1//===- lib/Linker/LinkModules.cpp - Module Linker Implementation ----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the LLVM module linker.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Linker.h"
15#include "llvm/Constants.h"
16#include "llvm/DerivedTypes.h"
17#include "llvm/Instructions.h"
18#include "llvm/Module.h"
19#include "llvm/ADT/SmallPtrSet.h"
20#include "llvm/Support/raw_ostream.h"
21#include "llvm/Support/Path.h"
22#include "llvm/Transforms/Utils/Cloning.h"
23#include "llvm/Transforms/Utils/ValueMapper.h"
24using namespace llvm;
25
26//===----------------------------------------------------------------------===//
27// TypeMap implementation.
28//===----------------------------------------------------------------------===//
29
30namespace {
31class TypeMapTy : public ValueMapTypeRemapper {
32  /// MappedTypes - This is a mapping from a source type to a destination type
33  /// to use.
34  DenseMap<Type*, Type*> MappedTypes;
35
36  /// SpeculativeTypes - When checking to see if two subgraphs are isomorphic,
37  /// we speculatively add types to MappedTypes, but keep track of them here in
38  /// case we need to roll back.
39  SmallVector<Type*, 16> SpeculativeTypes;
40
41  /// DefinitionsToResolve - This is a list of non-opaque structs in the source
42  /// module that are mapped to an opaque struct in the destination module.
43  SmallVector<StructType*, 16> DefinitionsToResolve;
44public:
45
46  /// addTypeMapping - Indicate that the specified type in the destination
47  /// module is conceptually equivalent to the specified type in the source
48  /// module.
49  void addTypeMapping(Type *DstTy, Type *SrcTy);
50
51  /// linkDefinedTypeBodies - Produce a body for an opaque type in the dest
52  /// module from a type definition in the source module.
53  void linkDefinedTypeBodies();
54
55  /// get - Return the mapped type to use for the specified input type from the
56  /// source module.
57  Type *get(Type *SrcTy);
58
59  FunctionType *get(FunctionType *T) {return cast<FunctionType>(get((Type*)T));}
60
61private:
62  Type *getImpl(Type *T);
63  /// remapType - Implement the ValueMapTypeRemapper interface.
64  Type *remapType(Type *SrcTy) {
65    return get(SrcTy);
66  }
67
68  bool areTypesIsomorphic(Type *DstTy, Type *SrcTy);
69};
70}
71
72void TypeMapTy::addTypeMapping(Type *DstTy, Type *SrcTy) {
73  Type *&Entry = MappedTypes[SrcTy];
74  if (Entry) return;
75
76  if (DstTy == SrcTy) {
77    Entry = DstTy;
78    return;
79  }
80
81  // Check to see if these types are recursively isomorphic and establish a
82  // mapping between them if so.
83  if (!areTypesIsomorphic(DstTy, SrcTy)) {
84    // Oops, they aren't isomorphic.  Just discard this request by rolling out
85    // any speculative mappings we've established.
86    for (unsigned i = 0, e = SpeculativeTypes.size(); i != e; ++i)
87      MappedTypes.erase(SpeculativeTypes[i]);
88  }
89  SpeculativeTypes.clear();
90}
91
92/// areTypesIsomorphic - Recursively walk this pair of types, returning true
93/// if they are isomorphic, false if they are not.
94bool TypeMapTy::areTypesIsomorphic(Type *DstTy, Type *SrcTy) {
95  // Two types with differing kinds are clearly not isomorphic.
96  if (DstTy->getTypeID() != SrcTy->getTypeID()) return false;
97
98  // If we have an entry in the MappedTypes table, then we have our answer.
99  Type *&Entry = MappedTypes[SrcTy];
100  if (Entry)
101    return Entry == DstTy;
102
103  // Two identical types are clearly isomorphic.  Remember this
104  // non-speculatively.
105  if (DstTy == SrcTy) {
106    Entry = DstTy;
107    return true;
108  }
109
110  // Okay, we have two types with identical kinds that we haven't seen before.
111
112  // If this is an opaque struct type, special case it.
113  if (StructType *SSTy = dyn_cast<StructType>(SrcTy)) {
114    // Mapping an opaque type to any struct, just keep the dest struct.
115    if (SSTy->isOpaque()) {
116      Entry = DstTy;
117      SpeculativeTypes.push_back(SrcTy);
118      return true;
119    }
120
121    // Mapping a non-opaque source type to an opaque dest.  Keep the dest, but
122    // fill it in later.  This doesn't need to be speculative.
123    if (cast<StructType>(DstTy)->isOpaque()) {
124      Entry = DstTy;
125      DefinitionsToResolve.push_back(SSTy);
126      return true;
127    }
128  }
129
130  // If the number of subtypes disagree between the two types, then we fail.
131  if (SrcTy->getNumContainedTypes() != DstTy->getNumContainedTypes())
132    return false;
133
134  // Fail if any of the extra properties (e.g. array size) of the type disagree.
135  if (isa<IntegerType>(DstTy))
136    return false;  // bitwidth disagrees.
137  if (PointerType *PT = dyn_cast<PointerType>(DstTy)) {
138    if (PT->getAddressSpace() != cast<PointerType>(SrcTy)->getAddressSpace())
139      return false;
140  } else if (FunctionType *FT = dyn_cast<FunctionType>(DstTy)) {
141    if (FT->isVarArg() != cast<FunctionType>(SrcTy)->isVarArg())
142      return false;
143  } else if (StructType *DSTy = dyn_cast<StructType>(DstTy)) {
144    StructType *SSTy = cast<StructType>(SrcTy);
145    if (DSTy->isLiteral() != SSTy->isLiteral() ||
146        DSTy->isPacked() != SSTy->isPacked())
147      return false;
148  } else if (ArrayType *DATy = dyn_cast<ArrayType>(DstTy)) {
149    if (DATy->getNumElements() != cast<ArrayType>(SrcTy)->getNumElements())
150      return false;
151  } else if (VectorType *DVTy = dyn_cast<VectorType>(DstTy)) {
152    if (DVTy->getNumElements() != cast<ArrayType>(SrcTy)->getNumElements())
153      return false;
154  }
155
156  // Otherwise, we speculate that these two types will line up and recursively
157  // check the subelements.
158  Entry = DstTy;
159  SpeculativeTypes.push_back(SrcTy);
160
161  for (unsigned i = 0, e = SrcTy->getNumContainedTypes(); i != e; ++i)
162    if (!areTypesIsomorphic(DstTy->getContainedType(i),
163                            SrcTy->getContainedType(i)))
164      return false;
165
166  // If everything seems to have lined up, then everything is great.
167  return true;
168}
169
170/// linkDefinedTypeBodies - Produce a body for an opaque type in the dest
171/// module from a type definition in the source module.
172void TypeMapTy::linkDefinedTypeBodies() {
173  SmallVector<Type*, 16> Elements;
174  SmallString<16> TmpName;
175
176  // Note that processing entries in this loop (calling 'get') can add new
177  // entries to the DefinitionsToResolve vector.
178  while (!DefinitionsToResolve.empty()) {
179    StructType *SrcSTy = DefinitionsToResolve.pop_back_val();
180    StructType *DstSTy = cast<StructType>(MappedTypes[SrcSTy]);
181
182    // TypeMap is a many-to-one mapping, if there were multiple types that
183    // provide a body for DstSTy then previous iterations of this loop may have
184    // already handled it.  Just ignore this case.
185    if (!DstSTy->isOpaque()) continue;
186    assert(!SrcSTy->isOpaque() && "Not resolving a definition?");
187
188    // Map the body of the source type over to a new body for the dest type.
189    Elements.resize(SrcSTy->getNumElements());
190    for (unsigned i = 0, e = Elements.size(); i != e; ++i)
191      Elements[i] = getImpl(SrcSTy->getElementType(i));
192
193    DstSTy->setBody(Elements, SrcSTy->isPacked());
194
195    // If DstSTy has no name or has a longer name than STy, then viciously steal
196    // STy's name.
197    if (!SrcSTy->hasName()) continue;
198    StringRef SrcName = SrcSTy->getName();
199
200    if (!DstSTy->hasName() || DstSTy->getName().size() > SrcName.size()) {
201      TmpName.insert(TmpName.end(), SrcName.begin(), SrcName.end());
202      SrcSTy->setName("");
203      DstSTy->setName(TmpName.str());
204      TmpName.clear();
205    }
206  }
207}
208
209
210/// get - Return the mapped type to use for the specified input type from the
211/// source module.
212Type *TypeMapTy::get(Type *Ty) {
213  Type *Result = getImpl(Ty);
214
215  // If this caused a reference to any struct type, resolve it before returning.
216  if (!DefinitionsToResolve.empty())
217    linkDefinedTypeBodies();
218  return Result;
219}
220
221/// getImpl - This is the recursive version of get().
222Type *TypeMapTy::getImpl(Type *Ty) {
223  // If we already have an entry for this type, return it.
224  Type **Entry = &MappedTypes[Ty];
225  if (*Entry) return *Entry;
226
227  // If this is not a named struct type, then just map all of the elements and
228  // then rebuild the type from inside out.
229  if (!isa<StructType>(Ty) || cast<StructType>(Ty)->isLiteral()) {
230    // If there are no element types to map, then the type is itself.  This is
231    // true for the anonymous {} struct, things like 'float', integers, etc.
232    if (Ty->getNumContainedTypes() == 0)
233      return *Entry = Ty;
234
235    // Remap all of the elements, keeping track of whether any of them change.
236    bool AnyChange = false;
237    SmallVector<Type*, 4> ElementTypes;
238    ElementTypes.resize(Ty->getNumContainedTypes());
239    for (unsigned i = 0, e = Ty->getNumContainedTypes(); i != e; ++i) {
240      ElementTypes[i] = getImpl(Ty->getContainedType(i));
241      AnyChange |= ElementTypes[i] != Ty->getContainedType(i);
242    }
243
244    // If we found our type while recursively processing stuff, just use it.
245    Entry = &MappedTypes[Ty];
246    if (*Entry) return *Entry;
247
248    // If all of the element types mapped directly over, then the type is usable
249    // as-is.
250    if (!AnyChange)
251      return *Entry = Ty;
252
253    // Otherwise, rebuild a modified type.
254    switch (Ty->getTypeID()) {
255    default: assert(0 && "unknown derived type to remap");
256    case Type::ArrayTyID:
257      return *Entry = ArrayType::get(ElementTypes[0],
258                                     cast<ArrayType>(Ty)->getNumElements());
259    case Type::VectorTyID:
260      return *Entry = VectorType::get(ElementTypes[0],
261                                      cast<VectorType>(Ty)->getNumElements());
262    case Type::PointerTyID:
263      return *Entry = PointerType::get(ElementTypes[0],
264                                      cast<PointerType>(Ty)->getAddressSpace());
265    case Type::FunctionTyID:
266      return *Entry = FunctionType::get(ElementTypes[0],
267                                        makeArrayRef(ElementTypes).slice(1),
268                                        cast<FunctionType>(Ty)->isVarArg());
269    case Type::StructTyID:
270      // Note that this is only reached for anonymous structs.
271      return *Entry = StructType::get(Ty->getContext(), ElementTypes,
272                                      cast<StructType>(Ty)->isPacked());
273    }
274  }
275
276  // Otherwise, this is an unmapped named struct.  If the struct can be directly
277  // mapped over, just use it as-is.  This happens in a case when the linked-in
278  // module has something like:
279  //   %T = type {%T*, i32}
280  //   @GV = global %T* null
281  // where T does not exist at all in the destination module.
282  //
283  // The other case we watch for is when the type is not in the destination
284  // module, but that it has to be rebuilt because it refers to something that
285  // is already mapped.  For example, if the destination module has:
286  //  %A = type { i32 }
287  // and the source module has something like
288  //  %A' = type { i32 }
289  //  %B = type { %A'* }
290  //  @GV = global %B* null
291  // then we want to create a new type: "%B = type { %A*}" and have it take the
292  // pristine "%B" name from the source module.
293  //
294  // To determine which case this is, we have to recursively walk the type graph
295  // speculating that we'll be able to reuse it unmodified.  Only if this is
296  // safe would we map the entire thing over.  Because this is an optimization,
297  // and is not required for the prettiness of the linked module, we just skip
298  // it and always rebuild a type here.
299  StructType *STy = cast<StructType>(Ty);
300
301  // If the type is opaque, we can just use it directly.
302  if (STy->isOpaque())
303    return *Entry = STy;
304
305  // Otherwise we create a new type and resolve its body later.  This will be
306  // resolved by the top level of get().
307  DefinitionsToResolve.push_back(STy);
308  return *Entry = StructType::create(STy->getContext());
309}
310
311
312
313//===----------------------------------------------------------------------===//
314// ModuleLinker implementation.
315//===----------------------------------------------------------------------===//
316
317namespace {
318  /// ModuleLinker - This is an implementation class for the LinkModules
319  /// function, which is the entrypoint for this file.
320  class ModuleLinker {
321    Module *DstM, *SrcM;
322
323    TypeMapTy TypeMap;
324
325    /// ValueMap - Mapping of values from what they used to be in Src, to what
326    /// they are now in DstM.  ValueToValueMapTy is a ValueMap, which involves
327    /// some overhead due to the use of Value handles which the Linker doesn't
328    /// actually need, but this allows us to reuse the ValueMapper code.
329    ValueToValueMapTy ValueMap;
330
331    struct AppendingVarInfo {
332      GlobalVariable *NewGV;  // New aggregate global in dest module.
333      Constant *DstInit;      // Old initializer from dest module.
334      Constant *SrcInit;      // Old initializer from src module.
335    };
336
337    std::vector<AppendingVarInfo> AppendingVars;
338
339    unsigned Mode; // Mode to treat source module.
340
341    // Set of items not to link in from source.
342    SmallPtrSet<const Value*, 16> DoNotLinkFromSource;
343
344  public:
345    std::string ErrorMsg;
346
347    ModuleLinker(Module *dstM, Module *srcM, unsigned mode)
348      : DstM(dstM), SrcM(srcM), Mode(mode) { }
349
350    bool run();
351
352  private:
353    /// emitError - Helper method for setting a message and returning an error
354    /// code.
355    bool emitError(const Twine &Message) {
356      ErrorMsg = Message.str();
357      return true;
358    }
359
360    /// getLinkageResult - This analyzes the two global values and determines
361    /// what the result will look like in the destination module.
362    bool getLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
363                          GlobalValue::LinkageTypes &LT, bool &LinkFromSrc);
364
365    /// getLinkedToGlobal - Given a global in the source module, return the
366    /// global in the destination module that is being linked to, if any.
367    GlobalValue *getLinkedToGlobal(GlobalValue *SrcGV) {
368      // If the source has no name it can't link.  If it has local linkage,
369      // there is no name match-up going on.
370      if (!SrcGV->hasName() || SrcGV->hasLocalLinkage())
371        return 0;
372
373      // Otherwise see if we have a match in the destination module's symtab.
374      GlobalValue *DGV = DstM->getNamedValue(SrcGV->getName());
375      if (DGV == 0) return 0;
376
377      // If we found a global with the same name in the dest module, but it has
378      // internal linkage, we are really not doing any linkage here.
379      if (DGV->hasLocalLinkage())
380        return 0;
381
382      // Otherwise, we do in fact link to the destination global.
383      return DGV;
384    }
385
386    void computeTypeMapping();
387
388    bool linkAppendingVarProto(GlobalVariable *DstGV, GlobalVariable *SrcGV);
389    bool linkGlobalProto(GlobalVariable *SrcGV);
390    bool linkFunctionProto(Function *SrcF);
391    bool linkAliasProto(GlobalAlias *SrcA);
392
393    void linkAppendingVarInit(const AppendingVarInfo &AVI);
394    void linkGlobalInits();
395    void linkFunctionBody(Function *Dst, Function *Src);
396    void linkAliasBodies();
397    void linkNamedMDNodes();
398  };
399}
400
401
402
403/// forceRenaming - The LLVM SymbolTable class autorenames globals that conflict
404/// in the symbol table.  This is good for all clients except for us.  Go
405/// through the trouble to force this back.
406static void forceRenaming(GlobalValue *GV, StringRef Name) {
407  // If the global doesn't force its name or if it already has the right name,
408  // there is nothing for us to do.
409  if (GV->hasLocalLinkage() || GV->getName() == Name)
410    return;
411
412  Module *M = GV->getParent();
413
414  // If there is a conflict, rename the conflict.
415  if (GlobalValue *ConflictGV = M->getNamedValue(Name)) {
416    GV->takeName(ConflictGV);
417    ConflictGV->setName(Name);    // This will cause ConflictGV to get renamed
418    assert(ConflictGV->getName() != Name && "forceRenaming didn't work");
419  } else {
420    GV->setName(Name);              // Force the name back
421  }
422}
423
424/// CopyGVAttributes - copy additional attributes (those not needed to construct
425/// a GlobalValue) from the SrcGV to the DestGV.
426static void CopyGVAttributes(GlobalValue *DestGV, const GlobalValue *SrcGV) {
427  // Use the maximum alignment, rather than just copying the alignment of SrcGV.
428  unsigned Alignment = std::max(DestGV->getAlignment(), SrcGV->getAlignment());
429  DestGV->copyAttributesFrom(SrcGV);
430  DestGV->setAlignment(Alignment);
431
432  forceRenaming(DestGV, SrcGV->getName());
433}
434
435/// getLinkageResult - This analyzes the two global values and determines what
436/// the result will look like in the destination module.  In particular, it
437/// computes the resultant linkage type, computes whether the global in the
438/// source should be copied over to the destination (replacing the existing
439/// one), and computes whether this linkage is an error or not. It also performs
440/// visibility checks: we cannot link together two symbols with different
441/// visibilities.
442bool ModuleLinker::getLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
443                                    GlobalValue::LinkageTypes &LT,
444                                    bool &LinkFromSrc) {
445  assert(Dest && "Must have two globals being queried");
446  assert(!Src->hasLocalLinkage() &&
447         "If Src has internal linkage, Dest shouldn't be set!");
448
449  bool SrcIsDeclaration = Src->isDeclaration();
450  bool DestIsDeclaration = Dest->isDeclaration();
451
452  if (SrcIsDeclaration) {
453    // If Src is external or if both Src & Dest are external..  Just link the
454    // external globals, we aren't adding anything.
455    if (Src->hasDLLImportLinkage()) {
456      // If one of GVs has DLLImport linkage, result should be dllimport'ed.
457      if (DestIsDeclaration) {
458        LinkFromSrc = true;
459        LT = Src->getLinkage();
460      }
461    } else if (Dest->hasExternalWeakLinkage()) {
462      // If the Dest is weak, use the source linkage.
463      LinkFromSrc = true;
464      LT = Src->getLinkage();
465    } else {
466      LinkFromSrc = false;
467      LT = Dest->getLinkage();
468    }
469  } else if (DestIsDeclaration && !Dest->hasDLLImportLinkage()) {
470    // If Dest is external but Src is not:
471    LinkFromSrc = true;
472    LT = Src->getLinkage();
473  } else if (Src->isWeakForLinker()) {
474    // At this point we know that Dest has LinkOnce, External*, Weak, Common,
475    // or DLL* linkage.
476    if (Dest->hasExternalWeakLinkage() ||
477        Dest->hasAvailableExternallyLinkage() ||
478        (Dest->hasLinkOnceLinkage() &&
479         (Src->hasWeakLinkage() || Src->hasCommonLinkage()))) {
480      LinkFromSrc = true;
481      LT = Src->getLinkage();
482    } else {
483      LinkFromSrc = false;
484      LT = Dest->getLinkage();
485    }
486  } else if (Dest->isWeakForLinker()) {
487    // At this point we know that Src has External* or DLL* linkage.
488    if (Src->hasExternalWeakLinkage()) {
489      LinkFromSrc = false;
490      LT = Dest->getLinkage();
491    } else {
492      LinkFromSrc = true;
493      LT = GlobalValue::ExternalLinkage;
494    }
495  } else {
496    assert((Dest->hasExternalLinkage()  || Dest->hasDLLImportLinkage() ||
497            Dest->hasDLLExportLinkage() || Dest->hasExternalWeakLinkage()) &&
498           (Src->hasExternalLinkage()   || Src->hasDLLImportLinkage() ||
499            Src->hasDLLExportLinkage()  || Src->hasExternalWeakLinkage()) &&
500           "Unexpected linkage type!");
501    return emitError("Linking globals named '" + Src->getName() +
502                 "': symbol multiply defined!");
503  }
504
505  // Check visibility
506  if (Src->getVisibility() != Dest->getVisibility() &&
507      !SrcIsDeclaration && !DestIsDeclaration &&
508      !Src->hasAvailableExternallyLinkage() &&
509      !Dest->hasAvailableExternallyLinkage())
510    return emitError("Linking globals named '" + Src->getName() +
511                   "': symbols have different visibilities!");
512  return false;
513}
514
515/// computeTypeMapping - Loop over all of the linked values to compute type
516/// mappings.  For example, if we link "extern Foo *x" and "Foo *x = NULL", then
517/// we have two struct types 'Foo' but one got renamed when the module was
518/// loaded into the same LLVMContext.
519void ModuleLinker::computeTypeMapping() {
520  // Incorporate globals.
521  for (Module::global_iterator I = SrcM->global_begin(),
522       E = SrcM->global_end(); I != E; ++I) {
523    GlobalValue *DGV = getLinkedToGlobal(I);
524    if (DGV == 0) continue;
525
526    if (!DGV->hasAppendingLinkage() || !I->hasAppendingLinkage()) {
527      TypeMap.addTypeMapping(DGV->getType(), I->getType());
528      continue;
529    }
530
531    // Unify the element type of appending arrays.
532    ArrayType *DAT = cast<ArrayType>(DGV->getType()->getElementType());
533    ArrayType *SAT = cast<ArrayType>(I->getType()->getElementType());
534    TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
535  }
536
537  // Incorporate functions.
538  for (Module::iterator I = SrcM->begin(), E = SrcM->end(); I != E; ++I) {
539    if (GlobalValue *DGV = getLinkedToGlobal(I))
540      TypeMap.addTypeMapping(DGV->getType(), I->getType());
541  }
542
543  // Don't bother incorporating aliases, they aren't generally typed well.
544
545  // Now that we have discovered all of the type equivalences, get a body for
546  // any 'opaque' types in the dest module that are now resolved.
547  TypeMap.linkDefinedTypeBodies();
548}
549
550/// linkAppendingVarProto - If there were any appending global variables, link
551/// them together now.  Return true on error.
552bool ModuleLinker::linkAppendingVarProto(GlobalVariable *DstGV,
553                                         GlobalVariable *SrcGV) {
554
555  if (!SrcGV->hasAppendingLinkage() || !DstGV->hasAppendingLinkage())
556    return emitError("Linking globals named '" + SrcGV->getName() +
557           "': can only link appending global with another appending global!");
558
559  ArrayType *DstTy = cast<ArrayType>(DstGV->getType()->getElementType());
560  ArrayType *SrcTy =
561    cast<ArrayType>(TypeMap.get(SrcGV->getType()->getElementType()));
562  Type *EltTy = DstTy->getElementType();
563
564  // Check to see that they two arrays agree on type.
565  if (EltTy != SrcTy->getElementType())
566    return emitError("Appending variables with different element types!");
567  if (DstGV->isConstant() != SrcGV->isConstant())
568    return emitError("Appending variables linked with different const'ness!");
569
570  if (DstGV->getAlignment() != SrcGV->getAlignment())
571    return emitError(
572             "Appending variables with different alignment need to be linked!");
573
574  if (DstGV->getVisibility() != SrcGV->getVisibility())
575    return emitError(
576            "Appending variables with different visibility need to be linked!");
577
578  if (DstGV->getSection() != SrcGV->getSection())
579    return emitError(
580          "Appending variables with different section name need to be linked!");
581
582  uint64_t NewSize = DstTy->getNumElements() + SrcTy->getNumElements();
583  ArrayType *NewType = ArrayType::get(EltTy, NewSize);
584
585  // Create the new global variable.
586  GlobalVariable *NG =
587    new GlobalVariable(*DstGV->getParent(), NewType, SrcGV->isConstant(),
588                       DstGV->getLinkage(), /*init*/0, /*name*/"", DstGV,
589                       DstGV->isThreadLocal(),
590                       DstGV->getType()->getAddressSpace());
591
592  // Propagate alignment, visibility and section info.
593  CopyGVAttributes(NG, DstGV);
594
595  AppendingVarInfo AVI;
596  AVI.NewGV = NG;
597  AVI.DstInit = DstGV->getInitializer();
598  AVI.SrcInit = SrcGV->getInitializer();
599  AppendingVars.push_back(AVI);
600
601  // Replace any uses of the two global variables with uses of the new
602  // global.
603  ValueMap[SrcGV] = ConstantExpr::getBitCast(NG, TypeMap.get(SrcGV->getType()));
604
605  DstGV->replaceAllUsesWith(ConstantExpr::getBitCast(NG, DstGV->getType()));
606  DstGV->eraseFromParent();
607
608  // Track the source variable so we don't try to link it.
609  DoNotLinkFromSource.insert(SrcGV);
610
611  return false;
612}
613
614/// linkGlobalProto - Loop through the global variables in the src module and
615/// merge them into the dest module.
616bool ModuleLinker::linkGlobalProto(GlobalVariable *SGV) {
617  GlobalValue *DGV = getLinkedToGlobal(SGV);
618
619  if (DGV) {
620    // Concatenation of appending linkage variables is magic and handled later.
621    if (DGV->hasAppendingLinkage() || SGV->hasAppendingLinkage())
622      return linkAppendingVarProto(cast<GlobalVariable>(DGV), SGV);
623
624    // Determine whether linkage of these two globals follows the source
625    // module's definition or the destination module's definition.
626    GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage;
627    bool LinkFromSrc = false;
628    if (getLinkageResult(DGV, SGV, NewLinkage, LinkFromSrc))
629      return true;
630
631    // If we're not linking from the source, then keep the definition that we
632    // have.
633    if (!LinkFromSrc) {
634      // Special case for const propagation.
635      if (GlobalVariable *DGVar = dyn_cast<GlobalVariable>(DGV))
636        if (DGVar->isDeclaration() && SGV->isConstant() && !DGVar->isConstant())
637          DGVar->setConstant(true);
638
639      // Set calculated linkage.
640      DGV->setLinkage(NewLinkage);
641
642      // Make sure to remember this mapping.
643      ValueMap[SGV] = ConstantExpr::getBitCast(DGV,TypeMap.get(SGV->getType()));
644
645      // Track the source global so that we don't attempt to copy it over when
646      // processing global initializers.
647      DoNotLinkFromSource.insert(SGV);
648
649      return false;
650    }
651  }
652
653  // No linking to be performed or linking from the source: simply create an
654  // identical version of the symbol over in the dest module... the
655  // initializer will be filled in later by LinkGlobalInits.
656  GlobalVariable *NewDGV =
657    new GlobalVariable(*DstM, TypeMap.get(SGV->getType()->getElementType()),
658                       SGV->isConstant(), SGV->getLinkage(), /*init*/0,
659                       SGV->getName(), /*insertbefore*/0,
660                       SGV->isThreadLocal(),
661                       SGV->getType()->getAddressSpace());
662  // Propagate alignment, visibility and section info.
663  CopyGVAttributes(NewDGV, SGV);
664
665  if (DGV) {
666    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDGV, DGV->getType()));
667    DGV->eraseFromParent();
668  }
669
670  // Make sure to remember this mapping.
671  ValueMap[SGV] = NewDGV;
672  return false;
673}
674
675/// linkFunctionProto - Link the function in the source module into the
676/// destination module if needed, setting up mapping information.
677bool ModuleLinker::linkFunctionProto(Function *SF) {
678  GlobalValue *DGV = getLinkedToGlobal(SF);
679
680  if (DGV) {
681    GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage;
682    bool LinkFromSrc = false;
683    if (getLinkageResult(DGV, SF, NewLinkage, LinkFromSrc))
684      return true;
685
686    if (!LinkFromSrc) {
687      // Set calculated linkage
688      DGV->setLinkage(NewLinkage);
689
690      // Make sure to remember this mapping.
691      ValueMap[SF] = ConstantExpr::getBitCast(DGV, TypeMap.get(SF->getType()));
692
693      // Track the function from the source module so we don't attempt to remap
694      // it.
695      DoNotLinkFromSource.insert(SF);
696
697      return false;
698    }
699  }
700
701  // If there is no linkage to be performed or we are linking from the source,
702  // bring SF over.
703  Function *NewDF = Function::Create(TypeMap.get(SF->getFunctionType()),
704                                     SF->getLinkage(), SF->getName(), DstM);
705  CopyGVAttributes(NewDF, SF);
706
707  if (DGV) {
708    // Any uses of DF need to change to NewDF, with cast.
709    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDF, DGV->getType()));
710    DGV->eraseFromParent();
711  }
712
713  ValueMap[SF] = NewDF;
714  return false;
715}
716
717/// LinkAliasProto - Set up prototypes for any aliases that come over from the
718/// source module.
719bool ModuleLinker::linkAliasProto(GlobalAlias *SGA) {
720  GlobalValue *DGV = getLinkedToGlobal(SGA);
721
722  if (DGV) {
723    GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage;
724    bool LinkFromSrc = false;
725    if (getLinkageResult(DGV, SGA, NewLinkage, LinkFromSrc))
726      return true;
727
728    if (!LinkFromSrc) {
729      // Set calculated linkage.
730      DGV->setLinkage(NewLinkage);
731
732      // Make sure to remember this mapping.
733      ValueMap[SGA] = ConstantExpr::getBitCast(DGV,TypeMap.get(SGA->getType()));
734
735      // Track the alias from the source module so we don't attempt to remap it.
736      DoNotLinkFromSource.insert(SGA);
737
738      return false;
739    }
740  }
741
742  // If there is no linkage to be performed or we're linking from the source,
743  // bring over SGA.
744  GlobalAlias *NewDA = new GlobalAlias(TypeMap.get(SGA->getType()),
745                                       SGA->getLinkage(), SGA->getName(),
746                                       /*aliasee*/0, DstM);
747  CopyGVAttributes(NewDA, SGA);
748
749  if (DGV) {
750    // Any uses of DGV need to change to NewDA, with cast.
751    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDA, DGV->getType()));
752    DGV->eraseFromParent();
753  }
754
755  ValueMap[SGA] = NewDA;
756  return false;
757}
758
759void ModuleLinker::linkAppendingVarInit(const AppendingVarInfo &AVI) {
760  // Merge the initializer.
761  SmallVector<Constant*, 16> Elements;
762  if (ConstantArray *I = dyn_cast<ConstantArray>(AVI.DstInit)) {
763    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
764      Elements.push_back(I->getOperand(i));
765  } else {
766    assert(isa<ConstantAggregateZero>(AVI.DstInit));
767    ArrayType *DstAT = cast<ArrayType>(AVI.DstInit->getType());
768    Type *EltTy = DstAT->getElementType();
769    Elements.append(DstAT->getNumElements(), Constant::getNullValue(EltTy));
770  }
771
772  Constant *SrcInit = MapValue(AVI.SrcInit, ValueMap, RF_None, &TypeMap);
773  if (const ConstantArray *I = dyn_cast<ConstantArray>(SrcInit)) {
774    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
775      Elements.push_back(I->getOperand(i));
776  } else {
777    assert(isa<ConstantAggregateZero>(SrcInit));
778    ArrayType *SrcAT = cast<ArrayType>(SrcInit->getType());
779    Type *EltTy = SrcAT->getElementType();
780    Elements.append(SrcAT->getNumElements(), Constant::getNullValue(EltTy));
781  }
782  ArrayType *NewType = cast<ArrayType>(AVI.NewGV->getType()->getElementType());
783  AVI.NewGV->setInitializer(ConstantArray::get(NewType, Elements));
784}
785
786
787// linkGlobalInits - Update the initializers in the Dest module now that all
788// globals that may be referenced are in Dest.
789void ModuleLinker::linkGlobalInits() {
790  // Loop over all of the globals in the src module, mapping them over as we go
791  for (Module::const_global_iterator I = SrcM->global_begin(),
792       E = SrcM->global_end(); I != E; ++I) {
793
794    // Only process initialized GV's or ones not already in dest.
795    if (!I->hasInitializer() || DoNotLinkFromSource.count(I)) continue;
796
797    // Grab destination global variable.
798    GlobalVariable *DGV = cast<GlobalVariable>(ValueMap[I]);
799    // Figure out what the initializer looks like in the dest module.
800    DGV->setInitializer(MapValue(I->getInitializer(), ValueMap,
801                                 RF_None, &TypeMap));
802  }
803}
804
805// linkFunctionBody - Copy the source function over into the dest function and
806// fix up references to values.  At this point we know that Dest is an external
807// function, and that Src is not.
808void ModuleLinker::linkFunctionBody(Function *Dst, Function *Src) {
809  assert(Src && Dst && Dst->isDeclaration() && !Src->isDeclaration());
810
811  // Go through and convert function arguments over, remembering the mapping.
812  Function::arg_iterator DI = Dst->arg_begin();
813  for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();
814       I != E; ++I, ++DI) {
815    DI->setName(I->getName());  // Copy the name over.
816
817    // Add a mapping to our mapping.
818    ValueMap[I] = DI;
819  }
820
821  if (Mode == Linker::DestroySource) {
822    // Splice the body of the source function into the dest function.
823    Dst->getBasicBlockList().splice(Dst->end(), Src->getBasicBlockList());
824
825    // At this point, all of the instructions and values of the function are now
826    // copied over.  The only problem is that they are still referencing values in
827    // the Source function as operands.  Loop through all of the operands of the
828    // functions and patch them up to point to the local versions.
829    for (Function::iterator BB = Dst->begin(), BE = Dst->end(); BB != BE; ++BB)
830      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
831        RemapInstruction(I, ValueMap, RF_IgnoreMissingEntries, &TypeMap);
832
833  } else {
834    // Clone the body of the function into the dest function.
835    SmallVector<ReturnInst*, 8> Returns; // Ignore returns.
836    CloneFunctionInto(Dst, Src, ValueMap, false, Returns);
837  }
838
839  // There is no need to map the arguments anymore.
840  for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();
841       I != E; ++I)
842    ValueMap.erase(I);
843
844}
845
846
847void ModuleLinker::linkAliasBodies() {
848  for (Module::alias_iterator I = SrcM->alias_begin(), E = SrcM->alias_end();
849       I != E; ++I) {
850    if (DoNotLinkFromSource.count(I))
851      continue;
852    if (Constant *Aliasee = I->getAliasee()) {
853      GlobalAlias *DA = cast<GlobalAlias>(ValueMap[I]);
854      DA->setAliasee(MapValue(Aliasee, ValueMap, RF_None, &TypeMap));
855    }
856  }
857}
858
859/// linkNamedMDNodes - Insert all of the named mdnodes in Src into the Dest
860/// module.
861void ModuleLinker::linkNamedMDNodes() {
862  for (Module::const_named_metadata_iterator I = SrcM->named_metadata_begin(),
863       E = SrcM->named_metadata_end(); I != E; ++I) {
864    NamedMDNode *DestNMD = DstM->getOrInsertNamedMetadata(I->getName());
865    // Add Src elements into Dest node.
866    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
867      DestNMD->addOperand(MapValue(I->getOperand(i), ValueMap,
868                                   RF_None, &TypeMap));
869  }
870}
871
872bool ModuleLinker::run() {
873  assert(DstM && "Null Destination module");
874  assert(SrcM && "Null Source Module");
875
876  // Inherit the target data from the source module if the destination module
877  // doesn't have one already.
878  if (DstM->getDataLayout().empty() && !SrcM->getDataLayout().empty())
879    DstM->setDataLayout(SrcM->getDataLayout());
880
881  // Copy the target triple from the source to dest if the dest's is empty.
882  if (DstM->getTargetTriple().empty() && !SrcM->getTargetTriple().empty())
883    DstM->setTargetTriple(SrcM->getTargetTriple());
884
885  if (!SrcM->getDataLayout().empty() && !DstM->getDataLayout().empty() &&
886      SrcM->getDataLayout() != DstM->getDataLayout())
887    errs() << "WARNING: Linking two modules of different data layouts!\n";
888  if (!SrcM->getTargetTriple().empty() &&
889      DstM->getTargetTriple() != SrcM->getTargetTriple()) {
890    errs() << "WARNING: Linking two modules of different target triples: ";
891    if (!SrcM->getModuleIdentifier().empty())
892      errs() << SrcM->getModuleIdentifier() << ": ";
893    errs() << "'" << SrcM->getTargetTriple() << "' and '"
894           << DstM->getTargetTriple() << "'\n";
895  }
896
897  // Append the module inline asm string.
898  if (!SrcM->getModuleInlineAsm().empty()) {
899    if (DstM->getModuleInlineAsm().empty())
900      DstM->setModuleInlineAsm(SrcM->getModuleInlineAsm());
901    else
902      DstM->setModuleInlineAsm(DstM->getModuleInlineAsm()+"\n"+
903                               SrcM->getModuleInlineAsm());
904  }
905
906  // Update the destination module's dependent libraries list with the libraries
907  // from the source module. There's no opportunity for duplicates here as the
908  // Module ensures that duplicate insertions are discarded.
909  for (Module::lib_iterator SI = SrcM->lib_begin(), SE = SrcM->lib_end();
910       SI != SE; ++SI)
911    DstM->addLibrary(*SI);
912
913  // If the source library's module id is in the dependent library list of the
914  // destination library, remove it since that module is now linked in.
915  StringRef ModuleId = SrcM->getModuleIdentifier();
916  if (!ModuleId.empty())
917    DstM->removeLibrary(sys::path::stem(ModuleId));
918
919  // Loop over all of the linked values to compute type mappings.
920  computeTypeMapping();
921
922  // Insert all of the globals in src into the DstM module... without linking
923  // initializers (which could refer to functions not yet mapped over).
924  for (Module::global_iterator I = SrcM->global_begin(),
925       E = SrcM->global_end(); I != E; ++I)
926    if (linkGlobalProto(I))
927      return true;
928
929  // Link the functions together between the two modules, without doing function
930  // bodies... this just adds external function prototypes to the DstM
931  // function...  We do this so that when we begin processing function bodies,
932  // all of the global values that may be referenced are available in our
933  // ValueMap.
934  for (Module::iterator I = SrcM->begin(), E = SrcM->end(); I != E; ++I)
935    if (linkFunctionProto(I))
936      return true;
937
938  // If there were any aliases, link them now.
939  for (Module::alias_iterator I = SrcM->alias_begin(),
940       E = SrcM->alias_end(); I != E; ++I)
941    if (linkAliasProto(I))
942      return true;
943
944  for (unsigned i = 0, e = AppendingVars.size(); i != e; ++i)
945    linkAppendingVarInit(AppendingVars[i]);
946
947  // Update the initializers in the DstM module now that all globals that may
948  // be referenced are in DstM.
949  linkGlobalInits();
950
951  // Link in the function bodies that are defined in the source module into
952  // DstM.
953  for (Module::iterator SF = SrcM->begin(), E = SrcM->end(); SF != E; ++SF) {
954
955    // Skip if not linking from source.
956    if (DoNotLinkFromSource.count(SF)) continue;
957
958    // Skip if no body (function is external) or materialize.
959    if (SF->isDeclaration()) {
960      if (!SF->isMaterializable())
961        continue;
962      if (SF->Materialize(&ErrorMsg))
963        return true;
964    }
965
966    linkFunctionBody(cast<Function>(ValueMap[SF]), SF);
967  }
968
969  // Resolve all uses of aliases with aliasees.
970  linkAliasBodies();
971
972  // Remap all of the named mdnoes in Src into the DstM module. We do this
973  // after linking GlobalValues so that MDNodes that reference GlobalValues
974  // are properly remapped.
975  linkNamedMDNodes();
976
977  // Now that all of the types from the source are used, resolve any structs
978  // copied over to the dest that didn't exist there.
979  TypeMap.linkDefinedTypeBodies();
980
981  return false;
982}
983
984//===----------------------------------------------------------------------===//
985// LinkModules entrypoint.
986//===----------------------------------------------------------------------===//
987
988// LinkModules - This function links two modules together, with the resulting
989// left module modified to be the composite of the two input modules.  If an
990// error occurs, true is returned and ErrorMsg (if not null) is set to indicate
991// the problem.  Upon failure, the Dest module could be in a modified state, and
992// shouldn't be relied on to be consistent.
993bool Linker::LinkModules(Module *Dest, Module *Src, unsigned Mode,
994                         std::string *ErrorMsg) {
995  ModuleLinker TheLinker(Dest, Src, Mode);
996  if (TheLinker.run()) {
997    if (ErrorMsg) *ErrorMsg = TheLinker.ErrorMsg;
998    return true;
999  }
1000
1001  return false;
1002}
1003