lib/Transforms/Utils/CloneModule.cpp

   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 (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
 208 extern "C" {
 209
 210 LLVMModuleRef LLVMCloneModule(LLVMModuleRef M) {
 211   return wrap(CloneModule(*unwrap(M)).release());
 212 }
 213
 214 }