1 //===- CloneModule.cpp - Clone an entire module ---------------------------===//
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 CloneModule interface which makes a copy of an
11 // entire module.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/IR/Constant.h"
16 #include "llvm/IR/DerivedTypes.h"
17 #include "llvm/IR/Module.h"
18 #include "llvm/Transforms/Utils/Cloning.h"
19 #include "llvm/Transforms/Utils/ValueMapper.h"
20 using namespace llvm;
21 
22 static void copyComdat(GlobalObject *Dst, const GlobalObject *Src) {
23   const Comdat *SC = Src->getComdat();
24   if (!SC)
25     return;
26   Comdat *DC = Dst->getParent()->getOrInsertComdat(SC->getName());
27   DC->setSelectionKind(SC->getSelectionKind());
28   Dst->setComdat(DC);
29 }
30 
31 /// This is not as easy as it might seem because we have to worry about making
32 /// copies of global variables and functions, and making their (initializers and
33 /// references, respectively) refer to the right globals.
34 ///
35 std::unique_ptr<Module> llvm::CloneModule(const Module *M) {
36   // Create the value map that maps things from the old module over to the new
37   // module.
38   ValueToValueMapTy VMap;
39   return CloneModule(M, VMap);
40 }
41 
42 std::unique_ptr<Module> llvm::CloneModule(const Module *M,
43                                           ValueToValueMapTy &VMap) {
44   return CloneModule(M, VMap, [](const GlobalValue *GV) { return true; });
45 }
46 
47 std::unique_ptr<Module> llvm::CloneModule(
48     const Module *M, ValueToValueMapTy &VMap,
49     function_ref<bool(const GlobalValue *)> ShouldCloneDefinition) {
50   // First off, we need to create the new module.
51   std::unique_ptr<Module> New =
52       llvm::make_unique<Module>(M->getModuleIdentifier(), M->getContext());
53   New->setDataLayout(M->getDataLayout());
54   New->setTargetTriple(M->getTargetTriple());
55   New->setModuleInlineAsm(M->getModuleInlineAsm());
56 
57   // Loop over all of the global variables, making corresponding globals in the
58   // new module.  Here we add them to the VMap and to the new Module.  We
59   // don't worry about attributes or initializers, they will come later.
60   //
61   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
62        I != E; ++I) {
63     GlobalVariable *GV = new GlobalVariable(*New,
64                                             I->getValueType(),
65                                             I->isConstant(), I->getLinkage(),
66                                             (Constant*) nullptr, I->getName(),
67                                             (GlobalVariable*) nullptr,
68                                             I->getThreadLocalMode(),
69                                             I->getType()->getAddressSpace());
70     GV->copyAttributesFrom(&*I);
71     VMap[&*I] = GV;
72   }
73 
74   // Loop over the functions in the module, making external functions as before
75   for (const Function &I : *M) {
76     Function *NF = Function::Create(cast<FunctionType>(I.getValueType()),
77                                     I.getLinkage(), I.getName(), New.get());
78     NF->copyAttributesFrom(&I);
79     VMap[&I] = NF;
80   }
81 
82   // Loop over the aliases in the module
83   for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
84        I != E; ++I) {
85     if (!ShouldCloneDefinition(&*I)) {
86       // An alias cannot act as an external reference, so we need to create
87       // either a function or a global variable depending on the value type.
88       // FIXME: Once pointee types are gone we can probably pick one or the
89       // other.
90       GlobalValue *GV;
91       if (I->getValueType()->isFunctionTy())
92         GV = Function::Create(cast<FunctionType>(I->getValueType()),
93                               GlobalValue::ExternalLinkage, I->getName(),
94                               New.get());
95       else
96         GV = new GlobalVariable(
97             *New, I->getValueType(), false, GlobalValue::ExternalLinkage,
98             nullptr, I->getName(), nullptr,
99             I->getThreadLocalMode(), I->getType()->getAddressSpace());
100       VMap[&*I] = GV;
101       // We do not copy attributes (mainly because copying between different
102       // kinds of globals is forbidden), but this is generally not required for
103       // correctness.
104       continue;
105     }
106     auto *GA = GlobalAlias::create(I->getValueType(),
107                                    I->getType()->getPointerAddressSpace(),
108                                    I->getLinkage(), I->getName(), New.get());
109     GA->copyAttributesFrom(&*I);
110     VMap[&*I] = GA;
111   }
112 
113   // Now that all of the things that global variable initializer can refer to
114   // have been created, loop through and copy the global variable referrers
115   // over...  We also set the attributes on the global now.
116   //
117   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
118        I != E; ++I) {
119     if (I->isDeclaration())
120       continue;
121 
122     GlobalVariable *GV = cast<GlobalVariable>(VMap[&*I]);
123     if (!ShouldCloneDefinition(&*I)) {
124       // Skip after setting the correct linkage for an external reference.
125       GV->setLinkage(GlobalValue::ExternalLinkage);
126       continue;
127     }
128     if (I->hasInitializer())
129       GV->setInitializer(MapValue(I->getInitializer(), VMap));
130 
131     SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
132     I->getAllMetadata(MDs);
133     for (auto MD : MDs)
134       GV->addMetadata(MD.first,
135                       *MapMetadata(MD.second, VMap, RF_MoveDistinctMDs));
136 
137     copyComdat(GV, &*I);
138   }
139 
140   // Similarly, copy over function bodies now...
141   //
142   for (const Function &I : *M) {
143     if (I.isDeclaration())
144       continue;
145 
146     Function *F = cast<Function>(VMap[&I]);
147     if (!ShouldCloneDefinition(&I)) {
148       // Skip after setting the correct linkage for an external reference.
149       F->setLinkage(GlobalValue::ExternalLinkage);
150       // Personality function is not valid on a declaration.
151       F->setPersonalityFn(nullptr);
152       continue;
153     }
154 
155     Function::arg_iterator DestI = F->arg_begin();
156     for (Function::const_arg_iterator J = I.arg_begin(); J != I.arg_end();
157          ++J) {
158       DestI->setName(J->getName());
159       VMap[&*J] = &*DestI++;
160     }
161 
162     SmallVector<ReturnInst *, 8> Returns; // Ignore returns cloned.
163     CloneFunctionInto(F, &I, VMap, /*ModuleLevelChanges=*/true, Returns);
164 
165     if (I.hasPersonalityFn())
166       F->setPersonalityFn(MapValue(I.getPersonalityFn(), VMap));
167 
168     copyComdat(F, &I);
169   }
170 
171   // And aliases
172   for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
173        I != E; ++I) {
174     // We already dealt with undefined aliases above.
175     if (!ShouldCloneDefinition(&*I))
176       continue;
177     GlobalAlias *GA = cast<GlobalAlias>(VMap[&*I]);
178     if (const Constant *C = I->getAliasee())
179       GA->setAliasee(MapValue(C, VMap));
180   }
181 
182   // And named metadata....
183   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
184          E = M->named_metadata_end(); I != E; ++I) {
185     const NamedMDNode &NMD = *I;
186     NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
187     for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
188       NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
189   }
190 
191   return New;
192 }
193 
194 extern "C" {
195 
196 LLVMModuleRef LLVMCloneModule(LLVMModuleRef M) {
197   return wrap(CloneModule(unwrap(M)).release());
198 }
199 
200 }
201