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32- and 64-bit performance
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Date: -- (:)
From: David Brown <caml@d...>
Subject: Re: [Caml-list] Re: 32- and 64-bit performance
On Sat, 02 Apr 2005 15:23:21 -0500, Stefan Monnier  
<monnier@iro.umontreal.ca> wrote:

> Under Alpha they called it "taso".  Mostly used for compatibility with  
> apps
> that were assuming the size of ptrs is the same as the size of int: it  
> just
> made the C library use only the bottom 4GB of the address space such that
> the compiler could use only 32bit to store pointer values.

The default mode in gcc for amd64 is almost this (-mcmodel=small).  It  
assumes pointers live in the lower 2GB of address space, but 'sizeof (void  
*)' is still 8.  I'm not sure why the small model doesn't use 32-bit  
pointers.

The -mcmodel=medium model does 64-bit operations on pointers, but the code  
must still live in the lower 2GB of address space.

The -mcmodel=large isn't yet implemented.

Dave