Added TargetRegisterInfo::getAllocatableClass.

The ensures that virtual registers always belong to an allocatable class.
If your target attempts to create a vreg for an operand that has no
allocatable register subclass, you will crash quickly.

This ensures that targets define register classes as intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156046 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index c30b133..f98e059 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1298,7 +1298,8 @@
         // Unfold the load.
         DEBUG(dbgs() << "2addr:   UNFOLDING: " << MI);
         const TargetRegisterClass *RC =
-          TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI);
+          TRI->getAllocatableClass(
+            TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI));
         unsigned Reg = MRI->createVirtualRegister(RC);
         SmallVector<MachineInstr *, 2> NewMIs;
         if (!TII->unfoldMemoryOperand(MF, &MI, Reg,