ValueMapper.cpp revision 360784 
1//===- ValueMapper.cpp - Interface shared by lib/Transforms/Utils ---------===//
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 defines the MapValue function, which is shared by various parts of
10// the lib/Transforms/Utils library.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Transforms/Utils/ValueMapper.h"
15#include "llvm/ADT/ArrayRef.h"
16#include "llvm/ADT/DenseMap.h"
17#include "llvm/ADT/DenseSet.h"
18#include "llvm/ADT/None.h"
19#include "llvm/ADT/Optional.h"
20#include "llvm/ADT/STLExtras.h"
21#include "llvm/ADT/SmallVector.h"
22#include "llvm/IR/Argument.h"
23#include "llvm/IR/BasicBlock.h"
24#include "llvm/IR/CallSite.h"
25#include "llvm/IR/Constant.h"
26#include "llvm/IR/Constants.h"
27#include "llvm/IR/DebugInfoMetadata.h"
28#include "llvm/IR/DerivedTypes.h"
29#include "llvm/IR/Function.h"
30#include "llvm/IR/GlobalObject.h"
31#include "llvm/IR/GlobalIndirectSymbol.h"
32#include "llvm/IR/GlobalVariable.h"
33#include "llvm/IR/InlineAsm.h"
34#include "llvm/IR/Instruction.h"
35#include "llvm/IR/Instructions.h"
36#include "llvm/IR/Metadata.h"
37#include "llvm/IR/Operator.h"
38#include "llvm/IR/Type.h"
39#include "llvm/IR/Value.h"
40#include "llvm/Support/Casting.h"
41#include <cassert>
42#include <limits>
43#include <memory>
44#include <utility>
45
46using namespace llvm;
47
48// Out of line method to get vtable etc for class.
49void ValueMapTypeRemapper::anchor() {}
50void ValueMaterializer::anchor() {}
51
52namespace {
53
54/// A basic block used in a BlockAddress whose function body is not yet
55/// materialized.
56struct DelayedBasicBlock {
57  BasicBlock *OldBB;
58  std::unique_ptr<BasicBlock> TempBB;
59
60  DelayedBasicBlock(const BlockAddress &Old)
61      : OldBB(Old.getBasicBlock()),
62        TempBB(BasicBlock::Create(Old.getContext())) {}
63};
64
65struct WorklistEntry {
66  enum EntryKind {
67    MapGlobalInit,
68    MapAppendingVar,
69    MapGlobalIndirectSymbol,
70    RemapFunction
71  };
72  struct GVInitTy {
73    GlobalVariable *GV;
74    Constant *Init;
75  };
76  struct AppendingGVTy {
77    GlobalVariable *GV;
78    Constant *InitPrefix;
79  };
80  struct GlobalIndirectSymbolTy {
81    GlobalIndirectSymbol *GIS;
82    Constant *Target;
83  };
84
85  unsigned Kind : 2;
86  unsigned MCID : 29;
87  unsigned AppendingGVIsOldCtorDtor : 1;
88  unsigned AppendingGVNumNewMembers;
89  union {
90    GVInitTy GVInit;
91    AppendingGVTy AppendingGV;
92    GlobalIndirectSymbolTy GlobalIndirectSymbol;
93    Function *RemapF;
94  } Data;
95};
96
97struct MappingContext {
98  ValueToValueMapTy *VM;
99  ValueMaterializer *Materializer = nullptr;
100
101  /// Construct a MappingContext with a value map and materializer.
102  explicit MappingContext(ValueToValueMapTy &VM,
103                          ValueMaterializer *Materializer = nullptr)
104      : VM(&VM), Materializer(Materializer) {}
105};
106
107class Mapper {
108  friend class MDNodeMapper;
109
110#ifndef NDEBUG
111  DenseSet<GlobalValue *> AlreadyScheduled;
112#endif
113
114  RemapFlags Flags;
115  ValueMapTypeRemapper *TypeMapper;
116  unsigned CurrentMCID = 0;
117  SmallVector<MappingContext, 2> MCs;
118  SmallVector<WorklistEntry, 4> Worklist;
119  SmallVector<DelayedBasicBlock, 1> DelayedBBs;
120  SmallVector<Constant *, 16> AppendingInits;
121
122public:
123  Mapper(ValueToValueMapTy &VM, RemapFlags Flags,
124         ValueMapTypeRemapper *TypeMapper, ValueMaterializer *Materializer)
125      : Flags(Flags), TypeMapper(TypeMapper),
126        MCs(1, MappingContext(VM, Materializer)) {}
127
128  /// ValueMapper should explicitly call \a flush() before destruction.
129  ~Mapper() { assert(!hasWorkToDo() && "Expected to be flushed"); }
130
131  bool hasWorkToDo() const { return !Worklist.empty(); }
132
133  unsigned
134  registerAlternateMappingContext(ValueToValueMapTy &VM,
135                                  ValueMaterializer *Materializer = nullptr) {
136    MCs.push_back(MappingContext(VM, Materializer));
137    return MCs.size() - 1;
138  }
139
140  void addFlags(RemapFlags Flags);
141
142  void remapGlobalObjectMetadata(GlobalObject &GO);
143
144  Value *mapValue(const Value *V);
145  void remapInstruction(Instruction *I);
146  void remapFunction(Function &F);
147
148  Constant *mapConstant(const Constant *C) {
149    return cast_or_null<Constant>(mapValue(C));
150  }
151
152  /// Map metadata.
153  ///
154  /// Find the mapping for MD.  Guarantees that the return will be resolved
155  /// (not an MDNode, or MDNode::isResolved() returns true).
156  Metadata *mapMetadata(const Metadata *MD);
157
158  void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
159                                    unsigned MCID);
160  void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
161                                    bool IsOldCtorDtor,
162                                    ArrayRef<Constant *> NewMembers,
163                                    unsigned MCID);
164  void scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS, Constant &Target,
165                                       unsigned MCID);
166  void scheduleRemapFunction(Function &F, unsigned MCID);
167
168  void flush();
169
170private:
171  void mapGlobalInitializer(GlobalVariable &GV, Constant &Init);
172  void mapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
173                            bool IsOldCtorDtor,
174                            ArrayRef<Constant *> NewMembers);
175  void mapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS, Constant &Target);
176  void remapFunction(Function &F, ValueToValueMapTy &VM);
177
178  ValueToValueMapTy &getVM() { return *MCs[CurrentMCID].VM; }
179  ValueMaterializer *getMaterializer() { return MCs[CurrentMCID].Materializer; }
180
181  Value *mapBlockAddress(const BlockAddress &BA);
182
183  /// Map metadata that doesn't require visiting operands.
184  Optional<Metadata *> mapSimpleMetadata(const Metadata *MD);
185
186  Metadata *mapToMetadata(const Metadata *Key, Metadata *Val);
187  Metadata *mapToSelf(const Metadata *MD);
188};
189
190class MDNodeMapper {
191  Mapper &M;
192
193  /// Data about a node in \a UniquedGraph.
194  struct Data {
195    bool HasChanged = false;
196    unsigned ID = std::numeric_limits<unsigned>::max();
197    TempMDNode Placeholder;
198  };
199
200  /// A graph of uniqued nodes.
201  struct UniquedGraph {
202    SmallDenseMap<const Metadata *, Data, 32> Info; // Node properties.
203    SmallVector<MDNode *, 16> POT;                  // Post-order traversal.
204
205    /// Propagate changed operands through the post-order traversal.
206    ///
207    /// Iteratively update \a Data::HasChanged for each node based on \a
208    /// Data::HasChanged of its operands, until fixed point.
209    void propagateChanges();
210
211    /// Get a forward reference to a node to use as an operand.
212    Metadata &getFwdReference(MDNode &Op);
213  };
214
215  /// Worklist of distinct nodes whose operands need to be remapped.
216  SmallVector<MDNode *, 16> DistinctWorklist;
217
218  // Storage for a UniquedGraph.
219  SmallDenseMap<const Metadata *, Data, 32> InfoStorage;
220  SmallVector<MDNode *, 16> POTStorage;
221
222public:
223  MDNodeMapper(Mapper &M) : M(M) {}
224
225  /// Map a metadata node (and its transitive operands).
226  ///
227  /// Map all the (unmapped) nodes in the subgraph under \c N.  The iterative
228  /// algorithm handles distinct nodes and uniqued node subgraphs using
229  /// different strategies.
230  ///
231  /// Distinct nodes are immediately mapped and added to \a DistinctWorklist
232  /// using \a mapDistinctNode().  Their mapping can always be computed
233  /// immediately without visiting operands, even if their operands change.
234  ///
235  /// The mapping for uniqued nodes depends on whether their operands change.
236  /// \a mapTopLevelUniquedNode() traverses the transitive uniqued subgraph of
237  /// a node to calculate uniqued node mappings in bulk.  Distinct leafs are
238  /// added to \a DistinctWorklist with \a mapDistinctNode().
239  ///
240  /// After mapping \c N itself, this function remaps the operands of the
241  /// distinct nodes in \a DistinctWorklist until the entire subgraph under \c
242  /// N has been mapped.
243  Metadata *map(const MDNode &N);
244
245private:
246  /// Map a top-level uniqued node and the uniqued subgraph underneath it.
247  ///
248  /// This builds up a post-order traversal of the (unmapped) uniqued subgraph
249  /// underneath \c FirstN and calculates the nodes' mapping.  Each node uses
250  /// the identity mapping (\a Mapper::mapToSelf()) as long as all of its
251  /// operands uses the identity mapping.
252  ///
253  /// The algorithm works as follows:
254  ///
255  ///  1. \a createPOT(): traverse the uniqued subgraph under \c FirstN and
256  ///     save the post-order traversal in the given \a UniquedGraph, tracking
257  ///     nodes' operands change.
258  ///
259  ///  2. \a UniquedGraph::propagateChanges(): propagate changed operands
260  ///     through the \a UniquedGraph until fixed point, following the rule
261  ///     that if a node changes, any node that references must also change.
262  ///
263  ///  3. \a mapNodesInPOT(): map the uniqued nodes, creating new uniqued nodes
264  ///     (referencing new operands) where necessary.
265  Metadata *mapTopLevelUniquedNode(const MDNode &FirstN);
266
267  /// Try to map the operand of an \a MDNode.
268  ///
269  /// If \c Op is already mapped, return the mapping.  If it's not an \a
270  /// MDNode, compute and return the mapping.  If it's a distinct \a MDNode,
271  /// return the result of \a mapDistinctNode().
272  ///
273  /// \return None if \c Op is an unmapped uniqued \a MDNode.
274  /// \post getMappedOp(Op) only returns None if this returns None.
275  Optional<Metadata *> tryToMapOperand(const Metadata *Op);
276
277  /// Map a distinct node.
278  ///
279  /// Return the mapping for the distinct node \c N, saving the result in \a
280  /// DistinctWorklist for later remapping.
281  ///
282  /// \pre \c N is not yet mapped.
283  /// \pre \c N.isDistinct().
284  MDNode *mapDistinctNode(const MDNode &N);
285
286  /// Get a previously mapped node.
287  Optional<Metadata *> getMappedOp(const Metadata *Op) const;
288
289  /// Create a post-order traversal of an unmapped uniqued node subgraph.
290  ///
291  /// This traverses the metadata graph deeply enough to map \c FirstN.  It
292  /// uses \a tryToMapOperand() (via \a Mapper::mapSimplifiedNode()), so any
293  /// metadata that has already been mapped will not be part of the POT.
294  ///
295  /// Each node that has a changed operand from outside the graph (e.g., a
296  /// distinct node, an already-mapped uniqued node, or \a ConstantAsMetadata)
297  /// is marked with \a Data::HasChanged.
298  ///
299  /// \return \c true if any nodes in \c G have \a Data::HasChanged.
300  /// \post \c G.POT is a post-order traversal ending with \c FirstN.
301  /// \post \a Data::hasChanged in \c G.Info indicates whether any node needs
302  /// to change because of operands outside the graph.
303  bool createPOT(UniquedGraph &G, const MDNode &FirstN);
304
305  /// Visit the operands of a uniqued node in the POT.
306  ///
307  /// Visit the operands in the range from \c I to \c E, returning the first
308  /// uniqued node we find that isn't yet in \c G.  \c I is always advanced to
309  /// where to continue the loop through the operands.
310  ///
311  /// This sets \c HasChanged if any of the visited operands change.
312  MDNode *visitOperands(UniquedGraph &G, MDNode::op_iterator &I,
313                        MDNode::op_iterator E, bool &HasChanged);
314
315  /// Map all the nodes in the given uniqued graph.
316  ///
317  /// This visits all the nodes in \c G in post-order, using the identity
318  /// mapping or creating a new node depending on \a Data::HasChanged.
319  ///
320  /// \pre \a getMappedOp() returns None for nodes in \c G, but not for any of
321  /// their operands outside of \c G.
322  /// \pre \a Data::HasChanged is true for a node in \c G iff any of its
323  /// operands have changed.
324  /// \post \a getMappedOp() returns the mapped node for every node in \c G.
325  void mapNodesInPOT(UniquedGraph &G);
326
327  /// Remap a node's operands using the given functor.
328  ///
329  /// Iterate through the operands of \c N and update them in place using \c
330  /// mapOperand.
331  ///
332  /// \pre N.isDistinct() or N.isTemporary().
333  template <class OperandMapper>
334  void remapOperands(MDNode &N, OperandMapper mapOperand);
335};
336
337} // end anonymous namespace
338
339Value *Mapper::mapValue(const Value *V) {
340  ValueToValueMapTy::iterator I = getVM().find(V);
341
342  // If the value already exists in the map, use it.
343  if (I != getVM().end()) {
344    assert(I->second && "Unexpected null mapping");
345    return I->second;
346  }
347
348  // If we have a materializer and it can materialize a value, use that.
349  if (auto *Materializer = getMaterializer()) {
350    if (Value *NewV = Materializer->materialize(const_cast<Value *>(V))) {
351      getVM()[V] = NewV;
352      return NewV;
353    }
354  }
355
356  // Global values do not need to be seeded into the VM if they
357  // are using the identity mapping.
358  if (isa<GlobalValue>(V)) {
359    if (Flags & RF_NullMapMissingGlobalValues)
360      return nullptr;
361    return getVM()[V] = const_cast<Value *>(V);
362  }
363
364  if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
365    // Inline asm may need *type* remapping.
366    FunctionType *NewTy = IA->getFunctionType();
367    if (TypeMapper) {
368      NewTy = cast<FunctionType>(TypeMapper->remapType(NewTy));
369
370      if (NewTy != IA->getFunctionType())
371        V = InlineAsm::get(NewTy, IA->getAsmString(), IA->getConstraintString(),
372                           IA->hasSideEffects(), IA->isAlignStack());
373    }
374
375    return getVM()[V] = const_cast<Value *>(V);
376  }
377
378  if (const auto *MDV = dyn_cast<MetadataAsValue>(V)) {
379    const Metadata *MD = MDV->getMetadata();
380
381    if (auto *LAM = dyn_cast<LocalAsMetadata>(MD)) {
382      // Look through to grab the local value.
383      if (Value *LV = mapValue(LAM->getValue())) {
384        if (V == LAM->getValue())
385          return const_cast<Value *>(V);
386        return MetadataAsValue::get(V->getContext(), ValueAsMetadata::get(LV));
387      }
388
389      // FIXME: always return nullptr once Verifier::verifyDominatesUse()
390      // ensures metadata operands only reference defined SSA values.
391      return (Flags & RF_IgnoreMissingLocals)
392                 ? nullptr
393                 : MetadataAsValue::get(V->getContext(),
394                                        MDTuple::get(V->getContext(), None));
395    }
396
397    // If this is a module-level metadata and we know that nothing at the module
398    // level is changing, then use an identity mapping.
399    if (Flags & RF_NoModuleLevelChanges)
400      return getVM()[V] = const_cast<Value *>(V);
401
402    // Map the metadata and turn it into a value.
403    auto *MappedMD = mapMetadata(MD);
404    if (MD == MappedMD)
405      return getVM()[V] = const_cast<Value *>(V);
406    return getVM()[V] = MetadataAsValue::get(V->getContext(), MappedMD);
407  }
408
409  // Okay, this either must be a constant (which may or may not be mappable) or
410  // is something that is not in the mapping table.
411  Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
412  if (!C)
413    return nullptr;
414
415  if (BlockAddress *BA = dyn_cast<BlockAddress>(C))
416    return mapBlockAddress(*BA);
417
418  auto mapValueOrNull = [this](Value *V) {
419    auto Mapped = mapValue(V);
420    assert((Mapped || (Flags & RF_NullMapMissingGlobalValues)) &&
421           "Unexpected null mapping for constant operand without "
422           "NullMapMissingGlobalValues flag");
423    return Mapped;
424  };
425
426  // Otherwise, we have some other constant to remap.  Start by checking to see
427  // if all operands have an identity remapping.
428  unsigned OpNo = 0, NumOperands = C->getNumOperands();
429  Value *Mapped = nullptr;
430  for (; OpNo != NumOperands; ++OpNo) {
431    Value *Op = C->getOperand(OpNo);
432    Mapped = mapValueOrNull(Op);
433    if (!Mapped)
434      return nullptr;
435    if (Mapped != Op)
436      break;
437  }
438
439  // See if the type mapper wants to remap the type as well.
440  Type *NewTy = C->getType();
441  if (TypeMapper)
442    NewTy = TypeMapper->remapType(NewTy);
443
444  // If the result type and all operands match up, then just insert an identity
445  // mapping.
446  if (OpNo == NumOperands && NewTy == C->getType())
447    return getVM()[V] = C;
448
449  // Okay, we need to create a new constant.  We've already processed some or
450  // all of the operands, set them all up now.
451  SmallVector<Constant*, 8> Ops;
452  Ops.reserve(NumOperands);
453  for (unsigned j = 0; j != OpNo; ++j)
454    Ops.push_back(cast<Constant>(C->getOperand(j)));
455
456  // If one of the operands mismatch, push it and the other mapped operands.
457  if (OpNo != NumOperands) {
458    Ops.push_back(cast<Constant>(Mapped));
459
460    // Map the rest of the operands that aren't processed yet.
461    for (++OpNo; OpNo != NumOperands; ++OpNo) {
462      Mapped = mapValueOrNull(C->getOperand(OpNo));
463      if (!Mapped)
464        return nullptr;
465      Ops.push_back(cast<Constant>(Mapped));
466    }
467  }
468  Type *NewSrcTy = nullptr;
469  if (TypeMapper)
470    if (auto *GEPO = dyn_cast<GEPOperator>(C))
471      NewSrcTy = TypeMapper->remapType(GEPO->getSourceElementType());
472
473  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
474    return getVM()[V] = CE->getWithOperands(Ops, NewTy, false, NewSrcTy);
475  if (isa<ConstantArray>(C))
476    return getVM()[V] = ConstantArray::get(cast<ArrayType>(NewTy), Ops);
477  if (isa<ConstantStruct>(C))
478    return getVM()[V] = ConstantStruct::get(cast<StructType>(NewTy), Ops);
479  if (isa<ConstantVector>(C))
480    return getVM()[V] = ConstantVector::get(Ops);
481  // If this is a no-operand constant, it must be because the type was remapped.
482  if (isa<UndefValue>(C))
483    return getVM()[V] = UndefValue::get(NewTy);
484  if (isa<ConstantAggregateZero>(C))
485    return getVM()[V] = ConstantAggregateZero::get(NewTy);
486  assert(isa<ConstantPointerNull>(C));
487  return getVM()[V] = ConstantPointerNull::get(cast<PointerType>(NewTy));
488}
489
490Value *Mapper::mapBlockAddress(const BlockAddress &BA) {
491  Function *F = cast<Function>(mapValue(BA.getFunction()));
492
493  // F may not have materialized its initializer.  In that case, create a
494  // dummy basic block for now, and replace it once we've materialized all
495  // the initializers.
496  BasicBlock *BB;
497  if (F->empty()) {
498    DelayedBBs.push_back(DelayedBasicBlock(BA));
499    BB = DelayedBBs.back().TempBB.get();
500  } else {
501    BB = cast_or_null<BasicBlock>(mapValue(BA.getBasicBlock()));
502  }
503
504  return getVM()[&BA] = BlockAddress::get(F, BB ? BB : BA.getBasicBlock());
505}
506
507Metadata *Mapper::mapToMetadata(const Metadata *Key, Metadata *Val) {
508  getVM().MD()[Key].reset(Val);
509  return Val;
510}
511
512Metadata *Mapper::mapToSelf(const Metadata *MD) {
513  return mapToMetadata(MD, const_cast<Metadata *>(MD));
514}
515
516Optional<Metadata *> MDNodeMapper::tryToMapOperand(const Metadata *Op) {
517  if (!Op)
518    return nullptr;
519
520  if (Optional<Metadata *> MappedOp = M.mapSimpleMetadata(Op)) {
521#ifndef NDEBUG
522    if (auto *CMD = dyn_cast<ConstantAsMetadata>(Op))
523      assert((!*MappedOp || M.getVM().count(CMD->getValue()) ||
524              M.getVM().getMappedMD(Op)) &&
525             "Expected Value to be memoized");
526    else
527      assert((isa<MDString>(Op) || M.getVM().getMappedMD(Op)) &&
528             "Expected result to be memoized");
529#endif
530    return *MappedOp;
531  }
532
533  const MDNode &N = *cast<MDNode>(Op);
534  if (N.isDistinct())
535    return mapDistinctNode(N);
536  return None;
537}
538
539static Metadata *cloneOrBuildODR(const MDNode &N) {
540  auto *CT = dyn_cast<DICompositeType>(&N);
541  // If ODR type uniquing is enabled, we would have uniqued composite types
542  // with identifiers during bitcode reading, so we can just use CT.
543  if (CT && CT->getContext().isODRUniquingDebugTypes() &&
544      CT->getIdentifier() != "")
545    return const_cast<DICompositeType *>(CT);
546  return MDNode::replaceWithDistinct(N.clone());
547}
548
549MDNode *MDNodeMapper::mapDistinctNode(const MDNode &N) {
550  assert(N.isDistinct() && "Expected a distinct node");
551  assert(!M.getVM().getMappedMD(&N) && "Expected an unmapped node");
552  DistinctWorklist.push_back(
553      cast<MDNode>((M.Flags & RF_MoveDistinctMDs)
554                       ? M.mapToSelf(&N)
555                       : M.mapToMetadata(&N, cloneOrBuildODR(N))));
556  return DistinctWorklist.back();
557}
558
559static ConstantAsMetadata *wrapConstantAsMetadata(const ConstantAsMetadata &CMD,
560                                                  Value *MappedV) {
561  if (CMD.getValue() == MappedV)
562    return const_cast<ConstantAsMetadata *>(&CMD);
563  return MappedV ? ConstantAsMetadata::getConstant(MappedV) : nullptr;
564}
565
566Optional<Metadata *> MDNodeMapper::getMappedOp(const Metadata *Op) const {
567  if (!Op)
568    return nullptr;
569
570  if (Optional<Metadata *> MappedOp = M.getVM().getMappedMD(Op))
571    return *MappedOp;
572
573  if (isa<MDString>(Op))
574    return const_cast<Metadata *>(Op);
575
576  if (auto *CMD = dyn_cast<ConstantAsMetadata>(Op))
577    return wrapConstantAsMetadata(*CMD, M.getVM().lookup(CMD->getValue()));
578
579  return None;
580}
581
582Metadata &MDNodeMapper::UniquedGraph::getFwdReference(MDNode &Op) {
583  auto Where = Info.find(&Op);
584  assert(Where != Info.end() && "Expected a valid reference");
585
586  auto &OpD = Where->second;
587  if (!OpD.HasChanged)
588    return Op;
589
590  // Lazily construct a temporary node.
591  if (!OpD.Placeholder)
592    OpD.Placeholder = Op.clone();
593
594  return *OpD.Placeholder;
595}
596
597template <class OperandMapper>
598void MDNodeMapper::remapOperands(MDNode &N, OperandMapper mapOperand) {
599  assert(!N.isUniqued() && "Expected distinct or temporary nodes");
600  for (unsigned I = 0, E = N.getNumOperands(); I != E; ++I) {
601    Metadata *Old = N.getOperand(I);
602    Metadata *New = mapOperand(Old);
603
604    if (Old != New)
605      N.replaceOperandWith(I, New);
606  }
607}
608
609namespace {
610
611/// An entry in the worklist for the post-order traversal.
612struct POTWorklistEntry {
613  MDNode *N;              ///< Current node.
614  MDNode::op_iterator Op; ///< Current operand of \c N.
615
616  /// Keep a flag of whether operands have changed in the worklist to avoid
617  /// hitting the map in \a UniquedGraph.
618  bool HasChanged = false;
619
620  POTWorklistEntry(MDNode &N) : N(&N), Op(N.op_begin()) {}
621};
622
623} // end anonymous namespace
624
625bool MDNodeMapper::createPOT(UniquedGraph &G, const MDNode &FirstN) {
626  assert(G.Info.empty() && "Expected a fresh traversal");
627  assert(FirstN.isUniqued() && "Expected uniqued node in POT");
628
629  // Construct a post-order traversal of the uniqued subgraph under FirstN.
630  bool AnyChanges = false;
631  SmallVector<POTWorklistEntry, 16> Worklist;
632  Worklist.push_back(POTWorklistEntry(const_cast<MDNode &>(FirstN)));
633  (void)G.Info[&FirstN];
634  while (!Worklist.empty()) {
635    // Start or continue the traversal through the this node's operands.
636    auto &WE = Worklist.back();
637    if (MDNode *N = visitOperands(G, WE.Op, WE.N->op_end(), WE.HasChanged)) {
638      // Push a new node to traverse first.
639      Worklist.push_back(POTWorklistEntry(*N));
640      continue;
641    }
642
643    // Push the node onto the POT.
644    assert(WE.N->isUniqued() && "Expected only uniqued nodes");
645    assert(WE.Op == WE.N->op_end() && "Expected to visit all operands");
646    auto &D = G.Info[WE.N];
647    AnyChanges |= D.HasChanged = WE.HasChanged;
648    D.ID = G.POT.size();
649    G.POT.push_back(WE.N);
650
651    // Pop the node off the worklist.
652    Worklist.pop_back();
653  }
654  return AnyChanges;
655}
656
657MDNode *MDNodeMapper::visitOperands(UniquedGraph &G, MDNode::op_iterator &I,
658                                    MDNode::op_iterator E, bool &HasChanged) {
659  while (I != E) {
660    Metadata *Op = *I++; // Increment even on early return.
661    if (Optional<Metadata *> MappedOp = tryToMapOperand(Op)) {
662      // Check if the operand changes.
663      HasChanged |= Op != *MappedOp;
664      continue;
665    }
666
667    // A uniqued metadata node.
668    MDNode &OpN = *cast<MDNode>(Op);
669    assert(OpN.isUniqued() &&
670           "Only uniqued operands cannot be mapped immediately");
671    if (G.Info.insert(std::make_pair(&OpN, Data())).second)
672      return &OpN; // This is a new one.  Return it.
673  }
674  return nullptr;
675}
676
677void MDNodeMapper::UniquedGraph::propagateChanges() {
678  bool AnyChanges;
679  do {
680    AnyChanges = false;
681    for (MDNode *N : POT) {
682      auto &D = Info[N];
683      if (D.HasChanged)
684        continue;
685
686      if (llvm::none_of(N->operands(), [&](const Metadata *Op) {
687            auto Where = Info.find(Op);
688            return Where != Info.end() && Where->second.HasChanged;
689          }))
690        continue;
691
692      AnyChanges = D.HasChanged = true;
693    }
694  } while (AnyChanges);
695}
696
697void MDNodeMapper::mapNodesInPOT(UniquedGraph &G) {
698  // Construct uniqued nodes, building forward references as necessary.
699  SmallVector<MDNode *, 16> CyclicNodes;
700  for (auto *N : G.POT) {
701    auto &D = G.Info[N];
702    if (!D.HasChanged) {
703      // The node hasn't changed.
704      M.mapToSelf(N);
705      continue;
706    }
707
708    // Remember whether this node had a placeholder.
709    bool HadPlaceholder(D.Placeholder);
710
711    // Clone the uniqued node and remap the operands.
712    TempMDNode ClonedN = D.Placeholder ? std::move(D.Placeholder) : N->clone();
713    remapOperands(*ClonedN, [this, &D, &G](Metadata *Old) {
714      if (Optional<Metadata *> MappedOp = getMappedOp(Old))
715        return *MappedOp;
716      (void)D;
717      assert(G.Info[Old].ID > D.ID && "Expected a forward reference");
718      return &G.getFwdReference(*cast<MDNode>(Old));
719    });
720
721    auto *NewN = MDNode::replaceWithUniqued(std::move(ClonedN));
722    M.mapToMetadata(N, NewN);
723
724    // Nodes that were referenced out of order in the POT are involved in a
725    // uniquing cycle.
726    if (HadPlaceholder)
727      CyclicNodes.push_back(NewN);
728  }
729
730  // Resolve cycles.
731  for (auto *N : CyclicNodes)
732    if (!N->isResolved())
733      N->resolveCycles();
734}
735
736Metadata *MDNodeMapper::map(const MDNode &N) {
737  assert(DistinctWorklist.empty() && "MDNodeMapper::map is not recursive");
738  assert(!(M.Flags & RF_NoModuleLevelChanges) &&
739         "MDNodeMapper::map assumes module-level changes");
740
741  // Require resolved nodes whenever metadata might be remapped.
742  assert(N.isResolved() && "Unexpected unresolved node");
743
744  Metadata *MappedN =
745      N.isUniqued() ? mapTopLevelUniquedNode(N) : mapDistinctNode(N);
746  while (!DistinctWorklist.empty())
747    remapOperands(*DistinctWorklist.pop_back_val(), [this](Metadata *Old) {
748      if (Optional<Metadata *> MappedOp = tryToMapOperand(Old))
749        return *MappedOp;
750      return mapTopLevelUniquedNode(*cast<MDNode>(Old));
751    });
752  return MappedN;
753}
754
755Metadata *MDNodeMapper::mapTopLevelUniquedNode(const MDNode &FirstN) {
756  assert(FirstN.isUniqued() && "Expected uniqued node");
757
758  // Create a post-order traversal of uniqued nodes under FirstN.
759  UniquedGraph G;
760  if (!createPOT(G, FirstN)) {
761    // Return early if no nodes have changed.
762    for (const MDNode *N : G.POT)
763      M.mapToSelf(N);
764    return &const_cast<MDNode &>(FirstN);
765  }
766
767  // Update graph with all nodes that have changed.
768  G.propagateChanges();
769
770  // Map all the nodes in the graph.
771  mapNodesInPOT(G);
772
773  // Return the original node, remapped.
774  return *getMappedOp(&FirstN);
775}
776
777Optional<Metadata *> Mapper::mapSimpleMetadata(const Metadata *MD) {
778  // If the value already exists in the map, use it.
779  if (Optional<Metadata *> NewMD = getVM().getMappedMD(MD))
780    return *NewMD;
781
782  if (isa<MDString>(MD))
783    return const_cast<Metadata *>(MD);
784
785  // This is a module-level metadata.  If nothing at the module level is
786  // changing, use an identity mapping.
787  if ((Flags & RF_NoModuleLevelChanges))
788    return const_cast<Metadata *>(MD);
789
790  if (auto *CMD = dyn_cast<ConstantAsMetadata>(MD)) {
791    // Don't memoize ConstantAsMetadata.  Instead of lasting until the
792    // LLVMContext is destroyed, they can be deleted when the GlobalValue they
793    // reference is destructed.  These aren't super common, so the extra
794    // indirection isn't that expensive.
795    return wrapConstantAsMetadata(*CMD, mapValue(CMD->getValue()));
796  }
797
798  assert(isa<MDNode>(MD) && "Expected a metadata node");
799
800  return None;
801}
802
803Metadata *Mapper::mapMetadata(const Metadata *MD) {
804  assert(MD && "Expected valid metadata");
805  assert(!isa<LocalAsMetadata>(MD) && "Unexpected local metadata");
806
807  if (Optional<Metadata *> NewMD = mapSimpleMetadata(MD))
808    return *NewMD;
809
810  return MDNodeMapper(*this).map(*cast<MDNode>(MD));
811}
812
813void Mapper::flush() {
814  // Flush out the worklist of global values.
815  while (!Worklist.empty()) {
816    WorklistEntry E = Worklist.pop_back_val();
817    CurrentMCID = E.MCID;
818    switch (E.Kind) {
819    case WorklistEntry::MapGlobalInit:
820      E.Data.GVInit.GV->setInitializer(mapConstant(E.Data.GVInit.Init));
821      remapGlobalObjectMetadata(*E.Data.GVInit.GV);
822      break;
823    case WorklistEntry::MapAppendingVar: {
824      unsigned PrefixSize = AppendingInits.size() - E.AppendingGVNumNewMembers;
825      mapAppendingVariable(*E.Data.AppendingGV.GV,
826                           E.Data.AppendingGV.InitPrefix,
827                           E.AppendingGVIsOldCtorDtor,
828                           makeArrayRef(AppendingInits).slice(PrefixSize));
829      AppendingInits.resize(PrefixSize);
830      break;
831    }
832    case WorklistEntry::MapGlobalIndirectSymbol:
833      E.Data.GlobalIndirectSymbol.GIS->setIndirectSymbol(
834          mapConstant(E.Data.GlobalIndirectSymbol.Target));
835      break;
836    case WorklistEntry::RemapFunction:
837      remapFunction(*E.Data.RemapF);
838      break;
839    }
840  }
841  CurrentMCID = 0;
842
843  // Finish logic for block addresses now that all global values have been
844  // handled.
845  while (!DelayedBBs.empty()) {
846    DelayedBasicBlock DBB = DelayedBBs.pop_back_val();
847    BasicBlock *BB = cast_or_null<BasicBlock>(mapValue(DBB.OldBB));
848    DBB.TempBB->replaceAllUsesWith(BB ? BB : DBB.OldBB);
849  }
850}
851
852void Mapper::remapInstruction(Instruction *I) {
853  // Remap operands.
854  for (Use &Op : I->operands()) {
855    Value *V = mapValue(Op);
856    // If we aren't ignoring missing entries, assert that something happened.
857    if (V)
858      Op = V;
859    else
860      assert((Flags & RF_IgnoreMissingLocals) &&
861             "Referenced value not in value map!");
862  }
863
864  // Remap phi nodes' incoming blocks.
865  if (PHINode *PN = dyn_cast<PHINode>(I)) {
866    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
867      Value *V = mapValue(PN->getIncomingBlock(i));
868      // If we aren't ignoring missing entries, assert that something happened.
869      if (V)
870        PN->setIncomingBlock(i, cast<BasicBlock>(V));
871      else
872        assert((Flags & RF_IgnoreMissingLocals) &&
873               "Referenced block not in value map!");
874    }
875  }
876
877  // Remap attached metadata.
878  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
879  I->getAllMetadata(MDs);
880  for (const auto &MI : MDs) {
881    MDNode *Old = MI.second;
882    MDNode *New = cast_or_null<MDNode>(mapMetadata(Old));
883    if (New != Old)
884      I->setMetadata(MI.first, New);
885  }
886
887  if (!TypeMapper)
888    return;
889
890  // If the instruction's type is being remapped, do so now.
891  if (auto CS = CallSite(I)) {
892    SmallVector<Type *, 3> Tys;
893    FunctionType *FTy = CS.getFunctionType();
894    Tys.reserve(FTy->getNumParams());
895    for (Type *Ty : FTy->params())
896      Tys.push_back(TypeMapper->remapType(Ty));
897    CS.mutateFunctionType(FunctionType::get(
898        TypeMapper->remapType(I->getType()), Tys, FTy->isVarArg()));
899
900    LLVMContext &C = CS->getContext();
901    AttributeList Attrs = CS.getAttributes();
902    for (unsigned i = 0; i < Attrs.getNumAttrSets(); ++i) {
903      if (Attrs.hasAttribute(i, Attribute::ByVal)) {
904        Type *Ty = Attrs.getAttribute(i, Attribute::ByVal).getValueAsType();
905        if (!Ty)
906          continue;
907
908        Attrs = Attrs.removeAttribute(C, i, Attribute::ByVal);
909        Attrs = Attrs.addAttribute(
910            C, i, Attribute::getWithByValType(C, TypeMapper->remapType(Ty)));
911      }
912    }
913    CS.setAttributes(Attrs);
914    return;
915  }
916  if (auto *AI = dyn_cast<AllocaInst>(I))
917    AI->setAllocatedType(TypeMapper->remapType(AI->getAllocatedType()));
918  if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
919    GEP->setSourceElementType(
920        TypeMapper->remapType(GEP->getSourceElementType()));
921    GEP->setResultElementType(
922        TypeMapper->remapType(GEP->getResultElementType()));
923  }
924  I->mutateType(TypeMapper->remapType(I->getType()));
925}
926
927void Mapper::remapGlobalObjectMetadata(GlobalObject &GO) {
928  SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
929  GO.getAllMetadata(MDs);
930  GO.clearMetadata();
931  for (const auto &I : MDs)
932    GO.addMetadata(I.first, *cast<MDNode>(mapMetadata(I.second)));
933}
934
935void Mapper::remapFunction(Function &F) {
936  // Remap the operands.
937  for (Use &Op : F.operands())
938    if (Op)
939      Op = mapValue(Op);
940
941  // Remap the metadata attachments.
942  remapGlobalObjectMetadata(F);
943
944  // Remap the argument types.
945  if (TypeMapper)
946    for (Argument &A : F.args())
947      A.mutateType(TypeMapper->remapType(A.getType()));
948
949  // Remap the instructions.
950  for (BasicBlock &BB : F)
951    for (Instruction &I : BB)
952      remapInstruction(&I);
953}
954
955void Mapper::mapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
956                                  bool IsOldCtorDtor,
957                                  ArrayRef<Constant *> NewMembers) {
958  SmallVector<Constant *, 16> Elements;
959  if (InitPrefix) {
960    unsigned NumElements =
961        cast<ArrayType>(InitPrefix->getType())->getNumElements();
962    for (unsigned I = 0; I != NumElements; ++I)
963      Elements.push_back(InitPrefix->getAggregateElement(I));
964  }
965
966  PointerType *VoidPtrTy;
967  Type *EltTy;
968  if (IsOldCtorDtor) {
969    // FIXME: This upgrade is done during linking to support the C API.  See
970    // also IRLinker::linkAppendingVarProto() in IRMover.cpp.
971    VoidPtrTy = Type::getInt8Ty(GV.getContext())->getPointerTo();
972    auto &ST = *cast<StructType>(NewMembers.front()->getType());
973    Type *Tys[3] = {ST.getElementType(0), ST.getElementType(1), VoidPtrTy};
974    EltTy = StructType::get(GV.getContext(), Tys, false);
975  }
976
977  for (auto *V : NewMembers) {
978    Constant *NewV;
979    if (IsOldCtorDtor) {
980      auto *S = cast<ConstantStruct>(V);
981      auto *E1 = cast<Constant>(mapValue(S->getOperand(0)));
982      auto *E2 = cast<Constant>(mapValue(S->getOperand(1)));
983      Constant *Null = Constant::getNullValue(VoidPtrTy);
984      NewV = ConstantStruct::get(cast<StructType>(EltTy), E1, E2, Null);
985    } else {
986      NewV = cast_or_null<Constant>(mapValue(V));
987    }
988    Elements.push_back(NewV);
989  }
990
991  GV.setInitializer(ConstantArray::get(
992      cast<ArrayType>(GV.getType()->getElementType()), Elements));
993}
994
995void Mapper::scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
996                                          unsigned MCID) {
997  assert(AlreadyScheduled.insert(&GV).second && "Should not reschedule");
998  assert(MCID < MCs.size() && "Invalid mapping context");
999
1000  WorklistEntry WE;
1001  WE.Kind = WorklistEntry::MapGlobalInit;
1002  WE.MCID = MCID;
1003  WE.Data.GVInit.GV = &GV;
1004  WE.Data.GVInit.Init = &Init;
1005  Worklist.push_back(WE);
1006}
1007
1008void Mapper::scheduleMapAppendingVariable(GlobalVariable &GV,
1009                                          Constant *InitPrefix,
1010                                          bool IsOldCtorDtor,
1011                                          ArrayRef<Constant *> NewMembers,
1012                                          unsigned MCID) {
1013  assert(AlreadyScheduled.insert(&GV).second && "Should not reschedule");
1014  assert(MCID < MCs.size() && "Invalid mapping context");
1015
1016  WorklistEntry WE;
1017  WE.Kind = WorklistEntry::MapAppendingVar;
1018  WE.MCID = MCID;
1019  WE.Data.AppendingGV.GV = &GV;
1020  WE.Data.AppendingGV.InitPrefix = InitPrefix;
1021  WE.AppendingGVIsOldCtorDtor = IsOldCtorDtor;
1022  WE.AppendingGVNumNewMembers = NewMembers.size();
1023  Worklist.push_back(WE);
1024  AppendingInits.append(NewMembers.begin(), NewMembers.end());
1025}
1026
1027void Mapper::scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS,
1028                                             Constant &Target, unsigned MCID) {
1029  assert(AlreadyScheduled.insert(&GIS).second && "Should not reschedule");
1030  assert(MCID < MCs.size() && "Invalid mapping context");
1031
1032  WorklistEntry WE;
1033  WE.Kind = WorklistEntry::MapGlobalIndirectSymbol;
1034  WE.MCID = MCID;
1035  WE.Data.GlobalIndirectSymbol.GIS = &GIS;
1036  WE.Data.GlobalIndirectSymbol.Target = &Target;
1037  Worklist.push_back(WE);
1038}
1039
1040void Mapper::scheduleRemapFunction(Function &F, unsigned MCID) {
1041  assert(AlreadyScheduled.insert(&F).second && "Should not reschedule");
1042  assert(MCID < MCs.size() && "Invalid mapping context");
1043
1044  WorklistEntry WE;
1045  WE.Kind = WorklistEntry::RemapFunction;
1046  WE.MCID = MCID;
1047  WE.Data.RemapF = &F;
1048  Worklist.push_back(WE);
1049}
1050
1051void Mapper::addFlags(RemapFlags Flags) {
1052  assert(!hasWorkToDo() && "Expected to have flushed the worklist");
1053  this->Flags = this->Flags | Flags;
1054}
1055
1056static Mapper *getAsMapper(void *pImpl) {
1057  return reinterpret_cast<Mapper *>(pImpl);
1058}
1059
1060namespace {
1061
1062class FlushingMapper {
1063  Mapper &M;
1064
1065public:
1066  explicit FlushingMapper(void *pImpl) : M(*getAsMapper(pImpl)) {
1067    assert(!M.hasWorkToDo() && "Expected to be flushed");
1068  }
1069
1070  ~FlushingMapper() { M.flush(); }
1071
1072  Mapper *operator->() const { return &M; }
1073};
1074
1075} // end anonymous namespace
1076
1077ValueMapper::ValueMapper(ValueToValueMapTy &VM, RemapFlags Flags,
1078                         ValueMapTypeRemapper *TypeMapper,
1079                         ValueMaterializer *Materializer)
1080    : pImpl(new Mapper(VM, Flags, TypeMapper, Materializer)) {}
1081
1082ValueMapper::~ValueMapper() { delete getAsMapper(pImpl); }
1083
1084unsigned
1085ValueMapper::registerAlternateMappingContext(ValueToValueMapTy &VM,
1086                                             ValueMaterializer *Materializer) {
1087  return getAsMapper(pImpl)->registerAlternateMappingContext(VM, Materializer);
1088}
1089
1090void ValueMapper::addFlags(RemapFlags Flags) {
1091  FlushingMapper(pImpl)->addFlags(Flags);
1092}
1093
1094Value *ValueMapper::mapValue(const Value &V) {
1095  return FlushingMapper(pImpl)->mapValue(&V);
1096}
1097
1098Constant *ValueMapper::mapConstant(const Constant &C) {
1099  return cast_or_null<Constant>(mapValue(C));
1100}
1101
1102Metadata *ValueMapper::mapMetadata(const Metadata &MD) {
1103  return FlushingMapper(pImpl)->mapMetadata(&MD);
1104}
1105
1106MDNode *ValueMapper::mapMDNode(const MDNode &N) {
1107  return cast_or_null<MDNode>(mapMetadata(N));
1108}
1109
1110void ValueMapper::remapInstruction(Instruction &I) {
1111  FlushingMapper(pImpl)->remapInstruction(&I);
1112}
1113
1114void ValueMapper::remapFunction(Function &F) {
1115  FlushingMapper(pImpl)->remapFunction(F);
1116}
1117
1118void ValueMapper::scheduleMapGlobalInitializer(GlobalVariable &GV,
1119                                               Constant &Init,
1120                                               unsigned MCID) {
1121  getAsMapper(pImpl)->scheduleMapGlobalInitializer(GV, Init, MCID);
1122}
1123
1124void ValueMapper::scheduleMapAppendingVariable(GlobalVariable &GV,
1125                                               Constant *InitPrefix,
1126                                               bool IsOldCtorDtor,
1127                                               ArrayRef<Constant *> NewMembers,
1128                                               unsigned MCID) {
1129  getAsMapper(pImpl)->scheduleMapAppendingVariable(
1130      GV, InitPrefix, IsOldCtorDtor, NewMembers, MCID);
1131}
1132
1133void ValueMapper::scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS,
1134                                                  Constant &Target,
1135                                                  unsigned MCID) {
1136  getAsMapper(pImpl)->scheduleMapGlobalIndirectSymbol(GIS, Target, MCID);
1137}
1138
1139void ValueMapper::scheduleRemapFunction(Function &F, unsigned MCID) {
1140  getAsMapper(pImpl)->scheduleRemapFunction(F, MCID);
1141}
1142