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Date: Thu, 10 Jun 2004 13:31:14 -0700
From: David Daney <ddaney@avtrex.com>
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To: Andrew Haley <aph@redhat.com>
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Subject: Re: [RFC] MIPS division by zero and libgcj...
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Andrew Haley wrote:

>David Daney writes:
> > Andrew Haley wrote:
> > 
> > MIPS div instructions never trap.  However I think that GCC always emits 
> > things like this when it cannot determine that the divisor is non zero:
> > 
> >         div     $0,$17,$16
> >         bne     $16,$0,1f
> >         nop
> >         break   7
> > 1:
> >  
> > 
>
> > >No, there's no reason not to do it.  You'll have to write some hairy
> > >code to satisfy all the rules, though.
> > >
> > What are the rules?  Are they more complicated then throw an 
> > ArithmeticException when the divisor is zero?
>
>Yes.  You also have to do
>
>  if (dividend == (jint) 0x80000000L && divisor == -1)
>    return dividend;
>  
>and not throw an exception.
>
That is evidently what you have to do on i386.  MIPS gives the right 
answer without faulting (i.e. hitting the break 7).

David Daney.