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