src/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

   1 //===-- ValueEnumerator.cpp - Number values and types for bitcode writer --===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the ValueEnumerator class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ValueEnumerator.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/SmallPtrSet.h"
  17 #include "llvm/IR/Constants.h"
  18 #include "llvm/IR/DerivedTypes.h"
  19 #include "llvm/IR/Instructions.h"
  20 #include "llvm/IR/Module.h"
  21 #include "llvm/IR/UseListOrder.h"
  22 #include "llvm/IR/ValueSymbolTable.h"
  23 #include "llvm/Support/Debug.h"
  24 #include "llvm/Support/raw_ostream.h"
  25 #include <algorithm>
  26 using namespace llvm;
  27
  28 namespace {
  29 struct OrderMap {
  30   DenseMap<const Value *, std::pair<unsigned, bool>> IDs;
  31   unsigned LastGlobalConstantID;
  32   unsigned LastGlobalValueID;
  33
  34   OrderMap() : LastGlobalConstantID(0), LastGlobalValueID(0) {}
  35
  36   bool isGlobalConstant(unsigned ID) const {
  37     return ID <= LastGlobalConstantID;
  38   }
  39   bool isGlobalValue(unsigned ID) const {
  40     return ID <= LastGlobalValueID && !isGlobalConstant(ID);
  41   }
  42
  43   unsigned size() const { return IDs.size(); }
  44   std::pair<unsigned, bool> &operator[](const Value *V) { return IDs[V]; }
  45   std::pair<unsigned, bool> lookup(const Value *V) const {
  46     return IDs.lookup(V);
  47   }
  48   void index(const Value *V) {
  49     // Explicitly sequence get-size and insert-value operations to avoid UB.
  50     unsigned ID = IDs.size() + 1;
  51     IDs[V].first = ID;
  52   }
  53 };
  54 }
  55
  56 static void orderValue(const Value *V, OrderMap &OM) {
  57   if (OM.lookup(V).first)
  58     return;
  59
  60   if (const Constant *C = dyn_cast<Constant>(V))
  61     if (C->getNumOperands() && !isa<GlobalValue>(C))
  62       for (const Value *Op : C->operands())
  63         if (!isa<BasicBlock>(Op) && !isa<GlobalValue>(Op))
  64           orderValue(Op, OM);
  65
  66   // Note: we cannot cache this lookup above, since inserting into the map
  67   // changes the map's size, and thus affects the other IDs.
  68   OM.index(V);
  69 }
  70
  71 static OrderMap orderModule(const Module &M) {
  72   // This needs to match the order used by ValueEnumerator::ValueEnumerator()
  73   // and ValueEnumerator::incorporateFunction().
  74   OrderMap OM;
  75
  76   // In the reader, initializers of GlobalValues are set *after* all the
  77   // globals have been read.  Rather than awkwardly modeling this behaviour
  78   // directly in predictValueUseListOrderImpl(), just assign IDs to
  79   // initializers of GlobalValues before GlobalValues themselves to model this
  80   // implicitly.
  81   for (const GlobalVariable &G : M.globals())
  82     if (G.hasInitializer())
  83       if (!isa<GlobalValue>(G.getInitializer()))
  84         orderValue(G.getInitializer(), OM);
  85   for (const GlobalAlias &A : M.aliases())
  86     if (!isa<GlobalValue>(A.getAliasee()))
  87       orderValue(A.getAliasee(), OM);
  88   for (const Function &F : M) {
  89     if (F.hasPrefixData())
  90       if (!isa<GlobalValue>(F.getPrefixData()))
  91         orderValue(F.getPrefixData(), OM);
  92     if (F.hasPrologueData())
  93       if (!isa<GlobalValue>(F.getPrologueData()))
  94         orderValue(F.getPrologueData(), OM);
  95   }
  96   OM.LastGlobalConstantID = OM.size();
  97
  98   // Initializers of GlobalValues are processed in
  99   // BitcodeReader::ResolveGlobalAndAliasInits().  Match the order there rather
 100   // than ValueEnumerator, and match the code in predictValueUseListOrderImpl()
 101   // by giving IDs in reverse order.
 102   //
 103   // Since GlobalValues never reference each other directly (just through
 104   // initializers), their relative IDs only matter for determining order of
 105   // uses in their initializers.
 106   for (const Function &F : M)
 107     orderValue(&F, OM);
 108   for (const GlobalAlias &A : M.aliases())
 109     orderValue(&A, OM);
 110   for (const GlobalVariable &G : M.globals())
 111     orderValue(&G, OM);
 112   OM.LastGlobalValueID = OM.size();
 113
 114   for (const Function &F : M) {
 115     if (F.isDeclaration())
 116       continue;
 117     // Here we need to match the union of ValueEnumerator::incorporateFunction()
 118     // and WriteFunction().  Basic blocks are implicitly declared before
 119     // anything else (by declaring their size).
 120     for (const BasicBlock &BB : F)
 121       orderValue(&BB, OM);
 122     for (const Argument &A : F.args())
 123       orderValue(&A, OM);
 124     for (const BasicBlock &BB : F)
 125       for (const Instruction &I : BB)
 126         for (const Value *Op : I.operands())
 127           if ((isa<Constant>(*Op) && !isa<GlobalValue>(*Op)) ||
 128               isa<InlineAsm>(*Op))
 129             orderValue(Op, OM);
 130     for (const BasicBlock &BB : F)
 131       for (const Instruction &I : BB)
 132         orderValue(&I, OM);
 133   }
 134   return OM;
 135 }
 136
 137 static void predictValueUseListOrderImpl(const Value *V, const Function *F,
 138                                          unsigned ID, const OrderMap &OM,
 139                                          UseListOrderStack &Stack) {
 140   // Predict use-list order for this one.
 141   typedef std::pair<const Use *, unsigned> Entry;
 142   SmallVector<Entry, 64> List;
 143   for (const Use &U : V->uses())
 144     // Check if this user will be serialized.
 145     if (OM.lookup(U.getUser()).first)
 146       List.push_back(std::make_pair(&U, List.size()));
 147
 148   if (List.size() < 2)
 149     // We may have lost some users.
 150     return;
 151
 152   bool IsGlobalValue = OM.isGlobalValue(ID);
 153   std::sort(List.begin(), List.end(), [&](const Entry &L, const Entry &R) {
 154     const Use *LU = L.first;
 155     const Use *RU = R.first;
 156     if (LU == RU)
 157       return false;
 158
 159     auto LID = OM.lookup(LU->getUser()).first;
 160     auto RID = OM.lookup(RU->getUser()).first;
 161
 162     // Global values are processed in reverse order.
 163     //
 164     // Moreover, initializers of GlobalValues are set *after* all the globals
 165     // have been read (despite having earlier IDs).  Rather than awkwardly
 166     // modeling this behaviour here, orderModule() has assigned IDs to
 167     // initializers of GlobalValues before GlobalValues themselves.
 168     if (OM.isGlobalValue(LID) && OM.isGlobalValue(RID))
 169       return LID < RID;
 170
 171     // If ID is 4, then expect: 7 6 5 1 2 3.
 172     if (LID < RID) {
 173       if (RID <= ID)
 174         if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 175           return true;
 176       return false;
 177     }
 178     if (RID < LID) {
 179       if (LID <= ID)
 180         if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 181           return false;
 182       return true;
 183     }
 184
 185     // LID and RID are equal, so we have different operands of the same user.
 186     // Assume operands are added in order for all instructions.
 187     if (LID <= ID)
 188       if (!IsGlobalValue) // GlobalValue uses don't get reversed.
 189         return LU->getOperandNo() < RU->getOperandNo();
 190     return LU->getOperandNo() > RU->getOperandNo();
 191   });
 192
 193   if (std::is_sorted(
 194           List.begin(), List.end(),
 195           [](const Entry &L, const Entry &R) { return L.second < R.second; }))
 196     // Order is already correct.
 197     return;
 198
 199   // Store the shuffle.
 200   Stack.emplace_back(V, F, List.size());
 201   assert(List.size() == Stack.back().Shuffle.size() && "Wrong size");
 202   for (size_t I = 0, E = List.size(); I != E; ++I)
 203     Stack.back().Shuffle[I] = List[I].second;
 204 }
 205
 206 static void predictValueUseListOrder(const Value *V, const Function *F,
 207                                      OrderMap &OM, UseListOrderStack &Stack) {
 208   auto &IDPair = OM[V];
 209   assert(IDPair.first && "Unmapped value");
 210   if (IDPair.second)
 211     // Already predicted.
 212     return;
 213
 214   // Do the actual prediction.
 215   IDPair.second = true;
 216   if (!V->use_empty() && std::next(V->use_begin()) != V->use_end())
 217     predictValueUseListOrderImpl(V, F, IDPair.first, OM, Stack);
 218
 219   // Recursive descent into constants.
 220   if (const Constant *C = dyn_cast<Constant>(V))
 221     if (C->getNumOperands()) // Visit GlobalValues.
 222       for (const Value *Op : C->operands())
 223         if (isa<Constant>(Op)) // Visit GlobalValues.
 224           predictValueUseListOrder(Op, F, OM, Stack);
 225 }
 226
 227 static UseListOrderStack predictUseListOrder(const Module &M) {
 228   OrderMap OM = orderModule(M);
 229
 230   // Use-list orders need to be serialized after all the users have been added
 231   // to a value, or else the shuffles will be incomplete.  Store them per
 232   // function in a stack.
 233   //
 234   // Aside from function order, the order of values doesn't matter much here.
 235   UseListOrderStack Stack;
 236
 237   // We want to visit the functions backward now so we can list function-local
 238   // constants in the last Function they're used in.  Module-level constants
 239   // have already been visited above.
 240   for (auto I = M.rbegin(), E = M.rend(); I != E; ++I) {
 241     const Function &F = *I;
 242     if (F.isDeclaration())
 243       continue;
 244     for (const BasicBlock &BB : F)
 245       predictValueUseListOrder(&BB, &F, OM, Stack);
 246     for (const Argument &A : F.args())
 247       predictValueUseListOrder(&A, &F, OM, Stack);
 248     for (const BasicBlock &BB : F)
 249       for (const Instruction &I : BB)
 250         for (const Value *Op : I.operands())
 251           if (isa<Constant>(*Op) || isa<InlineAsm>(*Op)) // Visit GlobalValues.
 252             predictValueUseListOrder(Op, &F, OM, Stack);
 253     for (const BasicBlock &BB : F)
 254       for (const Instruction &I : BB)
 255         predictValueUseListOrder(&I, &F, OM, Stack);
 256   }
 257
 258   // Visit globals last, since the module-level use-list block will be seen
 259   // before the function bodies are processed.
 260   for (const GlobalVariable &G : M.globals())
 261     predictValueUseListOrder(&G, nullptr, OM, Stack);
 262   for (const Function &F : M)
 263     predictValueUseListOrder(&F, nullptr, OM, Stack);
 264   for (const GlobalAlias &A : M.aliases())
 265     predictValueUseListOrder(&A, nullptr, OM, Stack);
 266   for (const GlobalVariable &G : M.globals())
 267     if (G.hasInitializer())
 268       predictValueUseListOrder(G.getInitializer(), nullptr, OM, Stack);
 269   for (const GlobalAlias &A : M.aliases())
 270     predictValueUseListOrder(A.getAliasee(), nullptr, OM, Stack);
 271   for (const Function &F : M) {
 272     if (F.hasPrefixData())
 273       predictValueUseListOrder(F.getPrefixData(), nullptr, OM, Stack);
 274     if (F.hasPrologueData())
 275       predictValueUseListOrder(F.getPrologueData(), nullptr, OM, Stack);
 276   }
 277
 278   return Stack;
 279 }
 280
 281 static bool isIntOrIntVectorValue(const std::pair<const Value*, unsigned> &V) {
 282   return V.first->getType()->isIntOrIntVectorTy();
 283 }
 284
 285 ValueEnumerator::ValueEnumerator(const Module &M)
 286     : HasMDString(false), HasMDLocation(false) {
 287   if (shouldPreserveBitcodeUseListOrder())
 288     UseListOrders = predictUseListOrder(M);
 289
 290   // Enumerate the global variables.
 291   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
 292        I != E; ++I)
 293     EnumerateValue(I);
 294
 295   // Enumerate the functions.
 296   for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
 297     EnumerateValue(I);
 298     EnumerateAttributes(cast<Function>(I)->getAttributes());
 299   }
 300
 301   // Enumerate the aliases.
 302   for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
 303        I != E; ++I)
 304     EnumerateValue(I);
 305
 306   // Remember what is the cutoff between globalvalue's and other constants.
 307   unsigned FirstConstant = Values.size();
 308
 309   // Enumerate the global variable initializers.
 310   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
 311        I != E; ++I)
 312     if (I->hasInitializer())
 313       EnumerateValue(I->getInitializer());
 314
 315   // Enumerate the aliasees.
 316   for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
 317        I != E; ++I)
 318     EnumerateValue(I->getAliasee());
 319
 320   // Enumerate the prefix data constants.
 321   for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I)
 322     if (I->hasPrefixData())
 323       EnumerateValue(I->getPrefixData());
 324
 325   // Enumerate the prologue data constants.
 326   for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I)
 327     if (I->hasPrologueData())
 328       EnumerateValue(I->getPrologueData());
 329
 330   // Enumerate the metadata type.
 331   //
 332   // TODO: Move this to ValueEnumerator::EnumerateOperandType() once bitcode
 333   // only encodes the metadata type when it's used as a value.
 334   EnumerateType(Type::getMetadataTy(M.getContext()));
 335
 336   // Insert constants and metadata that are named at module level into the slot
 337   // pool so that the module symbol table can refer to them...
 338   EnumerateValueSymbolTable(M.getValueSymbolTable());
 339   EnumerateNamedMetadata(M);
 340
 341   SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
 342
 343   // Enumerate types used by function bodies and argument lists.
 344   for (const Function &F : M) {
 345     for (const Argument &A : F.args())
 346       EnumerateType(A.getType());
 347
 348     for (const BasicBlock &BB : F)
 349       for (const Instruction &I : BB) {
 350         for (const Use &Op : I.operands()) {
 351           auto *MD = dyn_cast<MetadataAsValue>(&Op);
 352           if (!MD) {
 353             EnumerateOperandType(Op);
 354             continue;
 355           }
 356
 357           // Local metadata is enumerated during function-incorporation.
 358           if (isa<LocalAsMetadata>(MD->getMetadata()))
 359             continue;
 360
 361           EnumerateMetadata(MD->getMetadata());
 362         }
 363         EnumerateType(I.getType());
 364         if (const CallInst *CI = dyn_cast<CallInst>(&I))
 365           EnumerateAttributes(CI->getAttributes());
 366         else if (const InvokeInst *II = dyn_cast<InvokeInst>(&I))
 367           EnumerateAttributes(II->getAttributes());
 368
 369         // Enumerate metadata attached with this instruction.
 370         MDs.clear();
 371         I.getAllMetadataOtherThanDebugLoc(MDs);
 372         for (unsigned i = 0, e = MDs.size(); i != e; ++i)
 373           EnumerateMetadata(MDs[i].second);
 374
 375         if (!I.getDebugLoc().isUnknown()) {
 376           MDNode *Scope, *IA;
 377           I.getDebugLoc().getScopeAndInlinedAt(Scope, IA, I.getContext());
 378           if (Scope) EnumerateMetadata(Scope);
 379           if (IA) EnumerateMetadata(IA);
 380         }
 381       }
 382   }
 383
 384   // Optimize constant ordering.
 385   OptimizeConstants(FirstConstant, Values.size());
 386 }
 387
 388 unsigned ValueEnumerator::getInstructionID(const Instruction *Inst) const {
 389   InstructionMapType::const_iterator I = InstructionMap.find(Inst);
 390   assert(I != InstructionMap.end() && "Instruction is not mapped!");
 391   return I->second;
 392 }
 393
 394 unsigned ValueEnumerator::getComdatID(const Comdat *C) const {
 395   unsigned ComdatID = Comdats.idFor(C);
 396   assert(ComdatID && "Comdat not found!");
 397   return ComdatID;
 398 }
 399
 400 void ValueEnumerator::setInstructionID(const Instruction *I) {
 401   InstructionMap[I] = InstructionCount++;
 402 }
 403
 404 unsigned ValueEnumerator::getValueID(const Value *V) const {
 405   if (auto *MD = dyn_cast<MetadataAsValue>(V))
 406     return getMetadataID(MD->getMetadata());
 407
 408   ValueMapType::const_iterator I = ValueMap.find(V);
 409   assert(I != ValueMap.end() && "Value not in slotcalculator!");
 410   return I->second-1;
 411 }
 412
 413 unsigned ValueEnumerator::getMetadataID(const Metadata *MD) const {
 414   auto I = MDValueMap.find(MD);
 415   assert(I != MDValueMap.end() && "Metadata not in slotcalculator!");
 416   return I->second - 1;
 417 }
 418
 419 void ValueEnumerator::dump() const {
 420   print(dbgs(), ValueMap, "Default");
 421   dbgs() << '\n';
 422   print(dbgs(), MDValueMap, "MetaData");
 423   dbgs() << '\n';
 424 }
 425
 426 void ValueEnumerator::print(raw_ostream &OS, const ValueMapType &Map,
 427                             const char *Name) const {
 428
 429   OS << "Map Name: " << Name << "\n";
 430   OS << "Size: " << Map.size() << "\n";
 431   for (ValueMapType::const_iterator I = Map.begin(),
 432          E = Map.end(); I != E; ++I) {
 433
 434     const Value *V = I->first;
 435     if (V->hasName())
 436       OS << "Value: " << V->getName();
 437     else
 438       OS << "Value: [null]\n";
 439     V->dump();
 440
 441     OS << " Uses(" << std::distance(V->use_begin(),V->use_end()) << "):";
 442     for (const Use &U : V->uses()) {
 443       if (&U != &*V->use_begin())
 444         OS << ",";
 445       if(U->hasName())
 446         OS << " " << U->getName();
 447       else
 448         OS << " [null]";
 449
 450     }
 451     OS <<  "\n\n";
 452   }
 453 }
 454
 455 void ValueEnumerator::print(raw_ostream &OS, const MetadataMapType &Map,
 456                             const char *Name) const {
 457
 458   OS << "Map Name: " << Name << "\n";
 459   OS << "Size: " << Map.size() << "\n";
 460   for (auto I = Map.begin(), E = Map.end(); I != E; ++I) {
 461     const Metadata *MD = I->first;
 462     OS << "Metadata: slot = " << I->second << "\n";
 463     MD->print(OS);
 464   }
 465 }
 466
 467 /// OptimizeConstants - Reorder constant pool for denser encoding.
 468 void ValueEnumerator::OptimizeConstants(unsigned CstStart, unsigned CstEnd) {
 469   if (CstStart == CstEnd || CstStart+1 == CstEnd) return;
 470
 471   if (shouldPreserveBitcodeUseListOrder())
 472     // Optimizing constants makes the use-list order difficult to predict.
 473     // Disable it for now when trying to preserve the order.
 474     return;
 475
 476   std::stable_sort(Values.begin() + CstStart, Values.begin() + CstEnd,
 477                    [this](const std::pair<const Value *, unsigned> &LHS,
 478                           const std::pair<const Value *, unsigned> &RHS) {
 479     // Sort by plane.
 480     if (LHS.first->getType() != RHS.first->getType())
 481       return getTypeID(LHS.first->getType()) < getTypeID(RHS.first->getType());
 482     // Then by frequency.
 483     return LHS.second > RHS.second;
 484   });
 485
 486   // Ensure that integer and vector of integer constants are at the start of the
 487   // constant pool.  This is important so that GEP structure indices come before
 488   // gep constant exprs.
 489   std::partition(Values.begin()+CstStart, Values.begin()+CstEnd,
 490                  isIntOrIntVectorValue);
 491
 492   // Rebuild the modified portion of ValueMap.
 493   for (; CstStart != CstEnd; ++CstStart)
 494     ValueMap[Values[CstStart].first] = CstStart+1;
 495 }
 496
 497
 498 /// EnumerateValueSymbolTable - Insert all of the values in the specified symbol
 499 /// table into the values table.
 500 void ValueEnumerator::EnumerateValueSymbolTable(const ValueSymbolTable &VST) {
 501   for (ValueSymbolTable::const_iterator VI = VST.begin(), VE = VST.end();
 502        VI != VE; ++VI)
 503     EnumerateValue(VI->getValue());
 504 }
 505
 506 /// Insert all of the values referenced by named metadata in the specified
 507 /// module.
 508 void ValueEnumerator::EnumerateNamedMetadata(const Module &M) {
 509   for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
 510                                              E = M.named_metadata_end();
 511        I != E; ++I)
 512     EnumerateNamedMDNode(I);
 513 }
 514
 515 void ValueEnumerator::EnumerateNamedMDNode(const NamedMDNode *MD) {
 516   for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i)
 517     EnumerateMetadata(MD->getOperand(i));
 518 }
 519
 520 /// EnumerateMDNodeOperands - Enumerate all non-function-local values
 521 /// and types referenced by the given MDNode.
 522 void ValueEnumerator::EnumerateMDNodeOperands(const MDNode *N) {
 523   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
 524     Metadata *MD = N->getOperand(i);
 525     if (!MD)
 526       continue;
 527     assert(!isa<LocalAsMetadata>(MD) && "MDNodes cannot be function-local");
 528     EnumerateMetadata(MD);
 529   }
 530 }
 531
 532 void ValueEnumerator::EnumerateMetadata(const Metadata *MD) {
 533   assert(
 534       (isa<MDNode>(MD) || isa<MDString>(MD) || isa<ConstantAsMetadata>(MD)) &&
 535       "Invalid metadata kind");
 536
 537   // Insert a dummy ID to block the co-recursive call to
 538   // EnumerateMDNodeOperands() from re-visiting MD in a cyclic graph.
 539   //
 540   // Return early if there's already an ID.
 541   if (!MDValueMap.insert(std::make_pair(MD, 0)).second)
 542     return;
 543
 544   // Visit operands first to minimize RAUW.
 545   if (auto *N = dyn_cast<MDNode>(MD))
 546     EnumerateMDNodeOperands(N);
 547   else if (auto *C = dyn_cast<ConstantAsMetadata>(MD))
 548     EnumerateValue(C->getValue());
 549
 550   HasMDString |= isa<MDString>(MD);
 551   HasMDLocation |= isa<MDLocation>(MD);
 552
 553   // Replace the dummy ID inserted above with the correct one.  MDValueMap may
 554   // have changed by inserting operands, so we need a fresh lookup here.
 555   MDs.push_back(MD);
 556   MDValueMap[MD] = MDs.size();
 557 }
 558
 559 /// EnumerateFunctionLocalMetadataa - Incorporate function-local metadata
 560 /// information reachable from the metadata.
 561 void ValueEnumerator::EnumerateFunctionLocalMetadata(
 562     const LocalAsMetadata *Local) {
 563   // Check to see if it's already in!
 564   unsigned &MDValueID = MDValueMap[Local];
 565   if (MDValueID)
 566     return;
 567
 568   MDs.push_back(Local);
 569   MDValueID = MDs.size();
 570
 571   EnumerateValue(Local->getValue());
 572
 573   // Also, collect all function-local metadata for easy access.
 574   FunctionLocalMDs.push_back(Local);
 575 }
 576
 577 void ValueEnumerator::EnumerateValue(const Value *V) {
 578   assert(!V->getType()->isVoidTy() && "Can't insert void values!");
 579   assert(!isa<MetadataAsValue>(V) && "EnumerateValue doesn't handle Metadata!");
 580
 581   // Check to see if it's already in!
 582   unsigned &ValueID = ValueMap[V];
 583   if (ValueID) {
 584     // Increment use count.
 585     Values[ValueID-1].second++;
 586     return;
 587   }
 588
 589   if (auto *GO = dyn_cast<GlobalObject>(V))
 590     if (const Comdat *C = GO->getComdat())
 591       Comdats.insert(C);
 592
 593   // Enumerate the type of this value.
 594   EnumerateType(V->getType());
 595
 596   if (const Constant *C = dyn_cast<Constant>(V)) {
 597     if (isa<GlobalValue>(C)) {
 598       // Initializers for globals are handled explicitly elsewhere.
 599     } else if (C->getNumOperands()) {
 600       // If a constant has operands, enumerate them.  This makes sure that if a
 601       // constant has uses (for example an array of const ints), that they are
 602       // inserted also.
 603
 604       // We prefer to enumerate them with values before we enumerate the user
 605       // itself.  This makes it more likely that we can avoid forward references
 606       // in the reader.  We know that there can be no cycles in the constants
 607       // graph that don't go through a global variable.
 608       for (User::const_op_iterator I = C->op_begin(), E = C->op_end();
 609            I != E; ++I)
 610         if (!isa<BasicBlock>(*I)) // Don't enumerate BB operand to BlockAddress.
 611           EnumerateValue(*I);
 612
 613       // Finally, add the value.  Doing this could make the ValueID reference be
 614       // dangling, don't reuse it.
 615       Values.push_back(std::make_pair(V, 1U));
 616       ValueMap[V] = Values.size();
 617       return;
 618     }
 619   }
 620
 621   // Add the value.
 622   Values.push_back(std::make_pair(V, 1U));
 623   ValueID = Values.size();
 624 }
 625
 626
 627 void ValueEnumerator::EnumerateType(Type *Ty) {
 628   unsigned *TypeID = &TypeMap[Ty];
 629
 630   // We've already seen this type.
 631   if (*TypeID)
 632     return;
 633
 634   // If it is a non-anonymous struct, mark the type as being visited so that we
 635   // don't recursively visit it.  This is safe because we allow forward
 636   // references of these in the bitcode reader.
 637   if (StructType *STy = dyn_cast<StructType>(Ty))
 638     if (!STy->isLiteral())
 639       *TypeID = ~0U;
 640
 641   // Enumerate all of the subtypes before we enumerate this type.  This ensures
 642   // that the type will be enumerated in an order that can be directly built.
 643   for (Type *SubTy : Ty->subtypes())
 644     EnumerateType(SubTy);
 645
 646   // Refresh the TypeID pointer in case the table rehashed.
 647   TypeID = &TypeMap[Ty];
 648
 649   // Check to see if we got the pointer another way.  This can happen when
 650   // enumerating recursive types that hit the base case deeper than they start.
 651   //
 652   // If this is actually a struct that we are treating as forward ref'able,
 653   // then emit the definition now that all of its contents are available.
 654   if (*TypeID && *TypeID != ~0U)
 655     return;
 656
 657   // Add this type now that its contents are all happily enumerated.
 658   Types.push_back(Ty);
 659
 660   *TypeID = Types.size();
 661 }
 662
 663 // Enumerate the types for the specified value.  If the value is a constant,
 664 // walk through it, enumerating the types of the constant.
 665 void ValueEnumerator::EnumerateOperandType(const Value *V) {
 666   EnumerateType(V->getType());
 667
 668   if (auto *MD = dyn_cast<MetadataAsValue>(V)) {
 669     assert(!isa<LocalAsMetadata>(MD->getMetadata()) &&
 670            "Function-local metadata should be left for later");
 671
 672     EnumerateMetadata(MD->getMetadata());
 673     return;
 674   }
 675
 676   const Constant *C = dyn_cast<Constant>(V);
 677   if (!C)
 678     return;
 679
 680   // If this constant is already enumerated, ignore it, we know its type must
 681   // be enumerated.
 682   if (ValueMap.count(C))
 683     return;
 684
 685   // This constant may have operands, make sure to enumerate the types in
 686   // them.
 687   for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
 688     const Value *Op = C->getOperand(i);
 689
 690     // Don't enumerate basic blocks here, this happens as operands to
 691     // blockaddress.
 692     if (isa<BasicBlock>(Op))
 693       continue;
 694
 695     EnumerateOperandType(Op);
 696   }
 697 }
 698
 699 void ValueEnumerator::EnumerateAttributes(AttributeSet PAL) {
 700   if (PAL.isEmpty()) return;  // null is always 0.
 701
 702   // Do a lookup.
 703   unsigned &Entry = AttributeMap[PAL];
 704   if (Entry == 0) {
 705     // Never saw this before, add it.
 706     Attribute.push_back(PAL);
 707     Entry = Attribute.size();
 708   }
 709
 710   // Do lookups for all attribute groups.
 711   for (unsigned i = 0, e = PAL.getNumSlots(); i != e; ++i) {
 712     AttributeSet AS = PAL.getSlotAttributes(i);
 713     unsigned &Entry = AttributeGroupMap[AS];
 714     if (Entry == 0) {
 715       AttributeGroups.push_back(AS);
 716       Entry = AttributeGroups.size();
 717     }
 718   }
 719 }
 720
 721 void ValueEnumerator::incorporateFunction(const Function &F) {
 722   InstructionCount = 0;
 723   NumModuleValues = Values.size();
 724   NumModuleMDs = MDs.size();
 725
 726   // Adding function arguments to the value table.
 727   for (Function::const_arg_iterator I = F.arg_begin(), E = F.arg_end();
 728        I != E; ++I)
 729     EnumerateValue(I);
 730
 731   FirstFuncConstantID = Values.size();
 732
 733   // Add all function-level constants to the value table.
 734   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
 735     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I!=E; ++I)
 736       for (User::const_op_iterator OI = I->op_begin(), E = I->op_end();
 737            OI != E; ++OI) {
 738         if ((isa<Constant>(*OI) && !isa<GlobalValue>(*OI)) ||
 739             isa<InlineAsm>(*OI))
 740           EnumerateValue(*OI);
 741       }
 742     BasicBlocks.push_back(BB);
 743     ValueMap[BB] = BasicBlocks.size();
 744   }
 745
 746   // Optimize the constant layout.
 747   OptimizeConstants(FirstFuncConstantID, Values.size());
 748
 749   // Add the function's parameter attributes so they are available for use in
 750   // the function's instruction.
 751   EnumerateAttributes(F.getAttributes());
 752
 753   FirstInstID = Values.size();
 754
 755   SmallVector<LocalAsMetadata *, 8> FnLocalMDVector;
 756   // Add all of the instructions.
 757   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
 758     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I!=E; ++I) {
 759       for (User::const_op_iterator OI = I->op_begin(), E = I->op_end();
 760            OI != E; ++OI) {
 761         if (auto *MD = dyn_cast<MetadataAsValue>(&*OI))
 762           if (auto *Local = dyn_cast<LocalAsMetadata>(MD->getMetadata()))
 763             // Enumerate metadata after the instructions they might refer to.
 764             FnLocalMDVector.push_back(Local);
 765       }
 766
 767       if (!I->getType()->isVoidTy())
 768         EnumerateValue(I);
 769     }
 770   }
 771
 772   // Add all of the function-local metadata.
 773   for (unsigned i = 0, e = FnLocalMDVector.size(); i != e; ++i)
 774     EnumerateFunctionLocalMetadata(FnLocalMDVector[i]);
 775 }
 776
 777 void ValueEnumerator::purgeFunction() {
 778   /// Remove purged values from the ValueMap.
 779   for (unsigned i = NumModuleValues, e = Values.size(); i != e; ++i)
 780     ValueMap.erase(Values[i].first);
 781   for (unsigned i = NumModuleMDs, e = MDs.size(); i != e; ++i)
 782     MDValueMap.erase(MDs[i]);
 783   for (unsigned i = 0, e = BasicBlocks.size(); i != e; ++i)
 784     ValueMap.erase(BasicBlocks[i]);
 785
 786   Values.resize(NumModuleValues);
 787   MDs.resize(NumModuleMDs);
 788   BasicBlocks.clear();
 789   FunctionLocalMDs.clear();
 790 }
 791
 792 static void IncorporateFunctionInfoGlobalBBIDs(const Function *F,
 793                                  DenseMap<const BasicBlock*, unsigned> &IDMap) {
 794   unsigned Counter = 0;
 795   for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
 796     IDMap[BB] = ++Counter;
 797 }
 798
 799 /// getGlobalBasicBlockID - This returns the function-specific ID for the
 800 /// specified basic block.  This is relatively expensive information, so it
 801 /// should only be used by rare constructs such as address-of-label.
 802 unsigned ValueEnumerator::getGlobalBasicBlockID(const BasicBlock *BB) const {
 803   unsigned &Idx = GlobalBasicBlockIDs[BB];
 804   if (Idx != 0)
 805     return Idx-1;
 806
 807   IncorporateFunctionInfoGlobalBBIDs(BB->getParent(), GlobalBasicBlockIDs);
 808   return getGlobalBasicBlockID(BB);
 809 }