diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 69ab593..dee4786 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -335,12 +335,32 @@
   if (this == fromMBB)
     return;
   
-  for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(), 
-       E = fromMBB->succ_end(); I != E; ++I)
-    addSuccessor(*I);
+  while (!fromMBB->succ_empty()) {
+    MachineBasicBlock *Succ = *fromMBB->succ_begin();
+    addSuccessor(Succ);
+    fromMBB->removeSuccessor(Succ);
+  }
+}
+
+void
+MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
+  if (this == fromMBB)
+    return;
   
-  while (!fromMBB->succ_empty())
-    fromMBB->removeSuccessor(fromMBB->succ_begin());
+  while (!fromMBB->succ_empty()) {
+    MachineBasicBlock *Succ = *fromMBB->succ_begin();
+    addSuccessor(Succ);
+    fromMBB->removeSuccessor(Succ);
+
+    // Fix up any PHI nodes in the successor.
+    for (MachineBasicBlock::iterator MI = Succ->begin(), ME = Succ->end();
+         MI != ME && MI->isPHI(); ++MI)
+      for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
+        MachineOperand &MO = MI->getOperand(i);
+        if (MO.getMBB() == fromMBB)
+          MO.setMBB(this);
+      }
+  }
 }
 
 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {