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1 //===- lib/Linker/IRMover.cpp ---------------------------------------------===//
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 #include "llvm/Linker/IRMover.h"
11 #include "LinkDiagnosticInfo.h"
12 #include "llvm/ADT/SetVector.h"
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/Triple.h"
15 #include "llvm/IR/Constants.h"
16 #include "llvm/IR/DebugInfo.h"
17 #include "llvm/IR/DiagnosticPrinter.h"
18 #include "llvm/IR/GVMaterializer.h"
19 #include "llvm/IR/Intrinsics.h"
20 #include "llvm/IR/TypeFinder.h"
21 #include "llvm/Support/Error.h"
22 #include "llvm/Transforms/Utils/Cloning.h"
23 #include <utility>
24 using namespace llvm;
25 
26 //===----------------------------------------------------------------------===//
27 // TypeMap implementation.
28 //===----------------------------------------------------------------------===//
29 
30 namespace {
31 class TypeMapTy : public ValueMapTypeRemapper {
32   /// This is a mapping from a source type to a destination type to use.
33   DenseMap<Type *, Type *> MappedTypes;
34 
35   /// When checking to see if two subgraphs are isomorphic, we speculatively
36   /// add types to MappedTypes, but keep track of them here in case we need to
37   /// roll back.
38   SmallVector<Type *, 16> SpeculativeTypes;
39 
40   SmallVector<StructType *, 16> SpeculativeDstOpaqueTypes;
41 
42   /// This is a list of non-opaque structs in the source module that are mapped
43   /// to an opaque struct in the destination module.
44   SmallVector<StructType *, 16> SrcDefinitionsToResolve;
45 
46   /// This is the set of opaque types in the destination modules who are
47   /// getting a body from the source module.
48   SmallPtrSet<StructType *, 16> DstResolvedOpaqueTypes;
49 
50 public:
TypeMapTy(IRMover::IdentifiedStructTypeSet & DstStructTypesSet)51   TypeMapTy(IRMover::IdentifiedStructTypeSet &DstStructTypesSet)
52       : DstStructTypesSet(DstStructTypesSet) {}
53 
54   IRMover::IdentifiedStructTypeSet &DstStructTypesSet;
55   /// Indicate that the specified type in the destination module is conceptually
56   /// equivalent to the specified type in the source module.
57   void addTypeMapping(Type *DstTy, Type *SrcTy);
58 
59   /// Produce a body for an opaque type in the dest module from a type
60   /// definition in the source module.
61   void linkDefinedTypeBodies();
62 
63   /// Return the mapped type to use for the specified input type from the
64   /// source module.
65   Type *get(Type *SrcTy);
66   Type *get(Type *SrcTy, SmallPtrSet<StructType *, 8> &Visited);
67 
68   void finishType(StructType *DTy, StructType *STy, ArrayRef<Type *> ETypes);
69 
get(FunctionType * T)70   FunctionType *get(FunctionType *T) {
71     return cast<FunctionType>(get((Type *)T));
72   }
73 
74 private:
remapType(Type * SrcTy)75   Type *remapType(Type *SrcTy) override { return get(SrcTy); }
76 
77   bool areTypesIsomorphic(Type *DstTy, Type *SrcTy);
78 };
79 }
80 
addTypeMapping(Type * DstTy,Type * SrcTy)81 void TypeMapTy::addTypeMapping(Type *DstTy, Type *SrcTy) {
82   assert(SpeculativeTypes.empty());
83   assert(SpeculativeDstOpaqueTypes.empty());
84 
85   // Check to see if these types are recursively isomorphic and establish a
86   // mapping between them if so.
87   if (!areTypesIsomorphic(DstTy, SrcTy)) {
88     // Oops, they aren't isomorphic.  Just discard this request by rolling out
89     // any speculative mappings we've established.
90     for (Type *Ty : SpeculativeTypes)
91       MappedTypes.erase(Ty);
92 
93     SrcDefinitionsToResolve.resize(SrcDefinitionsToResolve.size() -
94                                    SpeculativeDstOpaqueTypes.size());
95     for (StructType *Ty : SpeculativeDstOpaqueTypes)
96       DstResolvedOpaqueTypes.erase(Ty);
97   } else {
98     for (Type *Ty : SpeculativeTypes)
99       if (auto *STy = dyn_cast<StructType>(Ty))
100         if (STy->hasName())
101           STy->setName("");
102   }
103   SpeculativeTypes.clear();
104   SpeculativeDstOpaqueTypes.clear();
105 }
106 
107 /// Recursively walk this pair of types, returning true if they are isomorphic,
108 /// false if they are not.
areTypesIsomorphic(Type * DstTy,Type * SrcTy)109 bool TypeMapTy::areTypesIsomorphic(Type *DstTy, Type *SrcTy) {
110   // Two types with differing kinds are clearly not isomorphic.
111   if (DstTy->getTypeID() != SrcTy->getTypeID())
112     return false;
113 
114   // If we have an entry in the MappedTypes table, then we have our answer.
115   Type *&Entry = MappedTypes[SrcTy];
116   if (Entry)
117     return Entry == DstTy;
118 
119   // Two identical types are clearly isomorphic.  Remember this
120   // non-speculatively.
121   if (DstTy == SrcTy) {
122     Entry = DstTy;
123     return true;
124   }
125 
126   // Okay, we have two types with identical kinds that we haven't seen before.
127 
128   // If this is an opaque struct type, special case it.
129   if (StructType *SSTy = dyn_cast<StructType>(SrcTy)) {
130     // Mapping an opaque type to any struct, just keep the dest struct.
131     if (SSTy->isOpaque()) {
132       Entry = DstTy;
133       SpeculativeTypes.push_back(SrcTy);
134       return true;
135     }
136 
137     // Mapping a non-opaque source type to an opaque dest.  If this is the first
138     // type that we're mapping onto this destination type then we succeed.  Keep
139     // the dest, but fill it in later. If this is the second (different) type
140     // that we're trying to map onto the same opaque type then we fail.
141     if (cast<StructType>(DstTy)->isOpaque()) {
142       // We can only map one source type onto the opaque destination type.
143       if (!DstResolvedOpaqueTypes.insert(cast<StructType>(DstTy)).second)
144         return false;
145       SrcDefinitionsToResolve.push_back(SSTy);
146       SpeculativeTypes.push_back(SrcTy);
147       SpeculativeDstOpaqueTypes.push_back(cast<StructType>(DstTy));
148       Entry = DstTy;
149       return true;
150     }
151   }
152 
153   // If the number of subtypes disagree between the two types, then we fail.
154   if (SrcTy->getNumContainedTypes() != DstTy->getNumContainedTypes())
155     return false;
156 
157   // Fail if any of the extra properties (e.g. array size) of the type disagree.
158   if (isa<IntegerType>(DstTy))
159     return false; // bitwidth disagrees.
160   if (PointerType *PT = dyn_cast<PointerType>(DstTy)) {
161     if (PT->getAddressSpace() != cast<PointerType>(SrcTy)->getAddressSpace())
162       return false;
163 
164   } else if (FunctionType *FT = dyn_cast<FunctionType>(DstTy)) {
165     if (FT->isVarArg() != cast<FunctionType>(SrcTy)->isVarArg())
166       return false;
167   } else if (StructType *DSTy = dyn_cast<StructType>(DstTy)) {
168     StructType *SSTy = cast<StructType>(SrcTy);
169     if (DSTy->isLiteral() != SSTy->isLiteral() ||
170         DSTy->isPacked() != SSTy->isPacked())
171       return false;
172   } else if (ArrayType *DATy = dyn_cast<ArrayType>(DstTy)) {
173     if (DATy->getNumElements() != cast<ArrayType>(SrcTy)->getNumElements())
174       return false;
175   } else if (VectorType *DVTy = dyn_cast<VectorType>(DstTy)) {
176     if (DVTy->getNumElements() != cast<VectorType>(SrcTy)->getNumElements())
177       return false;
178   }
179 
180   // Otherwise, we speculate that these two types will line up and recursively
181   // check the subelements.
182   Entry = DstTy;
183   SpeculativeTypes.push_back(SrcTy);
184 
185   for (unsigned I = 0, E = SrcTy->getNumContainedTypes(); I != E; ++I)
186     if (!areTypesIsomorphic(DstTy->getContainedType(I),
187                             SrcTy->getContainedType(I)))
188       return false;
189 
190   // If everything seems to have lined up, then everything is great.
191   return true;
192 }
193 
linkDefinedTypeBodies()194 void TypeMapTy::linkDefinedTypeBodies() {
195   SmallVector<Type *, 16> Elements;
196   for (StructType *SrcSTy : SrcDefinitionsToResolve) {
197     StructType *DstSTy = cast<StructType>(MappedTypes[SrcSTy]);
198     assert(DstSTy->isOpaque());
199 
200     // Map the body of the source type over to a new body for the dest type.
201     Elements.resize(SrcSTy->getNumElements());
202     for (unsigned I = 0, E = Elements.size(); I != E; ++I)
203       Elements[I] = get(SrcSTy->getElementType(I));
204 
205     DstSTy->setBody(Elements, SrcSTy->isPacked());
206     DstStructTypesSet.switchToNonOpaque(DstSTy);
207   }
208   SrcDefinitionsToResolve.clear();
209   DstResolvedOpaqueTypes.clear();
210 }
211 
finishType(StructType * DTy,StructType * STy,ArrayRef<Type * > ETypes)212 void TypeMapTy::finishType(StructType *DTy, StructType *STy,
213                            ArrayRef<Type *> ETypes) {
214   DTy->setBody(ETypes, STy->isPacked());
215 
216   // Steal STy's name.
217   if (STy->hasName()) {
218     SmallString<16> TmpName = STy->getName();
219     STy->setName("");
220     DTy->setName(TmpName);
221   }
222 
223   DstStructTypesSet.addNonOpaque(DTy);
224 }
225 
get(Type * Ty)226 Type *TypeMapTy::get(Type *Ty) {
227   SmallPtrSet<StructType *, 8> Visited;
228   return get(Ty, Visited);
229 }
230 
get(Type * Ty,SmallPtrSet<StructType *,8> & Visited)231 Type *TypeMapTy::get(Type *Ty, SmallPtrSet<StructType *, 8> &Visited) {
232   // If we already have an entry for this type, return it.
233   Type **Entry = &MappedTypes[Ty];
234   if (*Entry)
235     return *Entry;
236 
237   // These are types that LLVM itself will unique.
238   bool IsUniqued = !isa<StructType>(Ty) || cast<StructType>(Ty)->isLiteral();
239 
240 #ifndef NDEBUG
241   if (!IsUniqued) {
242     for (auto &Pair : MappedTypes) {
243       assert(!(Pair.first != Ty && Pair.second == Ty) &&
244              "mapping to a source type");
245     }
246   }
247 #endif
248 
249   if (!IsUniqued && !Visited.insert(cast<StructType>(Ty)).second) {
250     StructType *DTy = StructType::create(Ty->getContext());
251     return *Entry = DTy;
252   }
253 
254   // If this is not a recursive type, then just map all of the elements and
255   // then rebuild the type from inside out.
256   SmallVector<Type *, 4> ElementTypes;
257 
258   // If there are no element types to map, then the type is itself.  This is
259   // true for the anonymous {} struct, things like 'float', integers, etc.
260   if (Ty->getNumContainedTypes() == 0 && IsUniqued)
261     return *Entry = Ty;
262 
263   // Remap all of the elements, keeping track of whether any of them change.
264   bool AnyChange = false;
265   ElementTypes.resize(Ty->getNumContainedTypes());
266   for (unsigned I = 0, E = Ty->getNumContainedTypes(); I != E; ++I) {
267     ElementTypes[I] = get(Ty->getContainedType(I), Visited);
268     AnyChange |= ElementTypes[I] != Ty->getContainedType(I);
269   }
270 
271   // If we found our type while recursively processing stuff, just use it.
272   Entry = &MappedTypes[Ty];
273   if (*Entry) {
274     if (auto *DTy = dyn_cast<StructType>(*Entry)) {
275       if (DTy->isOpaque()) {
276         auto *STy = cast<StructType>(Ty);
277         finishType(DTy, STy, ElementTypes);
278       }
279     }
280     return *Entry;
281   }
282 
283   // If all of the element types mapped directly over and the type is not
284   // a nomed struct, then the type is usable as-is.
285   if (!AnyChange && IsUniqued)
286     return *Entry = Ty;
287 
288   // Otherwise, rebuild a modified type.
289   switch (Ty->getTypeID()) {
290   default:
291     llvm_unreachable("unknown derived type to remap");
292   case Type::ArrayTyID:
293     return *Entry = ArrayType::get(ElementTypes[0],
294                                    cast<ArrayType>(Ty)->getNumElements());
295   case Type::VectorTyID:
296     return *Entry = VectorType::get(ElementTypes[0],
297                                     cast<VectorType>(Ty)->getNumElements());
298   case Type::PointerTyID:
299     return *Entry = PointerType::get(ElementTypes[0],
300                                      cast<PointerType>(Ty)->getAddressSpace());
301   case Type::FunctionTyID:
302     return *Entry = FunctionType::get(ElementTypes[0],
303                                       makeArrayRef(ElementTypes).slice(1),
304                                       cast<FunctionType>(Ty)->isVarArg());
305   case Type::StructTyID: {
306     auto *STy = cast<StructType>(Ty);
307     bool IsPacked = STy->isPacked();
308     if (IsUniqued)
309       return *Entry = StructType::get(Ty->getContext(), ElementTypes, IsPacked);
310 
311     // If the type is opaque, we can just use it directly.
312     if (STy->isOpaque()) {
313       DstStructTypesSet.addOpaque(STy);
314       return *Entry = Ty;
315     }
316 
317     if (StructType *OldT =
318             DstStructTypesSet.findNonOpaque(ElementTypes, IsPacked)) {
319       STy->setName("");
320       return *Entry = OldT;
321     }
322 
323     if (!AnyChange) {
324       DstStructTypesSet.addNonOpaque(STy);
325       return *Entry = Ty;
326     }
327 
328     StructType *DTy = StructType::create(Ty->getContext());
329     finishType(DTy, STy, ElementTypes);
330     return *Entry = DTy;
331   }
332   }
333 }
334 
LinkDiagnosticInfo(DiagnosticSeverity Severity,const Twine & Msg)335 LinkDiagnosticInfo::LinkDiagnosticInfo(DiagnosticSeverity Severity,
336                                        const Twine &Msg)
337     : DiagnosticInfo(DK_Linker, Severity), Msg(Msg) {}
print(DiagnosticPrinter & DP) const338 void LinkDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
339 
340 //===----------------------------------------------------------------------===//
341 // IRLinker implementation.
342 //===----------------------------------------------------------------------===//
343 
344 namespace {
345 class IRLinker;
346 
347 /// Creates prototypes for functions that are lazily linked on the fly. This
348 /// speeds up linking for modules with many/ lazily linked functions of which
349 /// few get used.
350 class GlobalValueMaterializer final : public ValueMaterializer {
351   IRLinker &TheIRLinker;
352 
353 public:
GlobalValueMaterializer(IRLinker & TheIRLinker)354   GlobalValueMaterializer(IRLinker &TheIRLinker) : TheIRLinker(TheIRLinker) {}
355   Value *materialize(Value *V) override;
356 };
357 
358 class LocalValueMaterializer final : public ValueMaterializer {
359   IRLinker &TheIRLinker;
360 
361 public:
LocalValueMaterializer(IRLinker & TheIRLinker)362   LocalValueMaterializer(IRLinker &TheIRLinker) : TheIRLinker(TheIRLinker) {}
363   Value *materialize(Value *V) override;
364 };
365 
366 /// Type of the Metadata map in \a ValueToValueMapTy.
367 typedef DenseMap<const Metadata *, TrackingMDRef> MDMapT;
368 
369 /// This is responsible for keeping track of the state used for moving data
370 /// from SrcM to DstM.
371 class IRLinker {
372   Module &DstM;
373   std::unique_ptr<Module> SrcM;
374 
375   /// See IRMover::move().
376   std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor;
377 
378   TypeMapTy TypeMap;
379   GlobalValueMaterializer GValMaterializer;
380   LocalValueMaterializer LValMaterializer;
381 
382   /// A metadata map that's shared between IRLinker instances.
383   MDMapT &SharedMDs;
384 
385   /// Mapping of values from what they used to be in Src, to what they are now
386   /// in DstM.  ValueToValueMapTy is a ValueMap, which involves some overhead
387   /// due to the use of Value handles which the Linker doesn't actually need,
388   /// but this allows us to reuse the ValueMapper code.
389   ValueToValueMapTy ValueMap;
390   ValueToValueMapTy AliasValueMap;
391 
392   DenseSet<GlobalValue *> ValuesToLink;
393   std::vector<GlobalValue *> Worklist;
394 
maybeAdd(GlobalValue * GV)395   void maybeAdd(GlobalValue *GV) {
396     if (ValuesToLink.insert(GV).second)
397       Worklist.push_back(GV);
398   }
399 
400   /// Set to true when all global value body linking is complete (including
401   /// lazy linking). Used to prevent metadata linking from creating new
402   /// references.
403   bool DoneLinkingBodies = false;
404 
405   /// The Error encountered during materialization. We use an Optional here to
406   /// avoid needing to manage an unconsumed success value.
407   Optional<Error> FoundError;
setError(Error E)408   void setError(Error E) {
409     if (E)
410       FoundError = std::move(E);
411   }
412 
413   /// Most of the errors produced by this module are inconvertible StringErrors.
414   /// This convenience function lets us return one of those more easily.
stringErr(const Twine & T)415   Error stringErr(const Twine &T) {
416     return make_error<StringError>(T, inconvertibleErrorCode());
417   }
418 
419   /// Entry point for mapping values and alternate context for mapping aliases.
420   ValueMapper Mapper;
421   unsigned AliasMCID;
422 
423   /// Handles cloning of a global values from the source module into
424   /// the destination module, including setting the attributes and visibility.
425   GlobalValue *copyGlobalValueProto(const GlobalValue *SGV, bool ForDefinition);
426 
emitWarning(const Twine & Message)427   void emitWarning(const Twine &Message) {
428     SrcM->getContext().diagnose(LinkDiagnosticInfo(DS_Warning, Message));
429   }
430 
431   /// Given a global in the source module, return the global in the
432   /// destination module that is being linked to, if any.
getLinkedToGlobal(const GlobalValue * SrcGV)433   GlobalValue *getLinkedToGlobal(const GlobalValue *SrcGV) {
434     // If the source has no name it can't link.  If it has local linkage,
435     // there is no name match-up going on.
436     if (!SrcGV->hasName() || SrcGV->hasLocalLinkage())
437       return nullptr;
438 
439     // Otherwise see if we have a match in the destination module's symtab.
440     GlobalValue *DGV = DstM.getNamedValue(SrcGV->getName());
441     if (!DGV)
442       return nullptr;
443 
444     // If we found a global with the same name in the dest module, but it has
445     // internal linkage, we are really not doing any linkage here.
446     if (DGV->hasLocalLinkage())
447       return nullptr;
448 
449     // Otherwise, we do in fact link to the destination global.
450     return DGV;
451   }
452 
453   void computeTypeMapping();
454 
455   Expected<Constant *> linkAppendingVarProto(GlobalVariable *DstGV,
456                                              const GlobalVariable *SrcGV);
457 
458   /// Given the GlobaValue \p SGV in the source module, and the matching
459   /// GlobalValue \p DGV (if any), return true if the linker will pull \p SGV
460   /// into the destination module.
461   ///
462   /// Note this code may call the client-provided \p AddLazyFor.
463   bool shouldLink(GlobalValue *DGV, GlobalValue &SGV);
464   Expected<Constant *> linkGlobalValueProto(GlobalValue *GV, bool ForAlias);
465 
466   Error linkModuleFlagsMetadata();
467 
468   void linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src);
469   Error linkFunctionBody(Function &Dst, Function &Src);
470   void linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src);
471   Error linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src);
472 
473   /// Functions that take care of cloning a specific global value type
474   /// into the destination module.
475   GlobalVariable *copyGlobalVariableProto(const GlobalVariable *SGVar);
476   Function *copyFunctionProto(const Function *SF);
477   GlobalValue *copyGlobalAliasProto(const GlobalAlias *SGA);
478 
479   void linkNamedMDNodes();
480 
481 public:
IRLinker(Module & DstM,MDMapT & SharedMDs,IRMover::IdentifiedStructTypeSet & Set,std::unique_ptr<Module> SrcM,ArrayRef<GlobalValue * > ValuesToLink,std::function<void (GlobalValue &,IRMover::ValueAdder)> AddLazyFor)482   IRLinker(Module &DstM, MDMapT &SharedMDs,
483            IRMover::IdentifiedStructTypeSet &Set, std::unique_ptr<Module> SrcM,
484            ArrayRef<GlobalValue *> ValuesToLink,
485            std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor)
486       : DstM(DstM), SrcM(std::move(SrcM)), AddLazyFor(std::move(AddLazyFor)),
487         TypeMap(Set), GValMaterializer(*this), LValMaterializer(*this),
488         SharedMDs(SharedMDs),
489         Mapper(ValueMap, RF_MoveDistinctMDs | RF_IgnoreMissingLocals, &TypeMap,
490                &GValMaterializer),
491         AliasMCID(Mapper.registerAlternateMappingContext(AliasValueMap,
492                                                          &LValMaterializer)) {
493     ValueMap.getMDMap() = std::move(SharedMDs);
494     for (GlobalValue *GV : ValuesToLink)
495       maybeAdd(GV);
496   }
~IRLinker()497   ~IRLinker() { SharedMDs = std::move(*ValueMap.getMDMap()); }
498 
499   Error run();
500   Value *materialize(Value *V, bool ForAlias);
501 };
502 }
503 
504 /// The LLVM SymbolTable class autorenames globals that conflict in the symbol
505 /// table. This is good for all clients except for us. Go through the trouble
506 /// to force this back.
forceRenaming(GlobalValue * GV,StringRef Name)507 static void forceRenaming(GlobalValue *GV, StringRef Name) {
508   // If the global doesn't force its name or if it already has the right name,
509   // there is nothing for us to do.
510   if (GV->hasLocalLinkage() || GV->getName() == Name)
511     return;
512 
513   Module *M = GV->getParent();
514 
515   // If there is a conflict, rename the conflict.
516   if (GlobalValue *ConflictGV = M->getNamedValue(Name)) {
517     GV->takeName(ConflictGV);
518     ConflictGV->setName(Name); // This will cause ConflictGV to get renamed
519     assert(ConflictGV->getName() != Name && "forceRenaming didn't work");
520   } else {
521     GV->setName(Name); // Force the name back
522   }
523 }
524 
materialize(Value * SGV)525 Value *GlobalValueMaterializer::materialize(Value *SGV) {
526   return TheIRLinker.materialize(SGV, false);
527 }
528 
materialize(Value * SGV)529 Value *LocalValueMaterializer::materialize(Value *SGV) {
530   return TheIRLinker.materialize(SGV, true);
531 }
532 
materialize(Value * V,bool ForAlias)533 Value *IRLinker::materialize(Value *V, bool ForAlias) {
534   auto *SGV = dyn_cast<GlobalValue>(V);
535   if (!SGV)
536     return nullptr;
537 
538   Expected<Constant *> NewProto = linkGlobalValueProto(SGV, ForAlias);
539   if (!NewProto) {
540     setError(NewProto.takeError());
541     return nullptr;
542   }
543   if (!*NewProto)
544     return nullptr;
545 
546   GlobalValue *New = dyn_cast<GlobalValue>(*NewProto);
547   if (!New)
548     return *NewProto;
549 
550   // If we already created the body, just return.
551   if (auto *F = dyn_cast<Function>(New)) {
552     if (!F->isDeclaration())
553       return New;
554   } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
555     if (V->hasInitializer() || V->hasAppendingLinkage())
556       return New;
557   } else {
558     auto *A = cast<GlobalAlias>(New);
559     if (A->getAliasee())
560       return New;
561   }
562 
563   // When linking a global for an alias, it will always be linked. However we
564   // need to check if it was not already scheduled to satify a reference from a
565   // regular global value initializer. We know if it has been schedule if the
566   // "New" GlobalValue that is mapped here for the alias is the same as the one
567   // already mapped. If there is an entry in the ValueMap but the value is
568   // different, it means that the value already had a definition in the
569   // destination module (linkonce for instance), but we need a new definition
570   // for the alias ("New" will be different.
571   if (ForAlias && ValueMap.lookup(SGV) == New)
572     return New;
573 
574   if (ForAlias || shouldLink(New, *SGV))
575     setError(linkGlobalValueBody(*New, *SGV));
576 
577   return New;
578 }
579 
580 /// Loop through the global variables in the src module and merge them into the
581 /// dest module.
copyGlobalVariableProto(const GlobalVariable * SGVar)582 GlobalVariable *IRLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
583   // No linking to be performed or linking from the source: simply create an
584   // identical version of the symbol over in the dest module... the
585   // initializer will be filled in later by LinkGlobalInits.
586   GlobalVariable *NewDGV =
587       new GlobalVariable(DstM, TypeMap.get(SGVar->getValueType()),
588                          SGVar->isConstant(), GlobalValue::ExternalLinkage,
589                          /*init*/ nullptr, SGVar->getName(),
590                          /*insertbefore*/ nullptr, SGVar->getThreadLocalMode(),
591                          SGVar->getType()->getAddressSpace());
592   NewDGV->setAlignment(SGVar->getAlignment());
593   return NewDGV;
594 }
595 
596 /// Link the function in the source module into the destination module if
597 /// needed, setting up mapping information.
copyFunctionProto(const Function * SF)598 Function *IRLinker::copyFunctionProto(const Function *SF) {
599   // If there is no linkage to be performed or we are linking from the source,
600   // bring SF over.
601   return Function::Create(TypeMap.get(SF->getFunctionType()),
602                           GlobalValue::ExternalLinkage, SF->getName(), &DstM);
603 }
604 
605 /// Set up prototypes for any aliases that come over from the source module.
copyGlobalAliasProto(const GlobalAlias * SGA)606 GlobalValue *IRLinker::copyGlobalAliasProto(const GlobalAlias *SGA) {
607   // If there is no linkage to be performed or we're linking from the source,
608   // bring over SGA.
609   auto *Ty = TypeMap.get(SGA->getValueType());
610   return GlobalAlias::create(Ty, SGA->getType()->getPointerAddressSpace(),
611                              GlobalValue::ExternalLinkage, SGA->getName(),
612                              &DstM);
613 }
614 
copyGlobalValueProto(const GlobalValue * SGV,bool ForDefinition)615 GlobalValue *IRLinker::copyGlobalValueProto(const GlobalValue *SGV,
616                                             bool ForDefinition) {
617   GlobalValue *NewGV;
618   if (auto *SGVar = dyn_cast<GlobalVariable>(SGV)) {
619     NewGV = copyGlobalVariableProto(SGVar);
620   } else if (auto *SF = dyn_cast<Function>(SGV)) {
621     NewGV = copyFunctionProto(SF);
622   } else {
623     if (ForDefinition)
624       NewGV = copyGlobalAliasProto(cast<GlobalAlias>(SGV));
625     else
626       NewGV = new GlobalVariable(
627           DstM, TypeMap.get(SGV->getValueType()),
628           /*isConstant*/ false, GlobalValue::ExternalLinkage,
629           /*init*/ nullptr, SGV->getName(),
630           /*insertbefore*/ nullptr, SGV->getThreadLocalMode(),
631           SGV->getType()->getAddressSpace());
632   }
633 
634   if (ForDefinition)
635     NewGV->setLinkage(SGV->getLinkage());
636   else if (SGV->hasExternalWeakLinkage())
637     NewGV->setLinkage(GlobalValue::ExternalWeakLinkage);
638 
639   NewGV->copyAttributesFrom(SGV);
640 
641   if (auto *NewGO = dyn_cast<GlobalObject>(NewGV)) {
642     // Metadata for global variables and function declarations is copied eagerly.
643     if (isa<GlobalVariable>(SGV) || SGV->isDeclaration())
644       NewGO->copyMetadata(cast<GlobalObject>(SGV), 0);
645   }
646 
647   // Remove these copied constants in case this stays a declaration, since
648   // they point to the source module. If the def is linked the values will
649   // be mapped in during linkFunctionBody.
650   if (auto *NewF = dyn_cast<Function>(NewGV)) {
651     NewF->setPersonalityFn(nullptr);
652     NewF->setPrefixData(nullptr);
653     NewF->setPrologueData(nullptr);
654   }
655 
656   return NewGV;
657 }
658 
659 /// Loop over all of the linked values to compute type mappings.  For example,
660 /// if we link "extern Foo *x" and "Foo *x = NULL", then we have two struct
661 /// types 'Foo' but one got renamed when the module was loaded into the same
662 /// LLVMContext.
computeTypeMapping()663 void IRLinker::computeTypeMapping() {
664   for (GlobalValue &SGV : SrcM->globals()) {
665     GlobalValue *DGV = getLinkedToGlobal(&SGV);
666     if (!DGV)
667       continue;
668 
669     if (!DGV->hasAppendingLinkage() || !SGV.hasAppendingLinkage()) {
670       TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
671       continue;
672     }
673 
674     // Unify the element type of appending arrays.
675     ArrayType *DAT = cast<ArrayType>(DGV->getValueType());
676     ArrayType *SAT = cast<ArrayType>(SGV.getValueType());
677     TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
678   }
679 
680   for (GlobalValue &SGV : *SrcM)
681     if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
682       TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
683 
684   for (GlobalValue &SGV : SrcM->aliases())
685     if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
686       TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
687 
688   // Incorporate types by name, scanning all the types in the source module.
689   // At this point, the destination module may have a type "%foo = { i32 }" for
690   // example.  When the source module got loaded into the same LLVMContext, if
691   // it had the same type, it would have been renamed to "%foo.42 = { i32 }".
692   std::vector<StructType *> Types = SrcM->getIdentifiedStructTypes();
693   for (StructType *ST : Types) {
694     if (!ST->hasName())
695       continue;
696 
697     // Check to see if there is a dot in the name followed by a digit.
698     size_t DotPos = ST->getName().rfind('.');
699     if (DotPos == 0 || DotPos == StringRef::npos ||
700         ST->getName().back() == '.' ||
701         !isdigit(static_cast<unsigned char>(ST->getName()[DotPos + 1])))
702       continue;
703 
704     // Check to see if the destination module has a struct with the prefix name.
705     StructType *DST = DstM.getTypeByName(ST->getName().substr(0, DotPos));
706     if (!DST)
707       continue;
708 
709     // Don't use it if this actually came from the source module. They're in
710     // the same LLVMContext after all. Also don't use it unless the type is
711     // actually used in the destination module. This can happen in situations
712     // like this:
713     //
714     //      Module A                         Module B
715     //      --------                         --------
716     //   %Z = type { %A }                %B = type { %C.1 }
717     //   %A = type { %B.1, [7 x i8] }    %C.1 = type { i8* }
718     //   %B.1 = type { %C }              %A.2 = type { %B.3, [5 x i8] }
719     //   %C = type { i8* }               %B.3 = type { %C.1 }
720     //
721     // When we link Module B with Module A, the '%B' in Module B is
722     // used. However, that would then use '%C.1'. But when we process '%C.1',
723     // we prefer to take the '%C' version. So we are then left with both
724     // '%C.1' and '%C' being used for the same types. This leads to some
725     // variables using one type and some using the other.
726     if (TypeMap.DstStructTypesSet.hasType(DST))
727       TypeMap.addTypeMapping(DST, ST);
728   }
729 
730   // Now that we have discovered all of the type equivalences, get a body for
731   // any 'opaque' types in the dest module that are now resolved.
732   TypeMap.linkDefinedTypeBodies();
733 }
734 
getArrayElements(const Constant * C,SmallVectorImpl<Constant * > & Dest)735 static void getArrayElements(const Constant *C,
736                              SmallVectorImpl<Constant *> &Dest) {
737   unsigned NumElements = cast<ArrayType>(C->getType())->getNumElements();
738 
739   for (unsigned i = 0; i != NumElements; ++i)
740     Dest.push_back(C->getAggregateElement(i));
741 }
742 
743 /// If there were any appending global variables, link them together now.
744 Expected<Constant *>
linkAppendingVarProto(GlobalVariable * DstGV,const GlobalVariable * SrcGV)745 IRLinker::linkAppendingVarProto(GlobalVariable *DstGV,
746                                 const GlobalVariable *SrcGV) {
747   Type *EltTy = cast<ArrayType>(TypeMap.get(SrcGV->getValueType()))
748                     ->getElementType();
749 
750   // FIXME: This upgrade is done during linking to support the C API.  Once the
751   // old form is deprecated, we should move this upgrade to
752   // llvm::UpgradeGlobalVariable() and simplify the logic here and in
753   // Mapper::mapAppendingVariable() in ValueMapper.cpp.
754   StringRef Name = SrcGV->getName();
755   bool IsNewStructor = false;
756   bool IsOldStructor = false;
757   if (Name == "llvm.global_ctors" || Name == "llvm.global_dtors") {
758     if (cast<StructType>(EltTy)->getNumElements() == 3)
759       IsNewStructor = true;
760     else
761       IsOldStructor = true;
762   }
763 
764   PointerType *VoidPtrTy = Type::getInt8Ty(SrcGV->getContext())->getPointerTo();
765   if (IsOldStructor) {
766     auto &ST = *cast<StructType>(EltTy);
767     Type *Tys[3] = {ST.getElementType(0), ST.getElementType(1), VoidPtrTy};
768     EltTy = StructType::get(SrcGV->getContext(), Tys, false);
769   }
770 
771   uint64_t DstNumElements = 0;
772   if (DstGV) {
773     ArrayType *DstTy = cast<ArrayType>(DstGV->getValueType());
774     DstNumElements = DstTy->getNumElements();
775 
776     if (!SrcGV->hasAppendingLinkage() || !DstGV->hasAppendingLinkage())
777       return stringErr(
778           "Linking globals named '" + SrcGV->getName() +
779           "': can only link appending global with another appending "
780           "global!");
781 
782     // Check to see that they two arrays agree on type.
783     if (EltTy != DstTy->getElementType())
784       return stringErr("Appending variables with different element types!");
785     if (DstGV->isConstant() != SrcGV->isConstant())
786       return stringErr("Appending variables linked with different const'ness!");
787 
788     if (DstGV->getAlignment() != SrcGV->getAlignment())
789       return stringErr(
790           "Appending variables with different alignment need to be linked!");
791 
792     if (DstGV->getVisibility() != SrcGV->getVisibility())
793       return stringErr(
794           "Appending variables with different visibility need to be linked!");
795 
796     if (DstGV->hasGlobalUnnamedAddr() != SrcGV->hasGlobalUnnamedAddr())
797       return stringErr(
798           "Appending variables with different unnamed_addr need to be linked!");
799 
800     if (DstGV->getSection() != SrcGV->getSection())
801       return stringErr(
802           "Appending variables with different section name need to be linked!");
803   }
804 
805   SmallVector<Constant *, 16> SrcElements;
806   getArrayElements(SrcGV->getInitializer(), SrcElements);
807 
808   if (IsNewStructor)
809     SrcElements.erase(
810         std::remove_if(SrcElements.begin(), SrcElements.end(),
811                        [this](Constant *E) {
812                          auto *Key = dyn_cast<GlobalValue>(
813                              E->getAggregateElement(2)->stripPointerCasts());
814                          if (!Key)
815                            return false;
816                          GlobalValue *DGV = getLinkedToGlobal(Key);
817                          return !shouldLink(DGV, *Key);
818                        }),
819         SrcElements.end());
820   uint64_t NewSize = DstNumElements + SrcElements.size();
821   ArrayType *NewType = ArrayType::get(EltTy, NewSize);
822 
823   // Create the new global variable.
824   GlobalVariable *NG = new GlobalVariable(
825       DstM, NewType, SrcGV->isConstant(), SrcGV->getLinkage(),
826       /*init*/ nullptr, /*name*/ "", DstGV, SrcGV->getThreadLocalMode(),
827       SrcGV->getType()->getAddressSpace());
828 
829   NG->copyAttributesFrom(SrcGV);
830   forceRenaming(NG, SrcGV->getName());
831 
832   Constant *Ret = ConstantExpr::getBitCast(NG, TypeMap.get(SrcGV->getType()));
833 
834   Mapper.scheduleMapAppendingVariable(*NG,
835                                       DstGV ? DstGV->getInitializer() : nullptr,
836                                       IsOldStructor, SrcElements);
837 
838   // Replace any uses of the two global variables with uses of the new
839   // global.
840   if (DstGV) {
841     DstGV->replaceAllUsesWith(ConstantExpr::getBitCast(NG, DstGV->getType()));
842     DstGV->eraseFromParent();
843   }
844 
845   return Ret;
846 }
847 
shouldLink(GlobalValue * DGV,GlobalValue & SGV)848 bool IRLinker::shouldLink(GlobalValue *DGV, GlobalValue &SGV) {
849   if (ValuesToLink.count(&SGV) || SGV.hasLocalLinkage())
850     return true;
851 
852   if (DGV && !DGV->isDeclarationForLinker())
853     return false;
854 
855   if (SGV.hasAvailableExternallyLinkage())
856     return true;
857 
858   if (SGV.isDeclaration() || DoneLinkingBodies)
859     return false;
860 
861   // Callback to the client to give a chance to lazily add the Global to the
862   // list of value to link.
863   bool LazilyAdded = false;
864   AddLazyFor(SGV, [this, &LazilyAdded](GlobalValue &GV) {
865     maybeAdd(&GV);
866     LazilyAdded = true;
867   });
868   return LazilyAdded;
869 }
870 
linkGlobalValueProto(GlobalValue * SGV,bool ForAlias)871 Expected<Constant *> IRLinker::linkGlobalValueProto(GlobalValue *SGV,
872                                                     bool ForAlias) {
873   GlobalValue *DGV = getLinkedToGlobal(SGV);
874 
875   bool ShouldLink = shouldLink(DGV, *SGV);
876 
877   // just missing from map
878   if (ShouldLink) {
879     auto I = ValueMap.find(SGV);
880     if (I != ValueMap.end())
881       return cast<Constant>(I->second);
882 
883     I = AliasValueMap.find(SGV);
884     if (I != AliasValueMap.end())
885       return cast<Constant>(I->second);
886   }
887 
888   if (!ShouldLink && ForAlias)
889     DGV = nullptr;
890 
891   // Handle the ultra special appending linkage case first.
892   assert(!DGV || SGV->hasAppendingLinkage() == DGV->hasAppendingLinkage());
893   if (SGV->hasAppendingLinkage())
894     return linkAppendingVarProto(cast_or_null<GlobalVariable>(DGV),
895                                  cast<GlobalVariable>(SGV));
896 
897   GlobalValue *NewGV;
898   if (DGV && !ShouldLink) {
899     NewGV = DGV;
900   } else {
901     // If we are done linking global value bodies (i.e. we are performing
902     // metadata linking), don't link in the global value due to this
903     // reference, simply map it to null.
904     if (DoneLinkingBodies)
905       return nullptr;
906 
907     NewGV = copyGlobalValueProto(SGV, ShouldLink);
908     if (ShouldLink || !ForAlias)
909       forceRenaming(NewGV, SGV->getName());
910   }
911 
912   // Overloaded intrinsics have overloaded types names as part of their
913   // names. If we renamed overloaded types we should rename the intrinsic
914   // as well.
915   if (Function *F = dyn_cast<Function>(NewGV))
916     if (auto Remangled = Intrinsic::remangleIntrinsicFunction(F))
917       NewGV = Remangled.getValue();
918 
919   if (ShouldLink || ForAlias) {
920     if (const Comdat *SC = SGV->getComdat()) {
921       if (auto *GO = dyn_cast<GlobalObject>(NewGV)) {
922         Comdat *DC = DstM.getOrInsertComdat(SC->getName());
923         DC->setSelectionKind(SC->getSelectionKind());
924         GO->setComdat(DC);
925       }
926     }
927   }
928 
929   if (!ShouldLink && ForAlias)
930     NewGV->setLinkage(GlobalValue::InternalLinkage);
931 
932   Constant *C = NewGV;
933   if (DGV)
934     C = ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
935 
936   if (DGV && NewGV != DGV) {
937     DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, DGV->getType()));
938     DGV->eraseFromParent();
939   }
940 
941   return C;
942 }
943 
944 /// Update the initializers in the Dest module now that all globals that may be
945 /// referenced are in Dest.
linkGlobalInit(GlobalVariable & Dst,GlobalVariable & Src)946 void IRLinker::linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src) {
947   // Figure out what the initializer looks like in the dest module.
948   Mapper.scheduleMapGlobalInitializer(Dst, *Src.getInitializer());
949 }
950 
951 /// Copy the source function over into the dest function and fix up references
952 /// to values. At this point we know that Dest is an external function, and
953 /// that Src is not.
linkFunctionBody(Function & Dst,Function & Src)954 Error IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
955   assert(Dst.isDeclaration() && !Src.isDeclaration());
956 
957   // Materialize if needed.
958   if (std::error_code EC = Src.materialize())
959     return errorCodeToError(EC);
960 
961   // Link in the operands without remapping.
962   if (Src.hasPrefixData())
963     Dst.setPrefixData(Src.getPrefixData());
964   if (Src.hasPrologueData())
965     Dst.setPrologueData(Src.getPrologueData());
966   if (Src.hasPersonalityFn())
967     Dst.setPersonalityFn(Src.getPersonalityFn());
968 
969   // Copy over the metadata attachments without remapping.
970   Dst.copyMetadata(&Src, 0);
971 
972   // Steal arguments and splice the body of Src into Dst.
973   Dst.stealArgumentListFrom(Src);
974   Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
975 
976   // Everything has been moved over.  Remap it.
977   Mapper.scheduleRemapFunction(Dst);
978   return Error::success();
979 }
980 
linkAliasBody(GlobalAlias & Dst,GlobalAlias & Src)981 void IRLinker::linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src) {
982   Mapper.scheduleMapGlobalAliasee(Dst, *Src.getAliasee(), AliasMCID);
983 }
984 
linkGlobalValueBody(GlobalValue & Dst,GlobalValue & Src)985 Error IRLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
986   if (auto *F = dyn_cast<Function>(&Src))
987     return linkFunctionBody(cast<Function>(Dst), *F);
988   if (auto *GVar = dyn_cast<GlobalVariable>(&Src)) {
989     linkGlobalInit(cast<GlobalVariable>(Dst), *GVar);
990     return Error::success();
991   }
992   linkAliasBody(cast<GlobalAlias>(Dst), cast<GlobalAlias>(Src));
993   return Error::success();
994 }
995 
996 /// Insert all of the named MDNodes in Src into the Dest module.
linkNamedMDNodes()997 void IRLinker::linkNamedMDNodes() {
998   const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
999   for (const NamedMDNode &NMD : SrcM->named_metadata()) {
1000     // Don't link module flags here. Do them separately.
1001     if (&NMD == SrcModFlags)
1002       continue;
1003     NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
1004     // Add Src elements into Dest node.
1005     for (const MDNode *Op : NMD.operands())
1006       DestNMD->addOperand(Mapper.mapMDNode(*Op));
1007   }
1008 }
1009 
1010 /// Merge the linker flags in Src into the Dest module.
linkModuleFlagsMetadata()1011 Error IRLinker::linkModuleFlagsMetadata() {
1012   // If the source module has no module flags, we are done.
1013   const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
1014   if (!SrcModFlags)
1015     return Error::success();
1016 
1017   // If the destination module doesn't have module flags yet, then just copy
1018   // over the source module's flags.
1019   NamedMDNode *DstModFlags = DstM.getOrInsertModuleFlagsMetadata();
1020   if (DstModFlags->getNumOperands() == 0) {
1021     for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
1022       DstModFlags->addOperand(SrcModFlags->getOperand(I));
1023 
1024     return Error::success();
1025   }
1026 
1027   // First build a map of the existing module flags and requirements.
1028   DenseMap<MDString *, std::pair<MDNode *, unsigned>> Flags;
1029   SmallSetVector<MDNode *, 16> Requirements;
1030   for (unsigned I = 0, E = DstModFlags->getNumOperands(); I != E; ++I) {
1031     MDNode *Op = DstModFlags->getOperand(I);
1032     ConstantInt *Behavior = mdconst::extract<ConstantInt>(Op->getOperand(0));
1033     MDString *ID = cast<MDString>(Op->getOperand(1));
1034 
1035     if (Behavior->getZExtValue() == Module::Require) {
1036       Requirements.insert(cast<MDNode>(Op->getOperand(2)));
1037     } else {
1038       Flags[ID] = std::make_pair(Op, I);
1039     }
1040   }
1041 
1042   // Merge in the flags from the source module, and also collect its set of
1043   // requirements.
1044   for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I) {
1045     MDNode *SrcOp = SrcModFlags->getOperand(I);
1046     ConstantInt *SrcBehavior =
1047         mdconst::extract<ConstantInt>(SrcOp->getOperand(0));
1048     MDString *ID = cast<MDString>(SrcOp->getOperand(1));
1049     MDNode *DstOp;
1050     unsigned DstIndex;
1051     std::tie(DstOp, DstIndex) = Flags.lookup(ID);
1052     unsigned SrcBehaviorValue = SrcBehavior->getZExtValue();
1053 
1054     // If this is a requirement, add it and continue.
1055     if (SrcBehaviorValue == Module::Require) {
1056       // If the destination module does not already have this requirement, add
1057       // it.
1058       if (Requirements.insert(cast<MDNode>(SrcOp->getOperand(2)))) {
1059         DstModFlags->addOperand(SrcOp);
1060       }
1061       continue;
1062     }
1063 
1064     // If there is no existing flag with this ID, just add it.
1065     if (!DstOp) {
1066       Flags[ID] = std::make_pair(SrcOp, DstModFlags->getNumOperands());
1067       DstModFlags->addOperand(SrcOp);
1068       continue;
1069     }
1070 
1071     // Otherwise, perform a merge.
1072     ConstantInt *DstBehavior =
1073         mdconst::extract<ConstantInt>(DstOp->getOperand(0));
1074     unsigned DstBehaviorValue = DstBehavior->getZExtValue();
1075 
1076     // If either flag has override behavior, handle it first.
1077     if (DstBehaviorValue == Module::Override) {
1078       // Diagnose inconsistent flags which both have override behavior.
1079       if (SrcBehaviorValue == Module::Override &&
1080           SrcOp->getOperand(2) != DstOp->getOperand(2))
1081         return stringErr("linking module flags '" + ID->getString() +
1082                          "': IDs have conflicting override values");
1083       continue;
1084     } else if (SrcBehaviorValue == Module::Override) {
1085       // Update the destination flag to that of the source.
1086       DstModFlags->setOperand(DstIndex, SrcOp);
1087       Flags[ID].first = SrcOp;
1088       continue;
1089     }
1090 
1091     // Diagnose inconsistent merge behavior types.
1092     if (SrcBehaviorValue != DstBehaviorValue)
1093       return stringErr("linking module flags '" + ID->getString() +
1094                        "': IDs have conflicting behaviors");
1095 
1096     auto replaceDstValue = [&](MDNode *New) {
1097       Metadata *FlagOps[] = {DstOp->getOperand(0), ID, New};
1098       MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
1099       DstModFlags->setOperand(DstIndex, Flag);
1100       Flags[ID].first = Flag;
1101     };
1102 
1103     // Perform the merge for standard behavior types.
1104     switch (SrcBehaviorValue) {
1105     case Module::Require:
1106     case Module::Override:
1107       llvm_unreachable("not possible");
1108     case Module::Error: {
1109       // Emit an error if the values differ.
1110       if (SrcOp->getOperand(2) != DstOp->getOperand(2))
1111         return stringErr("linking module flags '" + ID->getString() +
1112                          "': IDs have conflicting values");
1113       continue;
1114     }
1115     case Module::Warning: {
1116       // Emit a warning if the values differ.
1117       if (SrcOp->getOperand(2) != DstOp->getOperand(2)) {
1118         emitWarning("linking module flags '" + ID->getString() +
1119                     "': IDs have conflicting values");
1120       }
1121       continue;
1122     }
1123     case Module::Append: {
1124       MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
1125       MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
1126       SmallVector<Metadata *, 8> MDs;
1127       MDs.reserve(DstValue->getNumOperands() + SrcValue->getNumOperands());
1128       MDs.append(DstValue->op_begin(), DstValue->op_end());
1129       MDs.append(SrcValue->op_begin(), SrcValue->op_end());
1130 
1131       replaceDstValue(MDNode::get(DstM.getContext(), MDs));
1132       break;
1133     }
1134     case Module::AppendUnique: {
1135       SmallSetVector<Metadata *, 16> Elts;
1136       MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
1137       MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
1138       Elts.insert(DstValue->op_begin(), DstValue->op_end());
1139       Elts.insert(SrcValue->op_begin(), SrcValue->op_end());
1140 
1141       replaceDstValue(MDNode::get(DstM.getContext(),
1142                                   makeArrayRef(Elts.begin(), Elts.end())));
1143       break;
1144     }
1145     }
1146   }
1147 
1148   // Check all of the requirements.
1149   for (unsigned I = 0, E = Requirements.size(); I != E; ++I) {
1150     MDNode *Requirement = Requirements[I];
1151     MDString *Flag = cast<MDString>(Requirement->getOperand(0));
1152     Metadata *ReqValue = Requirement->getOperand(1);
1153 
1154     MDNode *Op = Flags[Flag].first;
1155     if (!Op || Op->getOperand(2) != ReqValue)
1156       return stringErr("linking module flags '" + Flag->getString() +
1157                        "': does not have the required value");
1158   }
1159   return Error::success();
1160 }
1161 
1162 // This function returns true if the triples match.
triplesMatch(const Triple & T0,const Triple & T1)1163 static bool triplesMatch(const Triple &T0, const Triple &T1) {
1164   // If vendor is apple, ignore the version number.
1165   if (T0.getVendor() == Triple::Apple)
1166     return T0.getArch() == T1.getArch() && T0.getSubArch() == T1.getSubArch() &&
1167            T0.getVendor() == T1.getVendor() && T0.getOS() == T1.getOS();
1168 
1169   return T0 == T1;
1170 }
1171 
1172 // This function returns the merged triple.
mergeTriples(const Triple & SrcTriple,const Triple & DstTriple)1173 static std::string mergeTriples(const Triple &SrcTriple,
1174                                 const Triple &DstTriple) {
1175   // If vendor is apple, pick the triple with the larger version number.
1176   if (SrcTriple.getVendor() == Triple::Apple)
1177     if (DstTriple.isOSVersionLT(SrcTriple))
1178       return SrcTriple.str();
1179 
1180   return DstTriple.str();
1181 }
1182 
run()1183 Error IRLinker::run() {
1184   // Ensure metadata materialized before value mapping.
1185   if (SrcM->getMaterializer())
1186     if (std::error_code EC = SrcM->getMaterializer()->materializeMetadata())
1187       return errorCodeToError(EC);
1188 
1189   // Inherit the target data from the source module if the destination module
1190   // doesn't have one already.
1191   if (DstM.getDataLayout().isDefault())
1192     DstM.setDataLayout(SrcM->getDataLayout());
1193 
1194   if (SrcM->getDataLayout() != DstM.getDataLayout()) {
1195     emitWarning("Linking two modules of different data layouts: '" +
1196                 SrcM->getModuleIdentifier() + "' is '" +
1197                 SrcM->getDataLayoutStr() + "' whereas '" +
1198                 DstM.getModuleIdentifier() + "' is '" +
1199                 DstM.getDataLayoutStr() + "'\n");
1200   }
1201 
1202   // Copy the target triple from the source to dest if the dest's is empty.
1203   if (DstM.getTargetTriple().empty() && !SrcM->getTargetTriple().empty())
1204     DstM.setTargetTriple(SrcM->getTargetTriple());
1205 
1206   Triple SrcTriple(SrcM->getTargetTriple()), DstTriple(DstM.getTargetTriple());
1207 
1208   if (!SrcM->getTargetTriple().empty() && !triplesMatch(SrcTriple, DstTriple))
1209     emitWarning("Linking two modules of different target triples: " +
1210                 SrcM->getModuleIdentifier() + "' is '" +
1211                 SrcM->getTargetTriple() + "' whereas '" +
1212                 DstM.getModuleIdentifier() + "' is '" + DstM.getTargetTriple() +
1213                 "'\n");
1214 
1215   DstM.setTargetTriple(mergeTriples(SrcTriple, DstTriple));
1216 
1217   // Append the module inline asm string.
1218   if (!SrcM->getModuleInlineAsm().empty()) {
1219     if (DstM.getModuleInlineAsm().empty())
1220       DstM.setModuleInlineAsm(SrcM->getModuleInlineAsm());
1221     else
1222       DstM.setModuleInlineAsm(DstM.getModuleInlineAsm() + "\n" +
1223                               SrcM->getModuleInlineAsm());
1224   }
1225 
1226   // Loop over all of the linked values to compute type mappings.
1227   computeTypeMapping();
1228 
1229   std::reverse(Worklist.begin(), Worklist.end());
1230   while (!Worklist.empty()) {
1231     GlobalValue *GV = Worklist.back();
1232     Worklist.pop_back();
1233 
1234     // Already mapped.
1235     if (ValueMap.find(GV) != ValueMap.end() ||
1236         AliasValueMap.find(GV) != AliasValueMap.end())
1237       continue;
1238 
1239     assert(!GV->isDeclaration());
1240     Mapper.mapValue(*GV);
1241     if (FoundError)
1242       return std::move(*FoundError);
1243   }
1244 
1245   // Note that we are done linking global value bodies. This prevents
1246   // metadata linking from creating new references.
1247   DoneLinkingBodies = true;
1248   Mapper.addFlags(RF_NullMapMissingGlobalValues);
1249 
1250   // Remap all of the named MDNodes in Src into the DstM module. We do this
1251   // after linking GlobalValues so that MDNodes that reference GlobalValues
1252   // are properly remapped.
1253   linkNamedMDNodes();
1254 
1255   // Merge the module flags into the DstM module.
1256   return linkModuleFlagsMetadata();
1257 }
1258 
KeyTy(ArrayRef<Type * > E,bool P)1259 IRMover::StructTypeKeyInfo::KeyTy::KeyTy(ArrayRef<Type *> E, bool P)
1260     : ETypes(E), IsPacked(P) {}
1261 
KeyTy(const StructType * ST)1262 IRMover::StructTypeKeyInfo::KeyTy::KeyTy(const StructType *ST)
1263     : ETypes(ST->elements()), IsPacked(ST->isPacked()) {}
1264 
operator ==(const KeyTy & That) const1265 bool IRMover::StructTypeKeyInfo::KeyTy::operator==(const KeyTy &That) const {
1266   return IsPacked == That.IsPacked && ETypes == That.ETypes;
1267 }
1268 
operator !=(const KeyTy & That) const1269 bool IRMover::StructTypeKeyInfo::KeyTy::operator!=(const KeyTy &That) const {
1270   return !this->operator==(That);
1271 }
1272 
getEmptyKey()1273 StructType *IRMover::StructTypeKeyInfo::getEmptyKey() {
1274   return DenseMapInfo<StructType *>::getEmptyKey();
1275 }
1276 
getTombstoneKey()1277 StructType *IRMover::StructTypeKeyInfo::getTombstoneKey() {
1278   return DenseMapInfo<StructType *>::getTombstoneKey();
1279 }
1280 
getHashValue(const KeyTy & Key)1281 unsigned IRMover::StructTypeKeyInfo::getHashValue(const KeyTy &Key) {
1282   return hash_combine(hash_combine_range(Key.ETypes.begin(), Key.ETypes.end()),
1283                       Key.IsPacked);
1284 }
1285 
getHashValue(const StructType * ST)1286 unsigned IRMover::StructTypeKeyInfo::getHashValue(const StructType *ST) {
1287   return getHashValue(KeyTy(ST));
1288 }
1289 
isEqual(const KeyTy & LHS,const StructType * RHS)1290 bool IRMover::StructTypeKeyInfo::isEqual(const KeyTy &LHS,
1291                                          const StructType *RHS) {
1292   if (RHS == getEmptyKey() || RHS == getTombstoneKey())
1293     return false;
1294   return LHS == KeyTy(RHS);
1295 }
1296 
isEqual(const StructType * LHS,const StructType * RHS)1297 bool IRMover::StructTypeKeyInfo::isEqual(const StructType *LHS,
1298                                          const StructType *RHS) {
1299   if (RHS == getEmptyKey() || RHS == getTombstoneKey())
1300     return LHS == RHS;
1301   return KeyTy(LHS) == KeyTy(RHS);
1302 }
1303 
addNonOpaque(StructType * Ty)1304 void IRMover::IdentifiedStructTypeSet::addNonOpaque(StructType *Ty) {
1305   assert(!Ty->isOpaque());
1306   NonOpaqueStructTypes.insert(Ty);
1307 }
1308 
switchToNonOpaque(StructType * Ty)1309 void IRMover::IdentifiedStructTypeSet::switchToNonOpaque(StructType *Ty) {
1310   assert(!Ty->isOpaque());
1311   NonOpaqueStructTypes.insert(Ty);
1312   bool Removed = OpaqueStructTypes.erase(Ty);
1313   (void)Removed;
1314   assert(Removed);
1315 }
1316 
addOpaque(StructType * Ty)1317 void IRMover::IdentifiedStructTypeSet::addOpaque(StructType *Ty) {
1318   assert(Ty->isOpaque());
1319   OpaqueStructTypes.insert(Ty);
1320 }
1321 
1322 StructType *
findNonOpaque(ArrayRef<Type * > ETypes,bool IsPacked)1323 IRMover::IdentifiedStructTypeSet::findNonOpaque(ArrayRef<Type *> ETypes,
1324                                                 bool IsPacked) {
1325   IRMover::StructTypeKeyInfo::KeyTy Key(ETypes, IsPacked);
1326   auto I = NonOpaqueStructTypes.find_as(Key);
1327   return I == NonOpaqueStructTypes.end() ? nullptr : *I;
1328 }
1329 
hasType(StructType * Ty)1330 bool IRMover::IdentifiedStructTypeSet::hasType(StructType *Ty) {
1331   if (Ty->isOpaque())
1332     return OpaqueStructTypes.count(Ty);
1333   auto I = NonOpaqueStructTypes.find(Ty);
1334   return I == NonOpaqueStructTypes.end() ? false : *I == Ty;
1335 }
1336 
IRMover(Module & M)1337 IRMover::IRMover(Module &M) : Composite(M) {
1338   TypeFinder StructTypes;
1339   StructTypes.run(M, true);
1340   for (StructType *Ty : StructTypes) {
1341     if (Ty->isOpaque())
1342       IdentifiedStructTypes.addOpaque(Ty);
1343     else
1344       IdentifiedStructTypes.addNonOpaque(Ty);
1345   }
1346 }
1347 
move(std::unique_ptr<Module> Src,ArrayRef<GlobalValue * > ValuesToLink,std::function<void (GlobalValue &,ValueAdder Add)> AddLazyFor)1348 Error IRMover::move(
1349     std::unique_ptr<Module> Src, ArrayRef<GlobalValue *> ValuesToLink,
1350     std::function<void(GlobalValue &, ValueAdder Add)> AddLazyFor) {
1351   IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
1352                        std::move(Src), ValuesToLink, std::move(AddLazyFor));
1353   Error E = TheIRLinker.run();
1354   Composite.dropTriviallyDeadConstantArrays();
1355   return E;
1356 }
1357