This is the first in a series of patches to remove darwin support from the PowerPC backend. This patch issues an error message if Darwin support is attempted. It also cleans up all existing test cases, either converting the test to use an alternative triple or removing the test if the coverage is no longer needed.
Once this patch lands, subsequent patches can be committed that actively remove the Darwin code paths from POWER backend. Since these paths will be dead code at that point, the cleanup can be done using post-commit reviews when applicable.
There is a companion patch for Clang, which fixes test cases in Clang. I will open another review for those changes and link to this revision.