// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_HYDROGEN_UNIQUE_H_
#define V8_HYDROGEN_UNIQUE_H_
#include "src/handles-inl.h" // TODO(everyone): Fix our inl.h crap
#include "src/objects-inl.h" // TODO(everyone): Fix our inl.h crap
#include "src/string-stream.h"
#include "src/utils.h"
#include "src/zone.h"
namespace v8 {
namespace internal {
template <typename T>
class UniqueSet;
// Represents a handle to an object on the heap, but with the additional
// ability of checking for equality and hashing without accessing the heap.
//
// Creating a Unique<T> requires first dereferencing the handle to obtain
// the address of the object, which is used as the hashcode and the basis for
// comparison. The object can be moved later by the GC, but comparison
// and hashing use the old address of the object, without dereferencing it.
//
// Careful! Comparison of two Uniques is only correct if both were created
// in the same "era" of GC or if at least one is a non-movable object.
template <typename T>
class Unique {
public:
Unique<T>() : raw_address_(NULL) {}
// TODO(titzer): make private and introduce a uniqueness scope.
explicit Unique(Handle<T> handle) {
if (handle.is_null()) {
raw_address_ = NULL;
} else {
// This is a best-effort check to prevent comparing Unique<T>'s created
// in different GC eras; we require heap allocation to be disallowed at
// creation time.
// NOTE: we currently consider maps to be non-movable, so no special
// assurance is required for creating a Unique<Map>.
// TODO(titzer): other immortable immovable objects are also fine.
DCHECK(!AllowHeapAllocation::IsAllowed() || handle->IsMap());
raw_address_ = reinterpret_cast<Address>(*handle);
DCHECK_NE(raw_address_, NULL); // Non-null should imply non-zero address.
}
handle_ = handle;
}
// TODO(titzer): this is a hack to migrate to Unique<T> incrementally.
Unique(Address raw_address, Handle<T> handle)
: raw_address_(raw_address), handle_(handle) { }
// Constructor for handling automatic up casting.
// Eg. Unique<JSFunction> can be passed when Unique<Object> is expected.
template <class S> Unique(Unique<S> uniq) {
#ifdef DEBUG
T* a = NULL;
S* b = NULL;
a = b; // Fake assignment to enforce type checks.
USE(a);
#endif
raw_address_ = uniq.raw_address_;
handle_ = uniq.handle_;
}
template <typename U>
inline bool operator==(const Unique<U>& other) const {
DCHECK(IsInitialized() && other.IsInitialized());
return raw_address_ == other.raw_address_;
}
template <typename U>
inline bool operator!=(const Unique<U>& other) const {
DCHECK(IsInitialized() && other.IsInitialized());
return raw_address_ != other.raw_address_;
}
inline intptr_t Hashcode() const {
DCHECK(IsInitialized());
return reinterpret_cast<intptr_t>(raw_address_);
}
inline bool IsNull() const {
DCHECK(IsInitialized());
return raw_address_ == NULL;
}
inline bool IsKnownGlobal(void* global) const {
DCHECK(IsInitialized());
return raw_address_ == reinterpret_cast<Address>(global);
}
inline Handle<T> handle() const {
return handle_;
}
template <class S> static Unique<T> cast(Unique<S> that) {
return Unique<T>(that.raw_address_, Handle<T>::cast(that.handle_));
}
inline bool IsInitialized() const {
return raw_address_ != NULL || handle_.is_null();
}
// TODO(titzer): this is a hack to migrate to Unique<T> incrementally.
static Unique<T> CreateUninitialized(Handle<T> handle) {
return Unique<T>(reinterpret_cast<Address>(NULL), handle);
}
static Unique<T> CreateImmovable(Handle<T> handle) {
return Unique<T>(reinterpret_cast<Address>(*handle), handle);
}
friend class UniqueSet<T>; // Uses internal details for speed.
template <class U>
friend class Unique; // For comparing raw_address values.
protected:
Address raw_address_;
Handle<T> handle_;
friend class SideEffectsTracker;
};
template <typename T>
class UniqueSet FINAL : public ZoneObject {
public:
// Constructor. A new set will be empty.
UniqueSet() : size_(0), capacity_(0), array_(NULL) { }
// Capacity constructor. A new set will be empty.
UniqueSet(int capacity, Zone* zone)
: size_(0), capacity_(capacity),
array_(zone->NewArray<Unique<T> >(capacity)) {
DCHECK(capacity <= kMaxCapacity);
}
// Singleton constructor.
UniqueSet(Unique<T> uniq, Zone* zone)
: size_(1), capacity_(1), array_(zone->NewArray<Unique<T> >(1)) {
array_[0] = uniq;
}
// Add a new element to this unique set. Mutates this set. O(|this|).
void Add(Unique<T> uniq, Zone* zone) {
DCHECK(uniq.IsInitialized());
// Keep the set sorted by the {raw_address} of the unique elements.
for (int i = 0; i < size_; i++) {
if (array_[i] == uniq) return;
if (array_[i].raw_address_ > uniq.raw_address_) {
// Insert in the middle.
Grow(size_ + 1, zone);
for (int j = size_ - 1; j >= i; j--) array_[j + 1] = array_[j];
array_[i] = uniq;
size_++;
return;
}
}
// Append the element to the the end.
Grow(size_ + 1, zone);
array_[size_++] = uniq;
}
// Remove an element from this set. Mutates this set. O(|this|)
void Remove(Unique<T> uniq) {
for (int i = 0; i < size_; i++) {
if (array_[i] == uniq) {
while (++i < size_) array_[i - 1] = array_[i];
size_--;
return;
}
}
}
// Compare this set against another set. O(|this|).
bool Equals(const UniqueSet<T>* that) const {
if (that->size_ != this->size_) return false;
for (int i = 0; i < this->size_; i++) {
if (this->array_[i] != that->array_[i]) return false;
}
return true;
}
// Check whether this set contains the given element. O(|this|)
// TODO(titzer): use binary search for large sets to make this O(log|this|)
template <typename U>
bool Contains(const Unique<U> elem) const {
for (int i = 0; i < this->size_; ++i) {
Unique<T> cand = this->array_[i];
if (cand.raw_address_ >= elem.raw_address_) {
return cand.raw_address_ == elem.raw_address_;
}
}
return false;
}
// Check if this set is a subset of the given set. O(|this| + |that|).
bool IsSubset(const UniqueSet<T>* that) const {
if (that->size_ < this->size_) return false;
int j = 0;
for (int i = 0; i < this->size_; i++) {
Unique<T> sought = this->array_[i];
while (true) {
if (sought == that->array_[j++]) break;
// Fail whenever there are more elements in {this} than {that}.
if ((this->size_ - i) > (that->size_ - j)) return false;
}
}
return true;
}
// Returns a new set representing the intersection of this set and the other.
// O(|this| + |that|).
UniqueSet<T>* Intersect(const UniqueSet<T>* that, Zone* zone) const {
if (that->size_ == 0 || this->size_ == 0) return new(zone) UniqueSet<T>();
UniqueSet<T>* out = new(zone) UniqueSet<T>(
Min(this->size_, that->size_), zone);
int i = 0, j = 0, k = 0;
while (i < this->size_ && j < that->size_) {
Unique<T> a = this->array_[i];
Unique<T> b = that->array_[j];
if (a == b) {
out->array_[k++] = a;
i++;
j++;
} else if (a.raw_address_ < b.raw_address_) {
i++;
} else {
j++;
}
}
out->size_ = k;
return out;
}
// Returns a new set representing the union of this set and the other.
// O(|this| + |that|).
UniqueSet<T>* Union(const UniqueSet<T>* that, Zone* zone) const {
if (that->size_ == 0) return this->Copy(zone);
if (this->size_ == 0) return that->Copy(zone);
UniqueSet<T>* out = new(zone) UniqueSet<T>(
this->size_ + that->size_, zone);
int i = 0, j = 0, k = 0;
while (i < this->size_ && j < that->size_) {
Unique<T> a = this->array_[i];
Unique<T> b = that->array_[j];
if (a == b) {
out->array_[k++] = a;
i++;
j++;
} else if (a.raw_address_ < b.raw_address_) {
out->array_[k++] = a;
i++;
} else {
out->array_[k++] = b;
j++;
}
}
while (i < this->size_) out->array_[k++] = this->array_[i++];
while (j < that->size_) out->array_[k++] = that->array_[j++];
out->size_ = k;
return out;
}
// Returns a new set representing all elements from this set which are not in
// that set. O(|this| * |that|).
UniqueSet<T>* Subtract(const UniqueSet<T>* that, Zone* zone) const {
if (that->size_ == 0) return this->Copy(zone);
UniqueSet<T>* out = new(zone) UniqueSet<T>(this->size_, zone);
int i = 0, j = 0;
while (i < this->size_) {
Unique<T> cand = this->array_[i];
if (!that->Contains(cand)) {
out->array_[j++] = cand;
}
i++;
}
out->size_ = j;
return out;
}
// Makes an exact copy of this set. O(|this|).
UniqueSet<T>* Copy(Zone* zone) const {
UniqueSet<T>* copy = new(zone) UniqueSet<T>(this->size_, zone);
copy->size_ = this->size_;
memcpy(copy->array_, this->array_, this->size_ * sizeof(Unique<T>));
return copy;
}
void Clear() {
size_ = 0;
}
inline int size() const {
return size_;
}
inline Unique<T> at(int index) const {
DCHECK(index >= 0 && index < size_);
return array_[index];
}
private:
// These sets should be small, since operations are implemented with simple
// linear algorithms. Enforce a maximum size.
static const int kMaxCapacity = 65535;
uint16_t size_;
uint16_t capacity_;
Unique<T>* array_;
// Grow the size of internal storage to be at least {size} elements.
void Grow(int size, Zone* zone) {
CHECK(size < kMaxCapacity); // Enforce maximum size.
if (capacity_ < size) {
int new_capacity = 2 * capacity_ + size;
if (new_capacity > kMaxCapacity) new_capacity = kMaxCapacity;
Unique<T>* new_array = zone->NewArray<Unique<T> >(new_capacity);
if (size_ > 0) {
memcpy(new_array, array_, size_ * sizeof(Unique<T>));
}
capacity_ = new_capacity;
array_ = new_array;
}
}
};
} } // namespace v8::internal
#endif // V8_HYDROGEN_UNIQUE_H_