Adding a MACHINE_ARCH note

[Nathan Whitehorn]

On 07/12/13 18:02, Adrian Chadd wrote:
> On 12 July 2013 13:48, Kurt Lidl <lidl at pix.net> wrote:
>>> It seems to be driven by Intel and Google.  The idea is that for some
>>> applications (or maybe even most :), an ILP32 model will perform better.
>>
>> I believe that Google's NaCl (native client) plugins for Chrome all use
>> the "x32" ABI.  The NaCl stuff uses this, along with a "safe" code
>> generation path to implement part of the sandboxing for Chrome plugins.
>>
>> Ultimately, to have a fully functioning Chrome (with plugins) on amd64
>> hosts, we'll want to support "x32".
> Does this mean that netbooks with only 32 bit CPUs in them won't support NaCl?
> (Ie, they're only ever going to generate x32 code, and even 32 bit
> machines will still run 64 bit assembly..)
>

As I remember, they are trying to have a constant ABI (32-bit pointers, 
little endian) irrespective of the actual architecture to make things 
really just a recompile. Basically, it's meant to be something where 
sizeof(everything) is the same both on x86 and little-endian ARM. So 
this means there is 32-bit x86 and x32, but not amd64.
-Nathan