Re: [crosspost] dropping support for ia64

Dear matoro, Florian,

On 17.05.23 23:47, matoro wrote:
> On 2023-05-17 15:39, Florian Weimer wrote:
>> * Frank Scheiner:
>>
>>> On 12.05.23 17:57, Ard Biesheuvel wrote:
>>>> The bottom line is that, while I know of at least 2 people (on cc)
>>>> that test stuff on itanium, and package software for it, I don't think
>>>> there are any actual users remaining, and so it is doubtful whether it
>>>> is justified to ask people to spend time and effort on this.
>>>
>>> While I get your argument, I also find it important to be able to
>>> innovate without destroying the past. And with the already severly
>>> limited choice of current architectures for the masses (x86, arm), it
>>> becomes even more important to keep what we have or had in the past, to
>>> not end in a "If all you have is a hammer, everything looks like a
>>> nail." type of future.
>>
>> The history doesn't go away.  We still have pre-built ia64 system
>> images, the sources, and current machines can run ia64 code under
>> QEMU.  Those host systems will remain available (maybe under
>> virtualization) for many, many years to come.  So if anyone wants to
>> experiment with an architecture that has register trap bits and things
>> like that, it's possible.
>>
>> I expect the rest of the hardware itself is not remarkable, and
>> anything useful has been thoroughly reused for other systems (like we
>> did for the Itanium C++ ABI on the software side).
>>
>> From the userspace side, the issue is not so much testing (if we
>> bother to test our changes at all, we can use emulation), but
>> half-completed implementaton work (I ran into missing relaxations in
>> the link editor a while back, for example), and those limitations have
>> knock-on effects on generic code that we have to maintain.
> 
> FYI, QEMU does not have ia64 host or target support, not even TCG.

I assume Florian means user mode emulation, which for example can be 
used to complete a `debootstrap --foreign [...]` run when you don't have 
an existing ia64 userland on real hardware at hand.

I doubt that it works in the exact same way than the real thing, though. 
Such differences are part of the reasons why the OpenBSD devs don't seem 
to use cross compilers or virtualized or emulated systems to produce and 
test their OS, though they seem to use cross compilers for the bringup 
of new platforms IIC.

But if it's good enough to run ia64 binaries on other arches, why not.

Have a nice weekend,
Frank