Move use list management into MachineRegisterInfo.

Register MachineOperands are kept in linked lists accessible via MRI's
reg_iterator interfaces. The linked list management was handled partly
by MachineOperand methods, partly by MRI methods.

Move all of the list management into MRI, delete
MO::AddRegOperandToRegInfo() and MO::RemoveRegOperandFromRegInfo().

Be more explicit about handling the cases where an MRI pointer isn't
available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161632 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index f361d1a..151b402 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -109,7 +109,8 @@
   assert(N->getParent() != 0 && "machine instruction not in a basic block");
 
   // Remove from the use/def lists.
-  N->RemoveRegOperandsFromUseLists();
+  if (MachineFunction *MF = N->getParent()->getParent())
+    N->RemoveRegOperandsFromUseLists(MF->getRegInfo());
 
   N->setParent(0);