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

Bob Vandette bob.vandette at oracle.com
Thu Sep 29 12:33:32 UTC 2016

> On Sep 29, 2016, at 7:10 AM, Andrey Petushkov <andrey.petushkov at gmail.com> wrote:
>> 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
It is more that just possible.  I have provided you with an implementation that does just that.  
I don’t think you should be so fast to dismiss it.  


>> Andrew.

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