include/llvm/ADT/SmallVector.h

   1 //===- llvm/ADT/SmallVector.h - 'Normally small' vectors --------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines the SmallVector class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_ADT_SMALLVECTOR_H
  14 #define LLVM_ADT_SMALLVECTOR_H
  15
  16 #include "llvm/ADT/iterator_range.h"
  17 #include "llvm/Support/AlignOf.h"
  18 #include "llvm/Support/Compiler.h"
  19 #include "llvm/Support/MathExtras.h"
  20 #include "llvm/Support/MemAlloc.h"
  21 #include "llvm/Support/type_traits.h"
  22 #include "llvm/Support/ErrorHandling.h"
  23 #include <algorithm>
  24 #include <cassert>
  25 #include <cstddef>
  26 #include <cstdlib>
  27 #include <cstring>
  28 #include <initializer_list>
  29 #include <iterator>
  30 #include <memory>
  31 #include <new>
  32 #include <type_traits>
  33 #include <utility>
  34
  35 namespace llvm {
  36
  37 /// This is all the non-templated stuff common to all SmallVectors.
  38 class SmallVectorBase {
  39 protected:
  40   void *BeginX;
  41   unsigned Size = 0, Capacity;
  42
  43   SmallVectorBase() = delete;
  44   SmallVectorBase(void *FirstEl, size_t TotalCapacity)
  45       : BeginX(FirstEl), Capacity(TotalCapacity) {}
  46
  47   /// This is an implementation of the grow() method which only works
  48   /// on POD-like data types and is out of line to reduce code duplication.
  49   void grow_pod(void *FirstEl, size_t MinCapacity, size_t TSize);
  50
  51 public:
  52   size_t size() const { return Size; }
  53   size_t capacity() const { return Capacity; }
  54
  55   LLVM_NODISCARD bool empty() const { return !Size; }
  56
  57   /// Set the array size to \p N, which the current array must have enough
  58   /// capacity for.
  59   ///
  60   /// This does not construct or destroy any elements in the vector.
  61   ///
  62   /// Clients can use this in conjunction with capacity() to write past the end
  63   /// of the buffer when they know that more elements are available, and only
  64   /// update the size later. This avoids the cost of value initializing elements
  65   /// which will only be overwritten.
  66   void set_size(size_t N) {
  67     assert(N <= capacity());
  68     Size = N;
  69   }
  70 };
  71
  72 /// Figure out the offset of the first element.
  73 template <class T, typename = void> struct SmallVectorAlignmentAndSize {
  74   AlignedCharArrayUnion<SmallVectorBase> Base;
  75   AlignedCharArrayUnion<T> FirstEl;
  76 };
  77
  78 /// This is the part of SmallVectorTemplateBase which does not depend on whether
  79 /// the type T is a POD. The extra dummy template argument is used by ArrayRef
  80 /// to avoid unnecessarily requiring T to be complete.
  81 template <typename T, typename = void>
  82 class SmallVectorTemplateCommon : public SmallVectorBase {
  83   /// Find the address of the first element.  For this pointer math to be valid
  84   /// with small-size of 0 for T with lots of alignment, it's important that
  85   /// SmallVectorStorage is properly-aligned even for small-size of 0.
  86   void *getFirstEl() const {
  87     return const_cast<void *>(reinterpret_cast<const void *>(
  88         reinterpret_cast<const char *>(this) +
  89         offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)));
  90   }
  91   // Space after 'FirstEl' is clobbered, do not add any instance vars after it.
  92
  93 protected:
  94   SmallVectorTemplateCommon(size_t Size)
  95       : SmallVectorBase(getFirstEl(), Size) {}
  96
  97   void grow_pod(size_t MinCapacity, size_t TSize) {
  98     SmallVectorBase::grow_pod(getFirstEl(), MinCapacity, TSize);
  99   }
 100
 101   /// Return true if this is a smallvector which has not had dynamic
 102   /// memory allocated for it.
 103   bool isSmall() const { return BeginX == getFirstEl(); }
 104
 105   /// Put this vector in a state of being small.
 106   void resetToSmall() {
 107     BeginX = getFirstEl();
 108     Size = Capacity = 0; // FIXME: Setting Capacity to 0 is suspect.
 109   }
 110
 111 public:
 112   using size_type = size_t;
 113   using difference_type = ptrdiff_t;
 114   using value_type = T;
 115   using iterator = T *;
 116   using const_iterator = const T *;
 117
 118   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 119   using reverse_iterator = std::reverse_iterator<iterator>;
 120
 121   using reference = T &;
 122   using const_reference = const T &;
 123   using pointer = T *;
 124   using const_pointer = const T *;
 125
 126   // forward iterator creation methods.
 127   iterator begin() { return (iterator)this->BeginX; }
 128   const_iterator begin() const { return (const_iterator)this->BeginX; }
 129   iterator end() { return begin() + size(); }
 130   const_iterator end() const { return begin() + size(); }
 131
 132   // reverse iterator creation methods.
 133   reverse_iterator rbegin()            { return reverse_iterator(end()); }
 134   const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
 135   reverse_iterator rend()              { return reverse_iterator(begin()); }
 136   const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
 137
 138   size_type size_in_bytes() const { return size() * sizeof(T); }
 139   size_type max_size() const { return size_type(-1) / sizeof(T); }
 140
 141   size_t capacity_in_bytes() const { return capacity() * sizeof(T); }
 142
 143   /// Return a pointer to the vector's buffer, even if empty().
 144   pointer data() { return pointer(begin()); }
 145   /// Return a pointer to the vector's buffer, even if empty().
 146   const_pointer data() const { return const_pointer(begin()); }
 147
 148   reference operator[](size_type idx) {
 149     assert(idx < size());
 150     return begin()[idx];
 151   }
 152   const_reference operator[](size_type idx) const {
 153     assert(idx < size());
 154     return begin()[idx];
 155   }
 156
 157   reference front() {
 158     assert(!empty());
 159     return begin()[0];
 160   }
 161   const_reference front() const {
 162     assert(!empty());
 163     return begin()[0];
 164   }
 165
 166   reference back() {
 167     assert(!empty());
 168     return end()[-1];
 169   }
 170   const_reference back() const {
 171     assert(!empty());
 172     return end()[-1];
 173   }
 174 };
 175
 176 /// SmallVectorTemplateBase<TriviallyCopyable = false> - This is where we put method
 177 /// implementations that are designed to work with non-POD-like T's.
 178 template <typename T, bool = is_trivially_copyable<T>::value>
 179 class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
 180 protected:
 181   SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
 182
 183   static void destroy_range(T *S, T *E) {
 184     while (S != E) {
 185       --E;
 186       E->~T();
 187     }
 188   }
 189
 190   /// Move the range [I, E) into the uninitialized memory starting with "Dest",
 191   /// constructing elements as needed.
 192   template<typename It1, typename It2>
 193   static void uninitialized_move(It1 I, It1 E, It2 Dest) {
 194     std::uninitialized_copy(std::make_move_iterator(I),
 195                             std::make_move_iterator(E), Dest);
 196   }
 197
 198   /// Copy the range [I, E) onto the uninitialized memory starting with "Dest",
 199   /// constructing elements as needed.
 200   template<typename It1, typename It2>
 201   static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
 202     std::uninitialized_copy(I, E, Dest);
 203   }
 204
 205   /// Grow the allocated memory (without initializing new elements), doubling
 206   /// the size of the allocated memory. Guarantees space for at least one more
 207   /// element, or MinSize more elements if specified.
 208   void grow(size_t MinSize = 0);
 209
 210 public:
 211   void push_back(const T &Elt) {
 212     if (LLVM_UNLIKELY(this->size() >= this->capacity()))
 213       this->grow();
 214     ::new ((void*) this->end()) T(Elt);
 215     this->set_size(this->size() + 1);
 216   }
 217
 218   void push_back(T &&Elt) {
 219     if (LLVM_UNLIKELY(this->size() >= this->capacity()))
 220       this->grow();
 221     ::new ((void*) this->end()) T(::std::move(Elt));
 222     this->set_size(this->size() + 1);
 223   }
 224
 225   void pop_back() {
 226     this->set_size(this->size() - 1);
 227     this->end()->~T();
 228   }
 229 };
 230
 231 // Define this out-of-line to dissuade the C++ compiler from inlining it.
 232 template <typename T, bool TriviallyCopyable>
 233 void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
 234   if (MinSize > UINT32_MAX)
 235     report_bad_alloc_error("SmallVector capacity overflow during allocation");
 236
 237   // Always grow, even from zero.
 238   size_t NewCapacity = size_t(NextPowerOf2(this->capacity() + 2));
 239   NewCapacity = std::min(std::max(NewCapacity, MinSize), size_t(UINT32_MAX));
 240   T *NewElts = static_cast<T*>(llvm::safe_malloc(NewCapacity*sizeof(T)));
 241
 242   // Move the elements over.
 243   this->uninitialized_move(this->begin(), this->end(), NewElts);
 244
 245   // Destroy the original elements.
 246   destroy_range(this->begin(), this->end());
 247
 248   // If this wasn't grown from the inline copy, deallocate the old space.
 249   if (!this->isSmall())
 250     free(this->begin());
 251
 252   this->BeginX = NewElts;
 253   this->Capacity = NewCapacity;
 254 }
 255
 256 /// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put
 257 /// method implementations that are designed to work with POD-like T's.
 258 template <typename T>
 259 class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
 260 protected:
 261   SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
 262
 263   // No need to do a destroy loop for POD's.
 264   static void destroy_range(T *, T *) {}
 265
 266   /// Move the range [I, E) onto the uninitialized memory
 267   /// starting with "Dest", constructing elements into it as needed.
 268   template<typename It1, typename It2>
 269   static void uninitialized_move(It1 I, It1 E, It2 Dest) {
 270     // Just do a copy.
 271     uninitialized_copy(I, E, Dest);
 272   }
 273
 274   /// Copy the range [I, E) onto the uninitialized memory
 275   /// starting with "Dest", constructing elements into it as needed.
 276   template<typename It1, typename It2>
 277   static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
 278     // Arbitrary iterator types; just use the basic implementation.
 279     std::uninitialized_copy(I, E, Dest);
 280   }
 281
 282   /// Copy the range [I, E) onto the uninitialized memory
 283   /// starting with "Dest", constructing elements into it as needed.
 284   template <typename T1, typename T2>
 285   static void uninitialized_copy(
 286       T1 *I, T1 *E, T2 *Dest,
 287       typename std::enable_if<std::is_same<typename std::remove_const<T1>::type,
 288                                            T2>::value>::type * = nullptr) {
 289     // Use memcpy for PODs iterated by pointers (which includes SmallVector
 290     // iterators): std::uninitialized_copy optimizes to memmove, but we can
 291     // use memcpy here. Note that I and E are iterators and thus might be
 292     // invalid for memcpy if they are equal.
 293     if (I != E)
 294       memcpy(reinterpret_cast<void *>(Dest), I, (E - I) * sizeof(T));
 295   }
 296
 297   /// Double the size of the allocated memory, guaranteeing space for at
 298   /// least one more element or MinSize if specified.
 299   void grow(size_t MinSize = 0) { this->grow_pod(MinSize, sizeof(T)); }
 300
 301 public:
 302   void push_back(const T &Elt) {
 303     if (LLVM_UNLIKELY(this->size() >= this->capacity()))
 304       this->grow();
 305     memcpy(reinterpret_cast<void *>(this->end()), &Elt, sizeof(T));
 306     this->set_size(this->size() + 1);
 307   }
 308
 309   void pop_back() { this->set_size(this->size() - 1); }
 310 };
 311
 312 /// This class consists of common code factored out of the SmallVector class to
 313 /// reduce code duplication based on the SmallVector 'N' template parameter.
 314 template <typename T>
 315 class SmallVectorImpl : public SmallVectorTemplateBase<T> {
 316   using SuperClass = SmallVectorTemplateBase<T>;
 317
 318 public:
 319   using iterator = typename SuperClass::iterator;
 320   using const_iterator = typename SuperClass::const_iterator;
 321   using reference = typename SuperClass::reference;
 322   using size_type = typename SuperClass::size_type;
 323
 324 protected:
 325   // Default ctor - Initialize to empty.
 326   explicit SmallVectorImpl(unsigned N)
 327       : SmallVectorTemplateBase<T>(N) {}
 328
 329 public:
 330   SmallVectorImpl(const SmallVectorImpl &) = delete;
 331
 332   ~SmallVectorImpl() {
 333     // Subclass has already destructed this vector's elements.
 334     // If this wasn't grown from the inline copy, deallocate the old space.
 335     if (!this->isSmall())
 336       free(this->begin());
 337   }
 338
 339   void clear() {
 340     this->destroy_range(this->begin(), this->end());
 341     this->Size = 0;
 342   }
 343
 344   void resize(size_type N) {
 345     if (N < this->size()) {
 346       this->destroy_range(this->begin()+N, this->end());
 347       this->set_size(N);
 348     } else if (N > this->size()) {
 349       if (this->capacity() < N)
 350         this->grow(N);
 351       for (auto I = this->end(), E = this->begin() + N; I != E; ++I)
 352         new (&*I) T();
 353       this->set_size(N);
 354     }
 355   }
 356
 357   void resize(size_type N, const T &NV) {
 358     if (N < this->size()) {
 359       this->destroy_range(this->begin()+N, this->end());
 360       this->set_size(N);
 361     } else if (N > this->size()) {
 362       if (this->capacity() < N)
 363         this->grow(N);
 364       std::uninitialized_fill(this->end(), this->begin()+N, NV);
 365       this->set_size(N);
 366     }
 367   }
 368
 369   void reserve(size_type N) {
 370     if (this->capacity() < N)
 371       this->grow(N);
 372   }
 373
 374   LLVM_NODISCARD T pop_back_val() {
 375     T Result = ::std::move(this->back());
 376     this->pop_back();
 377     return Result;
 378   }
 379
 380   void swap(SmallVectorImpl &RHS);
 381
 382   /// Add the specified range to the end of the SmallVector.
 383   template <typename in_iter,
 384             typename = typename std::enable_if<std::is_convertible<
 385                 typename std::iterator_traits<in_iter>::iterator_category,
 386                 std::input_iterator_tag>::value>::type>
 387   void append(in_iter in_start, in_iter in_end) {
 388     size_type NumInputs = std::distance(in_start, in_end);
 389     if (NumInputs > this->capacity() - this->size())
 390       this->grow(this->size()+NumInputs);
 391
 392     this->uninitialized_copy(in_start, in_end, this->end());
 393     this->set_size(this->size() + NumInputs);
 394   }
 395
 396   /// Append \p NumInputs copies of \p Elt to the end.
 397   void append(size_type NumInputs, const T &Elt) {
 398     if (NumInputs > this->capacity() - this->size())
 399       this->grow(this->size()+NumInputs);
 400
 401     std::uninitialized_fill_n(this->end(), NumInputs, Elt);
 402     this->set_size(this->size() + NumInputs);
 403   }
 404
 405   void append(std::initializer_list<T> IL) {
 406     append(IL.begin(), IL.end());
 407   }
 408
 409   // FIXME: Consider assigning over existing elements, rather than clearing &
 410   // re-initializing them - for all assign(...) variants.
 411
 412   void assign(size_type NumElts, const T &Elt) {
 413     clear();
 414     if (this->capacity() < NumElts)
 415       this->grow(NumElts);
 416     this->set_size(NumElts);
 417     std::uninitialized_fill(this->begin(), this->end(), Elt);
 418   }
 419
 420   template <typename in_iter,
 421             typename = typename std::enable_if<std::is_convertible<
 422                 typename std::iterator_traits<in_iter>::iterator_category,
 423                 std::input_iterator_tag>::value>::type>
 424   void assign(in_iter in_start, in_iter in_end) {
 425     clear();
 426     append(in_start, in_end);
 427   }
 428
 429   void assign(std::initializer_list<T> IL) {
 430     clear();
 431     append(IL);
 432   }
 433
 434   iterator erase(const_iterator CI) {
 435     // Just cast away constness because this is a non-const member function.
 436     iterator I = const_cast<iterator>(CI);
 437
 438     assert(I >= this->begin() && "Iterator to erase is out of bounds.");
 439     assert(I < this->end() && "Erasing at past-the-end iterator.");
 440
 441     iterator N = I;
 442     // Shift all elts down one.
 443     std::move(I+1, this->end(), I);
 444     // Drop the last elt.
 445     this->pop_back();
 446     return(N);
 447   }
 448
 449   iterator erase(const_iterator CS, const_iterator CE) {
 450     // Just cast away constness because this is a non-const member function.
 451     iterator S = const_cast<iterator>(CS);
 452     iterator E = const_cast<iterator>(CE);
 453
 454     assert(S >= this->begin() && "Range to erase is out of bounds.");
 455     assert(S <= E && "Trying to erase invalid range.");
 456     assert(E <= this->end() && "Trying to erase past the end.");
 457
 458     iterator N = S;
 459     // Shift all elts down.
 460     iterator I = std::move(E, this->end(), S);
 461     // Drop the last elts.
 462     this->destroy_range(I, this->end());
 463     this->set_size(I - this->begin());
 464     return(N);
 465   }
 466
 467   iterator insert(iterator I, T &&Elt) {
 468     if (I == this->end()) {  // Important special case for empty vector.
 469       this->push_back(::std::move(Elt));
 470       return this->end()-1;
 471     }
 472
 473     assert(I >= this->begin() && "Insertion iterator is out of bounds.");
 474     assert(I <= this->end() && "Inserting past the end of the vector.");
 475
 476     if (this->size() >= this->capacity()) {
 477       size_t EltNo = I-this->begin();
 478       this->grow();
 479       I = this->begin()+EltNo;
 480     }
 481
 482     ::new ((void*) this->end()) T(::std::move(this->back()));
 483     // Push everything else over.
 484     std::move_backward(I, this->end()-1, this->end());
 485     this->set_size(this->size() + 1);
 486
 487     // If we just moved the element we're inserting, be sure to update
 488     // the reference.
 489     T *EltPtr = &Elt;
 490     if (I <= EltPtr && EltPtr < this->end())
 491       ++EltPtr;
 492
 493     *I = ::std::move(*EltPtr);
 494     return I;
 495   }
 496
 497   iterator insert(iterator I, const T &Elt) {
 498     if (I == this->end()) {  // Important special case for empty vector.
 499       this->push_back(Elt);
 500       return this->end()-1;
 501     }
 502
 503     assert(I >= this->begin() && "Insertion iterator is out of bounds.");
 504     assert(I <= this->end() && "Inserting past the end of the vector.");
 505
 506     if (this->size() >= this->capacity()) {
 507       size_t EltNo = I-this->begin();
 508       this->grow();
 509       I = this->begin()+EltNo;
 510     }
 511     ::new ((void*) this->end()) T(std::move(this->back()));
 512     // Push everything else over.
 513     std::move_backward(I, this->end()-1, this->end());
 514     this->set_size(this->size() + 1);
 515
 516     // If we just moved the element we're inserting, be sure to update
 517     // the reference.
 518     const T *EltPtr = &Elt;
 519     if (I <= EltPtr && EltPtr < this->end())
 520       ++EltPtr;
 521
 522     *I = *EltPtr;
 523     return I;
 524   }
 525
 526   iterator insert(iterator I, size_type NumToInsert, const T &Elt) {
 527     // Convert iterator to elt# to avoid invalidating iterator when we reserve()
 528     size_t InsertElt = I - this->begin();
 529
 530     if (I == this->end()) {  // Important special case for empty vector.
 531       append(NumToInsert, Elt);
 532       return this->begin()+InsertElt;
 533     }
 534
 535     assert(I >= this->begin() && "Insertion iterator is out of bounds.");
 536     assert(I <= this->end() && "Inserting past the end of the vector.");
 537
 538     // Ensure there is enough space.
 539     reserve(this->size() + NumToInsert);
 540
 541     // Uninvalidate the iterator.
 542     I = this->begin()+InsertElt;
 543
 544     // If there are more elements between the insertion point and the end of the
 545     // range than there are being inserted, we can use a simple approach to
 546     // insertion.  Since we already reserved space, we know that this won't
 547     // reallocate the vector.
 548     if (size_t(this->end()-I) >= NumToInsert) {
 549       T *OldEnd = this->end();
 550       append(std::move_iterator<iterator>(this->end() - NumToInsert),
 551              std::move_iterator<iterator>(this->end()));
 552
 553       // Copy the existing elements that get replaced.
 554       std::move_backward(I, OldEnd-NumToInsert, OldEnd);
 555
 556       std::fill_n(I, NumToInsert, Elt);
 557       return I;
 558     }
 559
 560     // Otherwise, we're inserting more elements than exist already, and we're
 561     // not inserting at the end.
 562
 563     // Move over the elements that we're about to overwrite.
 564     T *OldEnd = this->end();
 565     this->set_size(this->size() + NumToInsert);
 566     size_t NumOverwritten = OldEnd-I;
 567     this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
 568
 569     // Replace the overwritten part.
 570     std::fill_n(I, NumOverwritten, Elt);
 571
 572     // Insert the non-overwritten middle part.
 573     std::uninitialized_fill_n(OldEnd, NumToInsert-NumOverwritten, Elt);
 574     return I;
 575   }
 576
 577   template <typename ItTy,
 578             typename = typename std::enable_if<std::is_convertible<
 579                 typename std::iterator_traits<ItTy>::iterator_category,
 580                 std::input_iterator_tag>::value>::type>
 581   iterator insert(iterator I, ItTy From, ItTy To) {
 582     // Convert iterator to elt# to avoid invalidating iterator when we reserve()
 583     size_t InsertElt = I - this->begin();
 584
 585     if (I == this->end()) {  // Important special case for empty vector.
 586       append(From, To);
 587       return this->begin()+InsertElt;
 588     }
 589
 590     assert(I >= this->begin() && "Insertion iterator is out of bounds.");
 591     assert(I <= this->end() && "Inserting past the end of the vector.");
 592
 593     size_t NumToInsert = std::distance(From, To);
 594
 595     // Ensure there is enough space.
 596     reserve(this->size() + NumToInsert);
 597
 598     // Uninvalidate the iterator.
 599     I = this->begin()+InsertElt;
 600
 601     // If there are more elements between the insertion point and the end of the
 602     // range than there are being inserted, we can use a simple approach to
 603     // insertion.  Since we already reserved space, we know that this won't
 604     // reallocate the vector.
 605     if (size_t(this->end()-I) >= NumToInsert) {
 606       T *OldEnd = this->end();
 607       append(std::move_iterator<iterator>(this->end() - NumToInsert),
 608              std::move_iterator<iterator>(this->end()));
 609
 610       // Copy the existing elements that get replaced.
 611       std::move_backward(I, OldEnd-NumToInsert, OldEnd);
 612
 613       std::copy(From, To, I);
 614       return I;
 615     }
 616
 617     // Otherwise, we're inserting more elements than exist already, and we're
 618     // not inserting at the end.
 619
 620     // Move over the elements that we're about to overwrite.
 621     T *OldEnd = this->end();
 622     this->set_size(this->size() + NumToInsert);
 623     size_t NumOverwritten = OldEnd-I;
 624     this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
 625
 626     // Replace the overwritten part.
 627     for (T *J = I; NumOverwritten > 0; --NumOverwritten) {
 628       *J = *From;
 629       ++J; ++From;
 630     }
 631
 632     // Insert the non-overwritten middle part.
 633     this->uninitialized_copy(From, To, OldEnd);
 634     return I;
 635   }
 636
 637   void insert(iterator I, std::initializer_list<T> IL) {
 638     insert(I, IL.begin(), IL.end());
 639   }
 640
 641   template <typename... ArgTypes> reference emplace_back(ArgTypes &&... Args) {
 642     if (LLVM_UNLIKELY(this->size() >= this->capacity()))
 643       this->grow();
 644     ::new ((void *)this->end()) T(std::forward<ArgTypes>(Args)...);
 645     this->set_size(this->size() + 1);
 646     return this->back();
 647   }
 648
 649   SmallVectorImpl &operator=(const SmallVectorImpl &RHS);
 650
 651   SmallVectorImpl &operator=(SmallVectorImpl &&RHS);
 652
 653   bool operator==(const SmallVectorImpl &RHS) const {
 654     if (this->size() != RHS.size()) return false;
 655     return std::equal(this->begin(), this->end(), RHS.begin());
 656   }
 657   bool operator!=(const SmallVectorImpl &RHS) const {
 658     return !(*this == RHS);
 659   }
 660
 661   bool operator<(const SmallVectorImpl &RHS) const {
 662     return std::lexicographical_compare(this->begin(), this->end(),
 663                                         RHS.begin(), RHS.end());
 664   }
 665 };
 666
 667 template <typename T>
 668 void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
 669   if (this == &RHS) return;
 670
 671   // We can only avoid copying elements if neither vector is small.
 672   if (!this->isSmall() && !RHS.isSmall()) {
 673     std::swap(this->BeginX, RHS.BeginX);
 674     std::swap(this->Size, RHS.Size);
 675     std::swap(this->Capacity, RHS.Capacity);
 676     return;
 677   }
 678   if (RHS.size() > this->capacity())
 679     this->grow(RHS.size());
 680   if (this->size() > RHS.capacity())
 681     RHS.grow(this->size());
 682
 683   // Swap the shared elements.
 684   size_t NumShared = this->size();
 685   if (NumShared > RHS.size()) NumShared = RHS.size();
 686   for (size_type i = 0; i != NumShared; ++i)
 687     std::swap((*this)[i], RHS[i]);
 688
 689   // Copy over the extra elts.
 690   if (this->size() > RHS.size()) {
 691     size_t EltDiff = this->size() - RHS.size();
 692     this->uninitialized_copy(this->begin()+NumShared, this->end(), RHS.end());
 693     RHS.set_size(RHS.size() + EltDiff);
 694     this->destroy_range(this->begin()+NumShared, this->end());
 695     this->set_size(NumShared);
 696   } else if (RHS.size() > this->size()) {
 697     size_t EltDiff = RHS.size() - this->size();
 698     this->uninitialized_copy(RHS.begin()+NumShared, RHS.end(), this->end());
 699     this->set_size(this->size() + EltDiff);
 700     this->destroy_range(RHS.begin()+NumShared, RHS.end());
 701     RHS.set_size(NumShared);
 702   }
 703 }
 704
 705 template <typename T>
 706 SmallVectorImpl<T> &SmallVectorImpl<T>::
 707   operator=(const SmallVectorImpl<T> &RHS) {
 708   // Avoid self-assignment.
 709   if (this == &RHS) return *this;
 710
 711   // If we already have sufficient space, assign the common elements, then
 712   // destroy any excess.
 713   size_t RHSSize = RHS.size();
 714   size_t CurSize = this->size();
 715   if (CurSize >= RHSSize) {
 716     // Assign common elements.
 717     iterator NewEnd;
 718     if (RHSSize)
 719       NewEnd = std::copy(RHS.begin(), RHS.begin()+RHSSize, this->begin());
 720     else
 721       NewEnd = this->begin();
 722
 723     // Destroy excess elements.
 724     this->destroy_range(NewEnd, this->end());
 725
 726     // Trim.
 727     this->set_size(RHSSize);
 728     return *this;
 729   }
 730
 731   // If we have to grow to have enough elements, destroy the current elements.
 732   // This allows us to avoid copying them during the grow.
 733   // FIXME: don't do this if they're efficiently moveable.
 734   if (this->capacity() < RHSSize) {
 735     // Destroy current elements.
 736     this->destroy_range(this->begin(), this->end());
 737     this->set_size(0);
 738     CurSize = 0;
 739     this->grow(RHSSize);
 740   } else if (CurSize) {
 741     // Otherwise, use assignment for the already-constructed elements.
 742     std::copy(RHS.begin(), RHS.begin()+CurSize, this->begin());
 743   }
 744
 745   // Copy construct the new elements in place.
 746   this->uninitialized_copy(RHS.begin()+CurSize, RHS.end(),
 747                            this->begin()+CurSize);
 748
 749   // Set end.
 750   this->set_size(RHSSize);
 751   return *this;
 752 }
 753
 754 template <typename T>
 755 SmallVectorImpl<T> &SmallVectorImpl<T>::operator=(SmallVectorImpl<T> &&RHS) {
 756   // Avoid self-assignment.
 757   if (this == &RHS) return *this;
 758
 759   // If the RHS isn't small, clear this vector and then steal its buffer.
 760   if (!RHS.isSmall()) {
 761     this->destroy_range(this->begin(), this->end());
 762     if (!this->isSmall()) free(this->begin());
 763     this->BeginX = RHS.BeginX;
 764     this->Size = RHS.Size;
 765     this->Capacity = RHS.Capacity;
 766     RHS.resetToSmall();
 767     return *this;
 768   }
 769
 770   // If we already have sufficient space, assign the common elements, then
 771   // destroy any excess.
 772   size_t RHSSize = RHS.size();
 773   size_t CurSize = this->size();
 774   if (CurSize >= RHSSize) {
 775     // Assign common elements.
 776     iterator NewEnd = this->begin();
 777     if (RHSSize)
 778       NewEnd = std::move(RHS.begin(), RHS.end(), NewEnd);
 779
 780     // Destroy excess elements and trim the bounds.
 781     this->destroy_range(NewEnd, this->end());
 782     this->set_size(RHSSize);
 783
 784     // Clear the RHS.
 785     RHS.clear();
 786
 787     return *this;
 788   }
 789
 790   // If we have to grow to have enough elements, destroy the current elements.
 791   // This allows us to avoid copying them during the grow.
 792   // FIXME: this may not actually make any sense if we can efficiently move
 793   // elements.
 794   if (this->capacity() < RHSSize) {
 795     // Destroy current elements.
 796     this->destroy_range(this->begin(), this->end());
 797     this->set_size(0);
 798     CurSize = 0;
 799     this->grow(RHSSize);
 800   } else if (CurSize) {
 801     // Otherwise, use assignment for the already-constructed elements.
 802     std::move(RHS.begin(), RHS.begin()+CurSize, this->begin());
 803   }
 804
 805   // Move-construct the new elements in place.
 806   this->uninitialized_move(RHS.begin()+CurSize, RHS.end(),
 807                            this->begin()+CurSize);
 808
 809   // Set end.
 810   this->set_size(RHSSize);
 811
 812   RHS.clear();
 813   return *this;
 814 }
 815
 816 /// Storage for the SmallVector elements.  This is specialized for the N=0 case
 817 /// to avoid allocating unnecessary storage.
 818 template <typename T, unsigned N>
 819 struct SmallVectorStorage {
 820   AlignedCharArrayUnion<T> InlineElts[N];
 821 };
 822
 823 /// We need the storage to be properly aligned even for small-size of 0 so that
 824 /// the pointer math in \a SmallVectorTemplateCommon::getFirstEl() is
 825 /// well-defined.
 826 template <typename T> struct alignas(alignof(T)) SmallVectorStorage<T, 0> {};
 827
 828 /// This is a 'vector' (really, a variable-sized array), optimized
 829 /// for the case when the array is small.  It contains some number of elements
 830 /// in-place, which allows it to avoid heap allocation when the actual number of
 831 /// elements is below that threshold.  This allows normal "small" cases to be
 832 /// fast without losing generality for large inputs.
 833 ///
 834 /// Note that this does not attempt to be exception safe.
 835 ///
 836 template <typename T, unsigned N>
 837 class SmallVector : public SmallVectorImpl<T>, SmallVectorStorage<T, N> {
 838 public:
 839   SmallVector() : SmallVectorImpl<T>(N) {}
 840
 841   ~SmallVector() {
 842     // Destroy the constructed elements in the vector.
 843     this->destroy_range(this->begin(), this->end());
 844   }
 845
 846   explicit SmallVector(size_t Size, const T &Value = T())
 847     : SmallVectorImpl<T>(N) {
 848     this->assign(Size, Value);
 849   }
 850
 851   template <typename ItTy,
 852             typename = typename std::enable_if<std::is_convertible<
 853                 typename std::iterator_traits<ItTy>::iterator_category,
 854                 std::input_iterator_tag>::value>::type>
 855   SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) {
 856     this->append(S, E);
 857   }
 858
 859   template <typename RangeTy>
 860   explicit SmallVector(const iterator_range<RangeTy> &R)
 861       : SmallVectorImpl<T>(N) {
 862     this->append(R.begin(), R.end());
 863   }
 864
 865   SmallVector(std::initializer_list<T> IL) : SmallVectorImpl<T>(N) {
 866     this->assign(IL);
 867   }
 868
 869   SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) {
 870     if (!RHS.empty())
 871       SmallVectorImpl<T>::operator=(RHS);
 872   }
 873
 874   const SmallVector &operator=(const SmallVector &RHS) {
 875     SmallVectorImpl<T>::operator=(RHS);
 876     return *this;
 877   }
 878
 879   SmallVector(SmallVector &&RHS) : SmallVectorImpl<T>(N) {
 880     if (!RHS.empty())
 881       SmallVectorImpl<T>::operator=(::std::move(RHS));
 882   }
 883
 884   SmallVector(SmallVectorImpl<T> &&RHS) : SmallVectorImpl<T>(N) {
 885     if (!RHS.empty())
 886       SmallVectorImpl<T>::operator=(::std::move(RHS));
 887   }
 888
 889   const SmallVector &operator=(SmallVector &&RHS) {
 890     SmallVectorImpl<T>::operator=(::std::move(RHS));
 891     return *this;
 892   }
 893
 894   const SmallVector &operator=(SmallVectorImpl<T> &&RHS) {
 895     SmallVectorImpl<T>::operator=(::std::move(RHS));
 896     return *this;
 897   }
 898
 899   const SmallVector &operator=(std::initializer_list<T> IL) {
 900     this->assign(IL);
 901     return *this;
 902   }
 903 };
 904
 905 template <typename T, unsigned N>
 906 inline size_t capacity_in_bytes(const SmallVector<T, N> &X) {
 907   return X.capacity_in_bytes();
 908 }
 909
 910 } // end namespace llvm
 911
 912 namespace std {
 913
 914   /// Implement std::swap in terms of SmallVector swap.
 915   template<typename T>
 916   inline void
 917   swap(llvm::SmallVectorImpl<T> &LHS, llvm::SmallVectorImpl<T> &RHS) {
 918     LHS.swap(RHS);
 919   }
 920
 921   /// Implement std::swap in terms of SmallVector swap.
 922   template<typename T, unsigned N>
 923   inline void
 924   swap(llvm::SmallVector<T, N> &LHS, llvm::SmallVector<T, N> &RHS) {
 925     LHS.swap(RHS);
 926   }
 927
 928 } // end namespace std
 929
 930 #endif // LLVM_ADT_SMALLVECTOR_H