diff --git a/include/llvm/CodeGen/SlotIndexes.h b/include/llvm/CodeGen/SlotIndexes.h
index b1bd4cd30b7..f1f047b44ed 100644
--- a/include/llvm/CodeGen/SlotIndexes.h
+++ b/include/llvm/CodeGen/SlotIndexes.h
@@ -23,6 +23,7 @@
 #define LLVM_CODEGEN_SLOTINDEXES_H
 
 #include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/SmallVector.h"
@@ -762,6 +763,47 @@ namespace llvm {
       mi2iMap.insert(std::make_pair(newMI, replaceBaseIndex));
     }
 
+    /// Add the given MachineBasicBlock into the maps.
+    void insertMBBInMaps(MachineBasicBlock *mbb) {
+      MachineFunction::iterator nextMBB =
+        llvm::next(MachineFunction::iterator(mbb));
+      IndexListEntry *startEntry = createEntry(0, 0);
+      IndexListEntry *terminatorEntry = createEntry(0, 0); 
+      IndexListEntry *nextEntry = 0;
+
+      if (nextMBB == mbb->getParent()->end()) {
+        nextEntry = getTail();
+      } else {
+        nextEntry = &getMBBStartIdx(nextMBB).entry();
+      }
+
+      insert(nextEntry, startEntry);
+      insert(nextEntry, terminatorEntry);
+
+      SlotIndex startIdx(startEntry, SlotIndex::LOAD);
+      SlotIndex terminatorIdx(terminatorEntry, SlotIndex::PHI_BIT);
+      SlotIndex endIdx(nextEntry, SlotIndex::LOAD);
+
+      terminatorGaps.insert(
+        std::make_pair(mbb, terminatorIdx));
+
+      mbb2IdxMap.insert(
+        std::make_pair(mbb, std::make_pair(startIdx, endIdx)));
+
+      idx2MBBMap.push_back(IdxMBBPair(startIdx, mbb));
+
+      if (MachineFunction::iterator(mbb) != mbb->getParent()->begin()) {
+        // Have to update the end index of the previous block.
+        MachineBasicBlock *priorMBB =
+          llvm::prior(MachineFunction::iterator(mbb));
+        mbb2IdxMap[priorMBB].second = startIdx;
+      }
+
+      renumberIndexes();
+      std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
+
+    }
+
   };