generation of divxu opcode

[Andrew Haley]

Kai Henningsen writes:
 > aph@cambridge.redhat.com (Andrew Haley)  wrote on 08.07.02 in <15657.29301.560459.253061@cuddles.cambridge.redhat.com>:
 > 
 > > Kai Henningsen writes:
 > >  > aph@cambridge.redhat.com (Andrew Haley)  wrote on 05.07.02 in
 > >  > <15653.38739.706764.135879@cuddles.cambridge.redhat.com>:
 > >  >
 > >  > Care to explain what you would consider "valid results" in the
 > >  > cases in question?
 > >
 > > Sure.  In the case of an overflow, it would be possible to specify
 > > that the result of the operation is equal to the 8-bit truncation of
 > > the correct result.  This wouldn't help for a true division by zero,
 > > but would leave all other results well-defined.
 > 
 > Are we arguing well-defined, valid, or useful here? That would certainly  
 > be well-defined, but I cannot see it particularly valid or useful.

Well, it would allow us to write a more general RTL template for the
full range of the instruction, which is an appropriate core primitive
for classical long division -- for example Kunth 4.3.1, Algorithm D.

Andrew.