When combining extsw and sldi in PPCMIPeephole, we have to check if extsw's second operand is a virtual register, otherwise we might get miscompile. For now, I haven't find a real world case, so I posted a MIR test case.
Updated patch to use Register::isVirtualRegister, a replacement of TargetRegisterInfo::isVirtualRegister.
commit 2bea69bf6503ffc9f3cde9a52b5dac1a25e94e1c Author: Daniel Sanders <firstname.lastname@example.org> Date: Thu Aug 1 23:27:28 2019 +0000 Finish moving TargetRegisterInfo::isVirtualRegister() and friends to llvm::Register as started by r367614. NFC llvm-svn: 367633