Check register classes also when changing them.

We have the same assertion in createVirtualRegister.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176959 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineRegisterInfo.cpp

@@ -37,6 +37,7 @@ MachineRegisterInfo::~MachineRegisterInfo() {
 ///
 void
 MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
+  assert(RC && RC->isAllocatable() && "Invalid RC for virtual register");
   VRegInfo[Reg].first = RC;
 }