v8/src/scopeinfo.h

// Copyright 2011 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       with the distribution.
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#ifndef V8_SCOPEINFO_H_
#define V8_SCOPEINFO_H_

#include "allocation.h"
#include "variables.h"
#include "zone-inl.h"

namespace v8 {
namespace internal {

// ScopeInfo represents information about different scopes of a source
// program  and the allocation of the scope's variables. Scope information
// is stored in a compressed form in SerializedScopeInfo objects and is used
// at runtime (stack dumps, deoptimization, etc.).

// Forward defined as
// template <class Allocator = FreeStoreAllocationPolicy> class ScopeInfo;
template<class Allocator>
class ScopeInfo BASE_EMBEDDED {
 public:
  // Create a ScopeInfo instance from a scope.
  explicit ScopeInfo(Scope* scope);

  // Create a ScopeInfo instance from SerializedScopeInfo.
  explicit ScopeInfo(SerializedScopeInfo* data);

  // Creates a SerializedScopeInfo holding the serialized scope info.
  Handle<SerializedScopeInfo> Serialize();

  // --------------------------------------------------------------------------
  // Lookup

  Handle<String> function_name() const { return function_name_; }

  Handle<String> parameter_name(int i) const { return parameters_[i]; }
  int number_of_parameters() const { return parameters_.length(); }

  Handle<String> stack_slot_name(int i) const { return stack_slots_[i]; }
  int number_of_stack_slots() const { return stack_slots_.length(); }

  Handle<String> context_slot_name(int i) const {
    return context_slots_[i - Context::MIN_CONTEXT_SLOTS];
  }
  int number_of_context_slots() const {
    int l = context_slots_.length();
    return l == 0 ? 0 : l + Context::MIN_CONTEXT_SLOTS;
  }

  Handle<String> LocalName(int i) const;
  int NumberOfLocals() const;

  ScopeType type() const { return type_; }
  // --------------------------------------------------------------------------
  // Debugging support

#ifdef DEBUG
  void Print();
#endif

 private:
  Handle<String> function_name_;
  bool calls_eval_;
  bool is_strict_mode_;
  ScopeType type_;
  List<Handle<String>, Allocator > parameters_;
  List<Handle<String>, Allocator > stack_slots_;
  List<Handle<String>, Allocator > context_slots_;
  List<VariableMode, Allocator > context_modes_;
};


// Cache for mapping (data, property name) into context slot index.
// The cache contains both positive and negative results.
// Slot index equals -1 means the property is absent.
// Cleared at startup and prior to mark sweep collection.
class ContextSlotCache {
 public:
  // Lookup context slot index for (data, name).
  // If absent, kNotFound is returned.
  int Lookup(Object* data,
             String* name,
             VariableMode* mode);

  // Update an element in the cache.
  void Update(Object* data,
              String* name,
              VariableMode mode,
              int slot_index);

  // Clear the cache.
  void Clear();

  static const int kNotFound = -2;

 private:
  ContextSlotCache() {
    for (int i = 0; i < kLength; ++i) {
      keys_[i].data = NULL;
      keys_[i].name = NULL;
      values_[i] = kNotFound;
    }
  }

  inline static int Hash(Object* data, String* name);

#ifdef DEBUG
  void ValidateEntry(Object* data,
                     String* name,
                     VariableMode mode,
                     int slot_index);
#endif

  static const int kLength = 256;
  struct Key {
    Object* data;
    String* name;
  };

  struct Value {
    Value(VariableMode mode, int index) {
      ASSERT(ModeField::is_valid(mode));
      ASSERT(IndexField::is_valid(index));
      value_ = ModeField::encode(mode) | IndexField::encode(index);
      ASSERT(mode == this->mode());
      ASSERT(index == this->index());
    }

    explicit inline Value(uint32_t value) : value_(value) {}

    uint32_t raw() { return value_; }

    VariableMode mode() { return ModeField::decode(value_); }

    int index() { return IndexField::decode(value_); }

    // Bit fields in value_ (type, shift, size). Must be public so the
    // constants can be embedded in generated code.
    class ModeField:  public BitField<VariableMode, 0, 3> {};
    class IndexField: public BitField<int,          3, 32-3> {};
   private:
    uint32_t value_;
  };

  Key keys_[kLength];
  uint32_t values_[kLength];

  friend class Isolate;
  DISALLOW_COPY_AND_ASSIGN(ContextSlotCache);
};


} }  // namespace v8::internal

#endif  // V8_SCOPEINFO_H_