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Re: [WWWDocs] Deprecate support for non-thumb ARM devices

On 25/02/16 13:32, Stefan Ring wrote:
> On Thu, Feb 25, 2016 at 10:20 AM, Richard Earnshaw (lists)
> <> wrote:
>> The point is to permit the compiler to use interworking compatible
>> sequences of code when generating ARM code, not to force users to use
>> Thumb code.  The necessary instruction (BX) is available in armv5 and
>> armv5e, even though Thumb is not supported in those architecture variants.
>> It might be worth deprecating v5 and v5e at some point in the future: to
>> the best of my knowledge no v5 class device without Thumb has ever
>> existed - but it's not a decision that needs to be related to this proposal.
> Slightly off topic, but related: What does the "e" stand for? Also,
> what does "l" stand for in armv5tel, which is what I usually get --
> little endian?

The 'e' represented some extensions to the original v5 ISA (you can make
your own mind up as to what the 'e' stands for).

The 'l' isn't anything to do with the architecture per-se.  It simply
means in the Linux context a little-endian device, as opposed to a
'b'ig-endian device.  Most ARM based systems are little-endian so you'll
see that far more often than 'b'.

> I have no idea if there is an authoritative source for these host
> specifications and cannot find any. config.guess seems to just rely on
> uname -m.

For the AArch32 it's extremely ad-hoc.  There's a bit more sanity in the
AArch64 world, but it relies on people following some conventions and
not just creating anarchy.


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