zone.h 7.81 KB
Newer Older
1
// Copyright 2011 the V8 project authors. All rights reserved.
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_ZONE_H_
#define V8_ZONE_H_

31 32
namespace v8 {
namespace internal {
33 34


35 36 37 38 39 40 41 42
// Zone scopes are in one of two modes.  Either they delete the zone
// on exit or they do not.
enum ZoneScopeMode {
  DELETE_ON_EXIT,
  DONT_DELETE_ON_EXIT
};


43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
// The Zone supports very fast allocation of small chunks of
// memory. The chunks cannot be deallocated individually, but instead
// the Zone supports deallocating all chunks in one fast
// operation. The Zone is used to hold temporary data structures like
// the abstract syntax tree, which is deallocated after compilation.

// Note: There is no need to initialize the Zone; the first time an
// allocation is attempted, a segment of memory will be requested
// through a call to malloc().

// Note: The implementation is inherently not thread safe. Do not use
// from multi-threaded code.

class Zone {
 public:
  // Allocate 'size' bytes of memory in the Zone; expands the Zone by
  // allocating new segments of memory on demand using malloc().
  static inline void* New(int size);

62 63 64
  template <typename T>
  static inline T* NewArray(int length);

65 66 67
  // Delete all objects and free all memory allocated in the Zone.
  static void DeleteAll();

68 69 70 71
  // Returns true if more memory has been allocated in zones than
  // the limit allows.
  static inline bool excess_allocation();

72 73
  static inline void adjust_segment_bytes_allocated(int delta);

74 75
  static unsigned allocation_size_;

76
 private:
77

78 79 80 81 82
  // All pointers returned from New() have this alignment.
  static const int kAlignment = kPointerSize;

  // Never allocate segments smaller than this size in bytes.
  static const int kMinimumSegmentSize = 8 * KB;
iposva@chromium.org's avatar
iposva@chromium.org committed
83

84 85
  // Never allocate segments larger than this size in bytes.
  static const int kMaximumSegmentSize = 1 * MB;
86 87 88 89

  // Never keep segments larger than this size in bytes around.
  static const int kMaximumKeptSegmentSize = 64 * KB;

90 91 92 93 94 95 96
  // Report zone excess when allocation exceeds this limit.
  static int zone_excess_limit_;

  // The number of bytes allocated in segments.  Note that this number
  // includes memory allocated from the OS but not yet allocated from
  // the zone.
  static int segment_bytes_allocated_;
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122

  // The Zone is intentionally a singleton; you should not try to
  // allocate instances of the class.
  Zone() { UNREACHABLE(); }


  // Expand the Zone to hold at least 'size' more bytes and allocate
  // the bytes. Returns the address of the newly allocated chunk of
  // memory in the Zone. Should only be called if there isn't enough
  // room in the Zone already.
  static Address NewExpand(int size);


  // The free region in the current (front) segment is represented as
  // the half-open interval [position, limit). The 'position' variable
  // is guaranteed to be aligned as dictated by kAlignment.
  static Address position_;
  static Address limit_;
};


// ZoneObject is an abstraction that helps define classes of objects
// allocated in the Zone. Use it as a base class; see ast.h.
class ZoneObject {
 public:
  // Allocate a new ZoneObject of 'size' bytes in the Zone.
123
  void* operator new(size_t size) { return Zone::New(static_cast<int>(size)); }
124 125

  // Ideally, the delete operator should be private instead of
126
  // public, but unfortunately the compiler sometimes synthesizes
127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173
  // (unused) destructors for classes derived from ZoneObject, which
  // require the operator to be visible. MSVC requires the delete
  // operator to be public.

  // ZoneObjects should never be deleted individually; use
  // Zone::DeleteAll() to delete all zone objects in one go.
  void operator delete(void*, size_t) { UNREACHABLE(); }
};


class AssertNoZoneAllocation {
 public:
  AssertNoZoneAllocation() : prev_(allow_allocation_) {
    allow_allocation_ = false;
  }
  ~AssertNoZoneAllocation() { allow_allocation_ = prev_; }
  static bool allow_allocation() { return allow_allocation_; }
 private:
  bool prev_;
  static bool allow_allocation_;
};


// The ZoneListAllocationPolicy is used to specialize the GenericList
// implementation to allocate ZoneLists and their elements in the
// Zone.
class ZoneListAllocationPolicy {
 public:
  // Allocate 'size' bytes of memory in the zone.
  static void* New(int size) {  return Zone::New(size); }

  // De-allocation attempts are silently ignored.
  static void Delete(void* p) { }
};


// ZoneLists are growable lists with constant-time access to the
// elements. The list itself and all its elements are allocated in the
// Zone. ZoneLists cannot be deleted individually; you can delete all
// objects in the Zone by calling Zone::DeleteAll().
template<typename T>
class ZoneList: public List<T, ZoneListAllocationPolicy> {
 public:
  // Construct a new ZoneList with the given capacity; the length is
  // always zero. The capacity must be non-negative.
  explicit ZoneList(int capacity)
      : List<T, ZoneListAllocationPolicy>(capacity) { }
174 175 176 177 178 179

  // Construct a new ZoneList by copying the elements of the given ZoneList.
  explicit ZoneList(const ZoneList<T>& other)
      : List<T, ZoneListAllocationPolicy>(other.length()) {
    AddAll(other);
  }
180 181 182
};


183 184 185 186
// Introduce a convenience type for zone lists of map handles.
typedef ZoneList<Handle<Map> > ZoneMapList;


187 188 189 190 191 192 193 194 195
// ZoneScopes keep track of the current parsing and compilation
// nesting and cleans up generated ASTs in the Zone when exiting the
// outer-most scope.
class ZoneScope BASE_EMBEDDED {
 public:
  explicit ZoneScope(ZoneScopeMode mode) : mode_(mode) {
    nesting_++;
  }

196 197 198 199 200 201 202
  virtual ~ZoneScope() {
    if (ShouldDeleteOnExit()) Zone::DeleteAll();
    --nesting_;
  }

  bool ShouldDeleteOnExit() {
    return nesting_ == 1 && mode_ == DELETE_ON_EXIT;
203 204 205 206 207 208 209 210
  }

  // For ZoneScopes that do not delete on exit by default, call this
  // method to request deletion on exit.
  void DeleteOnExit() {
    mode_ = DELETE_ON_EXIT;
  }

211 212
  static int nesting() { return nesting_; }

213 214 215 216 217 218
 private:
  ZoneScopeMode mode_;
  static int nesting_;
};


219
// A zone splay tree.  The config type parameter encapsulates the
220 221
// different configurations of a concrete splay tree (see splay-tree.h).
// The tree itself and all its elements are allocated in the Zone.
222
template <typename Config>
223
class ZoneSplayTree: public SplayTree<Config, ZoneListAllocationPolicy> {
224
 public:
225 226 227
  ZoneSplayTree()
      : SplayTree<Config, ZoneListAllocationPolicy>() {}
  ~ZoneSplayTree();
228 229 230
};


231 232 233
} }  // namespace v8::internal

#endif  // V8_ZONE_H_