lib/IR/Globals.cpp - llvm - Git at Google

 //===-- 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 "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());
 }

 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) {
   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!");
 }

 void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
   GlobalValue::copyAttributesFrom(Src);
   setAlignment(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 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->SectionStrings.insert(S).first->first();
   }
   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;
 }


 //===----------------------------------------------------------------------===//
 // 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());
 }
	//===-- 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 "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());
	}

	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) {
	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!");
	}

	void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
	GlobalValue::copyAttributesFrom(Src);
	setAlignment(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 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->SectionStrings.insert(S).first->first();
	}
	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;
	}


	//===----------------------------------------------------------------------===//
	// 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());
	}