1 //===- lib/Linker/IRMover.cpp ---------------------------------------------===//
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 #include "llvm/Linker/IRMover.h"
10 #include "LinkDiagnosticInfo.h"
11 #include "llvm/ADT/SetVector.h"
12 #include "llvm/ADT/SmallString.h"
13 #include "llvm/ADT/Triple.h"
14 #include "llvm/IR/Constants.h"
15 #include "llvm/IR/DebugInfo.h"
16 #include "llvm/IR/DiagnosticPrinter.h"
17 #include "llvm/IR/GVMaterializer.h"
18 #include "llvm/IR/Intrinsics.h"
19 #include "llvm/IR/TypeFinder.h"
20 #include "llvm/Object/ModuleSymbolTable.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 // SrcTy and DstTy are recursively ismorphic. We clear names of SrcTy
99 // and all its descendants to lower amount of renaming in LLVM context
100 // Renaming occurs because we load all source modules to the same context
101 // and declaration with existing name gets renamed (i.e Foo -> Foo.42).
102 // As a result we may get several different types in the destination
103 // module, which are in fact the same.
104 for (Type *Ty : SpeculativeTypes)
105 if (auto *STy = dyn_cast<StructType>(Ty))
106 if (STy->hasName())
107 STy->setName("");
108 }
109 SpeculativeTypes.clear();
110 SpeculativeDstOpaqueTypes.clear();
111 }
112
113 /// Recursively walk this pair of types, returning true if they are isomorphic,
114 /// false if they are not.
areTypesIsomorphic(Type * DstTy,Type * SrcTy)115 bool TypeMapTy::areTypesIsomorphic(Type *DstTy, Type *SrcTy) {
116 // Two types with differing kinds are clearly not isomorphic.
117 if (DstTy->getTypeID() != SrcTy->getTypeID())
118 return false;
119
120 // If we have an entry in the MappedTypes table, then we have our answer.
121 Type *&Entry = MappedTypes[SrcTy];
122 if (Entry)
123 return Entry == DstTy;
124
125 // Two identical types are clearly isomorphic. Remember this
126 // non-speculatively.
127 if (DstTy == SrcTy) {
128 Entry = DstTy;
129 return true;
130 }
131
132 // Okay, we have two types with identical kinds that we haven't seen before.
133
134 // If this is an opaque struct type, special case it.
135 if (StructType *SSTy = dyn_cast<StructType>(SrcTy)) {
136 // Mapping an opaque type to any struct, just keep the dest struct.
137 if (SSTy->isOpaque()) {
138 Entry = DstTy;
139 SpeculativeTypes.push_back(SrcTy);
140 return true;
141 }
142
143 // Mapping a non-opaque source type to an opaque dest. If this is the first
144 // type that we're mapping onto this destination type then we succeed. Keep
145 // the dest, but fill it in later. If this is the second (different) type
146 // that we're trying to map onto the same opaque type then we fail.
147 if (cast<StructType>(DstTy)->isOpaque()) {
148 // We can only map one source type onto the opaque destination type.
149 if (!DstResolvedOpaqueTypes.insert(cast<StructType>(DstTy)).second)
150 return false;
151 SrcDefinitionsToResolve.push_back(SSTy);
152 SpeculativeTypes.push_back(SrcTy);
153 SpeculativeDstOpaqueTypes.push_back(cast<StructType>(DstTy));
154 Entry = DstTy;
155 return true;
156 }
157 }
158
159 // If the number of subtypes disagree between the two types, then we fail.
160 if (SrcTy->getNumContainedTypes() != DstTy->getNumContainedTypes())
161 return false;
162
163 // Fail if any of the extra properties (e.g. array size) of the type disagree.
164 if (isa<IntegerType>(DstTy))
165 return false; // bitwidth disagrees.
166 if (PointerType *PT = dyn_cast<PointerType>(DstTy)) {
167 if (PT->getAddressSpace() != cast<PointerType>(SrcTy)->getAddressSpace())
168 return false;
169 } else if (FunctionType *FT = dyn_cast<FunctionType>(DstTy)) {
170 if (FT->isVarArg() != cast<FunctionType>(SrcTy)->isVarArg())
171 return false;
172 } else if (StructType *DSTy = dyn_cast<StructType>(DstTy)) {
173 StructType *SSTy = cast<StructType>(SrcTy);
174 if (DSTy->isLiteral() != SSTy->isLiteral() ||
175 DSTy->isPacked() != SSTy->isPacked())
176 return false;
177 } else if (auto *DArrTy = dyn_cast<ArrayType>(DstTy)) {
178 if (DArrTy->getNumElements() != cast<ArrayType>(SrcTy)->getNumElements())
179 return false;
180 } else if (auto *DVecTy = dyn_cast<VectorType>(DstTy)) {
181 if (DVecTy->getElementCount() != cast<VectorType>(SrcTy)->getElementCount())
182 return false;
183 }
184
185 // Otherwise, we speculate that these two types will line up and recursively
186 // check the subelements.
187 Entry = DstTy;
188 SpeculativeTypes.push_back(SrcTy);
189
190 for (unsigned I = 0, E = SrcTy->getNumContainedTypes(); I != E; ++I)
191 if (!areTypesIsomorphic(DstTy->getContainedType(I),
192 SrcTy->getContainedType(I)))
193 return false;
194
195 // If everything seems to have lined up, then everything is great.
196 return true;
197 }
198
linkDefinedTypeBodies()199 void TypeMapTy::linkDefinedTypeBodies() {
200 SmallVector<Type *, 16> Elements;
201 for (StructType *SrcSTy : SrcDefinitionsToResolve) {
202 StructType *DstSTy = cast<StructType>(MappedTypes[SrcSTy]);
203 assert(DstSTy->isOpaque());
204
205 // Map the body of the source type over to a new body for the dest type.
206 Elements.resize(SrcSTy->getNumElements());
207 for (unsigned I = 0, E = Elements.size(); I != E; ++I)
208 Elements[I] = get(SrcSTy->getElementType(I));
209
210 DstSTy->setBody(Elements, SrcSTy->isPacked());
211 DstStructTypesSet.switchToNonOpaque(DstSTy);
212 }
213 SrcDefinitionsToResolve.clear();
214 DstResolvedOpaqueTypes.clear();
215 }
216
finishType(StructType * DTy,StructType * STy,ArrayRef<Type * > ETypes)217 void TypeMapTy::finishType(StructType *DTy, StructType *STy,
218 ArrayRef<Type *> ETypes) {
219 DTy->setBody(ETypes, STy->isPacked());
220
221 // Steal STy's name.
222 if (STy->hasName()) {
223 SmallString<16> TmpName = STy->getName();
224 STy->setName("");
225 DTy->setName(TmpName);
226 }
227
228 DstStructTypesSet.addNonOpaque(DTy);
229 }
230
get(Type * Ty)231 Type *TypeMapTy::get(Type *Ty) {
232 SmallPtrSet<StructType *, 8> Visited;
233 return get(Ty, Visited);
234 }
235
get(Type * Ty,SmallPtrSet<StructType *,8> & Visited)236 Type *TypeMapTy::get(Type *Ty, SmallPtrSet<StructType *, 8> &Visited) {
237 // If we already have an entry for this type, return it.
238 Type **Entry = &MappedTypes[Ty];
239 if (*Entry)
240 return *Entry;
241
242 // These are types that LLVM itself will unique.
243 bool IsUniqued = !isa<StructType>(Ty) || cast<StructType>(Ty)->isLiteral();
244
245 if (!IsUniqued) {
246 #ifndef NDEBUG
247 for (auto &Pair : MappedTypes) {
248 assert(!(Pair.first != Ty && Pair.second == Ty) &&
249 "mapping to a source type");
250 }
251 #endif
252
253 if (!Visited.insert(cast<StructType>(Ty)).second) {
254 StructType *DTy = StructType::create(Ty->getContext());
255 return *Entry = DTy;
256 }
257 }
258
259 // If this is not a recursive type, then just map all of the elements and
260 // then rebuild the type from inside out.
261 SmallVector<Type *, 4> ElementTypes;
262
263 // If there are no element types to map, then the type is itself. This is
264 // true for the anonymous {} struct, things like 'float', integers, etc.
265 if (Ty->getNumContainedTypes() == 0 && IsUniqued)
266 return *Entry = Ty;
267
268 // Remap all of the elements, keeping track of whether any of them change.
269 bool AnyChange = false;
270 ElementTypes.resize(Ty->getNumContainedTypes());
271 for (unsigned I = 0, E = Ty->getNumContainedTypes(); I != E; ++I) {
272 ElementTypes[I] = get(Ty->getContainedType(I), Visited);
273 AnyChange |= ElementTypes[I] != Ty->getContainedType(I);
274 }
275
276 // If we found our type while recursively processing stuff, just use it.
277 Entry = &MappedTypes[Ty];
278 if (*Entry) {
279 if (auto *DTy = dyn_cast<StructType>(*Entry)) {
280 if (DTy->isOpaque()) {
281 auto *STy = cast<StructType>(Ty);
282 finishType(DTy, STy, ElementTypes);
283 }
284 }
285 return *Entry;
286 }
287
288 // If all of the element types mapped directly over and the type is not
289 // a named struct, then the type is usable as-is.
290 if (!AnyChange && IsUniqued)
291 return *Entry = Ty;
292
293 // Otherwise, rebuild a modified type.
294 switch (Ty->getTypeID()) {
295 default:
296 llvm_unreachable("unknown derived type to remap");
297 case Type::ArrayTyID:
298 return *Entry = ArrayType::get(ElementTypes[0],
299 cast<ArrayType>(Ty)->getNumElements());
300 case Type::ScalableVectorTyID:
301 // FIXME: handle scalable vectors
302 case Type::FixedVectorTyID:
303 return *Entry = FixedVectorType::get(
304 ElementTypes[0], cast<FixedVectorType>(Ty)->getNumElements());
305 case Type::PointerTyID:
306 return *Entry = PointerType::get(ElementTypes[0],
307 cast<PointerType>(Ty)->getAddressSpace());
308 case Type::FunctionTyID:
309 return *Entry = FunctionType::get(ElementTypes[0],
310 makeArrayRef(ElementTypes).slice(1),
311 cast<FunctionType>(Ty)->isVarArg());
312 case Type::StructTyID: {
313 auto *STy = cast<StructType>(Ty);
314 bool IsPacked = STy->isPacked();
315 if (IsUniqued)
316 return *Entry = StructType::get(Ty->getContext(), ElementTypes, IsPacked);
317
318 // If the type is opaque, we can just use it directly.
319 if (STy->isOpaque()) {
320 DstStructTypesSet.addOpaque(STy);
321 return *Entry = Ty;
322 }
323
324 if (StructType *OldT =
325 DstStructTypesSet.findNonOpaque(ElementTypes, IsPacked)) {
326 STy->setName("");
327 return *Entry = OldT;
328 }
329
330 if (!AnyChange) {
331 DstStructTypesSet.addNonOpaque(STy);
332 return *Entry = Ty;
333 }
334
335 StructType *DTy = StructType::create(Ty->getContext());
336 finishType(DTy, STy, ElementTypes);
337 return *Entry = DTy;
338 }
339 }
340 }
341
LinkDiagnosticInfo(DiagnosticSeverity Severity,const Twine & Msg)342 LinkDiagnosticInfo::LinkDiagnosticInfo(DiagnosticSeverity Severity,
343 const Twine &Msg)
344 : DiagnosticInfo(DK_Linker, Severity), Msg(Msg) {}
print(DiagnosticPrinter & DP) const345 void LinkDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
346
347 //===----------------------------------------------------------------------===//
348 // IRLinker implementation.
349 //===----------------------------------------------------------------------===//
350
351 namespace {
352 class IRLinker;
353
354 /// Creates prototypes for functions that are lazily linked on the fly. This
355 /// speeds up linking for modules with many/ lazily linked functions of which
356 /// few get used.
357 class GlobalValueMaterializer final : public ValueMaterializer {
358 IRLinker &TheIRLinker;
359
360 public:
GlobalValueMaterializer(IRLinker & TheIRLinker)361 GlobalValueMaterializer(IRLinker &TheIRLinker) : TheIRLinker(TheIRLinker) {}
362 Value *materialize(Value *V) override;
363 };
364
365 class LocalValueMaterializer final : public ValueMaterializer {
366 IRLinker &TheIRLinker;
367
368 public:
LocalValueMaterializer(IRLinker & TheIRLinker)369 LocalValueMaterializer(IRLinker &TheIRLinker) : TheIRLinker(TheIRLinker) {}
370 Value *materialize(Value *V) override;
371 };
372
373 /// Type of the Metadata map in \a ValueToValueMapTy.
374 typedef DenseMap<const Metadata *, TrackingMDRef> MDMapT;
375
376 /// This is responsible for keeping track of the state used for moving data
377 /// from SrcM to DstM.
378 class IRLinker {
379 Module &DstM;
380 std::unique_ptr<Module> SrcM;
381
382 /// See IRMover::move().
383 std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor;
384
385 TypeMapTy TypeMap;
386 GlobalValueMaterializer GValMaterializer;
387 LocalValueMaterializer LValMaterializer;
388
389 /// A metadata map that's shared between IRLinker instances.
390 MDMapT &SharedMDs;
391
392 /// Mapping of values from what they used to be in Src, to what they are now
393 /// in DstM. ValueToValueMapTy is a ValueMap, which involves some overhead
394 /// due to the use of Value handles which the Linker doesn't actually need,
395 /// but this allows us to reuse the ValueMapper code.
396 ValueToValueMapTy ValueMap;
397 ValueToValueMapTy IndirectSymbolValueMap;
398
399 DenseSet<GlobalValue *> ValuesToLink;
400 std::vector<GlobalValue *> Worklist;
401 std::vector<std::pair<GlobalValue *, Value*>> RAUWWorklist;
402
maybeAdd(GlobalValue * GV)403 void maybeAdd(GlobalValue *GV) {
404 if (ValuesToLink.insert(GV).second)
405 Worklist.push_back(GV);
406 }
407
408 /// Whether we are importing globals for ThinLTO, as opposed to linking the
409 /// source module. If this flag is set, it means that we can rely on some
410 /// other object file to define any non-GlobalValue entities defined by the
411 /// source module. This currently causes us to not link retained types in
412 /// debug info metadata and module inline asm.
413 bool IsPerformingImport;
414
415 /// Set to true when all global value body linking is complete (including
416 /// lazy linking). Used to prevent metadata linking from creating new
417 /// references.
418 bool DoneLinkingBodies = false;
419
420 /// The Error encountered during materialization. We use an Optional here to
421 /// avoid needing to manage an unconsumed success value.
422 Optional<Error> FoundError;
setError(Error E)423 void setError(Error E) {
424 if (E)
425 FoundError = std::move(E);
426 }
427
428 /// Most of the errors produced by this module are inconvertible StringErrors.
429 /// This convenience function lets us return one of those more easily.
stringErr(const Twine & T)430 Error stringErr(const Twine &T) {
431 return make_error<StringError>(T, inconvertibleErrorCode());
432 }
433
434 /// Entry point for mapping values and alternate context for mapping aliases.
435 ValueMapper Mapper;
436 unsigned IndirectSymbolMCID;
437
438 /// Handles cloning of a global values from the source module into
439 /// the destination module, including setting the attributes and visibility.
440 GlobalValue *copyGlobalValueProto(const GlobalValue *SGV, bool ForDefinition);
441
emitWarning(const Twine & Message)442 void emitWarning(const Twine &Message) {
443 SrcM->getContext().diagnose(LinkDiagnosticInfo(DS_Warning, Message));
444 }
445
446 /// Given a global in the source module, return the global in the
447 /// destination module that is being linked to, if any.
getLinkedToGlobal(const GlobalValue * SrcGV)448 GlobalValue *getLinkedToGlobal(const GlobalValue *SrcGV) {
449 // If the source has no name it can't link. If it has local linkage,
450 // there is no name match-up going on.
451 if (!SrcGV->hasName() || SrcGV->hasLocalLinkage())
452 return nullptr;
453
454 // Otherwise see if we have a match in the destination module's symtab.
455 GlobalValue *DGV = DstM.getNamedValue(SrcGV->getName());
456 if (!DGV)
457 return nullptr;
458
459 // If we found a global with the same name in the dest module, but it has
460 // internal linkage, we are really not doing any linkage here.
461 if (DGV->hasLocalLinkage())
462 return nullptr;
463
464 // Otherwise, we do in fact link to the destination global.
465 return DGV;
466 }
467
468 void computeTypeMapping();
469
470 Expected<Constant *> linkAppendingVarProto(GlobalVariable *DstGV,
471 const GlobalVariable *SrcGV);
472
473 /// Given the GlobaValue \p SGV in the source module, and the matching
474 /// GlobalValue \p DGV (if any), return true if the linker will pull \p SGV
475 /// into the destination module.
476 ///
477 /// Note this code may call the client-provided \p AddLazyFor.
478 bool shouldLink(GlobalValue *DGV, GlobalValue &SGV);
479 Expected<Constant *> linkGlobalValueProto(GlobalValue *GV,
480 bool ForIndirectSymbol);
481
482 Error linkModuleFlagsMetadata();
483
484 void linkGlobalVariable(GlobalVariable &Dst, GlobalVariable &Src);
485 Error linkFunctionBody(Function &Dst, Function &Src);
486 void linkIndirectSymbolBody(GlobalIndirectSymbol &Dst,
487 GlobalIndirectSymbol &Src);
488 Error linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src);
489
490 /// Replace all types in the source AttributeList with the
491 /// corresponding destination type.
492 AttributeList mapAttributeTypes(LLVMContext &C, AttributeList Attrs);
493
494 /// Functions that take care of cloning a specific global value type
495 /// into the destination module.
496 GlobalVariable *copyGlobalVariableProto(const GlobalVariable *SGVar);
497 Function *copyFunctionProto(const Function *SF);
498 GlobalValue *copyGlobalIndirectSymbolProto(const GlobalIndirectSymbol *SGIS);
499
500 /// Perform "replace all uses with" operations. These work items need to be
501 /// performed as part of materialization, but we postpone them to happen after
502 /// materialization is done. The materializer called by ValueMapper is not
503 /// expected to delete constants, as ValueMapper is holding pointers to some
504 /// of them, but constant destruction may be indirectly triggered by RAUW.
505 /// Hence, the need to move this out of the materialization call chain.
506 void flushRAUWWorklist();
507
508 /// When importing for ThinLTO, prevent importing of types listed on
509 /// the DICompileUnit that we don't need a copy of in the importing
510 /// module.
511 void prepareCompileUnitsForImport();
512 void linkNamedMDNodes();
513
514 public:
IRLinker(Module & DstM,MDMapT & SharedMDs,IRMover::IdentifiedStructTypeSet & Set,std::unique_ptr<Module> SrcM,ArrayRef<GlobalValue * > ValuesToLink,std::function<void (GlobalValue &,IRMover::ValueAdder)> AddLazyFor,bool IsPerformingImport)515 IRLinker(Module &DstM, MDMapT &SharedMDs,
516 IRMover::IdentifiedStructTypeSet &Set, std::unique_ptr<Module> SrcM,
517 ArrayRef<GlobalValue *> ValuesToLink,
518 std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor,
519 bool IsPerformingImport)
520 : DstM(DstM), SrcM(std::move(SrcM)), AddLazyFor(std::move(AddLazyFor)),
521 TypeMap(Set), GValMaterializer(*this), LValMaterializer(*this),
522 SharedMDs(SharedMDs), IsPerformingImport(IsPerformingImport),
523 Mapper(ValueMap, RF_MoveDistinctMDs | RF_IgnoreMissingLocals, &TypeMap,
524 &GValMaterializer),
525 IndirectSymbolMCID(Mapper.registerAlternateMappingContext(
526 IndirectSymbolValueMap, &LValMaterializer)) {
527 ValueMap.getMDMap() = std::move(SharedMDs);
528 for (GlobalValue *GV : ValuesToLink)
529 maybeAdd(GV);
530 if (IsPerformingImport)
531 prepareCompileUnitsForImport();
532 }
~IRLinker()533 ~IRLinker() { SharedMDs = std::move(*ValueMap.getMDMap()); }
534
535 Error run();
536 Value *materialize(Value *V, bool ForIndirectSymbol);
537 };
538 }
539
540 /// The LLVM SymbolTable class autorenames globals that conflict in the symbol
541 /// table. This is good for all clients except for us. Go through the trouble
542 /// to force this back.
forceRenaming(GlobalValue * GV,StringRef Name)543 static void forceRenaming(GlobalValue *GV, StringRef Name) {
544 // If the global doesn't force its name or if it already has the right name,
545 // there is nothing for us to do.
546 if (GV->hasLocalLinkage() || GV->getName() == Name)
547 return;
548
549 Module *M = GV->getParent();
550
551 // If there is a conflict, rename the conflict.
552 if (GlobalValue *ConflictGV = M->getNamedValue(Name)) {
553 GV->takeName(ConflictGV);
554 ConflictGV->setName(Name); // This will cause ConflictGV to get renamed
555 assert(ConflictGV->getName() != Name && "forceRenaming didn't work");
556 } else {
557 GV->setName(Name); // Force the name back
558 }
559 }
560
materialize(Value * SGV)561 Value *GlobalValueMaterializer::materialize(Value *SGV) {
562 return TheIRLinker.materialize(SGV, false);
563 }
564
materialize(Value * SGV)565 Value *LocalValueMaterializer::materialize(Value *SGV) {
566 return TheIRLinker.materialize(SGV, true);
567 }
568
materialize(Value * V,bool ForIndirectSymbol)569 Value *IRLinker::materialize(Value *V, bool ForIndirectSymbol) {
570 auto *SGV = dyn_cast<GlobalValue>(V);
571 if (!SGV)
572 return nullptr;
573
574 // When linking a global from other modules than source & dest, skip
575 // materializing it because it would be mapped later when its containing
576 // module is linked. Linking it now would potentially pull in many types that
577 // may not be mapped properly.
578 if (SGV->getParent() != &DstM && SGV->getParent() != SrcM.get())
579 return nullptr;
580
581 Expected<Constant *> NewProto = linkGlobalValueProto(SGV, ForIndirectSymbol);
582 if (!NewProto) {
583 setError(NewProto.takeError());
584 return nullptr;
585 }
586 if (!*NewProto)
587 return nullptr;
588
589 GlobalValue *New = dyn_cast<GlobalValue>(*NewProto);
590 if (!New)
591 return *NewProto;
592
593 // If we already created the body, just return.
594 if (auto *F = dyn_cast<Function>(New)) {
595 if (!F->isDeclaration())
596 return New;
597 } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
598 if (V->hasInitializer() || V->hasAppendingLinkage())
599 return New;
600 } else {
601 auto *IS = cast<GlobalIndirectSymbol>(New);
602 if (IS->getIndirectSymbol())
603 return New;
604 }
605
606 // When linking a global for an indirect symbol, it will always be linked.
607 // However we need to check if it was not already scheduled to satisfy a
608 // reference from a regular global value initializer. We know if it has been
609 // schedule if the "New" GlobalValue that is mapped here for the indirect
610 // symbol is the same as the one already mapped. If there is an entry in the
611 // ValueMap but the value is different, it means that the value already had a
612 // definition in the destination module (linkonce for instance), but we need a
613 // new definition for the indirect symbol ("New" will be different.
614 if (ForIndirectSymbol && ValueMap.lookup(SGV) == New)
615 return New;
616
617 if (ForIndirectSymbol || shouldLink(New, *SGV))
618 setError(linkGlobalValueBody(*New, *SGV));
619
620 return New;
621 }
622
623 /// Loop through the global variables in the src module and merge them into the
624 /// dest module.
copyGlobalVariableProto(const GlobalVariable * SGVar)625 GlobalVariable *IRLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
626 // No linking to be performed or linking from the source: simply create an
627 // identical version of the symbol over in the dest module... the
628 // initializer will be filled in later by LinkGlobalInits.
629 GlobalVariable *NewDGV =
630 new GlobalVariable(DstM, TypeMap.get(SGVar->getValueType()),
631 SGVar->isConstant(), GlobalValue::ExternalLinkage,
632 /*init*/ nullptr, SGVar->getName(),
633 /*insertbefore*/ nullptr, SGVar->getThreadLocalMode(),
634 SGVar->getAddressSpace());
635 NewDGV->setAlignment(MaybeAlign(SGVar->getAlignment()));
636 NewDGV->copyAttributesFrom(SGVar);
637 return NewDGV;
638 }
639
mapAttributeTypes(LLVMContext & C,AttributeList Attrs)640 AttributeList IRLinker::mapAttributeTypes(LLVMContext &C, AttributeList Attrs) {
641 for (unsigned i = 0; i < Attrs.getNumAttrSets(); ++i) {
642 for (Attribute::AttrKind TypedAttr :
643 {Attribute::ByVal, Attribute::StructRet, Attribute::ByRef}) {
644 if (Attrs.hasAttribute(i, TypedAttr)) {
645 if (Type *Ty = Attrs.getAttribute(i, TypedAttr).getValueAsType()) {
646 Attrs = Attrs.replaceAttributeType(C, i, TypedAttr, TypeMap.get(Ty));
647 break;
648 }
649 }
650 }
651 }
652 return Attrs;
653 }
654
655 /// Link the function in the source module into the destination module if
656 /// needed, setting up mapping information.
copyFunctionProto(const Function * SF)657 Function *IRLinker::copyFunctionProto(const Function *SF) {
658 // If there is no linkage to be performed or we are linking from the source,
659 // bring SF over.
660 auto *F = Function::Create(TypeMap.get(SF->getFunctionType()),
661 GlobalValue::ExternalLinkage,
662 SF->getAddressSpace(), SF->getName(), &DstM);
663 F->copyAttributesFrom(SF);
664 F->setAttributes(mapAttributeTypes(F->getContext(), F->getAttributes()));
665 return F;
666 }
667
668 /// Set up prototypes for any indirect symbols that come over from the source
669 /// module.
670 GlobalValue *
copyGlobalIndirectSymbolProto(const GlobalIndirectSymbol * SGIS)671 IRLinker::copyGlobalIndirectSymbolProto(const GlobalIndirectSymbol *SGIS) {
672 // If there is no linkage to be performed or we're linking from the source,
673 // bring over SGA.
674 auto *Ty = TypeMap.get(SGIS->getValueType());
675 GlobalIndirectSymbol *GIS;
676 if (isa<GlobalAlias>(SGIS))
677 GIS = GlobalAlias::create(Ty, SGIS->getAddressSpace(),
678 GlobalValue::ExternalLinkage, SGIS->getName(),
679 &DstM);
680 else
681 GIS = GlobalIFunc::create(Ty, SGIS->getAddressSpace(),
682 GlobalValue::ExternalLinkage, SGIS->getName(),
683 nullptr, &DstM);
684 GIS->copyAttributesFrom(SGIS);
685 return GIS;
686 }
687
copyGlobalValueProto(const GlobalValue * SGV,bool ForDefinition)688 GlobalValue *IRLinker::copyGlobalValueProto(const GlobalValue *SGV,
689 bool ForDefinition) {
690 GlobalValue *NewGV;
691 if (auto *SGVar = dyn_cast<GlobalVariable>(SGV)) {
692 NewGV = copyGlobalVariableProto(SGVar);
693 } else if (auto *SF = dyn_cast<Function>(SGV)) {
694 NewGV = copyFunctionProto(SF);
695 } else {
696 if (ForDefinition)
697 NewGV = copyGlobalIndirectSymbolProto(cast<GlobalIndirectSymbol>(SGV));
698 else if (SGV->getValueType()->isFunctionTy())
699 NewGV =
700 Function::Create(cast<FunctionType>(TypeMap.get(SGV->getValueType())),
701 GlobalValue::ExternalLinkage, SGV->getAddressSpace(),
702 SGV->getName(), &DstM);
703 else
704 NewGV =
705 new GlobalVariable(DstM, TypeMap.get(SGV->getValueType()),
706 /*isConstant*/ false, GlobalValue::ExternalLinkage,
707 /*init*/ nullptr, SGV->getName(),
708 /*insertbefore*/ nullptr,
709 SGV->getThreadLocalMode(), SGV->getAddressSpace());
710 }
711
712 if (ForDefinition)
713 NewGV->setLinkage(SGV->getLinkage());
714 else if (SGV->hasExternalWeakLinkage())
715 NewGV->setLinkage(GlobalValue::ExternalWeakLinkage);
716
717 if (auto *NewGO = dyn_cast<GlobalObject>(NewGV)) {
718 // Metadata for global variables and function declarations is copied eagerly.
719 if (isa<GlobalVariable>(SGV) || SGV->isDeclaration())
720 NewGO->copyMetadata(cast<GlobalObject>(SGV), 0);
721 }
722
723 // Remove these copied constants in case this stays a declaration, since
724 // they point to the source module. If the def is linked the values will
725 // be mapped in during linkFunctionBody.
726 if (auto *NewF = dyn_cast<Function>(NewGV)) {
727 NewF->setPersonalityFn(nullptr);
728 NewF->setPrefixData(nullptr);
729 NewF->setPrologueData(nullptr);
730 }
731
732 return NewGV;
733 }
734
getTypeNamePrefix(StringRef Name)735 static StringRef getTypeNamePrefix(StringRef Name) {
736 size_t DotPos = Name.rfind('.');
737 return (DotPos == 0 || DotPos == StringRef::npos || Name.back() == '.' ||
738 !isdigit(static_cast<unsigned char>(Name[DotPos + 1])))
739 ? Name
740 : Name.substr(0, DotPos);
741 }
742
743 /// Loop over all of the linked values to compute type mappings. For example,
744 /// if we link "extern Foo *x" and "Foo *x = NULL", then we have two struct
745 /// types 'Foo' but one got renamed when the module was loaded into the same
746 /// LLVMContext.
computeTypeMapping()747 void IRLinker::computeTypeMapping() {
748 for (GlobalValue &SGV : SrcM->globals()) {
749 GlobalValue *DGV = getLinkedToGlobal(&SGV);
750 if (!DGV)
751 continue;
752
753 if (!DGV->hasAppendingLinkage() || !SGV.hasAppendingLinkage()) {
754 TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
755 continue;
756 }
757
758 // Unify the element type of appending arrays.
759 ArrayType *DAT = cast<ArrayType>(DGV->getValueType());
760 ArrayType *SAT = cast<ArrayType>(SGV.getValueType());
761 TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
762 }
763
764 for (GlobalValue &SGV : *SrcM)
765 if (GlobalValue *DGV = getLinkedToGlobal(&SGV)) {
766 if (DGV->getType() == SGV.getType()) {
767 // If the types of DGV and SGV are the same, it means that DGV is from
768 // the source module and got added to DstM from a shared metadata. We
769 // shouldn't map this type to itself in case the type's components get
770 // remapped to a new type from DstM (for instance, during the loop over
771 // SrcM->getIdentifiedStructTypes() below).
772 continue;
773 }
774
775 TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
776 }
777
778 for (GlobalValue &SGV : SrcM->aliases())
779 if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
780 TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
781
782 // Incorporate types by name, scanning all the types in the source module.
783 // At this point, the destination module may have a type "%foo = { i32 }" for
784 // example. When the source module got loaded into the same LLVMContext, if
785 // it had the same type, it would have been renamed to "%foo.42 = { i32 }".
786 std::vector<StructType *> Types = SrcM->getIdentifiedStructTypes();
787 for (StructType *ST : Types) {
788 if (!ST->hasName())
789 continue;
790
791 if (TypeMap.DstStructTypesSet.hasType(ST)) {
792 // This is actually a type from the destination module.
793 // getIdentifiedStructTypes() can have found it by walking debug info
794 // metadata nodes, some of which get linked by name when ODR Type Uniquing
795 // is enabled on the Context, from the source to the destination module.
796 continue;
797 }
798
799 auto STTypePrefix = getTypeNamePrefix(ST->getName());
800 if (STTypePrefix.size() == ST->getName().size())
801 continue;
802
803 // Check to see if the destination module has a struct with the prefix name.
804 StructType *DST = StructType::getTypeByName(ST->getContext(), STTypePrefix);
805 if (!DST)
806 continue;
807
808 // Don't use it if this actually came from the source module. They're in
809 // the same LLVMContext after all. Also don't use it unless the type is
810 // actually used in the destination module. This can happen in situations
811 // like this:
812 //
813 // Module A Module B
814 // -------- --------
815 // %Z = type { %A } %B = type { %C.1 }
816 // %A = type { %B.1, [7 x i8] } %C.1 = type { i8* }
817 // %B.1 = type { %C } %A.2 = type { %B.3, [5 x i8] }
818 // %C = type { i8* } %B.3 = type { %C.1 }
819 //
820 // When we link Module B with Module A, the '%B' in Module B is
821 // used. However, that would then use '%C.1'. But when we process '%C.1',
822 // we prefer to take the '%C' version. So we are then left with both
823 // '%C.1' and '%C' being used for the same types. This leads to some
824 // variables using one type and some using the other.
825 if (TypeMap.DstStructTypesSet.hasType(DST))
826 TypeMap.addTypeMapping(DST, ST);
827 }
828
829 // Now that we have discovered all of the type equivalences, get a body for
830 // any 'opaque' types in the dest module that are now resolved.
831 TypeMap.linkDefinedTypeBodies();
832 }
833
getArrayElements(const Constant * C,SmallVectorImpl<Constant * > & Dest)834 static void getArrayElements(const Constant *C,
835 SmallVectorImpl<Constant *> &Dest) {
836 unsigned NumElements = cast<ArrayType>(C->getType())->getNumElements();
837
838 for (unsigned i = 0; i != NumElements; ++i)
839 Dest.push_back(C->getAggregateElement(i));
840 }
841
842 /// If there were any appending global variables, link them together now.
843 Expected<Constant *>
linkAppendingVarProto(GlobalVariable * DstGV,const GlobalVariable * SrcGV)844 IRLinker::linkAppendingVarProto(GlobalVariable *DstGV,
845 const GlobalVariable *SrcGV) {
846 // Check that both variables have compatible properties.
847 if (DstGV && !DstGV->isDeclaration() && !SrcGV->isDeclaration()) {
848 if (!SrcGV->hasAppendingLinkage() || !DstGV->hasAppendingLinkage())
849 return stringErr(
850 "Linking globals named '" + SrcGV->getName() +
851 "': can only link appending global with another appending "
852 "global!");
853
854 if (DstGV->isConstant() != SrcGV->isConstant())
855 return stringErr("Appending variables linked with different const'ness!");
856
857 if (DstGV->getAlignment() != SrcGV->getAlignment())
858 return stringErr(
859 "Appending variables with different alignment need to be linked!");
860
861 if (DstGV->getVisibility() != SrcGV->getVisibility())
862 return stringErr(
863 "Appending variables with different visibility need to be linked!");
864
865 if (DstGV->hasGlobalUnnamedAddr() != SrcGV->hasGlobalUnnamedAddr())
866 return stringErr(
867 "Appending variables with different unnamed_addr need to be linked!");
868
869 if (DstGV->getSection() != SrcGV->getSection())
870 return stringErr(
871 "Appending variables with different section name need to be linked!");
872 }
873
874 // Do not need to do anything if source is a declaration.
875 if (SrcGV->isDeclaration())
876 return DstGV;
877
878 Type *EltTy = cast<ArrayType>(TypeMap.get(SrcGV->getValueType()))
879 ->getElementType();
880
881 // FIXME: This upgrade is done during linking to support the C API. Once the
882 // old form is deprecated, we should move this upgrade to
883 // llvm::UpgradeGlobalVariable() and simplify the logic here and in
884 // Mapper::mapAppendingVariable() in ValueMapper.cpp.
885 StringRef Name = SrcGV->getName();
886 bool IsNewStructor = false;
887 bool IsOldStructor = false;
888 if (Name == "llvm.global_ctors" || Name == "llvm.global_dtors") {
889 if (cast<StructType>(EltTy)->getNumElements() == 3)
890 IsNewStructor = true;
891 else
892 IsOldStructor = true;
893 }
894
895 PointerType *VoidPtrTy = Type::getInt8Ty(SrcGV->getContext())->getPointerTo();
896 if (IsOldStructor) {
897 auto &ST = *cast<StructType>(EltTy);
898 Type *Tys[3] = {ST.getElementType(0), ST.getElementType(1), VoidPtrTy};
899 EltTy = StructType::get(SrcGV->getContext(), Tys, false);
900 }
901
902 uint64_t DstNumElements = 0;
903 if (DstGV && !DstGV->isDeclaration()) {
904 ArrayType *DstTy = cast<ArrayType>(DstGV->getValueType());
905 DstNumElements = DstTy->getNumElements();
906
907 // Check to see that they two arrays agree on type.
908 if (EltTy != DstTy->getElementType())
909 return stringErr("Appending variables with different element types!");
910 }
911
912 SmallVector<Constant *, 16> SrcElements;
913 getArrayElements(SrcGV->getInitializer(), SrcElements);
914
915 if (IsNewStructor) {
916 erase_if(SrcElements, [this](Constant *E) {
917 auto *Key =
918 dyn_cast<GlobalValue>(E->getAggregateElement(2)->stripPointerCasts());
919 if (!Key)
920 return false;
921 GlobalValue *DGV = getLinkedToGlobal(Key);
922 return !shouldLink(DGV, *Key);
923 });
924 }
925 uint64_t NewSize = DstNumElements + SrcElements.size();
926 ArrayType *NewType = ArrayType::get(EltTy, NewSize);
927
928 // Create the new global variable.
929 GlobalVariable *NG = new GlobalVariable(
930 DstM, NewType, SrcGV->isConstant(), SrcGV->getLinkage(),
931 /*init*/ nullptr, /*name*/ "", DstGV, SrcGV->getThreadLocalMode(),
932 SrcGV->getAddressSpace());
933
934 NG->copyAttributesFrom(SrcGV);
935 forceRenaming(NG, SrcGV->getName());
936
937 Constant *Ret = ConstantExpr::getBitCast(NG, TypeMap.get(SrcGV->getType()));
938
939 Mapper.scheduleMapAppendingVariable(
940 *NG,
941 (DstGV && !DstGV->isDeclaration()) ? DstGV->getInitializer() : nullptr,
942 IsOldStructor, SrcElements);
943
944 // Replace any uses of the two global variables with uses of the new
945 // global.
946 if (DstGV) {
947 RAUWWorklist.push_back(
948 std::make_pair(DstGV, ConstantExpr::getBitCast(NG, DstGV->getType())));
949 }
950
951 return Ret;
952 }
953
shouldLink(GlobalValue * DGV,GlobalValue & SGV)954 bool IRLinker::shouldLink(GlobalValue *DGV, GlobalValue &SGV) {
955 if (ValuesToLink.count(&SGV) || SGV.hasLocalLinkage())
956 return true;
957
958 if (DGV && !DGV->isDeclarationForLinker())
959 return false;
960
961 if (SGV.isDeclaration() || DoneLinkingBodies)
962 return false;
963
964 // Callback to the client to give a chance to lazily add the Global to the
965 // list of value to link.
966 bool LazilyAdded = false;
967 AddLazyFor(SGV, [this, &LazilyAdded](GlobalValue &GV) {
968 maybeAdd(&GV);
969 LazilyAdded = true;
970 });
971 return LazilyAdded;
972 }
973
linkGlobalValueProto(GlobalValue * SGV,bool ForIndirectSymbol)974 Expected<Constant *> IRLinker::linkGlobalValueProto(GlobalValue *SGV,
975 bool ForIndirectSymbol) {
976 GlobalValue *DGV = getLinkedToGlobal(SGV);
977
978 bool ShouldLink = shouldLink(DGV, *SGV);
979
980 // just missing from map
981 if (ShouldLink) {
982 auto I = ValueMap.find(SGV);
983 if (I != ValueMap.end())
984 return cast<Constant>(I->second);
985
986 I = IndirectSymbolValueMap.find(SGV);
987 if (I != IndirectSymbolValueMap.end())
988 return cast<Constant>(I->second);
989 }
990
991 if (!ShouldLink && ForIndirectSymbol)
992 DGV = nullptr;
993
994 // Handle the ultra special appending linkage case first.
995 if (SGV->hasAppendingLinkage() || (DGV && DGV->hasAppendingLinkage()))
996 return linkAppendingVarProto(cast_or_null<GlobalVariable>(DGV),
997 cast<GlobalVariable>(SGV));
998
999 GlobalValue *NewGV;
1000 if (DGV && !ShouldLink) {
1001 NewGV = DGV;
1002 } else {
1003 // If we are done linking global value bodies (i.e. we are performing
1004 // metadata linking), don't link in the global value due to this
1005 // reference, simply map it to null.
1006 if (DoneLinkingBodies)
1007 return nullptr;
1008
1009 NewGV = copyGlobalValueProto(SGV, ShouldLink || ForIndirectSymbol);
1010 if (ShouldLink || !ForIndirectSymbol)
1011 forceRenaming(NewGV, SGV->getName());
1012 }
1013
1014 // Overloaded intrinsics have overloaded types names as part of their
1015 // names. If we renamed overloaded types we should rename the intrinsic
1016 // as well.
1017 if (Function *F = dyn_cast<Function>(NewGV))
1018 if (auto Remangled = Intrinsic::remangleIntrinsicFunction(F))
1019 NewGV = Remangled.getValue();
1020
1021 if (ShouldLink || ForIndirectSymbol) {
1022 if (const Comdat *SC = SGV->getComdat()) {
1023 if (auto *GO = dyn_cast<GlobalObject>(NewGV)) {
1024 Comdat *DC = DstM.getOrInsertComdat(SC->getName());
1025 DC->setSelectionKind(SC->getSelectionKind());
1026 GO->setComdat(DC);
1027 }
1028 }
1029 }
1030
1031 if (!ShouldLink && ForIndirectSymbol)
1032 NewGV->setLinkage(GlobalValue::InternalLinkage);
1033
1034 Constant *C = NewGV;
1035 // Only create a bitcast if necessary. In particular, with
1036 // DebugTypeODRUniquing we may reach metadata in the destination module
1037 // containing a GV from the source module, in which case SGV will be
1038 // the same as DGV and NewGV, and TypeMap.get() will assert since it
1039 // assumes it is being invoked on a type in the source module.
1040 if (DGV && NewGV != SGV) {
1041 C = ConstantExpr::getPointerBitCastOrAddrSpaceCast(
1042 NewGV, TypeMap.get(SGV->getType()));
1043 }
1044
1045 if (DGV && NewGV != DGV) {
1046 // Schedule "replace all uses with" to happen after materializing is
1047 // done. It is not safe to do it now, since ValueMapper may be holding
1048 // pointers to constants that will get deleted if RAUW runs.
1049 RAUWWorklist.push_back(std::make_pair(
1050 DGV,
1051 ConstantExpr::getPointerBitCastOrAddrSpaceCast(NewGV, DGV->getType())));
1052 }
1053
1054 return C;
1055 }
1056
1057 /// Update the initializers in the Dest module now that all globals that may be
1058 /// referenced are in Dest.
linkGlobalVariable(GlobalVariable & Dst,GlobalVariable & Src)1059 void IRLinker::linkGlobalVariable(GlobalVariable &Dst, GlobalVariable &Src) {
1060 // Figure out what the initializer looks like in the dest module.
1061 Mapper.scheduleMapGlobalInitializer(Dst, *Src.getInitializer());
1062 }
1063
1064 /// Copy the source function over into the dest function and fix up references
1065 /// to values. At this point we know that Dest is an external function, and
1066 /// that Src is not.
linkFunctionBody(Function & Dst,Function & Src)1067 Error IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
1068 assert(Dst.isDeclaration() && !Src.isDeclaration());
1069
1070 // Materialize if needed.
1071 if (Error Err = Src.materialize())
1072 return Err;
1073
1074 // Link in the operands without remapping.
1075 if (Src.hasPrefixData())
1076 Dst.setPrefixData(Src.getPrefixData());
1077 if (Src.hasPrologueData())
1078 Dst.setPrologueData(Src.getPrologueData());
1079 if (Src.hasPersonalityFn())
1080 Dst.setPersonalityFn(Src.getPersonalityFn());
1081
1082 // Copy over the metadata attachments without remapping.
1083 Dst.copyMetadata(&Src, 0);
1084
1085 // Steal arguments and splice the body of Src into Dst.
1086 Dst.stealArgumentListFrom(Src);
1087 Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
1088
1089 // Everything has been moved over. Remap it.
1090 Mapper.scheduleRemapFunction(Dst);
1091 return Error::success();
1092 }
1093
linkIndirectSymbolBody(GlobalIndirectSymbol & Dst,GlobalIndirectSymbol & Src)1094 void IRLinker::linkIndirectSymbolBody(GlobalIndirectSymbol &Dst,
1095 GlobalIndirectSymbol &Src) {
1096 Mapper.scheduleMapGlobalIndirectSymbol(Dst, *Src.getIndirectSymbol(),
1097 IndirectSymbolMCID);
1098 }
1099
linkGlobalValueBody(GlobalValue & Dst,GlobalValue & Src)1100 Error IRLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
1101 if (auto *F = dyn_cast<Function>(&Src))
1102 return linkFunctionBody(cast<Function>(Dst), *F);
1103 if (auto *GVar = dyn_cast<GlobalVariable>(&Src)) {
1104 linkGlobalVariable(cast<GlobalVariable>(Dst), *GVar);
1105 return Error::success();
1106 }
1107 linkIndirectSymbolBody(cast<GlobalIndirectSymbol>(Dst), cast<GlobalIndirectSymbol>(Src));
1108 return Error::success();
1109 }
1110
flushRAUWWorklist()1111 void IRLinker::flushRAUWWorklist() {
1112 for (const auto &Elem : RAUWWorklist) {
1113 GlobalValue *Old;
1114 Value *New;
1115 std::tie(Old, New) = Elem;
1116
1117 Old->replaceAllUsesWith(New);
1118 Old->eraseFromParent();
1119 }
1120 RAUWWorklist.clear();
1121 }
1122
prepareCompileUnitsForImport()1123 void IRLinker::prepareCompileUnitsForImport() {
1124 NamedMDNode *SrcCompileUnits = SrcM->getNamedMetadata("llvm.dbg.cu");
1125 if (!SrcCompileUnits)
1126 return;
1127 // When importing for ThinLTO, prevent importing of types listed on
1128 // the DICompileUnit that we don't need a copy of in the importing
1129 // module. They will be emitted by the originating module.
1130 for (unsigned I = 0, E = SrcCompileUnits->getNumOperands(); I != E; ++I) {
1131 auto *CU = cast<DICompileUnit>(SrcCompileUnits->getOperand(I));
1132 assert(CU && "Expected valid compile unit");
1133 // Enums, macros, and retained types don't need to be listed on the
1134 // imported DICompileUnit. This means they will only be imported
1135 // if reached from the mapped IR.
1136 CU->replaceEnumTypes(nullptr);
1137 CU->replaceMacros(nullptr);
1138 CU->replaceRetainedTypes(nullptr);
1139
1140 // The original definition (or at least its debug info - if the variable is
1141 // internalized and optimized away) will remain in the source module, so
1142 // there's no need to import them.
1143 // If LLVM ever does more advanced optimizations on global variables
1144 // (removing/localizing write operations, for instance) that can track
1145 // through debug info, this decision may need to be revisited - but do so
1146 // with care when it comes to debug info size. Emitting small CUs containing
1147 // only a few imported entities into every destination module may be very
1148 // size inefficient.
1149 CU->replaceGlobalVariables(nullptr);
1150
1151 // Imported entities only need to be mapped in if they have local
1152 // scope, as those might correspond to an imported entity inside a
1153 // function being imported (any locally scoped imported entities that
1154 // don't end up referenced by an imported function will not be emitted
1155 // into the object). Imported entities not in a local scope
1156 // (e.g. on the namespace) only need to be emitted by the originating
1157 // module. Create a list of the locally scoped imported entities, and
1158 // replace the source CUs imported entity list with the new list, so
1159 // only those are mapped in.
1160 // FIXME: Locally-scoped imported entities could be moved to the
1161 // functions they are local to instead of listing them on the CU, and
1162 // we would naturally only link in those needed by function importing.
1163 SmallVector<TrackingMDNodeRef, 4> AllImportedModules;
1164 bool ReplaceImportedEntities = false;
1165 for (auto *IE : CU->getImportedEntities()) {
1166 DIScope *Scope = IE->getScope();
1167 assert(Scope && "Invalid Scope encoding!");
1168 if (isa<DILocalScope>(Scope))
1169 AllImportedModules.emplace_back(IE);
1170 else
1171 ReplaceImportedEntities = true;
1172 }
1173 if (ReplaceImportedEntities) {
1174 if (!AllImportedModules.empty())
1175 CU->replaceImportedEntities(MDTuple::get(
1176 CU->getContext(),
1177 SmallVector<Metadata *, 16>(AllImportedModules.begin(),
1178 AllImportedModules.end())));
1179 else
1180 // If there were no local scope imported entities, we can map
1181 // the whole list to nullptr.
1182 CU->replaceImportedEntities(nullptr);
1183 }
1184 }
1185 }
1186
1187 /// Insert all of the named MDNodes in Src into the Dest module.
linkNamedMDNodes()1188 void IRLinker::linkNamedMDNodes() {
1189 const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
1190 for (const NamedMDNode &NMD : SrcM->named_metadata()) {
1191 // Don't link module flags here. Do them separately.
1192 if (&NMD == SrcModFlags)
1193 continue;
1194 NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
1195 // Add Src elements into Dest node.
1196 for (const MDNode *Op : NMD.operands())
1197 DestNMD->addOperand(Mapper.mapMDNode(*Op));
1198 }
1199 }
1200
1201 /// Merge the linker flags in Src into the Dest module.
linkModuleFlagsMetadata()1202 Error IRLinker::linkModuleFlagsMetadata() {
1203 // If the source module has no module flags, we are done.
1204 const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
1205 if (!SrcModFlags)
1206 return Error::success();
1207
1208 // If the destination module doesn't have module flags yet, then just copy
1209 // over the source module's flags.
1210 NamedMDNode *DstModFlags = DstM.getOrInsertModuleFlagsMetadata();
1211 if (DstModFlags->getNumOperands() == 0) {
1212 for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
1213 DstModFlags->addOperand(SrcModFlags->getOperand(I));
1214
1215 return Error::success();
1216 }
1217
1218 // First build a map of the existing module flags and requirements.
1219 DenseMap<MDString *, std::pair<MDNode *, unsigned>> Flags;
1220 SmallSetVector<MDNode *, 16> Requirements;
1221 for (unsigned I = 0, E = DstModFlags->getNumOperands(); I != E; ++I) {
1222 MDNode *Op = DstModFlags->getOperand(I);
1223 ConstantInt *Behavior = mdconst::extract<ConstantInt>(Op->getOperand(0));
1224 MDString *ID = cast<MDString>(Op->getOperand(1));
1225
1226 if (Behavior->getZExtValue() == Module::Require) {
1227 Requirements.insert(cast<MDNode>(Op->getOperand(2)));
1228 } else {
1229 Flags[ID] = std::make_pair(Op, I);
1230 }
1231 }
1232
1233 // Merge in the flags from the source module, and also collect its set of
1234 // requirements.
1235 for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I) {
1236 MDNode *SrcOp = SrcModFlags->getOperand(I);
1237 ConstantInt *SrcBehavior =
1238 mdconst::extract<ConstantInt>(SrcOp->getOperand(0));
1239 MDString *ID = cast<MDString>(SrcOp->getOperand(1));
1240 MDNode *DstOp;
1241 unsigned DstIndex;
1242 std::tie(DstOp, DstIndex) = Flags.lookup(ID);
1243 unsigned SrcBehaviorValue = SrcBehavior->getZExtValue();
1244
1245 // If this is a requirement, add it and continue.
1246 if (SrcBehaviorValue == Module::Require) {
1247 // If the destination module does not already have this requirement, add
1248 // it.
1249 if (Requirements.insert(cast<MDNode>(SrcOp->getOperand(2)))) {
1250 DstModFlags->addOperand(SrcOp);
1251 }
1252 continue;
1253 }
1254
1255 // If there is no existing flag with this ID, just add it.
1256 if (!DstOp) {
1257 Flags[ID] = std::make_pair(SrcOp, DstModFlags->getNumOperands());
1258 DstModFlags->addOperand(SrcOp);
1259 continue;
1260 }
1261
1262 // Otherwise, perform a merge.
1263 ConstantInt *DstBehavior =
1264 mdconst::extract<ConstantInt>(DstOp->getOperand(0));
1265 unsigned DstBehaviorValue = DstBehavior->getZExtValue();
1266
1267 auto overrideDstValue = [&]() {
1268 DstModFlags->setOperand(DstIndex, SrcOp);
1269 Flags[ID].first = SrcOp;
1270 };
1271
1272 // If either flag has override behavior, handle it first.
1273 if (DstBehaviorValue == Module::Override) {
1274 // Diagnose inconsistent flags which both have override behavior.
1275 if (SrcBehaviorValue == Module::Override &&
1276 SrcOp->getOperand(2) != DstOp->getOperand(2))
1277 return stringErr("linking module flags '" + ID->getString() +
1278 "': IDs have conflicting override values in '" +
1279 SrcM->getModuleIdentifier() + "' and '" +
1280 DstM.getModuleIdentifier() + "'");
1281 continue;
1282 } else if (SrcBehaviorValue == Module::Override) {
1283 // Update the destination flag to that of the source.
1284 overrideDstValue();
1285 continue;
1286 }
1287
1288 // Diagnose inconsistent merge behavior types.
1289 if (SrcBehaviorValue != DstBehaviorValue) {
1290 bool MaxAndWarn = (SrcBehaviorValue == Module::Max &&
1291 DstBehaviorValue == Module::Warning) ||
1292 (DstBehaviorValue == Module::Max &&
1293 SrcBehaviorValue == Module::Warning);
1294 if (!MaxAndWarn)
1295 return stringErr("linking module flags '" + ID->getString() +
1296 "': IDs have conflicting behaviors in '" +
1297 SrcM->getModuleIdentifier() + "' and '" +
1298 DstM.getModuleIdentifier() + "'");
1299 }
1300
1301 auto replaceDstValue = [&](MDNode *New) {
1302 Metadata *FlagOps[] = {DstOp->getOperand(0), ID, New};
1303 MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
1304 DstModFlags->setOperand(DstIndex, Flag);
1305 Flags[ID].first = Flag;
1306 };
1307
1308 // Emit a warning if the values differ and either source or destination
1309 // request Warning behavior.
1310 if ((DstBehaviorValue == Module::Warning ||
1311 SrcBehaviorValue == Module::Warning) &&
1312 SrcOp->getOperand(2) != DstOp->getOperand(2)) {
1313 std::string Str;
1314 raw_string_ostream(Str)
1315 << "linking module flags '" << ID->getString()
1316 << "': IDs have conflicting values ('" << *SrcOp->getOperand(2)
1317 << "' from " << SrcM->getModuleIdentifier() << " with '"
1318 << *DstOp->getOperand(2) << "' from " << DstM.getModuleIdentifier()
1319 << ')';
1320 emitWarning(Str);
1321 }
1322
1323 // Choose the maximum if either source or destination request Max behavior.
1324 if (DstBehaviorValue == Module::Max || SrcBehaviorValue == Module::Max) {
1325 ConstantInt *DstValue =
1326 mdconst::extract<ConstantInt>(DstOp->getOperand(2));
1327 ConstantInt *SrcValue =
1328 mdconst::extract<ConstantInt>(SrcOp->getOperand(2));
1329
1330 // The resulting flag should have a Max behavior, and contain the maximum
1331 // value from between the source and destination values.
1332 Metadata *FlagOps[] = {
1333 (DstBehaviorValue != Module::Max ? SrcOp : DstOp)->getOperand(0), ID,
1334 (SrcValue->getZExtValue() > DstValue->getZExtValue() ? SrcOp : DstOp)
1335 ->getOperand(2)};
1336 MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
1337 DstModFlags->setOperand(DstIndex, Flag);
1338 Flags[ID].first = Flag;
1339 continue;
1340 }
1341
1342 // Perform the merge for standard behavior types.
1343 switch (SrcBehaviorValue) {
1344 case Module::Require:
1345 case Module::Override:
1346 llvm_unreachable("not possible");
1347 case Module::Error: {
1348 // Emit an error if the values differ.
1349 if (SrcOp->getOperand(2) != DstOp->getOperand(2))
1350 return stringErr("linking module flags '" + ID->getString() +
1351 "': IDs have conflicting values in '" +
1352 SrcM->getModuleIdentifier() + "' and '" +
1353 DstM.getModuleIdentifier() + "'");
1354 continue;
1355 }
1356 case Module::Warning: {
1357 break;
1358 }
1359 case Module::Max: {
1360 break;
1361 }
1362 case Module::Append: {
1363 MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
1364 MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
1365 SmallVector<Metadata *, 8> MDs;
1366 MDs.reserve(DstValue->getNumOperands() + SrcValue->getNumOperands());
1367 MDs.append(DstValue->op_begin(), DstValue->op_end());
1368 MDs.append(SrcValue->op_begin(), SrcValue->op_end());
1369
1370 replaceDstValue(MDNode::get(DstM.getContext(), MDs));
1371 break;
1372 }
1373 case Module::AppendUnique: {
1374 SmallSetVector<Metadata *, 16> Elts;
1375 MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
1376 MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
1377 Elts.insert(DstValue->op_begin(), DstValue->op_end());
1378 Elts.insert(SrcValue->op_begin(), SrcValue->op_end());
1379
1380 replaceDstValue(MDNode::get(DstM.getContext(),
1381 makeArrayRef(Elts.begin(), Elts.end())));
1382 break;
1383 }
1384 }
1385
1386 }
1387
1388 // Check all of the requirements.
1389 for (unsigned I = 0, E = Requirements.size(); I != E; ++I) {
1390 MDNode *Requirement = Requirements[I];
1391 MDString *Flag = cast<MDString>(Requirement->getOperand(0));
1392 Metadata *ReqValue = Requirement->getOperand(1);
1393
1394 MDNode *Op = Flags[Flag].first;
1395 if (!Op || Op->getOperand(2) != ReqValue)
1396 return stringErr("linking module flags '" + Flag->getString() +
1397 "': does not have the required value");
1398 }
1399 return Error::success();
1400 }
1401
1402 /// Return InlineAsm adjusted with target-specific directives if required.
1403 /// For ARM and Thumb, we have to add directives to select the appropriate ISA
1404 /// to support mixing module-level inline assembly from ARM and Thumb modules.
adjustInlineAsm(const std::string & InlineAsm,const Triple & Triple)1405 static std::string adjustInlineAsm(const std::string &InlineAsm,
1406 const Triple &Triple) {
1407 if (Triple.getArch() == Triple::thumb || Triple.getArch() == Triple::thumbeb)
1408 return ".text\n.balign 2\n.thumb\n" + InlineAsm;
1409 if (Triple.getArch() == Triple::arm || Triple.getArch() == Triple::armeb)
1410 return ".text\n.balign 4\n.arm\n" + InlineAsm;
1411 return InlineAsm;
1412 }
1413
run()1414 Error IRLinker::run() {
1415 // Ensure metadata materialized before value mapping.
1416 if (SrcM->getMaterializer())
1417 if (Error Err = SrcM->getMaterializer()->materializeMetadata())
1418 return Err;
1419
1420 // Inherit the target data from the source module if the destination module
1421 // doesn't have one already.
1422 if (DstM.getDataLayout().isDefault())
1423 DstM.setDataLayout(SrcM->getDataLayout());
1424
1425 if (SrcM->getDataLayout() != DstM.getDataLayout()) {
1426 emitWarning("Linking two modules of different data layouts: '" +
1427 SrcM->getModuleIdentifier() + "' is '" +
1428 SrcM->getDataLayoutStr() + "' whereas '" +
1429 DstM.getModuleIdentifier() + "' is '" +
1430 DstM.getDataLayoutStr() + "'\n");
1431 }
1432
1433 // Copy the target triple from the source to dest if the dest's is empty.
1434 if (DstM.getTargetTriple().empty() && !SrcM->getTargetTriple().empty())
1435 DstM.setTargetTriple(SrcM->getTargetTriple());
1436
1437 Triple SrcTriple(SrcM->getTargetTriple()), DstTriple(DstM.getTargetTriple());
1438
1439 if (!SrcM->getTargetTriple().empty()&&
1440 !SrcTriple.isCompatibleWith(DstTriple))
1441 emitWarning("Linking two modules of different target triples: '" +
1442 SrcM->getModuleIdentifier() + "' is '" +
1443 SrcM->getTargetTriple() + "' whereas '" +
1444 DstM.getModuleIdentifier() + "' is '" + DstM.getTargetTriple() +
1445 "'\n");
1446
1447 DstM.setTargetTriple(SrcTriple.merge(DstTriple));
1448
1449 // Loop over all of the linked values to compute type mappings.
1450 computeTypeMapping();
1451
1452 std::reverse(Worklist.begin(), Worklist.end());
1453 while (!Worklist.empty()) {
1454 GlobalValue *GV = Worklist.back();
1455 Worklist.pop_back();
1456
1457 // Already mapped.
1458 if (ValueMap.find(GV) != ValueMap.end() ||
1459 IndirectSymbolValueMap.find(GV) != IndirectSymbolValueMap.end())
1460 continue;
1461
1462 assert(!GV->isDeclaration());
1463 Mapper.mapValue(*GV);
1464 if (FoundError)
1465 return std::move(*FoundError);
1466 flushRAUWWorklist();
1467 }
1468
1469 // Note that we are done linking global value bodies. This prevents
1470 // metadata linking from creating new references.
1471 DoneLinkingBodies = true;
1472 Mapper.addFlags(RF_NullMapMissingGlobalValues);
1473
1474 // Remap all of the named MDNodes in Src into the DstM module. We do this
1475 // after linking GlobalValues so that MDNodes that reference GlobalValues
1476 // are properly remapped.
1477 linkNamedMDNodes();
1478
1479 if (!IsPerformingImport && !SrcM->getModuleInlineAsm().empty()) {
1480 // Append the module inline asm string.
1481 DstM.appendModuleInlineAsm(adjustInlineAsm(SrcM->getModuleInlineAsm(),
1482 SrcTriple));
1483 } else if (IsPerformingImport) {
1484 // Import any symver directives for symbols in DstM.
1485 ModuleSymbolTable::CollectAsmSymvers(*SrcM,
1486 [&](StringRef Name, StringRef Alias) {
1487 if (DstM.getNamedValue(Name)) {
1488 SmallString<256> S(".symver ");
1489 S += Name;
1490 S += ", ";
1491 S += Alias;
1492 DstM.appendModuleInlineAsm(S);
1493 }
1494 });
1495 }
1496
1497 // Merge the module flags into the DstM module.
1498 return linkModuleFlagsMetadata();
1499 }
1500
KeyTy(ArrayRef<Type * > E,bool P)1501 IRMover::StructTypeKeyInfo::KeyTy::KeyTy(ArrayRef<Type *> E, bool P)
1502 : ETypes(E), IsPacked(P) {}
1503
KeyTy(const StructType * ST)1504 IRMover::StructTypeKeyInfo::KeyTy::KeyTy(const StructType *ST)
1505 : ETypes(ST->elements()), IsPacked(ST->isPacked()) {}
1506
operator ==(const KeyTy & That) const1507 bool IRMover::StructTypeKeyInfo::KeyTy::operator==(const KeyTy &That) const {
1508 return IsPacked == That.IsPacked && ETypes == That.ETypes;
1509 }
1510
operator !=(const KeyTy & That) const1511 bool IRMover::StructTypeKeyInfo::KeyTy::operator!=(const KeyTy &That) const {
1512 return !this->operator==(That);
1513 }
1514
getEmptyKey()1515 StructType *IRMover::StructTypeKeyInfo::getEmptyKey() {
1516 return DenseMapInfo<StructType *>::getEmptyKey();
1517 }
1518
getTombstoneKey()1519 StructType *IRMover::StructTypeKeyInfo::getTombstoneKey() {
1520 return DenseMapInfo<StructType *>::getTombstoneKey();
1521 }
1522
getHashValue(const KeyTy & Key)1523 unsigned IRMover::StructTypeKeyInfo::getHashValue(const KeyTy &Key) {
1524 return hash_combine(hash_combine_range(Key.ETypes.begin(), Key.ETypes.end()),
1525 Key.IsPacked);
1526 }
1527
getHashValue(const StructType * ST)1528 unsigned IRMover::StructTypeKeyInfo::getHashValue(const StructType *ST) {
1529 return getHashValue(KeyTy(ST));
1530 }
1531
isEqual(const KeyTy & LHS,const StructType * RHS)1532 bool IRMover::StructTypeKeyInfo::isEqual(const KeyTy &LHS,
1533 const StructType *RHS) {
1534 if (RHS == getEmptyKey() || RHS == getTombstoneKey())
1535 return false;
1536 return LHS == KeyTy(RHS);
1537 }
1538
isEqual(const StructType * LHS,const StructType * RHS)1539 bool IRMover::StructTypeKeyInfo::isEqual(const StructType *LHS,
1540 const StructType *RHS) {
1541 if (RHS == getEmptyKey() || RHS == getTombstoneKey())
1542 return LHS == RHS;
1543 return KeyTy(LHS) == KeyTy(RHS);
1544 }
1545
addNonOpaque(StructType * Ty)1546 void IRMover::IdentifiedStructTypeSet::addNonOpaque(StructType *Ty) {
1547 assert(!Ty->isOpaque());
1548 NonOpaqueStructTypes.insert(Ty);
1549 }
1550
switchToNonOpaque(StructType * Ty)1551 void IRMover::IdentifiedStructTypeSet::switchToNonOpaque(StructType *Ty) {
1552 assert(!Ty->isOpaque());
1553 NonOpaqueStructTypes.insert(Ty);
1554 bool Removed = OpaqueStructTypes.erase(Ty);
1555 (void)Removed;
1556 assert(Removed);
1557 }
1558
addOpaque(StructType * Ty)1559 void IRMover::IdentifiedStructTypeSet::addOpaque(StructType *Ty) {
1560 assert(Ty->isOpaque());
1561 OpaqueStructTypes.insert(Ty);
1562 }
1563
1564 StructType *
findNonOpaque(ArrayRef<Type * > ETypes,bool IsPacked)1565 IRMover::IdentifiedStructTypeSet::findNonOpaque(ArrayRef<Type *> ETypes,
1566 bool IsPacked) {
1567 IRMover::StructTypeKeyInfo::KeyTy Key(ETypes, IsPacked);
1568 auto I = NonOpaqueStructTypes.find_as(Key);
1569 return I == NonOpaqueStructTypes.end() ? nullptr : *I;
1570 }
1571
hasType(StructType * Ty)1572 bool IRMover::IdentifiedStructTypeSet::hasType(StructType *Ty) {
1573 if (Ty->isOpaque())
1574 return OpaqueStructTypes.count(Ty);
1575 auto I = NonOpaqueStructTypes.find(Ty);
1576 return I == NonOpaqueStructTypes.end() ? false : *I == Ty;
1577 }
1578
IRMover(Module & M)1579 IRMover::IRMover(Module &M) : Composite(M) {
1580 TypeFinder StructTypes;
1581 StructTypes.run(M, /* OnlyNamed */ false);
1582 for (StructType *Ty : StructTypes) {
1583 if (Ty->isOpaque())
1584 IdentifiedStructTypes.addOpaque(Ty);
1585 else
1586 IdentifiedStructTypes.addNonOpaque(Ty);
1587 }
1588 // Self-map metadatas in the destination module. This is needed when
1589 // DebugTypeODRUniquing is enabled on the LLVMContext, since metadata in the
1590 // destination module may be reached from the source module.
1591 for (auto *MD : StructTypes.getVisitedMetadata()) {
1592 SharedMDs[MD].reset(const_cast<MDNode *>(MD));
1593 }
1594 }
1595
move(std::unique_ptr<Module> Src,ArrayRef<GlobalValue * > ValuesToLink,std::function<void (GlobalValue &,ValueAdder Add)> AddLazyFor,bool IsPerformingImport)1596 Error IRMover::move(
1597 std::unique_ptr<Module> Src, ArrayRef<GlobalValue *> ValuesToLink,
1598 std::function<void(GlobalValue &, ValueAdder Add)> AddLazyFor,
1599 bool IsPerformingImport) {
1600 IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
1601 std::move(Src), ValuesToLink, std::move(AddLazyFor),
1602 IsPerformingImport);
1603 Error E = TheIRLinker.run();
1604 Composite.dropTriviallyDeadConstantArrays();
1605 return E;
1606 }
1607