Yes it would be quite useless to do a multiply by 0 on purpose. But i was thinking about cases where you have no control over the inputs values? I don't know. In any case, early termination was next on my list. However it requires supporting an arbritrary shift distance which will be on the critical path and maybe require quite a bit of hardware. We'll see how it turns out.
On Fri, August 31, 2007 10:42 pm, Paul Brook said: >> The other question is, is this even beneficial? I seem to recall that >> zeros occur quite commonly. Even in the MIPS ISA, r0 is just a >> hardwired zero because of this if i remember right... so that is my >> justification for doing this. > > I'd expect multiplication by zero to be relatively rare. One of the > advantages of a zero register is that some unary operations can be > implemented as a binary operation with a zero operand. e.g. x = -y can > be implemented as x = 0 - y without requiring an extra instruction. > > Early termination when the high bits are zero (ie. small values) would > be more useful. I've no idea how hard that is to achieve though. > > Paul > > _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
