[PowerPC] add fsub-fneg test; NFC

This is a test for a transform that was suggested in the post-commit
mailing list thread for rL329821. The target in question is not in
trunk, so PPC gets to stand in for it because it's the only in-tree
target that sets 'isFPExtFree()' to 'true'.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@329963 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed