Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_CRANKSHAFT_UNIQUE_H_ |
| 6 | #define V8_CRANKSHAFT_UNIQUE_H_ |
| 7 | |
| 8 | #include <ostream> // NOLINT(readability/streams) |
| 9 | |
| 10 | #include "src/assert-scope.h" |
| 11 | #include "src/base/functional.h" |
| 12 | #include "src/handles.h" |
| 13 | #include "src/utils.h" |
| 14 | #include "src/zone.h" |
| 15 | |
| 16 | namespace v8 { |
| 17 | namespace internal { |
| 18 | |
| 19 | |
| 20 | template <typename T> |
| 21 | class UniqueSet; |
| 22 | |
| 23 | |
| 24 | // Represents a handle to an object on the heap, but with the additional |
| 25 | // ability of checking for equality and hashing without accessing the heap. |
| 26 | // |
| 27 | // Creating a Unique<T> requires first dereferencing the handle to obtain |
| 28 | // the address of the object, which is used as the hashcode and the basis for |
| 29 | // comparison. The object can be moved later by the GC, but comparison |
| 30 | // and hashing use the old address of the object, without dereferencing it. |
| 31 | // |
| 32 | // Careful! Comparison of two Uniques is only correct if both were created |
| 33 | // in the same "era" of GC or if at least one is a non-movable object. |
| 34 | template <typename T> |
| 35 | class Unique final { |
| 36 | public: |
| 37 | Unique<T>() : raw_address_(NULL) {} |
| 38 | |
| 39 | // TODO(titzer): make private and introduce a uniqueness scope. |
| 40 | explicit Unique(Handle<T> handle) { |
| 41 | if (handle.is_null()) { |
| 42 | raw_address_ = NULL; |
| 43 | } else { |
| 44 | // This is a best-effort check to prevent comparing Unique<T>'s created |
| 45 | // in different GC eras; we require heap allocation to be disallowed at |
| 46 | // creation time. |
| 47 | // NOTE: we currently consider maps to be non-movable, so no special |
| 48 | // assurance is required for creating a Unique<Map>. |
| 49 | // TODO(titzer): other immortable immovable objects are also fine. |
| 50 | DCHECK(!AllowHeapAllocation::IsAllowed() || handle->IsMap()); |
| 51 | raw_address_ = reinterpret_cast<Address>(*handle); |
| 52 | DCHECK_NOT_NULL(raw_address_); // Non-null should imply non-zero address. |
| 53 | } |
| 54 | handle_ = handle; |
| 55 | } |
| 56 | |
| 57 | // Constructor for handling automatic up casting. |
| 58 | // Eg. Unique<JSFunction> can be passed when Unique<Object> is expected. |
| 59 | template <class S> Unique(Unique<S> uniq) { |
| 60 | #ifdef DEBUG |
| 61 | T* a = NULL; |
| 62 | S* b = NULL; |
| 63 | a = b; // Fake assignment to enforce type checks. |
| 64 | USE(a); |
| 65 | #endif |
| 66 | raw_address_ = uniq.raw_address_; |
| 67 | handle_ = uniq.handle_; |
| 68 | } |
| 69 | |
| 70 | template <typename U> |
| 71 | inline bool operator==(const Unique<U>& other) const { |
| 72 | DCHECK(IsInitialized() && other.IsInitialized()); |
| 73 | return raw_address_ == other.raw_address_; |
| 74 | } |
| 75 | |
| 76 | template <typename U> |
| 77 | inline bool operator!=(const Unique<U>& other) const { |
| 78 | DCHECK(IsInitialized() && other.IsInitialized()); |
| 79 | return raw_address_ != other.raw_address_; |
| 80 | } |
| 81 | |
| 82 | friend inline size_t hash_value(Unique<T> const& unique) { |
| 83 | DCHECK(unique.IsInitialized()); |
| 84 | return base::hash<void*>()(unique.raw_address_); |
| 85 | } |
| 86 | |
| 87 | inline intptr_t Hashcode() const { |
| 88 | DCHECK(IsInitialized()); |
| 89 | return reinterpret_cast<intptr_t>(raw_address_); |
| 90 | } |
| 91 | |
| 92 | inline bool IsNull() const { |
| 93 | DCHECK(IsInitialized()); |
| 94 | return raw_address_ == NULL; |
| 95 | } |
| 96 | |
| 97 | inline bool IsKnownGlobal(void* global) const { |
| 98 | DCHECK(IsInitialized()); |
| 99 | return raw_address_ == reinterpret_cast<Address>(global); |
| 100 | } |
| 101 | |
| 102 | inline Handle<T> handle() const { |
| 103 | return handle_; |
| 104 | } |
| 105 | |
| 106 | template <class S> static Unique<T> cast(Unique<S> that) { |
| 107 | // Allow fetching location() to unsafe-cast the handle. This is necessary |
| 108 | // since we can't concurrently safe-cast. Safe-casting requires looking at |
| 109 | // the heap which may be moving concurrently to the compiler thread. |
| 110 | AllowHandleDereference allow_deref; |
| 111 | return Unique<T>(that.raw_address_, |
| 112 | Handle<T>(reinterpret_cast<T**>(that.handle_.location()))); |
| 113 | } |
| 114 | |
| 115 | inline bool IsInitialized() const { |
| 116 | return raw_address_ != NULL || handle_.is_null(); |
| 117 | } |
| 118 | |
| 119 | // TODO(titzer): this is a hack to migrate to Unique<T> incrementally. |
| 120 | static Unique<T> CreateUninitialized(Handle<T> handle) { |
| 121 | return Unique<T>(NULL, handle); |
| 122 | } |
| 123 | |
| 124 | static Unique<T> CreateImmovable(Handle<T> handle) { |
| 125 | return Unique<T>(reinterpret_cast<Address>(*handle), handle); |
| 126 | } |
| 127 | |
| 128 | private: |
| 129 | Unique(Address raw_address, Handle<T> handle) |
| 130 | : raw_address_(raw_address), handle_(handle) {} |
| 131 | |
| 132 | Address raw_address_; |
| 133 | Handle<T> handle_; |
| 134 | |
| 135 | friend class UniqueSet<T>; // Uses internal details for speed. |
| 136 | template <class U> |
| 137 | friend class Unique; // For comparing raw_address values. |
| 138 | }; |
| 139 | |
| 140 | template <typename T> |
| 141 | inline std::ostream& operator<<(std::ostream& os, Unique<T> uniq) { |
| 142 | return os << Brief(*uniq.handle()); |
| 143 | } |
| 144 | |
| 145 | |
| 146 | template <typename T> |
| 147 | class UniqueSet final : public ZoneObject { |
| 148 | public: |
| 149 | // Constructor. A new set will be empty. |
| 150 | UniqueSet() : size_(0), capacity_(0), array_(NULL) { } |
| 151 | |
| 152 | // Capacity constructor. A new set will be empty. |
| 153 | UniqueSet(int capacity, Zone* zone) |
| 154 | : size_(0), capacity_(capacity), |
| 155 | array_(zone->NewArray<Unique<T> >(capacity)) { |
| 156 | DCHECK(capacity <= kMaxCapacity); |
| 157 | } |
| 158 | |
| 159 | // Singleton constructor. |
| 160 | UniqueSet(Unique<T> uniq, Zone* zone) |
| 161 | : size_(1), capacity_(1), array_(zone->NewArray<Unique<T> >(1)) { |
| 162 | array_[0] = uniq; |
| 163 | } |
| 164 | |
| 165 | // Add a new element to this unique set. Mutates this set. O(|this|). |
| 166 | void Add(Unique<T> uniq, Zone* zone) { |
| 167 | DCHECK(uniq.IsInitialized()); |
| 168 | // Keep the set sorted by the {raw_address} of the unique elements. |
| 169 | for (int i = 0; i < size_; i++) { |
| 170 | if (array_[i] == uniq) return; |
| 171 | if (array_[i].raw_address_ > uniq.raw_address_) { |
| 172 | // Insert in the middle. |
| 173 | Grow(size_ + 1, zone); |
| 174 | for (int j = size_ - 1; j >= i; j--) array_[j + 1] = array_[j]; |
| 175 | array_[i] = uniq; |
| 176 | size_++; |
| 177 | return; |
| 178 | } |
| 179 | } |
| 180 | // Append the element to the the end. |
| 181 | Grow(size_ + 1, zone); |
| 182 | array_[size_++] = uniq; |
| 183 | } |
| 184 | |
| 185 | // Remove an element from this set. Mutates this set. O(|this|) |
| 186 | void Remove(Unique<T> uniq) { |
| 187 | for (int i = 0; i < size_; i++) { |
| 188 | if (array_[i] == uniq) { |
| 189 | while (++i < size_) array_[i - 1] = array_[i]; |
| 190 | size_--; |
| 191 | return; |
| 192 | } |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | // Compare this set against another set. O(|this|). |
| 197 | bool Equals(const UniqueSet<T>* that) const { |
| 198 | if (that->size_ != this->size_) return false; |
| 199 | for (int i = 0; i < this->size_; i++) { |
| 200 | if (this->array_[i] != that->array_[i]) return false; |
| 201 | } |
| 202 | return true; |
| 203 | } |
| 204 | |
| 205 | // Check whether this set contains the given element. O(|this|) |
| 206 | // TODO(titzer): use binary search for large sets to make this O(log|this|) |
| 207 | template <typename U> |
| 208 | bool Contains(const Unique<U> elem) const { |
| 209 | for (int i = 0; i < this->size_; ++i) { |
| 210 | Unique<T> cand = this->array_[i]; |
| 211 | if (cand.raw_address_ >= elem.raw_address_) { |
| 212 | return cand.raw_address_ == elem.raw_address_; |
| 213 | } |
| 214 | } |
| 215 | return false; |
| 216 | } |
| 217 | |
| 218 | // Check if this set is a subset of the given set. O(|this| + |that|). |
| 219 | bool IsSubset(const UniqueSet<T>* that) const { |
| 220 | if (that->size_ < this->size_) return false; |
| 221 | int j = 0; |
| 222 | for (int i = 0; i < this->size_; i++) { |
| 223 | Unique<T> sought = this->array_[i]; |
| 224 | while (true) { |
| 225 | if (sought == that->array_[j++]) break; |
| 226 | // Fail whenever there are more elements in {this} than {that}. |
| 227 | if ((this->size_ - i) > (that->size_ - j)) return false; |
| 228 | } |
| 229 | } |
| 230 | return true; |
| 231 | } |
| 232 | |
| 233 | // Returns a new set representing the intersection of this set and the other. |
| 234 | // O(|this| + |that|). |
| 235 | UniqueSet<T>* Intersect(const UniqueSet<T>* that, Zone* zone) const { |
| 236 | if (that->size_ == 0 || this->size_ == 0) return new(zone) UniqueSet<T>(); |
| 237 | |
| 238 | UniqueSet<T>* out = new(zone) UniqueSet<T>( |
| 239 | Min(this->size_, that->size_), zone); |
| 240 | |
| 241 | int i = 0, j = 0, k = 0; |
| 242 | while (i < this->size_ && j < that->size_) { |
| 243 | Unique<T> a = this->array_[i]; |
| 244 | Unique<T> b = that->array_[j]; |
| 245 | if (a == b) { |
| 246 | out->array_[k++] = a; |
| 247 | i++; |
| 248 | j++; |
| 249 | } else if (a.raw_address_ < b.raw_address_) { |
| 250 | i++; |
| 251 | } else { |
| 252 | j++; |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | out->size_ = k; |
| 257 | return out; |
| 258 | } |
| 259 | |
| 260 | // Returns a new set representing the union of this set and the other. |
| 261 | // O(|this| + |that|). |
| 262 | UniqueSet<T>* Union(const UniqueSet<T>* that, Zone* zone) const { |
| 263 | if (that->size_ == 0) return this->Copy(zone); |
| 264 | if (this->size_ == 0) return that->Copy(zone); |
| 265 | |
| 266 | UniqueSet<T>* out = new(zone) UniqueSet<T>( |
| 267 | this->size_ + that->size_, zone); |
| 268 | |
| 269 | int i = 0, j = 0, k = 0; |
| 270 | while (i < this->size_ && j < that->size_) { |
| 271 | Unique<T> a = this->array_[i]; |
| 272 | Unique<T> b = that->array_[j]; |
| 273 | if (a == b) { |
| 274 | out->array_[k++] = a; |
| 275 | i++; |
| 276 | j++; |
| 277 | } else if (a.raw_address_ < b.raw_address_) { |
| 278 | out->array_[k++] = a; |
| 279 | i++; |
| 280 | } else { |
| 281 | out->array_[k++] = b; |
| 282 | j++; |
| 283 | } |
| 284 | } |
| 285 | |
| 286 | while (i < this->size_) out->array_[k++] = this->array_[i++]; |
| 287 | while (j < that->size_) out->array_[k++] = that->array_[j++]; |
| 288 | |
| 289 | out->size_ = k; |
| 290 | return out; |
| 291 | } |
| 292 | |
| 293 | // Returns a new set representing all elements from this set which are not in |
| 294 | // that set. O(|this| * |that|). |
| 295 | UniqueSet<T>* Subtract(const UniqueSet<T>* that, Zone* zone) const { |
| 296 | if (that->size_ == 0) return this->Copy(zone); |
| 297 | |
| 298 | UniqueSet<T>* out = new(zone) UniqueSet<T>(this->size_, zone); |
| 299 | |
| 300 | int i = 0, j = 0; |
| 301 | while (i < this->size_) { |
| 302 | Unique<T> cand = this->array_[i]; |
| 303 | if (!that->Contains(cand)) { |
| 304 | out->array_[j++] = cand; |
| 305 | } |
| 306 | i++; |
| 307 | } |
| 308 | |
| 309 | out->size_ = j; |
| 310 | return out; |
| 311 | } |
| 312 | |
| 313 | // Makes an exact copy of this set. O(|this|). |
| 314 | UniqueSet<T>* Copy(Zone* zone) const { |
| 315 | UniqueSet<T>* copy = new(zone) UniqueSet<T>(this->size_, zone); |
| 316 | copy->size_ = this->size_; |
| 317 | memcpy(copy->array_, this->array_, this->size_ * sizeof(Unique<T>)); |
| 318 | return copy; |
| 319 | } |
| 320 | |
| 321 | void Clear() { |
| 322 | size_ = 0; |
| 323 | } |
| 324 | |
| 325 | inline int size() const { |
| 326 | return size_; |
| 327 | } |
| 328 | |
| 329 | inline Unique<T> at(int index) const { |
| 330 | DCHECK(index >= 0 && index < size_); |
| 331 | return array_[index]; |
| 332 | } |
| 333 | |
| 334 | private: |
| 335 | // These sets should be small, since operations are implemented with simple |
| 336 | // linear algorithms. Enforce a maximum size. |
| 337 | static const int kMaxCapacity = 65535; |
| 338 | |
| 339 | uint16_t size_; |
| 340 | uint16_t capacity_; |
| 341 | Unique<T>* array_; |
| 342 | |
| 343 | // Grow the size of internal storage to be at least {size} elements. |
| 344 | void Grow(int size, Zone* zone) { |
| 345 | CHECK(size < kMaxCapacity); // Enforce maximum size. |
| 346 | if (capacity_ < size) { |
| 347 | int new_capacity = 2 * capacity_ + size; |
| 348 | if (new_capacity > kMaxCapacity) new_capacity = kMaxCapacity; |
| 349 | Unique<T>* new_array = zone->NewArray<Unique<T> >(new_capacity); |
| 350 | if (size_ > 0) { |
| 351 | memcpy(new_array, array_, size_ * sizeof(Unique<T>)); |
| 352 | } |
| 353 | capacity_ = new_capacity; |
| 354 | array_ = new_array; |
| 355 | } |
| 356 | } |
| 357 | }; |
| 358 | |
| 359 | } // namespace internal |
| 360 | } // namespace v8 |
| 361 | |
| 362 | #endif // V8_CRANKSHAFT_UNIQUE_H_ |