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

Kit Barton via llvm-dev llvm-dev at lists.llvm.org
Mon Aug 20 12:42:23 PDT 2018

Hi all,
I just posted two patches on phabricator to remove Darwin support from the
POWER backend.

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.

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

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.

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