[llvm-dev] PowerPC LLVM support much appreciated

[Fāng-ruì Sòng via llvm-dev]

On Wed, Nov 10, 2021 at 6:34 AM James Y Knight via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
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>
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> On Wed, Nov 10, 2021 at 9:07 AM John Paul Adrian Glaubitz via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> I fully understand the reasoning and I absolutely agree with you. However, the
>> the actual changes required to get LLVM to build on Darwin/PPC seem to be rather
>> minimal, given when we ignore the additional tests which is why I don't think
>> that Darwin/PPC would actually be such a maintenance burden.
>>
>> It would be different if there was no support for either Darwin or PPC at all, but
>> that's not the case. It's more a question of tying to pieces of string together
>> which are already there.
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> I think there was a lot more behavior specific to the intersection of Darwin+PPC (not applicable to other PPC OSes or other Darwin architectures), than one might think (and than has been mentioned on this thread so far). Fortunately, I don't recall details -- but I rather doubt it'll be such a trivial change to resurrect Darwin PPC support.

Yes, Darwin+PPC diverge a lot from ELF+PPC.
It had dispatches all over the place which would continuous causing
maintenance burden to folks who are developing the active back end.
The amount of change was more than 2000 lines of code.
For example, I have made these commits in 2020 after the deprecation in 2018:

bfa6ca07a8cda0ab889b7fee0b914907ce594e11 ("[PowerPC] Delete remnant
Darwin ISelLowering code") removed 760 lines.
3e851f4a688c42315355aae743b403dddeba9860 ("[PowerPC] Delete
PPCMachObjectWriter and powerpc{,64}-apple-darwin") removed 397 lines.
7c4555f60d96d8a3ed35d74dab7e591dacc24b8d ("[PowerPC] Delete remnant
Darwin code in PPCAsmParser") removed 118 lines.

> Might I suggest installing Linux on old Mac PPC hardware, instead? MacOS 10.5 was the last release able to run on PPC, and hasn't been updated in 12 years.

Good suggestion:) FreeBSD and Linux are getting updated. I have seen
several folks installing the updated OSes onto the old Mac PPC
hardware.

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