[llvm-dev] [RFC] Remove Darwin support from POWER Backends

[Hal Finkel via llvm-dev]

On 08/20/2018 02:42 PM, Kit Barton via llvm-dev wrote:
> Hi all,
> I just posted two patches on phabricator to remove Darwin support from
> the POWER backend.

Thanks, Kit.

To connect the two threads, the last RFC we had on this subject was
here: http://lists.llvm.org/pipermail/llvm-dev/2016-October/106359.html
- it looks like we're all now in agreement to move forward.

>
> I thought I had posted this on the dev mailing list some time ago, but
> I cannot find a reference to it now. 
>
> The intention here is to cleanup the POWER backend. Darwin has not
> been supported on POWER for quite some time now, and we'd like to use
> this as an opportunity to clean up several aspects of the backend
> code. If there is any concerns with this, please let me know.
>
> As for the approach, the patch that I posted will issue an error
> message from the backend if you attempt to use the Darwin ABI on PPC.
> The intention is that once this patch lands, all of the
> Darwin-specific code paths will essentially be dead-code, and we can
> remove them on demand as we're touching various pieces of code. This
> cleanup should be done in stand-alone patches, but can be done as NFC
> changes and thus reviewed post-commit, whenever possible.

This is reasonable. Please proceed.

 -Hal

>
> I've cleaned up all of the test cases effected by this, mostly by
> converting them to a different powerpc target so as to not lose test
> coverage. There were a few tests that were ppc-darwin specific, which
> were removed.
>
> There is a companion patch to clean up test cases in Clang as well. I
> think we can use a similar approach for cleaning up ppc-specific
> darwin code in Clang, although I don't have a good idea right now for
> how much cleanup that will be.
>
> Thanks.
>
>
>
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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