Re: PATCH [0/3]: Simplify the kernel build by removing perl.

[Jamie Lokier <jamie@shareable.org>]

Rob Landley wrote:
> This doesn't _need_ bignum support.  It maxes out around 72 bits and
> the _result_ can't use more than about $SHIFT bits because you're
> dividing by the amount you shifted, so just chop off the bottom 32
> bits, do a normal 64 bit division on the top (it has to fit), and
> then do the same division on the appropriate shifted remainder, and
> combine the results.  This is easy because when the shift _is_ 32
> bits or more, the bottom 32 bits all have to be zeroes so you don't
> even have to mask and add, just shift the remainder left 32 bits so
> you can continue the divide.
> 
> Pulling out perl isn't always a good alternative to thinking about
> the problem.

Related query:

Does the Perl script being replaced use 64-bit arithmetic?  Because
many Perl installations only do 32-bit arithmetic.

If the Perl version works in 32-bit arithmetic, why does the shell
version not do the same thing?

-- Jamie