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diff --git a/clang/lib/Analysis/CFGReachabilityAnalysis.cpp b/clang/lib/Analysis/CFGReachabilityAnalysis.cpp
new file mode 100644
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--- /dev/null
+++ b/clang/lib/Analysis/CFGReachabilityAnalysis.cpp
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+//==- CFGReachabilityAnalysis.cpp - Basic reachability analysis --*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a flow-sensitive, (mostly) path-insensitive reachability
+// analysis based on Clang's CFGs.  Clients can query if a given basic block
+// is reachable within the CFG.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/SmallVector.h"
+#include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
+#include "clang/Analysis/CFG.h"
+
+using namespace clang;
+
+CFGReverseBlockReachabilityAnalysis::CFGReverseBlockReachabilityAnalysis(const CFG &cfg)
+  : analyzed(cfg.getNumBlockIDs(), false) {}
+
+bool CFGReverseBlockReachabilityAnalysis::isReachable(const CFGBlock *Src,
+                                          const CFGBlock *Dst) {
+
+  const unsigned DstBlockID = Dst->getBlockID();
+  
+  // If we haven't analyzed the destination node, run the analysis now
+  if (!analyzed[DstBlockID]) {
+    mapReachability(Dst);
+    analyzed[DstBlockID] = true;
+  }
+  
+  // Return the cached result
+  return reachable[DstBlockID][Src->getBlockID()];
+}
+
+// Maps reachability to a common node by walking the predecessors of the
+// destination node.
+void CFGReverseBlockReachabilityAnalysis::mapReachability(const CFGBlock *Dst) {
+  SmallVector<const CFGBlock *, 11> worklist;
+  llvm::BitVector visited(analyzed.size());
+  
+  ReachableSet &DstReachability = reachable[Dst->getBlockID()];
+  DstReachability.resize(analyzed.size(), false);
+  
+  // Start searching from the destination node, since we commonly will perform
+  // multiple queries relating to a destination node.
+  worklist.push_back(Dst);
+  bool firstRun = true;
+  
+  while (!worklist.empty()) {    
+    const CFGBlock *block = worklist.back();
+    worklist.pop_back();
+    
+    if (visited[block->getBlockID()])
+      continue;
+    visited[block->getBlockID()] = true;
+    
+    // Update reachability information for this node -> Dst
+    if (!firstRun) {
+      // Don't insert Dst -> Dst unless it was a predecessor of itself
+      DstReachability[block->getBlockID()] = true;
+    }
+    else
+      firstRun = false;
+    
+    // Add the predecessors to the worklist.
+    for (CFGBlock::const_pred_iterator i = block->pred_begin(), 
+         e = block->pred_end(); i != e; ++i) {
+      worklist.push_back(*i);
+    }
+  }
+}