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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/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/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/TargetParser/Triple.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());
setThreadLocalMode(Src->getThreadLocalMode());
setDLLStorageClass(Src->getDLLStorageClass());
setDSOLocal(Src->isDSOLocal());
setPartition(Src->getPartition());
if (Src->hasSanitizerMetadata())
setSanitizerMetadata(Src->getSanitizerMetadata());
else
removeSanitizerMetadata();
}
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");
}
GlobalObject::~GlobalObject() { setComdat(nullptr); }
bool GlobalValue::isInterposable() const {
if (isInterposableLinkage(getLinkage()))
return true;
return getParent() && getParent()->getSemanticInterposition() &&
!isDSOLocal();
}
bool GlobalValue::canBenefitFromLocalAlias() const {
// See AsmPrinter::getSymbolPreferLocal(). For a deduplicate comdat kind,
// references to a discarded local symbol from outside the group are not
// allowed, so avoid the local alias.
auto isDeduplicateComdat = [](const Comdat *C) {
return C && C->getSelectionKind() != Comdat::NoDeduplicate;
};
return hasDefaultVisibility() &&
GlobalObject::isExternalLinkage(getLinkage()) && !isDeclaration() &&
!isa<GlobalIFunc>(this) && !isDeduplicateComdat(getComdat());
}
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(getAlign() == Align && "Alignment representation error!");
}
void GlobalObject::setAlignment(Align Align) {
assert(Align <= MaximumAlignment &&
"Alignment is greater than MaximumAlignment!");
unsigned AlignmentData = encode(Align);
unsigned OldData = getGlobalValueSubClassData();
setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
assert(getAlign() && *getAlign() == Align &&
"Alignment representation error!");
}
void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
GlobalValue::copyAttributesFrom(Src);
setAlignment(Src->getAlign());
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.
Name.consume_front("\1");
std::string GlobalName;
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())
GlobalName += "<unknown>";
else
GlobalName += FileName;
GlobalName += kGlobalIdentifierDelimiter;
}
GlobalName += Name;
return GlobalName;
}
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->getAliaseeObject())
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->getAliaseeObject())
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::setComdat(Comdat *C) {
if (ObjComdat)
ObjComdat->removeUser(this);
ObjComdat = C;
if (C)
C->addUser(this);
}
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();
}
using SanitizerMetadata = GlobalValue::SanitizerMetadata;
const SanitizerMetadata &GlobalValue::getSanitizerMetadata() const {
assert(hasSanitizerMetadata());
assert(getContext().pImpl->GlobalValueSanitizerMetadata.count(this));
return getContext().pImpl->GlobalValueSanitizerMetadata[this];
}
void GlobalValue::setSanitizerMetadata(SanitizerMetadata Meta) {
getContext().pImpl->GlobalValueSanitizerMetadata[this] = Meta;
HasSanitizerMetadata = true;
}
void GlobalValue::removeSanitizerMetadata() {
DenseMap<const GlobalValue *, SanitizerMetadata> &MetadataMap =
getContext().pImpl->GlobalValueSanitizerMetadata;
MetadataMap.erase(this);
HasSanitizerMetadata = false;
}
void GlobalValue::setNoSanitizeMetadata() {
SanitizerMetadata Meta;
Meta.NoAddress = true;
Meta.NoHWAddress = true;
setSanitizerMetadata(Meta);
}
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::isNobuiltinFnDef() const {
const Function *F = dyn_cast<Function>(this);
if (!F || F->empty())
return false;
return F->hasFnAttribute(Attribute::NoBuiltin);
}
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<GlobalAlias>(this) || isa<GlobalIFunc>(this));
return false;
}
bool GlobalObject::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() && getAlign())
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;
}
template <typename Operation>
static const GlobalObject *
findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases,
const Operation &Op) {
if (auto *GO = dyn_cast<GlobalObject>(C)) {
Op(*GO);
return GO;
}
if (auto *GA = dyn_cast<GlobalAlias>(C)) {
Op(*GA);
if (Aliases.insert(GA).second)
return findBaseObject(GA->getOperand(0), Aliases, Op);
}
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
switch (CE->getOpcode()) {
case Instruction::Add: {
auto *LHS = findBaseObject(CE->getOperand(0), Aliases, Op);
auto *RHS = findBaseObject(CE->getOperand(1), Aliases, Op);
if (LHS && RHS)
return nullptr;
return LHS ? LHS : RHS;
}
case Instruction::Sub: {
if (findBaseObject(CE->getOperand(1), Aliases, Op))
return nullptr;
return findBaseObject(CE->getOperand(0), Aliases, Op);
}
case Instruction::IntToPtr:
case Instruction::PtrToInt:
case Instruction::BitCast:
case Instruction::GetElementPtr:
return findBaseObject(CE->getOperand(0), Aliases, Op);
default:
break;
}
}
return nullptr;
}
const GlobalObject *GlobalValue::getAliaseeObject() const {
DenseSet<const GlobalAlias *> Aliases;
return findBaseObject(this, Aliases, [](const GlobalValue &) {});
}
bool GlobalValue::isAbsoluteSymbolRef() const {
auto *GO = dyn_cast<GlobalObject>(this);
if (!GO)
return false;
return GO->getMetadata(LLVMContext::MD_absolute_symbol);
}
std::optional<ConstantRange> GlobalValue::getAbsoluteSymbolRange() const {
auto *GO = dyn_cast<GlobalObject>(this);
if (!GO)
return std::nullopt;
MDNode *MD = GO->getMetadata(LLVMContext::MD_absolute_symbol);
if (!MD)
return std::nullopt;
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,
std::optional<unsigned> AddressSpace,
bool isExternallyInitialized)
: GlobalVariable(Ty, constant, Link, InitVal, Name, TLMode,
AddressSpace
? *AddressSpace
: M.getDataLayout().getDefaultGlobalsAddressSpace(),
isExternallyInitialized) {
if (Before)
Before->getParent()->insertGlobalVariable(Before->getIterator(), this);
else
M.insertGlobalVariable(this);
}
void GlobalVariable::removeFromParent() {
getParent()->removeGlobalVariable(this);
}
void GlobalVariable::eraseFromParent() {
getParent()->eraseGlobalVariable(this);
}
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);
setExternallyInitialized(Src->isExternallyInitialized());
setAttributes(Src->getAttributes());
if (auto CM = Src->getCodeModel())
setCodeModel(*CM);
}
void GlobalVariable::dropAllReferences() {
User::dropAllReferences();
clearMetadata();
}
void GlobalVariable::setCodeModel(CodeModel::Model CM) {
unsigned CodeModelData = static_cast<unsigned>(CM) + 1;
unsigned OldData = getGlobalValueSubClassData();
unsigned NewData = (OldData & ~(CodeModelMask << CodeModelShift)) |
(CodeModelData << CodeModelShift);
setGlobalValueSubClassData(NewData);
assert(getCodeModel() == CM && "Code model representation error!");
}
//===----------------------------------------------------------------------===//
// GlobalAlias Implementation
//===----------------------------------------------------------------------===//
GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
const Twine &Name, Constant *Aliasee,
Module *ParentModule)
: GlobalValue(Ty, Value::GlobalAliasVal, &Op<0>(), 1, Link, Name,
AddressSpace) {
setAliasee(Aliasee);
if (ParentModule)
ParentModule->insertAlias(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) {
return create(Aliasee->getValueType(), Aliasee->getAddressSpace(), Link, Name,
Aliasee);
}
GlobalAlias *GlobalAlias::create(const Twine &Name, GlobalValue *Aliasee) {
return create(Aliasee->getLinkage(), Name, Aliasee);
}
void GlobalAlias::removeFromParent() { getParent()->removeAlias(this); }
void GlobalAlias::eraseFromParent() { getParent()->eraseAlias(this); }
void GlobalAlias::setAliasee(Constant *Aliasee) {
assert((!Aliasee || Aliasee->getType() == getType()) &&
"Alias and aliasee types should match!");
Op<0>().set(Aliasee);
}
const GlobalObject *GlobalAlias::getAliaseeObject() const {
DenseSet<const GlobalAlias *> Aliases;
return findBaseObject(getOperand(0), Aliases, [](const GlobalValue &) {});
}
//===----------------------------------------------------------------------===//
// GlobalIFunc Implementation
//===----------------------------------------------------------------------===//
GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
const Twine &Name, Constant *Resolver,
Module *ParentModule)
: GlobalObject(Ty, Value::GlobalIFuncVal, &Op<0>(), 1, Link, Name,
AddressSpace) {
setResolver(Resolver);
if (ParentModule)
ParentModule->insertIFunc(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()->removeIFunc(this); }
void GlobalIFunc::eraseFromParent() { getParent()->eraseIFunc(this); }
const Function *GlobalIFunc::getResolverFunction() const {
return dyn_cast<Function>(getResolver()->stripPointerCastsAndAliases());
}
void GlobalIFunc::applyAlongResolverPath(
function_ref<void(const GlobalValue &)> Op) const {
DenseSet<const GlobalAlias *> Aliases;
findBaseObject(getResolver(), Aliases, Op);
}