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From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.arch
Subject: Re: MIPS 64x32 Divide?
Summary: 32/16 may serve
Message-ID: <3111@goanna.cs.rmit.oz.au>
Date: 30 May 90 17:58:59 GMT
References: <9462@pt.cs.cmu.edu>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 18

In article <9462@pt.cs.cmu.edu>, chiles@chiles.slisp.cs.cmu.edu (Bill Chiles) writes:
> This is a general query of how to do 64-bit by 32-bit division when a
> machine only gives you a 32-bit by 32-bit instruction.  [...]
> Some languages and number packages do support [bignums] and require a
> 64x32 divide for completeness, even if profiling dictates that it isn't
> worth providing such an instruction.

If you want to implement bignums, you can treat a bitstring as a sequence
of 16-bit "bigits" just as easily as you can treat it as 32-bit "bigits".
In fact, you can do your addition and subtraction in 32-bit chunks and
your division in 16-bit chunks.  All you need, then, is 32-bit/16-bit,
and the existing 32-bit/32-bit will give you that.  Isn't code for a
double-precision division in Knuth vol 2?

A certain popular RISC hasn't _any_ division instruction...
-- 
"A 7th class of programs, correct in every way, is believed to exist by a
few computer scientists.  However, no example could be found to include here."