[racket] 80-bit precision in Racket

From: Hugh Myers (hsmyers at gmail.com)
Date: Fri Nov 9 11:51:57 EST 2012

As much as I love Racket, there are certainly times I miss 'C' and it's
ability to write code pretty much in assembler. As co-creator of the first
commercial fractal generation software (FracTools, FracInt was free not
commercial) I found the need to code down to the bare metal and a bit
beyond chasing yet more and more resolution :) </sigh> Now back to the
regular discussion...


On Fri, Nov 9, 2012 at 9:40 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:

> At Fri, 09 Nov 2012 19:34:00 +0400, Dmitry Pavlov wrote:
> > Matthew,
> >
> >  > Your plan sounds workable, but I wonder whether you'll want the JIT to
> > > unbox extnums in the same way that it unboxes flonums. That's not as
> > > easy as the rest of the plan, but generalizing Racket's unboxing
> > > machinery to deal with more types is something that we can consider.
> >
> > Surely we will need the JIT to unbox extnums. Could you please tell
> > why it is harder than the rest of the plan? Ten bytes worse than
> > eight? Alignment issues?
> Unboxing is a collaboration between the JIT and the bytecode compiler.
> There are various "value is known to be a flonum" flags that are
> threaded through the compiler, bytecode, validator, and JIT. In some of
> those places, there's room for an extra bit of information, but in
> other places, we'll have to adjust representations to make room for
> more bits.
> I'll look into this more. It would be nice to have fixnum unboxing, and
> maybe that would be a good experiment toward unboxing for other types
> as well.
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