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// Copyright 2012 the V8 project authors. All rights reserved.
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#ifndef V8_ZONE_H_
#define V8_ZONE_H_
#include "allocation.h"
#include "checks.h"
#include "hashmap.h"
#include "globals.h"
#include "list.h"
#include "splay-tree.h"
namespace v8 {
namespace internal {
// 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
};
class Segment;
class Isolate;
// 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:
explicit Zone(Isolate* isolate);
~Zone() { DeleteKeptSegment(); }
// Allocate 'size' bytes of memory in the Zone; expands the Zone by
// allocating new segments of memory on demand using malloc().
inline void* New(int size);
template <typename T>
inline T* NewArray(int length);
// Deletes all objects and free all memory allocated in the Zone. Keeps one
// small (size <= kMaximumKeptSegmentSize) segment around if it finds one.
void DeleteAll();
// Deletes the last small segment kept around by DeleteAll().
void DeleteKeptSegment();
// Returns true if more memory has been allocated in zones than
// the limit allows.
inline bool excess_allocation();
inline void adjust_segment_bytes_allocated(int delta);
inline Isolate* isolate() { return isolate_; }
static unsigned allocation_size_;
private:
friend class Isolate;
friend class ZoneScope;
// All pointers returned from New() have this alignment. In addition, if the
// object being allocated has a size that is divisible by 8 then its alignment
// will be 8.
static const int kAlignment = kPointerSize;
// Never allocate segments smaller than this size in bytes.
static const int kMinimumSegmentSize = 8 * KB;
// Never allocate segments larger than this size in bytes.
static const int kMaximumSegmentSize = 1 * MB;
// Never keep segments larger than this size in bytes around.
static const int kMaximumKeptSegmentSize = 64 * KB;
// Report zone excess when allocation exceeds this limit.
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.
int segment_bytes_allocated_;
// 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.
Address NewExpand(int size);
// Creates a new segment, sets it size, and pushes it to the front
// of the segment chain. Returns the new segment.
Segment* NewSegment(int size);
// Deletes the given segment. Does not touch the segment chain.
void DeleteSegment(Segment* segment, 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.
Address position_;
Address limit_;
int scope_nesting_;
Segment* segment_head_;
Isolate* isolate_;
};
// 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.
INLINE(void* operator new(size_t size, Zone* zone));
// Ideally, the delete operator should be private instead of
// public, but unfortunately the compiler sometimes synthesizes
// (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(); }
void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
};
// The ZoneAllocationPolicy is used to specialize generic data
// structures to allocate themselves and their elements in the Zone.
struct ZoneAllocationPolicy {
public:
explicit ZoneAllocationPolicy(Zone* zone) : zone_(zone) { }
INLINE(void* New(size_t size));
INLINE(static void Delete(void *pointer)) { }
private:
Zone* zone_;
};
// 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, ZoneAllocationPolicy> {
public:
// Construct a new ZoneList with the given capacity; the length is
// always zero. The capacity must be non-negative.
ZoneList(int capacity, Zone* zone)
: List<T, ZoneAllocationPolicy>(capacity, ZoneAllocationPolicy(zone)) { }
INLINE(void* operator new(size_t size, Zone* zone));
// Construct a new ZoneList by copying the elements of the given ZoneList.
ZoneList(const ZoneList<T>& other, Zone* zone)
: List<T, ZoneAllocationPolicy>(other.length(),
ZoneAllocationPolicy(zone)) {
AddAll(other, ZoneAllocationPolicy(zone));
}
// We add some convenience wrappers so that we can pass in a Zone
// instead of a (less convenient) ZoneAllocationPolicy.
INLINE(void Add(const T& element, Zone* zone)) {
List<T, ZoneAllocationPolicy>::Add(element, ZoneAllocationPolicy(zone));
}
INLINE(void AddAll(const List<T, ZoneAllocationPolicy>& other,
Zone* zone)) {
List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone));
}
INLINE(void AddAll(const Vector<T>& other, Zone* zone)) {
List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone));
}
INLINE(void InsertAt(int index, const T& element, Zone* zone)) {
List<T, ZoneAllocationPolicy>::InsertAt(index, element,
ZoneAllocationPolicy(zone));
}
INLINE(Vector<T> AddBlock(T value, int count, Zone* zone)) {
return List<T, ZoneAllocationPolicy>::AddBlock(value, count,
ZoneAllocationPolicy(zone));
}
INLINE(void Allocate(int length, Zone* zone)) {
List<T, ZoneAllocationPolicy>::Allocate(length, ZoneAllocationPolicy(zone));
}
INLINE(void Initialize(int capacity, Zone* zone)) {
List<T, ZoneAllocationPolicy>::Initialize(capacity,
ZoneAllocationPolicy(zone));
}
void operator delete(void* pointer) { UNREACHABLE(); }
void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
};
// 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:
INLINE(ZoneScope(Zone* zone, ZoneScopeMode mode));
virtual ~ZoneScope();
inline bool ShouldDeleteOnExit();
// For ZoneScopes that do not delete on exit by default, call this
// method to request deletion on exit.
void DeleteOnExit() {
mode_ = DELETE_ON_EXIT;
}
inline static int nesting();
private:
Zone* zone_;
ZoneScopeMode mode_;
};
// A zone splay tree. The config type parameter encapsulates the
// different configurations of a concrete splay tree (see splay-tree.h).
// The tree itself and all its elements are allocated in the Zone.
template <typename Config>
class ZoneSplayTree: public SplayTree<Config, ZoneAllocationPolicy> {
public:
explicit ZoneSplayTree(Zone* zone)
: SplayTree<Config, ZoneAllocationPolicy>(ZoneAllocationPolicy(zone)) {}
~ZoneSplayTree();
};
typedef TemplateHashMapImpl<ZoneAllocationPolicy> ZoneHashMap;
} } // namespace v8::internal
#endif // V8_ZONE_H_