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