[Haskell-cafe] OSX i386/x86 and x86_64 - time to switch supported platforms?

John Lato jwlato at gmail.com
Fri Feb 4 12:53:13 CET 2011

> From: Max Bolingbroke <batterseapower at hotmail.com>
> On 4 February 2011 02:35, Steve Severance <steve at medwizard.net> wrote:
> > Wholly support moving OSX to x64. x86 should be supported only on a
> > best effort basis for legacy.
> Moving from x86 to x64 has advantages and disadvantages from my POV.
> Advantages:
>  * Able to address more memory
>  * More registers for code generation
>  * Haskell dependencies wouldn't need to be built for x86 on Snow
> Leopard (though if we swapped to x64 on Leopard as well, the Leopard
> users would start having to build 64-bit libraries specially)
> Disadvantages:
>  * Pointers become wider, and Haskell data structures mostly consist
> of pointers. This will bloat memory use of Haskell programs.
>  * Generated binaries won't work on older Macs that don't have a
> 64-bit OS/CPU. This is important if you are distributing compiled
> Haskell binaries, which is not something I personally do but which is
> probably important to support
> Did I miss anything?

I'm moderately in favor of making the primary supported platform x86_64,
except for the distribution issue.  If i386 were maintained but not
necessarily targeted for improvement that would be fine by me.

> I don't know if anyone using a 64-bits GHC on e.g. Linux has reported
> experience of whether moving to 64-bits is a net win or not from a
> performance perspective. My guess is that it is a win for certain
> classes of programs (numerically intensive, "high performance
> Haskell"), and a loss for programs making extensive use of laziness,
> boxed data structures etc.

For my code, x86_64 (OS X) is a net win.  It's sometimes significantly
faster, and hasn't ever been noticeably slower. The biggest gains seems to
be I/O, although I haven't really investigated this.

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