r217556 - Thread Safety Analysis: major update to thread safety TIL.

Patrik Hägglund H patrik.h.hagglund at ericsson.com
Fri Sep 12 05:51:07 PDT 2014


With gcc-4.9.1, I get:

../tools/clang/lib/Analysis/ThreadSafetyTIL.cpp:173:11: error: overflow in implicit constant conversion [-Werror=overflow]
   Visited = 1;
           ^
Should unsigned be used instead of int below?

+  int          BlockID : 31; // unique id for this BB in the containing CFG.
+                             // IDs are in topological order.
+  int          Visited : 1;  // Bit to determine if a block has been visited
+                             // during a traversal.

/Patrik Hägglund

-----Original Message-----
From: cfe-commits-bounces at cs.uiuc.edu [mailto:cfe-commits-bounces at cs.uiuc.edu] On Behalf Of DeLesley Hutchins
Sent: den 11 september 2014 00:13
To: cfe-commits at cs.uiuc.edu
Subject: r217556 - Thread Safety Analysis: major update to thread safety TIL.

Author: delesley
Date: Wed Sep 10 17:12:52 2014
New Revision: 217556

URL: http://llvm.org/viewvc/llvm-project?rev=217556&view=rev
Log:
Thread Safety Analysis: major update to thread safety TIL.
Numerous changes, including:
  * Changed the way variables and instructions are handled in basic blocks to
    be more efficient.
  * Eliminated SExprRef.
  * Simplified futures.
  * Fixed documentation.
  * Compute dominator and post dominator trees.

Modified:
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyLogical.h
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyOps.def
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h
    cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyUtil.h
    cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp
    cfe/trunk/lib/Analysis/ThreadSafetyTIL.cpp

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h Wed Sep 10 17:12:52 2014
@@ -477,9 +477,9 @@ private:
                                            // Indexed by clang BlockID.
 
   LVarDefinitionMap CurrentLVarMap;
-  std::vector<til::Variable*> CurrentArguments;
-  std::vector<til::Variable*> CurrentInstructions;
-  std::vector<til::Variable*> IncompleteArgs;
+  std::vector<til::Phi*>   CurrentArguments;
+  std::vector<til::SExpr*> CurrentInstructions;
+  std::vector<til::Phi*>   IncompleteArgs;
   til::BasicBlock *CurrentBB;
   BlockInfo *CurrentBlockInfo;
 };

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyLogical.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyLogical.h?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyLogical.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyLogical.h Wed Sep 10 17:12:52 2014
@@ -41,13 +41,13 @@ private:
 };
 
 class Terminal : public LExpr {
-  til::SExprRef Expr;
+  til::SExpr *Expr;
 
 public:
   Terminal(til::SExpr *Expr) : LExpr(LExpr::Terminal), Expr(Expr) {}
 
-  const til::SExpr *expr() const { return Expr.get(); }
-  til::SExpr *expr() { return Expr.get(); }
+  const til::SExpr *expr() const { return Expr; }
+  til::SExpr *expr() { return Expr; }
 
   static bool classof(const LExpr *E) { return E->kind() == LExpr::Terminal; }
 };

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyOps.def
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyOps.def?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyOps.def (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyOps.def Wed Sep 10 17:12:52 2014
@@ -44,8 +44,11 @@ TIL_OPCODE_DEF(Cast)
 TIL_OPCODE_DEF(SCFG)
 TIL_OPCODE_DEF(BasicBlock)
 TIL_OPCODE_DEF(Phi)
+
+// Terminator instructions
 TIL_OPCODE_DEF(Goto)
 TIL_OPCODE_DEF(Branch)
+TIL_OPCODE_DEF(Return)
 
 // pseudo-terms
 TIL_OPCODE_DEF(Identifier)

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h Wed Sep 10 17:12:52 2014
@@ -63,24 +63,27 @@ namespace threadSafety {
 namespace til {
 
 
+/// Enum for the different distinct classes of SExpr
 enum TIL_Opcode {
 #define TIL_OPCODE_DEF(X) COP_##X,
 #include "ThreadSafetyOps.def"
 #undef TIL_OPCODE_DEF
 };
 
+/// Opcode for unary arithmetic operations.
 enum TIL_UnaryOpcode : unsigned char {
   UOP_Minus,        //  -
   UOP_BitNot,       //  ~
   UOP_LogicNot      //  !
 };
 
+/// Opcode for binary arithmetic operations.
 enum TIL_BinaryOpcode : unsigned char {
+  BOP_Add,          //  +
+  BOP_Sub,          //  -
   BOP_Mul,          //  *
   BOP_Div,          //  /
   BOP_Rem,          //  %
-  BOP_Add,          //  +
-  BOP_Sub,          //  -
   BOP_Shl,          //  <<
   BOP_Shr,          //  >>
   BOP_BitAnd,       //  &
@@ -90,10 +93,11 @@ enum TIL_BinaryOpcode : unsigned char {
   BOP_Neq,          //  !=
   BOP_Lt,           //  <
   BOP_Leq,          //  <=
-  BOP_LogicAnd,     //  &&
-  BOP_LogicOr       //  ||
+  BOP_LogicAnd,     //  &&  (no short-circuit)
+  BOP_LogicOr       //  ||  (no short-circuit)
 };
 
+/// Opcode for cast operations.
 enum TIL_CastOpcode : unsigned char {
   CAST_none = 0,
   CAST_extendNum,   // extend precision of numeric type
@@ -107,21 +111,24 @@ const TIL_Opcode       COP_Min  = COP_Fu
 const TIL_Opcode       COP_Max  = COP_Branch;
 const TIL_UnaryOpcode  UOP_Min  = UOP_Minus;
 const TIL_UnaryOpcode  UOP_Max  = UOP_LogicNot;
-const TIL_BinaryOpcode BOP_Min  = BOP_Mul;
+const TIL_BinaryOpcode BOP_Min  = BOP_Add;
 const TIL_BinaryOpcode BOP_Max  = BOP_LogicOr;
 const TIL_CastOpcode   CAST_Min = CAST_none;
 const TIL_CastOpcode   CAST_Max = CAST_toInt;
 
+/// Return the name of a unary opcode.
 StringRef getUnaryOpcodeString(TIL_UnaryOpcode Op);
+
+/// Return the name of a binary opcode.
 StringRef getBinaryOpcodeString(TIL_BinaryOpcode Op);
 
 
-// ValueTypes are data types that can actually be held in registers.
-// All variables and expressions must have a vBNF_Nonealue type.
-// Pointer types are further subdivided into the various heap-allocated
-// types, such as functions, records, etc.
-// Structured types that are passed by value (e.g. complex numbers)
-// require special handling; they use BT_ValueRef, and size ST_0.
+/// ValueTypes are data types that can actually be held in registers.
+/// All variables and expressions must have a value type.
+/// Pointer types are further subdivided into the various heap-allocated
+/// types, such as functions, records, etc.
+/// Structured types that are passed by value (e.g. complex numbers)
+/// require special handling; they use BT_ValueRef, and size ST_0.
 struct ValueType {
   enum BaseType : unsigned char {
     BT_Void = 0,
@@ -247,8 +254,10 @@ inline ValueType ValueType::getValueType
 }
 
 
+class BasicBlock;
+
 
-// Base class for AST nodes in the typed intermediate language.
+/// Base class for AST nodes in the typed intermediate language.
 class SExpr {
 public:
   TIL_Opcode opcode() const { return static_cast<TIL_Opcode>(Opcode); }
@@ -267,71 +276,47 @@ public:
   // template <class C> typename C::CType compare(CType* E, C& Cmp) {
   //   compare all subexpressions, following the comparator interface
   // }
-
   void *operator new(size_t S, MemRegionRef &R) {
     return ::operator new(S, R);
   }
 
-  // SExpr objects cannot be deleted.
+  /// SExpr objects cannot be deleted.
   // This declaration is public to workaround a gcc bug that breaks building
   // with REQUIRES_EH=1.
   void operator delete(void *) LLVM_DELETED_FUNCTION;
 
+  /// Returns the instruction ID for this expression.
+  /// All basic block instructions have a unique ID (i.e. virtual register).
+  unsigned id() const { return SExprID; }
+
+  /// Returns the block, if this is an instruction in a basic block,
+  /// otherwise returns null.
+  BasicBlock* block() const { return Block; }
+
+  /// Set the basic block and instruction ID for this expression.
+  void setID(BasicBlock *B, unsigned id) { Block = B; SExprID = id; }
+
 protected:
-  SExpr(TIL_Opcode Op) : Opcode(Op), Reserved(0), Flags(0) {}
-  SExpr(const SExpr &E) : Opcode(E.Opcode), Reserved(0), Flags(E.Flags) {}
+  SExpr(TIL_Opcode Op)
+    : Opcode(Op), Reserved(0), Flags(0), SExprID(0), Block(nullptr) {}
+  SExpr(const SExpr &E)
+    : Opcode(E.Opcode), Reserved(0), Flags(E.Flags), SExprID(0),
+      Block(nullptr) {}
 
   const unsigned char Opcode;
   unsigned char Reserved;
   unsigned short Flags;
+  unsigned SExprID;
+  BasicBlock* Block;
 
 private:
   SExpr() LLVM_DELETED_FUNCTION;
 
-  // SExpr objects must be created in an arena.
+  /// SExpr objects must be created in an arena.
   void *operator new(size_t) LLVM_DELETED_FUNCTION;
 };
 
 
-// Class for owning references to SExprs.
-// Includes attach/detach logic for counting variable references and lazy
-// rewriting strategies.
-class SExprRef {
-public:
-  SExprRef() : Ptr(nullptr) { }
-  SExprRef(std::nullptr_t P) : Ptr(nullptr) { }
-  SExprRef(SExprRef &&R) : Ptr(R.Ptr) { R.Ptr = nullptr; }
-
-  // Defined after Variable and Future, below.
-  inline SExprRef(SExpr *P);
-  inline ~SExprRef();
-
-  SExpr       *get()       { return Ptr; }
-  const SExpr *get() const { return Ptr; }
-
-  SExpr       *operator->()       { return get(); }
-  const SExpr *operator->() const { return get(); }
-
-  SExpr       &operator*()        { return *Ptr; }
-  const SExpr &operator*() const  { return *Ptr; }
-
-  bool operator==(const SExprRef &R) const { return Ptr == R.Ptr; }
-  bool operator!=(const SExprRef &R) const { return !operator==(R); }
-  bool operator==(const SExpr *P)    const { return Ptr == P; }
-  bool operator!=(const SExpr *P)    const { return !operator==(P); }
-  bool operator==(std::nullptr_t)    const { return Ptr == nullptr; }
-  bool operator!=(std::nullptr_t)    const { return Ptr != nullptr; }
-
-  inline void reset(SExpr *E);
-
-private:
-  inline void attach();
-  inline void detach();
-
-  SExpr *Ptr;
-};
-
-
 // Contains various helper functions for SExprs.
 namespace ThreadSafetyTIL {
   inline bool isTrivial(const SExpr *E) {
@@ -343,62 +328,64 @@ namespace ThreadSafetyTIL {
 // Nodes which declare variables
 class Function;
 class SFunction;
-class BasicBlock;
 class Let;
 
 
-// A named variable, e.g. "x".
-//
-// There are two distinct places in which a Variable can appear in the AST.
-// A variable declaration introduces a new variable, and can occur in 3 places:
-//   Let-expressions:           (Let (x = t) u)
-//   Functions:                 (Function (x : t) u)
-//   Self-applicable functions  (SFunction (x) t)
-//
-// If a variable occurs in any other location, it is a reference to an existing
-// variable declaration -- e.g. 'x' in (x * y + z). To save space, we don't
-// allocate a separate AST node for variable references; a reference is just a
-// pointer to the original declaration.
+/// A named variable, e.g. "x".
+///
+/// There are two distinct places in which a Variable can appear in the AST.
+/// A variable declaration introduces a new variable, and can occur in 3 places:
+///   Let-expressions:           (Let (x = t) u)
+///   Functions:                 (Function (x : t) u)
+///   Self-applicable functions  (SFunction (x) t)
+///
+/// If a variable occurs in any other location, it is a reference to an existing
+/// variable declaration -- e.g. 'x' in (x * y + z). To save space, we don't
+/// allocate a separate AST node for variable references; a reference is just a
+/// pointer to the original declaration.
 class Variable : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Variable; }
 
-  // Let-variable, function parameter, or self-variable
   enum VariableKind {
-    VK_Let,
-    VK_LetBB,
-    VK_Fun,
-    VK_SFun
+    VK_Let,  ///< Let-variable
+    VK_Fun,  ///< Function parameter
+    VK_SFun  ///< SFunction (self) parameter
   };
 
-  // These are defined after SExprRef contructor, below
-  inline Variable(SExpr *D, const clang::ValueDecl *Cvd = nullptr);
-  inline Variable(StringRef s, SExpr *D = nullptr);
-  inline Variable(const Variable &Vd, SExpr *D);
+  Variable(StringRef s, SExpr *D = nullptr)
+      : SExpr(COP_Variable), Name(s), Definition(D), Cvdecl(nullptr) {
+    Flags = VK_Let;
+  }
+  Variable(SExpr *D, const clang::ValueDecl *Cvd = nullptr)
+      : SExpr(COP_Variable), Name(Cvd ? Cvd->getName() : "_x"),
+        Definition(D), Cvdecl(Cvd) {
+    Flags = VK_Let;
+  }
+  Variable(const Variable &Vd, SExpr *D)  // rewrite constructor
+      : SExpr(Vd), Name(Vd.Name), Definition(D), Cvdecl(Vd.Cvdecl) {
+    Flags = Vd.kind();
+  }
 
+  /// Return the kind of variable (let, function param, or self)
   VariableKind kind() const { return static_cast<VariableKind>(Flags); }
 
+  /// Return the name of the variable, if any.
   StringRef name() const { return Name; }
+
+  /// Return the clang declaration for this variable, if any.
   const clang::ValueDecl *clangDecl() const { return Cvdecl; }
 
-  // Returns the definition (for let vars) or type (for parameter & self vars)
-  SExpr *definition() { return Definition.get(); }
-  const SExpr *definition() const { return Definition.get(); }
-
-  void attachVar() const { ++NumUses; }
-  void detachVar() const { assert(NumUses > 0); --NumUses; }
-
-  unsigned getID() const { return Id; }
-  unsigned getBlockID() const { return BlockID; }
-
-  void setName(StringRef S) { Name = S; }
-  void setID(unsigned Bid, unsigned I) {
-    BlockID = static_cast<unsigned short>(Bid);
-    Id = static_cast<unsigned short>(I);
-  }
-  void setClangDecl(const clang::ValueDecl *VD) { Cvdecl = VD; }
-  void setDefinition(SExpr *E);
+  /// Return the definition of the variable.
+  /// For let-vars, this is the setting expression.
+  /// For function and self parameters, it is the type of the variable.
+  SExpr *definition() { return Definition; }
+  const SExpr *definition() const { return Definition; }
+
+  void setName(StringRef S)    { Name = S;  }
   void setKind(VariableKind K) { Flags = K; }
+  void setDefinition(SExpr *E) { Definition = E; }
+  void setClangDecl(const clang::ValueDecl *VD) { Cvdecl = VD; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -418,17 +405,13 @@ private:
   friend class Let;
 
   StringRef Name;                  // The name of the variable.
-  SExprRef  Definition;            // The TIL type or definition
+  SExpr*    Definition;            // The TIL type or definition
   const clang::ValueDecl *Cvdecl;  // The clang declaration for this variable.
-
-  unsigned short BlockID;
-  unsigned short Id;
-  mutable unsigned NumUses;
 };
 
 
-// Placeholder for an expression that has not yet been created.
-// Used to implement lazy copy and rewriting strategies.
+/// Placeholder for an expression that has not yet been created.
+/// Used to implement lazy copy and rewriting strategies.
 class Future : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Future; }
@@ -439,22 +422,14 @@ public:
     FS_done
   };
 
-  Future() :
-    SExpr(COP_Future), Status(FS_pending), Result(nullptr), Location(nullptr)
-  {}
+  Future() : SExpr(COP_Future), Status(FS_pending), Result(nullptr) {}
+
 private:
   virtual ~Future() LLVM_DELETED_FUNCTION;
-public:
-
-  // Registers the location in the AST where this future is stored.
-  // Forcing the future will automatically update the AST.
-  static inline void registerLocation(SExprRef *Member) {
-    if (Future *F = dyn_cast_or_null<Future>(Member->get()))
-      F->Location = Member;
-  }
 
+public:
   // A lazy rewriting strategy should subclass Future and override this method.
-  virtual SExpr *create() { return nullptr; }
+  virtual SExpr *compute() { return nullptr; }
 
   // Return the result of this future if it exists, otherwise return null.
   SExpr *maybeGetResult() const {
@@ -465,8 +440,7 @@ public:
   SExpr *result() {
     switch (Status) {
     case FS_pending:
-      force();
-      return Result;
+      return force();
     case FS_evaluating:
       return nullptr; // infinite loop; illegal recursion.
     case FS_done:
@@ -488,81 +462,14 @@ public:
   }
 
 private:
-  // Force the future.
-  inline void force();
+  SExpr* force();
 
   FutureStatus Status;
   SExpr *Result;
-  SExprRef *Location;
 };
 
 
-inline void SExprRef::attach() {
-  if (!Ptr)
-    return;
-
-  TIL_Opcode Op = Ptr->opcode();
-  if (Op == COP_Variable) {
-    cast<Variable>(Ptr)->attachVar();
-  } else if (Op == COP_Future) {
-    cast<Future>(Ptr)->registerLocation(this);
-  }
-}
-
-inline void SExprRef::detach() {
-  if (Ptr && Ptr->opcode() == COP_Variable) {
-    cast<Variable>(Ptr)->detachVar();
-  }
-}
-
-inline SExprRef::SExprRef(SExpr *P) : Ptr(P) {
-  attach();
-}
-
-inline SExprRef::~SExprRef() {
-  detach();
-}
-
-inline void SExprRef::reset(SExpr *P) {
-  detach();
-  Ptr = P;
-  attach();
-}
-
-
-inline Variable::Variable(StringRef s, SExpr *D)
-    : SExpr(COP_Variable), Name(s), Definition(D), Cvdecl(nullptr),
-      BlockID(0), Id(0), NumUses(0) {
-  Flags = VK_Let;
-}
-
-inline Variable::Variable(SExpr *D, const clang::ValueDecl *Cvd)
-    : SExpr(COP_Variable), Name(Cvd ? Cvd->getName() : "_x"),
-      Definition(D), Cvdecl(Cvd), BlockID(0), Id(0), NumUses(0) {
-  Flags = VK_Let;
-}
-
-inline Variable::Variable(const Variable &Vd, SExpr *D) // rewrite constructor
-    : SExpr(Vd), Name(Vd.Name), Definition(D), Cvdecl(Vd.Cvdecl),
-      BlockID(0), Id(0), NumUses(0) {
-  Flags = Vd.kind();
-}
-
-inline void Variable::setDefinition(SExpr *E) {
-  Definition.reset(E);
-}
-
-void Future::force() {
-  Status = FS_evaluating;
-  SExpr *R = create();
-  Result = R;
-  if (Location)
-    Location->reset(R);
-  Status = FS_done;
-}
-
-
-// Placeholder for C++ expressions that cannot be represented in the TIL.
+/// Placeholder for expressions that cannot be represented in the TIL.
 class Undefined : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Undefined; }
@@ -585,7 +492,7 @@ private:
 };
 
 
-// Placeholder for a wildcard that matches any other expression.
+/// Placeholder for a wildcard that matches any other expression.
 class Wildcard : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Wildcard; }
@@ -716,8 +623,8 @@ typename V::R_SExpr Literal::traverse(V
 }
 
 
-// Literal pointer to an object allocated in memory.
-// At compile time, pointer literals are represented by symbolic names.
+/// A Literal pointer to an object allocated in memory.
+/// At compile time, pointer literals are represented by symbolic names.
 class LiteralPtr : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_LiteralPtr; }
@@ -743,9 +650,9 @@ private:
 };
 
 
-// A function -- a.k.a. lambda abstraction.
-// Functions with multiple arguments are created by currying,
-// e.g. (function (x: Int) (function (y: Int) (add x y)))
+/// A function -- a.k.a. lambda abstraction.
+/// Functions with multiple arguments are created by currying,
+/// e.g. (Function (x: Int) (Function (y: Int) (Code { return x + y })))
 class Function : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Function; }
@@ -762,8 +669,8 @@ public:
   Variable *variableDecl()  { return VarDecl; }
   const Variable *variableDecl() const { return VarDecl; }
 
-  SExpr *body() { return Body.get(); }
-  const SExpr *body() const { return Body.get(); }
+  SExpr *body() { return Body; }
+  const SExpr *body() const { return Body; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -790,13 +697,13 @@ public:
 
 private:
   Variable *VarDecl;
-  SExprRef Body;
+  SExpr* Body;
 };
 
 
-// A self-applicable function.
-// A self-applicable function can be applied to itself.  It's useful for
-// implementing objects and late binding
+/// A self-applicable function.
+/// A self-applicable function can be applied to itself.  It's useful for
+/// implementing objects and late binding.
 class SFunction : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_SFunction; }
@@ -805,20 +712,20 @@ public:
       : SExpr(COP_SFunction), VarDecl(Vd), Body(B) {
     assert(Vd->Definition == nullptr);
     Vd->setKind(Variable::VK_SFun);
-    Vd->Definition.reset(this);
+    Vd->Definition = this;
   }
   SFunction(const SFunction &F, Variable *Vd, SExpr *B) // rewrite constructor
       : SExpr(F), VarDecl(Vd), Body(B) {
     assert(Vd->Definition == nullptr);
     Vd->setKind(Variable::VK_SFun);
-    Vd->Definition.reset(this);
+    Vd->Definition = this;
   }
 
   Variable *variableDecl() { return VarDecl; }
   const Variable *variableDecl() const { return VarDecl; }
 
-  SExpr *body() { return Body.get(); }
-  const SExpr *body() const { return Body.get(); }
+  SExpr *body() { return Body; }
+  const SExpr *body() const { return Body; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -842,11 +749,11 @@ public:
 
 private:
   Variable *VarDecl;
-  SExprRef Body;
+  SExpr* Body;
 };
 
 
-// A block of code -- e.g. the body of a function.
+/// A block of code -- e.g. the body of a function.
 class Code : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Code; }
@@ -855,11 +762,11 @@ public:
   Code(const Code &C, SExpr *T, SExpr *B) // rewrite constructor
       : SExpr(C), ReturnType(T), Body(B) {}
 
-  SExpr *returnType() { return ReturnType.get(); }
-  const SExpr *returnType() const { return ReturnType.get(); }
+  SExpr *returnType() { return ReturnType; }
+  const SExpr *returnType() const { return ReturnType; }
 
-  SExpr *body() { return Body.get(); }
-  const SExpr *body() const { return Body.get(); }
+  SExpr *body() { return Body; }
+  const SExpr *body() const { return Body; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -877,12 +784,12 @@ public:
   }
 
 private:
-  SExprRef ReturnType;
-  SExprRef Body;
+  SExpr* ReturnType;
+  SExpr* Body;
 };
 
 
-// A typed, writable location in memory
+/// A typed, writable location in memory
 class Field : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Field; }
@@ -891,11 +798,11 @@ public:
   Field(const Field &C, SExpr *R, SExpr *B) // rewrite constructor
       : SExpr(C), Range(R), Body(B) {}
 
-  SExpr *range() { return Range.get(); }
-  const SExpr *range() const { return Range.get(); }
+  SExpr *range() { return Range; }
+  const SExpr *range() const { return Range; }
 
-  SExpr *body() { return Body.get(); }
-  const SExpr *body() const { return Body.get(); }
+  SExpr *body() { return Body; }
+  const SExpr *body() const { return Body; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -913,12 +820,16 @@ public:
   }
 
 private:
-  SExprRef Range;
-  SExprRef Body;
+  SExpr* Range;
+  SExpr* Body;
 };
 
 
-// Apply an argument to a function
+/// Apply an argument to a function.
+/// Note that this does not actually call the function.  Functions are curried,
+/// so this returns a closure in which the first parameter has been applied.
+/// Once all parameters have been applied, Call can be used to invoke the
+/// function.
 class Apply : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Apply; }
@@ -928,11 +839,11 @@ public:
       : SExpr(A), Fun(F), Arg(Ar)
   {}
 
-  SExpr *fun() { return Fun.get(); }
-  const SExpr *fun() const { return Fun.get(); }
+  SExpr *fun() { return Fun; }
+  const SExpr *fun() const { return Fun; }
 
-  SExpr *arg() { return Arg.get(); }
-  const SExpr *arg() const { return Arg.get(); }
+  SExpr *arg() { return Arg; }
+  const SExpr *arg() const { return Arg; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -950,12 +861,12 @@ public:
   }
 
 private:
-  SExprRef Fun;
-  SExprRef Arg;
+  SExpr* Fun;
+  SExpr* Arg;
 };
 
 
-// Apply a self-argument to a self-applicable function
+/// Apply a self-argument to a self-applicable function.
 class SApply : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_SApply; }
@@ -964,18 +875,18 @@ public:
   SApply(SApply &A, SExpr *Sf, SExpr *Ar = nullptr) // rewrite constructor
       : SExpr(A), Sfun(Sf), Arg(Ar) {}
 
-  SExpr *sfun() { return Sfun.get(); }
-  const SExpr *sfun() const { return Sfun.get(); }
+  SExpr *sfun() { return Sfun; }
+  const SExpr *sfun() const { return Sfun; }
 
-  SExpr *arg() { return Arg.get() ? Arg.get() : Sfun.get(); }
-  const SExpr *arg() const { return Arg.get() ? Arg.get() : Sfun.get(); }
+  SExpr *arg() { return Arg ? Arg : Sfun; }
+  const SExpr *arg() const { return Arg ? Arg : Sfun; }
 
   bool isDelegation() const { return Arg != nullptr; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
     auto Nf = Vs.traverse(Sfun, Vs.subExprCtx(Ctx));
-    typename V::R_SExpr Na = Arg.get() ? Vs.traverse(Arg, Vs.subExprCtx(Ctx))
+    typename V::R_SExpr Na = Arg ? Vs.traverse(Arg, Vs.subExprCtx(Ctx))
                                        : nullptr;
     return Vs.reduceSApply(*this, Nf, Na);
   }
@@ -989,12 +900,12 @@ public:
   }
 
 private:
-  SExprRef Sfun;
-  SExprRef Arg;
+  SExpr* Sfun;
+  SExpr* Arg;
 };
 
 
-// Project a named slot from a C++ struct or class.
+/// Project a named slot from a C++ struct or class.
 class Project : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Project; }
@@ -1009,8 +920,8 @@ public:
       : SExpr(P), Rec(R), SlotName(P.SlotName), Cvdecl(P.Cvdecl)
   { }
 
-  SExpr *record() { return Rec.get(); }
-  const SExpr *record() const { return Rec.get(); }
+  SExpr *record() { return Rec; }
+  const SExpr *record() const { return Rec; }
 
   const clang::ValueDecl *clangDecl() const { return Cvdecl; }
 
@@ -1042,13 +953,13 @@ public:
   }
 
 private:
-  SExprRef Rec;
+  SExpr* Rec;
   StringRef SlotName;
   const clang::ValueDecl *Cvdecl;
 };
 
 
-// Call a function (after all arguments have been applied).
+/// Call a function (after all arguments have been applied).
 class Call : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Call; }
@@ -1057,8 +968,8 @@ public:
       : SExpr(COP_Call), Target(T), Cexpr(Ce) {}
   Call(const Call &C, SExpr *T) : SExpr(C), Target(T), Cexpr(C.Cexpr) {}
 
-  SExpr *target() { return Target.get(); }
-  const SExpr *target() const { return Target.get(); }
+  SExpr *target() { return Target; }
+  const SExpr *target() const { return Target; }
 
   const clang::CallExpr *clangCallExpr() const { return Cexpr; }
 
@@ -1074,12 +985,12 @@ public:
   }
 
 private:
-  SExprRef Target;
+  SExpr* Target;
   const clang::CallExpr *Cexpr;
 };
 
 
-// Allocate memory for a new value on the heap or stack.
+/// Allocate memory for a new value on the heap or stack.
 class Alloc : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Call; }
@@ -1094,8 +1005,8 @@ public:
 
   AllocKind kind() const { return static_cast<AllocKind>(Flags); }
 
-  SExpr *dataType() { return Dtype.get(); }
-  const SExpr *dataType() const { return Dtype.get(); }
+  SExpr *dataType() { return Dtype; }
+  const SExpr *dataType() const { return Dtype; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1112,11 +1023,11 @@ public:
   }
 
 private:
-  SExprRef Dtype;
+  SExpr* Dtype;
 };
 
 
-// Load a value from memory.
+/// Load a value from memory.
 class Load : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Load; }
@@ -1124,8 +1035,8 @@ public:
   Load(SExpr *P) : SExpr(COP_Load), Ptr(P) {}
   Load(const Load &L, SExpr *P) : SExpr(L), Ptr(P) {}
 
-  SExpr *pointer() { return Ptr.get(); }
-  const SExpr *pointer() const { return Ptr.get(); }
+  SExpr *pointer() { return Ptr; }
+  const SExpr *pointer() const { return Ptr; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1139,12 +1050,12 @@ public:
   }
 
 private:
-  SExprRef Ptr;
+  SExpr* Ptr;
 };
 
 
-// Store a value to memory.
-// Source is a pointer, destination is the value to store.
+/// Store a value to memory.
+/// The destination is a pointer to a field, the source is the value to store.
 class Store : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Store; }
@@ -1152,11 +1063,11 @@ public:
   Store(SExpr *P, SExpr *V) : SExpr(COP_Store), Dest(P), Source(V) {}
   Store(const Store &S, SExpr *P, SExpr *V) : SExpr(S), Dest(P), Source(V) {}
 
-  SExpr *destination() { return Dest.get(); }  // Address to store to
-  const SExpr *destination() const { return Dest.get(); }
+  SExpr *destination() { return Dest; }  // Address to store to
+  const SExpr *destination() const { return Dest; }
 
-  SExpr *source() { return Source.get(); }     // Value to store
-  const SExpr *source() const { return Source.get(); }
+  SExpr *source() { return Source; }     // Value to store
+  const SExpr *source() const { return Source; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1174,13 +1085,13 @@ public:
   }
 
 private:
-  SExprRef Dest;
-  SExprRef Source;
+  SExpr* Dest;
+  SExpr* Source;
 };
 
 
-// If p is a reference to an array, then first(p) is a reference to the first
-// element.  The usual array notation p[i]  becomes first(p + i).
+/// If p is a reference to an array, then p[i] is a reference to the i'th
+/// element of the array.
 class ArrayIndex : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_ArrayIndex; }
@@ -1189,11 +1100,11 @@ public:
   ArrayIndex(const ArrayIndex &E, SExpr *A, SExpr *N)
     : SExpr(E), Array(A), Index(N) {}
 
-  SExpr *array() { return Array.get(); }
-  const SExpr *array() const { return Array.get(); }
+  SExpr *array() { return Array; }
+  const SExpr *array() const { return Array; }
 
-  SExpr *index() { return Index.get(); }
-  const SExpr *index() const { return Index.get(); }
+  SExpr *index() { return Index; }
+  const SExpr *index() const { return Index; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1211,14 +1122,14 @@ public:
   }
 
 private:
-  SExprRef Array;
-  SExprRef Index;
+  SExpr* Array;
+  SExpr* Index;
 };
 
 
-// Pointer arithmetic, restricted to arrays only.
-// If p is a reference to an array, then p + n, where n is an integer, is
-// a reference to a subarray.
+/// Pointer arithmetic, restricted to arrays only.
+/// If p is a reference to an array, then p + n, where n is an integer, is
+/// a reference to a subarray.
 class ArrayAdd : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_ArrayAdd; }
@@ -1227,11 +1138,11 @@ public:
   ArrayAdd(const ArrayAdd &E, SExpr *A, SExpr *N)
     : SExpr(E), Array(A), Index(N) {}
 
-  SExpr *array() { return Array.get(); }
-  const SExpr *array() const { return Array.get(); }
+  SExpr *array() { return Array; }
+  const SExpr *array() const { return Array; }
 
-  SExpr *index() { return Index.get(); }
-  const SExpr *index() const { return Index.get(); }
+  SExpr *index() { return Index; }
+  const SExpr *index() const { return Index; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1249,12 +1160,13 @@ public:
   }
 
 private:
-  SExprRef Array;
-  SExprRef Index;
+  SExpr* Array;
+  SExpr* Index;
 };
 
 
-// Simple unary operation -- e.g. !, ~, etc.
+/// Simple arithmetic unary operations, e.g. negate and not.
+/// These operations have no side-effects.
 class UnaryOp : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_UnaryOp; }
@@ -1268,8 +1180,8 @@ public:
     return static_cast<TIL_UnaryOpcode>(Flags);
   }
 
-  SExpr *expr() { return Expr0.get(); }
-  const SExpr *expr() const { return Expr0.get(); }
+  SExpr *expr() { return Expr0; }
+  const SExpr *expr() const { return Expr0; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1287,11 +1199,12 @@ public:
   }
 
 private:
-  SExprRef Expr0;
+  SExpr* Expr0;
 };
 
 
-// Simple binary operation -- e.g. +, -, etc.
+/// Simple arithmetic binary operations, e.g. +, -, etc.
+/// These operations have no side effects.
 class BinaryOp : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_BinaryOp; }
@@ -1309,11 +1222,11 @@ public:
     return static_cast<TIL_BinaryOpcode>(Flags);
   }
 
-  SExpr *expr0() { return Expr0.get(); }
-  const SExpr *expr0() const { return Expr0.get(); }
+  SExpr *expr0() { return Expr0; }
+  const SExpr *expr0() const { return Expr0; }
 
-  SExpr *expr1() { return Expr1.get(); }
-  const SExpr *expr1() const { return Expr1.get(); }
+  SExpr *expr1() { return Expr1; }
+  const SExpr *expr1() const { return Expr1; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1335,12 +1248,14 @@ public:
   }
 
 private:
-  SExprRef Expr0;
-  SExprRef Expr1;
+  SExpr* Expr0;
+  SExpr* Expr1;
 };
 
 
-// Cast expression
+/// Cast expressions.
+/// Cast expressions are essentially unary operations, but we treat them
+/// as a distinct AST node because they only change the type of the result.
 class Cast : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Cast; }
@@ -1352,8 +1267,8 @@ public:
     return static_cast<TIL_CastOpcode>(Flags);
   }
 
-  SExpr *expr() { return Expr0.get(); }
-  const SExpr *expr() const { return Expr0.get(); }
+  SExpr *expr() { return Expr0; }
+  const SExpr *expr() const { return Expr0; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1371,16 +1286,18 @@ public:
   }
 
 private:
-  SExprRef Expr0;
+  SExpr* Expr0;
 };
 
 
 class SCFG;
 
 
+/// Phi Node, for code in SSA form.
+/// Each Phi node has an array of possible values that it can take,
+/// depending on where control flow comes from.
 class Phi : public SExpr {
 public:
-  // TODO: change to SExprRef
   typedef SimpleArray<SExpr *> ValArray;
 
   // In minimal SSA form, all Phi nodes are MultiVal.
@@ -1394,9 +1311,12 @@ public:
 
   static bool classof(const SExpr *E) { return E->opcode() == COP_Phi; }
 
-  Phi() : SExpr(COP_Phi) {}
-  Phi(MemRegionRef A, unsigned Nvals) : SExpr(COP_Phi), Values(A, Nvals) {}
-  Phi(const Phi &P, ValArray &&Vs)    : SExpr(P), Values(std::move(Vs)) {}
+  Phi()
+    : SExpr(COP_Phi), Cvdecl(nullptr) {}
+  Phi(MemRegionRef A, unsigned Nvals)
+    : SExpr(COP_Phi), Values(A, Nvals), Cvdecl(nullptr)  {}
+  Phi(const Phi &P, ValArray &&Vs)
+    : SExpr(P), Values(std::move(Vs)), Cvdecl(nullptr) {}
 
   const ValArray &values() const { return Values; }
   ValArray &values() { return Values; }
@@ -1404,6 +1324,12 @@ public:
   Status status() const { return static_cast<Status>(Flags); }
   void setStatus(Status s) { Flags = s; }
 
+  /// Return the clang declaration of the variable for this Phi node, if any.
+  const clang::ValueDecl *clangDecl() const { return Cvdecl; }
+
+  /// Set the clang variable associated with this Phi node.
+  void setClangDecl(const clang::ValueDecl *Cvd) { Cvdecl = Cvd; }
+
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
     typename V::template Container<typename V::R_SExpr>
@@ -1423,65 +1349,260 @@ public:
 
 private:
   ValArray Values;
+  const clang::ValueDecl* Cvdecl;
+};
+
+
+/// Base class for basic block terminators:  Branch, Goto, and Return.
+class Terminator : public SExpr {
+public:
+  static bool classof(const SExpr *E) {
+    return E->opcode() >= COP_Goto && E->opcode() <= COP_Return;
+  }
+
+protected:
+  Terminator(TIL_Opcode Op)  : SExpr(Op) {}
+  Terminator(const SExpr &E) : SExpr(E)  {}
+
+public:
+  /// Return the list of basic blocks that this terminator can branch to.
+  ArrayRef<BasicBlock*> successors();
+
+  ArrayRef<BasicBlock*> successors() const {
+    return const_cast<const Terminator*>(this)->successors();
+  }
+};
+
+
+/// Jump to another basic block.
+/// A goto instruction is essentially a tail-recursive call into another
+/// block.  In addition to the block pointer, it specifies an index into the
+/// phi nodes of that block.  The index can be used to retrieve the "arguments"
+/// of the call.
+class Goto : public Terminator {
+public:
+  static bool classof(const SExpr *E) { return E->opcode() == COP_Goto; }
+
+  Goto(BasicBlock *B, unsigned I)
+      : Terminator(COP_Goto), TargetBlock(B), Index(I) {}
+  Goto(const Goto &G, BasicBlock *B, unsigned I)
+      : Terminator(COP_Goto), TargetBlock(B), Index(I) {}
+
+  const BasicBlock *targetBlock() const { return TargetBlock; }
+  BasicBlock *targetBlock() { return TargetBlock; }
+
+  /// Returns the index into the
+  unsigned index() const { return Index; }
+
+  /// Return the list of basic blocks that this terminator can branch to.
+  ArrayRef<BasicBlock*> successors() {
+    return ArrayRef<BasicBlock*>(&TargetBlock, 1);
+  }
+
+  template <class V>
+  typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
+    BasicBlock *Ntb = Vs.reduceBasicBlockRef(TargetBlock);
+    return Vs.reduceGoto(*this, Ntb);
+  }
+
+  template <class C>
+  typename C::CType compare(const Goto *E, C &Cmp) const {
+    // TODO: implement CFG comparisons
+    return Cmp.comparePointers(this, E);
+  }
+
+private:
+  BasicBlock *TargetBlock;
+  unsigned Index;
+};
+
+
+/// A conditional branch to two other blocks.
+/// Note that unlike Goto, Branch does not have an index.  The target blocks
+/// must be child-blocks, and cannot have Phi nodes.
+class Branch : public Terminator {
+public:
+  static bool classof(const SExpr *E) { return E->opcode() == COP_Branch; }
+
+  Branch(SExpr *C, BasicBlock *T, BasicBlock *E)
+      : Terminator(COP_Branch), Condition(C) {
+    Branches[0] = T;
+    Branches[1] = E;
+  }
+  Branch(const Branch &Br, SExpr *C, BasicBlock *T, BasicBlock *E)
+      : Terminator(Br), Condition(C) {
+    Branches[0] = T;
+    Branches[1] = E;
+  }
+
+  const SExpr *condition() const { return Condition; }
+  SExpr *condition() { return Condition; }
+
+  const BasicBlock *thenBlock() const { return Branches[0]; }
+  BasicBlock *thenBlock() { return Branches[0]; }
+
+  const BasicBlock *elseBlock() const { return Branches[1]; }
+  BasicBlock *elseBlock() { return Branches[1]; }
+
+  /// Return the list of basic blocks that this terminator can branch to.
+  ArrayRef<BasicBlock*> successors() {
+    return ArrayRef<BasicBlock*>(Branches, 2);
+  }
+
+  template <class V>
+  typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
+    auto Nc = Vs.traverse(Condition, Vs.subExprCtx(Ctx));
+    BasicBlock *Ntb = Vs.reduceBasicBlockRef(Branches[0]);
+    BasicBlock *Nte = Vs.reduceBasicBlockRef(Branches[1]);
+    return Vs.reduceBranch(*this, Nc, Ntb, Nte);
+  }
+
+  template <class C>
+  typename C::CType compare(const Branch *E, C &Cmp) const {
+    // TODO: implement CFG comparisons
+    return Cmp.comparePointers(this, E);
+  }
+
+private:
+  SExpr*     Condition;
+  BasicBlock *Branches[2];
+};
+
+
+/// Return from the enclosing function, passing the return value to the caller.
+/// Only the exit block should end with a return statement.
+class Return : public Terminator {
+public:
+  static bool classof(const SExpr *E) { return E->opcode() == COP_Return; }
+
+  Return(SExpr* Rval) : Terminator(COP_Return), Retval(Rval) {}
+  Return(const Return &R, SExpr* Rval) : Terminator(R), Retval(Rval) {}
+
+  /// Return an empty list.
+  ArrayRef<BasicBlock*> successors() {
+    return ArrayRef<BasicBlock*>();
+  }
+
+  SExpr *returnValue() { return Retval; }
+  const SExpr *returnValue() const { return Retval; }
+
+  template <class V>
+  typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
+    auto Ne = Vs.traverse(Retval, Vs.subExprCtx(Ctx));
+    return Vs.reduceReturn(*this, Ne);
+  }
+
+  template <class C>
+  typename C::CType compare(const Return *E, C &Cmp) const {
+    return Cmp.compare(Retval, E->Retval);
+  }
+
+private:
+  SExpr* Retval;
 };
 
 
-// A basic block is part of an SCFG, and can be treated as a function in
-// continuation passing style.  It consists of a sequence of phi nodes, which
-// are "arguments" to the function, followed by a sequence of instructions.
-// Both arguments and instructions define new variables.  It ends with a
-// branch or goto to another basic block in the same SCFG.
+inline ArrayRef<BasicBlock*> Terminator::successors() {
+  switch (opcode()) {
+    case COP_Goto:   return cast<Goto>(this)->successors();
+    case COP_Branch: return cast<Branch>(this)->successors();
+    case COP_Return: return cast<Return>(this)->successors();
+    default:
+      return ArrayRef<BasicBlock*>();
+  }
+}
+
+
+/// A basic block is part of an SCFG.  It can be treated as a function in
+/// continuation passing style.  A block consists of a sequence of phi nodes,
+/// which are "arguments" to the function, followed by a sequence of
+/// instructions.  It ends with a Terminator, which is a Branch or Goto to
+/// another basic block in the same SCFG.
 class BasicBlock : public SExpr {
 public:
-  typedef SimpleArray<Variable*>   VarArray;
+  typedef SimpleArray<SExpr*>      InstrArray;
   typedef SimpleArray<BasicBlock*> BlockArray;
 
+  // TopologyNodes are used to overlay tree structures on top of the CFG,
+  // such as dominator and postdominator trees.  Each block is assigned an
+  // ID in the tree according to a depth-first search.  Tree traversals are
+  // always up, towards the parents.
+  struct TopologyNode {
+    TopologyNode() : NodeID(0), SizeOfSubTree(0), Parent(nullptr) {}
+
+    bool isParentOf(const TopologyNode& OtherNode) {
+      return OtherNode.NodeID > NodeID &&
+             OtherNode.NodeID < NodeID + SizeOfSubTree;
+    }
+
+    bool isParentOfOrEqual(const TopologyNode& OtherNode) {
+      return OtherNode.NodeID >= NodeID &&
+             OtherNode.NodeID < NodeID + SizeOfSubTree;
+    }
+
+    int NodeID;
+    int SizeOfSubTree;    // Includes this node, so must be > 1.
+    BasicBlock *Parent;   // Pointer to parent.
+  };
+
   static bool classof(const SExpr *E) { return E->opcode() == COP_BasicBlock; }
 
-  explicit BasicBlock(MemRegionRef A, BasicBlock* P = nullptr)
+  explicit BasicBlock(MemRegionRef A)
       : SExpr(COP_BasicBlock), Arena(A), CFGPtr(nullptr), BlockID(0),
-        Parent(P), Terminator(nullptr)
-  { }
-  BasicBlock(BasicBlock &B, VarArray &&As, VarArray &&Is, SExpr *T)
-      : SExpr(COP_BasicBlock), Arena(B.Arena), CFGPtr(nullptr), BlockID(0),
-        Parent(nullptr), Args(std::move(As)), Instrs(std::move(Is)),
-        Terminator(T)
-  { }
-
-  unsigned blockID() const { return BlockID; }
-  unsigned numPredecessors() const { return Predecessors.size(); }
+        Visited(0), TermInstr(nullptr) {}
+  BasicBlock(BasicBlock &B, MemRegionRef A, InstrArray &&As, InstrArray &&Is,
+             Terminator *T)
+      : SExpr(COP_BasicBlock), Arena(A), CFGPtr(nullptr), BlockID(0),Visited(0),
+        Args(std::move(As)), Instrs(std::move(Is)), TermInstr(T) {}
+
+  /// Returns the block ID.  Every block has a unique ID in the CFG.
+  int blockID() const { return BlockID; }
+
+  /// Returns the number of predecessors.
+  size_t numPredecessors() const { return Predecessors.size(); }
+  size_t numSuccessors() const { return successors().size(); }
 
   const SCFG* cfg() const { return CFGPtr; }
   SCFG* cfg() { return CFGPtr; }
 
-  const BasicBlock *parent() const { return Parent; }
-  BasicBlock *parent() { return Parent; }
+  const BasicBlock *parent() const { return DominatorNode.Parent; }
+  BasicBlock *parent() { return DominatorNode.Parent; }
 
-  const VarArray &arguments() const { return Args; }
-  VarArray &arguments() { return Args; }
+  const InstrArray &arguments() const { return Args; }
+  InstrArray &arguments() { return Args; }
 
-  const VarArray &instructions() const { return Instrs; }
-  VarArray &instructions() { return Instrs; }
+  InstrArray &instructions() { return Instrs; }
+  const InstrArray &instructions() const { return Instrs; }
 
-  const BlockArray &predecessors() const { return Predecessors; }
+  /// Returns a list of predecessors.
+  /// The order of predecessors in the list is important; each phi node has
+  /// exactly one argument for each precessor, in the same order.
   BlockArray &predecessors() { return Predecessors; }
+  const BlockArray &predecessors() const { return Predecessors; }
+
+  ArrayRef<BasicBlock*> successors() { return TermInstr->successors(); }
+  ArrayRef<BasicBlock*> successors() const { return TermInstr->successors(); }
 
-  const SExpr *terminator() const { return Terminator.get(); }
-  SExpr *terminator() { return Terminator.get(); }
+  const Terminator *terminator() const { return TermInstr; }
+  Terminator *terminator() { return TermInstr; }
 
-  void setBlockID(unsigned i)   { BlockID = i; }
-  void setParent(BasicBlock *P) { Parent = P;  }
-  void setTerminator(SExpr *E)  { Terminator.reset(E); }
-
-  // Add a new argument.  V must define a phi-node.
-  void addArgument(Variable *V) {
-    V->setKind(Variable::VK_LetBB);
+  void setTerminator(Terminator *E) { TermInstr = E; }
+
+  bool Dominates(const BasicBlock &Other) {
+    return DominatorNode.isParentOfOrEqual(Other.DominatorNode);
+  }
+
+  bool PostDominates(const BasicBlock &Other) {
+    return PostDominatorNode.isParentOfOrEqual(Other.PostDominatorNode);
+  }
+
+  /// Add a new argument.
+  void addArgument(Phi *V) {
     Args.reserveCheck(1, Arena);
     Args.push_back(V);
   }
-  // Add a new instruction.
-  void addInstruction(Variable *V) {
-    V->setKind(Variable::VK_LetBB);
+  /// Add a new instruction.
+  void addInstruction(SExpr *V) {
     Instrs.reserveCheck(1, Arena);
     Instrs.push_back(V);
   }
@@ -1498,34 +1619,29 @@ public:
   // Reserve space for NumPreds predecessors, including space in phi nodes.
   void reservePredecessors(unsigned NumPreds);
 
-  // Return the index of BB, or Predecessors.size if BB is not a predecessor.
+  /// Return the index of BB, or Predecessors.size if BB is not a predecessor.
   unsigned findPredecessorIndex(const BasicBlock *BB) const {
     auto I = std::find(Predecessors.cbegin(), Predecessors.cend(), BB);
     return std::distance(Predecessors.cbegin(), I);
   }
 
-  // Set id numbers for variables.
-  void renumberVars();
-
   template <class V>
   typename V::R_BasicBlock traverse(V &Vs, typename V::R_Ctx Ctx) {
-    typename V::template Container<Variable*> Nas(Vs, Args.size());
-    typename V::template Container<Variable*> Nis(Vs, Instrs.size());
+    typename V::template Container<SExpr*> Nas(Vs, Args.size());
+    typename V::template Container<SExpr*> Nis(Vs, Instrs.size());
 
     // Entering the basic block should do any scope initialization.
     Vs.enterBasicBlock(*this);
 
-    for (auto *A : Args) {
-      auto Ne = Vs.traverse(A->Definition, Vs.subExprCtx(Ctx));
-      Variable *Nvd = Vs.enterScope(*A, Ne);
-      Nas.push_back(Nvd);
+    for (auto *E : Args) {
+      auto Ne = Vs.traverse(E, Vs.subExprCtx(Ctx));
+      Nas.push_back(Ne);
     }
-    for (auto *I : Instrs) {
-      auto Ne = Vs.traverse(I->Definition, Vs.subExprCtx(Ctx));
-      Variable *Nvd = Vs.enterScope(*I, Ne);
-      Nis.push_back(Nvd);
+    for (auto *E : Instrs) {
+      auto Ne = Vs.traverse(E, Vs.subExprCtx(Ctx));
+      Nis.push_back(Ne);
     }
-    auto Nt = Vs.traverse(Terminator, Ctx);
+    auto Nt = Vs.traverse(TermInstr, Ctx);
 
     // Exiting the basic block should handle any scope cleanup.
     Vs.exitBasicBlock(*this);
@@ -1542,22 +1658,32 @@ public:
 private:
   friend class SCFG;
 
-  MemRegionRef Arena;
-
-  SCFG       *CFGPtr;       // The CFG that contains this block.
-  unsigned   BlockID;       // unique id for this BB in the containing CFG
-  BasicBlock *Parent;       // The parent block is the enclosing lexical scope.
-                            // The parent dominates this block.
-  BlockArray Predecessors;  // Predecessor blocks in the CFG.
-  VarArray   Args;          // Phi nodes.  One argument per predecessor.
-  VarArray   Instrs;        // Instructions.
-  SExprRef   Terminator;    // Branch or Goto
+  int  renumberInstrs(int id);  // assign unique ids to all instructions
+  int  topologicalSort(SimpleArray<BasicBlock*>& Blocks, int ID);
+  int  topologicalFinalSort(SimpleArray<BasicBlock*>& Blocks, int ID);
+  void computeDominator();
+  void computePostDominator();
+
+private:
+  MemRegionRef Arena;        // The arena used to allocate this block.
+  SCFG         *CFGPtr;      // The CFG that contains this block.
+  int          BlockID : 31; // unique id for this BB in the containing CFG.
+                             // IDs are in topological order.
+  int          Visited : 1;  // Bit to determine if a block has been visited
+                             // during a traversal.
+  BlockArray  Predecessors;  // Predecessor blocks in the CFG.
+  InstrArray  Args;          // Phi nodes.  One argument per predecessor.
+  InstrArray  Instrs;        // Instructions.
+  Terminator* TermInstr;     // Terminating instruction
+
+  TopologyNode DominatorNode;       // The dominator tree
+  TopologyNode PostDominatorNode;   // The post-dominator tree
 };
 
 
-// An SCFG is a control-flow graph.  It consists of a set of basic blocks, each
-// of which terminates in a branch to another basic block.  There is one
-// entry point, and one exit point.
+/// An SCFG is a control-flow graph.  It consists of a set of basic blocks,
+/// each of which terminates in a branch to another basic block.  There is one
+/// entry point, and one exit point.
 class SCFG : public SExpr {
 public:
   typedef SimpleArray<BasicBlock *> BlockArray;
@@ -1568,20 +1694,29 @@ public:
 
   SCFG(MemRegionRef A, unsigned Nblocks)
     : SExpr(COP_SCFG), Arena(A), Blocks(A, Nblocks),
-      Entry(nullptr), Exit(nullptr) {
-    Entry = new (A) BasicBlock(A, nullptr);
-    Exit  = new (A) BasicBlock(A, Entry);
-    auto *V = new (A) Variable(new (A) Phi());
+      Entry(nullptr), Exit(nullptr), NumInstructions(0), Normal(false) {
+    Entry = new (A) BasicBlock(A);
+    Exit  = new (A) BasicBlock(A);
+    auto *V = new (A) Phi();
     Exit->addArgument(V);
+    Exit->setTerminator(new (A) Return(V));
     add(Entry);
     add(Exit);
   }
   SCFG(const SCFG &Cfg, BlockArray &&Ba) // steals memory from Ba
       : SExpr(COP_SCFG), Arena(Cfg.Arena), Blocks(std::move(Ba)),
-        Entry(nullptr), Exit(nullptr) {
+        Entry(nullptr), Exit(nullptr), NumInstructions(0), Normal(false) {
     // TODO: set entry and exit!
   }
 
+  /// Return true if this CFG is valid.
+  bool valid() const { return Entry && Exit && Blocks.size() > 0; }
+
+  /// Return true if this CFG has been normalized.
+  /// After normalization, blocks are in topological order, and block and
+  /// instruction IDs have been assigned.
+  bool normal() const { return Normal; }
+
   iterator begin() { return Blocks.begin(); }
   iterator end() { return Blocks.end(); }
 
@@ -1596,9 +1731,17 @@ public:
   const BasicBlock *exit() const { return Exit; }
   BasicBlock *exit() { return Exit; }
 
+  /// Return the number of blocks in the CFG.
+  /// Block::blockID() will return a number less than numBlocks();
+  size_t numBlocks() const { return Blocks.size(); }
+
+  /// Return the total number of instructions in the CFG.
+  /// This is useful for building instruction side-tables;
+  /// A call to SExpr::id() will return a number less than numInstructions().
+  unsigned numInstructions() { return NumInstructions; }
+
   inline void add(BasicBlock *BB) {
-    assert(BB->CFGPtr == nullptr || BB->CFGPtr == this);
-    BB->setBlockID(Blocks.size());
+    assert(BB->CFGPtr == nullptr);
     BB->CFGPtr = this;
     Blocks.reserveCheck(1, Arena);
     Blocks.push_back(BB);
@@ -1607,13 +1750,13 @@ public:
   void setEntry(BasicBlock *BB) { Entry = BB; }
   void setExit(BasicBlock *BB)  { Exit = BB;  }
 
-  // Set varable ids in all blocks.
-  void renumberVars();
+  void computeNormalForm();
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
     Vs.enterCFG(*this);
     typename V::template Container<BasicBlock *> Bbs(Vs, Blocks.size());
+
     for (auto *B : Blocks) {
       Bbs.push_back( B->traverse(Vs, Vs.subExprCtx(Ctx)) );
     }
@@ -1623,101 +1766,26 @@ public:
 
   template <class C>
   typename C::CType compare(const SCFG *E, C &Cmp) const {
-    // TODO -- implement CFG comparisons
+    // TODO: implement CFG comparisons
     return Cmp.comparePointers(this, E);
   }
 
 private:
+  void renumberInstrs();       // assign unique ids to all instructions
+
+private:
   MemRegionRef Arena;
   BlockArray   Blocks;
   BasicBlock   *Entry;
   BasicBlock   *Exit;
+  unsigned     NumInstructions;
+  bool         Normal;
 };
 
 
-class Goto : public SExpr {
-public:
-  static bool classof(const SExpr *E) { return E->opcode() == COP_Goto; }
-
-  Goto(BasicBlock *B, unsigned I)
-      : SExpr(COP_Goto), TargetBlock(B), Index(I) {}
-  Goto(const Goto &G, BasicBlock *B, unsigned I)
-      : SExpr(COP_Goto), TargetBlock(B), Index(I) {}
-
-  const BasicBlock *targetBlock() const { return TargetBlock; }
-  BasicBlock *targetBlock() { return TargetBlock; }
-
-  unsigned index() const { return Index; }
-
-  template <class V>
-  typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
-    BasicBlock *Ntb = Vs.reduceBasicBlockRef(TargetBlock);
-    return Vs.reduceGoto(*this, Ntb);
-  }
-
-  template <class C>
-  typename C::CType compare(const Goto *E, C &Cmp) const {
-    // TODO -- implement CFG comparisons
-    return Cmp.comparePointers(this, E);
-  }
-
-private:
-  BasicBlock *TargetBlock;
-  unsigned Index;   // Index into Phi nodes of target block.
-};
-
-
-class Branch : public SExpr {
-public:
-  static bool classof(const SExpr *E) { return E->opcode() == COP_Branch; }
-
-  Branch(SExpr *C, BasicBlock *T, BasicBlock *E, unsigned TI, unsigned EI)
-      : SExpr(COP_Branch), Condition(C), ThenBlock(T), ElseBlock(E),
-        ThenIndex(TI), ElseIndex(EI)
-  {}
-  Branch(const Branch &Br, SExpr *C, BasicBlock *T, BasicBlock *E,
-         unsigned TI, unsigned EI)
-      : SExpr(COP_Branch), Condition(C), ThenBlock(T), ElseBlock(E),
-        ThenIndex(TI), ElseIndex(EI)
-  {}
-
-  const SExpr *condition() const { return Condition; }
-  SExpr *condition() { return Condition; }
-
-  const BasicBlock *thenBlock() const { return ThenBlock; }
-  BasicBlock *thenBlock() { return ThenBlock; }
-
-  const BasicBlock *elseBlock() const { return ElseBlock; }
-  BasicBlock *elseBlock() { return ElseBlock; }
-
-  unsigned thenIndex() const { return ThenIndex; }
-  unsigned elseIndex() const { return ElseIndex; }
-
-  template <class V>
-  typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
-    auto Nc = Vs.traverse(Condition, Vs.subExprCtx(Ctx));
-    BasicBlock *Ntb = Vs.reduceBasicBlockRef(ThenBlock);
-    BasicBlock *Nte = Vs.reduceBasicBlockRef(ElseBlock);
-    return Vs.reduceBranch(*this, Nc, Ntb, Nte);
-  }
 
-  template <class C>
-  typename C::CType compare(const Branch *E, C &Cmp) const {
-    // TODO -- implement CFG comparisons
-    return Cmp.comparePointers(this, E);
-  }
-
-private:
-  SExpr *Condition;
-  BasicBlock *ThenBlock;
-  BasicBlock *ElseBlock;
-  unsigned ThenIndex;
-  unsigned ElseIndex;
-};
-
-
-// An identifier, e.g. 'foo' or 'x'.
-// This is a pseduo-term; it will be lowered to a variable or projection.
+/// An identifier, e.g. 'foo' or 'x'.
+/// This is a pseduo-term; it will be lowered to a variable or projection.
 class Identifier : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Identifier; }
@@ -1742,8 +1810,8 @@ private:
 };
 
 
-// An if-then-else expression.
-// This is a pseduo-term; it will be lowered to a branch in a CFG.
+/// An if-then-else expression.
+/// This is a pseduo-term; it will be lowered to a branch in a CFG.
 class IfThenElse : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_IfThenElse; }
@@ -1755,14 +1823,14 @@ public:
     : SExpr(I), Condition(C), ThenExpr(T), ElseExpr(E)
   { }
 
-  SExpr *condition() { return Condition.get(); }   // Address to store to
-  const SExpr *condition() const { return Condition.get(); }
+  SExpr *condition() { return Condition; }   // Address to store to
+  const SExpr *condition() const { return Condition; }
 
-  SExpr *thenExpr() { return ThenExpr.get(); }     // Value to store
-  const SExpr *thenExpr() const { return ThenExpr.get(); }
+  SExpr *thenExpr() { return ThenExpr; }     // Value to store
+  const SExpr *thenExpr() const { return ThenExpr; }
 
-  SExpr *elseExpr() { return ElseExpr.get(); }     // Value to store
-  const SExpr *elseExpr() const { return ElseExpr.get(); }
+  SExpr *elseExpr() { return ElseExpr; }     // Value to store
+  const SExpr *elseExpr() const { return ElseExpr; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1784,14 +1852,14 @@ public:
   }
 
 private:
-  SExprRef Condition;
-  SExprRef ThenExpr;
-  SExprRef ElseExpr;
+  SExpr* Condition;
+  SExpr* ThenExpr;
+  SExpr* ElseExpr;
 };
 
 
-// A let-expression,  e.g.  let x=t; u.
-// This is a pseduo-term; it will be lowered to instructions in a CFG.
+/// A let-expression,  e.g.  let x=t; u.
+/// This is a pseduo-term; it will be lowered to instructions in a CFG.
 class Let : public SExpr {
 public:
   static bool classof(const SExpr *E) { return E->opcode() == COP_Let; }
@@ -1806,8 +1874,8 @@ public:
   Variable *variableDecl()  { return VarDecl; }
   const Variable *variableDecl() const { return VarDecl; }
 
-  SExpr *body() { return Body.get(); }
-  const SExpr *body() const { return Body.get(); }
+  SExpr *body() { return Body; }
+  const SExpr *body() const { return Body; }
 
   template <class V>
   typename V::R_SExpr traverse(V &Vs, typename V::R_Ctx Ctx) {
@@ -1834,14 +1902,14 @@ public:
 
 private:
   Variable *VarDecl;
-  SExprRef Body;
+  SExpr* Body;
 };
 
 
 
 const SExpr *getCanonicalVal(const SExpr *E);
 SExpr* simplifyToCanonicalVal(SExpr *E);
-void simplifyIncompleteArg(Variable *V, til::Phi *Ph);
+void simplifyIncompleteArg(til::Phi *Ph);
 
 
 } // end namespace til

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h Wed Sep 10 17:12:52 2014
@@ -58,11 +58,16 @@ public:
   // Traverse an expression -- returning a result of type R_SExpr.
   // Override this method to do something for every expression, regardless
   // of which kind it is.
-  typename R::R_SExpr traverse(SExprRef &E, typename R::R_Ctx Ctx) {
-    return traverse(E.get(), Ctx);
+  // E is a reference, so this can be use for in-place updates.
+  // The type T must be a subclass of SExpr.
+  template <class T>
+  typename R::R_SExpr traverse(T* &E, typename R::R_Ctx Ctx) {
+    return traverseSExpr(E, Ctx);
   }
 
-  typename R::R_SExpr traverse(SExpr *E, typename R::R_Ctx Ctx) {
+  // Override this method to do something for every expression.
+  // Does not allow in-place updates.
+  typename R::R_SExpr traverseSExpr(SExpr *E, typename R::R_Ctx Ctx) {
     return traverseByCase(E, Ctx);
   }
 
@@ -75,6 +80,7 @@ public:
 #include "ThreadSafetyOps.def"
 #undef TIL_OPCODE_DEF
     }
+    return self()->reduceNull();
   }
 
 // Traverse e, by static dispatch on the type "X" of e.
@@ -92,10 +98,10 @@ public:
 class SimpleReducerBase {
 public:
   enum TraversalKind {
-    TRV_Normal,
-    TRV_Decl,
-    TRV_Lazy,
-    TRV_Type
+    TRV_Normal,   // ordinary subexpressions
+    TRV_Decl,     // declarations (e.g. function bodies)
+    TRV_Lazy,     // expressions that require lazy evaluation
+    TRV_Type      // type expressions
   };
 
   // R_Ctx defines a "context" for the traversal, which encodes information
@@ -147,153 +153,6 @@ protected:
 };
 
 
-// Implements a traversal that makes a deep copy of an SExpr.
-// The default behavior of reduce##X(...) is to create a copy of the original.
-// Subclasses can override reduce##X to implement non-destructive rewriting
-// passes.
-template<class Self>
-class CopyReducer : public Traversal<Self, CopyReducerBase>,
-                    public CopyReducerBase {
-public:
-  CopyReducer(MemRegionRef A) : CopyReducerBase(A) {}
-
-public:
-  R_SExpr reduceNull() {
-    return nullptr;
-  }
-  // R_SExpr reduceFuture(...)  is never used.
-
-  R_SExpr reduceUndefined(Undefined &Orig) {
-    return new (Arena) Undefined(Orig);
-  }
-  R_SExpr reduceWildcard(Wildcard &Orig) {
-    return new (Arena) Wildcard(Orig);
-  }
-
-  R_SExpr reduceLiteral(Literal &Orig) {
-    return new (Arena) Literal(Orig);
-  }
-  template<class T>
-  R_SExpr reduceLiteralT(LiteralT<T> &Orig) {
-    return new (Arena) LiteralT<T>(Orig);
-  }
-  R_SExpr reduceLiteralPtr(LiteralPtr &Orig) {
-    return new (Arena) LiteralPtr(Orig);
-  }
-
-  R_SExpr reduceFunction(Function &Orig, Variable *Nvd, R_SExpr E0) {
-    return new (Arena) Function(Orig, Nvd, E0);
-  }
-  R_SExpr reduceSFunction(SFunction &Orig, Variable *Nvd, R_SExpr E0) {
-    return new (Arena) SFunction(Orig, Nvd, E0);
-  }
-  R_SExpr reduceCode(Code &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) Code(Orig, E0, E1);
-  }
-  R_SExpr reduceField(Field &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) Field(Orig, E0, E1);
-  }
-
-  R_SExpr reduceApply(Apply &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) Apply(Orig, E0, E1);
-  }
-  R_SExpr reduceSApply(SApply &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) SApply(Orig, E0, E1);
-  }
-  R_SExpr reduceProject(Project &Orig, R_SExpr E0) {
-    return new (Arena) Project(Orig, E0);
-  }
-  R_SExpr reduceCall(Call &Orig, R_SExpr E0) {
-    return new (Arena) Call(Orig, E0);
-  }
-
-  R_SExpr reduceAlloc(Alloc &Orig, R_SExpr E0) {
-    return new (Arena) Alloc(Orig, E0);
-  }
-  R_SExpr reduceLoad(Load &Orig, R_SExpr E0) {
-    return new (Arena) Load(Orig, E0);
-  }
-  R_SExpr reduceStore(Store &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) Store(Orig, E0, E1);
-  }
-  R_SExpr reduceArrayIndex(ArrayIndex &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) ArrayIndex(Orig, E0, E1);
-  }
-  R_SExpr reduceArrayAdd(ArrayAdd &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) ArrayAdd(Orig, E0, E1);
-  }
-  R_SExpr reduceUnaryOp(UnaryOp &Orig, R_SExpr E0) {
-    return new (Arena) UnaryOp(Orig, E0);
-  }
-  R_SExpr reduceBinaryOp(BinaryOp &Orig, R_SExpr E0, R_SExpr E1) {
-    return new (Arena) BinaryOp(Orig, E0, E1);
-  }
-  R_SExpr reduceCast(Cast &Orig, R_SExpr E0) {
-    return new (Arena) Cast(Orig, E0);
-  }
-
-  R_SExpr reduceSCFG(SCFG &Orig, Container<BasicBlock *> &Bbs) {
-    return nullptr;  // FIXME: implement CFG rewriting
-  }
-  R_BasicBlock reduceBasicBlock(BasicBlock &Orig, Container<Variable *> &As,
-                                Container<Variable *> &Is, R_SExpr T) {
-    return nullptr;  // FIXME: implement CFG rewriting
-  }
-  R_SExpr reducePhi(Phi &Orig, Container<R_SExpr> &As) {
-    return new (Arena) Phi(Orig, std::move(As.Elems));
-  }
-  R_SExpr reduceGoto(Goto &Orig, BasicBlock *B) {
-    return new (Arena) Goto(Orig, B, 0);  // FIXME: set index
-  }
-  R_SExpr reduceBranch(Branch &O, R_SExpr C, BasicBlock *B0, BasicBlock *B1) {
-    return new (Arena) Branch(O, C, B0, B1, 0, 0);  // FIXME: set indices
-  }
-
-  R_SExpr reduceIdentifier(Identifier &Orig) {
-    return new (Arena) Identifier(Orig);
-  }
-  R_SExpr reduceIfThenElse(IfThenElse &Orig, R_SExpr C, R_SExpr T, R_SExpr E) {
-    return new (Arena) IfThenElse(Orig, C, T, E);
-  }
-  R_SExpr reduceLet(Let &Orig, Variable *Nvd, R_SExpr B) {
-    return new (Arena) Let(Orig, Nvd, B);
-  }
-
-  // Create a new variable from orig, and push it onto the lexical scope.
-  Variable *enterScope(Variable &Orig, R_SExpr E0) {
-    return new (Arena) Variable(Orig, E0);
-  }
-  // Exit the lexical scope of orig.
-  void exitScope(const Variable &Orig) {}
-
-  void enterCFG(SCFG &Cfg) {}
-  void exitCFG(SCFG &Cfg) {}
-  void enterBasicBlock(BasicBlock &BB) {}
-  void exitBasicBlock(BasicBlock &BB) {}
-
-  // Map Variable references to their rewritten definitions.
-  Variable *reduceVariableRef(Variable *Ovd) { return Ovd; }
-
-  // Map BasicBlock references to their rewritten definitions.
-  BasicBlock *reduceBasicBlockRef(BasicBlock *Obb) { return Obb; }
-};
-
-
-class SExprCopier : public CopyReducer<SExprCopier> {
-public:
-  typedef SExpr *R_SExpr;
-
-  SExprCopier(MemRegionRef A) : CopyReducer(A) { }
-
-  // Create a copy of e in region a.
-  static SExpr *copy(SExpr *E, MemRegionRef A) {
-    SExprCopier Copier(A);
-    return Copier.traverse(E, TRV_Normal);
-  }
-};
-
-
-
 // Base class for visit traversals.
 class VisitReducerBase : public SimpleReducerBase {
 public:
@@ -368,8 +227,8 @@ public:
   R_SExpr reduceSCFG(SCFG &Orig, Container<BasicBlock *> Bbs) {
     return Bbs.Success;
   }
-  R_BasicBlock reduceBasicBlock(BasicBlock &Orig, Container<Variable *> &As,
-                                Container<Variable *> &Is, R_SExpr T) {
+  R_BasicBlock reduceBasicBlock(BasicBlock &Orig, Container<R_SExpr> &As,
+                                Container<R_SExpr> &Is, R_SExpr T) {
     return (As.Success && Is.Success && T);
   }
   R_SExpr reducePhi(Phi &Orig, Container<R_SExpr> &As) {
@@ -381,6 +240,9 @@ public:
   R_SExpr reduceBranch(Branch &O, R_SExpr C, BasicBlock *B0, BasicBlock *B1) {
     return C;
   }
+  R_SExpr reduceReturn(Return &O, R_SExpr E) {
+    return E;
+  }
 
   R_SExpr reduceIdentifier(Identifier &Orig) {
     return true;
@@ -433,7 +295,7 @@ public:
 #include "ThreadSafetyOps.def"
 #undef TIL_OPCODE_DEF
     }
-    llvm_unreachable("invalid enum");
+    return false;
   }
 };
 
@@ -514,9 +376,9 @@ public:
 
 
 
-inline std::ostream& operator<<(std::ostream& SS, llvm::StringRef R) {
-  return SS.write(R.data(), R.size());
-}
+// inline std::ostream& operator<<(std::ostream& SS, StringRef R) {
+//   return SS.write(R.data(), R.size());
+// }
 
 // Pretty printer for TIL expressions
 template <typename Self, typename StreamType>
@@ -587,6 +449,7 @@ protected:
       case COP_Phi:        return Prec_Atom;
       case COP_Goto:       return Prec_Atom;
       case COP_Branch:     return Prec_Atom;
+      case COP_Return:     return Prec_Other;
 
       case COP_Identifier: return Prec_Atom;
       case COP_IfThenElse: return Prec_Other;
@@ -595,22 +458,29 @@ protected:
     return Prec_MAX;
   }
 
-  void printBlockLabel(StreamType & SS, const BasicBlock *BB, unsigned index) {
+  void printBlockLabel(StreamType & SS, const BasicBlock *BB, int index) {
     if (!BB) {
       SS << "BB_null";
       return;
     }
     SS << "BB_";
     SS << BB->blockID();
-    SS << ":";
-    SS << index;
+    if (index >= 0) {
+      SS << ":";
+      SS << index;
+    }
   }
 
-  void printSExpr(const SExpr *E, StreamType &SS, unsigned P) {
+
+  void printSExpr(const SExpr *E, StreamType &SS, unsigned P, bool Sub=true) {
     if (!E) {
       self()->printNull(SS);
       return;
     }
+    if (Sub && E->block() && E->opcode() != COP_Variable) {
+      SS << "_x" << E->id();
+      return;
+    }
     if (self()->precedence(E) > P) {
       // Wrap expr in () if necessary.
       SS << "(";
@@ -740,20 +610,11 @@ protected:
     SS << E->clangDecl()->getNameAsString();
   }
 
-  void printVariable(const Variable *V, StreamType &SS, bool IsVarDecl = false) {
-    if (!IsVarDecl && Cleanup) {
-      const SExpr* E = getCanonicalVal(V);
-      if (E != V) {
-        printSExpr(E, SS, Prec_Atom);
-        return;
-      }
-    }
-    if (V->kind() == Variable::VK_LetBB)
-      SS << V->name() << V->getBlockID() << "_" << V->getID();
-    else if (CStyle && V->kind() == Variable::VK_SFun)
+  void printVariable(const Variable *V, StreamType &SS, bool IsVarDecl=false) {
+    if (CStyle && V->kind() == Variable::VK_SFun)
       SS << "this";
     else
-      SS << V->name() << V->getID();
+      SS << V->name() << V->id();
   }
 
   void printFunction(const Function *E, StreamType &SS, unsigned sugared = 0) {
@@ -927,32 +788,38 @@ protected:
     newline(SS);
   }
 
+
+  void printBBInstr(const SExpr *E, StreamType &SS) {
+    bool Sub = false;
+    if (E->opcode() == COP_Variable) {
+      auto *V = cast<Variable>(E);
+      SS << "let " << V->name() << V->id() << " = ";
+      E = V->definition();
+      Sub = true;
+    }
+    else if (E->opcode() != COP_Store) {
+      SS << "let _x" << E->id() << " = ";
+    }
+    self()->printSExpr(E, SS, Prec_MAX, Sub);
+    SS << ";";
+    newline(SS);
+  }
+
   void printBasicBlock(const BasicBlock *E, StreamType &SS) {
     SS << "BB_" << E->blockID() << ":";
     if (E->parent())
       SS << " BB_" << E->parent()->blockID();
     newline(SS);
-    for (auto *A : E->arguments()) {
-      SS << "let ";
-      self()->printVariable(A, SS, true);
-      SS << " = ";
-      self()->printSExpr(A->definition(), SS, Prec_MAX);
-      SS << ";";
-      newline(SS);
-    }
-    for (auto *I : E->instructions()) {
-      if (I->definition()->opcode() != COP_Store) {
-        SS << "let ";
-        self()->printVariable(I, SS, true);
-        SS << " = ";
-      }
-      self()->printSExpr(I->definition(), SS, Prec_MAX);
-      SS << ";";
-      newline(SS);
-    }
+
+    for (auto *A : E->arguments())
+      printBBInstr(A, SS);
+
+    for (auto *I : E->instructions())
+      printBBInstr(I, SS);
+
     const SExpr *T = E->terminator();
     if (T) {
-      self()->printSExpr(T, SS, Prec_MAX);
+      self()->printSExpr(T, SS, Prec_MAX, false);
       SS << ";";
       newline(SS);
     }
@@ -983,9 +850,14 @@ protected:
     SS << "branch (";
     self()->printSExpr(E->condition(), SS, Prec_MAX);
     SS << ") ";
-    printBlockLabel(SS, E->thenBlock(), E->thenIndex());
+    printBlockLabel(SS, E->thenBlock(), -1);
     SS << " ";
-    printBlockLabel(SS, E->elseBlock(), E->elseIndex());
+    printBlockLabel(SS, E->elseBlock(), -1);
+  }
+
+  void printReturn(const Return *E, StreamType &SS) {
+    SS << "return ";
+    self()->printSExpr(E->returnValue(), SS, Prec_Other);
   }
 
   void printIdentifier(const Identifier *E, StreamType &SS) {

Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyUtil.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyUtil.h?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyUtil.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyUtil.h Wed Sep 10 17:12:52 2014
@@ -142,20 +142,35 @@ public:
     assert(i < Size && "Array index out of bounds.");
     return Data[i];
   }
+  T &back() {
+    assert(Size && "No elements in the array.");
+    return Data[Size - 1];
+  }
+  const T &back() const {
+    assert(Size && "No elements in the array.");
+    return Data[Size - 1];
+  }
 
   iterator begin() { return Data; }
+  iterator end()   { return Data + Size; }
+
   const_iterator begin() const { return Data; }
-  iterator end() { return Data + Size; }
-  const_iterator end() const { return Data + Size; }
+  const_iterator end()   const { return Data + Size; }
 
   const_iterator cbegin() const { return Data; }
-  const_iterator cend() const { return Data + Size; }
+  const_iterator cend()   const { return Data + Size; }
 
   void push_back(const T &Elem) {
     assert(Size < Capacity);
     Data[Size++] = Elem;
   }
 
+  // drop last n elements from array
+  void drop(unsigned n = 0) {
+    assert(Size > n);
+    Size -= n;
+  }
+
   void setValues(unsigned Sz, const T& C) {
     assert(Sz <= Capacity);
     Size = Sz;
@@ -173,6 +188,37 @@ public:
     return J - Osz;
   }
 
+  // An adaptor to reverse a simple array
+  class ReverseAdaptor {
+   public:
+    ReverseAdaptor(SimpleArray &Array) : Array(Array) {}
+    // A reverse iterator used by the reverse adaptor
+    class Iterator {
+     public:
+      Iterator(T *Data) : Data(Data) {}
+      T &operator*() { return *Data; }
+      const T &operator*() const { return *Data; }
+      Iterator &operator++() {
+        --Data;
+        return *this;
+      }
+      bool operator!=(Iterator Other) { return Data != Other.Data; }
+
+     private:
+      T *Data;
+    };
+    Iterator begin() { return Array.end() - 1; }
+    Iterator end() { return Array.begin() - 1; }
+    const Iterator begin() const { return Array.end() - 1; }
+    const Iterator end() const { return Array.begin() - 1; }
+
+   private:
+    SimpleArray &Array;
+  };
+
+  const ReverseAdaptor reverse() const { return ReverseAdaptor(*this); }
+  ReverseAdaptor reverse() { return ReverseAdaptor(*this); }
+
 private:
   // std::max is annoying here, because it requires a reference,
   // thus forcing InitialCapacity to be initialized outside the .h file.
@@ -187,6 +233,7 @@ private:
   size_t Capacity;
 };
 
+
 }  // end namespace til
 
 
@@ -312,6 +359,12 @@ private:
 };
 
 
+inline std::ostream& operator<<(std::ostream& ss, const StringRef str) {
+  ss << str.data();
+  return ss;
+}
+
+
 } // end namespace threadSafety
 } // end namespace clang
 

Modified: cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp (original)
+++ cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp Wed Sep 10 17:12:52 2014
@@ -63,11 +63,9 @@ std::string getSourceLiteralString(const
 namespace til {
 
 // Return true if E is a variable that points to an incomplete Phi node.
-static bool isIncompleteVar(const SExpr *E) {
-  if (const auto *V = dyn_cast<Variable>(E)) {
-    if (const auto *Ph = dyn_cast<Phi>(V->definition()))
-      return Ph->status() == Phi::PH_Incomplete;
-  }
+static bool isIncompletePhi(const SExpr *E) {
+  if (const auto *Ph = dyn_cast<Phi>(E))
+    return Ph->status() == Phi::PH_Incomplete;
   return false;
 }
 
@@ -320,6 +318,8 @@ til::SExpr *SExprBuilder::translateCXXTh
 const ValueDecl *getValueDeclFromSExpr(const til::SExpr *E) {
   if (auto *V = dyn_cast<til::Variable>(E))
     return V->clangDecl();
+  if (auto *Ph = dyn_cast<til::Phi>(E))
+    return Ph->clangDecl();
   if (auto *P = dyn_cast<til::Project>(E))
     return P->clangDecl();
   if (auto *L = dyn_cast<til::LiteralPtr>(E))
@@ -641,14 +641,14 @@ SExprBuilder::translateDeclStmt(const De
 // If E is trivial returns E.
 til::SExpr *SExprBuilder::addStatement(til::SExpr* E, const Stmt *S,
                                        const ValueDecl *VD) {
-  if (!E || !CurrentBB || til::ThreadSafetyTIL::isTrivial(E))
+  if (!E || !CurrentBB || E->block() || til::ThreadSafetyTIL::isTrivial(E))
     return E;
-
-  til::Variable *V = new (Arena) til::Variable(E, VD);
-  CurrentInstructions.push_back(V);
+  if (VD)
+    E = new (Arena) til::Variable(E, VD);
+  CurrentInstructions.push_back(E);
   if (S)
-    insertStmt(S, V);
-  return V;
+    insertStmt(S, E);
+  return E;
 }
 
 
@@ -705,11 +705,11 @@ void SExprBuilder::makePhiNodeVar(unsign
   unsigned ArgIndex = CurrentBlockInfo->ProcessedPredecessors;
   assert(ArgIndex > 0 && ArgIndex < NPreds);
 
-  til::Variable *V = dyn_cast<til::Variable>(CurrentLVarMap[i].second);
-  if (V && V->getBlockID() == CurrentBB->blockID()) {
+  til::SExpr *CurrE = CurrentLVarMap[i].second;
+  if (CurrE->block() == CurrentBB) {
     // We already have a Phi node in the current block,
     // so just add the new variable to the Phi node.
-    til::Phi *Ph = dyn_cast<til::Phi>(V->definition());
+    til::Phi *Ph = dyn_cast<til::Phi>(CurrE);
     assert(Ph && "Expecting Phi node.");
     if (E)
       Ph->values()[ArgIndex] = E;
@@ -718,27 +718,26 @@ void SExprBuilder::makePhiNodeVar(unsign
 
   // Make a new phi node: phi(..., E)
   // All phi args up to the current index are set to the current value.
-  til::SExpr *CurrE = CurrentLVarMap[i].second;
   til::Phi *Ph = new (Arena) til::Phi(Arena, NPreds);
   Ph->values().setValues(NPreds, nullptr);
   for (unsigned PIdx = 0; PIdx < ArgIndex; ++PIdx)
     Ph->values()[PIdx] = CurrE;
   if (E)
     Ph->values()[ArgIndex] = E;
+  Ph->setClangDecl(CurrentLVarMap[i].first);
   // If E is from a back-edge, or either E or CurrE are incomplete, then
   // mark this node as incomplete; we may need to remove it later.
-  if (!E || isIncompleteVar(E) || isIncompleteVar(CurrE)) {
+  if (!E || isIncompletePhi(E) || isIncompletePhi(CurrE)) {
     Ph->setStatus(til::Phi::PH_Incomplete);
   }
 
   // Add Phi node to current block, and update CurrentLVarMap[i]
-  auto *Var = new (Arena) til::Variable(Ph, CurrentLVarMap[i].first);
-  CurrentArguments.push_back(Var);
+  CurrentArguments.push_back(Ph);
   if (Ph->status() == til::Phi::PH_Incomplete)
-    IncompleteArgs.push_back(Var);
+    IncompleteArgs.push_back(Ph);
 
   CurrentLVarMap.makeWritable();
-  CurrentLVarMap.elem(i).second = Var;
+  CurrentLVarMap.elem(i).second = Ph;
 }
 
 
@@ -812,15 +811,13 @@ void SExprBuilder::mergePhiNodesBackEdge
   unsigned ArgIndex = BBInfo[Blk->getBlockID()].ProcessedPredecessors;
   assert(ArgIndex > 0 && ArgIndex < BB->numPredecessors());
 
-  for (til::Variable *V : BB->arguments()) {
-    til::Phi *Ph = dyn_cast_or_null<til::Phi>(V->definition());
+  for (til::SExpr *PE : BB->arguments()) {
+    til::Phi *Ph = dyn_cast_or_null<til::Phi>(PE);
     assert(Ph && "Expecting Phi Node.");
     assert(Ph->values()[ArgIndex] == nullptr && "Wrong index for back edge.");
-    assert(V->clangDecl() && "No local variable for Phi node.");
 
-    til::SExpr *E = lookupVarDecl(V->clangDecl());
+    til::SExpr *E = lookupVarDecl(Ph->clangDecl());
     assert(E && "Couldn't find local variable for Phi node.");
-
     Ph->values()[ArgIndex] = E;
   }
 }
@@ -899,8 +896,8 @@ void SExprBuilder::enterCFGBlockBody(con
   // Push those arguments onto the basic block.
   CurrentBB->arguments().reserve(
     static_cast<unsigned>(CurrentArguments.size()), Arena);
-  for (auto *V : CurrentArguments)
-    CurrentBB->addArgument(V);
+  for (auto *A : CurrentArguments)
+    CurrentBB->addArgument(A);
 }
 
 
@@ -934,7 +931,7 @@ void SExprBuilder::exitCFGBlockBody(cons
     til::BasicBlock *BB = *It ? lookupBlock(*It) : nullptr;
     // TODO: set index
     unsigned Idx = BB ? BB->findPredecessorIndex(CurrentBB) : 0;
-    til::SExpr *Tm = new (Arena) til::Goto(BB, Idx);
+    auto *Tm = new (Arena) til::Goto(BB, Idx);
     CurrentBB->setTerminator(Tm);
   }
   else if (N == 2) {
@@ -942,9 +939,8 @@ void SExprBuilder::exitCFGBlockBody(cons
     til::BasicBlock *BB1 = *It ? lookupBlock(*It) : nullptr;
     ++It;
     til::BasicBlock *BB2 = *It ? lookupBlock(*It) : nullptr;
-    unsigned Idx1 = BB1 ? BB1->findPredecessorIndex(CurrentBB) : 0;
-    unsigned Idx2 = BB2 ? BB2->findPredecessorIndex(CurrentBB) : 0;
-    til::SExpr *Tm = new (Arena) til::Branch(C, BB1, BB2, Idx1, Idx2);
+    // FIXME: make sure these arent' critical edges.
+    auto *Tm = new (Arena) til::Branch(C, BB1, BB2);
     CurrentBB->setTerminator(Tm);
   }
 }
@@ -971,10 +967,9 @@ void SExprBuilder::exitCFGBlock(const CF
 
 
 void SExprBuilder::exitCFG(const CFGBlock *Last) {
-  for (auto *V : IncompleteArgs) {
-    til::Phi *Ph = dyn_cast<til::Phi>(V->definition());
-    if (Ph && Ph->status() == til::Phi::PH_Incomplete)
-      simplifyIncompleteArg(V, Ph);
+  for (auto *Ph : IncompleteArgs) {
+    if (Ph->status() == til::Phi::PH_Incomplete)
+      simplifyIncompleteArg(Ph);
   }
 
   CurrentArguments.clear();

Modified: cfe/trunk/lib/Analysis/ThreadSafetyTIL.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/ThreadSafetyTIL.cpp?rev=217556&r1=217555&r2=217556&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/ThreadSafetyTIL.cpp (original)
+++ cfe/trunk/lib/Analysis/ThreadSafetyTIL.cpp Wed Sep 10 17:12:52 2014
@@ -48,12 +48,20 @@ StringRef getBinaryOpcodeString(TIL_Bina
 }
 
 
+SExpr* Future::force() {
+  Status = FS_evaluating;
+  Result = compute();
+  Status = FS_done;
+  return Result;
+}
+
+
 unsigned BasicBlock::addPredecessor(BasicBlock *Pred) {
   unsigned Idx = Predecessors.size();
   Predecessors.reserveCheck(1, Arena);
   Predecessors.push_back(Pred);
-  for (Variable *V : Args) {
-    if (Phi* Ph = dyn_cast<Phi>(V->definition())) {
+  for (SExpr *E : Args) {
+    if (Phi* Ph = dyn_cast<Phi>(E)) {
       Ph->values().reserveCheck(1, Arena);
       Ph->values().push_back(nullptr);
     }
@@ -61,105 +69,73 @@ unsigned BasicBlock::addPredecessor(Basi
   return Idx;
 }
 
+
 void BasicBlock::reservePredecessors(unsigned NumPreds) {
   Predecessors.reserve(NumPreds, Arena);
-  for (Variable *V : Args) {
-    if (Phi* Ph = dyn_cast<Phi>(V->definition())) {
+  for (SExpr *E : Args) {
+    if (Phi* Ph = dyn_cast<Phi>(E)) {
       Ph->values().reserve(NumPreds, Arena);
     }
   }
 }
 
-void BasicBlock::renumberVars() {
-  unsigned VID = 0;
-  for (Variable *V : Args) {
-    V->setID(BlockID, VID++);
-  }
-  for (Variable *V : Instrs) {
-    V->setID(BlockID, VID++);
-  }
-}
-
-void SCFG::renumberVars() {
-  for (BasicBlock *B : Blocks) {
-    B->renumberVars();
-  }
-}
-
-
 
 // If E is a variable, then trace back through any aliases or redundant
 // Phi nodes to find the canonical definition.
 const SExpr *getCanonicalVal(const SExpr *E) {
-  while (auto *V = dyn_cast<Variable>(E)) {
-    const SExpr *D;
-    do {
-      if (V->kind() != Variable::VK_Let)
-        return V;
-      D = V->definition();
-      auto *V2 = dyn_cast<Variable>(D);
-      if (V2)
-        V = V2;
-      else
-        break;
-    } while (true);
-
-    if (ThreadSafetyTIL::isTrivial(D))
-      return D;
-
-    if (const Phi *Ph = dyn_cast<Phi>(D)) {
+  while (true) {
+    if (auto *V = dyn_cast<Variable>(E)) {
+      if (V->kind() == Variable::VK_Let) {
+        E = V->definition();
+        continue;
+      }
+    }
+    if (const Phi *Ph = dyn_cast<Phi>(E)) {
       if (Ph->status() == Phi::PH_SingleVal) {
         E = Ph->values()[0];
         continue;
       }
     }
-    return V;
+    break;
   }
   return E;
 }
 
 
-
 // If E is a variable, then trace back through any aliases or redundant
 // Phi nodes to find the canonical definition.
 // The non-const version will simplify incomplete Phi nodes.
 SExpr *simplifyToCanonicalVal(SExpr *E) {
-  while (auto *V = dyn_cast<Variable>(E)) {
-    SExpr *D;
-    do {
+  while (true) {
+    if (auto *V = dyn_cast<Variable>(E)) {
       if (V->kind() != Variable::VK_Let)
         return V;
-      D = V->definition();
-      auto *V2 = dyn_cast<Variable>(D);
-      if (V2)
-        V = V2;
-      else
-        break;
-    } while (true);
-
-    if (ThreadSafetyTIL::isTrivial(D))
-      return D;
-
-    if (Phi *Ph = dyn_cast<Phi>(D)) {
+      // Eliminate redundant variables, e.g. x = y, or x = 5,
+      // but keep anything more complicated.
+      if (til::ThreadSafetyTIL::isTrivial(V->definition())) {
+        E = V->definition();
+        continue;
+      }
+      return V;
+    }
+    if (auto *Ph = dyn_cast<Phi>(E)) {
       if (Ph->status() == Phi::PH_Incomplete)
-        simplifyIncompleteArg(V, Ph);
-
+        simplifyIncompleteArg(Ph);
+      // Eliminate redundant Phi nodes.
       if (Ph->status() == Phi::PH_SingleVal) {
         E = Ph->values()[0];
         continue;
       }
     }
-    return V;
+    return E;
   }
-  return E;
 }
 
 
-
 // Trace the arguments of an incomplete Phi node to see if they have the same
 // canonical definition.  If so, mark the Phi node as redundant.
 // getCanonicalVal() will recursively call simplifyIncompletePhi().
-void simplifyIncompleteArg(Variable *V, til::Phi *Ph) {
+void simplifyIncompleteArg(til::Phi *Ph) {
   assert(Ph && Ph->status() == Phi::PH_Incomplete);
 
   // eliminate infinite recursion -- assume that this node is not redundant.
@@ -168,18 +144,200 @@ void simplifyIncompleteArg(Variable *V,
   SExpr *E0 = simplifyToCanonicalVal(Ph->values()[0]);
   for (unsigned i=1, n=Ph->values().size(); i<n; ++i) {
     SExpr *Ei = simplifyToCanonicalVal(Ph->values()[i]);
-    if (Ei == V)
+    if (Ei == Ph)
       continue;  // Recursive reference to itself.  Don't count.
     if (Ei != E0) {
       return;    // Status is already set to MultiVal.
     }
   }
   Ph->setStatus(Phi::PH_SingleVal);
-  // Eliminate Redundant Phi node.
-  V->setDefinition(Ph->values()[0]);
 }
 
 
+// Renumbers the arguments and instructions to have unique, sequential IDs.
+int BasicBlock::renumberInstrs(int ID) {
+  for (auto *Arg : Args)
+    Arg->setID(this, ID++);
+  for (auto *Instr : Instrs)
+    Instr->setID(this, ID++);
+  TermInstr->setID(this, ID++);
+  return ID;
+}
+
+// Sorts the CFGs blocks using a reverse post-order depth-first traversal.
+// Each block will be written into the Blocks array in order, and its BlockID
+// will be set to the index in the array.  Sorting should start from the entry
+// block, and ID should be the total number of blocks.
+int BasicBlock::topologicalSort(SimpleArray<BasicBlock*>& Blocks, int ID) {
+  if (Visited) return ID;
+  Visited = 1;
+  for (auto *Block : successors())
+    ID = Block->topologicalSort(Blocks, ID);
+  // set ID and update block array in place.
+  // We may lose pointers to unreachable blocks.
+  assert(ID > 0);
+  BlockID = --ID;
+  Blocks[BlockID] = this;
+  return ID;
+}
+
+// Performs a reverse topological traversal, starting from the exit block and
+// following back-edges.  The dominator is serialized before any predecessors,
+// which guarantees that all blocks are serialized after their dominator and
+// before their post-dominator (because it's a reverse topological traversal).
+// ID should be initially set to 0.
+//
+// This sort assumes that (1) dominators have been computed, (2) there are no
+// critical edges, and (3) the entry block is reachable from the exit block
+// and no blocks are accessable via traversal of back-edges from the exit that
+// weren't accessable via forward edges from the entry.
+int BasicBlock::topologicalFinalSort(SimpleArray<BasicBlock*>& Blocks, int ID) {
+  // Visited is assumed to have been set by the topologicalSort.  This pass
+  // assumes !Visited means that we've visited this node before.
+  if (!Visited) return ID;
+  Visited = 0;
+  if (DominatorNode.Parent)
+    ID = DominatorNode.Parent->topologicalFinalSort(Blocks, ID);
+  for (auto *Pred : Predecessors)
+    ID = Pred->topologicalFinalSort(Blocks, ID);
+  assert(ID < Blocks.size());
+  BlockID = ID++;
+  Blocks[BlockID] = this;
+  return ID;
+}
+
+// Computes the immediate dominator of the current block.  Assumes that all of
+// its predecessors have already computed their dominators.  This is achieved
+// by visiting the nodes in topological order.
+void BasicBlock::computeDominator() {
+  BasicBlock *Candidate = nullptr;
+  // Walk backwards from each predecessor to find the common dominator node.
+  for (auto *Pred : Predecessors) {
+    // Skip back-edges
+    if (Pred->BlockID >= BlockID) continue;
+    // If we don't yet have a candidate for dominator yet, take this one.
+    if (Candidate == nullptr) {
+      Candidate = Pred;
+      continue;
+    }
+    // Walk the alternate and current candidate back to find a common ancestor.
+    auto *Alternate = Pred;
+    while (Alternate != Candidate) {
+      if (Candidate->BlockID > Alternate->BlockID)
+        Candidate = Candidate->DominatorNode.Parent;
+      else
+        Alternate = Alternate->DominatorNode.Parent;
+    }
+  }
+  DominatorNode.Parent = Candidate;
+  DominatorNode.SizeOfSubTree = 1;
+}
+
+// Computes the immediate post-dominator of the current block.  Assumes that all
+// of its successors have already computed their post-dominators.  This is
+// achieved visiting the nodes in reverse topological order.
+void BasicBlock::computePostDominator() {
+  BasicBlock *Candidate = nullptr;
+  // Walk back from each predecessor to find the common post-dominator node.
+  for (auto *Succ : successors()) {
+    // Skip back-edges
+    if (Succ->BlockID <= BlockID) continue;
+    // If we don't yet have a candidate for post-dominator yet, take this one.
+    if (Candidate == nullptr) {
+      Candidate = Succ;
+      continue;
+    }
+    // Walk the alternate and current candidate back to find a common ancestor.
+    auto *Alternate = Succ;
+    while (Alternate != Candidate) {
+      if (Candidate->BlockID < Alternate->BlockID)
+        Candidate = Candidate->PostDominatorNode.Parent;
+      else
+        Alternate = Alternate->PostDominatorNode.Parent;
+    }
+  }
+  PostDominatorNode.Parent = Candidate;
+  PostDominatorNode.SizeOfSubTree = 1;
+}
+
+
+// Renumber instructions in all blocks
+void SCFG::renumberInstrs() {
+  int InstrID = 0;
+  for (auto *Block : Blocks)
+    InstrID = Block->renumberInstrs(InstrID);
+}
+
+
+static inline void computeNodeSize(BasicBlock *B,
+                                   BasicBlock::TopologyNode BasicBlock::*TN) {
+  BasicBlock::TopologyNode *N = &(B->*TN);
+  if (N->Parent) {
+    BasicBlock::TopologyNode *P = &(N->Parent->*TN);
+    // Initially set ID relative to the (as yet uncomputed) parent ID
+    N->NodeID = P->SizeOfSubTree;
+    P->SizeOfSubTree += N->SizeOfSubTree;
+  }
+}
+
+static inline void computeNodeID(BasicBlock *B,
+                                 BasicBlock::TopologyNode BasicBlock::*TN) {
+  BasicBlock::TopologyNode *N = &(B->*TN);
+  if (N->Parent) {
+    BasicBlock::TopologyNode *P = &(N->Parent->*TN);
+    N->NodeID += P->NodeID;    // Fix NodeIDs relative to starting node.
+  }
+}
+
+
+// Normalizes a CFG.  Normalization has a few major components:
+// 1) Removing unreachable blocks.
+// 2) Computing dominators and post-dominators
+// 3) Topologically sorting the blocks into the "Blocks" array.
+void SCFG::computeNormalForm() {
+  // Topologically sort the blocks starting from the entry block.
+  int NumUnreachableBlocks = Entry->topologicalSort(Blocks, Blocks.size());
+  if (NumUnreachableBlocks > 0) {
+    // If there were unreachable blocks shift everything down, and delete them.
+    for (size_t I = NumUnreachableBlocks, E = Blocks.size(); I < E; ++I) {
+      size_t NI = I - NumUnreachableBlocks;
+      Blocks[NI] = Blocks[I];
+      Blocks[NI]->BlockID = NI;
+      // FIXME: clean up predecessor pointers to unreachable blocks?
+    }
+    Blocks.drop(NumUnreachableBlocks);
+  }
+
+  // Compute dominators.
+  for (auto *Block : Blocks)
+    Block->computeDominator();
+
+  // Once dominators have been computed, the final sort may be performed.
+  int NumBlocks = Exit->topologicalFinalSort(Blocks, 0);
+  assert(NumBlocks == Blocks.size());
+  (void) NumBlocks;
+
+  // Renumber the instructions now that we have a final sort.
+  renumberInstrs();
+
+  // Compute post-dominators and compute the sizes of each node in the
+  // dominator tree.
+  for (auto *Block : Blocks.reverse()) {
+    Block->computePostDominator();
+    computeNodeSize(Block, &BasicBlock::DominatorNode);
+  }
+  // Compute the sizes of each node in the post-dominator tree and assign IDs in
+  // the dominator tree.
+  for (auto *Block : Blocks) {
+    computeNodeID(Block, &BasicBlock::DominatorNode);
+    computeNodeSize(Block, &BasicBlock::PostDominatorNode);
+  }
+  // Assign IDs in the post-dominator tree.
+  for (auto *Block : Blocks.reverse()) {
+    computeNodeID(Block, &BasicBlock::PostDominatorNode);
+  }
+}
+
 }  // end namespace til
 }  // end namespace threadSafety
 }  // end namespace clang


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