xref: /freebsd/contrib/llvm-project/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp (revision f976241773df2260e6170317080761d1c5814fe5)
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 }
1042