lib/Bitcode/Writer/ValueEnumerator.cpp

   1 //===- ValueEnumerator.cpp - Number values and types for bitcode writer ---===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the ValueEnumerator class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "ValueEnumerator.h"
  14 #include "llvm/ADT/DenseMap.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/Config/llvm-config.h"
  17 #include "llvm/IR/Argument.h"
  18 #include "llvm/IR/Attributes.h"
  19 #include "llvm/IR/BasicBlock.h"
  20 #include "llvm/IR/Constant.h"
  21 #include "llvm/IR/DebugInfoMetadata.h"
  22 #include "llvm/IR/DerivedTypes.h"
  23 #include "llvm/IR/Function.h"
  24 #include "llvm/IR/GlobalAlias.h"
  25 #include "llvm/IR/GlobalIFunc.h"
  26 #include "llvm/IR/GlobalObject.h"
  27 #include "llvm/IR/GlobalValue.h"
  28 #include "llvm/IR/GlobalVariable.h"
  29 #include "llvm/IR/Instruction.h"
  30 #include "llvm/IR/Instructions.h"
  31 #include "llvm/IR/Metadata.h"
  32 #include "llvm/IR/Module.h"
  33 #include "llvm/IR/Type.h"
  34 #include "llvm/IR/Use.h"
  35 #include "llvm/IR/UseListOrder.h"
  36 #include "llvm/IR/User.h"
  37 #include "llvm/IR/Value.h"
  38 #include "llvm/IR/ValueSymbolTable.h"
  39 #include "llvm/Support/Casting.h"
  40 #include "llvm/Support/Compiler.h"
  41 #include "llvm/Support/Debug.h"
  42 #include "llvm/Support/MathExtras.h"
  43 #include "llvm/Support/raw_ostream.h"
  44 #include <algorithm>
  45 #include <cassert>
  46 #include <cstddef>
  47 #include <iterator>
  48 #include <tuple>
  49 #include <utility>
  50 #include <vector>
  51
  52 using namespace llvm;
  53
  54 namespace {
  55
  56 struct OrderMap {
  57   DenseMap<const Value *, std::pair<unsigned, bool>> IDs;
  58   unsigned LastGlobalConstantID = 0;
  59   unsigned LastGlobalValueID = 0;
  60
  61   OrderMap() = default;
  62
  63   bool isGlobalConstant(unsigned ID) const {
  64     return ID <= LastGlobalConstantID;
  65   }
  66
  67   bool isGlobalValue(unsigned ID) const {
  68     return ID <= LastGlobalValueID && !isGlobalConstant(ID);
  69   }
  70
  71   unsigned size() const { return IDs.size(); }
  72   std::pair<unsigned, bool> &operator[](const Value *V) { return IDs[V]; }
  73
  74   std::pair<unsigned, bool> lookup(const Value *V) const {
  75     return IDs.lookup(V);
  76   }
  77
  78   void index(const Value *V) {
  79     // Explicitly sequence get-size and insert-value operations to avoid UB.
  80     unsigned ID = IDs.size() + 1;
  81     IDs[V].first = ID;
  82   }
  83 };
  84
  85 } // end anonymous namespace
  86
  87 static void orderValue(const Value *V, OrderMap &OM) {
  88   if (OM.lookup(V).first)
  89     return;
  90
  91   if (const Constant *C = dyn_cast<Constant>(V))
  92     if (C->getNumOperands() && !isa<GlobalValue>(C))
  93       for (const Value *Op : C->operands())
  94         if (!isa<BasicBlock>(Op) && !isa<GlobalValue>(Op))
  95           orderValue(Op, OM);
  96
  97   // Note: we cannot cache this lookup above, since inserting into the map
  98   // changes the map's size, and thus affects the other IDs.
  99   OM.index(V);
 100 }
 101
 102 static OrderMap orderModule(const Module &M) {
 103   // This needs to match the order used by ValueEnumerator::ValueEnumerator()
 104   // and ValueEnumerator::incorporateFunction().
 105   OrderMap OM;
 106
 107   // In the reader, initializers of GlobalValues are set *after* all the
 108   // globals have been read.  Rather than awkwardly modeling this behaviour
 109   // directly in predictValueUseListOrderImpl(), just assign IDs to
 110   // initializers of GlobalValues before GlobalValues themselves to model this
 111   // implicitly.
 112   for (const GlobalVariable &G : M.globals())
 113     if (G.hasInitializer())
 114       if (!isa<GlobalValue>(G.getInitializer()))
 115         orderValue(G.getInitializer(), OM);
 116   for (const GlobalAlias &A : M.aliases())
 117     if (!isa<GlobalValue>(A.getAliasee()))
 118       orderValue(A.getAliasee(), OM);
 119   for (const GlobalIFunc &I : M.ifuncs())
 120     if (!isa<GlobalValue>(I.getResolver()))
 121       orderValue(I.getResolver(), OM);
 122   for (const Function &F : M) {
 123     for (const Use &U : F.operands())
 124       if (!isa<GlobalValue>(U.get()))
 125         orderValue(U.get(), OM);
 126   }
 127   OM.LastGlobalConstantID = OM.size();
 128
 129   // Initializers of GlobalValues are processed in
 130   // BitcodeReader::ResolveGlobalAndAliasInits().  Match the order there rather
 131   // than ValueEnumerator, and match the code in predictValueUseListOrderImpl()
 132   // by giving IDs in reverse order.
 133   //
 134   // Since GlobalValues never reference each other directly (just through
 135   // initializers), their relative IDs only matter for determining order of
 136   // uses in their initializers.
 137   for (const Function &F : M)
 138     orderValue(&F, OM);
 139   for (const GlobalAlias &A : M.aliases())
 140     orderValue(&A, OM);
 141   for (const GlobalIFunc &I : M.ifuncs())
 142     orderValue(&I, OM);
 143   for (const GlobalVariable &G : M.globals())
 144     orderValue(&G, OM);
 145   OM.LastGlobalValueID = OM.size();
 146
 147   for (const Function &F : M) {
 148     if (F.isDeclaration())
 149       continue;
 150     // Here we need to match the union of ValueEnumerator::incorporateFunction()
 151     // and WriteFunction().  Basic blocks are implicitly declared before
 152     // anything else (by declaring their size).
 153     for (const BasicBlock &BB : F)
 154       orderValue(&BB, OM);
 155     for (const Argument &A : F.args())
 156       orderValue(&A, OM);
 157     for (const BasicBlock &BB : F)
 158       for (const Instruction &I : BB)
 159         for (const Value *Op : I.operands())
 160           if ((isa<Constant>(*Op) && !isa<GlobalValue>(*Op)) ||
 161               isa<InlineAsm>(*Op))
 162             orderValue(Op, OM);
 163     for (const BasicBlock &BB : F)
 164       for (const Instruction &I : BB)
 165         orderValue(&I, OM);
 166   }
 167   return OM;
 168 }
 169
 170 static void predictValueUseListOrderImpl(const Value *V, const Function *F,
 171                                          unsigned ID, const OrderMap &OM,
 172                                          UseListOrderStack &Stack) {
 173   // Predict use-list order for this one.
 174   using Entry = std::pair<const Use *, unsigned>;
 175   SmallVector<Entry, 64> List;
 176   for (const Use &U : V->uses())
 177     // Check if this user will be serialized.
 178     if (OM.lookup(U.getUser()).first)
 179       List.push_back(std::make_pair(&U, List.size()));
 180
 181   if (List.size() < 2)
 182     // We may have lost some users.
 183     return;
 184
 185   bool IsGlobalValue = OM.isGlobalValue(ID);
 186   llvm::sort(List, [&](const Entry &L, const Entry &R) {
 187     const Use *LU = L.first;
 188     const Use *RU = R.first;
 189     if (LU == RU)
 190       return false;
 191
 192     auto LID = OM.lookup(LU->getUser()).first;
 193     auto RID = OM.lookup(RU->getUser()).first;
 194
 195     // Global values are processed in reverse order.
 196     //
 197     // Moreover, initializers of GlobalValues are set *after* all the globals
 198     // have been read (despite having earlier IDs).  Rather than awkwardly
 199     // modeling this behaviour here, orderModule() has assigned IDs to
 200     // initializers of GlobalValues before GlobalValues themselves.
 201     if (OM.isGlobalValue(LID) && OM.isGlobalValue(RID))
 202       return LID < RID;
 203
 204     // If ID is 4, then expect: 7 6 5 1 2 3.
 205     if (LID < RID) {
 206       if (RID <= ID)
 207         if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 208           return true;
 209       return false;
 210     }
 211     if (RID < LID) {
 212       if (LID <= ID)
 213         if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 214           return false;
 215       return true;
 216     }
 217
 218     // LID and RID are equal, so we have different operands of the same user.
 219     // Assume operands are added in order for all instructions.
 220     if (LID <= ID)
 221       if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 222         return LU->getOperandNo() < RU->getOperandNo();
 223     return LU->getOperandNo() > RU->getOperandNo();
 224   });
 225
 226   if (std::is_sorted(
 227           List.begin(), List.end(),
 228           [](const Entry &L, const Entry &R) { return L.second < R.second; }))
 229     // Order is already correct.
 230     return;
 231
 232   // Store the shuffle.
 233   Stack.emplace_back(V, F, List.size());
 234   assert(List.size() == Stack.back().Shuffle.size() && "Wrong size");
 235   for (size_t I = 0, E = List.size(); I != E; ++I)
 236     Stack.back().Shuffle[I] = List[I].second;
 237 }
 238
 239 static void predictValueUseListOrder(const Value *V, const Function *F,
 240                                      OrderMap &OM, UseListOrderStack &Stack) {
 241   auto &IDPair = OM[V];
 242   assert(IDPair.first && "Unmapped value");
 243   if (IDPair.second)
 244     // Already predicted.
 245     return;
 246
 247   // Do the actual prediction.
 248   IDPair.second = true;
 249   if (!V->use_empty() && std::next(V->use_begin()) != V->use_end())
 250     predictValueUseListOrderImpl(V, F, IDPair.first, OM, Stack);
 251
 252   // Recursive descent into constants.
 253   if (const Constant *C = dyn_cast<Constant>(V))
 254     if (C->getNumOperands()) // Visit GlobalValues.
 255       for (const Value *Op : C->operands())
 256         if (isa<Constant>(Op)) // Visit GlobalValues.
 257           predictValueUseListOrder(Op, F, OM, Stack);
 258 }
 259
 260 static UseListOrderStack predictUseListOrder(const Module &M) {
 261   OrderMap OM = orderModule(M);
 262
 263   // Use-list orders need to be serialized after all the users have been added
 264   // to a value, or else the shuffles will be incomplete.  Store them per
 265   // function in a stack.
 266   //
 267   // Aside from function order, the order of values doesn't matter much here.
 268   UseListOrderStack Stack;
 269
 270   // We want to visit the functions backward now so we can list function-local
 271   // constants in the last Function they're used in.  Module-level constants
 272   // have already been visited above.
 273   for (auto I = M.rbegin(), E = M.rend(); I != E; ++I) {
 274     const Function &F = *I;
 275     if (F.isDeclaration())
 276       continue;
 277     for (const BasicBlock &BB : F)
 278       predictValueUseListOrder(&BB, &F, OM, Stack);
 279     for (const Argument &A : F.args())
 280       predictValueUseListOrder(&A, &F, OM, Stack);
 281     for (const BasicBlock &BB : F)
 282       for (const Instruction &I : BB)
 283         for (const Value *Op : I.operands())
 284           if (isa<Constant>(*Op) || isa<InlineAsm>(*Op)) // Visit GlobalValues.
 285             predictValueUseListOrder(Op, &F, OM, Stack);
 286     for (const BasicBlock &BB : F)
 287       for (const Instruction &I : BB)
 288         predictValueUseListOrder(&I, &F, OM, Stack);
 289   }
 290
 291   // Visit globals last, since the module-level use-list block will be seen
 292   // before the function bodies are processed.
 293   for (const GlobalVariable &G : M.globals())
 294     predictValueUseListOrder(&G, nullptr, OM, Stack);
 295   for (const Function &F : M)
 296     predictValueUseListOrder(&F, nullptr, OM, Stack);
 297   for (const GlobalAlias &A : M.aliases())
 298     predictValueUseListOrder(&A, nullptr, OM, Stack);
 299   for (const GlobalIFunc &I : M.ifuncs())
 300     predictValueUseListOrder(&I, nullptr, OM, Stack);
 301   for (const GlobalVariable &G : M.globals())
 302     if (G.hasInitializer())
 303       predictValueUseListOrder(G.getInitializer(), nullptr, OM, Stack);
 304   for (const GlobalAlias &A : M.aliases())
 305     predictValueUseListOrder(A.getAliasee(), nullptr, OM, Stack);
 306   for (const GlobalIFunc &I : M.ifuncs())
 307     predictValueUseListOrder(I.getResolver(), nullptr, OM, Stack);
 308   for (const Function &F : M) {
 309     for (const Use &U : F.operands())
 310       predictValueUseListOrder(U.get(), nullptr, OM, Stack);
 311   }
 312
 313   return Stack;
 314 }
 315
 316 static bool isIntOrIntVectorValue(const std::pair<const Value*, unsigned> &V) {
 317   return V.first->getType()->isIntOrIntVectorTy();
 318 }
 319
 320 ValueEnumerator::ValueEnumerator(const Module &M,
 321                                  bool ShouldPreserveUseListOrder)
 322     : ShouldPreserveUseListOrder(ShouldPreserveUseListOrder) {
 323   if (ShouldPreserveUseListOrder)
 324     UseListOrders = predictUseListOrder(M);
 325
 326   // Enumerate the global variables.
 327   for (const GlobalVariable &GV : M.globals())
 328     EnumerateValue(&GV);
 329
 330   // Enumerate the functions.
 331   for (const Function & F : M) {
 332     EnumerateValue(&F);
 333     EnumerateAttributes(F.getAttributes());
 334   }
 335
 336   // Enumerate the aliases.
 337   for (const GlobalAlias &GA : M.aliases())
 338     EnumerateValue(&GA);
 339
 340   // Enumerate the ifuncs.
 341   for (const GlobalIFunc &GIF : M.ifuncs())
 342     EnumerateValue(&GIF);
 343
 344   // Remember what is the cutoff between globalvalue's and other constants.
 345   unsigned FirstConstant = Values.size();
 346
 347   // Enumerate the global variable initializers and attributes.
 348   for (const GlobalVariable &GV : M.globals()) {
 349     if (GV.hasInitializer())
 350       EnumerateValue(GV.getInitializer());
 351     if (GV.hasAttributes())
 352       EnumerateAttributes(GV.getAttributesAsList(AttributeList::FunctionIndex));
 353   }
 354
 355   // Enumerate the aliasees.
 356   for (const GlobalAlias &GA : M.aliases())
 357     EnumerateValue(GA.getAliasee());
 358
 359   // Enumerate the ifunc resolvers.
 360   for (const GlobalIFunc &GIF : M.ifuncs())
 361     EnumerateValue(GIF.getResolver());
 362
 363   // Enumerate any optional Function data.
 364   for (const Function &F : M)
 365     for (const Use &U : F.operands())
 366       EnumerateValue(U.get());
 367
 368   // Enumerate the metadata type.
 369   //
 370   // TODO: Move this to ValueEnumerator::EnumerateOperandType() once bitcode
 371   // only encodes the metadata type when it's used as a value.
 372   EnumerateType(Type::getMetadataTy(M.getContext()));
 373
 374   // Insert constants and metadata that are named at module level into the slot
 375   // pool so that the module symbol table can refer to them...
 376   EnumerateValueSymbolTable(M.getValueSymbolTable());
 377   EnumerateNamedMetadata(M);
 378
 379   SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
 380   for (const GlobalVariable &GV : M.globals()) {
 381     MDs.clear();
 382     GV.getAllMetadata(MDs);
 383     for (const auto &I : MDs)
 384       // FIXME: Pass GV to EnumerateMetadata and arrange for the bitcode writer
 385       // to write metadata to the global variable's own metadata block
 386       // (PR28134).
 387       EnumerateMetadata(nullptr, I.second);
 388   }
 389
 390   // Enumerate types used by function bodies and argument lists.
 391   for (const Function &F : M) {
 392     for (const Argument &A : F.args())
 393       EnumerateType(A.getType());
 394
 395     // Enumerate metadata attached to this function.
 396     MDs.clear();
 397     F.getAllMetadata(MDs);
 398     for (const auto &I : MDs)
 399       EnumerateMetadata(F.isDeclaration() ? nullptr : &F, I.second);
 400
 401     for (const BasicBlock &BB : F)
 402       for (const Instruction &I : BB) {
 403         for (const Use &Op : I.operands()) {
 404           auto *MD = dyn_cast<MetadataAsValue>(&Op);
 405           if (!MD) {
 406             EnumerateOperandType(Op);
 407             continue;
 408           }
 409
 410           // Local metadata is enumerated during function-incorporation.
 411           if (isa<LocalAsMetadata>(MD->getMetadata()))
 412             continue;
 413
 414           EnumerateMetadata(&F, MD->getMetadata());
 415         }
 416         EnumerateType(I.getType());
 417         if (const auto *Call = dyn_cast<CallBase>(&I))
 418           EnumerateAttributes(Call->getAttributes());
 419
 420         // Enumerate metadata attached with this instruction.
 421         MDs.clear();
 422         I.getAllMetadataOtherThanDebugLoc(MDs);
 423         for (unsigned i = 0, e = MDs.size(); i != e; ++i)
 424           EnumerateMetadata(&F, MDs[i].second);
 425
 426         // Don't enumerate the location directly -- it has a special record
 427         // type -- but enumerate its operands.
 428         if (DILocation *L = I.getDebugLoc())
 429           for (const Metadata *Op : L->operands())
 430             EnumerateMetadata(&F, Op);
 431       }
 432   }
 433
 434   // Optimize constant ordering.
 435   OptimizeConstants(FirstConstant, Values.size());
 436
 437   // Organize metadata ordering.
 438   organizeMetadata();
 439 }
 440
 441 unsigned ValueEnumerator::getInstructionID(const Instruction *Inst) const {
 442   InstructionMapType::const_iterator I = InstructionMap.find(Inst);
 443   assert(I != InstructionMap.end() && "Instruction is not mapped!");
 444   return I->second;
 445 }
 446
 447 unsigned ValueEnumerator::getComdatID(const Comdat *C) const {
 448   unsigned ComdatID = Comdats.idFor(C);
 449   assert(ComdatID && "Comdat not found!");
 450   return ComdatID;
 451 }
 452
 453 void ValueEnumerator::setInstructionID(const Instruction *I) {
 454   InstructionMap[I] = InstructionCount++;
 455 }
 456
 457 unsigned ValueEnumerator::getValueID(const Value *V) const {
 458   if (auto *MD = dyn_cast<MetadataAsValue>(V))
 459     return getMetadataID(MD->getMetadata());
 460
 461   ValueMapType::const_iterator I = ValueMap.find(V);
 462   assert(I != ValueMap.end() && "Value not in slotcalculator!");
 463   return I->second-1;
 464 }
 465
 466 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 467 LLVM_DUMP_METHOD void ValueEnumerator::dump() const {
 468   print(dbgs(), ValueMap, "Default");
 469   dbgs() << '\n';
 470   print(dbgs(), MetadataMap, "MetaData");
 471   dbgs() << '\n';
 472 }
 473 #endif
 474
 475 void ValueEnumerator::print(raw_ostream &OS, const ValueMapType &Map,
 476                             const char *Name) const {
 477   OS << "Map Name: " << Name << "\n";
 478   OS << "Size: " << Map.size() << "\n";
 479   for (ValueMapType::const_iterator I = Map.begin(),
 480          E = Map.end(); I != E; ++I) {
 481     const Value *V = I->first;
 482     if (V->hasName())
 483       OS << "Value: " << V->getName();
 484     else
 485       OS << "Value: [null]\n";
 486     V->print(errs());
 487     errs() << '\n';
 488
 489     OS << " Uses(" << V->getNumUses() << "):";
 490     for (const Use &U : V->uses()) {
 491       if (&U != &*V->use_begin())
 492         OS << ",";
 493       if(U->hasName())
 494         OS << " " << U->getName();
 495       else
 496         OS << " [null]";
 497
 498     }
 499     OS <<  "\n\n";
 500   }
 501 }
 502
 503 void ValueEnumerator::print(raw_ostream &OS, const MetadataMapType &Map,
 504                             const char *Name) const {
 505   OS << "Map Name: " << Name << "\n";
 506   OS << "Size: " << Map.size() << "\n";
 507   for (auto I = Map.begin(), E = Map.end(); I != E; ++I) {
 508     const Metadata *MD = I->first;
 509     OS << "Metadata: slot = " << I->second.ID << "\n";
 510     OS << "Metadata: function = " << I->second.F << "\n";
 511     MD->print(OS);
 512     OS << "\n";
 513   }
 514 }
 515
 516 /// OptimizeConstants - Reorder constant pool for denser encoding.
 517 void ValueEnumerator::OptimizeConstants(unsigned CstStart, unsigned CstEnd) {
 518   if (CstStart == CstEnd || CstStart+1 == CstEnd) return;
 519
 520   if (ShouldPreserveUseListOrder)
 521     // Optimizing constants makes the use-list order difficult to predict.
 522     // Disable it for now when trying to preserve the order.
 523     return;
 524
 525   std::stable_sort(Values.begin() + CstStart, Values.begin() + CstEnd,
 526                    [this](const std::pair<const Value *, unsigned> &LHS,
 527                           const std::pair<const Value *, unsigned> &RHS) {
 528     // Sort by plane.
 529     if (LHS.first->getType() != RHS.first->getType())
 530       return getTypeID(LHS.first->getType()) < getTypeID(RHS.first->getType());
 531     // Then by frequency.
 532     return LHS.second > RHS.second;
 533   });
 534
 535   // Ensure that integer and vector of integer constants are at the start of the
 536   // constant pool.  This is important so that GEP structure indices come before
 537   // gep constant exprs.
 538   std::stable_partition(Values.begin() + CstStart, Values.begin() + CstEnd,
 539                         isIntOrIntVectorValue);
 540
 541   // Rebuild the modified portion of ValueMap.
 542   for (; CstStart != CstEnd; ++CstStart)
 543     ValueMap[Values[CstStart].first] = CstStart+1;
 544 }
 545
 546 /// EnumerateValueSymbolTable - Insert all of the values in the specified symbol
 547 /// table into the values table.
 548 void ValueEnumerator::EnumerateValueSymbolTable(const ValueSymbolTable &VST) {
 549   for (ValueSymbolTable::const_iterator VI = VST.begin(), VE = VST.end();
 550        VI != VE; ++VI)
 551     EnumerateValue(VI->getValue());
 552 }
 553
 554 /// Insert all of the values referenced by named metadata in the specified
 555 /// module.
 556 void ValueEnumerator::EnumerateNamedMetadata(const Module &M) {
 557   for (const auto &I : M.named_metadata())
 558     EnumerateNamedMDNode(&I);
 559 }
 560
 561 void ValueEnumerator::EnumerateNamedMDNode(const NamedMDNode *MD) {
 562   for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i)
 563     EnumerateMetadata(nullptr, MD->getOperand(i));
 564 }
 565
 566 unsigned ValueEnumerator::getMetadataFunctionID(const Function *F) const {
 567   return F ? getValueID(F) + 1 : 0;
 568 }
 569
 570 void ValueEnumerator::EnumerateMetadata(const Function *F, const Metadata *MD) {
 571   EnumerateMetadata(getMetadataFunctionID(F), MD);
 572 }
 573
 574 void ValueEnumerator::EnumerateFunctionLocalMetadata(
 575     const Function &F, const LocalAsMetadata *Local) {
 576   EnumerateFunctionLocalMetadata(getMetadataFunctionID(&F), Local);
 577 }
 578
 579 void ValueEnumerator::dropFunctionFromMetadata(
 580     MetadataMapType::value_type &FirstMD) {
 581   SmallVector<const MDNode *, 64> Worklist;
 582   auto push = [&Worklist](MetadataMapType::value_type &MD) {
 583     auto &Entry = MD.second;
 584
 585     // Nothing to do if this metadata isn't tagged.
 586     if (!Entry.F)
 587       return;
 588
 589     // Drop the function tag.
 590     Entry.F = 0;
 591
 592     // If this is has an ID and is an MDNode, then its operands have entries as
 593     // well.  We need to drop the function from them too.
 594     if (Entry.ID)
 595       if (auto *N = dyn_cast<MDNode>(MD.first))
 596         Worklist.push_back(N);
 597   };
 598   push(FirstMD);
 599   while (!Worklist.empty())
 600     for (const Metadata *Op : Worklist.pop_back_val()->operands()) {
 601       if (!Op)
 602         continue;
 603       auto MD = MetadataMap.find(Op);
 604       if (MD != MetadataMap.end())
 605         push(*MD);
 606     }
 607 }
 608
 609 void ValueEnumerator::EnumerateMetadata(unsigned F, const Metadata *MD) {
 610   // It's vital for reader efficiency that uniqued subgraphs are done in
 611   // post-order; it's expensive when their operands have forward references.
 612   // If a distinct node is referenced from a uniqued node, it'll be delayed
 613   // until the uniqued subgraph has been completely traversed.
 614   SmallVector<const MDNode *, 32> DelayedDistinctNodes;
 615
 616   // Start by enumerating MD, and then work through its transitive operands in
 617   // post-order.  This requires a depth-first search.
 618   SmallVector<std::pair<const MDNode *, MDNode::op_iterator>, 32> Worklist;
 619   if (const MDNode *N = enumerateMetadataImpl(F, MD))
 620     Worklist.push_back(std::make_pair(N, N->op_begin()));
 621
 622   while (!Worklist.empty()) {
 623     const MDNode *N = Worklist.back().first;
 624
 625     // Enumerate operands until we hit a new node.  We need to traverse these
 626     // nodes' operands before visiting the rest of N's operands.
 627     MDNode::op_iterator I = std::find_if(
 628         Worklist.back().second, N->op_end(),
 629         [&](const Metadata *MD) { return enumerateMetadataImpl(F, MD); });
 630     if (I != N->op_end()) {
 631       auto *Op = cast<MDNode>(*I);
 632       Worklist.back().second = ++I;
 633
 634       // Delay traversing Op if it's a distinct node and N is uniqued.
 635       if (Op->isDistinct() && !N->isDistinct())
 636         DelayedDistinctNodes.push_back(Op);
 637       else
 638         Worklist.push_back(std::make_pair(Op, Op->op_begin()));
 639       continue;
 640     }
 641
 642     // All the operands have been visited.  Now assign an ID.
 643     Worklist.pop_back();
 644     MDs.push_back(N);
 645     MetadataMap[N].ID = MDs.size();
 646
 647     // Flush out any delayed distinct nodes; these are all the distinct nodes
 648     // that are leaves in last uniqued subgraph.
 649     if (Worklist.empty() || Worklist.back().first->isDistinct()) {
 650       for (const MDNode *N : DelayedDistinctNodes)
 651         Worklist.push_back(std::make_pair(N, N->op_begin()));
 652       DelayedDistinctNodes.clear();
 653     }
 654   }
 655 }
 656
 657 const MDNode *ValueEnumerator::enumerateMetadataImpl(unsigned F, const Metadata *MD) {
 658   if (!MD)
 659     return nullptr;
 660
 661   assert(
 662       (isa<MDNode>(MD) || isa<MDString>(MD) || isa<ConstantAsMetadata>(MD)) &&
 663       "Invalid metadata kind");
 664
 665   auto Insertion = MetadataMap.insert(std::make_pair(MD, MDIndex(F)));
 666   MDIndex &Entry = Insertion.first->second;
 667   if (!Insertion.second) {
 668     // Already mapped.  If F doesn't match the function tag, drop it.
 669     if (Entry.hasDifferentFunction(F))
 670       dropFunctionFromMetadata(*Insertion.first);
 671     return nullptr;
 672   }
 673
 674   // Don't assign IDs to metadata nodes.
 675   if (auto *N = dyn_cast<MDNode>(MD))
 676     return N;
 677
 678   // Save the metadata.
 679   MDs.push_back(MD);
 680   Entry.ID = MDs.size();
 681
 682   // Enumerate the constant, if any.
 683   if (auto *C = dyn_cast<ConstantAsMetadata>(MD))
 684     EnumerateValue(C->getValue());
 685
 686   return nullptr;
 687 }
 688
 689 /// EnumerateFunctionLocalMetadataa - Incorporate function-local metadata
 690 /// information reachable from the metadata.
 691 void ValueEnumerator::EnumerateFunctionLocalMetadata(
 692     unsigned F, const LocalAsMetadata *Local) {
 693   assert(F && "Expected a function");
 694
 695   // Check to see if it's already in!
 696   MDIndex &Index = MetadataMap[Local];
 697   if (Index.ID) {
 698     assert(Index.F == F && "Expected the same function");
 699     return;
 700   }
 701
 702   MDs.push_back(Local);
 703   Index.F = F;
 704   Index.ID = MDs.size();
 705
 706   EnumerateValue(Local->getValue());
 707 }
 708
 709 static unsigned getMetadataTypeOrder(const Metadata *MD) {
 710   // Strings are emitted in bulk and must come first.
 711   if (isa<MDString>(MD))
 712     return 0;
 713
 714   // ConstantAsMetadata doesn't reference anything.  We may as well shuffle it
 715   // to the front since we can detect it.
 716   auto *N = dyn_cast<MDNode>(MD);
 717   if (!N)
 718     return 1;
 719
 720   // The reader is fast forward references for distinct node operands, but slow
 721   // when uniqued operands are unresolved.
 722   return N->isDistinct() ? 2 : 3;
 723 }
 724
 725 void ValueEnumerator::organizeMetadata() {
 726   assert(MetadataMap.size() == MDs.size() &&
 727          "Metadata map and vector out of sync");
 728
 729   if (MDs.empty())
 730     return;
 731
 732   // Copy out the index information from MetadataMap in order to choose a new
 733   // order.
 734   SmallVector<MDIndex, 64> Order;
 735   Order.reserve(MetadataMap.size());
 736   for (const Metadata *MD : MDs)
 737     Order.push_back(MetadataMap.lookup(MD));
 738
 739   // Partition:
 740   //   - by function, then
 741   //   - by isa<MDString>
 742   // and then sort by the original/current ID.  Since the IDs are guaranteed to
 743   // be unique, the result of std::sort will be deterministic.  There's no need
 744   // for std::stable_sort.
 745   llvm::sort(Order, [this](MDIndex LHS, MDIndex RHS) {
 746     return std::make_tuple(LHS.F, getMetadataTypeOrder(LHS.get(MDs)), LHS.ID) <
 747            std::make_tuple(RHS.F, getMetadataTypeOrder(RHS.get(MDs)), RHS.ID);
 748   });
 749
 750   // Rebuild MDs, index the metadata ranges for each function in FunctionMDs,
 751   // and fix up MetadataMap.
 752   std::vector<const Metadata *> OldMDs;
 753   MDs.swap(OldMDs);
 754   MDs.reserve(OldMDs.size());
 755   for (unsigned I = 0, E = Order.size(); I != E && !Order[I].F; ++I) {
 756     auto *MD = Order[I].get(OldMDs);
 757     MDs.push_back(MD);
 758     MetadataMap[MD].ID = I + 1;
 759     if (isa<MDString>(MD))
 760       ++NumMDStrings;
 761   }
 762
 763   // Return early if there's nothing for the functions.
 764   if (MDs.size() == Order.size())
 765     return;
 766
 767   // Build the function metadata ranges.
 768   MDRange R;
 769   FunctionMDs.reserve(OldMDs.size());
 770   unsigned PrevF = 0;
 771   for (unsigned I = MDs.size(), E = Order.size(), ID = MDs.size(); I != E;
 772        ++I) {
 773     unsigned F = Order[I].F;
 774     if (!PrevF) {
 775       PrevF = F;
 776     } else if (PrevF != F) {
 777       R.Last = FunctionMDs.size();
 778       std::swap(R, FunctionMDInfo[PrevF]);
 779       R.First = FunctionMDs.size();
 780
 781       ID = MDs.size();
 782       PrevF = F;
 783     }
 784
 785     auto *MD = Order[I].get(OldMDs);
 786     FunctionMDs.push_back(MD);
 787     MetadataMap[MD].ID = ++ID;
 788     if (isa<MDString>(MD))
 789       ++R.NumStrings;
 790   }
 791   R.Last = FunctionMDs.size();
 792   FunctionMDInfo[PrevF] = R;
 793 }
 794
 795 void ValueEnumerator::incorporateFunctionMetadata(const Function &F) {
 796   NumModuleMDs = MDs.size();
 797
 798   auto R = FunctionMDInfo.lookup(getValueID(&F) + 1);
 799   NumMDStrings = R.NumStrings;
 800   MDs.insert(MDs.end(), FunctionMDs.begin() + R.First,
 801              FunctionMDs.begin() + R.Last);
 802 }
 803
 804 void ValueEnumerator::EnumerateValue(const Value *V) {
 805   assert(!V->getType()->isVoidTy() && "Can't insert void values!");
 806   assert(!isa<MetadataAsValue>(V) && "EnumerateValue doesn't handle Metadata!");
 807
 808   // Check to see if it's already in!
 809   unsigned &ValueID = ValueMap[V];
 810   if (ValueID) {
 811     // Increment use count.
 812     Values[ValueID-1].second++;
 813     return;
 814   }
 815
 816   if (auto *GO = dyn_cast<GlobalObject>(V))
 817     if (const Comdat *C = GO->getComdat())
 818       Comdats.insert(C);
 819
 820   // Enumerate the type of this value.
 821   EnumerateType(V->getType());
 822
 823   if (const Constant *C = dyn_cast<Constant>(V)) {
 824     if (isa<GlobalValue>(C)) {
 825       // Initializers for globals are handled explicitly elsewhere.
 826     } else if (C->getNumOperands()) {
 827       // If a constant has operands, enumerate them.  This makes sure that if a
 828       // constant has uses (for example an array of const ints), that they are
 829       // inserted also.
 830
 831       // We prefer to enumerate them with values before we enumerate the user
 832       // itself.  This makes it more likely that we can avoid forward references
 833       // in the reader.  We know that there can be no cycles in the constants
 834       // graph that don't go through a global variable.
 835       for (User::const_op_iterator I = C->op_begin(), E = C->op_end();
 836            I != E; ++I)
 837         if (!isa<BasicBlock>(*I)) // Don't enumerate BB operand to BlockAddress.
 838           EnumerateValue(*I);
 839
 840       // Finally, add the value.  Doing this could make the ValueID reference be
 841       // dangling, don't reuse it.
 842       Values.push_back(std::make_pair(V, 1U));
 843       ValueMap[V] = Values.size();
 844       return;
 845     }
 846   }
 847
 848   // Add the value.
 849   Values.push_back(std::make_pair(V, 1U));
 850   ValueID = Values.size();
 851 }
 852
 853
 854 void ValueEnumerator::EnumerateType(Type *Ty) {
 855   unsigned *TypeID = &TypeMap[Ty];
 856
 857   // We've already seen this type.
 858   if (*TypeID)
 859     return;
 860
 861   // If it is a non-anonymous struct, mark the type as being visited so that we
 862   // don't recursively visit it.  This is safe because we allow forward
 863   // references of these in the bitcode reader.
 864   if (StructType *STy = dyn_cast<StructType>(Ty))
 865     if (!STy->isLiteral())
 866       *TypeID = ~0U;
 867
 868   // Enumerate all of the subtypes before we enumerate this type.  This ensures
 869   // that the type will be enumerated in an order that can be directly built.
 870   for (Type *SubTy : Ty->subtypes())
 871     EnumerateType(SubTy);
 872
 873   // Refresh the TypeID pointer in case the table rehashed.
 874   TypeID = &TypeMap[Ty];
 875
 876   // Check to see if we got the pointer another way.  This can happen when
 877   // enumerating recursive types that hit the base case deeper than they start.
 878   //
 879   // If this is actually a struct that we are treating as forward ref'able,
 880   // then emit the definition now that all of its contents are available.
 881   if (*TypeID && *TypeID != ~0U)
 882     return;
 883
 884   // Add this type now that its contents are all happily enumerated.
 885   Types.push_back(Ty);
 886
 887   *TypeID = Types.size();
 888 }
 889
 890 // Enumerate the types for the specified value.  If the value is a constant,
 891 // walk through it, enumerating the types of the constant.
 892 void ValueEnumerator::EnumerateOperandType(const Value *V) {
 893   EnumerateType(V->getType());
 894
 895   assert(!isa<MetadataAsValue>(V) && "Unexpected metadata operand");
 896
 897   const Constant *C = dyn_cast<Constant>(V);
 898   if (!C)
 899     return;
 900
 901   // If this constant is already enumerated, ignore it, we know its type must
 902   // be enumerated.
 903   if (ValueMap.count(C))
 904     return;
 905
 906   // This constant may have operands, make sure to enumerate the types in
 907   // them.
 908   for (const Value *Op : C->operands()) {
 909     // Don't enumerate basic blocks here, this happens as operands to
 910     // blockaddress.
 911     if (isa<BasicBlock>(Op))
 912       continue;
 913
 914     EnumerateOperandType(Op);
 915   }
 916 }
 917
 918 void ValueEnumerator::EnumerateAttributes(AttributeList PAL) {
 919   if (PAL.isEmpty()) return;  // null is always 0.
 920
 921   // Do a lookup.
 922   unsigned &Entry = AttributeListMap[PAL];
 923   if (Entry == 0) {
 924     // Never saw this before, add it.
 925     AttributeLists.push_back(PAL);
 926     Entry = AttributeLists.size();
 927   }
 928
 929   // Do lookups for all attribute groups.
 930   for (unsigned i = PAL.index_begin(), e = PAL.index_end(); i != e; ++i) {
 931     AttributeSet AS = PAL.getAttributes(i);
 932     if (!AS.hasAttributes())
 933       continue;
 934     IndexAndAttrSet Pair = {i, AS};
 935     unsigned &Entry = AttributeGroupMap[Pair];
 936     if (Entry == 0) {
 937       AttributeGroups.push_back(Pair);
 938       Entry = AttributeGroups.size();
 939     }
 940   }
 941 }
 942
 943 void ValueEnumerator::incorporateFunction(const Function &F) {
 944   InstructionCount = 0;
 945   NumModuleValues = Values.size();
 946
 947   // Add global metadata to the function block.  This doesn't include
 948   // LocalAsMetadata.
 949   incorporateFunctionMetadata(F);
 950
 951   // Adding function arguments to the value table.
 952   for (const auto &I : F.args()) {
 953     EnumerateValue(&I);
 954     if (I.hasAttribute(Attribute::ByVal))
 955       EnumerateType(I.getParamByValType());
 956   }
 957   FirstFuncConstantID = Values.size();
 958
 959   // Add all function-level constants to the value table.
 960   for (const BasicBlock &BB : F) {
 961     for (const Instruction &I : BB)
 962       for (const Use &OI : I.operands()) {
 963         if ((isa<Constant>(OI) && !isa<GlobalValue>(OI)) || isa<InlineAsm>(OI))
 964           EnumerateValue(OI);
 965       }
 966     BasicBlocks.push_back(&BB);
 967     ValueMap[&BB] = BasicBlocks.size();
 968   }
 969
 970   // Optimize the constant layout.
 971   OptimizeConstants(FirstFuncConstantID, Values.size());
 972
 973   // Add the function's parameter attributes so they are available for use in
 974   // the function's instruction.
 975   EnumerateAttributes(F.getAttributes());
 976
 977   FirstInstID = Values.size();
 978
 979   SmallVector<LocalAsMetadata *, 8> FnLocalMDVector;
 980   // Add all of the instructions.
 981   for (const BasicBlock &BB : F) {
 982     for (const Instruction &I : BB) {
 983       for (const Use &OI : I.operands()) {
 984         if (auto *MD = dyn_cast<MetadataAsValue>(&OI))
 985           if (auto *Local = dyn_cast<LocalAsMetadata>(MD->getMetadata()))
 986             // Enumerate metadata after the instructions they might refer to.
 987             FnLocalMDVector.push_back(Local);
 988       }
 989
 990       if (!I.getType()->isVoidTy())
 991         EnumerateValue(&I);
 992     }
 993   }
 994
 995   // Add all of the function-local metadata.
 996   for (unsigned i = 0, e = FnLocalMDVector.size(); i != e; ++i) {
 997     // At this point, every local values have been incorporated, we shouldn't
 998     // have a metadata operand that references a value that hasn't been seen.
 999     assert(ValueMap.count(FnLocalMDVector[i]->getValue()) &&
1000            "Missing value for metadata operand");
1001     EnumerateFunctionLocalMetadata(F, FnLocalMDVector[i]);
1002   }
1003 }
1004
1005 void ValueEnumerator::purgeFunction() {
1006   /// Remove purged values from the ValueMap.
1007   for (unsigned i = NumModuleValues, e = Values.size(); i != e; ++i)
1008     ValueMap.erase(Values[i].first);
1009   for (unsigned i = NumModuleMDs, e = MDs.size(); i != e; ++i)
1010     MetadataMap.erase(MDs[i]);
1011   for (unsigned i = 0, e = BasicBlocks.size(); i != e; ++i)
1012     ValueMap.erase(BasicBlocks[i]);
1013
1014   Values.resize(NumModuleValues);
1015   MDs.resize(NumModuleMDs);
1016   BasicBlocks.clear();
1017   NumMDStrings = 0;
1018 }
1019
1020 static void IncorporateFunctionInfoGlobalBBIDs(const Function *F,
1021                                  DenseMap<const BasicBlock*, unsigned> &IDMap) {
1022   unsigned Counter = 0;
1023   for (const BasicBlock &BB : *F)
1024     IDMap[&BB] = ++Counter;
1025 }
1026
1027 /// getGlobalBasicBlockID - This returns the function-specific ID for the
1028 /// specified basic block.  This is relatively expensive information, so it
1029 /// should only be used by rare constructs such as address-of-label.
1030 unsigned ValueEnumerator::getGlobalBasicBlockID(const BasicBlock *BB) const {
1031   unsigned &Idx = GlobalBasicBlockIDs[BB];
1032   if (Idx != 0)
1033     return Idx-1;
1034
1035   IncorporateFunctionInfoGlobalBBIDs(BB->getParent(), GlobalBasicBlockIDs);
1036   return getGlobalBasicBlockID(BB);
1037 }
1038
1039 uint64_t ValueEnumerator::computeBitsRequiredForTypeIndicies() const {
1040   return Log2_32_Ceil(getTypes().size() + 1);
1041 }