1// Copyright 2006-2008 the V8 project authors. All rights reserved.
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27
28#ifndef V8_SCOPEINFO_H_
29#define V8_SCOPEINFO_H_
30
31#include "variables.h"
32
33namespace v8 {
34namespace internal {
35
36// Scope information represents information about a functions's
37// scopes (currently only one, because we don't do any inlining)
38// and the allocation of the scope's variables. Scope information
39// is stored in a compressed form with Code objects and is used
40// at runtime (stack dumps, deoptimization, etc.).
41//
42// Historical note: In other VMs built by this team, ScopeInfo was
43// usually called DebugInfo since the information was used (among
44// other things) for on-demand debugging (Self, Smalltalk). However,
45// DebugInfo seems misleading, since this information is primarily used
46// in debugging-unrelated contexts.
47
48// Forward defined as
49// template <class Allocator = FreeStoreAllocationPolicy> class ScopeInfo;
50template<class Allocator>
51class ScopeInfo BASE_EMBEDDED {
52 public:
53  // Create a ScopeInfo instance from a scope.
54  explicit ScopeInfo(Scope* scope);
55
56  // Create a ScopeInfo instance from a Code object.
57  explicit ScopeInfo(Code* code);
58
59  // Write the ScopeInfo data into a Code object, and returns the
60  // amount of space that was needed. If no Code object is provided
61  // (NULL handle), Serialize() only returns the amount of space needed.
62  //
63  // This operations requires that the Code object has the correct amount
64  // of space for the ScopeInfo data; otherwise the operation fails (fatal
65  // error). Any existing scope info in the Code object is simply overwritten.
66  int Serialize(Code* code);
67
68  // Garbage collection support for scope info embedded in Code objects.
69  // This code is in ScopeInfo because only here we should have to know
70  // about the encoding.
71  static void IterateScopeInfo(Code* code, ObjectVisitor* v);
72
73
74  // --------------------------------------------------------------------------
75  // Lookup
76
77  Handle<String> function_name() const  { return function_name_; }
78
79  Handle<String> parameter_name(int i) const  { return parameters_[i]; }
80  int number_of_parameters() const  { return parameters_.length(); }
81
82  Handle<String> stack_slot_name(int i) const  { return stack_slots_[i]; }
83  int number_of_stack_slots() const  { return stack_slots_.length(); }
84
85  Handle<String> context_slot_name(int i) const {
86    return context_slots_[i - Context::MIN_CONTEXT_SLOTS];
87  }
88  int number_of_context_slots() const {
89    int l = context_slots_.length();
90    return l == 0 ? 0 : l + Context::MIN_CONTEXT_SLOTS;
91  }
92
93  Handle<String> LocalName(int i) const;
94  int NumberOfLocals() const;
95
96  // --------------------------------------------------------------------------
97  // The following functions provide quick access to scope info details
98  // for runtime routines w/o the need to explicitly create a ScopeInfo
99  // object.
100  //
101  // ScopeInfo is the only class which should have to know about the
102  // encoding of it's information in a Code object, which is why these
103  // functions are in this class.
104
105  // Does this scope call eval.
106  static bool CallsEval(Code* code);
107
108  // Return the number of stack slots for code.
109  static int NumberOfStackSlots(Code* code);
110
111  // Return the number of context slots for code.
112  static int NumberOfContextSlots(Code* code);
113
114  // Lookup support for scope info embedded in Code objects. Returns
115  // the stack slot index for a given slot name if the slot is
116  // present; otherwise returns a value < 0. The name must be a symbol
117  // (canonicalized).
118  static int StackSlotIndex(Code* code, String* name);
119
120  // Lookup support for scope info embedded in Code objects. Returns the
121  // context slot index for a given slot name if the slot is present; otherwise
122  // returns a value < 0. The name must be a symbol (canonicalized).
123  // If the slot is present and mode != NULL, sets *mode to the corresponding
124  // mode for that variable.
125  static int ContextSlotIndex(Code* code, String* name, Variable::Mode* mode);
126
127  // Lookup support for scope info embedded in Code objects. Returns the
128  // parameter index for a given parameter name if the parameter is present;
129  // otherwise returns a value < 0. The name must be a symbol (canonicalized).
130  static int ParameterIndex(Code* code, String* name);
131
132  // Lookup support for scope info embedded in Code objects. Returns the
133  // function context slot index if the function name is present (named
134  // function expressions, only), otherwise returns a value < 0. The name
135  // must be a symbol (canonicalized).
136  static int FunctionContextSlotIndex(Code* code, String* name);
137
138  // --------------------------------------------------------------------------
139  // Debugging support
140
141#ifdef DEBUG
142  void Print();
143#endif
144
145 private:
146  Handle<String> function_name_;
147  bool calls_eval_;
148  List<Handle<String>, Allocator > parameters_;
149  List<Handle<String>, Allocator > stack_slots_;
150  List<Handle<String>, Allocator > context_slots_;
151  List<Variable::Mode, Allocator > context_modes_;
152};
153
154class ZoneScopeInfo: public ScopeInfo<ZoneListAllocationPolicy> {
155 public:
156  // Create a ZoneScopeInfo instance from a scope.
157  explicit ZoneScopeInfo(Scope* scope)
158      : ScopeInfo<ZoneListAllocationPolicy>(scope) {}
159
160  // Create a ZoneScopeInfo instance from a Code object.
161  explicit ZoneScopeInfo(Code* code)
162      :  ScopeInfo<ZoneListAllocationPolicy>(code) {}
163};
164
165
166// Cache for mapping (code, property name) into context slot index.
167// The cache contains both positive and negative results.
168// Slot index equals -1 means the property is absent.
169// Cleared at startup and prior to mark sweep collection.
170class ContextSlotCache {
171 public:
172  // Lookup context slot index for (code, name).
173  // If absent, kNotFound is returned.
174  static int Lookup(Code* code,
175                    String* name,
176                    Variable::Mode* mode);
177
178  // Update an element in the cache.
179  static void Update(Code* code,
180                     String* name,
181                     Variable::Mode mode,
182                     int slot_index);
183
184  // Clear the cache.
185  static void Clear();
186
187  static const int kNotFound = -2;
188 private:
189  inline static int Hash(Code* code, String* name);
190
191#ifdef DEBUG
192  static void ValidateEntry(Code* code,
193                            String* name,
194                            Variable::Mode mode,
195                            int slot_index);
196#endif
197
198  static const int kLength = 256;
199  struct Key {
200    Code* code;
201    String* name;
202  };
203
204  struct Value {
205    Value(Variable::Mode mode, int index) {
206      ASSERT(ModeField::is_valid(mode));
207      ASSERT(IndexField::is_valid(index));
208      value_ = ModeField::encode(mode) | IndexField::encode(index);
209      ASSERT(mode == this->mode());
210      ASSERT(index == this->index());
211    }
212
213    inline Value(uint32_t value) : value_(value) {}
214
215    uint32_t raw() { return value_; }
216
217    Variable::Mode mode() { return ModeField::decode(value_); }
218
219    int index() { return IndexField::decode(value_); }
220
221    // Bit fields in value_ (type, shift, size). Must be public so the
222    // constants can be embedded in generated code.
223    class ModeField:  public BitField<Variable::Mode, 0, 3> {};
224    class IndexField: public BitField<int,            3, 32-3> {};
225   private:
226    uint32_t value_;
227  };
228
229  static Key keys_[kLength];
230  static uint32_t values_[kLength];
231};
232
233
234} }  // namespace v8::internal
235
236#endif  // V8_SCOPEINFO_H_
237