After fix all asserts found by machine verifier in PowerPC target with following patches, we can activate machine verifier as default.
https://reviews.llvm.org/rL293769
https://reviews.llvm.org/rL348566
https://reviews.llvm.org/rL349030
https://reviews.llvm.org/rL349029
https://reviews.llvm.org/rL350113
https://reviews.llvm.org/rL350111
https://reviews.llvm.org/rL350799
https://reviews.llvm.org/rL350165
https://reviews.llvm.org/rL355378
https://reviews.llvm.org/rL352174
https://reviews.llvm.org/rL354762
https://reviews.llvm.org/rL350115
It's also found in PR#27456, https://bugs.llvm.org/show_bug.cgi?id=27456