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       std::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 (const GlobalVariable &G : M.globals()) {
119     GlobalVariable *GV = cast<GlobalVariable>(VMap[&G]);
120 
121     SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
122     G.getAllMetadata(MDs);
123 
124     // FIXME: Stop using RF_ReuseAndMutateDistinctMDs here, since it's unsound
125     // to mutate metadata that is still referenced by the source module unless
126     // the source is about to be discarded (see IRMover for a valid use).
127     for (auto MD : MDs)
128       GV->addMetadata(MD.first, *MapMetadata(MD.second, VMap,
129                                              RF_ReuseAndMutateDistinctMDs));
130 
131     if (G.isDeclaration())
132       continue;
133 
134     if (!ShouldCloneDefinition(&G)) {
135       // Skip after setting the correct linkage for an external reference.
136       GV->setLinkage(GlobalValue::ExternalLinkage);
137       continue;
138     }
139     if (G.hasInitializer())
140       GV->setInitializer(MapValue(G.getInitializer(), VMap));
141 
142     copyComdat(GV, &G);
143   }
144 
145   // Similarly, copy over function bodies now...
146   //
147   for (const Function &I : M) {
148     if (I.isDeclaration())
149       continue;
150 
151     Function *F = cast<Function>(VMap[&I]);
152     if (!ShouldCloneDefinition(&I)) {
153       // Skip after setting the correct linkage for an external reference.
154       F->setLinkage(GlobalValue::ExternalLinkage);
155       // Personality function is not valid on a declaration.
156       F->setPersonalityFn(nullptr);
157       continue;
158     }
159 
160     Function::arg_iterator DestI = F->arg_begin();
161     for (Function::const_arg_iterator J = I.arg_begin(); J != I.arg_end();
162          ++J) {
163       DestI->setName(J->getName());
164       VMap[&*J] = &*DestI++;
165     }
166 
167     SmallVector<ReturnInst *, 8> Returns; // Ignore returns cloned.
168     CloneFunctionInto(F, &I, VMap, /*ModuleLevelChanges=*/true, Returns);
169 
170     if (I.hasPersonalityFn())
171       F->setPersonalityFn(MapValue(I.getPersonalityFn(), VMap));
172 
173     copyComdat(F, &I);
174   }
175 
176   // And aliases
177   for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
178        I != E; ++I) {
179     // We already dealt with undefined aliases above.
180     if (!ShouldCloneDefinition(&*I))
181       continue;
182     GlobalAlias *GA = cast<GlobalAlias>(VMap[&*I]);
183     if (const Constant *C = I->getAliasee())
184       GA->setAliasee(MapValue(C, VMap));
185   }
186 
187   // And named metadata....
188   const auto* LLVM_DBG_CU = M.getNamedMetadata("llvm.dbg.cu");
189   for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
190                                              E = M.named_metadata_end();
191        I != E; ++I) {
192     const NamedMDNode &NMD = *I;
193     NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
194     if (&NMD == LLVM_DBG_CU) {
195       // Do not insert duplicate operands.
196       SmallPtrSet<const void*, 8> Visited;
197       for (const auto* Operand : NewNMD->operands())
198         Visited.insert(Operand);
199       for (const auto* Operand : NMD.operands()) {
200         auto* MappedOperand = MapMetadata(Operand, VMap);
201         if (Visited.insert(MappedOperand).second)
202           NewNMD->addOperand(MappedOperand);
203       }
204     } else
205       for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
206         NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
207   }
208 
209   return New;
210 }
211 
212 extern "C" {
213 
214 LLVMModuleRef LLVMCloneModule(LLVMModuleRef M) {
215   return wrap(CloneModule(*unwrap(M)).release());
216 }
217 
218 }
219