diff --git a/lib/Analysis/Interval.cpp b/lib/Analysis/Interval.cpp
new file mode 100644
index 00000000000..f1737fc39af
--- /dev/null
+++ b/lib/Analysis/Interval.cpp
@@ -0,0 +1,85 @@
+//===- Intervals.cpp - Interval partition Calculation ------------*- C++ -*--=//
+//
+// This file contains the declaration of the cfg::IntervalPartition class, which
+// calculates and represent the interval partition of a method.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/Intervals.h"
+#include "llvm/Method.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/CFG.h"
+
+void cfg::IntervalPartition::UpdateSuccessors(cfg::Interval *Int) {
+  BasicBlock *Header = Int->HeaderNode;
+  for (cfg::Interval::succ_iterator I = Int->Successors.begin(), 
+	                            E = Int->Successors.end(); I != E; ++I)
+    getBlockInterval(*I)->Predecessors.push_back(Header);
+}
+
+// IntervalPartition ctor - Build the partition for the specified method
+cfg::IntervalPartition::IntervalPartition(Method *M) {
+  BasicBlock *MethodStart = M->getBasicBlocks().front();
+  assert(MethodStart && "Cannot operate on prototypes!");
+
+  ProcessInterval(MethodStart);
+  RootInterval = getBlockInterval(MethodStart);
+
+  // Now that we know all of the successor information, propogate this to the
+  // predecessors for each block...
+  for(iterator I = begin(), E = end(); I != E; ++I)
+    UpdateSuccessors(*I);
+}
+
+void cfg::IntervalPartition::ProcessInterval(BasicBlock *Header) {
+  if (getBlockInterval(Header)) return;  // Interval already constructed
+
+  Interval *Int = new Interval(Header);
+  IntervalList.push_back(Int);           // Add the interval to our current set
+  IntervalMap.insert(make_pair(Header, Int));
+
+  // Check all of our successors to see if they are in the interval...
+  for (succ_iterator I = succ_begin(Header), E = succ_end(Header); I != E; ++I)
+    ProcessBasicBlock(Int, *I);
+
+  // Build all of the successor intervals of this interval now...
+  for(Interval::succ_iterator I = Int->Successors.begin(), 
+	E = Int->Successors.end(); I != E; ++I)
+    ProcessInterval(*I);
+}
+
+void cfg::IntervalPartition::ProcessBasicBlock(Interval *Int, BasicBlock *BB) {
+  assert(Int && "Null interval == bad!");
+  assert(BB && "Null interval == bad!");
+
+  Interval *CurInt = getBlockInterval(BB);
+  if (CurInt == Int) {                  // Already in this interval...
+    return;
+  } else if (CurInt != 0) {             // In another interval, add as successor
+    if (!Int->isSuccessor(BB))          // Add only if not already in set
+      Int->Successors.push_back(BB);
+  } else {                              // Otherwise, not in interval yet
+    for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
+      if (!Int->contains(*I)) {         // If pred not in interval, we can't be
+	if (!Int->isSuccessor(BB))      // Add only if not already in set
+	  Int->Successors.push_back(BB);
+	return;                         // See you later
+      }
+    }
+    
+    // If we get here, then all of the predecessors of BB are in the interval
+    // already.  In this case, we must add BB to the interval!
+    Int->Nodes.push_back(BB);
+    IntervalMap.insert(make_pair(BB, Int));
+    
+    if (Int->isSuccessor(BB)) {
+      // If we were in the successor list from before... remove from succ list
+      remove(Int->Successors.begin(), Int->Successors.end(), BB);
+    }
+    
+    // Now that we have discovered that BB is in the interval, perhaps some of
+    // its successors are as well?
+    for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I)
+      ProcessBasicBlock(Int, *I);
+  }
+}