Yahoo Groups archive
Thread
2005-12-31 by soren_t_hansen
What happenes if you make a division by zero on the LPC2132? I suspect that you enter the Undefined Instruction exception handler, but is that correct? I haven't been able to find anything about it in the manual. Best Regards Søren
2005-12-31 by Richard Duits
The ARM7TDMI does not have a divide instruction, so this is depending on the implementation of your compilers run time library. Richard. soren_t_hansen wrote:
> What happenes if you make a division by zero on the LPC2132? I suspect > that you enter the Undefined Instruction exception handler, but is > that correct? I haven't been able to find anything about it in the manual. > > Best Regards > S\ufffdren
2005-12-31 by Karl Olsen
---- Original Message ----
From: "soren_t_hansen" <soren_t_hansen@...> To: <lpc2000@yahoogroups.com> Sent: Saturday, December 31, 2005 12:12 PM Subject: [lpc2000] Divide by zero > What happenes if you make a division by zero on the LPC2132? I suspect > that you enter the Undefined Instruction exception handler, but is > that correct? I haven't been able to find anything about it in the > manual. No, the ARM7TDMI does not have a hardware divide instruction, so divisions are purely a software matter. With gcc, the compiler calls __divsi3 and __udivsi3 for signed and unsigned integer divisions, and they are implemented in libgcc, a part of gcc. If you try to divide by zero, they call __div0, and then return 0. The default implementation of __div0 does nothing. Other compilers might handle it differently. Karl Olsen
2005-12-31 by soren_t_hansen
--- In lpc2000@yahoogroups.com, "Karl Olsen" <kro@p...> wrote: > > ---- Original Message ---- > From: "soren_t_hansen" <soren_t_hansen@y...> > To: <lpc2000@yahoogroups.com> > Sent: Saturday, December 31, 2005 12:12 PM > Subject: [lpc2000] Divide by zero > > > What happenes if you make a division by zero on the LPC2132? I suspect > > that you enter the Undefined Instruction exception handler, but is > > that correct? I haven't been able to find anything about it in the > > manual. > > No, the ARM7TDMI does not have a hardware divide instruction, so divisions > are purely a software matter. > > With gcc, the compiler calls __divsi3 and __udivsi3 for signed and unsigned > integer divisions, and they are implemented in libgcc, a part of gcc. If > you try to divide by zero, they call __div0, and then return 0. The default > implementation of __div0 does nothing. > > Other compilers might handle it differently. > > Karl Olsen > I'm using the GNUARM toolchain. Does that mean that a divide by zero doesn't result in anything? /Søren
2005-12-31 by Karl Olsen
---- Original Message ----
From: "soren_t_hansen" <soren_t_hansen@...>
To: <lpc2000@yahoogroups.com>
Sent: Saturday, December 31, 2005 2:33 PM
Subject: [lpc2000] Re: Divide by zero
> --- In lpc2000@yahoogroups.com, "Karl Olsen" <kro@p...> wrote:
>>
>> ---- Original Message ----
>> From: "soren_t_hansen" <soren_t_hansen@y...>
>> To: <lpc2000@yahoogroups.com>
>> Sent: Saturday, December 31, 2005 12:12 PM
>> Subject: [lpc2000] Divide by zero
>>
>>> What happenes if you make a division by zero on the LPC2132? I
>>> suspect that you enter the Undefined Instruction exception handler,
>>> but is that correct? I haven't been able to find anything about it
>>> in the manual.
>>
>> No, the ARM7TDMI does not have a hardware divide instruction, so
>> divisions are purely a software matter.
>>
>> With gcc, the compiler calls __divsi3 and __udivsi3 for signed and
>> unsigned integer divisions, and they are implemented in libgcc, a
>> part of gcc. If you try to divide by zero, they call __div0, and then
>> return 0. The default implementation of __div0 does nothing.
>>
>> Other compilers might handle it differently.
>
> I'm using the GNUARM toolchain. Does that mean that a divide by zero
> doesn't result in anything?
Yes, the result is zero. If you want something more to happen, you can
provide your own __div0 function:
void __div0 (void)
{
printf ("Division by zero!\n");
}
Karl Olsen