llvm.org GIT mirror llvm / 3995e3e include / llvm / ADT / STLExtras.h
3995e3e

Tree @3995e3e (Download .tar.gz)

STLExtras.h @3995e3eraw · history · blame

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
//===- llvm/ADT/STLExtras.h - Useful STL related functions ------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains some templates that are useful if you are working with the
// STL at all.
//
// No library is required when using these functions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_STLEXTRAS_H
#define LLVM_ADT_STLEXTRAS_H

#include <algorithm> // for std::all_of
#include <cassert>
#include <cstddef> // for std::size_t
#include <cstdlib> // for qsort
#include <functional>
#include <iterator>
#include <limits>
#include <memory>
#include <tuple>
#include <utility> // for std::pair

#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"

namespace llvm {

// Only used by compiler if both template types are the same.  Useful when
// using SFINAE to test for the existence of member functions.
template <typename T, T> struct SameType;

namespace detail {

template <typename RangeT>
using IterOfRange = decltype(std::begin(std::declval<RangeT &>()));

template <typename RangeT>
using ValueOfRange = typename std::remove_reference<decltype(
    *std::begin(std::declval<RangeT &>()))>::type;

} // End detail namespace

//===----------------------------------------------------------------------===//
//     Extra additions to <functional>
//===----------------------------------------------------------------------===//

template<class Ty>
struct identity : public std::unary_function<Ty, Ty> {
  Ty &operator()(Ty &self) const {
    return self;
  }
  const Ty &operator()(const Ty &self) const {
    return self;
  }
};

template<class Ty>
struct less_ptr : public std::binary_function<Ty, Ty, bool> {
  bool operator()(const Ty* left, const Ty* right) const {
    return *left < *right;
  }
};

template<class Ty>
struct greater_ptr : public std::binary_function<Ty, Ty, bool> {
  bool operator()(const Ty* left, const Ty* right) const {
    return *right < *left;
  }
};

/// An efficient, type-erasing, non-owning reference to a callable. This is
/// intended for use as the type of a function parameter that is not used
/// after the function in question returns.
///
/// This class does not own the callable, so it is not in general safe to store
/// a function_ref.
template<typename Fn> class function_ref;

template<typename Ret, typename ...Params>
class function_ref<Ret(Params...)> {
  Ret (*callback)(intptr_t callable, Params ...params);
  intptr_t callable;

  template<typename Callable>
  static Ret callback_fn(intptr_t callable, Params ...params) {
    return (*reinterpret_cast<Callable*>(callable))(
        std::forward<Params>(params)...);
  }

public:
  template <typename Callable>
  function_ref(Callable &&callable,
               typename std::enable_if<
                   !std::is_same<typename std::remove_reference<Callable>::type,
                                 function_ref>::value>::type * = nullptr)
      : callback(callback_fn<typename std::remove_reference<Callable>::type>),
        callable(reinterpret_cast<intptr_t>(&callable)) {}
  Ret operator()(Params ...params) const {
    return callback(callable, std::forward<Params>(params)...);
  }
};

// deleter - Very very very simple method that is used to invoke operator
// delete on something.  It is used like this:
//
//   for_each(V.begin(), B.end(), deleter<Interval>);
//
template <class T>
inline void deleter(T *Ptr) {
  delete Ptr;
}



//===----------------------------------------------------------------------===//
//     Extra additions to <iterator>
//===----------------------------------------------------------------------===//

// mapped_iterator - This is a simple iterator adapter that causes a function to
// be applied whenever operator* is invoked on the iterator.
//
template <class RootIt, class UnaryFunc>
class mapped_iterator {
  RootIt current;
  UnaryFunc Fn;
public:
  typedef typename std::iterator_traits<RootIt>::iterator_category
          iterator_category;
  typedef typename std::iterator_traits<RootIt>::difference_type
          difference_type;
  typedef decltype(std::declval<UnaryFunc>()(*std::declval<RootIt>()))
          value_type;

  typedef void pointer;
  //typedef typename UnaryFunc::result_type *pointer;
  typedef void reference;        // Can't modify value returned by fn

  typedef RootIt iterator_type;

  inline const RootIt &getCurrent() const { return current; }
  inline const UnaryFunc &getFunc() const { return Fn; }

  inline explicit mapped_iterator(const RootIt &I, UnaryFunc F)
    : current(I), Fn(F) {}

  inline value_type operator*() const {   // All this work to do this
    return Fn(*current);         // little change
  }

  mapped_iterator &operator++() {
    ++current;
    return *this;
  }
  mapped_iterator &operator--() {
    --current;
    return *this;
  }
  mapped_iterator operator++(int) {
    mapped_iterator __tmp = *this;
    ++current;
    return __tmp;
  }
  mapped_iterator operator--(int) {
    mapped_iterator __tmp = *this;
    --current;
    return __tmp;
  }
  mapped_iterator operator+(difference_type n) const {
    return mapped_iterator(current + n, Fn);
  }
  mapped_iterator &operator+=(difference_type n) {
    current += n;
    return *this;
  }
  mapped_iterator operator-(difference_type n) const {
    return mapped_iterator(current - n, Fn);
  }
  mapped_iterator &operator-=(difference_type n) {
    current -= n;
    return *this;
  }
  reference operator[](difference_type n) const { return *(*this + n); }

  bool operator!=(const mapped_iterator &X) const { return !operator==(X); }
  bool operator==(const mapped_iterator &X) const {
    return current == X.current;
  }
  bool operator<(const mapped_iterator &X) const { return current < X.current; }

  difference_type operator-(const mapped_iterator &X) const {
    return current - X.current;
  }
};

template <class Iterator, class Func>
inline mapped_iterator<Iterator, Func>
operator+(typename mapped_iterator<Iterator, Func>::difference_type N,
          const mapped_iterator<Iterator, Func> &X) {
  return mapped_iterator<Iterator, Func>(X.getCurrent() - N, X.getFunc());
}


// map_iterator - Provide a convenient way to create mapped_iterators, just like
// make_pair is useful for creating pairs...
//
template <class ItTy, class FuncTy>
inline mapped_iterator<ItTy, FuncTy> map_iterator(const ItTy &I, FuncTy F) {
  return mapped_iterator<ItTy, FuncTy>(I, F);
}

/// Helper to determine if type T has a member called rbegin().
template <typename Ty> class has_rbegin_impl {
  typedef char yes[1];
  typedef char no[2];

  template <typename Inner>
  static yes& test(Inner *I, decltype(I->rbegin()) * = nullptr);

  template <typename>
  static no& test(...);

public:
  static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
};

/// Metafunction to determine if T& or T has a member called rbegin().
template <typename Ty>
struct has_rbegin : has_rbegin_impl<typename std::remove_reference<Ty>::type> {
};

// Returns an iterator_range over the given container which iterates in reverse.
// Note that the container must have rbegin()/rend() methods for this to work.
template <typename ContainerTy>
auto reverse(ContainerTy &&C,
             typename std::enable_if<has_rbegin<ContainerTy>::value>::type * =
                 nullptr) -> decltype(make_range(C.rbegin(), C.rend())) {
  return make_range(C.rbegin(), C.rend());
}

// Returns a std::reverse_iterator wrapped around the given iterator.
template <typename IteratorTy>
std::reverse_iterator<IteratorTy> make_reverse_iterator(IteratorTy It) {
  return std::reverse_iterator<IteratorTy>(It);
}

// Returns an iterator_range over the given container which iterates in reverse.
// Note that the container must have begin()/end() methods which return
// bidirectional iterators for this to work.
template <typename ContainerTy>
auto reverse(
    ContainerTy &&C,
    typename std::enable_if<!has_rbegin<ContainerTy>::value>::type * = nullptr)
    -> decltype(make_range(llvm::make_reverse_iterator(std::end(C)),
                           llvm::make_reverse_iterator(std::begin(C)))) {
  return make_range(llvm::make_reverse_iterator(std::end(C)),
                    llvm::make_reverse_iterator(std::begin(C)));
}

/// An iterator adaptor that filters the elements of given inner iterators.
///
/// The predicate parameter should be a callable object that accepts the wrapped
/// iterator's reference type and returns a bool. When incrementing or
/// decrementing the iterator, it will call the predicate on each element and
/// skip any where it returns false.
///
/// \code
///   int A[] = { 1, 2, 3, 4 };
///   auto R = make_filter_range(A, [](int N) { return N % 2 == 1; });
///   // R contains { 1, 3 }.
/// \endcode
template <typename WrappedIteratorT, typename PredicateT>
class filter_iterator
    : public iterator_adaptor_base<
          filter_iterator<WrappedIteratorT, PredicateT>, WrappedIteratorT,
          typename std::common_type<
              std::forward_iterator_tag,
              typename std::iterator_traits<
                  WrappedIteratorT>::iterator_category>::type> {
  using BaseT = iterator_adaptor_base<
      filter_iterator<WrappedIteratorT, PredicateT>, WrappedIteratorT,
      typename std::common_type<
          std::forward_iterator_tag,
          typename std::iterator_traits<WrappedIteratorT>::iterator_category>::
          type>;

  struct PayloadType {
    WrappedIteratorT End;
    PredicateT Pred;
  };

  Optional<PayloadType> Payload;

  void findNextValid() {
    assert(Payload && "Payload should be engaged when findNextValid is called");
    while (this->I != Payload->End && !Payload->Pred(*this->I))
      BaseT::operator++();
  }

  // Construct the begin iterator. The begin iterator requires to know where end
  // is, so that it can properly stop when it hits end.
  filter_iterator(WrappedIteratorT Begin, WrappedIteratorT End, PredicateT Pred)
      : BaseT(std::move(Begin)),
        Payload(PayloadType{std::move(End), std::move(Pred)}) {
    findNextValid();
  }

  // Construct the end iterator. It's not incrementable, so Payload doesn't
  // have to be engaged.
  filter_iterator(WrappedIteratorT End) : BaseT(End) {}

public:
  using BaseT::operator++;

  filter_iterator &operator++() {
    BaseT::operator++();
    findNextValid();
    return *this;
  }

  template <typename RT, typename PT>
  friend iterator_range<filter_iterator<detail::IterOfRange<RT>, PT>>
  make_filter_range(RT &&, PT);
};

/// Convenience function that takes a range of elements and a predicate,
/// and return a new filter_iterator range.
///
/// FIXME: Currently if RangeT && is a rvalue reference to a temporary, the
/// lifetime of that temporary is not kept by the returned range object, and the
/// temporary is going to be dropped on the floor after the make_iterator_range
/// full expression that contains this function call.
template <typename RangeT, typename PredicateT>
iterator_range<filter_iterator<detail::IterOfRange<RangeT>, PredicateT>>
make_filter_range(RangeT &&Range, PredicateT Pred) {
  using FilterIteratorT =
      filter_iterator<detail::IterOfRange<RangeT>, PredicateT>;
  return make_range(FilterIteratorT(std::begin(std::forward<RangeT>(Range)),
                                    std::end(std::forward<RangeT>(Range)),
                                    std::move(Pred)),
                    FilterIteratorT(std::end(std::forward<RangeT>(Range))));
}

// forward declarations required by zip_shortest/zip_first
template <typename R, typename UnaryPredicate>
bool all_of(R &&range, UnaryPredicate P);

template <size_t... I> struct index_sequence;

template <class... Ts> struct index_sequence_for;

namespace detail {
using std::declval;

// We have to alias this since inlining the actual type at the usage site
// in the parameter list of iterator_facade_base<> below ICEs MSVC 2017.
template<typename... Iters> struct ZipTupleType {
  typedef std::tuple<decltype(*declval<Iters>())...> type;
};

template <typename ZipType, typename... Iters>
using zip_traits = iterator_facade_base<
    ZipType, typename std::common_type<std::bidirectional_iterator_tag,
                                       typename std::iterator_traits<
                                           Iters>::iterator_category...>::type,
    // ^ TODO: Implement random access methods.
    typename ZipTupleType<Iters...>::type,
    typename std::iterator_traits<typename std::tuple_element<
        0, std::tuple<Iters...>>::type>::difference_type,
    // ^ FIXME: This follows boost::make_zip_iterator's assumption that all
    // inner iterators have the same difference_type. It would fail if, for
    // instance, the second field's difference_type were non-numeric while the
    // first is.
    typename ZipTupleType<Iters...>::type *,
    typename ZipTupleType<Iters...>::type>;

template <typename ZipType, typename... Iters>
struct zip_common : public zip_traits<ZipType, Iters...> {
  using Base = zip_traits<ZipType, Iters...>;
  using value_type = typename Base::value_type;

  std::tuple<Iters...> iterators;

protected:
  template <size_t... Ns> value_type deref(index_sequence<Ns...>) const {
    return value_type(*std::get<Ns>(iterators)...);
  }

  template <size_t... Ns>
  decltype(iterators) tup_inc(index_sequence<Ns...>) const {
    return std::tuple<Iters...>(std::next(std::get<Ns>(iterators))...);
  }

  template <size_t... Ns>
  decltype(iterators) tup_dec(index_sequence<Ns...>) const {
    return std::tuple<Iters...>(std::prev(std::get<Ns>(iterators))...);
  }

public:
  zip_common(Iters &&... ts) : iterators(std::forward<Iters>(ts)...) {}

  value_type operator*() { return deref(index_sequence_for<Iters...>{}); }

  const value_type operator*() const {
    return deref(index_sequence_for<Iters...>{});
  }

  ZipType &operator++() {
    iterators = tup_inc(index_sequence_for<Iters...>{});
    return *reinterpret_cast<ZipType *>(this);
  }

  ZipType &operator--() {
    static_assert(Base::IsBidirectional,
                  "All inner iterators must be at least bidirectional.");
    iterators = tup_dec(index_sequence_for<Iters...>{});
    return *reinterpret_cast<ZipType *>(this);
  }
};

template <typename... Iters>
struct zip_first : public zip_common<zip_first<Iters...>, Iters...> {
  using Base = zip_common<zip_first<Iters...>, Iters...>;

  bool operator==(const zip_first<Iters...> &other) const {
    return std::get<0>(this->iterators) == std::get<0>(other.iterators);
  }

  zip_first(Iters &&... ts) : Base(std::forward<Iters>(ts)...) {}
};

template <typename... Iters>
class zip_shortest : public zip_common<zip_shortest<Iters...>, Iters...> {
  template <size_t... Ns>
  bool test(const zip_shortest<Iters...> &other, index_sequence<Ns...>) const {
    return all_of(std::initializer_list<bool>{std::get<Ns>(this->iterators) !=
                                              std::get<Ns>(other.iterators)...},
                  identity<bool>{});
  }

public:
  using Base = zip_common<zip_shortest<Iters...>, Iters...>;

  bool operator==(const zip_shortest<Iters...> &other) const {
    return !test(other, index_sequence_for<Iters...>{});
  }

  zip_shortest(Iters &&... ts) : Base(std::forward<Iters>(ts)...) {}
};

template <template <typename...> class ItType, typename... Args> class zippy {
public:
  using iterator = ItType<decltype(std::begin(std::declval<Args>()))...>;
  using iterator_category = typename iterator::iterator_category;
  using value_type = typename iterator::value_type;
  using difference_type = typename iterator::difference_type;
  using pointer = typename iterator::pointer;
  using reference = typename iterator::reference;

private:
  std::tuple<Args...> ts;

  template <size_t... Ns> iterator begin_impl(index_sequence<Ns...>) const {
    return iterator(std::begin(std::get<Ns>(ts))...);
  }
  template <size_t... Ns> iterator end_impl(index_sequence<Ns...>) const {
    return iterator(std::end(std::get<Ns>(ts))...);
  }

public:
  iterator begin() const { return begin_impl(index_sequence_for<Args...>{}); }
  iterator end() const { return end_impl(index_sequence_for<Args...>{}); }
  zippy(Args &&... ts_) : ts(std::forward<Args>(ts_)...) {}
};
} // End detail namespace

/// zip iterator for two or more iteratable types.
template <typename T, typename U, typename... Args>
detail::zippy<detail::zip_shortest, T, U, Args...> zip(T &&t, U &&u,
                                                       Args &&... args) {
  return detail::zippy<detail::zip_shortest, T, U, Args...>(
      std::forward<T>(t), std::forward<U>(u), std::forward<Args>(args)...);
}

/// zip iterator that, for the sake of efficiency, assumes the first iteratee to
/// be the shortest.
template <typename T, typename U, typename... Args>
detail::zippy<detail::zip_first, T, U, Args...> zip_first(T &&t, U &&u,
                                                          Args &&... args) {
  return detail::zippy<detail::zip_first, T, U, Args...>(
      std::forward<T>(t), std::forward<U>(u), std::forward<Args>(args)...);
}

/// Iterator wrapper that concatenates sequences together.
///
/// This can concatenate different iterators, even with different types, into
/// a single iterator provided the value types of all the concatenated
/// iterators expose `reference` and `pointer` types that can be converted to
/// `ValueT &` and `ValueT *` respectively. It doesn't support more
/// interesting/customized pointer or reference types.
///
/// Currently this only supports forward or higher iterator categories as
/// inputs and always exposes a forward iterator interface.
template <typename ValueT, typename... IterTs>
class concat_iterator
    : public iterator_facade_base<concat_iterator<ValueT, IterTs...>,
                                  std::forward_iterator_tag, ValueT> {
  typedef typename concat_iterator::iterator_facade_base BaseT;

  /// We store both the current and end iterators for each concatenated
  /// sequence in a tuple of pairs.
  ///
  /// Note that something like iterator_range seems nice at first here, but the
  /// range properties are of little benefit and end up getting in the way
  /// because we need to do mutation on the current iterators.
  std::tuple<std::pair<IterTs, IterTs>...> IterPairs;

  /// Attempts to increment a specific iterator.
  ///
  /// Returns true if it was able to increment the iterator. Returns false if
  /// the iterator is already at the end iterator.
  template <size_t Index> bool incrementHelper() {
    auto &IterPair = std::get<Index>(IterPairs);
    if (IterPair.first == IterPair.second)
      return false;

    ++IterPair.first;
    return true;
  }

  /// Increments the first non-end iterator.
  ///
  /// It is an error to call this with all iterators at the end.
  template <size_t... Ns> void increment(index_sequence<Ns...>) {
    // Build a sequence of functions to increment each iterator if possible.
    bool (concat_iterator::*IncrementHelperFns[])() = {
        &concat_iterator::incrementHelper<Ns>...};

    // Loop over them, and stop as soon as we succeed at incrementing one.
    for (auto &IncrementHelperFn : IncrementHelperFns)
      if ((this->*IncrementHelperFn)())
        return;

    llvm_unreachable("Attempted to increment an end concat iterator!");
  }

  /// Returns null if the specified iterator is at the end. Otherwise,
  /// dereferences the iterator and returns the address of the resulting
  /// reference.
  template <size_t Index> ValueT *getHelper() const {
    auto &IterPair = std::get<Index>(IterPairs);
    if (IterPair.first == IterPair.second)
      return nullptr;

    return &*IterPair.first;
  }

  /// Finds the first non-end iterator, dereferences, and returns the resulting
  /// reference.
  ///
  /// It is an error to call this with all iterators at the end.
  template <size_t... Ns> ValueT &get(index_sequence<Ns...>) const {
    // Build a sequence of functions to get from iterator if possible.
    ValueT *(concat_iterator::*GetHelperFns[])() const = {
        &concat_iterator::getHelper<Ns>...};

    // Loop over them, and return the first result we find.
    for (auto &GetHelperFn : GetHelperFns)
      if (ValueT *P = (this->*GetHelperFn)())
        return *P;

    llvm_unreachable("Attempted to get a pointer from an end concat iterator!");
  }

public:
  /// Constructs an iterator from a squence of ranges.
  ///
  /// We need the full range to know how to switch between each of the
  /// iterators.
  template <typename... RangeTs>
  explicit concat_iterator(RangeTs &&... Ranges)
      : IterPairs({std::begin(Ranges), std::end(Ranges)}...) {}

  using BaseT::operator++;
  concat_iterator &operator++() {
    increment(index_sequence_for<IterTs...>());
    return *this;
  }

  ValueT &operator*() const { return get(index_sequence_for<IterTs...>()); }

  bool operator==(const concat_iterator &RHS) const {
    return IterPairs == RHS.IterPairs;
  }
};

namespace detail {
/// Helper to store a sequence of ranges being concatenated and access them.
///
/// This is designed to facilitate providing actual storage when temporaries
/// are passed into the constructor such that we can use it as part of range
/// based for loops.
template <typename ValueT, typename... RangeTs> class concat_range {
public:
  typedef concat_iterator<ValueT,
                          decltype(std::begin(std::declval<RangeTs &>()))...>
      iterator;

private:
  std::tuple<RangeTs...> Ranges;

  template <size_t... Ns> iterator begin_impl(index_sequence<Ns...>) {
    return iterator(std::get<Ns>(Ranges)...);
  }
  template <size_t... Ns> iterator end_impl(index_sequence<Ns...>) {
    return iterator(make_range(std::end(std::get<Ns>(Ranges)),
                               std::end(std::get<Ns>(Ranges)))...);
  }

public:
  iterator begin() { return begin_impl(index_sequence_for<RangeTs...>{}); }
  iterator end() { return end_impl(index_sequence_for<RangeTs...>{}); }
  concat_range(RangeTs &&... Ranges)
      : Ranges(std::forward<RangeTs>(Ranges)...) {}
};
}

/// Concatenated range across two or more ranges.
///
/// The desired value type must be explicitly specified.
template <typename ValueT, typename... RangeTs>
detail::concat_range<ValueT, RangeTs...> concat(RangeTs &&... Ranges) {
  static_assert(sizeof...(RangeTs) > 1,
                "Need more than one range to concatenate!");
  return detail::concat_range<ValueT, RangeTs...>(
      std::forward<RangeTs>(Ranges)...);
}

//===----------------------------------------------------------------------===//
//     Extra additions to <utility>
//===----------------------------------------------------------------------===//

/// \brief Function object to check whether the first component of a std::pair
/// compares less than the first component of another std::pair.
struct less_first {
  template <typename T> bool operator()(const T &lhs, const T &rhs) const {
    return lhs.first < rhs.first;
  }
};

/// \brief Function object to check whether the second component of a std::pair
/// compares less than the second component of another std::pair.
struct less_second {
  template <typename T> bool operator()(const T &lhs, const T &rhs) const {
    return lhs.second < rhs.second;
  }
};

// A subset of N3658. More stuff can be added as-needed.

/// \brief Represents a compile-time sequence of integers.
template <class T, T... I> struct integer_sequence {
  typedef T value_type;

  static constexpr size_t size() { return sizeof...(I); }
};

/// \brief Alias for the common case of a sequence of size_ts.
template <size_t... I>
struct index_sequence : integer_sequence<std::size_t, I...> {};

template <std::size_t N, std::size_t... I>
struct build_index_impl : build_index_impl<N - 1, N - 1, I...> {};
template <std::size_t... I>
struct build_index_impl<0, I...> : index_sequence<I...> {};

/// \brief Creates a compile-time integer sequence for a parameter pack.
template <class... Ts>
struct index_sequence_for : build_index_impl<sizeof...(Ts)> {};

/// Utility type to build an inheritance chain that makes it easy to rank
/// overload candidates.
template <int N> struct rank : rank<N - 1> {};
template <> struct rank<0> {};

/// \brief traits class for checking whether type T is one of any of the given
/// types in the variadic list.
template <typename T, typename... Ts> struct is_one_of {
  static const bool value = false;
};

template <typename T, typename U, typename... Ts>
struct is_one_of<T, U, Ts...> {
  static const bool value =
      std::is_same<T, U>::value || is_one_of<T, Ts...>::value;
};

//===----------------------------------------------------------------------===//
//     Extra additions for arrays
//===----------------------------------------------------------------------===//

/// Find the length of an array.
template <class T, std::size_t N>
constexpr inline size_t array_lengthof(T (&)[N]) {
  return N;
}

/// Adapt std::less<T> for array_pod_sort.
template<typename T>
inline int array_pod_sort_comparator(const void *P1, const void *P2) {
  if (std::less<T>()(*reinterpret_cast<const T*>(P1),
                     *reinterpret_cast<const T*>(P2)))
    return -1;
  if (std::less<T>()(*reinterpret_cast<const T*>(P2),
                     *reinterpret_cast<const T*>(P1)))
    return 1;
  return 0;
}

/// get_array_pod_sort_comparator - This is an internal helper function used to
/// get type deduction of T right.
template<typename T>
inline int (*get_array_pod_sort_comparator(const T &))
             (const void*, const void*) {
  return array_pod_sort_comparator<T>;
}


/// array_pod_sort - This sorts an array with the specified start and end
/// extent.  This is just like std::sort, except that it calls qsort instead of
/// using an inlined template.  qsort is slightly slower than std::sort, but
/// most sorts are not performance critical in LLVM and std::sort has to be
/// template instantiated for each type, leading to significant measured code
/// bloat.  This function should generally be used instead of std::sort where
/// possible.
///
/// This function assumes that you have simple POD-like types that can be
/// compared with std::less and can be moved with memcpy.  If this isn't true,
/// you should use std::sort.
///
/// NOTE: If qsort_r were portable, we could allow a custom comparator and
/// default to std::less.
template<class IteratorTy>
inline void array_pod_sort(IteratorTy Start, IteratorTy End) {
  // Don't inefficiently call qsort with one element or trigger undefined
  // behavior with an empty sequence.
  auto NElts = End - Start;
  if (NElts <= 1) return;
  qsort(&*Start, NElts, sizeof(*Start), get_array_pod_sort_comparator(*Start));
}

template <class IteratorTy>
inline void array_pod_sort(
    IteratorTy Start, IteratorTy End,
    int (*Compare)(
        const typename std::iterator_traits<IteratorTy>::value_type *,
        const typename std::iterator_traits<IteratorTy>::value_type *)) {
  // Don't inefficiently call qsort with one element or trigger undefined
  // behavior with an empty sequence.
  auto NElts = End - Start;
  if (NElts <= 1) return;
  qsort(&*Start, NElts, sizeof(*Start),
        reinterpret_cast<int (*)(const void *, const void *)>(Compare));
}

//===----------------------------------------------------------------------===//
//     Extra additions to <algorithm>
//===----------------------------------------------------------------------===//

/// For a container of pointers, deletes the pointers and then clears the
/// container.
template<typename Container>
void DeleteContainerPointers(Container &C) {
  for (auto V : C)
    delete V;
  C.clear();
}

/// In a container of pairs (usually a map) whose second element is a pointer,
/// deletes the second elements and then clears the container.
template<typename Container>
void DeleteContainerSeconds(Container &C) {
  for (auto &V : C)
    delete V.second;
  C.clear();
}

/// Provide wrappers to std::all_of which take ranges instead of having to pass
/// begin/end explicitly.
template <typename R, typename UnaryPredicate>
bool all_of(R &&Range, UnaryPredicate P) {
  return std::all_of(std::begin(Range), std::end(Range), P);
}

/// Provide wrappers to std::any_of which take ranges instead of having to pass
/// begin/end explicitly.
template <typename R, typename UnaryPredicate>
bool any_of(R &&Range, UnaryPredicate P) {
  return std::any_of(std::begin(Range), std::end(Range), P);
}

/// Provide wrappers to std::none_of which take ranges instead of having to pass
/// begin/end explicitly.
template <typename R, typename UnaryPredicate>
bool none_of(R &&Range, UnaryPredicate P) {
  return std::none_of(std::begin(Range), std::end(Range), P);
}

/// Provide wrappers to std::find which take ranges instead of having to pass
/// begin/end explicitly.
template <typename R, typename T>
auto find(R &&Range, const T &Val) -> decltype(std::begin(Range)) {
  return std::find(std::begin(Range), std::end(Range), Val);
}

/// Provide wrappers to std::find_if which take ranges instead of having to pass
/// begin/end explicitly.
template <typename R, typename UnaryPredicate>
auto find_if(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range)) {
  return std::find_if(std::begin(Range), std::end(Range), P);
}

template <typename R, typename UnaryPredicate>
auto find_if_not(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range)) {
  return std::find_if_not(std::begin(Range), std::end(Range), P);
}

/// Provide wrappers to std::remove_if which take ranges instead of having to
/// pass begin/end explicitly.
template <typename R, typename UnaryPredicate>
auto remove_if(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range)) {
  return std::remove_if(std::begin(Range), std::end(Range), P);
}

/// Provide wrappers to std::copy_if which take ranges instead of having to
/// pass begin/end explicitly.
template <typename R, typename OutputIt, typename UnaryPredicate>
OutputIt copy_if(R &&Range, OutputIt Out, UnaryPredicate P) {
  return std::copy_if(std::begin(Range), std::end(Range), Out, P);
}

/// Wrapper function around std::find to detect if an element exists
/// in a container.
template <typename R, typename E>
bool is_contained(R &&Range, const E &Element) {
  return std::find(std::begin(Range), std::end(Range), Element) !=
         std::end(Range);
}

/// Wrapper function around std::count to count the number of times an element
/// \p Element occurs in the given range \p Range.
template <typename R, typename E>
auto count(R &&Range, const E &Element) -> typename std::iterator_traits<
    decltype(std::begin(Range))>::difference_type {
  return std::count(std::begin(Range), std::end(Range), Element);
}

/// Wrapper function around std::count_if to count the number of times an
/// element satisfying a given predicate occurs in a range.
template <typename R, typename UnaryPredicate>
auto count_if(R &&Range, UnaryPredicate P) -> typename std::iterator_traits<
    decltype(std::begin(Range))>::difference_type {
  return std::count_if(std::begin(Range), std::end(Range), P);
}

/// Wrapper function around std::transform to apply a function to a range and
/// store the result elsewhere.
template <typename R, typename OutputIt, typename UnaryPredicate>
OutputIt transform(R &&Range, OutputIt d_first, UnaryPredicate P) {
  return std::transform(std::begin(Range), std::end(Range), d_first, P);
}

/// Provide wrappers to std::partition which take ranges instead of having to
/// pass begin/end explicitly.
template <typename R, typename UnaryPredicate>
auto partition(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range)) {
  return std::partition(std::begin(Range), std::end(Range), P);
}

/// \brief Given a range of type R, iterate the entire range and return a
/// SmallVector with elements of the vector.  This is useful, for example,
/// when you want to iterate a range and then sort the results.
template <unsigned Size, typename R>
SmallVector<typename std::remove_const<detail::ValueOfRange<R>>::type, Size>
to_vector(R &&Range) {
  return {std::begin(Range), std::end(Range)};
}

/// Provide a container algorithm similar to C++ Library Fundamentals v2's
/// `erase_if` which is equivalent to:
///
///   C.erase(remove_if(C, pred), C.end());
///
/// This version works for any container with an erase method call accepting
/// two iterators.
template <typename Container, typename UnaryPredicate>
void erase_if(Container &C, UnaryPredicate P) {
  C.erase(remove_if(C, P), C.end());
}

//===----------------------------------------------------------------------===//
//     Extra additions to <memory>
//===----------------------------------------------------------------------===//

// Implement make_unique according to N3656.

/// \brief Constructs a `new T()` with the given args and returns a
///        `unique_ptr<T>` which owns the object.
///
/// Example:
///
///     auto p = make_unique<int>();
///     auto p = make_unique<std::tuple<int, int>>(0, 1);
template <class T, class... Args>
typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type
make_unique(Args &&... args) {
  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}

/// \brief Constructs a `new T[n]` with the given args and returns a
///        `unique_ptr<T[]>` which owns the object.
///
/// \param n size of the new array.
///
/// Example:
///
///     auto p = make_unique<int[]>(2); // value-initializes the array with 0's.
template <class T>
typename std::enable_if<std::is_array<T>::value && std::extent<T>::value == 0,
                        std::unique_ptr<T>>::type
make_unique(size_t n) {
  return std::unique_ptr<T>(new typename std::remove_extent<T>::type[n]());
}

/// This function isn't used and is only here to provide better compile errors.
template <class T, class... Args>
typename std::enable_if<std::extent<T>::value != 0>::type
make_unique(Args &&...) = delete;

struct FreeDeleter {
  void operator()(void* v) {
    ::free(v);
  }
};

template<typename First, typename Second>
struct pair_hash {
  size_t operator()(const std::pair<First, Second> &P) const {
    return std::hash<First>()(P.first) * 31 + std::hash<Second>()(P.second);
  }
};

/// A functor like C++14's std::less<void> in its absence.
struct less {
  template <typename A, typename B> bool operator()(A &&a, B &&b) const {
    return std::forward<A>(a) < std::forward<B>(b);
  }
};

/// A functor like C++14's std::equal<void> in its absence.
struct equal {
  template <typename A, typename B> bool operator()(A &&a, B &&b) const {
    return std::forward<A>(a) == std::forward<B>(b);
  }
};

/// Binary functor that adapts to any other binary functor after dereferencing
/// operands.
template <typename T> struct deref {
  T func;
  // Could be further improved to cope with non-derivable functors and
  // non-binary functors (should be a variadic template member function
  // operator()).
  template <typename A, typename B>
  auto operator()(A &lhs, B &rhs) const -> decltype(func(*lhs, *rhs)) {
    assert(lhs);
    assert(rhs);
    return func(*lhs, *rhs);
  }
};

namespace detail {
template <typename R> class enumerator_iter;

template <typename R> struct result_pair {
  friend class enumerator_iter<R>;

  result_pair() : Index(-1) {}
  result_pair(std::size_t Index, IterOfRange<R> Iter)
      : Index(Index), Iter(Iter) {}

  result_pair<R> &operator=(const result_pair<R> &Other) {
    Index = Other.Index;
    Iter = Other.Iter;
    return *this;
  }

  std::size_t index() const { return Index; }
  const ValueOfRange<R> &value() const { return *Iter; }
  ValueOfRange<R> &value() { return *Iter; }

private:
  std::size_t Index;
  IterOfRange<R> Iter;
};

template <typename R>
class enumerator_iter
    : public iterator_facade_base<
          enumerator_iter<R>, std::forward_iterator_tag, result_pair<R>,
          typename std::iterator_traits<IterOfRange<R>>::difference_type,
          typename std::iterator_traits<IterOfRange<R>>::pointer,
          typename std::iterator_traits<IterOfRange<R>>::reference> {
  using result_type = result_pair<R>;

public:
  explicit enumerator_iter(IterOfRange<R> EndIter)
    : Result(std::numeric_limits<size_t>::max(), EndIter) { }

  enumerator_iter(std::size_t Index, IterOfRange<R> Iter)
      : Result(Index, Iter) {}

  result_type &operator*() { return Result; }
  const result_type &operator*() const { return Result; }

  enumerator_iter<R> &operator++() {
    assert(Result.Index != std::numeric_limits<size_t>::max());
    ++Result.Iter;
    ++Result.Index;
    return *this;
  }

  bool operator==(const enumerator_iter<R> &RHS) const {
    // Don't compare indices here, only iterators.  It's possible for an end
    // iterator to have different indices depending on whether it was created
    // by calling std::end() versus incrementing a valid iterator.
    return Result.Iter == RHS.Result.Iter;
  }

  enumerator_iter<R> &operator=(const enumerator_iter<R> &Other) {
    Result = Other.Result;
    return *this;
  }

private:
  result_type Result;
};

template <typename R> class enumerator {
public:
  explicit enumerator(R &&Range) : TheRange(std::forward<R>(Range)) {}

  enumerator_iter<R> begin() {
    return enumerator_iter<R>(0, std::begin(TheRange));
  }
  enumerator_iter<R> end() {
    return enumerator_iter<R>(std::end(TheRange));
  }

private:
  R TheRange;
};
}

/// Given an input range, returns a new range whose values are are pair (A,B)
/// such that A is the 0-based index of the item in the sequence, and B is
/// the value from the original sequence.  Example:
///
/// std::vector<char> Items = {'A', 'B', 'C', 'D'};
/// for (auto X : enumerate(Items)) {
///   printf("Item %d - %c\n", X.Index, X.Value);
/// }
///
/// Output:
///   Item 0 - A
///   Item 1 - B
///   Item 2 - C
///   Item 3 - D
///
template <typename R> detail::enumerator<R> enumerate(R &&TheRange) {
  return detail::enumerator<R>(std::forward<R>(TheRange));
}

namespace detail {
template <typename F, typename Tuple, std::size_t... I>
auto apply_tuple_impl(F &&f, Tuple &&t, index_sequence<I...>)
    -> decltype(std::forward<F>(f)(std::get<I>(std::forward<Tuple>(t))...)) {
  return std::forward<F>(f)(std::get<I>(std::forward<Tuple>(t))...);
}
}

/// Given an input tuple (a1, a2, ..., an), pass the arguments of the
/// tuple variadically to f as if by calling f(a1, a2, ..., an) and
/// return the result.
template <typename F, typename Tuple>
auto apply_tuple(F &&f, Tuple &&t) -> decltype(detail::apply_tuple_impl(
    std::forward<F>(f), std::forward<Tuple>(t),
    build_index_impl<
        std::tuple_size<typename std::decay<Tuple>::type>::value>{})) {
  using Indices = build_index_impl<
      std::tuple_size<typename std::decay<Tuple>::type>::value>;

  return detail::apply_tuple_impl(std::forward<F>(f), std::forward<Tuple>(t),
                                  Indices{});
}
} // End llvm namespace

#endif