Re: 64 bit codes

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Mok-Kong Shen wrote on comp.lang.ada:
> I have some computations that would be much more efficient, if done
> with 64-bit arithmetics ("natively") than with 32-bit arithmetics
> and I don't like to take the trouble/"risk" of having a 2nd OS on my
> PC (I don't think currently to possess even the proper knowledge to
> do that at all).

I'm not sure what you mean exactly by "64-bit arithmetic".  If you
require 64-bit addresses, then yes you need a 64-bit compiler.  But if
you only need 64-bit floating point numbers, the 32-bit compiler can
provide them just fine.  In fact, on Intel hardware, Long_Floats are
normally 80 bits wide IIRC.  Similarly, I think Long_Long_Integer is
64 bits wide even with a 32-bit compiler.

> On the other hand, as outsider I surmise that providing a 64-bit
> Windows version doesn't involve much work, since there is already a
> 32-bit version. It's essentially just a replacement of the included
> gcc from the 32-bit version to the 64-bit version, isn't it?

No, there is more to it than that.  Given that most of GNAT is written
in Ada, one requires a 64-bit Ada compiler to produce the first 64-bit
Ada compiler; that's the classic catch-22 aka bootstrapping process.
In the case of GNAT, this problem is exacerbated by the requirement to
also bootstrap the run-time library.

I see that GNAT Pro[1] supports 64-bit Windows; this means that they
have completed the bootstrapping process already.  So, if AdaCore tell
you that the GPL 2011 Edition simply won't support 64-bit, and you are
impatient, and really need a 64-bit version of GNAT, you should ask
AdaCore to provide GNAT Pro to you.

[1] http://www.adacore.com/home/products/gnatpro/supported_platforms/

--
Ludovic Brenta.