[aarch64-port-dev ] Webrev of Oracle ARM & AARCH64 Sources

[Andrey Petushkov]

> On 29 Sep 2016, at 14:04, Andrew Haley <aph at redhat.com> wrote:
> 
> On 29/09/16 11:54, Andrey Petushkov wrote:
>> 
>>> On 29 Sep 2016, at 13:43, Andrew Haley <aph at redhat.com> wrote:
>>> 
>>> On 29/09/16 11:13, Andrey Petushkov wrote:
>>> 
>>>> In addition, aarch32 port shares much in common with RH’s aarch64
>>>> implementation so well, if you keep aarch64 in main openjdk repos
>>>> it’s much easier to merge aarch32 into it, rather than merge with
>>>> Sun/Oracle’s arm implementation.
>>> 
>>> There is no good technical reason for AArch64 to merge with AArch32,
>>> and IMO it would create a mess.  AArch64 is a clean-sheet design which
>>> shares some of its DNA with AArch32, but that is all.  It's not like
>>> x86-64, which is a 64-bit extension of x86.
>> 
>> Well, it’s AArch32 which is not clean-sheet design but rather
>> borrows from AArch64 :)
> 
> I meant to say: the AArch64 hardware architecture is a clean-sheet
> design which shares some of its DNA with AArch32, but that is all.
Ok, git it. Sorry for misunderstanding
> 
>> I admit that there are much more difference between architectures
>> than for x86 so you might be right that the difference in the code
>> could be too big. I just have a feeling it’s not. I can mistake of
>> course, I did not diff specifically
> 
> Possibly.  I don't really want to make the port a mess of #ifdefs and
> suchlike, so I'd fight pretty hard against it.
> 
> It is possible to do some macro trickery to write common runtime
> routines, but with sufficient such trickery it'd be possible to do
> that with any two unrelated arches.  While it might save some time, it
> adds another layer of complexity and makes it harder to write
> efficient and idiomatic code.  In particular things such as predicated
> instructions, which are an important part of the AArch32 ISA, are
> absent on AArch64.
Very much possible. I don’t want to propose it now, was just mentioning the probability. Ok it’s low, let’s dismiss it
> 
> Andrew.