1.1 --- a/jitcraft/SemanticAnalysis.h	Thu Jul 12 00:38:00 2012 -0700
     1.2 +++ b/jitcraft/SemanticAnalysis.h	Sat Jul 14 18:43:34 2012 -0700
     1.3 @@ -29,10 +29,123 @@
     1.4      Zone *zone_;
     1.5      CompileContext &cc_;
     1.6      ParseTree *tree_;
     1.7 -    unsigned loopDepth_;
     1.8      Scope *scope_;
     1.9      ScopedRoot<Type> function_;
    1.10  
    1.11 +    enum ReturnStatus
    1.12 +    {
    1.13 +        Returns_Never,
    1.14 +        Returns_Sometimes,
    1.15 +        Returns_Always
    1.16 +    };
    1.17 +
    1.18 +    // Tuple that describes whether a path terminates control flow, and
    1.19 +    // if it is guaranteed to end in a return.
    1.20 +    class ControlStatus
    1.21 +    {
    1.22 +        bool terminates_;
    1.23 +        ReturnStatus returns_;
    1.24 +
    1.25 +      public:
    1.26 +        ControlStatus(bool terminates, ReturnStatus returns)
    1.27 +          : terminates_(terminates),
    1.28 +            returns_(returns)
    1.29 +        {
    1.30 +        }
    1.31 +
    1.32 +        bool terminates() const {
    1.33 +            return terminates_;
    1.34 +        }
    1.35 +        ReturnStatus returns() const {
    1.36 +            return returns_;
    1.37 +        }
    1.38 +    };
    1.39 +
    1.40 +    // Used to keep track of terminating control flow and return statements
    1.41 +    // inside control structures.
    1.42 +    class ControlScope
    1.43 +    {
    1.44 +        ReturnStatus returns_;
    1.45 +        ControlScope **prevp_;
    1.46 +        ControlScope *prev_;
    1.47 +        bool terminates_;
    1.48 +
    1.49 +      public:
    1.50 +        ControlScope(ControlScope **prev)
    1.51 +          : returns_(Returns_Never),
    1.52 +            prevp_(prev),
    1.53 +            prev_(*prev),
    1.54 +            terminates_(false)
    1.55 +        {
    1.56 +            *prevp_ = this;
    1.57 +        }
    1.58 +
    1.59 +        ControlStatus status() const {
    1.60 +            return ControlStatus(terminates_, returns_);
    1.61 +        }
    1.62 +
    1.63 +        // We allow multiple terminators, but only the first one takes effect.
    1.64 +        // For example, |break; continue;| is legal but the continue is
    1.65 +        // unreachable.
    1.66 +        void returns(ReturnStatus status) {
    1.67 +            if (terminates_)
    1.68 +                return;
    1.69 +            if (status > returns_)
    1.70 +                returns_ = status;
    1.71 +        }
    1.72 +        void terminate(ReturnStatus status) {
    1.73 +            if (terminates_)
    1.74 +                return;
    1.75 +            terminates_ = true;
    1.76 +            returns_ = status;
    1.77 +        }
    1.78 +        void merge(const ControlStatus &left, const ControlStatus &right);
    1.79 +
    1.80 +        ~ControlScope()
    1.81 +        {
    1.82 +            *prevp_ = prev_;
    1.83 +        }
    1.84 +    };
    1.85 +
    1.86 +    class LoopScope
    1.87 +    {
    1.88 +        LoopScope **prevp_;
    1.89 +        LoopScope *prev_;
    1.90 +        unsigned breaks_;
    1.91 +        unsigned continues_;
    1.92 +
    1.93 +      public:
    1.94 +        LoopScope(LoopScope **prev)
    1.95 +          : prevp_(prev),
    1.96 +            prev_(*prev),
    1.97 +            breaks_(0),
    1.98 +            continues_(0)
    1.99 +        {
   1.100 +            *prevp_ = this;
   1.101 +        }
   1.102 +
   1.103 +        ~LoopScope()
   1.104 +        {
   1.105 +            *prevp_ = prev_;
   1.106 +        }
   1.107 +
   1.108 +        void addBreak() {
   1.109 +            breaks_++;
   1.110 +        }
   1.111 +        void addContinue() {
   1.112 +            continues_++;
   1.113 +        }
   1.114 +        unsigned breaks() const {
   1.115 +            return breaks_;
   1.116 +        }
   1.117 +        unsigned continues() const {
   1.118 +            return continues_;
   1.119 +        }
   1.120 +    };
   1.121 +
   1.122 +    ControlScope *control_;
   1.123 +    LoopScope *loop_;
   1.124 +
   1.125    private:
   1.126      bool canTest(AstNode *node, Handle<Type> type);
   1.127      void unaryTypeError(AstNode *node, TokenKind token, Handle<Type> type);
   1.128 @@ -47,14 +160,15 @@
   1.129      //
   1.130      bool typeCheckArrayAssignment(AstNode *node, Handle<Type> given, Handle<Type> actual, bool forAssign);
   1.131      bool typeCheckAssignment(AstNode *node, Handle<Type> given, Handle<Type> actual, bool forAssign);
   1.132 -
   1.133      bool typeCheckParameter(AstNode *node, Handle<Type> given, Handle<Type> actual);
   1.134  
   1.135      Type *visitForLoad(Expression *expression);
   1.136 -    Type *visitForRef(Expression *expression);
   1.137      bool preanalyze(FunctionStatement *node);
   1.138      Type *visitForLValue(Expression *expression);
   1.139      Type *visitAndApplyType(Expression *expression);
   1.140 +    ControlStatus visitForControl(Statement *statement);
   1.141 +
   1.142 +    void markCallResultUsed(CallExpression *call);
   1.143  
   1.144    public:
   1.145      SemanticAnalysis(Zone *zone, CompileContext &cc, ParseTree *tree);