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+//===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the GlobalValue & GlobalVariable classes for the IR
+// library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LLVMContextImpl.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/ConstantRange.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/Error.h"
+#include "llvm/Support/ErrorHandling.h"
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// GlobalValue Class
+//===----------------------------------------------------------------------===//
+
+// GlobalValue should be a Constant, plus a type, a module, some flags, and an
+// intrinsic ID. Add an assert to prevent people from accidentally growing
+// GlobalValue while adding flags.
+static_assert(sizeof(GlobalValue) ==
+ sizeof(Constant) + 2 * sizeof(void *) + 2 * sizeof(unsigned),
+ "unexpected GlobalValue size growth");
+
+// GlobalObject adds a comdat.
+static_assert(sizeof(GlobalObject) == sizeof(GlobalValue) + sizeof(void *),
+ "unexpected GlobalObject size growth");
+
+bool GlobalValue::isMaterializable() const {
+ if (const Function *F = dyn_cast<Function>(this))
+ return F->isMaterializable();
+ return false;
+}
+Error 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());
+ setDSOLocal(Src->isDSOLocal());
+ setPartition(Src->getPartition());
+}
+
+void GlobalValue::removeFromParent() {
+ switch (getValueID()) {
+#define HANDLE_GLOBAL_VALUE(NAME) \
+ case Value::NAME##Val: \
+ return static_cast<NAME *>(this)->removeFromParent();
+#include "llvm/IR/Value.def"
+ default:
+ break;
+ }
+ llvm_unreachable("not a global");
+}
+
+void GlobalValue::eraseFromParent() {
+ switch (getValueID()) {
+#define HANDLE_GLOBAL_VALUE(NAME) \
+ case Value::NAME##Val: \
+ return static_cast<NAME *>(this)->eraseFromParent();
+#include "llvm/IR/Value.def"
+ default:
+ break;
+ }
+ llvm_unreachable("not a global");
+}
+
+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();
+}
+
+unsigned GlobalValue::getAddressSpace() const {
+ PointerType *PtrTy = getType();
+ return PtrTy->getAddressSpace();
+}
+
+void GlobalObject::setAlignment(unsigned Align) {
+ setAlignment(MaybeAlign(Align));
+}
+
+void GlobalObject::setAlignment(MaybeAlign Align) {
+ assert((!Align || Align <= MaximumAlignment) &&
+ "Alignment is greater than MaximumAlignment!");
+ unsigned AlignmentData = encode(Align);
+ unsigned OldData = getGlobalValueSubClassData();
+ setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
+ assert(MaybeAlign(getAlignment()) == Align &&
+ "Alignment representation error!");
+}
+
+void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
+ GlobalValue::copyAttributesFrom(Src);
+ setAlignment(MaybeAlign(Src->getAlignment()));
+ setSection(Src->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();
+}
+
+const Comdat *GlobalValue::getComdat() 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 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();
+}
+
+StringRef GlobalValue::getPartition() const {
+ if (!hasPartition())
+ return "";
+ return getContext().pImpl->GlobalValuePartitions[this];
+}
+
+void GlobalValue::setPartition(StringRef S) {
+ // Do nothing if we're clearing the partition and it is already empty.
+ if (!hasPartition() && S.empty())
+ return;
+
+ // Get or create a stable partition name string and put it in the table in the
+ // context.
+ if (!S.empty())
+ S = getContext().pImpl->Saver.save(S);
+ getContext().pImpl->GlobalValuePartitions[this] = S;
+
+ // Update the HasPartition field. Setting the partition to the empty string
+ // means this global no longer has a partition.
+ HasPartition = !S.empty();
+}
+
+StringRef GlobalObject::getSectionImpl() const {
+ assert(hasSection());
+ return getContext().pImpl->GlobalObjectSections[this];
+}
+
+void GlobalObject::setSection(StringRef S) {
+ // Do nothing if we're clearing the section and it is already empty.
+ if (!hasSection() && S.empty())
+ return;
+
+ // Get or create a stable section name string and put it in the table in the
+ // context.
+ if (!S.empty())
+ S = getContext().pImpl->Saver.save(S);
+ getContext().pImpl->GlobalObjectSections[this] = S;
+
+ // Update the HasSectionHashEntryBit. Setting the section to the empty string
+ // means this global no longer has a section.
+ setGlobalObjectFlag(HasSectionHashEntryBit, !S.empty());
+}
+
+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 && !isDSOLocal())
+ return false;
+
+ return true;
+}
+
+const GlobalObject *GlobalValue::getBaseObject() const {
+ if (auto *GO = dyn_cast<GlobalObject>(this))
+ return GO;
+ if (auto *GA = dyn_cast<GlobalIndirectSymbol>(this))
+ return GA->getBaseObject();
+ return nullptr;
+}
+
+bool GlobalValue::isAbsoluteSymbolRef() const {
+ auto *GO = dyn_cast<GlobalObject>(this);
+ if (!GO)
+ return false;
+
+ return GO->getMetadata(LLVMContext::MD_absolute_symbol);
+}
+
+Optional<ConstantRange> GlobalValue::getAbsoluteSymbolRange() const {
+ auto *GO = dyn_cast<GlobalObject>(this);
+ if (!GO)
+ return None;
+
+ MDNode *MD = GO->getMetadata(LLVMContext::MD_absolute_symbol);
+ if (!MD)
+ return None;
+
+ return getConstantRangeFromMetadata(*MD);
+}
+
+bool GlobalValue::canBeOmittedFromSymbolTable() const {
+ if (!hasLinkOnceODRLinkage())
+ return false;
+
+ // We assume that anyone who sets global unnamed_addr on a non-constant
+ // knows what they're doing.
+ if (hasGlobalUnnamedAddr())
+ return true;
+
+ // If it is a non constant variable, it needs to be uniqued across shared
+ // objects.
+ if (auto *Var = dyn_cast<GlobalVariable>(this))
+ if (!Var->isConstant())
+ return false;
+
+ return hasAtLeastLocalUnnamedAddr();
+}
+
+//===----------------------------------------------------------------------===//
+// 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) {
+ assert(!Ty->isFunctionTy() && PointerType::isValidElementType(Ty) &&
+ "invalid type for global variable");
+ 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) {
+ assert(!Ty->isFunctionTy() && PointerType::isValidElementType(Ty) &&
+ "invalid type for global variable");
+ 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::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 GlobalVariable *Src) {
+ GlobalObject::copyAttributesFrom(Src);
+ setThreadLocalMode(Src->getThreadLocalMode());
+ setExternallyInitialized(Src->isExternallyInitialized());
+ setAttributes(Src->getAttributes());
+}
+
+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;
+}
+
+static const GlobalObject *
+findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
+ if (auto *GO = dyn_cast<GlobalObject>(C))
+ return GO;
+ if (auto *GA = dyn_cast<GlobalAlias>(C))
+ if (Aliases.insert(GA).second)
+ return findBaseObject(GA->getOperand(0), Aliases);
+ if (auto *CE = dyn_cast<ConstantExpr>(C)) {
+ switch (CE->getOpcode()) {
+ case Instruction::Add: {
+ auto *LHS = findBaseObject(CE->getOperand(0), Aliases);
+ auto *RHS = findBaseObject(CE->getOperand(1), Aliases);
+ if (LHS && RHS)
+ return nullptr;
+ return LHS ? LHS : RHS;
+ }
+ case Instruction::Sub: {
+ if (findBaseObject(CE->getOperand(1), Aliases))
+ return nullptr;
+ return findBaseObject(CE->getOperand(0), Aliases);
+ }
+ case Instruction::IntToPtr:
+ case Instruction::PtrToInt:
+ case Instruction::BitCast:
+ case Instruction::GetElementPtr:
+ return findBaseObject(CE->getOperand(0), Aliases);
+ default:
+ break;
+ }
+ }
+ return nullptr;
+}
+
+const GlobalObject *GlobalIndirectSymbol::getBaseObject() const {
+ DenseSet<const GlobalAlias *> Aliases;
+ return findBaseObject(getOperand(0), Aliases);
+}
+
+//===----------------------------------------------------------------------===//
+// 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::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::removeFromParent() {
+ getParent()->getIFuncList().remove(getIterator());
+}
+
+void GlobalIFunc::eraseFromParent() {
+ getParent()->getIFuncList().erase(getIterator());
+}
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