//===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the GlobalValue & GlobalVariable classes for the IR // library. // //===----------------------------------------------------------------------===// #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/Triple.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DerivedTypes.h" #include "llvm/IR/GlobalAlias.h" #include "llvm/IR/GlobalValue.h" #include "llvm/IR/GlobalVariable.h" #include "llvm/IR/Module.h" #include "llvm/IR/Operator.h" #include "llvm/Support/ErrorHandling.h" using namespace llvm; //===----------------------------------------------------------------------===// // GlobalValue Class //===----------------------------------------------------------------------===// bool GlobalValue::isMaterializable() const { if (const Function *F = dyn_cast<Function>(this)) return F->isMaterializable(); return false; } std::error_code GlobalValue::materialize() { return getParent()->materialize(this); } /// Override destroyConstantImpl to make sure it doesn't get called on /// GlobalValue's because they shouldn't be treated like other constants. void GlobalValue::destroyConstantImpl() { llvm_unreachable("You can't GV->destroyConstantImpl()!"); } Value *GlobalValue::handleOperandChangeImpl(Value *From, Value *To) { llvm_unreachable("Unsupported class for handleOperandChange()!"); } /// copyAttributesFrom - copy all additional attributes (those not needed to /// create a GlobalValue) from the GlobalValue Src to this one. void GlobalValue::copyAttributesFrom(const GlobalValue *Src) { setVisibility(Src->getVisibility()); setUnnamedAddr(Src->getUnnamedAddr()); setDLLStorageClass(Src->getDLLStorageClass()); } unsigned GlobalValue::getAlignment() const { if (auto *GA = dyn_cast<GlobalAlias>(this)) { // In general we cannot compute this at the IR level, but we try. if (const GlobalObject *GO = GA->getBaseObject()) return GO->getAlignment(); // FIXME: we should also be able to handle: // Alias = Global + Offset // Alias = Absolute return 0; } return cast<GlobalObject>(this)->getAlignment(); } void GlobalObject::setAlignment(unsigned Align) { assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!"); assert(Align <= MaximumAlignment && "Alignment is greater than MaximumAlignment!"); unsigned AlignmentData = Log2_32(Align) + 1; unsigned OldData = getGlobalValueSubClassData(); setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData); assert(getAlignment() == Align && "Alignment representation error!"); } unsigned GlobalObject::getGlobalObjectSubClassData() const { unsigned ValueData = getGlobalValueSubClassData(); return ValueData >> GlobalObjectBits; } void GlobalObject::setGlobalObjectSubClassData(unsigned Val) { unsigned OldData = getGlobalValueSubClassData(); setGlobalValueSubClassData((OldData & GlobalObjectMask) | (Val << GlobalObjectBits)); assert(getGlobalObjectSubClassData() == Val && "representation error"); } void GlobalObject::copyAttributesFrom(const GlobalValue *Src) { GlobalValue::copyAttributesFrom(Src); if (const auto *GV = dyn_cast<GlobalObject>(Src)) { setAlignment(GV->getAlignment()); setSection(GV->getSection()); } } std::string GlobalValue::getGlobalIdentifier(StringRef Name, GlobalValue::LinkageTypes Linkage, StringRef FileName) { // Value names may be prefixed with a binary '1' to indicate // that the backend should not modify the symbols due to any platform // naming convention. Do not include that '1' in the PGO profile name. if (Name[0] == '\1') Name = Name.substr(1); std::string NewName = Name; if (llvm::GlobalValue::isLocalLinkage(Linkage)) { // For local symbols, prepend the main file name to distinguish them. // Do not include the full path in the file name since there's no guarantee // that it will stay the same, e.g., if the files are checked out from // version control in different locations. if (FileName.empty()) NewName = NewName.insert(0, "<unknown>:"); else NewName = NewName.insert(0, FileName.str() + ":"); } return NewName; } std::string GlobalValue::getGlobalIdentifier() const { return getGlobalIdentifier(getName(), getLinkage(), getParent()->getSourceFileName()); } StringRef GlobalValue::getSection() const { if (auto *GA = dyn_cast<GlobalAlias>(this)) { // In general we cannot compute this at the IR level, but we try. if (const GlobalObject *GO = GA->getBaseObject()) return GO->getSection(); return ""; } return cast<GlobalObject>(this)->getSection(); } Comdat *GlobalValue::getComdat() { if (auto *GA = dyn_cast<GlobalAlias>(this)) { // In general we cannot compute this at the IR level, but we try. if (const GlobalObject *GO = GA->getBaseObject()) return const_cast<GlobalObject *>(GO)->getComdat(); return nullptr; } // ifunc and its resolver are separate things so don't use resolver comdat. if (isa<GlobalIFunc>(this)) return nullptr; return cast<GlobalObject>(this)->getComdat(); } void GlobalObject::setSection(StringRef S) { Section = S; // The C api requires this to be null terminated. Section.c_str(); } bool GlobalValue::isDeclaration() const { // Globals are definitions if they have an initializer. if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this)) return GV->getNumOperands() == 0; // Functions are definitions if they have a body. if (const Function *F = dyn_cast<Function>(this)) return F->empty() && !F->isMaterializable(); // Aliases and ifuncs are always definitions. assert(isa<GlobalIndirectSymbol>(this)); return false; } bool GlobalValue::canIncreaseAlignment() const { // Firstly, can only increase the alignment of a global if it // is a strong definition. if (!isStrongDefinitionForLinker()) return false; // It also has to either not have a section defined, or, not have // alignment specified. (If it is assigned a section, the global // could be densely packed with other objects in the section, and // increasing the alignment could cause padding issues.) if (hasSection() && getAlignment() > 0) return false; // On ELF platforms, we're further restricted in that we can't // increase the alignment of any variable which might be emitted // into a shared library, and which is exported. If the main // executable accesses a variable found in a shared-lib, the main // exe actually allocates memory for and exports the symbol ITSELF, // overriding the symbol found in the library. That is, at link // time, the observed alignment of the variable is copied into the // executable binary. (A COPY relocation is also generated, to copy // the initial data from the shadowed variable in the shared-lib // into the location in the main binary, before running code.) // // And thus, even though you might think you are defining the // global, and allocating the memory for the global in your object // file, and thus should be able to set the alignment arbitrarily, // that's not actually true. Doing so can cause an ABI breakage; an // executable might have already been built with the previous // alignment of the variable, and then assuming an increased // alignment will be incorrect. // Conservatively assume ELF if there's no parent pointer. bool isELF = (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatELF()); if (isELF && hasDefaultVisibility() && !hasLocalLinkage()) return false; return true; } //===----------------------------------------------------------------------===// // GlobalVariable Implementation //===----------------------------------------------------------------------===// GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link, Constant *InitVal, const Twine &Name, ThreadLocalMode TLMode, unsigned AddressSpace, bool isExternallyInitialized) : GlobalObject(Ty, Value::GlobalVariableVal, OperandTraits<GlobalVariable>::op_begin(this), InitVal != nullptr, Link, Name, AddressSpace), isConstantGlobal(constant), isExternallyInitializedConstant(isExternallyInitialized) { setThreadLocalMode(TLMode); if (InitVal) { assert(InitVal->getType() == Ty && "Initializer should be the same type as the GlobalVariable!"); Op<0>() = InitVal; } } GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant, LinkageTypes Link, Constant *InitVal, const Twine &Name, GlobalVariable *Before, ThreadLocalMode TLMode, unsigned AddressSpace, bool isExternallyInitialized) : GlobalObject(Ty, Value::GlobalVariableVal, OperandTraits<GlobalVariable>::op_begin(this), InitVal != nullptr, Link, Name, AddressSpace), isConstantGlobal(constant), isExternallyInitializedConstant(isExternallyInitialized) { setThreadLocalMode(TLMode); if (InitVal) { assert(InitVal->getType() == Ty && "Initializer should be the same type as the GlobalVariable!"); Op<0>() = InitVal; } if (Before) Before->getParent()->getGlobalList().insert(Before->getIterator(), this); else M.getGlobalList().push_back(this); } void GlobalVariable::setParent(Module *parent) { Parent = parent; } void GlobalVariable::removeFromParent() { getParent()->getGlobalList().remove(getIterator()); } void GlobalVariable::eraseFromParent() { getParent()->getGlobalList().erase(getIterator()); } void GlobalVariable::setInitializer(Constant *InitVal) { if (!InitVal) { if (hasInitializer()) { // Note, the num operands is used to compute the offset of the operand, so // the order here matters. Clearing the operand then clearing the num // operands ensures we have the correct offset to the operand. Op<0>().set(nullptr); setGlobalVariableNumOperands(0); } } else { assert(InitVal->getType() == getValueType() && "Initializer type must match GlobalVariable type"); // Note, the num operands is used to compute the offset of the operand, so // the order here matters. We need to set num operands to 1 first so that // we get the correct offset to the first operand when we set it. if (!hasInitializer()) setGlobalVariableNumOperands(1); Op<0>().set(InitVal); } } /// Copy all additional attributes (those not needed to create a GlobalVariable) /// from the GlobalVariable Src to this one. void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) { GlobalObject::copyAttributesFrom(Src); if (const GlobalVariable *SrcVar = dyn_cast<GlobalVariable>(Src)) { setThreadLocalMode(SrcVar->getThreadLocalMode()); setExternallyInitialized(SrcVar->isExternallyInitialized()); } } void GlobalVariable::dropAllReferences() { User::dropAllReferences(); clearMetadata(); } //===----------------------------------------------------------------------===// // GlobalIndirectSymbol Implementation //===----------------------------------------------------------------------===// GlobalIndirectSymbol::GlobalIndirectSymbol(Type *Ty, ValueTy VTy, unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name, Constant *Symbol) : GlobalValue(Ty, VTy, &Op<0>(), 1, Linkage, Name, AddressSpace) { Op<0>() = Symbol; } //===----------------------------------------------------------------------===// // GlobalAlias Implementation //===----------------------------------------------------------------------===// GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link, const Twine &Name, Constant *Aliasee, Module *ParentModule) : GlobalIndirectSymbol(Ty, Value::GlobalAliasVal, AddressSpace, Link, Name, Aliasee) { if (ParentModule) ParentModule->getAliasList().push_back(this); } GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, LinkageTypes Link, const Twine &Name, Constant *Aliasee, Module *ParentModule) { return new GlobalAlias(Ty, AddressSpace, Link, Name, Aliasee, ParentModule); } GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name, Module *Parent) { return create(Ty, AddressSpace, Linkage, Name, nullptr, Parent); } GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name, GlobalValue *Aliasee) { return create(Ty, AddressSpace, Linkage, Name, Aliasee, Aliasee->getParent()); } GlobalAlias *GlobalAlias::create(LinkageTypes Link, const Twine &Name, GlobalValue *Aliasee) { PointerType *PTy = Aliasee->getType(); return create(PTy->getElementType(), PTy->getAddressSpace(), Link, Name, Aliasee); } GlobalAlias *GlobalAlias::create(const Twine &Name, GlobalValue *Aliasee) { return create(Aliasee->getLinkage(), Name, Aliasee); } void GlobalAlias::setParent(Module *parent) { Parent = parent; } void GlobalAlias::removeFromParent() { getParent()->getAliasList().remove(getIterator()); } void GlobalAlias::eraseFromParent() { getParent()->getAliasList().erase(getIterator()); } void GlobalAlias::setAliasee(Constant *Aliasee) { assert((!Aliasee || Aliasee->getType() == getType()) && "Alias and aliasee types should match!"); setIndirectSymbol(Aliasee); } //===----------------------------------------------------------------------===// // GlobalIFunc Implementation //===----------------------------------------------------------------------===// GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link, const Twine &Name, Constant *Resolver, Module *ParentModule) : GlobalIndirectSymbol(Ty, Value::GlobalIFuncVal, AddressSpace, Link, Name, Resolver) { if (ParentModule) ParentModule->getIFuncList().push_back(this); } GlobalIFunc *GlobalIFunc::create(Type *Ty, unsigned AddressSpace, LinkageTypes Link, const Twine &Name, Constant *Resolver, Module *ParentModule) { return new GlobalIFunc(Ty, AddressSpace, Link, Name, Resolver, ParentModule); } void GlobalIFunc::setParent(Module *parent) { Parent = parent; } void GlobalIFunc::removeFromParent() { getParent()->getIFuncList().remove(getIterator()); } void GlobalIFunc::eraseFromParent() { getParent()->getIFuncList().erase(getIterator()); }