interesting.
>>>>
>>>> I run QEMU 0.13 on Windows Vista (64-bit).
>>>> Perhaps host system and QEMU binaries are relevant here.
>>>> I will try on Linux host system later tonight.
>>>>
>>>> BTW, here are my images:
>>>>
>>>> http://mateusz.loskot.net/tmp/qemu/
>>>>          
>>> The problem was with NaN handling in fcmped instruction. I've
>>> committed a patch that fixes the problem, please test. Thanks for
>>> reporting and the test case.
>>>        
>> FYI, this problem seems to be occurring in qemu on Windows only.
>> I tested git version dated before you applied the fix
>> and built on Linux and the problem does not happening there.
>>      
> No, it was generic problem. I could reproduce it with your test case
> and with a small assembler program which only used fcmped using user
> emulator.
>
>
>    
There is still a floating point exception problem that may or may not be 
related.

Booting an ss5-170 with a real sun ROM image still fails FP tests:

4.1.1  fpu    reg          regfile                  Pass
4.1.2  fpu    reg          misalign                 Pass
4.1.3  fpu    reg          single precision         Pass
4.1.4  fpu    reg          double precision         Pass
4.2.1  fpu    exceptions   single precision         Failed
Exception Didn't Block Store : 0 : exp= 00000000, obs= FFFFFFFF
4.2.2  fpu    exceptions   double precision         Failed
Exception Didn't Block Store : 0 : exp= 00000000, obs= FFFFFFFF

Re: [Qemu-devel] [sparc] Floating point exception issue

[Artyom Tarasenko]

On Sat, Jan 22, 2011 at 5:45 PM, Robert Reif <reif@earthlink.net> wrote:
> Blue Swirl wrote:
>>
>> On Sat, Jan 22, 2011 at 3:30 PM, Mateusz Loskot<mateusz@loskot.net>
>>  wrote:
>>
>>>
>>> On 18/01/11 21:51, Blue Swirl wrote:
>>>
>>>>
>>>> On Tue, Jan 18, 2011 at 6:00 PM, Mateusz Loskot<mateusz@loskot.net>
>>>>  wrote:
>>>>
>>>>>
>>>>> On 18/01/11 17:36, Blue Swirl wrote:
>>>>>
>>>>>>
>>>>>> On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mateusz@loskot.net>
>>>>>>  wrote:
>>>>>>
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Recently, I have reported mysterious issues on NetBSD 5.1
>>>>>>> emulated on SPARC. The whole first thread is here:
>>>>>>>
>>>>>>> http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
>>>>>>>
>>>>>>> I decided to investigate the problem deeper and with great help
>>>>>>> from NetBSD folks, I managed to find reproducible test case.
>>>>>>> Initially, it was AWK command:
>>>>>>>
>>>>>>> # echo NaN | awk '{print "test"}'
>>>>>>> awk: floating point exception 8
>>>>>>>  source line number 1
>>>>>>>
>>>>>>> and next it boiled down to simple C program (see below).
>>>>>>> Details of the investigation are archived in the NetBSD Problem
>>>>>>> Report #44389 here:
>>>>>>>
>>>>>>> http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
>>>>>>>
>>>>>>>
>>>>>>> Here is final version of the test program which reproduces the
>>>>>>> problem:
>>>>>>>
>>>>>>> #include<stdio.h>
>>>>>>> #include<stdlib.h>
>>>>>>> #include<math.h>
>>>>>>> #include<errno.h>
>>>>>>>
>>>>>>> int is_number(const char *s)
>>>>>>> {
>>>>>>>        double r;
>>>>>>>        char *ep;
>>>>>>>        errno = 0;
>>>>>>>        r = strtod(s,&ep);
>>>>>>>        if (r == HUGE_VAL)
>>>>>>>                printf("X:%g\n", r);
>>>>>>>
>>>>>>>        if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>>>>                return 0;
>>>>>>>        while (*ep == ' ' || *ep == '\t' || *ep == '\n')
>>>>>>>                ep++;
>>>>>>>        if (*ep == '\0')
>>>>>>>                return 1;
>>>>>>>        else
>>>>>>>                return 0;
>>>>>>> }
>>>>>>>
>>>>>>> int main(int argc, char **argv)
>>>>>>> {
>>>>>>>        double v;
>>>>>>>
>>>>>>>        if (is_number("NaN")) {
>>>>>>>                printf("is a number\n");
>>>>>>>                v = atof("NaN");
>>>>>>>        } else {
>>>>>>>                printf("not a number\n");
>>>>>>>                v = 0.0;
>>>>>>>        }
>>>>>>>        printf("%.4f\n", v);
>>>>>>>
>>>>>>>        return 0;
>>>>>>> }
>>>>>>>
>>>>>>>
>>>>>>> On NetBSD/SPARC, the program receives SIGFPE:
>>>>>>>
>>>>>>> $ gcc ./nan_test_2.c
>>>>>>>  $ ./a.out
>>>>>>>  [1]   Floating point exception (core dumped) ./a.out
>>>>>>>
>>>>>>> Specifically, it's caused by r == HUGE_VAL condition in
>>>>>>>  if (ep == s || r == HUGE_VAL || errno == ERANGE)
>>>>>>> where r is NaN.
>>>>>>>
>>>>>>> All the signs indicate there is a bug in QEMU.
>>>>>>>
>>>>>>
>>>>>> I'll install 5.1, but on 4.0 which I had installed, the program works
>>>>>> fine:
>>>>>> $ ./sigfpe
>>>>>> is a number
>>>>>> nan
>>>>>>
>>>>>
>>>>> I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use
>>>>> with
>>>>> NetBSD 5.1/SPARC) and it works well indeed:
>>>>>
>>>>> mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
>>>>> is a number
>>>>> nan
>>>>> mloskot@qemu-netbsd-50-sparc:~/tmp#
>>>>>
>>>>> Hmm, this is becoming interesting.
>>>>>
>>>>> I run QEMU 0.13 on Windows Vista (64-bit).
>>>>> Perhaps host system and QEMU binaries are relevant here.
>>>>> I will try on Linux host system later tonight.
>>>>>
>>>>> BTW, here are my images:
>>>>>
>>>>> http://mateusz.loskot.net/tmp/qemu/
>>>>>
>>>>
>>>> The problem was with NaN handling in fcmped instruction. I've
>>>> committed a patch that fixes the problem, please test. Thanks for
>>>> reporting and the test case.
>>>>
>>>
>>> FYI, this problem seems to be occurring in qemu on Windows only.
>>> I tested git version dated before you applied the fix
>>> and built on Linux and the problem does not happening there.
>>>
>>
>> No, it was generic problem. I could reproduce it with your test case
>> and with a small assembler program which only used fcmped using user
>> emulator.
>>
>>
>>
>
> There is still a floating point exception problem that may or may not be
> related.

AFAICS they are not related. Strictly speaking they are not FP
problems but deferred trap processing problems.

> Booting an ss5-170 with a real sun ROM image still fails FP tests:
>
> 4.1.1  fpu    reg          regfile                  Pass
> 4.1.2  fpu    reg          misalign                 Pass
> 4.1.3  fpu    reg          single precision         Pass
> 4.1.4  fpu    reg          double precision         Pass
> 4.2.1  fpu    exceptions   single precision         Failed
> Exception Didn't Block Store : 0 : exp= 00000000, obs= FFFFFFFF
> 4.2.2  fpu    exceptions   double precision         Failed
> Exception Didn't Block Store : 0 : exp= 00000000, obs= FFFFFFFF
>
>
>



-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/