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/// \file
10/// This file defines the SmallVector class.
11///
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ADT_SMALLVECTOR_H
15#define LLVM_ADT_SMALLVECTOR_H
16
17#include "llvm/Support/Compiler.h"
18#include "llvm/Support/type_traits.h"
19#include <algorithm>
20#include <cassert>
21#include <cstddef>
22#include <cstdlib>
23#include <cstring>
24#include <functional>
25#include <initializer_list>
26#include <iterator>
27#include <limits>
28#include <memory>
29#include <new>
30#include <type_traits>
31#include <utility>
32
33namespace llvm {
34
35template <typename T> class ArrayRef;
36
37template <typename IteratorT> class iterator_range;
38
39template <class Iterator>
40using EnableIfConvertibleToInputIterator = std::enable_if_t<std::is_convertible<
41    typename std::iterator_traits<Iterator>::iterator_category,
42    std::input_iterator_tag>::value>;
43
44/// This is all the stuff common to all SmallVectors.
45///
46/// The template parameter specifies the type which should be used to hold the
47/// Size and Capacity of the SmallVector, so it can be adjusted.
48/// Using 32 bit size is desirable to shrink the size of the SmallVector.
49/// Using 64 bit size is desirable for cases like SmallVector<char>, where a
50/// 32 bit size would limit the vector to ~4GB. SmallVectors are used for
51/// buffering bitcode output - which can exceed 4GB.
52template <class Size_T> class SmallVectorBase {
53protected:
54  void *BeginX;
55  Size_T Size = 0, Capacity;
56
57  /// The maximum value of the Size_T used.
58  static constexpr size_t SizeTypeMax() {
59    return std::numeric_limits<Size_T>::max();
60  }
61
62  SmallVectorBase() = delete;
63  SmallVectorBase(void *FirstEl, size_t TotalCapacity)
64      : BeginX(FirstEl), Capacity(static_cast<Size_T>(TotalCapacity)) {}
65
66  /// This is a helper for \a grow() that's out of line to reduce code
67  /// duplication.  This function will report a fatal error if it can't grow at
68  /// least to \p MinSize.
69  void *mallocForGrow(void *FirstEl, size_t MinSize, size_t TSize,
70                      size_t &NewCapacity);
71
72  /// This is an implementation of the grow() method which only works
73  /// on POD-like data types and is out of line to reduce code duplication.
74  /// This function will report a fatal error if it cannot increase capacity.
75  void grow_pod(void *FirstEl, size_t MinSize, size_t TSize);
76
77  /// If vector was first created with capacity 0, getFirstEl() points to the
78  /// memory right after, an area unallocated. If a subsequent allocation,
79  /// that grows the vector, happens to return the same pointer as getFirstEl(),
80  /// get a new allocation, otherwise isSmall() will falsely return that no
81  /// allocation was done (true) and the memory will not be freed in the
82  /// destructor. If a VSize is given (vector size), also copy that many
83  /// elements to the new allocation - used if realloca fails to increase
84  /// space, and happens to allocate precisely at BeginX.
85  /// This is unlikely to be called often, but resolves a memory leak when the
86  /// situation does occur.
87  void *replaceAllocation(void *NewElts, size_t TSize, size_t NewCapacity,
88                          size_t VSize = 0);
89
90public:
91  size_t size() const { return Size; }
92  size_t capacity() const { return Capacity; }
93
94  [[nodiscard]] bool empty() const { return !Size; }
95
96protected:
97  /// Set the array size to \p N, which the current array must have enough
98  /// capacity for.
99  ///
100  /// This does not construct or destroy any elements in the vector.
101  void set_size(size_t N) {
102    assert(N <= capacity()); // implies no overflow in assignment
103    Size = static_cast<Size_T>(N);
104  }
105
106  /// Set the array data pointer to \p Begin and capacity to \p N.
107  ///
108  /// This does not construct or destroy any elements in the vector.
109  //  This does not clean up any existing allocation.
110  void set_allocation_range(void *Begin, size_t N) {
111    assert(N <= SizeTypeMax());
112    BeginX = Begin;
113    Capacity = static_cast<Size_T>(N);
114  }
115};
116
117template <class T>
118using SmallVectorSizeType =
119    std::conditional_t<sizeof(T) < 4 && sizeof(void *) >= 8, uint64_t,
120                       uint32_t>;
121
122/// Figure out the offset of the first element.
123template <class T, typename = void> struct SmallVectorAlignmentAndSize {
124  alignas(SmallVectorBase<SmallVectorSizeType<T>>) char Base[sizeof(
125      SmallVectorBase<SmallVectorSizeType<T>>)];
126  alignas(T) char FirstEl[sizeof(T)];
127};
128
129/// This is the part of SmallVectorTemplateBase which does not depend on whether
130/// the type T is a POD. The extra dummy template argument is used by ArrayRef
131/// to avoid unnecessarily requiring T to be complete.
132template <typename T, typename = void>
133class SmallVectorTemplateCommon
134    : public SmallVectorBase<SmallVectorSizeType<T>> {
135  using Base = SmallVectorBase<SmallVectorSizeType<T>>;
136
137protected:
138  /// Find the address of the first element.  For this pointer math to be valid
139  /// with small-size of 0 for T with lots of alignment, it's important that
140  /// SmallVectorStorage is properly-aligned even for small-size of 0.
141  void *getFirstEl() const {
142    return const_cast<void *>(reinterpret_cast<const void *>(
143        reinterpret_cast<const char *>(this) +
144        offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)));
145  }
146  // Space after 'FirstEl' is clobbered, do not add any instance vars after it.
147
148  SmallVectorTemplateCommon(size_t Size) : Base(getFirstEl(), Size) {}
149
150  void grow_pod(size_t MinSize, size_t TSize) {
151    Base::grow_pod(getFirstEl(), MinSize, TSize);
152  }
153
154  /// Return true if this is a smallvector which has not had dynamic
155  /// memory allocated for it.
156  bool isSmall() const { return this->BeginX == getFirstEl(); }
157
158  /// Put this vector in a state of being small.
159  void resetToSmall() {
160    this->BeginX = getFirstEl();
161    this->Size = this->Capacity = 0; // FIXME: Setting Capacity to 0 is suspect.
162  }
163
164  /// Return true if V is an internal reference to the given range.
165  bool isReferenceToRange(const void *V, const void *First, const void *Last) const {
166    // Use std::less to avoid UB.
167    std::less<> LessThan;
168    return !LessThan(V, First) && LessThan(V, Last);
169  }
170
171  /// Return true if V is an internal reference to this vector.
172  bool isReferenceToStorage(const void *V) const {
173    return isReferenceToRange(V, this->begin(), this->end());
174  }
175
176  /// Return true if First and Last form a valid (possibly empty) range in this
177  /// vector's storage.
178  bool isRangeInStorage(const void *First, const void *Last) const {
179    // Use std::less to avoid UB.
180    std::less<> LessThan;
181    return !LessThan(First, this->begin()) && !LessThan(Last, First) &&
182           !LessThan(this->end(), Last);
183  }
184
185  /// Return true unless Elt will be invalidated by resizing the vector to
186  /// NewSize.
187  bool isSafeToReferenceAfterResize(const void *Elt, size_t NewSize) {
188    // Past the end.
189    if (LLVM_LIKELY(!isReferenceToStorage(Elt)))
190      return true;
191
192    // Return false if Elt will be destroyed by shrinking.
193    if (NewSize <= this->size())
194      return Elt < this->begin() + NewSize;
195
196    // Return false if we need to grow.
197    return NewSize <= this->capacity();
198  }
199
200  /// Check whether Elt will be invalidated by resizing the vector to NewSize.
201  void assertSafeToReferenceAfterResize(const void *Elt, size_t NewSize) {
202    assert(isSafeToReferenceAfterResize(Elt, NewSize) &&
203           "Attempting to reference an element of the vector in an operation "
204           "that invalidates it");
205  }
206
207  /// Check whether Elt will be invalidated by increasing the size of the
208  /// vector by N.
209  void assertSafeToAdd(const void *Elt, size_t N = 1) {
210    this->assertSafeToReferenceAfterResize(Elt, this->size() + N);
211  }
212
213  /// Check whether any part of the range will be invalidated by clearing.
214  void assertSafeToReferenceAfterClear(const T *From, const T *To) {
215    if (From == To)
216      return;
217    this->assertSafeToReferenceAfterResize(From, 0);
218    this->assertSafeToReferenceAfterResize(To - 1, 0);
219  }
220  template <
221      class ItTy,
222      std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value,
223                       bool> = false>
224  void assertSafeToReferenceAfterClear(ItTy, ItTy) {}
225
226  /// Check whether any part of the range will be invalidated by growing.
227  void assertSafeToAddRange(const T *From, const T *To) {
228    if (From == To)
229      return;
230    this->assertSafeToAdd(From, To - From);
231    this->assertSafeToAdd(To - 1, To - From);
232  }
233  template <
234      class ItTy,
235      std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value,
236                       bool> = false>
237  void assertSafeToAddRange(ItTy, ItTy) {}
238
239  /// Reserve enough space to add one element, and return the updated element
240  /// pointer in case it was a reference to the storage.
241  template <class U>
242  static const T *reserveForParamAndGetAddressImpl(U *This, const T &Elt,
243                                                   size_t N) {
244    size_t NewSize = This->size() + N;
245    if (LLVM_LIKELY(NewSize <= This->capacity()))
246      return &Elt;
247
248    bool ReferencesStorage = false;
249    int64_t Index = -1;
250    if (!U::TakesParamByValue) {
251      if (LLVM_UNLIKELY(This->isReferenceToStorage(&Elt))) {
252        ReferencesStorage = true;
253        Index = &Elt - This->begin();
254      }
255    }
256    This->grow(NewSize);
257    return ReferencesStorage ? This->begin() + Index : &Elt;
258  }
259
260public:
261  using size_type = size_t;
262  using difference_type = ptrdiff_t;
263  using value_type = T;
264  using iterator = T *;
265  using const_iterator = const T *;
266
267  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
268  using reverse_iterator = std::reverse_iterator<iterator>;
269
270  using reference = T &;
271  using const_reference = const T &;
272  using pointer = T *;
273  using const_pointer = const T *;
274
275  using Base::capacity;
276  using Base::empty;
277  using Base::size;
278
279  // forward iterator creation methods.
280  iterator begin() { return (iterator)this->BeginX; }
281  const_iterator begin() const { return (const_iterator)this->BeginX; }
282  iterator end() { return begin() + size(); }
283  const_iterator end() const { return begin() + size(); }
284
285  // reverse iterator creation methods.
286  reverse_iterator rbegin()            { return reverse_iterator(end()); }
287  const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
288  reverse_iterator rend()              { return reverse_iterator(begin()); }
289  const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
290
291  size_type size_in_bytes() const { return size() * sizeof(T); }
292  size_type max_size() const {
293    return std::min(this->SizeTypeMax(), size_type(-1) / sizeof(T));
294  }
295
296  size_t capacity_in_bytes() const { return capacity() * sizeof(T); }
297
298  /// Return a pointer to the vector's buffer, even if empty().
299  pointer data() { return pointer(begin()); }
300  /// Return a pointer to the vector's buffer, even if empty().
301  const_pointer data() const { return const_pointer(begin()); }
302
303  reference operator[](size_type idx) {
304    assert(idx < size());
305    return begin()[idx];
306  }
307  const_reference operator[](size_type idx) const {
308    assert(idx < size());
309    return begin()[idx];
310  }
311
312  reference front() {
313    assert(!empty());
314    return begin()[0];
315  }
316  const_reference front() const {
317    assert(!empty());
318    return begin()[0];
319  }
320
321  reference back() {
322    assert(!empty());
323    return end()[-1];
324  }
325  const_reference back() const {
326    assert(!empty());
327    return end()[-1];
328  }
329};
330
331/// SmallVectorTemplateBase<TriviallyCopyable = false> - This is where we put
332/// method implementations that are designed to work with non-trivial T's.
333///
334/// We approximate is_trivially_copyable with trivial move/copy construction and
335/// trivial destruction. While the standard doesn't specify that you're allowed
336/// copy these types with memcpy, there is no way for the type to observe this.
337/// This catches the important case of std::pair<POD, POD>, which is not
338/// trivially assignable.
339template <typename T, bool = (std::is_trivially_copy_constructible<T>::value) &&
340                             (std::is_trivially_move_constructible<T>::value) &&
341                             std::is_trivially_destructible<T>::value>
342class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
343  friend class SmallVectorTemplateCommon<T>;
344
345protected:
346  static constexpr bool TakesParamByValue = false;
347  using ValueParamT = const T &;
348
349  SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
350
351  static void destroy_range(T *S, T *E) {
352    while (S != E) {
353      --E;
354      E->~T();
355    }
356  }
357
358  /// Move the range [I, E) into the uninitialized memory starting with "Dest",
359  /// constructing elements as needed.
360  template<typename It1, typename It2>
361  static void uninitialized_move(It1 I, It1 E, It2 Dest) {
362    std::uninitialized_move(I, E, Dest);
363  }
364
365  /// Copy the range [I, E) onto the uninitialized memory starting with "Dest",
366  /// constructing elements as needed.
367  template<typename It1, typename It2>
368  static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
369    std::uninitialized_copy(I, E, Dest);
370  }
371
372  /// Grow the allocated memory (without initializing new elements), doubling
373  /// the size of the allocated memory. Guarantees space for at least one more
374  /// element, or MinSize more elements if specified.
375  void grow(size_t MinSize = 0);
376
377  /// Create a new allocation big enough for \p MinSize and pass back its size
378  /// in \p NewCapacity. This is the first section of \a grow().
379  T *mallocForGrow(size_t MinSize, size_t &NewCapacity);
380
381  /// Move existing elements over to the new allocation \p NewElts, the middle
382  /// section of \a grow().
383  void moveElementsForGrow(T *NewElts);
384
385  /// Transfer ownership of the allocation, finishing up \a grow().
386  void takeAllocationForGrow(T *NewElts, size_t NewCapacity);
387
388  /// Reserve enough space to add one element, and return the updated element
389  /// pointer in case it was a reference to the storage.
390  const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) {
391    return this->reserveForParamAndGetAddressImpl(this, Elt, N);
392  }
393
394  /// Reserve enough space to add one element, and return the updated element
395  /// pointer in case it was a reference to the storage.
396  T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) {
397    return const_cast<T *>(
398        this->reserveForParamAndGetAddressImpl(this, Elt, N));
399  }
400
401  static T &&forward_value_param(T &&V) { return std::move(V); }
402  static const T &forward_value_param(const T &V) { return V; }
403
404  void growAndAssign(size_t NumElts, const T &Elt) {
405    // Grow manually in case Elt is an internal reference.
406    size_t NewCapacity;
407    T *NewElts = mallocForGrow(NumElts, NewCapacity);
408    std::uninitialized_fill_n(NewElts, NumElts, Elt);
409    this->destroy_range(this->begin(), this->end());
410    takeAllocationForGrow(NewElts, NewCapacity);
411    this->set_size(NumElts);
412  }
413
414  template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) {
415    // Grow manually in case one of Args is an internal reference.
416    size_t NewCapacity;
417    T *NewElts = mallocForGrow(0, NewCapacity);
418    ::new ((void *)(NewElts + this->size())) T(std::forward<ArgTypes>(Args)...);
419    moveElementsForGrow(NewElts);
420    takeAllocationForGrow(NewElts, NewCapacity);
421    this->set_size(this->size() + 1);
422    return this->back();
423  }
424
425public:
426  void push_back(const T &Elt) {
427    const T *EltPtr = reserveForParamAndGetAddress(Elt);
428    ::new ((void *)this->end()) T(*EltPtr);
429    this->set_size(this->size() + 1);
430  }
431
432  void push_back(T &&Elt) {
433    T *EltPtr = reserveForParamAndGetAddress(Elt);
434    ::new ((void *)this->end()) T(::std::move(*EltPtr));
435    this->set_size(this->size() + 1);
436  }
437
438  void pop_back() {
439    this->set_size(this->size() - 1);
440    this->end()->~T();
441  }
442};
443
444// Define this out-of-line to dissuade the C++ compiler from inlining it.
445template <typename T, bool TriviallyCopyable>
446void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
447  size_t NewCapacity;
448  T *NewElts = mallocForGrow(MinSize, NewCapacity);
449  moveElementsForGrow(NewElts);
450  takeAllocationForGrow(NewElts, NewCapacity);
451}
452
453template <typename T, bool TriviallyCopyable>
454T *SmallVectorTemplateBase<T, TriviallyCopyable>::mallocForGrow(
455    size_t MinSize, size_t &NewCapacity) {
456  return static_cast<T *>(
457      SmallVectorBase<SmallVectorSizeType<T>>::mallocForGrow(
458          this->getFirstEl(), MinSize, sizeof(T), NewCapacity));
459}
460
461// Define this out-of-line to dissuade the C++ compiler from inlining it.
462template <typename T, bool TriviallyCopyable>
463void SmallVectorTemplateBase<T, TriviallyCopyable>::moveElementsForGrow(
464    T *NewElts) {
465  // Move the elements over.
466  this->uninitialized_move(this->begin(), this->end(), NewElts);
467
468  // Destroy the original elements.
469  destroy_range(this->begin(), this->end());
470}
471
472// Define this out-of-line to dissuade the C++ compiler from inlining it.
473template <typename T, bool TriviallyCopyable>
474void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow(
475    T *NewElts, size_t NewCapacity) {
476  // If this wasn't grown from the inline copy, deallocate the old space.
477  if (!this->isSmall())
478    free(this->begin());
479
480  this->set_allocation_range(NewElts, NewCapacity);
481}
482
483/// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put
484/// method implementations that are designed to work with trivially copyable
485/// T's. This allows using memcpy in place of copy/move construction and
486/// skipping destruction.
487template <typename T>
488class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
489  friend class SmallVectorTemplateCommon<T>;
490
491protected:
492  /// True if it's cheap enough to take parameters by value. Doing so avoids
493  /// overhead related to mitigations for reference invalidation.
494  static constexpr bool TakesParamByValue = sizeof(T) <= 2 * sizeof(void *);
495
496  /// Either const T& or T, depending on whether it's cheap enough to take
497  /// parameters by value.
498  using ValueParamT = std::conditional_t<TakesParamByValue, T, const T &>;
499
500  SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
501
502  // No need to do a destroy loop for POD's.
503  static void destroy_range(T *, T *) {}
504
505  /// Move the range [I, E) onto the uninitialized memory
506  /// starting with "Dest", constructing elements into it as needed.
507  template<typename It1, typename It2>
508  static void uninitialized_move(It1 I, It1 E, It2 Dest) {
509    // Just do a copy.
510    uninitialized_copy(I, E, Dest);
511  }
512
513  /// Copy the range [I, E) onto the uninitialized memory
514  /// starting with "Dest", constructing elements into it as needed.
515  template<typename It1, typename It2>
516  static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
517    // Arbitrary iterator types; just use the basic implementation.
518    std::uninitialized_copy(I, E, Dest);
519  }
520
521  /// Copy the range [I, E) onto the uninitialized memory
522  /// starting with "Dest", constructing elements into it as needed.
523  template <typename T1, typename T2>
524  static void uninitialized_copy(
525      T1 *I, T1 *E, T2 *Dest,
526      std::enable_if_t<std::is_same<std::remove_const_t<T1>, T2>::value> * =
527          nullptr) {
528    // Use memcpy for PODs iterated by pointers (which includes SmallVector
529    // iterators): std::uninitialized_copy optimizes to memmove, but we can
530    // use memcpy here. Note that I and E are iterators and thus might be
531    // invalid for memcpy if they are equal.
532    if (I != E)
533      memcpy(reinterpret_cast<void *>(Dest), I, (E - I) * sizeof(T));
534  }
535
536  /// Double the size of the allocated memory, guaranteeing space for at
537  /// least one more element or MinSize if specified.
538  void grow(size_t MinSize = 0) { this->grow_pod(MinSize, sizeof(T)); }
539
540  /// Reserve enough space to add one element, and return the updated element
541  /// pointer in case it was a reference to the storage.
542  const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) {
543    return this->reserveForParamAndGetAddressImpl(this, Elt, N);
544  }
545
546  /// Reserve enough space to add one element, and return the updated element
547  /// pointer in case it was a reference to the storage.
548  T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) {
549    return const_cast<T *>(
550        this->reserveForParamAndGetAddressImpl(this, Elt, N));
551  }
552
553  /// Copy \p V or return a reference, depending on \a ValueParamT.
554  static ValueParamT forward_value_param(ValueParamT V) { return V; }
555
556  void growAndAssign(size_t NumElts, T Elt) {
557    // Elt has been copied in case it's an internal reference, side-stepping
558    // reference invalidation problems without losing the realloc optimization.
559    this->set_size(0);
560    this->grow(NumElts);
561    std::uninitialized_fill_n(this->begin(), NumElts, Elt);
562    this->set_size(NumElts);
563  }
564
565  template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) {
566    // Use push_back with a copy in case Args has an internal reference,
567    // side-stepping reference invalidation problems without losing the realloc
568    // optimization.
569    push_back(T(std::forward<ArgTypes>(Args)...));
570    return this->back();
571  }
572
573public:
574  void push_back(ValueParamT Elt) {
575    const T *EltPtr = reserveForParamAndGetAddress(Elt);
576    memcpy(reinterpret_cast<void *>(this->end()), EltPtr, sizeof(T));
577    this->set_size(this->size() + 1);
578  }
579
580  void pop_back() { this->set_size(this->size() - 1); }
581};
582
583/// This class consists of common code factored out of the SmallVector class to
584/// reduce code duplication based on the SmallVector 'N' template parameter.
585template <typename T>
586class SmallVectorImpl : public SmallVectorTemplateBase<T> {
587  using SuperClass = SmallVectorTemplateBase<T>;
588
589public:
590  using iterator = typename SuperClass::iterator;
591  using const_iterator = typename SuperClass::const_iterator;
592  using reference = typename SuperClass::reference;
593  using size_type = typename SuperClass::size_type;
594
595protected:
596  using SmallVectorTemplateBase<T>::TakesParamByValue;
597  using ValueParamT = typename SuperClass::ValueParamT;
598
599  // Default ctor - Initialize to empty.
600  explicit SmallVectorImpl(unsigned N)
601      : SmallVectorTemplateBase<T>(N) {}
602
603  void assignRemote(SmallVectorImpl &&RHS) {
604    this->destroy_range(this->begin(), this->end());
605    if (!this->isSmall())
606      free(this->begin());
607    this->BeginX = RHS.BeginX;
608    this->Size = RHS.Size;
609    this->Capacity = RHS.Capacity;
610    RHS.resetToSmall();
611  }
612
613  ~SmallVectorImpl() {
614    // Subclass has already destructed this vector's elements.
615    // If this wasn't grown from the inline copy, deallocate the old space.
616    if (!this->isSmall())
617      free(this->begin());
618  }
619
620public:
621  SmallVectorImpl(const SmallVectorImpl &) = delete;
622
623  void clear() {
624    this->destroy_range(this->begin(), this->end());
625    this->Size = 0;
626  }
627
628private:
629  // Make set_size() private to avoid misuse in subclasses.
630  using SuperClass::set_size;
631
632  template <bool ForOverwrite> void resizeImpl(size_type N) {
633    if (N == this->size())
634      return;
635
636    if (N < this->size()) {
637      this->truncate(N);
638      return;
639    }
640
641    this->reserve(N);
642    for (auto I = this->end(), E = this->begin() + N; I != E; ++I)
643      if (ForOverwrite)
644        new (&*I) T;
645      else
646        new (&*I) T();
647    this->set_size(N);
648  }
649
650public:
651  void resize(size_type N) { resizeImpl<false>(N); }
652
653  /// Like resize, but \ref T is POD, the new values won't be initialized.
654  void resize_for_overwrite(size_type N) { resizeImpl<true>(N); }
655
656  /// Like resize, but requires that \p N is less than \a size().
657  void truncate(size_type N) {
658    assert(this->size() >= N && "Cannot increase size with truncate");
659    this->destroy_range(this->begin() + N, this->end());
660    this->set_size(N);
661  }
662
663  void resize(size_type N, ValueParamT NV) {
664    if (N == this->size())
665      return;
666
667    if (N < this->size()) {
668      this->truncate(N);
669      return;
670    }
671
672    // N > this->size(). Defer to append.
673    this->append(N - this->size(), NV);
674  }
675
676  void reserve(size_type N) {
677    if (this->capacity() < N)
678      this->grow(N);
679  }
680
681  void pop_back_n(size_type NumItems) {
682    assert(this->size() >= NumItems);
683    truncate(this->size() - NumItems);
684  }
685
686  [[nodiscard]] T pop_back_val() {
687    T Result = ::std::move(this->back());
688    this->pop_back();
689    return Result;
690  }
691
692  void swap(SmallVectorImpl &RHS);
693
694  /// Add the specified range to the end of the SmallVector.
695  template <typename ItTy, typename = EnableIfConvertibleToInputIterator<ItTy>>
696  void append(ItTy in_start, ItTy in_end) {
697    this->assertSafeToAddRange(in_start, in_end);
698    size_type NumInputs = std::distance(in_start, in_end);
699    this->reserve(this->size() + NumInputs);
700    this->uninitialized_copy(in_start, in_end, this->end());
701    this->set_size(this->size() + NumInputs);
702  }
703
704  /// Append \p NumInputs copies of \p Elt to the end.
705  void append(size_type NumInputs, ValueParamT Elt) {
706    const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumInputs);
707    std::uninitialized_fill_n(this->end(), NumInputs, *EltPtr);
708    this->set_size(this->size() + NumInputs);
709  }
710
711  void append(std::initializer_list<T> IL) {
712    append(IL.begin(), IL.end());
713  }
714
715  void append(const SmallVectorImpl &RHS) { append(RHS.begin(), RHS.end()); }
716
717  void assign(size_type NumElts, ValueParamT Elt) {
718    // Note that Elt could be an internal reference.
719    if (NumElts > this->capacity()) {
720      this->growAndAssign(NumElts, Elt);
721      return;
722    }
723
724    // Assign over existing elements.
725    std::fill_n(this->begin(), std::min(NumElts, this->size()), Elt);
726    if (NumElts > this->size())
727      std::uninitialized_fill_n(this->end(), NumElts - this->size(), Elt);
728    else if (NumElts < this->size())
729      this->destroy_range(this->begin() + NumElts, this->end());
730    this->set_size(NumElts);
731  }
732
733  // FIXME: Consider assigning over existing elements, rather than clearing &
734  // re-initializing them - for all assign(...) variants.
735
736  template <typename ItTy, typename = EnableIfConvertibleToInputIterator<ItTy>>
737  void assign(ItTy in_start, ItTy in_end) {
738    this->assertSafeToReferenceAfterClear(in_start, in_end);
739    clear();
740    append(in_start, in_end);
741  }
742
743  void assign(std::initializer_list<T> IL) {
744    clear();
745    append(IL);
746  }
747
748  void assign(const SmallVectorImpl &RHS) { assign(RHS.begin(), RHS.end()); }
749
750  iterator erase(const_iterator CI) {
751    // Just cast away constness because this is a non-const member function.
752    iterator I = const_cast<iterator>(CI);
753
754    assert(this->isReferenceToStorage(CI) && "Iterator to erase is out of bounds.");
755
756    iterator N = I;
757    // Shift all elts down one.
758    std::move(I+1, this->end(), I);
759    // Drop the last elt.
760    this->pop_back();
761    return(N);
762  }
763
764  iterator erase(const_iterator CS, const_iterator CE) {
765    // Just cast away constness because this is a non-const member function.
766    iterator S = const_cast<iterator>(CS);
767    iterator E = const_cast<iterator>(CE);
768
769    assert(this->isRangeInStorage(S, E) && "Range to erase is out of bounds.");
770
771    iterator N = S;
772    // Shift all elts down.
773    iterator I = std::move(E, this->end(), S);
774    // Drop the last elts.
775    this->destroy_range(I, this->end());
776    this->set_size(I - this->begin());
777    return(N);
778  }
779
780private:
781  template <class ArgType> iterator insert_one_impl(iterator I, ArgType &&Elt) {
782    // Callers ensure that ArgType is derived from T.
783    static_assert(
784        std::is_same<std::remove_const_t<std::remove_reference_t<ArgType>>,
785                     T>::value,
786        "ArgType must be derived from T!");
787
788    if (I == this->end()) {  // Important special case for empty vector.
789      this->push_back(::std::forward<ArgType>(Elt));
790      return this->end()-1;
791    }
792
793    assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.");
794
795    // Grow if necessary.
796    size_t Index = I - this->begin();
797    std::remove_reference_t<ArgType> *EltPtr =
798        this->reserveForParamAndGetAddress(Elt);
799    I = this->begin() + Index;
800
801    ::new ((void*) this->end()) T(::std::move(this->back()));
802    // Push everything else over.
803    std::move_backward(I, this->end()-1, this->end());
804    this->set_size(this->size() + 1);
805
806    // If we just moved the element we're inserting, be sure to update
807    // the reference (never happens if TakesParamByValue).
808    static_assert(!TakesParamByValue || std::is_same<ArgType, T>::value,
809                  "ArgType must be 'T' when taking by value!");
810    if (!TakesParamByValue && this->isReferenceToRange(EltPtr, I, this->end()))
811      ++EltPtr;
812
813    *I = ::std::forward<ArgType>(*EltPtr);
814    return I;
815  }
816
817public:
818  iterator insert(iterator I, T &&Elt) {
819    return insert_one_impl(I, this->forward_value_param(std::move(Elt)));
820  }
821
822  iterator insert(iterator I, const T &Elt) {
823    return insert_one_impl(I, this->forward_value_param(Elt));
824  }
825
826  iterator insert(iterator I, size_type NumToInsert, ValueParamT Elt) {
827    // Convert iterator to elt# to avoid invalidating iterator when we reserve()
828    size_t InsertElt = I - this->begin();
829
830    if (I == this->end()) {  // Important special case for empty vector.
831      append(NumToInsert, Elt);
832      return this->begin()+InsertElt;
833    }
834
835    assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.");
836
837    // Ensure there is enough space, and get the (maybe updated) address of
838    // Elt.
839    const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumToInsert);
840
841    // Uninvalidate the iterator.
842    I = this->begin()+InsertElt;
843
844    // If there are more elements between the insertion point and the end of the
845    // range than there are being inserted, we can use a simple approach to
846    // insertion.  Since we already reserved space, we know that this won't
847    // reallocate the vector.
848    if (size_t(this->end()-I) >= NumToInsert) {
849      T *OldEnd = this->end();
850      append(std::move_iterator<iterator>(this->end() - NumToInsert),
851             std::move_iterator<iterator>(this->end()));
852
853      // Copy the existing elements that get replaced.
854      std::move_backward(I, OldEnd-NumToInsert, OldEnd);
855
856      // If we just moved the element we're inserting, be sure to update
857      // the reference (never happens if TakesParamByValue).
858      if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
859        EltPtr += NumToInsert;
860
861      std::fill_n(I, NumToInsert, *EltPtr);
862      return I;
863    }
864
865    // Otherwise, we're inserting more elements than exist already, and we're
866    // not inserting at the end.
867
868    // Move over the elements that we're about to overwrite.
869    T *OldEnd = this->end();
870    this->set_size(this->size() + NumToInsert);
871    size_t NumOverwritten = OldEnd-I;
872    this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
873
874    // If we just moved the element we're inserting, be sure to update
875    // the reference (never happens if TakesParamByValue).
876    if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
877      EltPtr += NumToInsert;
878
879    // Replace the overwritten part.
880    std::fill_n(I, NumOverwritten, *EltPtr);
881
882    // Insert the non-overwritten middle part.
883    std::uninitialized_fill_n(OldEnd, NumToInsert - NumOverwritten, *EltPtr);
884    return I;
885  }
886
887  template <typename ItTy, typename = EnableIfConvertibleToInputIterator<ItTy>>
888  iterator insert(iterator I, ItTy From, ItTy To) {
889    // Convert iterator to elt# to avoid invalidating iterator when we reserve()
890    size_t InsertElt = I - this->begin();
891
892    if (I == this->end()) {  // Important special case for empty vector.
893      append(From, To);
894      return this->begin()+InsertElt;
895    }
896
897    assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.");
898
899    // Check that the reserve that follows doesn't invalidate the iterators.
900    this->assertSafeToAddRange(From, To);
901
902    size_t NumToInsert = std::distance(From, To);
903
904    // Ensure there is enough space.
905    reserve(this->size() + NumToInsert);
906
907    // Uninvalidate the iterator.
908    I = this->begin()+InsertElt;
909
910    // If there are more elements between the insertion point and the end of the
911    // range than there are being inserted, we can use a simple approach to
912    // insertion.  Since we already reserved space, we know that this won't
913    // reallocate the vector.
914    if (size_t(this->end()-I) >= NumToInsert) {
915      T *OldEnd = this->end();
916      append(std::move_iterator<iterator>(this->end() - NumToInsert),
917             std::move_iterator<iterator>(this->end()));
918
919      // Copy the existing elements that get replaced.
920      std::move_backward(I, OldEnd-NumToInsert, OldEnd);
921
922      std::copy(From, To, I);
923      return I;
924    }
925
926    // Otherwise, we're inserting more elements than exist already, and we're
927    // not inserting at the end.
928
929    // Move over the elements that we're about to overwrite.
930    T *OldEnd = this->end();
931    this->set_size(this->size() + NumToInsert);
932    size_t NumOverwritten = OldEnd-I;
933    this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
934
935    // Replace the overwritten part.
936    for (T *J = I; NumOverwritten > 0; --NumOverwritten) {
937      *J = *From;
938      ++J; ++From;
939    }
940
941    // Insert the non-overwritten middle part.
942    this->uninitialized_copy(From, To, OldEnd);
943    return I;
944  }
945
946  void insert(iterator I, std::initializer_list<T> IL) {
947    insert(I, IL.begin(), IL.end());
948  }
949
950  template <typename... ArgTypes> reference emplace_back(ArgTypes &&... Args) {
951    if (LLVM_UNLIKELY(this->size() >= this->capacity()))
952      return this->growAndEmplaceBack(std::forward<ArgTypes>(Args)...);
953
954    ::new ((void *)this->end()) T(std::forward<ArgTypes>(Args)...);
955    this->set_size(this->size() + 1);
956    return this->back();
957  }
958
959  SmallVectorImpl &operator=(const SmallVectorImpl &RHS);
960
961  SmallVectorImpl &operator=(SmallVectorImpl &&RHS);
962
963  bool operator==(const SmallVectorImpl &RHS) const {
964    if (this->size() != RHS.size()) return false;
965    return std::equal(this->begin(), this->end(), RHS.begin());
966  }
967  bool operator!=(const SmallVectorImpl &RHS) const {
968    return !(*this == RHS);
969  }
970
971  bool operator<(const SmallVectorImpl &RHS) const {
972    return std::lexicographical_compare(this->begin(), this->end(),
973                                        RHS.begin(), RHS.end());
974  }
975  bool operator>(const SmallVectorImpl &RHS) const { return RHS < *this; }
976  bool operator<=(const SmallVectorImpl &RHS) const { return !(*this > RHS); }
977  bool operator>=(const SmallVectorImpl &RHS) const { return !(*this < RHS); }
978};
979
980template <typename T>
981void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
982  if (this == &RHS) return;
983
984  // We can only avoid copying elements if neither vector is small.
985  if (!this->isSmall() && !RHS.isSmall()) {
986    std::swap(this->BeginX, RHS.BeginX);
987    std::swap(this->Size, RHS.Size);
988    std::swap(this->Capacity, RHS.Capacity);
989    return;
990  }
991  this->reserve(RHS.size());
992  RHS.reserve(this->size());
993
994  // Swap the shared elements.
995  size_t NumShared = this->size();
996  if (NumShared > RHS.size()) NumShared = RHS.size();
997  for (size_type i = 0; i != NumShared; ++i)
998    std::swap((*this)[i], RHS[i]);
999
1000  // Copy over the extra elts.
1001  if (this->size() > RHS.size()) {
1002    size_t EltDiff = this->size() - RHS.size();
1003    this->uninitialized_copy(this->begin()+NumShared, this->end(), RHS.end());
1004    RHS.set_size(RHS.size() + EltDiff);
1005    this->destroy_range(this->begin()+NumShared, this->end());
1006    this->set_size(NumShared);
1007  } else if (RHS.size() > this->size()) {
1008    size_t EltDiff = RHS.size() - this->size();
1009    this->uninitialized_copy(RHS.begin()+NumShared, RHS.end(), this->end());
1010    this->set_size(this->size() + EltDiff);
1011    this->destroy_range(RHS.begin()+NumShared, RHS.end());
1012    RHS.set_size(NumShared);
1013  }
1014}
1015
1016template <typename T>
1017SmallVectorImpl<T> &SmallVectorImpl<T>::
1018  operator=(const SmallVectorImpl<T> &RHS) {
1019  // Avoid self-assignment.
1020  if (this == &RHS) return *this;
1021
1022  // If we already have sufficient space, assign the common elements, then
1023  // destroy any excess.
1024  size_t RHSSize = RHS.size();
1025  size_t CurSize = this->size();
1026  if (CurSize >= RHSSize) {
1027    // Assign common elements.
1028    iterator NewEnd;
1029    if (RHSSize)
1030      NewEnd = std::copy(RHS.begin(), RHS.begin()+RHSSize, this->begin());
1031    else
1032      NewEnd = this->begin();
1033
1034    // Destroy excess elements.
1035    this->destroy_range(NewEnd, this->end());
1036
1037    // Trim.
1038    this->set_size(RHSSize);
1039    return *this;
1040  }
1041
1042  // If we have to grow to have enough elements, destroy the current elements.
1043  // This allows us to avoid copying them during the grow.
1044  // FIXME: don't do this if they're efficiently moveable.
1045  if (this->capacity() < RHSSize) {
1046    // Destroy current elements.
1047    this->clear();
1048    CurSize = 0;
1049    this->grow(RHSSize);
1050  } else if (CurSize) {
1051    // Otherwise, use assignment for the already-constructed elements.
1052    std::copy(RHS.begin(), RHS.begin()+CurSize, this->begin());
1053  }
1054
1055  // Copy construct the new elements in place.
1056  this->uninitialized_copy(RHS.begin()+CurSize, RHS.end(),
1057                           this->begin()+CurSize);
1058
1059  // Set end.
1060  this->set_size(RHSSize);
1061  return *this;
1062}
1063
1064template <typename T>
1065SmallVectorImpl<T> &SmallVectorImpl<T>::operator=(SmallVectorImpl<T> &&RHS) {
1066  // Avoid self-assignment.
1067  if (this == &RHS) return *this;
1068
1069  // If the RHS isn't small, clear this vector and then steal its buffer.
1070  if (!RHS.isSmall()) {
1071    this->assignRemote(std::move(RHS));
1072    return *this;
1073  }
1074
1075  // If we already have sufficient space, assign the common elements, then
1076  // destroy any excess.
1077  size_t RHSSize = RHS.size();
1078  size_t CurSize = this->size();
1079  if (CurSize >= RHSSize) {
1080    // Assign common elements.
1081    iterator NewEnd = this->begin();
1082    if (RHSSize)
1083      NewEnd = std::move(RHS.begin(), RHS.end(), NewEnd);
1084
1085    // Destroy excess elements and trim the bounds.
1086    this->destroy_range(NewEnd, this->end());
1087    this->set_size(RHSSize);
1088
1089    // Clear the RHS.
1090    RHS.clear();
1091
1092    return *this;
1093  }
1094
1095  // If we have to grow to have enough elements, destroy the current elements.
1096  // This allows us to avoid copying them during the grow.
1097  // FIXME: this may not actually make any sense if we can efficiently move
1098  // elements.
1099  if (this->capacity() < RHSSize) {
1100    // Destroy current elements.
1101    this->clear();
1102    CurSize = 0;
1103    this->grow(RHSSize);
1104  } else if (CurSize) {
1105    // Otherwise, use assignment for the already-constructed elements.
1106    std::move(RHS.begin(), RHS.begin()+CurSize, this->begin());
1107  }
1108
1109  // Move-construct the new elements in place.
1110  this->uninitialized_move(RHS.begin()+CurSize, RHS.end(),
1111                           this->begin()+CurSize);
1112
1113  // Set end.
1114  this->set_size(RHSSize);
1115
1116  RHS.clear();
1117  return *this;
1118}
1119
1120/// Storage for the SmallVector elements.  This is specialized for the N=0 case
1121/// to avoid allocating unnecessary storage.
1122template <typename T, unsigned N>
1123struct SmallVectorStorage {
1124  alignas(T) char InlineElts[N * sizeof(T)];
1125};
1126
1127/// We need the storage to be properly aligned even for small-size of 0 so that
1128/// the pointer math in \a SmallVectorTemplateCommon::getFirstEl() is
1129/// well-defined.
1130template <typename T> struct alignas(T) SmallVectorStorage<T, 0> {};
1131
1132/// Forward declaration of SmallVector so that
1133/// calculateSmallVectorDefaultInlinedElements can reference
1134/// `sizeof(SmallVector<T, 0>)`.
1135template <typename T, unsigned N> class LLVM_GSL_OWNER SmallVector;
1136
1137/// Helper class for calculating the default number of inline elements for
1138/// `SmallVector<T>`.
1139///
1140/// This should be migrated to a constexpr function when our minimum
1141/// compiler support is enough for multi-statement constexpr functions.
1142template <typename T> struct CalculateSmallVectorDefaultInlinedElements {
1143  // Parameter controlling the default number of inlined elements
1144  // for `SmallVector<T>`.
1145  //
1146  // The default number of inlined elements ensures that
1147  // 1. There is at least one inlined element.
1148  // 2. `sizeof(SmallVector<T>) <= kPreferredSmallVectorSizeof` unless
1149  // it contradicts 1.
1150  static constexpr size_t kPreferredSmallVectorSizeof = 64;
1151
1152  // static_assert that sizeof(T) is not "too big".
1153  //
1154  // Because our policy guarantees at least one inlined element, it is possible
1155  // for an arbitrarily large inlined element to allocate an arbitrarily large
1156  // amount of inline storage. We generally consider it an antipattern for a
1157  // SmallVector to allocate an excessive amount of inline storage, so we want
1158  // to call attention to these cases and make sure that users are making an
1159  // intentional decision if they request a lot of inline storage.
1160  //
1161  // We want this assertion to trigger in pathological cases, but otherwise
1162  // not be too easy to hit. To accomplish that, the cutoff is actually somewhat
1163  // larger than kPreferredSmallVectorSizeof (otherwise,
1164  // `SmallVector<SmallVector<T>>` would be one easy way to trip it, and that
1165  // pattern seems useful in practice).
1166  //
1167  // One wrinkle is that this assertion is in theory non-portable, since
1168  // sizeof(T) is in general platform-dependent. However, we don't expect this
1169  // to be much of an issue, because most LLVM development happens on 64-bit
1170  // hosts, and therefore sizeof(T) is expected to *decrease* when compiled for
1171  // 32-bit hosts, dodging the issue. The reverse situation, where development
1172  // happens on a 32-bit host and then fails due to sizeof(T) *increasing* on a
1173  // 64-bit host, is expected to be very rare.
1174  static_assert(
1175      sizeof(T) <= 256,
1176      "You are trying to use a default number of inlined elements for "
1177      "`SmallVector<T>` but `sizeof(T)` is really big! Please use an "
1178      "explicit number of inlined elements with `SmallVector<T, N>` to make "
1179      "sure you really want that much inline storage.");
1180
1181  // Discount the size of the header itself when calculating the maximum inline
1182  // bytes.
1183  static constexpr size_t PreferredInlineBytes =
1184      kPreferredSmallVectorSizeof - sizeof(SmallVector<T, 0>);
1185  static constexpr size_t NumElementsThatFit = PreferredInlineBytes / sizeof(T);
1186  static constexpr size_t value =
1187      NumElementsThatFit == 0 ? 1 : NumElementsThatFit;
1188};
1189
1190/// This is a 'vector' (really, a variable-sized array), optimized
1191/// for the case when the array is small.  It contains some number of elements
1192/// in-place, which allows it to avoid heap allocation when the actual number of
1193/// elements is below that threshold.  This allows normal "small" cases to be
1194/// fast without losing generality for large inputs.
1195///
1196/// \note
1197/// In the absence of a well-motivated choice for the number of inlined
1198/// elements \p N, it is recommended to use \c SmallVector<T> (that is,
1199/// omitting the \p N). This will choose a default number of inlined elements
1200/// reasonable for allocation on the stack (for example, trying to keep \c
1201/// sizeof(SmallVector<T>) around 64 bytes).
1202///
1203/// \warning This does not attempt to be exception safe.
1204///
1205/// \see https://llvm.org/docs/ProgrammersManual.html#llvm-adt-smallvector-h
1206template <typename T,
1207          unsigned N = CalculateSmallVectorDefaultInlinedElements<T>::value>
1208class LLVM_GSL_OWNER SmallVector : public SmallVectorImpl<T>,
1209                                   SmallVectorStorage<T, N> {
1210public:
1211  SmallVector() : SmallVectorImpl<T>(N) {}
1212
1213  ~SmallVector() {
1214    // Destroy the constructed elements in the vector.
1215    this->destroy_range(this->begin(), this->end());
1216  }
1217
1218  explicit SmallVector(size_t Size)
1219    : SmallVectorImpl<T>(N) {
1220    this->resize(Size);
1221  }
1222
1223  SmallVector(size_t Size, const T &Value)
1224    : SmallVectorImpl<T>(N) {
1225    this->assign(Size, Value);
1226  }
1227
1228  template <typename ItTy, typename = EnableIfConvertibleToInputIterator<ItTy>>
1229  SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) {
1230    this->append(S, E);
1231  }
1232
1233  template <typename RangeTy>
1234  explicit SmallVector(const iterator_range<RangeTy> &R)
1235      : SmallVectorImpl<T>(N) {
1236    this->append(R.begin(), R.end());
1237  }
1238
1239  SmallVector(std::initializer_list<T> IL) : SmallVectorImpl<T>(N) {
1240    this->append(IL);
1241  }
1242
1243  template <typename U,
1244            typename = std::enable_if_t<std::is_convertible<U, T>::value>>
1245  explicit SmallVector(ArrayRef<U> A) : SmallVectorImpl<T>(N) {
1246    this->append(A.begin(), A.end());
1247  }
1248
1249  SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) {
1250    if (!RHS.empty())
1251      SmallVectorImpl<T>::operator=(RHS);
1252  }
1253
1254  SmallVector &operator=(const SmallVector &RHS) {
1255    SmallVectorImpl<T>::operator=(RHS);
1256    return *this;
1257  }
1258
1259  SmallVector(SmallVector &&RHS) : SmallVectorImpl<T>(N) {
1260    if (!RHS.empty())
1261      SmallVectorImpl<T>::operator=(::std::move(RHS));
1262  }
1263
1264  SmallVector(SmallVectorImpl<T> &&RHS) : SmallVectorImpl<T>(N) {
1265    if (!RHS.empty())
1266      SmallVectorImpl<T>::operator=(::std::move(RHS));
1267  }
1268
1269  SmallVector &operator=(SmallVector &&RHS) {
1270    if (N) {
1271      SmallVectorImpl<T>::operator=(::std::move(RHS));
1272      return *this;
1273    }
1274    // SmallVectorImpl<T>::operator= does not leverage N==0. Optimize the
1275    // case.
1276    if (this == &RHS)
1277      return *this;
1278    if (RHS.empty()) {
1279      this->destroy_range(this->begin(), this->end());
1280      this->Size = 0;
1281    } else {
1282      this->assignRemote(std::move(RHS));
1283    }
1284    return *this;
1285  }
1286
1287  SmallVector &operator=(SmallVectorImpl<T> &&RHS) {
1288    SmallVectorImpl<T>::operator=(::std::move(RHS));
1289    return *this;
1290  }
1291
1292  SmallVector &operator=(std::initializer_list<T> IL) {
1293    this->assign(IL);
1294    return *this;
1295  }
1296};
1297
1298template <typename T, unsigned N>
1299inline size_t capacity_in_bytes(const SmallVector<T, N> &X) {
1300  return X.capacity_in_bytes();
1301}
1302
1303template <typename RangeType>
1304using ValueTypeFromRangeType =
1305    std::remove_const_t<std::remove_reference_t<decltype(*std::begin(
1306        std::declval<RangeType &>()))>>;
1307
1308/// Given a range of type R, iterate the entire range and return a
1309/// SmallVector with elements of the vector.  This is useful, for example,
1310/// when you want to iterate a range and then sort the results.
1311template <unsigned Size, typename R>
1312SmallVector<ValueTypeFromRangeType<R>, Size> to_vector(R &&Range) {
1313  return {std::begin(Range), std::end(Range)};
1314}
1315template <typename R>
1316SmallVector<ValueTypeFromRangeType<R>> to_vector(R &&Range) {
1317  return {std::begin(Range), std::end(Range)};
1318}
1319
1320template <typename Out, unsigned Size, typename R>
1321SmallVector<Out, Size> to_vector_of(R &&Range) {
1322  return {std::begin(Range), std::end(Range)};
1323}
1324
1325template <typename Out, typename R> SmallVector<Out> to_vector_of(R &&Range) {
1326  return {std::begin(Range), std::end(Range)};
1327}
1328
1329// Explicit instantiations
1330extern template class llvm::SmallVectorBase<uint32_t>;
1331#if SIZE_MAX > UINT32_MAX
1332extern template class llvm::SmallVectorBase<uint64_t>;
1333#endif
1334
1335} // end namespace llvm
1336
1337namespace std {
1338
1339  /// Implement std::swap in terms of SmallVector swap.
1340  template<typename T>
1341  inline void
1342  swap(llvm::SmallVectorImpl<T> &LHS, llvm::SmallVectorImpl<T> &RHS) {
1343    LHS.swap(RHS);
1344  }
1345
1346  /// Implement std::swap in terms of SmallVector swap.
1347  template<typename T, unsigned N>
1348  inline void
1349  swap(llvm::SmallVector<T, N> &LHS, llvm::SmallVector<T, N> &RHS) {
1350    LHS.swap(RHS);
1351  }
1352
1353} // end namespace std
1354
1355#endif // LLVM_ADT_SMALLVECTOR_H
1356