Add (initial?) static analyzer support for handling C++ references.

This change was a lot bigger than I originally anticipated; among
other things it requires us storing more information in the CFG to
record what block-level expressions need to be evaluated as lvalues.

The big change is that CFGBlocks no longer contain Stmt*'s by
CFGElements.  Currently CFGElements just wrap Stmt*, but they also
store a bit indicating whether the block-level expression should be
evalauted as an lvalue.  DeclStmts involving the initialization of a
reference require us treating the initialization expression as an
lvalue, even though that information isn't recorded in the AST.
Conceptually this change isn't that complicated, but it required
bubbling up the data through the CFGBuilder, to GRCoreEngine, and
eventually to GRExprEngine.

The addition of CFGElement is also useful for when we want to handle
more control-flow constructs or other data we want to keep in the CFG
that isn't represented well with just a block of statements.

In GRExprEngine, this patch introduces logic for evaluating the
lvalues of references, which currently retrieves the internal "pointer
value" that the reference represents.  EvalLoad does a two stage load
to catch null dereferences involving an invalid reference (although
this could possibly be caught earlier during the initialization of a
reference).

Symbols are currently symbolicated using the reference type, instead
of a pointer type, and special handling is required creating
ElementRegions that layer on SymbolicRegions (see the changes to
RegionStoreManager).

Along the way, the DeadStoresChecker also silences warnings involving
dead stores to references.  This was the original change I introduced
(which I wrote test cases for) that I realized caused GRExprEngine to
crash.

llvm-svn: 91501

6 files changed, 176 insertions, 79 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index e1a1e72c204..884188acd78 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -34,6 +34,17 @@ static SourceLocation GetEndLoc(Decl* D) {
 
   return D->getLocation();
 }
+  
+class AddStmtChoice {
+public:
+  enum Kind { NotAlwaysAdd = 0, AlwaysAdd, AlwaysAddAsLValue };
+public:
+  AddStmtChoice(Kind kind) : k(kind) {}  
+  bool alwaysAdd() const { return k != NotAlwaysAdd; }
+  bool asLValue() const { return k == AlwaysAddAsLValue; }
+private:
+  Kind k;
+};
 
 /// CFGBuilder - This class implements CFG construction from an AST.
 ///   The builder is stateful: an instance of the builder should be used to only
@@ -84,15 +95,16 @@ public:
 
 private:
   // Visitors to walk an AST and construct the CFG.
-  CFGBlock *VisitAddrLabelExpr(AddrLabelExpr *A, bool alwaysAdd);
-  CFGBlock *VisitBinaryOperator(BinaryOperator *B, bool alwaysAdd);
-  CFGBlock *VisitBlockExpr(BlockExpr* E, bool alwaysAdd);
+  CFGBlock *VisitAddrLabelExpr(AddrLabelExpr *A, AddStmtChoice asc);
+  CFGBlock *VisitBinaryOperator(BinaryOperator *B, AddStmtChoice asc);
+  CFGBlock *VisitBlockExpr(BlockExpr* E, AddStmtChoice asc);
   CFGBlock *VisitBreakStmt(BreakStmt *B);
-  CFGBlock *VisitCallExpr(CallExpr *C, bool alwaysAdd);
+  CFGBlock *VisitCallExpr(CallExpr *C, AddStmtChoice asc);
   CFGBlock *VisitCaseStmt(CaseStmt *C);
-  CFGBlock *VisitChooseExpr(ChooseExpr *C);
+  CFGBlock *VisitChooseExpr(ChooseExpr *C, AddStmtChoice asc);
   CFGBlock *VisitCompoundStmt(CompoundStmt *C);
-  CFGBlock *VisitConditionalOperator(ConditionalOperator *C);
+  CFGBlock *VisitConditionalOperator(ConditionalOperator *C,
+                                     AddStmtChoice asc);
   CFGBlock *VisitContinueStmt(ContinueStmt *C);
   CFGBlock *VisitCXXCatchStmt(CXXCatchStmt *S) { return NYS(); }
   CFGBlock *VisitCXXThrowExpr(CXXThrowExpr *T);
@@ -112,13 +124,13 @@ private:
   CFGBlock *VisitObjCAtTryStmt(ObjCAtTryStmt *S);
   CFGBlock *VisitObjCForCollectionStmt(ObjCForCollectionStmt *S);
   CFGBlock *VisitReturnStmt(ReturnStmt* R);
-  CFGBlock *VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E, bool alwaysAdd);
-  CFGBlock *VisitStmtExpr(StmtExpr *S, bool alwaysAdd);
+  CFGBlock *VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E, AddStmtChoice asc);
+  CFGBlock *VisitStmtExpr(StmtExpr *S, AddStmtChoice asc);
   CFGBlock *VisitSwitchStmt(SwitchStmt *S);
   CFGBlock *VisitWhileStmt(WhileStmt *W);
 
-  CFGBlock *Visit(Stmt *S, bool alwaysAdd = false);
-  CFGBlock *VisitStmt(Stmt *S, bool alwaysAdd);
+  CFGBlock *Visit(Stmt *S, AddStmtChoice asc = AddStmtChoice::NotAlwaysAdd);
+  CFGBlock *VisitStmt(Stmt *S, AddStmtChoice asc);
   CFGBlock *VisitChildren(Stmt* S);
 
   // NYS == Not Yet Supported
@@ -130,10 +142,13 @@ private:
   void autoCreateBlock() { if (!Block) Block = createBlock(); }
   CFGBlock *createBlock(bool add_successor = true);
   bool FinishBlock(CFGBlock* B);
-  CFGBlock *addStmt(Stmt *S) { return Visit(S, true); }
+  CFGBlock *addStmt(Stmt *S, AddStmtChoice asc = AddStmtChoice::AlwaysAdd) {
+    return Visit(S, asc);
+  }
   
-  void AppendStmt(CFGBlock *B, Stmt *S) {
-    B->appendStmt(S, cfg->getBumpVectorContext());
+  void AppendStmt(CFGBlock *B, Stmt *S,
+                  AddStmtChoice asc = AddStmtChoice::AlwaysAdd) {
+    B->appendStmt(S, cfg->getBumpVectorContext(), asc.asLValue());
   }
   
   void AddSuccessor(CFGBlock *B, CFGBlock *S) {
@@ -278,38 +293,38 @@ bool CFGBuilder::FinishBlock(CFGBlock* B) {
 /// Visit - Walk the subtree of a statement and add extra
 ///   blocks for ternary operators, &&, and ||.  We also process "," and
 ///   DeclStmts (which may contain nested control-flow).
-CFGBlock* CFGBuilder::Visit(Stmt * S, bool alwaysAdd) {
+CFGBlock* CFGBuilder::Visit(Stmt * S, AddStmtChoice asc) {
 tryAgain:
   switch (S->getStmtClass()) {
     default:
-      return VisitStmt(S, alwaysAdd);
+      return VisitStmt(S, asc);
 
     case Stmt::AddrLabelExprClass:
-      return VisitAddrLabelExpr(cast<AddrLabelExpr>(S), alwaysAdd);
+      return VisitAddrLabelExpr(cast<AddrLabelExpr>(S), asc);
 
     case Stmt::BinaryOperatorClass:
-      return VisitBinaryOperator(cast<BinaryOperator>(S), alwaysAdd);
+      return VisitBinaryOperator(cast<BinaryOperator>(S), asc);
 
     case Stmt::BlockExprClass:
-      return VisitBlockExpr(cast<BlockExpr>(S), alwaysAdd);
+      return VisitBlockExpr(cast<BlockExpr>(S), asc);
 
     case Stmt::BreakStmtClass:
       return VisitBreakStmt(cast<BreakStmt>(S));
 
     case Stmt::CallExprClass:
-      return VisitCallExpr(cast<CallExpr>(S), alwaysAdd);
+      return VisitCallExpr(cast<CallExpr>(S), asc);
 
     case Stmt::CaseStmtClass:
       return VisitCaseStmt(cast<CaseStmt>(S));
 
     case Stmt::ChooseExprClass:
-      return VisitChooseExpr(cast<ChooseExpr>(S));
+      return VisitChooseExpr(cast<ChooseExpr>(S), asc);
 
     case Stmt::CompoundStmtClass:
       return VisitCompoundStmt(cast<CompoundStmt>(S));
 
     case Stmt::ConditionalOperatorClass:
-      return VisitConditionalOperator(cast<ConditionalOperator>(S));
+      return VisitConditionalOperator(cast<ConditionalOperator>(S), asc);
 
     case Stmt::ContinueStmtClass:
       return VisitContinueStmt(cast<ContinueStmt>(S));
@@ -367,10 +382,10 @@ tryAgain:
       return VisitReturnStmt(cast<ReturnStmt>(S));
 
     case Stmt::SizeOfAlignOfExprClass:
-      return VisitSizeOfAlignOfExpr(cast<SizeOfAlignOfExpr>(S), alwaysAdd);
+      return VisitSizeOfAlignOfExpr(cast<SizeOfAlignOfExpr>(S), asc);
 
     case Stmt::StmtExprClass:
-      return VisitStmtExpr(cast<StmtExpr>(S), alwaysAdd);
+      return VisitStmtExpr(cast<StmtExpr>(S), asc);
 
     case Stmt::SwitchStmtClass:
       return VisitSwitchStmt(cast<SwitchStmt>(S));
@@ -380,10 +395,10 @@ tryAgain:
   }
 }
 
-CFGBlock *CFGBuilder::VisitStmt(Stmt *S, bool alwaysAdd) {
-  if (alwaysAdd) {
+CFGBlock *CFGBuilder::VisitStmt(Stmt *S, AddStmtChoice asc) {
+  if (asc.alwaysAdd()) {
     autoCreateBlock();
-    AppendStmt(Block, S);
+    AppendStmt(Block, S, asc);
   }
 
   return VisitChildren(S);
@@ -399,21 +414,23 @@ CFGBlock *CFGBuilder::VisitChildren(Stmt* Terminator) {
   return B;
 }
 
-CFGBlock *CFGBuilder::VisitAddrLabelExpr(AddrLabelExpr *A, bool alwaysAdd) {
+CFGBlock *CFGBuilder::VisitAddrLabelExpr(AddrLabelExpr *A,
+                                         AddStmtChoice asc) {
   AddressTakenLabels.insert(A->getLabel());
 
-  if (alwaysAdd) {
+  if (asc.alwaysAdd()) {
     autoCreateBlock();
-    AppendStmt(Block, A);
+    AppendStmt(Block, A, asc);
   }
 
   return Block;
 }
 
-CFGBlock *CFGBuilder::VisitBinaryOperator(BinaryOperator *B, bool alwaysAdd) {
+CFGBlock *CFGBuilder::VisitBinaryOperator(BinaryOperator *B,
+                                          AddStmtChoice asc) {
   if (B->isLogicalOp()) { // && or ||
     CFGBlock* ConfluenceBlock = Block ? Block : createBlock();
-    AppendStmt(ConfluenceBlock, B);
+    AppendStmt(ConfluenceBlock, B, asc);
 
     if (!FinishBlock(ConfluenceBlock))
       return 0;
@@ -450,18 +467,18 @@ CFGBlock *CFGBuilder::VisitBinaryOperator(BinaryOperator *B, bool alwaysAdd) {
   }
   else if (B->getOpcode() == BinaryOperator::Comma) { // ,
     autoCreateBlock();
-    AppendStmt(Block, B);
+    AppendStmt(Block, B, asc);
     addStmt(B->getRHS());
     return addStmt(B->getLHS());
   }
 
-  return VisitStmt(B, alwaysAdd);
+  return VisitStmt(B, asc);
 }
 
-CFGBlock *CFGBuilder::VisitBlockExpr(BlockExpr *E, bool alwaysAdd) {
-  if (alwaysAdd) {
+CFGBlock *CFGBuilder::VisitBlockExpr(BlockExpr *E, AddStmtChoice asc) {
+  if (asc.alwaysAdd()) {
     autoCreateBlock();
-    AppendStmt(Block, E);
+    AppendStmt(Block, E, asc);
   }
   return Block;
 }
@@ -487,7 +504,7 @@ CFGBlock *CFGBuilder::VisitBreakStmt(BreakStmt *B) {
   return Block;
 }
 
-CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, bool alwaysAdd) {
+CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
   // If this is a call to a no-return function, this stops the block here.
   bool NoReturn = false;
   if (C->getCallee()->getType().getNoReturnAttr()) {
@@ -499,14 +516,14 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, bool alwaysAdd) {
       NoReturn = true;
 
   if (!NoReturn)
-    return VisitStmt(C, alwaysAdd);
+    return VisitStmt(C, asc);
 
   if (Block && !FinishBlock(Block))
     return 0;
 
   // Create new block with no successor for the remaining pieces.
   Block = createBlock(false);
-  AppendStmt(Block, C);
+  AppendStmt(Block, C, asc);
 
   // Wire this to the exit block directly.
   AddSuccessor(Block, &cfg->getExit());
@@ -514,9 +531,10 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, bool alwaysAdd) {
   return VisitChildren(C);
 }
 
-CFGBlock *CFGBuilder::VisitChooseExpr(ChooseExpr *C) {
+CFGBlock *CFGBuilder::VisitChooseExpr(ChooseExpr *C,
+                                      AddStmtChoice asc) {
   CFGBlock* ConfluenceBlock = Block ? Block : createBlock();
-  AppendStmt(ConfluenceBlock, C);
+  AppendStmt(ConfluenceBlock, C, asc);
   if (!FinishBlock(ConfluenceBlock))
     return 0;
 
@@ -555,11 +573,12 @@ CFGBlock* CFGBuilder::VisitCompoundStmt(CompoundStmt* C) {
   return LastBlock;
 }
 
-CFGBlock *CFGBuilder::VisitConditionalOperator(ConditionalOperator *C) {
+CFGBlock *CFGBuilder::VisitConditionalOperator(ConditionalOperator *C,
+                                               AddStmtChoice asc) {
   // Create the confluence block that will "merge" the results of the ternary
   // expression.
   CFGBlock* ConfluenceBlock = Block ? Block : createBlock();
-  AppendStmt(ConfluenceBlock, C);
+  AppendStmt(ConfluenceBlock, C, asc);
   if (!FinishBlock(ConfluenceBlock))
     return 0;
 
@@ -670,7 +689,10 @@ CFGBlock *CFGBuilder::VisitDeclSubExpr(Decl* D) {
       case Stmt::StringLiteralClass:
         break;
       default:
-        Block = addStmt(Init);
+        Block = addStmt(Init,
+                        VD->getType()->isReferenceType()
+                        ? AddStmtChoice::AlwaysAddAsLValue
+                        : AddStmtChoice::AlwaysAdd);
     }
   }
 
@@ -776,7 +798,7 @@ CFGBlock* CFGBuilder::VisitReturnStmt(ReturnStmt* R) {
 
   // Add the return statement to the block.  This may create new blocks if R
   // contains control-flow (short-circuit operations).
-  return VisitStmt(R, true);
+  return VisitStmt(R, AddStmtChoice::AlwaysAdd);
 }
 
 CFGBlock* CFGBuilder::VisitLabelStmt(LabelStmt* L) {
@@ -1000,7 +1022,7 @@ CFGBlock* CFGBuilder::VisitObjCForCollectionStmt(ObjCForCollectionStmt* S) {
   // Walk the 'element' expression to see if there are any side-effects.  We
   // generate new blocks as necesary.  We DON'T add the statement by default to
   // the CFG unless it contains control-flow.
-  EntryConditionBlock = Visit(S->getElement(), false);
+  EntryConditionBlock = Visit(S->getElement(), AddStmtChoice::NotAlwaysAdd);
   if (Block) {
     if (!FinishBlock(EntryConditionBlock))
       return 0;
@@ -1182,7 +1204,7 @@ CFGBlock* CFGBuilder::VisitObjCAtThrowStmt(ObjCAtThrowStmt* S) {
 
   // Add the statement to the block.  This may create new blocks if S contains
   // control-flow (short-circuit operations).
-  return VisitStmt(S, true);
+  return VisitStmt(S, AddStmtChoice::AlwaysAdd);
 }
 
 CFGBlock* CFGBuilder::VisitCXXThrowExpr(CXXThrowExpr* T) {
@@ -1198,7 +1220,7 @@ CFGBlock* CFGBuilder::VisitCXXThrowExpr(CXXThrowExpr* T) {
 
   // Add the statement to the block.  This may create new blocks if S contains
   // control-flow (short-circuit operations).
-  return VisitStmt(T, true);
+  return VisitStmt(T, AddStmtChoice::AlwaysAdd);
 }
 
 CFGBlock *CFGBuilder::VisitDoStmt(DoStmt* D) {
@@ -1316,9 +1338,9 @@ CFGBlock* CFGBuilder::VisitContinueStmt(ContinueStmt* C) {
 }
 
 CFGBlock *CFGBuilder::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E,
-                                             bool alwaysAdd) {
+                                             AddStmtChoice asc) {
 
-  if (alwaysAdd) {
+  if (asc.alwaysAdd()) {
     autoCreateBlock();
     AppendStmt(Block, E);
   }
@@ -1335,8 +1357,8 @@ CFGBlock *CFGBuilder::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E,
 
 /// VisitStmtExpr - Utility method to handle (nested) statement
 ///  expressions (a GCC extension).
-CFGBlock* CFGBuilder::VisitStmtExpr(StmtExpr *SE, bool alwaysAdd) {
-  if (alwaysAdd) {
+CFGBlock* CFGBuilder::VisitStmtExpr(StmtExpr *SE, AddStmtChoice asc) {
+  if (asc.alwaysAdd()) {
     autoCreateBlock();
     AppendStmt(Block, SE);
   }
diff --git a/clang/lib/Analysis/CheckDeadStores.cpp b/clang/lib/Analysis/CheckDeadStores.cpp
index db9016fa1e6..f081c69c2b1 100644
--- a/clang/lib/Analysis/CheckDeadStores.cpp
+++ b/clang/lib/Analysis/CheckDeadStores.cpp
@@ -84,7 +84,14 @@ public:
                     const LiveVariables::AnalysisDataTy& AD,
                     const LiveVariables::ValTy& Live) {
 
-    if (VD->hasLocalStorage() && !Live(VD, AD) && 
+    if (!VD->hasLocalStorage())
+      return;
+    // Reference types confuse the dead stores checker.  Skip them
+    // for now.
+    if (VD->getType()->getAs<ReferenceType>())
+      return;
+
+    if (!Live(VD, AD) && 
         !(VD->getAttr<UnusedAttr>() || VD->getAttr<BlocksAttr>()))
       Report(VD, dsk, Ex->getSourceRange().getBegin(),
              Val->getSourceRange());
@@ -93,7 +100,6 @@ public:
   void CheckDeclRef(DeclRefExpr* DR, Expr* Val, DeadStoreKind dsk,
                     const LiveVariables::AnalysisDataTy& AD,
                     const LiveVariables::ValTy& Live) {
-
     if (VarDecl* VD = dyn_cast<VarDecl>(DR->getDecl()))
       CheckVarDecl(VD, DR, Val, dsk, AD, Live);
   }
@@ -183,8 +189,13 @@ public:
 
         if (!V)
           continue;
-
-        if (V->hasLocalStorage())
+          
+        if (V->hasLocalStorage()) {          
+          // Reference types confuse the dead stores checker.  Skip them
+          // for now.
+          if (V->getType()->getAs<ReferenceType>())
+            return;
+            
           if (Expr* E = V->getInit()) {
             // Don't warn on C++ objects (yet) until we can show that their
             // constructors/destructors don't have side effects.
@@ -218,6 +229,7 @@ public:
               Report(V, DeadInit, V->getLocation(), E->getSourceRange());
             }
           }
+        }
       }
   }
 };
diff --git a/clang/lib/Analysis/GRCoreEngine.cpp b/clang/lib/Analysis/GRCoreEngine.cpp
index 644dd199bea..1c05ddc60bc 100644
--- a/clang/lib/Analysis/GRCoreEngine.cpp
+++ b/clang/lib/Analysis/GRCoreEngine.cpp
@@ -122,8 +122,8 @@ void GRCoreEngine::ProcessEndPath(GREndPathNodeBuilder& Builder) {
   SubEngine.ProcessEndPath(Builder);
 }
 
-void GRCoreEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& Builder) {
-  SubEngine.ProcessStmt(S, Builder);
+void GRCoreEngine::ProcessStmt(CFGElement E, GRStmtNodeBuilder& Builder) {
+  SubEngine.ProcessStmt(E, Builder);
 }
 
 bool GRCoreEngine::ProcessBlockEntrance(CFGBlock* Blk, const GRState* State,
@@ -241,10 +241,10 @@ void GRCoreEngine::HandleBlockEntrance(const BlockEntrance& L,
   WList->setBlockCounter(Counter);
 
   // Process the entrance of the block.
-  if (Stmt* S = L.getFirstStmt()) {
+  if (CFGElement E = L.getFirstElement()) {
     GRStmtNodeBuilder Builder(L.getBlock(), 0, Pred, this,
                               SubEngine.getStateManager());
-    ProcessStmt(S, Builder);
+    ProcessStmt(E, Builder);
   }
   else
     HandleBlockExit(L.getBlock(), Pred);
diff --git a/clang/lib/Analysis/GRExprEngine.cpp b/clang/lib/Analysis/GRExprEngine.cpp
index 51e6a547529..a0ec87d2f75 100644
--- a/clang/lib/Analysis/GRExprEngine.cpp
+++ b/clang/lib/Analysis/GRExprEngine.cpp
@@ -33,6 +33,7 @@
 
 using namespace clang;
 using llvm::dyn_cast;
+using llvm::dyn_cast_or_null;
 using llvm::cast;
 using llvm::APSInt;
 
@@ -378,17 +379,15 @@ const GRState* GRExprEngine::getInitialState(const LocationContext *InitLoc) {
 // Top-level transfer function logic (Dispatcher).
 //===----------------------------------------------------------------------===//
 
-void GRExprEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& builder) {
-
+void GRExprEngine::ProcessStmt(CFGElement CE, GRStmtNodeBuilder& builder) {
+  CurrentStmt = CE.getStmt();
   PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),
-                                S->getLocStart(),
+                                CurrentStmt->getLocStart(),
                                 "Error evaluating statement");
 
   Builder = &builder;
   EntryNode = builder.getLastNode();
 
-  CurrentStmt = S;
-
   // Set up our simple checks.
   if (BatchAuditor)
     Builder->setAuditor(BatchAuditor.get());
@@ -415,7 +414,7 @@ void GRExprEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& builder) {
 
     // FIXME: This should soon be removed.
     ExplodedNodeSet Tmp2;
-    getTF().EvalDeadSymbols(Tmp2, *this, *Builder, EntryNode, S,
+    getTF().EvalDeadSymbols(Tmp2, *this, *Builder, EntryNode, CurrentStmt,
                             CleanedState, SymReaper);
 
     if (Checkers.empty())
@@ -437,8 +436,8 @@ void GRExprEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& builder) {
         Checker *checker = I->second;
         for (ExplodedNodeSet::iterator NI = SrcSet->begin(), NE = SrcSet->end();
              NI != NE; ++NI)
-          checker->GR_EvalDeadSymbols(*DstSet, *Builder, *this, S, *NI, 
-                                      SymReaper, tag);
+          checker->GR_EvalDeadSymbols(*DstSet, *Builder, *this, CurrentStmt,
+                                      *NI, SymReaper, tag);
         SrcSet = DstSet;
       }
     }
@@ -457,7 +456,10 @@ void GRExprEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& builder) {
     Builder->SetCleanedState(*I == EntryNode ? CleanedState : GetState(*I));
 
     // Visit the statement.
-    Visit(S, *I, Dst);
+    if (CE.asLValue())
+      VisitLValue(cast<Expr>(CurrentStmt), *I, Dst);
+    else
+      Visit(CurrentStmt, *I, Dst);
 
     // Do we need to auto-generate a node?  We only need to do this to generate
     // a node with a "cleaned" state; GRCoreEngine will actually handle
@@ -465,7 +467,7 @@ void GRExprEngine::ProcessStmt(Stmt* S, GRStmtNodeBuilder& builder) {
     if (Dst.size() == 1 && *Dst.begin() == EntryNode
         && !Builder->HasGeneratedNode && !HasAutoGenerated) {
       HasAutoGenerated = true;
-      builder.generateNode(S, GetState(EntryNode), *I);
+      builder.generateNode(CurrentStmt, GetState(EntryNode), *I);
     }
   }
 
@@ -1232,13 +1234,23 @@ void GRExprEngine::VisitCommonDeclRefExpr(Expr *Ex, const NamedDecl *D,
 
     SVal V = state->getLValue(VD, Pred->getLocationContext());
 
-    if (asLValue)
-      MakeNode(Dst, Ex, Pred, state->BindExpr(Ex, V),
-               ProgramPoint::PostLValueKind);
+    if (asLValue) {
+      // For references, the 'lvalue' is the pointer address stored in the
+      // reference region.
+      if (VD->getType()->isReferenceType()) {
+        if (const MemRegion *R = V.getAsRegion())
+          V = state->getSVal(R);
+        else
+          V = UnknownVal();
+      }
+      
+      MakeNode(Dst, Ex, Pred, state->BindExpr(Ex, V,
+                                              ProgramPoint::PostLValueKind));
+    }
     else
       EvalLoad(Dst, Ex, Pred, state, V);
-    return;
 
+    return;
   } else if (const EnumConstantDecl* ED = dyn_cast<EnumConstantDecl>(D)) {
     assert(!asLValue && "EnumConstantDecl does not have lvalue.");
 
@@ -1415,6 +1427,37 @@ void GRExprEngine::EvalLoad(ExplodedNodeSet& Dst, Expr *Ex, ExplodedNode* Pred,
                             const GRState* state, SVal location,
                             const void *tag, QualType LoadTy) {
 
+  // Are we loading from a region?  This actually results in two loads; one
+  // to fetch the address of the referenced value and one to fetch the
+  // referenced value.
+  if (const TypedRegion *TR = 
+        dyn_cast_or_null<TypedRegion>(location.getAsRegion())) {
+    
+    QualType ValTy = TR->getValueType(getContext());
+    if (const ReferenceType *RT = ValTy->getAs<ReferenceType>()) {
+      static int loadReferenceTag = 0;    
+      ExplodedNodeSet Tmp;
+      EvalLoadCommon(Tmp, Ex, Pred, state, location, &loadReferenceTag,
+                     getContext().getPointerType(RT->getPointeeType()));
+
+      // Perform the load from the referenced value.
+      for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end() ; I!=E; ++I) {
+        state = GetState(*I);
+        location = state->getSVal(Ex);
+        EvalLoadCommon(Dst, Ex, *I, state, location, tag, LoadTy);
+      }    
+      return;
+    }
+  }
+  
+  EvalLoadCommon(Dst, Ex, Pred, state, location, tag, LoadTy);
+}
+
+void GRExprEngine::EvalLoadCommon(ExplodedNodeSet& Dst, Expr *Ex,
+                                  ExplodedNode* Pred,
+                                  const GRState* state, SVal location,
+                                  const void *tag, QualType LoadTy) {
+  
   // Evaluate the location (checks for bad dereferences).
   ExplodedNodeSet Tmp;
   EvalLocation(Tmp, Ex, Pred, state, location, tag, true);
@@ -1992,8 +2035,12 @@ void GRExprEngine::VisitDeclStmt(DeclStmt *DS, ExplodedNode *Pred,
   //  time a function is called those values may not be current.
   ExplodedNodeSet Tmp;
 
-  if (InitEx)
-    Visit(InitEx, Pred, Tmp);
+  if (InitEx) {
+    if (VD->getType()->isReferenceType())
+      VisitLValue(InitEx, Pred, Tmp);
+    else
+      Visit(InitEx, Pred, Tmp);
+  }
   else
     Tmp.Add(Pred);
 
diff --git a/clang/lib/Analysis/RegionStore.cpp b/clang/lib/Analysis/RegionStore.cpp
index a96f6c85be8..bc3680e23da 100644
--- a/clang/lib/Analysis/RegionStore.cpp
+++ b/clang/lib/Analysis/RegionStore.cpp
@@ -1424,7 +1424,13 @@ const GRState *RegionStoreManager::Bind(const GRState *state, Loc L, SVal V) {
     // Binding directly to a symbolic region should be treated as binding
     // to element 0.
     QualType T = SR->getSymbol()->getType(getContext());
-    T = T->getAs<PointerType>()->getPointeeType();
+    
+    // FIXME: Is this the right way to handle symbols that are references?
+    if (const PointerType *PT = T->getAs<PointerType>())
+      T = PT->getPointeeType();
+    else
+      T = T->getAs<ReferenceType>()->getPointeeType();
+
     R = GetElementZeroRegion(SR, T);
   }
 
diff --git a/clang/lib/Analysis/Store.cpp b/clang/lib/Analysis/Store.cpp
index e6ff6e5af47..56f8a0a70c9 100644
--- a/clang/lib/Analysis/Store.cpp
+++ b/clang/lib/Analysis/Store.cpp
@@ -198,11 +198,21 @@ const MemRegion *StoreManager::CastRegion(const MemRegion *R, QualType CastToTy)
 ///  as another region.
 SVal  StoreManager::CastRetrievedVal(SVal V, const TypedRegion *R,
                                      QualType castTy) {
+  
+#ifndef NDEBUG
   if (castTy.isNull())
     return V;
+  
+  ASTContext &Ctx = ValMgr.getContext();
+  QualType T = R->getValueType(Ctx);
+
+  // Automatically translate references to pointers.
+  if (const ReferenceType *RT = T->getAs<ReferenceType>())
+    T = Ctx.getPointerType(RT->getPointeeType());
+
+  assert(ValMgr.getContext().hasSameUnqualifiedType(castTy, T));
+#endif
 
-  assert(ValMgr.getContext().hasSameUnqualifiedType(castTy,
-                                         R->getValueType(ValMgr.getContext())));
   return V;
 }