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      1 //===--- CFG.h - Classes for representing and building CFGs------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file defines the CFG and CFGBuilder classes for representing and
     11 //  building Control-Flow Graphs (CFGs) from ASTs.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_CLANG_CFG_H
     16 #define LLVM_CLANG_CFG_H
     17 
     18 #include "clang/AST/Stmt.h"
     19 #include "clang/Analysis/Support/BumpVector.h"
     20 #include "clang/Basic/SourceLocation.h"
     21 #include "llvm/ADT/DenseMap.h"
     22 #include "llvm/ADT/GraphTraits.h"
     23 #include "llvm/ADT/Optional.h"
     24 #include "llvm/ADT/OwningPtr.h"
     25 #include "llvm/ADT/PointerIntPair.h"
     26 #include "llvm/Support/Allocator.h"
     27 #include "llvm/Support/Casting.h"
     28 #include <bitset>
     29 #include <cassert>
     30 #include <iterator>
     31 
     32 namespace clang {
     33   class CXXDestructorDecl;
     34   class Decl;
     35   class Stmt;
     36   class Expr;
     37   class FieldDecl;
     38   class VarDecl;
     39   class CXXCtorInitializer;
     40   class CXXBaseSpecifier;
     41   class CXXBindTemporaryExpr;
     42   class CFG;
     43   class PrinterHelper;
     44   class LangOptions;
     45   class ASTContext;
     46 
     47 /// CFGElement - Represents a top-level expression in a basic block.
     48 class CFGElement {
     49 public:
     50   enum Kind {
     51     // main kind
     52     Statement,
     53     Initializer,
     54     // dtor kind
     55     AutomaticObjectDtor,
     56     BaseDtor,
     57     MemberDtor,
     58     TemporaryDtor,
     59     DTOR_BEGIN = AutomaticObjectDtor,
     60     DTOR_END = TemporaryDtor
     61   };
     62 
     63 protected:
     64   // The int bits are used to mark the kind.
     65   llvm::PointerIntPair<void *, 2> Data1;
     66   llvm::PointerIntPair<void *, 2> Data2;
     67 
     68   CFGElement(Kind kind, const void *Ptr1, const void *Ptr2 = 0)
     69     : Data1(const_cast<void*>(Ptr1), ((unsigned) kind) & 0x3),
     70       Data2(const_cast<void*>(Ptr2), (((unsigned) kind) >> 2) & 0x3) {}
     71 
     72   CFGElement() {}
     73 public:
     74 
     75   /// \brief Convert to the specified CFGElement type, asserting that this
     76   /// CFGElement is of the desired type.
     77   template<typename T>
     78   T castAs() const {
     79     assert(T::isKind(*this));
     80     T t;
     81     CFGElement& e = t;
     82     e = *this;
     83     return t;
     84   }
     85 
     86   /// \brief Convert to the specified CFGElement type, returning None if this
     87   /// CFGElement is not of the desired type.
     88   template<typename T>
     89   Optional<T> getAs() const {
     90     if (!T::isKind(*this))
     91       return None;
     92     T t;
     93     CFGElement& e = t;
     94     e = *this;
     95     return t;
     96   }
     97 
     98   Kind getKind() const {
     99     unsigned x = Data2.getInt();
    100     x <<= 2;
    101     x |= Data1.getInt();
    102     return (Kind) x;
    103   }
    104 };
    105 
    106 class CFGStmt : public CFGElement {
    107 public:
    108   CFGStmt(Stmt *S) : CFGElement(Statement, S) {}
    109 
    110   const Stmt *getStmt() const {
    111     return static_cast<const Stmt *>(Data1.getPointer());
    112   }
    113 
    114 private:
    115   friend class CFGElement;
    116   CFGStmt() {}
    117   static bool isKind(const CFGElement &E) {
    118     return E.getKind() == Statement;
    119   }
    120 };
    121 
    122 /// CFGInitializer - Represents C++ base or member initializer from
    123 /// constructor's initialization list.
    124 class CFGInitializer : public CFGElement {
    125 public:
    126   CFGInitializer(CXXCtorInitializer *initializer)
    127       : CFGElement(Initializer, initializer) {}
    128 
    129   CXXCtorInitializer* getInitializer() const {
    130     return static_cast<CXXCtorInitializer*>(Data1.getPointer());
    131   }
    132 
    133 private:
    134   friend class CFGElement;
    135   CFGInitializer() {}
    136   static bool isKind(const CFGElement &E) {
    137     return E.getKind() == Initializer;
    138   }
    139 };
    140 
    141 /// CFGImplicitDtor - Represents C++ object destructor implicitly generated
    142 /// by compiler on various occasions.
    143 class CFGImplicitDtor : public CFGElement {
    144 protected:
    145   CFGImplicitDtor() {}
    146   CFGImplicitDtor(Kind kind, const void *data1, const void *data2 = 0)
    147     : CFGElement(kind, data1, data2) {
    148     assert(kind >= DTOR_BEGIN && kind <= DTOR_END);
    149   }
    150 
    151 public:
    152   const CXXDestructorDecl *getDestructorDecl(ASTContext &astContext) const;
    153   bool isNoReturn(ASTContext &astContext) const;
    154 
    155 private:
    156   friend class CFGElement;
    157   static bool isKind(const CFGElement &E) {
    158     Kind kind = E.getKind();
    159     return kind >= DTOR_BEGIN && kind <= DTOR_END;
    160   }
    161 };
    162 
    163 /// CFGAutomaticObjDtor - Represents C++ object destructor implicitly generated
    164 /// for automatic object or temporary bound to const reference at the point
    165 /// of leaving its local scope.
    166 class CFGAutomaticObjDtor: public CFGImplicitDtor {
    167 public:
    168   CFGAutomaticObjDtor(const VarDecl *var, const Stmt *stmt)
    169       : CFGImplicitDtor(AutomaticObjectDtor, var, stmt) {}
    170 
    171   const VarDecl *getVarDecl() const {
    172     return static_cast<VarDecl*>(Data1.getPointer());
    173   }
    174 
    175   // Get statement end of which triggered the destructor call.
    176   const Stmt *getTriggerStmt() const {
    177     return static_cast<Stmt*>(Data2.getPointer());
    178   }
    179 
    180 private:
    181   friend class CFGElement;
    182   CFGAutomaticObjDtor() {}
    183   static bool isKind(const CFGElement &elem) {
    184     return elem.getKind() == AutomaticObjectDtor;
    185   }
    186 };
    187 
    188 /// CFGBaseDtor - Represents C++ object destructor implicitly generated for
    189 /// base object in destructor.
    190 class CFGBaseDtor : public CFGImplicitDtor {
    191 public:
    192   CFGBaseDtor(const CXXBaseSpecifier *base)
    193       : CFGImplicitDtor(BaseDtor, base) {}
    194 
    195   const CXXBaseSpecifier *getBaseSpecifier() const {
    196     return static_cast<const CXXBaseSpecifier*>(Data1.getPointer());
    197   }
    198 
    199 private:
    200   friend class CFGElement;
    201   CFGBaseDtor() {}
    202   static bool isKind(const CFGElement &E) {
    203     return E.getKind() == BaseDtor;
    204   }
    205 };
    206 
    207 /// CFGMemberDtor - Represents C++ object destructor implicitly generated for
    208 /// member object in destructor.
    209 class CFGMemberDtor : public CFGImplicitDtor {
    210 public:
    211   CFGMemberDtor(const FieldDecl *field)
    212       : CFGImplicitDtor(MemberDtor, field, 0) {}
    213 
    214   const FieldDecl *getFieldDecl() const {
    215     return static_cast<const FieldDecl*>(Data1.getPointer());
    216   }
    217 
    218 private:
    219   friend class CFGElement;
    220   CFGMemberDtor() {}
    221   static bool isKind(const CFGElement &E) {
    222     return E.getKind() == MemberDtor;
    223   }
    224 };
    225 
    226 /// CFGTemporaryDtor - Represents C++ object destructor implicitly generated
    227 /// at the end of full expression for temporary object.
    228 class CFGTemporaryDtor : public CFGImplicitDtor {
    229 public:
    230   CFGTemporaryDtor(CXXBindTemporaryExpr *expr)
    231       : CFGImplicitDtor(TemporaryDtor, expr, 0) {}
    232 
    233   const CXXBindTemporaryExpr *getBindTemporaryExpr() const {
    234     return static_cast<const CXXBindTemporaryExpr *>(Data1.getPointer());
    235   }
    236 
    237 private:
    238   friend class CFGElement;
    239   CFGTemporaryDtor() {}
    240   static bool isKind(const CFGElement &E) {
    241     return E.getKind() == TemporaryDtor;
    242   }
    243 };
    244 
    245 /// CFGTerminator - Represents CFGBlock terminator statement.
    246 ///
    247 /// TemporaryDtorsBranch bit is set to true if the terminator marks a branch
    248 /// in control flow of destructors of temporaries. In this case terminator
    249 /// statement is the same statement that branches control flow in evaluation
    250 /// of matching full expression.
    251 class CFGTerminator {
    252   llvm::PointerIntPair<Stmt *, 1> Data;
    253 public:
    254   CFGTerminator() {}
    255   CFGTerminator(Stmt *S, bool TemporaryDtorsBranch = false)
    256       : Data(S, TemporaryDtorsBranch) {}
    257 
    258   Stmt *getStmt() { return Data.getPointer(); }
    259   const Stmt *getStmt() const { return Data.getPointer(); }
    260 
    261   bool isTemporaryDtorsBranch() const { return Data.getInt(); }
    262 
    263   operator Stmt *() { return getStmt(); }
    264   operator const Stmt *() const { return getStmt(); }
    265 
    266   Stmt *operator->() { return getStmt(); }
    267   const Stmt *operator->() const { return getStmt(); }
    268 
    269   Stmt &operator*() { return *getStmt(); }
    270   const Stmt &operator*() const { return *getStmt(); }
    271 
    272   LLVM_EXPLICIT operator bool() const { return getStmt(); }
    273 };
    274 
    275 /// CFGBlock - Represents a single basic block in a source-level CFG.
    276 ///  It consists of:
    277 ///
    278 ///  (1) A set of statements/expressions (which may contain subexpressions).
    279 ///  (2) A "terminator" statement (not in the set of statements).
    280 ///  (3) A list of successors and predecessors.
    281 ///
    282 /// Terminator: The terminator represents the type of control-flow that occurs
    283 /// at the end of the basic block.  The terminator is a Stmt* referring to an
    284 /// AST node that has control-flow: if-statements, breaks, loops, etc.
    285 /// If the control-flow is conditional, the condition expression will appear
    286 /// within the set of statements in the block (usually the last statement).
    287 ///
    288 /// Predecessors: the order in the set of predecessors is arbitrary.
    289 ///
    290 /// Successors: the order in the set of successors is NOT arbitrary.  We
    291 ///  currently have the following orderings based on the terminator:
    292 ///
    293 ///     Terminator       Successor Ordering
    294 ///  -----------------------------------------------------
    295 ///       if            Then Block;  Else Block
    296 ///     ? operator      LHS expression;  RHS expression
    297 ///     &&, ||          expression that uses result of && or ||, RHS
    298 ///
    299 /// But note that any of that may be NULL in case of optimized-out edges.
    300 ///
    301 class CFGBlock {
    302   class ElementList {
    303     typedef BumpVector<CFGElement> ImplTy;
    304     ImplTy Impl;
    305   public:
    306     ElementList(BumpVectorContext &C) : Impl(C, 4) {}
    307 
    308     typedef std::reverse_iterator<ImplTy::iterator>       iterator;
    309     typedef std::reverse_iterator<ImplTy::const_iterator> const_iterator;
    310     typedef ImplTy::iterator                              reverse_iterator;
    311     typedef ImplTy::const_iterator                       const_reverse_iterator;
    312     typedef ImplTy::const_reference                       const_reference;
    313 
    314     void push_back(CFGElement e, BumpVectorContext &C) { Impl.push_back(e, C); }
    315     reverse_iterator insert(reverse_iterator I, size_t Cnt, CFGElement E,
    316         BumpVectorContext &C) {
    317       return Impl.insert(I, Cnt, E, C);
    318     }
    319 
    320     const_reference front() const { return Impl.back(); }
    321     const_reference back() const { return Impl.front(); }
    322 
    323     iterator begin() { return Impl.rbegin(); }
    324     iterator end() { return Impl.rend(); }
    325     const_iterator begin() const { return Impl.rbegin(); }
    326     const_iterator end() const { return Impl.rend(); }
    327     reverse_iterator rbegin() { return Impl.begin(); }
    328     reverse_iterator rend() { return Impl.end(); }
    329     const_reverse_iterator rbegin() const { return Impl.begin(); }
    330     const_reverse_iterator rend() const { return Impl.end(); }
    331 
    332    CFGElement operator[](size_t i) const  {
    333      assert(i < Impl.size());
    334      return Impl[Impl.size() - 1 - i];
    335    }
    336 
    337     size_t size() const { return Impl.size(); }
    338     bool empty() const { return Impl.empty(); }
    339   };
    340 
    341   /// Stmts - The set of statements in the basic block.
    342   ElementList Elements;
    343 
    344   /// Label - An (optional) label that prefixes the executable
    345   ///  statements in the block.  When this variable is non-NULL, it is
    346   ///  either an instance of LabelStmt, SwitchCase or CXXCatchStmt.
    347   Stmt *Label;
    348 
    349   /// Terminator - The terminator for a basic block that
    350   ///  indicates the type of control-flow that occurs between a block
    351   ///  and its successors.
    352   CFGTerminator Terminator;
    353 
    354   /// LoopTarget - Some blocks are used to represent the "loop edge" to
    355   ///  the start of a loop from within the loop body.  This Stmt* will be
    356   ///  refer to the loop statement for such blocks (and be null otherwise).
    357   const Stmt *LoopTarget;
    358 
    359   /// BlockID - A numerical ID assigned to a CFGBlock during construction
    360   ///   of the CFG.
    361   unsigned BlockID;
    362 
    363   /// Predecessors/Successors - Keep track of the predecessor / successor
    364   /// CFG blocks.
    365   typedef BumpVector<CFGBlock*> AdjacentBlocks;
    366   AdjacentBlocks Preds;
    367   AdjacentBlocks Succs;
    368 
    369   /// NoReturn - This bit is set when the basic block contains a function call
    370   /// or implicit destructor that is attributed as 'noreturn'. In that case,
    371   /// control cannot technically ever proceed past this block. All such blocks
    372   /// will have a single immediate successor: the exit block. This allows them
    373   /// to be easily reached from the exit block and using this bit quickly
    374   /// recognized without scanning the contents of the block.
    375   ///
    376   /// Optimization Note: This bit could be profitably folded with Terminator's
    377   /// storage if the memory usage of CFGBlock becomes an issue.
    378   unsigned HasNoReturnElement : 1;
    379 
    380   /// Parent - The parent CFG that owns this CFGBlock.
    381   CFG *Parent;
    382 
    383 public:
    384   explicit CFGBlock(unsigned blockid, BumpVectorContext &C, CFG *parent)
    385     : Elements(C), Label(NULL), Terminator(NULL), LoopTarget(NULL),
    386       BlockID(blockid), Preds(C, 1), Succs(C, 1), HasNoReturnElement(false),
    387       Parent(parent) {}
    388   ~CFGBlock() {}
    389 
    390   // Statement iterators
    391   typedef ElementList::iterator                      iterator;
    392   typedef ElementList::const_iterator                const_iterator;
    393   typedef ElementList::reverse_iterator              reverse_iterator;
    394   typedef ElementList::const_reverse_iterator        const_reverse_iterator;
    395 
    396   CFGElement                 front()       const { return Elements.front();   }
    397   CFGElement                 back()        const { return Elements.back();    }
    398 
    399   iterator                   begin()             { return Elements.begin();   }
    400   iterator                   end()               { return Elements.end();     }
    401   const_iterator             begin()       const { return Elements.begin();   }
    402   const_iterator             end()         const { return Elements.end();     }
    403 
    404   reverse_iterator           rbegin()            { return Elements.rbegin();  }
    405   reverse_iterator           rend()              { return Elements.rend();    }
    406   const_reverse_iterator     rbegin()      const { return Elements.rbegin();  }
    407   const_reverse_iterator     rend()        const { return Elements.rend();    }
    408 
    409   unsigned                   size()        const { return Elements.size();    }
    410   bool                       empty()       const { return Elements.empty();   }
    411 
    412   CFGElement operator[](size_t i) const  { return Elements[i]; }
    413 
    414   // CFG iterators
    415   typedef AdjacentBlocks::iterator                              pred_iterator;
    416   typedef AdjacentBlocks::const_iterator                  const_pred_iterator;
    417   typedef AdjacentBlocks::reverse_iterator              pred_reverse_iterator;
    418   typedef AdjacentBlocks::const_reverse_iterator  const_pred_reverse_iterator;
    419 
    420   typedef AdjacentBlocks::iterator                              succ_iterator;
    421   typedef AdjacentBlocks::const_iterator                  const_succ_iterator;
    422   typedef AdjacentBlocks::reverse_iterator              succ_reverse_iterator;
    423   typedef AdjacentBlocks::const_reverse_iterator  const_succ_reverse_iterator;
    424 
    425   pred_iterator                pred_begin()        { return Preds.begin();   }
    426   pred_iterator                pred_end()          { return Preds.end();     }
    427   const_pred_iterator          pred_begin()  const { return Preds.begin();   }
    428   const_pred_iterator          pred_end()    const { return Preds.end();     }
    429 
    430   pred_reverse_iterator        pred_rbegin()       { return Preds.rbegin();  }
    431   pred_reverse_iterator        pred_rend()         { return Preds.rend();    }
    432   const_pred_reverse_iterator  pred_rbegin() const { return Preds.rbegin();  }
    433   const_pred_reverse_iterator  pred_rend()   const { return Preds.rend();    }
    434 
    435   succ_iterator                succ_begin()        { return Succs.begin();   }
    436   succ_iterator                succ_end()          { return Succs.end();     }
    437   const_succ_iterator          succ_begin()  const { return Succs.begin();   }
    438   const_succ_iterator          succ_end()    const { return Succs.end();     }
    439 
    440   succ_reverse_iterator        succ_rbegin()       { return Succs.rbegin();  }
    441   succ_reverse_iterator        succ_rend()         { return Succs.rend();    }
    442   const_succ_reverse_iterator  succ_rbegin() const { return Succs.rbegin();  }
    443   const_succ_reverse_iterator  succ_rend()   const { return Succs.rend();    }
    444 
    445   unsigned                     succ_size()   const { return Succs.size();    }
    446   bool                         succ_empty()  const { return Succs.empty();   }
    447 
    448   unsigned                     pred_size()   const { return Preds.size();    }
    449   bool                         pred_empty()  const { return Preds.empty();   }
    450 
    451 
    452   class FilterOptions {
    453   public:
    454     FilterOptions() {
    455       IgnoreDefaultsWithCoveredEnums = 0;
    456     }
    457 
    458     unsigned IgnoreDefaultsWithCoveredEnums : 1;
    459   };
    460 
    461   static bool FilterEdge(const FilterOptions &F, const CFGBlock *Src,
    462        const CFGBlock *Dst);
    463 
    464   template <typename IMPL, bool IsPred>
    465   class FilteredCFGBlockIterator {
    466   private:
    467     IMPL I, E;
    468     const FilterOptions F;
    469     const CFGBlock *From;
    470    public:
    471     explicit FilteredCFGBlockIterator(const IMPL &i, const IMPL &e,
    472               const CFGBlock *from,
    473               const FilterOptions &f)
    474       : I(i), E(e), F(f), From(from) {}
    475 
    476     bool hasMore() const { return I != E; }
    477 
    478     FilteredCFGBlockIterator &operator++() {
    479       do { ++I; } while (hasMore() && Filter(*I));
    480       return *this;
    481     }
    482 
    483     const CFGBlock *operator*() const { return *I; }
    484   private:
    485     bool Filter(const CFGBlock *To) {
    486       return IsPred ? FilterEdge(F, To, From) : FilterEdge(F, From, To);
    487     }
    488   };
    489 
    490   typedef FilteredCFGBlockIterator<const_pred_iterator, true>
    491           filtered_pred_iterator;
    492 
    493   typedef FilteredCFGBlockIterator<const_succ_iterator, false>
    494           filtered_succ_iterator;
    495 
    496   filtered_pred_iterator filtered_pred_start_end(const FilterOptions &f) const {
    497     return filtered_pred_iterator(pred_begin(), pred_end(), this, f);
    498   }
    499 
    500   filtered_succ_iterator filtered_succ_start_end(const FilterOptions &f) const {
    501     return filtered_succ_iterator(succ_begin(), succ_end(), this, f);
    502   }
    503 
    504   // Manipulation of block contents
    505 
    506   void setTerminator(Stmt *Statement) { Terminator = Statement; }
    507   void setLabel(Stmt *Statement) { Label = Statement; }
    508   void setLoopTarget(const Stmt *loopTarget) { LoopTarget = loopTarget; }
    509   void setHasNoReturnElement() { HasNoReturnElement = true; }
    510 
    511   CFGTerminator getTerminator() { return Terminator; }
    512   const CFGTerminator getTerminator() const { return Terminator; }
    513 
    514   Stmt *getTerminatorCondition();
    515 
    516   const Stmt *getTerminatorCondition() const {
    517     return const_cast<CFGBlock*>(this)->getTerminatorCondition();
    518   }
    519 
    520   const Stmt *getLoopTarget() const { return LoopTarget; }
    521 
    522   Stmt *getLabel() { return Label; }
    523   const Stmt *getLabel() const { return Label; }
    524 
    525   bool hasNoReturnElement() const { return HasNoReturnElement; }
    526 
    527   unsigned getBlockID() const { return BlockID; }
    528 
    529   CFG *getParent() const { return Parent; }
    530 
    531   void dump(const CFG *cfg, const LangOptions &LO, bool ShowColors = false) const;
    532   void print(raw_ostream &OS, const CFG* cfg, const LangOptions &LO,
    533              bool ShowColors) const;
    534   void printTerminator(raw_ostream &OS, const LangOptions &LO) const;
    535 
    536   void addSuccessor(CFGBlock *Block, BumpVectorContext &C) {
    537     if (Block)
    538       Block->Preds.push_back(this, C);
    539     Succs.push_back(Block, C);
    540   }
    541 
    542   void appendStmt(Stmt *statement, BumpVectorContext &C) {
    543     Elements.push_back(CFGStmt(statement), C);
    544   }
    545 
    546   void appendInitializer(CXXCtorInitializer *initializer,
    547                         BumpVectorContext &C) {
    548     Elements.push_back(CFGInitializer(initializer), C);
    549   }
    550 
    551   void appendBaseDtor(const CXXBaseSpecifier *BS, BumpVectorContext &C) {
    552     Elements.push_back(CFGBaseDtor(BS), C);
    553   }
    554 
    555   void appendMemberDtor(FieldDecl *FD, BumpVectorContext &C) {
    556     Elements.push_back(CFGMemberDtor(FD), C);
    557   }
    558 
    559   void appendTemporaryDtor(CXXBindTemporaryExpr *E, BumpVectorContext &C) {
    560     Elements.push_back(CFGTemporaryDtor(E), C);
    561   }
    562 
    563   void appendAutomaticObjDtor(VarDecl *VD, Stmt *S, BumpVectorContext &C) {
    564     Elements.push_back(CFGAutomaticObjDtor(VD, S), C);
    565   }
    566 
    567   // Destructors must be inserted in reversed order. So insertion is in two
    568   // steps. First we prepare space for some number of elements, then we insert
    569   // the elements beginning at the last position in prepared space.
    570   iterator beginAutomaticObjDtorsInsert(iterator I, size_t Cnt,
    571       BumpVectorContext &C) {
    572     return iterator(Elements.insert(I.base(), Cnt, CFGAutomaticObjDtor(0, 0), C));
    573   }
    574   iterator insertAutomaticObjDtor(iterator I, VarDecl *VD, Stmt *S) {
    575     *I = CFGAutomaticObjDtor(VD, S);
    576     return ++I;
    577   }
    578 };
    579 
    580 /// CFG - Represents a source-level, intra-procedural CFG that represents the
    581 ///  control-flow of a Stmt.  The Stmt can represent an entire function body,
    582 ///  or a single expression.  A CFG will always contain one empty block that
    583 ///  represents the Exit point of the CFG.  A CFG will also contain a designated
    584 ///  Entry block.  The CFG solely represents control-flow; it consists of
    585 ///  CFGBlocks which are simply containers of Stmt*'s in the AST the CFG
    586 ///  was constructed from.
    587 class CFG {
    588 public:
    589   //===--------------------------------------------------------------------===//
    590   // CFG Construction & Manipulation.
    591   //===--------------------------------------------------------------------===//
    592 
    593   class BuildOptions {
    594     std::bitset<Stmt::lastStmtConstant> alwaysAddMask;
    595   public:
    596     typedef llvm::DenseMap<const Stmt *, const CFGBlock*> ForcedBlkExprs;
    597     ForcedBlkExprs **forcedBlkExprs;
    598 
    599     bool PruneTriviallyFalseEdges;
    600     bool AddEHEdges;
    601     bool AddInitializers;
    602     bool AddImplicitDtors;
    603     bool AddTemporaryDtors;
    604     bool AddStaticInitBranches;
    605 
    606     bool alwaysAdd(const Stmt *stmt) const {
    607       return alwaysAddMask[stmt->getStmtClass()];
    608     }
    609 
    610     BuildOptions &setAlwaysAdd(Stmt::StmtClass stmtClass, bool val = true) {
    611       alwaysAddMask[stmtClass] = val;
    612       return *this;
    613     }
    614 
    615     BuildOptions &setAllAlwaysAdd() {
    616       alwaysAddMask.set();
    617       return *this;
    618     }
    619 
    620     BuildOptions()
    621     : forcedBlkExprs(0), PruneTriviallyFalseEdges(true)
    622       ,AddEHEdges(false)
    623       ,AddInitializers(false)
    624       ,AddImplicitDtors(false)
    625       ,AddTemporaryDtors(false)
    626       ,AddStaticInitBranches(false) {}
    627   };
    628 
    629   /// \brief Provides a custom implementation of the iterator class to have the
    630   /// same interface as Function::iterator - iterator returns CFGBlock
    631   /// (not a pointer to CFGBlock).
    632   class graph_iterator {
    633   public:
    634     typedef const CFGBlock                  value_type;
    635     typedef value_type&                     reference;
    636     typedef value_type*                     pointer;
    637     typedef BumpVector<CFGBlock*>::iterator ImplTy;
    638 
    639     graph_iterator(const ImplTy &i) : I(i) {}
    640 
    641     bool operator==(const graph_iterator &X) const { return I == X.I; }
    642     bool operator!=(const graph_iterator &X) const { return I != X.I; }
    643 
    644     reference operator*()    const { return **I; }
    645     pointer operator->()     const { return  *I; }
    646     operator CFGBlock* ()          { return  *I; }
    647 
    648     graph_iterator &operator++() { ++I; return *this; }
    649     graph_iterator &operator--() { --I; return *this; }
    650 
    651   private:
    652     ImplTy I;
    653   };
    654 
    655   class const_graph_iterator {
    656   public:
    657     typedef const CFGBlock                  value_type;
    658     typedef value_type&                     reference;
    659     typedef value_type*                     pointer;
    660     typedef BumpVector<CFGBlock*>::const_iterator ImplTy;
    661 
    662     const_graph_iterator(const ImplTy &i) : I(i) {}
    663 
    664     bool operator==(const const_graph_iterator &X) const { return I == X.I; }
    665     bool operator!=(const const_graph_iterator &X) const { return I != X.I; }
    666 
    667     reference operator*() const { return **I; }
    668     pointer operator->()  const { return  *I; }
    669     operator CFGBlock* () const { return  *I; }
    670 
    671     const_graph_iterator &operator++() { ++I; return *this; }
    672     const_graph_iterator &operator--() { --I; return *this; }
    673 
    674   private:
    675     ImplTy I;
    676   };
    677 
    678   /// buildCFG - Builds a CFG from an AST.  The responsibility to free the
    679   ///   constructed CFG belongs to the caller.
    680   static CFG* buildCFG(const Decl *D, Stmt *AST, ASTContext *C,
    681                        const BuildOptions &BO);
    682 
    683   /// createBlock - Create a new block in the CFG.  The CFG owns the block;
    684   ///  the caller should not directly free it.
    685   CFGBlock *createBlock();
    686 
    687   /// setEntry - Set the entry block of the CFG.  This is typically used
    688   ///  only during CFG construction.  Most CFG clients expect that the
    689   ///  entry block has no predecessors and contains no statements.
    690   void setEntry(CFGBlock *B) { Entry = B; }
    691 
    692   /// setIndirectGotoBlock - Set the block used for indirect goto jumps.
    693   ///  This is typically used only during CFG construction.
    694   void setIndirectGotoBlock(CFGBlock *B) { IndirectGotoBlock = B; }
    695 
    696   //===--------------------------------------------------------------------===//
    697   // Block Iterators
    698   //===--------------------------------------------------------------------===//
    699 
    700   typedef BumpVector<CFGBlock*>                    CFGBlockListTy;
    701   typedef CFGBlockListTy::iterator                 iterator;
    702   typedef CFGBlockListTy::const_iterator           const_iterator;
    703   typedef std::reverse_iterator<iterator>          reverse_iterator;
    704   typedef std::reverse_iterator<const_iterator>    const_reverse_iterator;
    705 
    706   CFGBlock &                front()                { return *Blocks.front(); }
    707   CFGBlock &                back()                 { return *Blocks.back(); }
    708 
    709   iterator                  begin()                { return Blocks.begin(); }
    710   iterator                  end()                  { return Blocks.end(); }
    711   const_iterator            begin()       const    { return Blocks.begin(); }
    712   const_iterator            end()         const    { return Blocks.end(); }
    713 
    714   graph_iterator nodes_begin() { return graph_iterator(Blocks.begin()); }
    715   graph_iterator nodes_end() { return graph_iterator(Blocks.end()); }
    716   const_graph_iterator nodes_begin() const {
    717     return const_graph_iterator(Blocks.begin());
    718   }
    719   const_graph_iterator nodes_end() const {
    720     return const_graph_iterator(Blocks.end());
    721   }
    722 
    723   reverse_iterator          rbegin()               { return Blocks.rbegin(); }
    724   reverse_iterator          rend()                 { return Blocks.rend(); }
    725   const_reverse_iterator    rbegin()      const    { return Blocks.rbegin(); }
    726   const_reverse_iterator    rend()        const    { return Blocks.rend(); }
    727 
    728   CFGBlock &                getEntry()             { return *Entry; }
    729   const CFGBlock &          getEntry()    const    { return *Entry; }
    730   CFGBlock &                getExit()              { return *Exit; }
    731   const CFGBlock &          getExit()     const    { return *Exit; }
    732 
    733   CFGBlock *       getIndirectGotoBlock() { return IndirectGotoBlock; }
    734   const CFGBlock * getIndirectGotoBlock() const { return IndirectGotoBlock; }
    735 
    736   typedef std::vector<const CFGBlock*>::const_iterator try_block_iterator;
    737   try_block_iterator try_blocks_begin() const {
    738     return TryDispatchBlocks.begin();
    739   }
    740   try_block_iterator try_blocks_end() const {
    741     return TryDispatchBlocks.end();
    742   }
    743 
    744   void addTryDispatchBlock(const CFGBlock *block) {
    745     TryDispatchBlocks.push_back(block);
    746   }
    747 
    748   /// Records a synthetic DeclStmt and the DeclStmt it was constructed from.
    749   ///
    750   /// The CFG uses synthetic DeclStmts when a single AST DeclStmt contains
    751   /// multiple decls.
    752   void addSyntheticDeclStmt(const DeclStmt *Synthetic,
    753                             const DeclStmt *Source) {
    754     assert(Synthetic->isSingleDecl() && "Can handle single declarations only");
    755     assert(Synthetic != Source && "Don't include original DeclStmts in map");
    756     assert(!SyntheticDeclStmts.count(Synthetic) && "Already in map");
    757     SyntheticDeclStmts[Synthetic] = Source;
    758   }
    759 
    760   typedef llvm::DenseMap<const DeclStmt *, const DeclStmt *>::const_iterator
    761     synthetic_stmt_iterator;
    762 
    763   /// Iterates over synthetic DeclStmts in the CFG.
    764   ///
    765   /// Each element is a (synthetic statement, source statement) pair.
    766   ///
    767   /// \sa addSyntheticDeclStmt
    768   synthetic_stmt_iterator synthetic_stmt_begin() const {
    769     return SyntheticDeclStmts.begin();
    770   }
    771 
    772   /// \sa synthetic_stmt_begin
    773   synthetic_stmt_iterator synthetic_stmt_end() const {
    774     return SyntheticDeclStmts.end();
    775   }
    776 
    777   //===--------------------------------------------------------------------===//
    778   // Member templates useful for various batch operations over CFGs.
    779   //===--------------------------------------------------------------------===//
    780 
    781   template <typename CALLBACK>
    782   void VisitBlockStmts(CALLBACK& O) const {
    783     for (const_iterator I=begin(), E=end(); I != E; ++I)
    784       for (CFGBlock::const_iterator BI=(*I)->begin(), BE=(*I)->end();
    785            BI != BE; ++BI) {
    786         if (Optional<CFGStmt> stmt = BI->getAs<CFGStmt>())
    787           O(const_cast<Stmt*>(stmt->getStmt()));
    788       }
    789   }
    790 
    791   //===--------------------------------------------------------------------===//
    792   // CFG Introspection.
    793   //===--------------------------------------------------------------------===//
    794 
    795   /// getNumBlockIDs - Returns the total number of BlockIDs allocated (which
    796   /// start at 0).
    797   unsigned getNumBlockIDs() const { return NumBlockIDs; }
    798 
    799   /// size - Return the total number of CFGBlocks within the CFG
    800   /// This is simply a renaming of the getNumBlockIDs(). This is necessary
    801   /// because the dominator implementation needs such an interface.
    802   unsigned size() const { return NumBlockIDs; }
    803 
    804   //===--------------------------------------------------------------------===//
    805   // CFG Debugging: Pretty-Printing and Visualization.
    806   //===--------------------------------------------------------------------===//
    807 
    808   void viewCFG(const LangOptions &LO) const;
    809   void print(raw_ostream &OS, const LangOptions &LO, bool ShowColors) const;
    810   void dump(const LangOptions &LO, bool ShowColors) const;
    811 
    812   //===--------------------------------------------------------------------===//
    813   // Internal: constructors and data.
    814   //===--------------------------------------------------------------------===//
    815 
    816   CFG() : Entry(NULL), Exit(NULL), IndirectGotoBlock(NULL), NumBlockIDs(0),
    817           Blocks(BlkBVC, 10) {}
    818 
    819   llvm::BumpPtrAllocator& getAllocator() {
    820     return BlkBVC.getAllocator();
    821   }
    822 
    823   BumpVectorContext &getBumpVectorContext() {
    824     return BlkBVC;
    825   }
    826 
    827 private:
    828   CFGBlock *Entry;
    829   CFGBlock *Exit;
    830   CFGBlock* IndirectGotoBlock;  // Special block to contain collective dispatch
    831                                 // for indirect gotos
    832   unsigned  NumBlockIDs;
    833 
    834   BumpVectorContext BlkBVC;
    835 
    836   CFGBlockListTy Blocks;
    837 
    838   /// C++ 'try' statements are modeled with an indirect dispatch block.
    839   /// This is the collection of such blocks present in the CFG.
    840   std::vector<const CFGBlock *> TryDispatchBlocks;
    841 
    842   /// Collects DeclStmts synthesized for this CFG and maps each one back to its
    843   /// source DeclStmt.
    844   llvm::DenseMap<const DeclStmt *, const DeclStmt *> SyntheticDeclStmts;
    845 };
    846 } // end namespace clang
    847 
    848 //===----------------------------------------------------------------------===//
    849 // GraphTraits specializations for CFG basic block graphs (source-level CFGs)
    850 //===----------------------------------------------------------------------===//
    851 
    852 namespace llvm {
    853 
    854 /// Implement simplify_type for CFGTerminator, so that we can dyn_cast from
    855 /// CFGTerminator to a specific Stmt class.
    856 template <> struct simplify_type< ::clang::CFGTerminator> {
    857   typedef ::clang::Stmt *SimpleType;
    858   static SimpleType getSimplifiedValue(::clang::CFGTerminator Val) {
    859     return Val.getStmt();
    860   }
    861 };
    862 
    863 // Traits for: CFGBlock
    864 
    865 template <> struct GraphTraits< ::clang::CFGBlock *> {
    866   typedef ::clang::CFGBlock NodeType;
    867   typedef ::clang::CFGBlock::succ_iterator ChildIteratorType;
    868 
    869   static NodeType* getEntryNode(::clang::CFGBlock *BB)
    870   { return BB; }
    871 
    872   static inline ChildIteratorType child_begin(NodeType* N)
    873   { return N->succ_begin(); }
    874 
    875   static inline ChildIteratorType child_end(NodeType* N)
    876   { return N->succ_end(); }
    877 };
    878 
    879 template <> struct GraphTraits< const ::clang::CFGBlock *> {
    880   typedef const ::clang::CFGBlock NodeType;
    881   typedef ::clang::CFGBlock::const_succ_iterator ChildIteratorType;
    882 
    883   static NodeType* getEntryNode(const clang::CFGBlock *BB)
    884   { return BB; }
    885 
    886   static inline ChildIteratorType child_begin(NodeType* N)
    887   { return N->succ_begin(); }
    888 
    889   static inline ChildIteratorType child_end(NodeType* N)
    890   { return N->succ_end(); }
    891 };
    892 
    893 template <> struct GraphTraits<Inverse< ::clang::CFGBlock*> > {
    894   typedef ::clang::CFGBlock NodeType;
    895   typedef ::clang::CFGBlock::const_pred_iterator ChildIteratorType;
    896 
    897   static NodeType *getEntryNode(Inverse< ::clang::CFGBlock*> G)
    898   { return G.Graph; }
    899 
    900   static inline ChildIteratorType child_begin(NodeType* N)
    901   { return N->pred_begin(); }
    902 
    903   static inline ChildIteratorType child_end(NodeType* N)
    904   { return N->pred_end(); }
    905 };
    906 
    907 template <> struct GraphTraits<Inverse<const ::clang::CFGBlock*> > {
    908   typedef const ::clang::CFGBlock NodeType;
    909   typedef ::clang::CFGBlock::const_pred_iterator ChildIteratorType;
    910 
    911   static NodeType *getEntryNode(Inverse<const ::clang::CFGBlock*> G)
    912   { return G.Graph; }
    913 
    914   static inline ChildIteratorType child_begin(NodeType* N)
    915   { return N->pred_begin(); }
    916 
    917   static inline ChildIteratorType child_end(NodeType* N)
    918   { return N->pred_end(); }
    919 };
    920 
    921 // Traits for: CFG
    922 
    923 template <> struct GraphTraits< ::clang::CFG* >
    924     : public GraphTraits< ::clang::CFGBlock *>  {
    925 
    926   typedef ::clang::CFG::graph_iterator nodes_iterator;
    927 
    928   static NodeType     *getEntryNode(::clang::CFG* F) { return &F->getEntry(); }
    929   static nodes_iterator nodes_begin(::clang::CFG* F) { return F->nodes_begin();}
    930   static nodes_iterator   nodes_end(::clang::CFG* F) { return F->nodes_end(); }
    931   static unsigned              size(::clang::CFG* F) { return F->size(); }
    932 };
    933 
    934 template <> struct GraphTraits<const ::clang::CFG* >
    935     : public GraphTraits<const ::clang::CFGBlock *>  {
    936 
    937   typedef ::clang::CFG::const_graph_iterator nodes_iterator;
    938 
    939   static NodeType *getEntryNode( const ::clang::CFG* F) {
    940     return &F->getEntry();
    941   }
    942   static nodes_iterator nodes_begin( const ::clang::CFG* F) {
    943     return F->nodes_begin();
    944   }
    945   static nodes_iterator nodes_end( const ::clang::CFG* F) {
    946     return F->nodes_end();
    947   }
    948   static unsigned size(const ::clang::CFG* F) {
    949     return F->size();
    950   }
    951 };
    952 
    953 template <> struct GraphTraits<Inverse< ::clang::CFG*> >
    954   : public GraphTraits<Inverse< ::clang::CFGBlock*> > {
    955 
    956   typedef ::clang::CFG::graph_iterator nodes_iterator;
    957 
    958   static NodeType *getEntryNode( ::clang::CFG* F) { return &F->getExit(); }
    959   static nodes_iterator nodes_begin( ::clang::CFG* F) {return F->nodes_begin();}
    960   static nodes_iterator nodes_end( ::clang::CFG* F) { return F->nodes_end(); }
    961 };
    962 
    963 template <> struct GraphTraits<Inverse<const ::clang::CFG*> >
    964   : public GraphTraits<Inverse<const ::clang::CFGBlock*> > {
    965 
    966   typedef ::clang::CFG::const_graph_iterator nodes_iterator;
    967 
    968   static NodeType *getEntryNode(const ::clang::CFG* F) { return &F->getExit(); }
    969   static nodes_iterator nodes_begin(const ::clang::CFG* F) {
    970     return F->nodes_begin();
    971   }
    972   static nodes_iterator nodes_end(const ::clang::CFG* F) {
    973     return F->nodes_end();
    974   }
    975 };
    976 } // end llvm namespace
    977 #endif
    978