diff --git a/include/llvm/CodeGen/FunctionLoweringInfo.h b/include/llvm/CodeGen/FunctionLoweringInfo.h
index 7f03a7a..8b1c852 100644
--- a/include/llvm/CodeGen/FunctionLoweringInfo.h
+++ b/include/llvm/CodeGen/FunctionLoweringInfo.h
@@ -106,6 +106,10 @@
     LiveOutInfo() : NumSignBits(0), KnownOne(1, 0), KnownZero(1, 0) {}
   };
 
+  /// VisitedBBs - The set of basic blocks visited thus far by instruction
+  /// selection.
+  DenseSet<const BasicBlock*> VisitedBBs;
+
   /// PHINodesToUpdate - A list of phi instructions whose operand list will
   /// be updated after processing the current basic block.
   /// TODO: This isn't per-function state, it's per-basic-block state. But
diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 98582ba..c55cf85 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -219,6 +219,7 @@
   CatchInfoFound.clear();
 #endif
   LiveOutRegInfo.clear();
+  VisitedBBs.clear();
   ArgDbgValues.clear();
   ByValArgFrameIndexMap.clear();
   RegFixups.clear();
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 835aab2..9d3f5bc 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -831,6 +831,10 @@
 #ifndef NDEBUG
     CheckLineNumbers(LLVMBB);
 #endif
+
+    if (OptLevel != CodeGenOpt::None)
+      FuncInfo->VisitedBBs.insert(LLVMBB);
+
     FuncInfo->MBB = FuncInfo->MBBMap[LLVMBB];
     FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();