[U-Boot] merge arm64 to arm

[Tom Rini <trini@ti.com>]

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On 08/19/2013 01:33 PM, M?ns Rullg?rd wrote:
> Scott Wood <scottwood@freescale.com> writes:
[snip]
>> i960 is a bad analogy.  It's often possible to turn arm32 asm
>> into arm64 asm with some search and replace and minor manual
>> fixups.
> 
> Only if the original uses none of the distinguishing features of
> ARM like predicated instructions or variably shifted operands.
> Once you limit yourself to the remaining basic operations, every
> (RISC) architecture looks the same.
[snip]
> AArch64 of course shares certain non-ISA aspects with AArch32.
> Page table formats and other architecturally defined system control
> features are the same, and code for managing these things should of
> course be shared.  Some other features, e.g. exception handling,
> are different enough that sharing code is probably difficult.
> 
> There is a tendency to see arm64/aarch64 as yet another 64-bit
> extension of a 32-bit architecture, which it is not.  Assuming that
> software support will or can follow the model used by the others
> mentioned is thus a mistake.

We don't have lots of hand-crafted assembly, and what we do, we
largely have split out already into the cpu directories.  I really
think we just need to try this and see how it goes.

- -- 
Tom
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