1 //===- CloneModule.cpp - Clone an entire module ---------------------------===//
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 // This file implements the CloneModule interface which makes a copy of an
10 // entire module.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/IR/Constant.h"
15 #include "llvm/IR/DerivedTypes.h"
16 #include "llvm/IR/Module.h"
17 #include "llvm/Transforms/Utils/Cloning.h"
18 #include "llvm/Transforms/Utils/ValueMapper.h"
19 using namespace llvm;
20 
21 static void copyComdat(GlobalObject *Dst, const GlobalObject *Src) {
22   const Comdat *SC = Src->getComdat();
23   if (!SC)
24     return;
25   Comdat *DC = Dst->getParent()->getOrInsertComdat(SC->getName());
26   DC->setSelectionKind(SC->getSelectionKind());
27   Dst->setComdat(DC);
28 }
29 
30 /// This is not as easy as it might seem because we have to worry about making
31 /// copies of global variables and functions, and making their (initializers and
32 /// references, respectively) refer to the right globals.
33 ///
34 std::unique_ptr<Module> llvm::CloneModule(const Module &M) {
35   // Create the value map that maps things from the old module over to the new
36   // module.
37   ValueToValueMapTy VMap;
38   return CloneModule(M, VMap);
39 }
40 
41 std::unique_ptr<Module> llvm::CloneModule(const Module &M,
42                                           ValueToValueMapTy &VMap) {
43   return CloneModule(M, VMap, [](const GlobalValue *GV) { return true; });
44 }
45 
46 std::unique_ptr<Module> llvm::CloneModule(
47     const Module &M, ValueToValueMapTy &VMap,
48     function_ref<bool(const GlobalValue *)> ShouldCloneDefinition) {
49   // First off, we need to create the new module.
50   std::unique_ptr<Module> New =
51       llvm::make_unique<Module>(M.getModuleIdentifier(), M.getContext());
52   New->setSourceFileName(M.getSourceFileName());
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 =
77         Function::Create(cast<FunctionType>(I.getValueType()), I.getLinkage(),
78                          I.getAddressSpace(), I.getName(), New.get());
79     NF->copyAttributesFrom(&I);
80     VMap[&I] = NF;
81   }
82 
83   // Loop over the aliases in the module
84   for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
85        I != E; ++I) {
86     if (!ShouldCloneDefinition(&*I)) {
87       // An alias cannot act as an external reference, so we need to create
88       // either a function or a global variable depending on the value type.
89       // FIXME: Once pointee types are gone we can probably pick one or the
90       // other.
91       GlobalValue *GV;
92       if (I->getValueType()->isFunctionTy())
93         GV = Function::Create(cast<FunctionType>(I->getValueType()),
94                               GlobalValue::ExternalLinkage,
95                               I->getAddressSpace(), I->getName(), New.get());
96       else
97         GV = new GlobalVariable(
98             *New, I->getValueType(), false, GlobalValue::ExternalLinkage,
99             nullptr, I->getName(), nullptr,
100             I->getThreadLocalMode(), I->getType()->getAddressSpace());
101       VMap[&*I] = GV;
102       // We do not copy attributes (mainly because copying between different
103       // kinds of globals is forbidden), but this is generally not required for
104       // correctness.
105       continue;
106     }
107     auto *GA = GlobalAlias::create(I->getValueType(),
108                                    I->getType()->getPointerAddressSpace(),
109                                    I->getLinkage(), I->getName(), New.get());
110     GA->copyAttributesFrom(&*I);
111     VMap[&*I] = GA;
112   }
113 
114   // Now that all of the things that global variable initializer can refer to
115   // have been created, loop through and copy the global variable referrers
116   // over...  We also set the attributes on the global now.
117   //
118   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
119        I != E; ++I) {
120     if (I->isDeclaration())
121       continue;
122 
123     GlobalVariable *GV = cast<GlobalVariable>(VMap[&*I]);
124     if (!ShouldCloneDefinition(&*I)) {
125       // Skip after setting the correct linkage for an external reference.
126       GV->setLinkage(GlobalValue::ExternalLinkage);
127       continue;
128     }
129     if (I->hasInitializer())
130       GV->setInitializer(MapValue(I->getInitializer(), VMap));
131 
132     SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
133     I->getAllMetadata(MDs);
134     for (auto MD : MDs)
135       GV->addMetadata(MD.first,
136                       *MapMetadata(MD.second, VMap, RF_MoveDistinctMDs));
137 
138     copyComdat(GV, &*I);
139   }
140 
141   // Similarly, copy over function bodies now...
142   //
143   for (const Function &I : M) {
144     if (I.isDeclaration())
145       continue;
146 
147     Function *F = cast<Function>(VMap[&I]);
148     if (!ShouldCloneDefinition(&I)) {
149       // Skip after setting the correct linkage for an external reference.
150       F->setLinkage(GlobalValue::ExternalLinkage);
151       // Personality function is not valid on a declaration.
152       F->setPersonalityFn(nullptr);
153       continue;
154     }
155 
156     Function::arg_iterator DestI = F->arg_begin();
157     for (Function::const_arg_iterator J = I.arg_begin(); J != I.arg_end();
158          ++J) {
159       DestI->setName(J->getName());
160       VMap[&*J] = &*DestI++;
161     }
162 
163     SmallVector<ReturnInst *, 8> Returns; // Ignore returns cloned.
164     CloneFunctionInto(F, &I, VMap, /*ModuleLevelChanges=*/true, Returns);
165 
166     if (I.hasPersonalityFn())
167       F->setPersonalityFn(MapValue(I.getPersonalityFn(), VMap));
168 
169     copyComdat(F, &I);
170   }
171 
172   // And aliases
173   for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
174        I != E; ++I) {
175     // We already dealt with undefined aliases above.
176     if (!ShouldCloneDefinition(&*I))
177       continue;
178     GlobalAlias *GA = cast<GlobalAlias>(VMap[&*I]);
179     if (const Constant *C = I->getAliasee())
180       GA->setAliasee(MapValue(C, VMap));
181   }
182 
183   // And named metadata....
184   for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
185                                              E = M.named_metadata_end();
186        I != E; ++I) {
187     const NamedMDNode &NMD = *I;
188     NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
189     for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
190       NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
191   }
192 
193   return New;
194 }
195 
196 extern "C" {
197 
198 LLVMModuleRef LLVMCloneModule(LLVMModuleRef M) {
199   return wrap(CloneModule(*unwrap(M)).release());
200 }
201 
202 }
203