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"
19using namespace llvm;
20
21static 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///
34std::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
41std::unique_ptr<Module> llvm::CloneModule(const Module &M,
42                                          ValueToValueMapTy &VMap) {
43  return CloneModule(M, VMap, [](const GlobalValue *GV) { return true; });
44}
45
46std::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 (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  const auto* LLVM_DBG_CU = M.getNamedMetadata("llvm.dbg.cu");
185  for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
186                                             E = M.named_metadata_end();
187       I != E; ++I) {
188    const NamedMDNode &NMD = *I;
189    NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
190    if (&NMD == LLVM_DBG_CU) {
191      // Do not insert duplicate operands.
192      SmallPtrSet<const void*, 8> Visited;
193      for (const auto* Operand : NewNMD->operands())
194        Visited.insert(Operand);
195      for (const auto* Operand : NMD.operands()) {
196        auto* MappedOperand = MapMetadata(Operand, VMap);
197        if (Visited.insert(MappedOperand).second)
198          NewNMD->addOperand(MappedOperand);
199      }
200    } else
201      for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
202        NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
203  }
204
205  return New;
206}
207
208extern "C" {
209
210LLVMModuleRef LLVMCloneModule(LLVMModuleRef M) {
211  return wrap(CloneModule(*unwrap(M)).release());
212}
213
214}
215