HexagonCommonGEP.cpp 41.8 KB
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 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316
//===- HexagonCommonGEP.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <map>
#include <set>
#include <utility>
#include <vector>

#define DEBUG_TYPE "commgep"

using namespace llvm;

static cl::opt<bool> OptSpeculate("commgep-speculate", cl::init(true),
  cl::Hidden, cl::ZeroOrMore);

static cl::opt<bool> OptEnableInv("commgep-inv", cl::init(true), cl::Hidden,
  cl::ZeroOrMore);

static cl::opt<bool> OptEnableConst("commgep-const", cl::init(true),
  cl::Hidden, cl::ZeroOrMore);

namespace llvm {

  void initializeHexagonCommonGEPPass(PassRegistry&);

} // end namespace llvm

namespace {

  struct GepNode;
  using NodeSet = std::set<GepNode *>;
  using NodeToValueMap = std::map<GepNode *, Value *>;
  using NodeVect = std::vector<GepNode *>;
  using NodeChildrenMap = std::map<GepNode *, NodeVect>;
  using UseSet = SetVector<Use *>;
  using NodeToUsesMap = std::map<GepNode *, UseSet>;

  // Numbering map for gep nodes. Used to keep track of ordering for
  // gep nodes.
  struct NodeOrdering {
    NodeOrdering() = default;

    void insert(const GepNode *N) { Map.insert(std::make_pair(N, ++LastNum)); }
    void clear() { Map.clear(); }

    bool operator()(const GepNode *N1, const GepNode *N2) const {
      auto F1 = Map.find(N1), F2 = Map.find(N2);
      assert(F1 != Map.end() && F2 != Map.end());
      return F1->second < F2->second;
    }

  private:
    std::map<const GepNode *, unsigned> Map;
    unsigned LastNum = 0;
  };

  class HexagonCommonGEP : public FunctionPass {
  public:
    static char ID;

    HexagonCommonGEP() : FunctionPass(ID) {
      initializeHexagonCommonGEPPass(*PassRegistry::getPassRegistry());
    }

    bool runOnFunction(Function &F) override;
    StringRef getPassName() const override { return "Hexagon Common GEP"; }

    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.addRequired<DominatorTreeWrapperPass>();
      AU.addPreserved<DominatorTreeWrapperPass>();
      AU.addRequired<PostDominatorTreeWrapperPass>();
      AU.addPreserved<PostDominatorTreeWrapperPass>();
      AU.addRequired<LoopInfoWrapperPass>();
      AU.addPreserved<LoopInfoWrapperPass>();
      FunctionPass::getAnalysisUsage(AU);
    }

  private:
    using ValueToNodeMap = std::map<Value *, GepNode *>;
    using ValueVect = std::vector<Value *>;
    using NodeToValuesMap = std::map<GepNode *, ValueVect>;

    void getBlockTraversalOrder(BasicBlock *Root, ValueVect &Order);
    bool isHandledGepForm(GetElementPtrInst *GepI);
    void processGepInst(GetElementPtrInst *GepI, ValueToNodeMap &NM);
    void collect();
    void common();

    BasicBlock *recalculatePlacement(GepNode *Node, NodeChildrenMap &NCM,
                                     NodeToValueMap &Loc);
    BasicBlock *recalculatePlacementRec(GepNode *Node, NodeChildrenMap &NCM,
                                        NodeToValueMap &Loc);
    bool isInvariantIn(Value *Val, Loop *L);
    bool isInvariantIn(GepNode *Node, Loop *L);
    bool isInMainPath(BasicBlock *B, Loop *L);
    BasicBlock *adjustForInvariance(GepNode *Node, NodeChildrenMap &NCM,
                                    NodeToValueMap &Loc);
    void separateChainForNode(GepNode *Node, Use *U, NodeToValueMap &Loc);
    void separateConstantChains(GepNode *Node, NodeChildrenMap &NCM,
                                NodeToValueMap &Loc);
    void computeNodePlacement(NodeToValueMap &Loc);

    Value *fabricateGEP(NodeVect &NA, BasicBlock::iterator At,
                        BasicBlock *LocB);
    void getAllUsersForNode(GepNode *Node, ValueVect &Values,
                            NodeChildrenMap &NCM);
    void materialize(NodeToValueMap &Loc);

    void removeDeadCode();

    NodeVect Nodes;
    NodeToUsesMap Uses;
    NodeOrdering NodeOrder;   // Node ordering, for deterministic behavior.
    SpecificBumpPtrAllocator<GepNode> *Mem;
    LLVMContext *Ctx;
    LoopInfo *LI;
    DominatorTree *DT;
    PostDominatorTree *PDT;
    Function *Fn;
  };

} // end anonymous namespace

char HexagonCommonGEP::ID = 0;

INITIALIZE_PASS_BEGIN(HexagonCommonGEP, "hcommgep", "Hexagon Common GEP",
      false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(HexagonCommonGEP, "hcommgep", "Hexagon Common GEP",
      false, false)

namespace {

  struct GepNode {
    enum {
      None      = 0,
      Root      = 0x01,
      Internal  = 0x02,
      Used      = 0x04,
      InBounds  = 0x08
    };

    uint32_t Flags = 0;
    union {
      GepNode *Parent;
      Value *BaseVal;
    };
    Value *Idx = nullptr;
    Type *PTy = nullptr;  // Type of the pointer operand.

    GepNode() : Parent(nullptr) {}
    GepNode(const GepNode *N) : Flags(N->Flags), Idx(N->Idx), PTy(N->PTy) {
      if (Flags & Root)
        BaseVal = N->BaseVal;
      else
        Parent = N->Parent;
    }

    friend raw_ostream &operator<< (raw_ostream &OS, const GepNode &GN);
  };

  Type *next_type(Type *Ty, Value *Idx) {
    if (auto *PTy = dyn_cast<PointerType>(Ty))
      return PTy->getElementType();
    // Advance the type.
    if (!Ty->isStructTy()) {
      Type *NexTy = cast<SequentialType>(Ty)->getElementType();
      return NexTy;
    }
    // Otherwise it is a struct type.
    ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
    assert(CI && "Struct type with non-constant index");
    int64_t i = CI->getValue().getSExtValue();
    Type *NextTy = cast<StructType>(Ty)->getElementType(i);
    return NextTy;
  }

  raw_ostream &operator<< (raw_ostream &OS, const GepNode &GN) {
    OS << "{ {";
    bool Comma = false;
    if (GN.Flags & GepNode::Root) {
      OS << "root";
      Comma = true;
    }
    if (GN.Flags & GepNode::Internal) {
      if (Comma)
        OS << ',';
      OS << "internal";
      Comma = true;
    }
    if (GN.Flags & GepNode::Used) {
      if (Comma)
        OS << ',';
      OS << "used";
    }
    if (GN.Flags & GepNode::InBounds) {
      if (Comma)
        OS << ',';
      OS << "inbounds";
    }
    OS << "} ";
    if (GN.Flags & GepNode::Root)
      OS << "BaseVal:" << GN.BaseVal->getName() << '(' << GN.BaseVal << ')';
    else
      OS << "Parent:" << GN.Parent;

    OS << " Idx:";
    if (ConstantInt *CI = dyn_cast<ConstantInt>(GN.Idx))
      OS << CI->getValue().getSExtValue();
    else if (GN.Idx->hasName())
      OS << GN.Idx->getName();
    else
      OS << "<anon> =" << *GN.Idx;

    OS << " PTy:";
    if (GN.PTy->isStructTy()) {
      StructType *STy = cast<StructType>(GN.PTy);
      if (!STy->isLiteral())
        OS << GN.PTy->getStructName();
      else
        OS << "<anon-struct>:" << *STy;
    }
    else
      OS << *GN.PTy;
    OS << " }";
    return OS;
  }

  template <typename NodeContainer>
  void dump_node_container(raw_ostream &OS, const NodeContainer &S) {
    using const_iterator = typename NodeContainer::const_iterator;

    for (const_iterator I = S.begin(), E = S.end(); I != E; ++I)
      OS << *I << ' ' << **I << '\n';
  }

  raw_ostream &operator<< (raw_ostream &OS,
                           const NodeVect &S) LLVM_ATTRIBUTE_UNUSED;
  raw_ostream &operator<< (raw_ostream &OS, const NodeVect &S) {
    dump_node_container(OS, S);
    return OS;
  }

  raw_ostream &operator<< (raw_ostream &OS,
                           const NodeToUsesMap &M) LLVM_ATTRIBUTE_UNUSED;
  raw_ostream &operator<< (raw_ostream &OS, const NodeToUsesMap &M){
    using const_iterator = NodeToUsesMap::const_iterator;

    for (const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
      const UseSet &Us = I->second;
      OS << I->first << " -> #" << Us.size() << '{';
      for (UseSet::const_iterator J = Us.begin(), F = Us.end(); J != F; ++J) {
        User *R = (*J)->getUser();
        if (R->hasName())
          OS << ' ' << R->getName();
        else
          OS << " <?>(" << *R << ')';
      }
      OS << " }\n";
    }
    return OS;
  }

  struct in_set {
    in_set(const NodeSet &S) : NS(S) {}

    bool operator() (GepNode *N) const {
      return NS.find(N) != NS.end();
    }

  private:
    const NodeSet &NS;
  };

} // end anonymous namespace

inline void *operator new(size_t, SpecificBumpPtrAllocator<GepNode> &A) {
  return A.Allocate();
}

void HexagonCommonGEP::getBlockTraversalOrder(BasicBlock *Root,
      ValueVect &Order) {
  // Compute block ordering for a typical DT-based traversal of the flow
  // graph: "before visiting a block, all of its dominators must have been
  // visited".

  Order.push_back(Root);
  for (auto *DTN : children<DomTreeNode*>(DT->getNode(Root)))
    getBlockTraversalOrder(DTN->getBlock(), Order);
}

bool HexagonCommonGEP::isHandledGepForm(GetElementPtrInst *GepI) {
  // No vector GEPs.
  if (!GepI->getType()->isPointerTy())
    return false;
  // No GEPs without any indices.  (Is this possible?)
  if (GepI->idx_begin() == GepI->idx_end())
    return false;
  return true;
}

void HexagonCommonGEP::processGepInst(GetElementPtrInst *GepI,
      ValueToNodeMap &NM) {
  LLVM_DEBUG(dbgs() << "Visiting GEP: " << *GepI << '\n');
  GepNode *N = new (*Mem) GepNode;
  Value *PtrOp = GepI->getPointerOperand();
  uint32_t InBounds = GepI->isInBounds() ? GepNode::InBounds : 0;
  ValueToNodeMap::iterator F = NM.find(PtrOp);
  if (F == NM.end()) {
    N->BaseVal = PtrOp;
    N->Flags |= GepNode::Root | InBounds;
  } else {
    // If PtrOp was a GEP instruction, it must have already been processed.
    // The ValueToNodeMap entry for it is the last gep node in the generated
    // chain. Link to it here.
    N->Parent = F->second;
  }
  N->PTy = PtrOp->getType();
  N->Idx = *GepI->idx_begin();

  // Collect the list of users of this GEP instruction. Will add it to the
  // last node created for it.
  UseSet Us;
  for (Value::user_iterator UI = GepI->user_begin(), UE = GepI->user_end();
       UI != UE; ++UI) {
    // Check if this gep is used by anything other than other geps that
    // we will process.
    if (isa<GetElementPtrInst>(*UI)) {
      GetElementPtrInst *UserG = cast<GetElementPtrInst>(*UI);
      if (isHandledGepForm(UserG))
        continue;
    }
    Us.insert(&UI.getUse());
  }
  Nodes.push_back(N);
  NodeOrder.insert(N);

  // Skip the first index operand, since we only handle 0. This dereferences
  // the pointer operand.
  GepNode *PN = N;
  Type *PtrTy = cast<PointerType>(PtrOp->getType())->getElementType();
  for (User::op_iterator OI = GepI->idx_begin()+1, OE = GepI->idx_end();
       OI != OE; ++OI) {
    Value *Op = *OI;
    GepNode *Nx = new (*Mem) GepNode;
    Nx->Parent = PN;  // Link Nx to the previous node.
    Nx->Flags |= GepNode::Internal | InBounds;
    Nx->PTy = PtrTy;
    Nx->Idx = Op;
    Nodes.push_back(Nx);
    NodeOrder.insert(Nx);
    PN = Nx;

    PtrTy = next_type(PtrTy, Op);
  }

  // After last node has been created, update the use information.
  if (!Us.empty()) {
    PN->Flags |= GepNode::Used;
    Uses[PN].insert(Us.begin(), Us.end());
  }

  // Link the last node with the originating GEP instruction. This is to
  // help with linking chained GEP instructions.
  NM.insert(std::make_pair(GepI, PN));
}

void HexagonCommonGEP::collect() {
  // Establish depth-first traversal order of the dominator tree.
  ValueVect BO;
  getBlockTraversalOrder(&Fn->front(), BO);

  // The creation of gep nodes requires DT-traversal. When processing a GEP
  // instruction that uses another GEP instruction as the base pointer, the
  // gep node for the base pointer should already exist.
  ValueToNodeMap NM;
  for (ValueVect::iterator I = BO.begin(), E = BO.end(); I != E; ++I) {
    BasicBlock *B = cast<BasicBlock>(*I);
    for (BasicBlock::iterator J = B->begin(), F = B->end(); J != F; ++J) {
      if (!isa<GetElementPtrInst>(J))
        continue;
      GetElementPtrInst *GepI = cast<GetElementPtrInst>(J);
      if (isHandledGepForm(GepI))
        processGepInst(GepI, NM);
    }
  }

  LLVM_DEBUG(dbgs() << "Gep nodes after initial collection:\n" << Nodes);
}

static void invert_find_roots(const NodeVect &Nodes, NodeChildrenMap &NCM,
                              NodeVect &Roots) {
    using const_iterator = NodeVect::const_iterator;

    for (const_iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
      GepNode *N = *I;
      if (N->Flags & GepNode::Root) {
        Roots.push_back(N);
        continue;
      }
      GepNode *PN = N->Parent;
      NCM[PN].push_back(N);
    }
}

static void nodes_for_root(GepNode *Root, NodeChildrenMap &NCM,
                           NodeSet &Nodes) {
    NodeVect Work;
    Work.push_back(Root);
    Nodes.insert(Root);

    while (!Work.empty()) {
      NodeVect::iterator First = Work.begin();
      GepNode *N = *First;
      Work.erase(First);
      NodeChildrenMap::iterator CF = NCM.find(N);
      if (CF != NCM.end()) {
        Work.insert(Work.end(), CF->second.begin(), CF->second.end());
        Nodes.insert(CF->second.begin(), CF->second.end());
      }
    }
}

namespace {

  using NodeSymRel = std::set<NodeSet>;
  using NodePair = std::pair<GepNode *, GepNode *>;
  using NodePairSet = std::set<NodePair>;

} // end anonymous namespace

static const NodeSet *node_class(GepNode *N, NodeSymRel &Rel) {
    for (NodeSymRel::iterator I = Rel.begin(), E = Rel.end(); I != E; ++I)
      if (I->count(N))
        return &*I;
    return nullptr;
}

  // Create an ordered pair of GepNode pointers. The pair will be used in
  // determining equality. The only purpose of the ordering is to eliminate
  // duplication due to the commutativity of equality/non-equality.
static NodePair node_pair(GepNode *N1, GepNode *N2) {
    uintptr_t P1 = uintptr_t(N1), P2 = uintptr_t(N2);
    if (P1 <= P2)
      return std::make_pair(N1, N2);
    return std::make_pair(N2, N1);
}

static unsigned node_hash(GepNode *N) {
    // Include everything except flags and parent.
    FoldingSetNodeID ID;
    ID.AddPointer(N->Idx);
    ID.AddPointer(N->PTy);
    return ID.ComputeHash();
}

static bool node_eq(GepNode *N1, GepNode *N2, NodePairSet &Eq,
                    NodePairSet &Ne) {
    // Don't cache the result for nodes with different hashes. The hash
    // comparison is fast enough.
    if (node_hash(N1) != node_hash(N2))
      return false;

    NodePair NP = node_pair(N1, N2);
    NodePairSet::iterator FEq = Eq.find(NP);
    if (FEq != Eq.end())
      return true;
    NodePairSet::iterator FNe = Ne.find(NP);
    if (FNe != Ne.end())
      return false;
    // Not previously compared.
    bool Root1 = N1->Flags & GepNode::Root;
    bool Root2 = N2->Flags & GepNode::Root;
    NodePair P = node_pair(N1, N2);
    // If the Root flag has different values, the nodes are different.
    // If both nodes are root nodes, but their base pointers differ,
    // they are different.
    if (Root1 != Root2 || (Root1 && N1->BaseVal != N2->BaseVal)) {
      Ne.insert(P);
      return false;
    }
    // Here the root flags are identical, and for root nodes the
    // base pointers are equal, so the root nodes are equal.
    // For non-root nodes, compare their parent nodes.
    if (Root1 || node_eq(N1->Parent, N2->Parent, Eq, Ne)) {
      Eq.insert(P);
      return true;
    }
    return false;
}

void HexagonCommonGEP::common() {
  // The essence of this commoning is finding gep nodes that are equal.
  // To do this we need to compare all pairs of nodes. To save time,
  // first, partition the set of all nodes into sets of potentially equal
  // nodes, and then compare pairs from within each partition.
  using NodeSetMap = std::map<unsigned, NodeSet>;
  NodeSetMap MaybeEq;

  for (NodeVect::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
    GepNode *N = *I;
    unsigned H = node_hash(N);
    MaybeEq[H].insert(N);
  }

  // Compute the equivalence relation for the gep nodes.  Use two caches,
  // one for equality and the other for non-equality.
  NodeSymRel EqRel;  // Equality relation (as set of equivalence classes).
  NodePairSet Eq, Ne;  // Caches.
  for (NodeSetMap::iterator I = MaybeEq.begin(), E = MaybeEq.end();
       I != E; ++I) {
    NodeSet &S = I->second;
    for (NodeSet::iterator NI = S.begin(), NE = S.end(); NI != NE; ++NI) {
      GepNode *N = *NI;
      // If node already has a class, then the class must have been created
      // in a prior iteration of this loop. Since equality is transitive,
      // nothing more will be added to that class, so skip it.
      if (node_class(N, EqRel))
        continue;

      // Create a new class candidate now.
      NodeSet C;
      for (NodeSet::iterator NJ = std::next(NI); NJ != NE; ++NJ)
        if (node_eq(N, *NJ, Eq, Ne))
          C.insert(*NJ);
      // If Tmp is empty, N would be the only element in it. Don't bother
      // creating a class for it then.
      if (!C.empty()) {
        C.insert(N);  // Finalize the set before adding it to the relation.
        std::pair<NodeSymRel::iterator, bool> Ins = EqRel.insert(C);
        (void)Ins;
        assert(Ins.second && "Cannot add a class");
      }
    }
  }

  LLVM_DEBUG({
    dbgs() << "Gep node equality:\n";
    for (NodePairSet::iterator I = Eq.begin(), E = Eq.end(); I != E; ++I)
      dbgs() << "{ " << I->first << ", " << I->second << " }\n";

    dbgs() << "Gep equivalence classes:\n";
    for (NodeSymRel::iterator I = EqRel.begin(), E = EqRel.end(); I != E; ++I) {
      dbgs() << '{';
      const NodeSet &S = *I;
      for (NodeSet::const_iterator J = S.begin(), F = S.end(); J != F; ++J) {
        if (J != S.begin())
          dbgs() << ',';
        dbgs() << ' ' << *J;
      }
      dbgs() << " }\n";
    }
  });

  // Create a projection from a NodeSet to the minimal element in it.
  using ProjMap = std::map<const NodeSet *, GepNode *>;
  ProjMap PM;
  for (NodeSymRel::iterator I = EqRel.begin(), E = EqRel.end(); I != E; ++I) {
    const NodeSet &S = *I;
    GepNode *Min = *std::min_element(S.begin(), S.end(), NodeOrder);
    std::pair<ProjMap::iterator,bool> Ins = PM.insert(std::make_pair(&S, Min));
    (void)Ins;
    assert(Ins.second && "Cannot add minimal element");

    // Update the min element's flags, and user list.
    uint32_t Flags = 0;
    UseSet &MinUs = Uses[Min];
    for (NodeSet::iterator J = S.begin(), F = S.end(); J != F; ++J) {
      GepNode *N = *J;
      uint32_t NF = N->Flags;
      // If N is used, append all original values of N to the list of
      // original values of Min.
      if (NF & GepNode::Used)
        MinUs.insert(Uses[N].begin(), Uses[N].end());
      Flags |= NF;
    }
    if (MinUs.empty())
      Uses.erase(Min);

    // The collected flags should include all the flags from the min element.
    assert((Min->Flags & Flags) == Min->Flags);
    Min->Flags = Flags;
  }

  // Commoning: for each non-root gep node, replace "Parent" with the
  // selected (minimum) node from the corresponding equivalence class.
  // If a given parent does not have an equivalence class, leave it
  // unchanged (it means that it's the only element in its class).
  for (NodeVect::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
    GepNode *N = *I;
    if (N->Flags & GepNode::Root)
      continue;
    const NodeSet *PC = node_class(N->Parent, EqRel);
    if (!PC)
      continue;
    ProjMap::iterator F = PM.find(PC);
    if (F == PM.end())
      continue;
    // Found a replacement, use it.
    GepNode *Rep = F->second;
    N->Parent = Rep;
  }

  LLVM_DEBUG(dbgs() << "Gep nodes after commoning:\n" << Nodes);

  // Finally, erase the nodes that are no longer used.
  NodeSet Erase;
  for (NodeVect::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
    GepNode *N = *I;
    const NodeSet *PC = node_class(N, EqRel);
    if (!PC)
      continue;
    ProjMap::iterator F = PM.find(PC);
    if (F == PM.end())
      continue;
    if (N == F->second)
      continue;
    // Node for removal.
    Erase.insert(*I);
  }
  NodeVect::iterator NewE = remove_if(Nodes, in_set(Erase));
  Nodes.resize(std::distance(Nodes.begin(), NewE));

  LLVM_DEBUG(dbgs() << "Gep nodes after post-commoning cleanup:\n" << Nodes);
}

template <typename T>
static BasicBlock *nearest_common_dominator(DominatorTree *DT, T &Blocks) {
  LLVM_DEBUG({
    dbgs() << "NCD of {";
    for (typename T::iterator I = Blocks.begin(), E = Blocks.end(); I != E;
         ++I) {
      if (!*I)
        continue;
      BasicBlock *B = cast<BasicBlock>(*I);
      dbgs() << ' ' << B->getName();
    }
    dbgs() << " }\n";
  });

  // Allow null basic blocks in Blocks.  In such cases, return nullptr.
  typename T::iterator I = Blocks.begin(), E = Blocks.end();
  if (I == E || !*I)
    return nullptr;
  BasicBlock *Dom = cast<BasicBlock>(*I);
  while (++I != E) {
    BasicBlock *B = cast_or_null<BasicBlock>(*I);
    Dom = B ? DT->findNearestCommonDominator(Dom, B) : nullptr;
    if (!Dom)
      return nullptr;
    }
    LLVM_DEBUG(dbgs() << "computed:" << Dom->getName() << '\n');
    return Dom;
}

template <typename T>
static BasicBlock *nearest_common_dominatee(DominatorTree *DT, T &Blocks) {
    // If two blocks, A and B, dominate a block C, then A dominates B,
    // or B dominates A.
    typename T::iterator I = Blocks.begin(), E = Blocks.end();
    // Find the first non-null block.
    while (I != E && !*I)
      ++I;
    if (I == E)
      return DT->getRoot();
    BasicBlock *DomB = cast<BasicBlock>(*I);
    while (++I != E) {
      if (!*I)
        continue;
      BasicBlock *B = cast<BasicBlock>(*I);
      if (DT->dominates(B, DomB))
        continue;
      if (!DT->dominates(DomB, B))
        return nullptr;
      DomB = B;
    }
    return DomB;
}

// Find the first use in B of any value from Values. If no such use,
// return B->end().
template <typename T>
static BasicBlock::iterator first_use_of_in_block(T &Values, BasicBlock *B) {
    BasicBlock::iterator FirstUse = B->end(), BEnd = B->end();

    using iterator = typename T::iterator;

    for (iterator I = Values.begin(), E = Values.end(); I != E; ++I) {
      Value *V = *I;
      // If V is used in a PHI node, the use belongs to the incoming block,
      // not the block with the PHI node. In the incoming block, the use
      // would be considered as being at the end of it, so it cannot
      // influence the position of the first use (which is assumed to be
      // at the end to start with).
      if (isa<PHINode>(V))
        continue;
      if (!isa<Instruction>(V))
        continue;
      Instruction *In = cast<Instruction>(V);
      if (In->getParent() != B)
        continue;
      BasicBlock::iterator It = In->getIterator();
      if (std::distance(FirstUse, BEnd) < std::distance(It, BEnd))
        FirstUse = It;
    }
    return FirstUse;
}

static bool is_empty(const BasicBlock *B) {
    return B->empty() || (&*B->begin() == B->getTerminator());
}

BasicBlock *HexagonCommonGEP::recalculatePlacement(GepNode *Node,
      NodeChildrenMap &NCM, NodeToValueMap &Loc) {
  LLVM_DEBUG(dbgs() << "Loc for node:" << Node << '\n');
  // Recalculate the placement for Node, assuming that the locations of
  // its children in Loc are valid.
  // Return nullptr if there is no valid placement for Node (for example, it
  // uses an index value that is not available at the location required
  // to dominate all children, etc.).

  // Find the nearest common dominator for:
  // - all users, if the node is used, and
  // - all children.
  ValueVect Bs;
  if (Node->Flags & GepNode::Used) {
    // Append all blocks with uses of the original values to the
    // block vector Bs.
    NodeToUsesMap::iterator UF = Uses.find(Node);
    assert(UF != Uses.end() && "Used node with no use information");
    UseSet &Us = UF->second;
    for (UseSet::iterator I = Us.begin(), E = Us.end(); I != E; ++I) {
      Use *U = *I;
      User *R = U->getUser();
      if (!isa<Instruction>(R))
        continue;
      BasicBlock *PB = isa<PHINode>(R)
          ? cast<PHINode>(R)->getIncomingBlock(*U)
          : cast<Instruction>(R)->getParent();
      Bs.push_back(PB);
    }
  }
  // Append the location of each child.
  NodeChildrenMap::iterator CF = NCM.find(Node);
  if (CF != NCM.end()) {
    NodeVect &Cs = CF->second;
    for (NodeVect::iterator I = Cs.begin(), E = Cs.end(); I != E; ++I) {
      GepNode *CN = *I;
      NodeToValueMap::iterator LF = Loc.find(CN);
      // If the child is only used in GEP instructions (i.e. is not used in
      // non-GEP instructions), the nearest dominator computed for it may
      // have been null. In such case it won't have a location available.
      if (LF == Loc.end())
        continue;
      Bs.push_back(LF->second);
    }
  }

  BasicBlock *DomB = nearest_common_dominator(DT, Bs);
  if (!DomB)
    return nullptr;
  // Check if the index used by Node dominates the computed dominator.
  Instruction *IdxI = dyn_cast<Instruction>(Node->Idx);
  if (IdxI && !DT->dominates(IdxI->getParent(), DomB))
    return nullptr;

  // Avoid putting nodes into empty blocks.
  while (is_empty(DomB)) {
    DomTreeNode *N = (*DT)[DomB]->getIDom();
    if (!N)
      break;
    DomB = N->getBlock();
  }

  // Otherwise, DomB is fine. Update the location map.
  Loc[Node] = DomB;
  return DomB;
}

BasicBlock *HexagonCommonGEP::recalculatePlacementRec(GepNode *Node,
      NodeChildrenMap &NCM, NodeToValueMap &Loc) {
  LLVM_DEBUG(dbgs() << "LocRec begin for node:" << Node << '\n');
  // Recalculate the placement of Node, after recursively recalculating the
  // placements of all its children.
  NodeChildrenMap::iterator CF = NCM.find(Node);
  if (CF != NCM.end()) {
    NodeVect &Cs = CF->second;
    for (NodeVect::iterator I = Cs.begin(), E = Cs.end(); I != E; ++I)
      recalculatePlacementRec(*I, NCM, Loc);
  }
  BasicBlock *LB = recalculatePlacement(Node, NCM, Loc);
  LLVM_DEBUG(dbgs() << "LocRec end for node:" << Node << '\n');
  return LB;
}

bool HexagonCommonGEP::isInvariantIn(Value *Val, Loop *L) {
  if (isa<Constant>(Val) || isa<Argument>(Val))
    return true;
  Instruction *In = dyn_cast<Instruction>(Val);
  if (!In)
    return false;
  BasicBlock *HdrB = L->getHeader(), *DefB = In->getParent();
  return DT->properlyDominates(DefB, HdrB);
}

bool HexagonCommonGEP::isInvariantIn(GepNode *Node, Loop *L) {
  if (Node->Flags & GepNode::Root)
    if (!isInvariantIn(Node->BaseVal, L))
      return false;
  return isInvariantIn(Node->Idx, L);
}

bool HexagonCommonGEP::isInMainPath(BasicBlock *B, Loop *L) {
  BasicBlock *HB = L->getHeader();
  BasicBlock *LB = L->getLoopLatch();
  // B must post-dominate the loop header or dominate the loop latch.
  if (PDT->dominates(B, HB))
    return true;
  if (LB && DT->dominates(B, LB))
    return true;
  return false;
}

static BasicBlock *preheader(DominatorTree *DT, Loop *L) {
  if (BasicBlock *PH = L->getLoopPreheader())
    return PH;
  if (!OptSpeculate)
    return nullptr;
  DomTreeNode *DN = DT->getNode(L->getHeader());
  if (!DN)
    return nullptr;
  return DN->getIDom()->getBlock();
}

BasicBlock *HexagonCommonGEP::adjustForInvariance(GepNode *Node,
      NodeChildrenMap &NCM, NodeToValueMap &Loc) {
  // Find the "topmost" location for Node: it must be dominated by both,
  // its parent (or the BaseVal, if it's a root node), and by the index
  // value.
  ValueVect Bs;
  if (Node->Flags & GepNode::Root) {
    if (Instruction *PIn = dyn_cast<Instruction>(Node->BaseVal))
      Bs.push_back(PIn->getParent());
  } else {
    Bs.push_back(Loc[Node->Parent]);
  }
  if (Instruction *IIn = dyn_cast<Instruction>(Node->Idx))
    Bs.push_back(IIn->getParent());
  BasicBlock *TopB = nearest_common_dominatee(DT, Bs);

  // Traverse the loop nest upwards until we find a loop in which Node
  // is no longer invariant, or until we get to the upper limit of Node's
  // placement. The traversal will also stop when a suitable "preheader"
  // cannot be found for a given loop. The "preheader" may actually be
  // a regular block outside of the loop (i.e. not guarded), in which case
  // the Node will be speculated.
  // For nodes that are not in the main path of the containing loop (i.e.
  // are not executed in each iteration), do not move them out of the loop.
  BasicBlock *LocB = cast_or_null<BasicBlock>(Loc[Node]);
  if (LocB) {
    Loop *Lp = LI->getLoopFor(LocB);
    while (Lp) {
      if (!isInvariantIn(Node, Lp) || !isInMainPath(LocB, Lp))
        break;
      BasicBlock *NewLoc = preheader(DT, Lp);
      if (!NewLoc || !DT->dominates(TopB, NewLoc))
        break;
      Lp = Lp->getParentLoop();
      LocB = NewLoc;
    }
  }
  Loc[Node] = LocB;

  // Recursively compute the locations of all children nodes.
  NodeChildrenMap::iterator CF = NCM.find(Node);
  if (CF != NCM.end()) {
    NodeVect &Cs = CF->second;
    for (NodeVect::iterator I = Cs.begin(), E = Cs.end(); I != E; ++I)
      adjustForInvariance(*I, NCM, Loc);
  }
  return LocB;
}

namespace {

  struct LocationAsBlock {
    LocationAsBlock(const NodeToValueMap &L) : Map(L) {}

    const NodeToValueMap &Map;
  };

  raw_ostream &operator<< (raw_ostream &OS,
                           const LocationAsBlock &Loc) LLVM_ATTRIBUTE_UNUSED ;
  raw_ostream &operator<< (raw_ostream &OS, const LocationAsBlock &Loc) {
    for (NodeToValueMap::const_iterator I = Loc.Map.begin(), E = Loc.Map.end();
         I != E; ++I) {
      OS << I->first << " -> ";
      BasicBlock *B = cast<BasicBlock>(I->second);
      OS << B->getName() << '(' << B << ')';
      OS << '\n';
    }
    return OS;
  }

  inline bool is_constant(GepNode *N) {
    return isa<ConstantInt>(N->Idx);
  }

} // end anonymous namespace

void HexagonCommonGEP::separateChainForNode(GepNode *Node, Use *U,
      NodeToValueMap &Loc) {
  User *R = U->getUser();
  LLVM_DEBUG(dbgs() << "Separating chain for node (" << Node << ") user: " << *R
                    << '\n');
  BasicBlock *PB = cast<Instruction>(R)->getParent();

  GepNode *N = Node;
  GepNode *C = nullptr, *NewNode = nullptr;
  while (is_constant(N) && !(N->Flags & GepNode::Root)) {
    // XXX if (single-use) dont-replicate;
    GepNode *NewN = new (*Mem) GepNode(N);
    Nodes.push_back(NewN);
    Loc[NewN] = PB;

    if (N == Node)
      NewNode = NewN;
    NewN->Flags &= ~GepNode::Used;
    if (C)
      C->Parent = NewN;
    C = NewN;
    N = N->Parent;
  }
  if (!NewNode)
    return;

  // Move over all uses that share the same user as U from Node to NewNode.
  NodeToUsesMap::iterator UF = Uses.find(Node);
  assert(UF != Uses.end());
  UseSet &Us = UF->second;
  UseSet NewUs;
  for (Use *U : Us) {
    if (U->getUser() == R)
      NewUs.insert(U);
  }
  for (Use *U : NewUs)
    Us.remove(U); // erase takes an iterator.

  if (Us.empty()) {
    Node->Flags &= ~GepNode::Used;
    Uses.erase(UF);
  }

  // Should at least have U in NewUs.
  NewNode->Flags |= GepNode::Used;
  LLVM_DEBUG(dbgs() << "new node: " << NewNode << "  " << *NewNode << '\n');
  assert(!NewUs.empty());
  Uses[NewNode] = NewUs;
}

void HexagonCommonGEP::separateConstantChains(GepNode *Node,
      NodeChildrenMap &NCM, NodeToValueMap &Loc) {
  // First approximation: extract all chains.
  NodeSet Ns;
  nodes_for_root(Node, NCM, Ns);

  LLVM_DEBUG(dbgs() << "Separating constant chains for node: " << Node << '\n');
  // Collect all used nodes together with the uses from loads and stores,
  // where the GEP node could be folded into the load/store instruction.
  NodeToUsesMap FNs; // Foldable nodes.
  for (NodeSet::iterator I = Ns.begin(), E = Ns.end(); I != E; ++I) {
    GepNode *N = *I;
    if (!(N->Flags & GepNode::Used))
      continue;
    NodeToUsesMap::iterator UF = Uses.find(N);
    assert(UF != Uses.end());
    UseSet &Us = UF->second;
    // Loads/stores that use the node N.
    UseSet LSs;
    for (UseSet::iterator J = Us.begin(), F = Us.end(); J != F; ++J) {
      Use *U = *J;
      User *R = U->getUser();
      // We're interested in uses that provide the address. It can happen
      // that the value may also be provided via GEP, but we won't handle
      // those cases here for now.
      if (LoadInst *Ld = dyn_cast<LoadInst>(R)) {
        unsigned PtrX = LoadInst::getPointerOperandIndex();
        if (&Ld->getOperandUse(PtrX) == U)
          LSs.insert(U);
      } else if (StoreInst *St = dyn_cast<StoreInst>(R)) {
        unsigned PtrX = StoreInst::getPointerOperandIndex();
        if (&St->getOperandUse(PtrX) == U)
          LSs.insert(U);
      }
    }
    // Even if the total use count is 1, separating the chain may still be
    // beneficial, since the constant chain may be longer than the GEP alone
    // would be (e.g. if the parent node has a constant index and also has
    // other children).
    if (!LSs.empty())
      FNs.insert(std::make_pair(N, LSs));
  }

  LLVM_DEBUG(dbgs() << "Nodes with foldable users:\n" << FNs);

  for (NodeToUsesMap::iterator I = FNs.begin(), E = FNs.end(); I != E; ++I) {
    GepNode *N = I->first;
    UseSet &Us = I->second;
    for (UseSet::iterator J = Us.begin(), F = Us.end(); J != F; ++J)
      separateChainForNode(N, *J, Loc);
  }
}

void HexagonCommonGEP::computeNodePlacement(NodeToValueMap &Loc) {
  // Compute the inverse of the Node.Parent links. Also, collect the set
  // of root nodes.
  NodeChildrenMap NCM;
  NodeVect Roots;
  invert_find_roots(Nodes, NCM, Roots);

  // Compute the initial placement determined by the users' locations, and
  // the locations of the child nodes.
  for (NodeVect::iterator I = Roots.begin(), E = Roots.end(); I != E; ++I)
    recalculatePlacementRec(*I, NCM, Loc);

  LLVM_DEBUG(dbgs() << "Initial node placement:\n" << LocationAsBlock(Loc));

  if (OptEnableInv) {
    for (NodeVect::iterator I = Roots.begin(), E = Roots.end(); I != E; ++I)
      adjustForInvariance(*I, NCM, Loc);

    LLVM_DEBUG(dbgs() << "Node placement after adjustment for invariance:\n"
                      << LocationAsBlock(Loc));
  }
  if (OptEnableConst) {
    for (NodeVect::iterator I = Roots.begin(), E = Roots.end(); I != E; ++I)
      separateConstantChains(*I, NCM, Loc);
  }
  LLVM_DEBUG(dbgs() << "Node use information:\n" << Uses);

  // At the moment, there is no further refinement of the initial placement.
  // Such a refinement could include splitting the nodes if they are placed
  // too far from some of its users.

  LLVM_DEBUG(dbgs() << "Final node placement:\n" << LocationAsBlock(Loc));
}

Value *HexagonCommonGEP::fabricateGEP(NodeVect &NA, BasicBlock::iterator At,
      BasicBlock *LocB) {
  LLVM_DEBUG(dbgs() << "Fabricating GEP in " << LocB->getName()
                    << " for nodes:\n"
                    << NA);
  unsigned Num = NA.size();
  GepNode *RN = NA[0];
  assert((RN->Flags & GepNode::Root) && "Creating GEP for non-root");

  GetElementPtrInst *NewInst = nullptr;
  Value *Input = RN->BaseVal;
  Value **IdxList = new Value*[Num+1];
  unsigned nax = 0;
  do {
    unsigned IdxC = 0;
    // If the type of the input of the first node is not a pointer,
    // we need to add an artificial i32 0 to the indices (because the
    // actual input in the IR will be a pointer).
    if (!NA[nax]->PTy->isPointerTy()) {
      Type *Int32Ty = Type::getInt32Ty(*Ctx);
      IdxList[IdxC++] = ConstantInt::get(Int32Ty, 0);
    }

    // Keep adding indices from NA until we have to stop and generate
    // an "intermediate" GEP.
    while (++nax <= Num) {
      GepNode *N = NA[nax-1];
      IdxList[IdxC++] = N->Idx;
      if (nax < Num) {
        // We have to stop, if the expected type of the output of this node
        // is not the same as the input type of the next node.
        Type *NextTy = next_type(N->PTy, N->Idx);
        if (NextTy != NA[nax]->PTy)
          break;
      }
    }
    ArrayRef<Value*> A(IdxList, IdxC);
    Type *InpTy = Input->getType();
    Type *ElTy = cast<PointerType>(InpTy->getScalarType())->getElementType();
    NewInst = GetElementPtrInst::Create(ElTy, Input, A, "cgep", &*At);
    NewInst->setIsInBounds(RN->Flags & GepNode::InBounds);
    LLVM_DEBUG(dbgs() << "new GEP: " << *NewInst << '\n');
    Input = NewInst;
  } while (nax <= Num);

  delete[] IdxList;
  return NewInst;
}

void HexagonCommonGEP::getAllUsersForNode(GepNode *Node, ValueVect &Values,
      NodeChildrenMap &NCM) {
  NodeVect Work;
  Work.push_back(Node);

  while (!Work.empty()) {
    NodeVect::iterator First = Work.begin();
    GepNode *N = *First;
    Work.erase(First);
    if (N->Flags & GepNode::Used) {
      NodeToUsesMap::iterator UF = Uses.find(N);
      assert(UF != Uses.end() && "No use information for used node");
      UseSet &Us = UF->second;
      for (UseSet::iterator I = Us.begin(), E = Us.end(); I != E; ++I)
        Values.push_back((*I)->getUser());
    }
    NodeChildrenMap::iterator CF = NCM.find(N);
    if (CF != NCM.end()) {
      NodeVect &Cs = CF->second;
      Work.insert(Work.end(), Cs.begin(), Cs.end());
    }
  }
}

void HexagonCommonGEP::materialize(NodeToValueMap &Loc) {
  LLVM_DEBUG(dbgs() << "Nodes before materialization:\n" << Nodes << '\n');
  NodeChildrenMap NCM;
  NodeVect Roots;
  // Compute the inversion again, since computing placement could alter
  // "parent" relation between nodes.
  invert_find_roots(Nodes, NCM, Roots);

  while (!Roots.empty()) {
    NodeVect::iterator First = Roots.begin();
    GepNode *Root = *First, *Last = *First;
    Roots.erase(First);

    NodeVect NA;  // Nodes to assemble.
    // Append to NA all child nodes up to (and including) the first child
    // that:
    // (1) has more than 1 child, or
    // (2) is used, or
    // (3) has a child located in a different block.
    bool LastUsed = false;
    unsigned LastCN = 0;
    // The location may be null if the computation failed (it can legitimately
    // happen for nodes created from dead GEPs).
    Value *LocV = Loc[Last];
    if (!LocV)
      continue;
    BasicBlock *LastB = cast<BasicBlock>(LocV);
    do {
      NA.push_back(Last);
      LastUsed = (Last->Flags & GepNode::Used);
      if (LastUsed)
        break;
      NodeChildrenMap::iterator CF = NCM.find(Last);
      LastCN = (CF != NCM.end()) ? CF->second.size() : 0;
      if (LastCN != 1)
        break;
      GepNode *Child = CF->second.front();
      BasicBlock *ChildB = cast_or_null<BasicBlock>(Loc[Child]);
      if (ChildB != nullptr && LastB != ChildB)
        break;
      Last = Child;
    } while (true);

    BasicBlock::iterator InsertAt = LastB->getTerminator()->getIterator();
    if (LastUsed || LastCN > 0) {
      ValueVect Urs;
      getAllUsersForNode(Root, Urs, NCM);
      BasicBlock::iterator FirstUse = first_use_of_in_block(Urs, LastB);
      if (FirstUse != LastB->end())
        InsertAt = FirstUse;
    }

    // Generate a new instruction for NA.
    Value *NewInst = fabricateGEP(NA, InsertAt, LastB);

    // Convert all the children of Last node into roots, and append them
    // to the Roots list.
    if (LastCN > 0) {
      NodeVect &Cs = NCM[Last];
      for (NodeVect::iterator I = Cs.begin(), E = Cs.end(); I != E; ++I) {
        GepNode *CN = *I;
        CN->Flags &= ~GepNode::Internal;
        CN->Flags |= GepNode::Root;
        CN->BaseVal = NewInst;
        Roots.push_back(CN);
      }
    }

    // Lastly, if the Last node was used, replace all uses with the new GEP.
    // The uses reference the original GEP values.
    if (LastUsed) {
      NodeToUsesMap::iterator UF = Uses.find(Last);
      assert(UF != Uses.end() && "No use information found");
      UseSet &Us = UF->second;
      for (UseSet::iterator I = Us.begin(), E = Us.end(); I != E; ++I) {
        Use *U = *I;
        U->set(NewInst);
      }
    }
  }
}

void HexagonCommonGEP::removeDeadCode() {
  ValueVect BO;
  BO.push_back(&Fn->front());

  for (unsigned i = 0; i < BO.size(); ++i) {
    BasicBlock *B = cast<BasicBlock>(BO[i]);
    for (auto DTN : children<DomTreeNode*>(DT->getNode(B)))
      BO.push_back(DTN->getBlock());
  }

  for (unsigned i = BO.size(); i > 0; --i) {
    BasicBlock *B = cast<BasicBlock>(BO[i-1]);
    BasicBlock::InstListType &IL = B->getInstList();

    using reverse_iterator = BasicBlock::InstListType::reverse_iterator;

    ValueVect Ins;
    for (reverse_iterator I = IL.rbegin(), E = IL.rend(); I != E; ++I)
      Ins.push_back(&*I);
    for (ValueVect::iterator I = Ins.begin(), E = Ins.end(); I != E; ++I) {
      Instruction *In = cast<Instruction>(*I);
      if (isInstructionTriviallyDead(In))
        In->eraseFromParent();
    }
  }
}

bool HexagonCommonGEP::runOnFunction(Function &F) {
  if (skipFunction(F))
    return false;

  // For now bail out on C++ exception handling.
  for (Function::iterator A = F.begin(), Z = F.end(); A != Z; ++A)
    for (BasicBlock::iterator I = A->begin(), E = A->end(); I != E; ++I)
      if (isa<InvokeInst>(I) || isa<LandingPadInst>(I))
        return false;

  Fn = &F;
  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
  PDT = &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
  Ctx = &F.getContext();

  Nodes.clear();
  Uses.clear();
  NodeOrder.clear();

  SpecificBumpPtrAllocator<GepNode> Allocator;
  Mem = &Allocator;

  collect();
  common();

  NodeToValueMap Loc;
  computeNodePlacement(Loc);
  materialize(Loc);
  removeDeadCode();

#ifdef EXPENSIVE_CHECKS
  // Run this only when expensive checks are enabled.
  verifyFunction(F);
#endif
  return true;
}

namespace llvm {

  FunctionPass *createHexagonCommonGEP() {
    return new HexagonCommonGEP();
  }

} // end namespace llvm