1 //===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file implements the GlobalValue & GlobalVariable classes for the IR
12 //===----------------------------------------------------------------------===//
14 #include "LLVMContextImpl.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/IR/ConstantRange.h"
18 #include "llvm/IR/Constants.h"
19 #include "llvm/IR/DerivedTypes.h"
20 #include "llvm/IR/GlobalAlias.h"
21 #include "llvm/IR/GlobalValue.h"
22 #include "llvm/IR/GlobalVariable.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/Operator.h"
25 #include "llvm/Support/Error.h"
26 #include "llvm/Support/ErrorHandling.h"
29 //===----------------------------------------------------------------------===//
31 //===----------------------------------------------------------------------===//
33 // GlobalValue should be a Constant, plus a type, a module, some flags, and an
34 // intrinsic ID. Add an assert to prevent people from accidentally growing
35 // GlobalValue while adding flags.
36 static_assert(sizeof(GlobalValue) ==
37 sizeof(Constant) + 2 * sizeof(void *) + 2 * sizeof(unsigned),
38 "unexpected GlobalValue size growth");
40 // GlobalObject adds a comdat.
41 static_assert(sizeof(GlobalObject) == sizeof(GlobalValue) + sizeof(void *),
42 "unexpected GlobalObject size growth");
44 bool GlobalValue::isMaterializable() const {
45 if (const Function *F = dyn_cast<Function>(this))
46 return F->isMaterializable();
49 Error GlobalValue::materialize() {
50 return getParent()->materialize(this);
53 /// Override destroyConstantImpl to make sure it doesn't get called on
54 /// GlobalValue's because they shouldn't be treated like other constants.
55 void GlobalValue::destroyConstantImpl() {
56 llvm_unreachable("You can't GV->destroyConstantImpl()!");
59 Value *GlobalValue::handleOperandChangeImpl(Value *From, Value *To) {
60 llvm_unreachable("Unsupported class for handleOperandChange()!");
63 /// copyAttributesFrom - copy all additional attributes (those not needed to
64 /// create a GlobalValue) from the GlobalValue Src to this one.
65 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
66 setVisibility(Src->getVisibility());
67 setUnnamedAddr(Src->getUnnamedAddr());
68 setThreadLocalMode(Src->getThreadLocalMode());
69 setDLLStorageClass(Src->getDLLStorageClass());
70 setDSOLocal(Src->isDSOLocal());
71 setPartition(Src->getPartition());
74 void GlobalValue::removeFromParent() {
75 switch (getValueID()) {
76 #define HANDLE_GLOBAL_VALUE(NAME) \
77 case Value::NAME##Val: \
78 return static_cast<NAME *>(this)->removeFromParent();
79 #include "llvm/IR/Value.def"
83 llvm_unreachable("not a global");
86 void GlobalValue::eraseFromParent() {
87 switch (getValueID()) {
88 #define HANDLE_GLOBAL_VALUE(NAME) \
89 case Value::NAME##Val: \
90 return static_cast<NAME *>(this)->eraseFromParent();
91 #include "llvm/IR/Value.def"
95 llvm_unreachable("not a global");
98 bool GlobalValue::isInterposable() const {
99 if (isInterposableLinkage(getLinkage()))
101 return getParent() && getParent()->getSemanticInterposition() &&
105 bool GlobalValue::canBenefitFromLocalAlias() const {
106 // See AsmPrinter::getSymbolPreferLocal().
107 return hasDefaultVisibility() &&
108 GlobalObject::isExternalLinkage(getLinkage()) && !isDeclaration() &&
109 !isa<GlobalIFunc>(this) && !hasComdat();
112 unsigned GlobalValue::getAddressSpace() const {
113 PointerType *PtrTy = getType();
114 return PtrTy->getAddressSpace();
117 void GlobalObject::setAlignment(MaybeAlign Align) {
118 assert((!Align || *Align <= MaximumAlignment) &&
119 "Alignment is greater than MaximumAlignment!");
120 unsigned AlignmentData = encode(Align);
121 unsigned OldData = getGlobalValueSubClassData();
122 setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
123 assert(MaybeAlign(getAlignment()) == Align &&
124 "Alignment representation error!");
127 void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
128 GlobalValue::copyAttributesFrom(Src);
129 setAlignment(MaybeAlign(Src->getAlignment()));
130 setSection(Src->getSection());
133 std::string GlobalValue::getGlobalIdentifier(StringRef Name,
134 GlobalValue::LinkageTypes Linkage,
135 StringRef FileName) {
137 // Value names may be prefixed with a binary '1' to indicate
138 // that the backend should not modify the symbols due to any platform
139 // naming convention. Do not include that '1' in the PGO profile name.
141 Name = Name.substr(1);
143 std::string NewName = std::string(Name);
144 if (llvm::GlobalValue::isLocalLinkage(Linkage)) {
145 // For local symbols, prepend the main file name to distinguish them.
146 // Do not include the full path in the file name since there's no guarantee
147 // that it will stay the same, e.g., if the files are checked out from
148 // version control in different locations.
149 if (FileName.empty())
150 NewName = NewName.insert(0, "<unknown>:");
152 NewName = NewName.insert(0, FileName.str() + ":");
157 std::string GlobalValue::getGlobalIdentifier() const {
158 return getGlobalIdentifier(getName(), getLinkage(),
159 getParent()->getSourceFileName());
162 StringRef GlobalValue::getSection() const {
163 if (auto *GA = dyn_cast<GlobalAlias>(this)) {
164 // In general we cannot compute this at the IR level, but we try.
165 if (const GlobalObject *GO = GA->getBaseObject())
166 return GO->getSection();
169 return cast<GlobalObject>(this)->getSection();
172 const Comdat *GlobalValue::getComdat() const {
173 if (auto *GA = dyn_cast<GlobalAlias>(this)) {
174 // In general we cannot compute this at the IR level, but we try.
175 if (const GlobalObject *GO = GA->getBaseObject())
176 return const_cast<GlobalObject *>(GO)->getComdat();
179 // ifunc and its resolver are separate things so don't use resolver comdat.
180 if (isa<GlobalIFunc>(this))
182 return cast<GlobalObject>(this)->getComdat();
185 StringRef GlobalValue::getPartition() const {
188 return getContext().pImpl->GlobalValuePartitions[this];
191 void GlobalValue::setPartition(StringRef S) {
192 // Do nothing if we're clearing the partition and it is already empty.
193 if (!hasPartition() && S.empty())
196 // Get or create a stable partition name string and put it in the table in the
199 S = getContext().pImpl->Saver.save(S);
200 getContext().pImpl->GlobalValuePartitions[this] = S;
202 // Update the HasPartition field. Setting the partition to the empty string
203 // means this global no longer has a partition.
204 HasPartition = !S.empty();
207 StringRef GlobalObject::getSectionImpl() const {
208 assert(hasSection());
209 return getContext().pImpl->GlobalObjectSections[this];
212 void GlobalObject::setSection(StringRef S) {
213 // Do nothing if we're clearing the section and it is already empty.
214 if (!hasSection() && S.empty())
217 // Get or create a stable section name string and put it in the table in the
220 S = getContext().pImpl->Saver.save(S);
221 getContext().pImpl->GlobalObjectSections[this] = S;
223 // Update the HasSectionHashEntryBit. Setting the section to the empty string
224 // means this global no longer has a section.
225 setGlobalObjectFlag(HasSectionHashEntryBit, !S.empty());
228 bool GlobalValue::isDeclaration() const {
229 // Globals are definitions if they have an initializer.
230 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
231 return GV->getNumOperands() == 0;
233 // Functions are definitions if they have a body.
234 if (const Function *F = dyn_cast<Function>(this))
235 return F->empty() && !F->isMaterializable();
237 // Aliases and ifuncs are always definitions.
238 assert(isa<GlobalIndirectSymbol>(this));
242 bool GlobalObject::canIncreaseAlignment() const {
243 // Firstly, can only increase the alignment of a global if it
244 // is a strong definition.
245 if (!isStrongDefinitionForLinker())
248 // It also has to either not have a section defined, or, not have
249 // alignment specified. (If it is assigned a section, the global
250 // could be densely packed with other objects in the section, and
251 // increasing the alignment could cause padding issues.)
252 if (hasSection() && getAlignment() > 0)
255 // On ELF platforms, we're further restricted in that we can't
256 // increase the alignment of any variable which might be emitted
257 // into a shared library, and which is exported. If the main
258 // executable accesses a variable found in a shared-lib, the main
259 // exe actually allocates memory for and exports the symbol ITSELF,
260 // overriding the symbol found in the library. That is, at link
261 // time, the observed alignment of the variable is copied into the
262 // executable binary. (A COPY relocation is also generated, to copy
263 // the initial data from the shadowed variable in the shared-lib
264 // into the location in the main binary, before running code.)
266 // And thus, even though you might think you are defining the
267 // global, and allocating the memory for the global in your object
268 // file, and thus should be able to set the alignment arbitrarily,
269 // that's not actually true. Doing so can cause an ABI breakage; an
270 // executable might have already been built with the previous
271 // alignment of the variable, and then assuming an increased
272 // alignment will be incorrect.
274 // Conservatively assume ELF if there's no parent pointer.
276 (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatELF());
277 if (isELF && !isDSOLocal())
283 const GlobalObject *GlobalValue::getBaseObject() const {
284 if (auto *GO = dyn_cast<GlobalObject>(this))
286 if (auto *GA = dyn_cast<GlobalIndirectSymbol>(this))
287 return GA->getBaseObject();
291 bool GlobalValue::isAbsoluteSymbolRef() const {
292 auto *GO = dyn_cast<GlobalObject>(this);
296 return GO->getMetadata(LLVMContext::MD_absolute_symbol);
299 Optional<ConstantRange> GlobalValue::getAbsoluteSymbolRange() const {
300 auto *GO = dyn_cast<GlobalObject>(this);
304 MDNode *MD = GO->getMetadata(LLVMContext::MD_absolute_symbol);
308 return getConstantRangeFromMetadata(*MD);
311 bool GlobalValue::canBeOmittedFromSymbolTable() const {
312 if (!hasLinkOnceODRLinkage())
315 // We assume that anyone who sets global unnamed_addr on a non-constant
316 // knows what they're doing.
317 if (hasGlobalUnnamedAddr())
320 // If it is a non constant variable, it needs to be uniqued across shared
322 if (auto *Var = dyn_cast<GlobalVariable>(this))
323 if (!Var->isConstant())
326 return hasAtLeastLocalUnnamedAddr();
329 //===----------------------------------------------------------------------===//
330 // GlobalVariable Implementation
331 //===----------------------------------------------------------------------===//
333 GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link,
334 Constant *InitVal, const Twine &Name,
335 ThreadLocalMode TLMode, unsigned AddressSpace,
336 bool isExternallyInitialized)
337 : GlobalObject(Ty, Value::GlobalVariableVal,
338 OperandTraits<GlobalVariable>::op_begin(this),
339 InitVal != nullptr, Link, Name, AddressSpace),
340 isConstantGlobal(constant),
341 isExternallyInitializedConstant(isExternallyInitialized) {
342 assert(!Ty->isFunctionTy() && PointerType::isValidElementType(Ty) &&
343 "invalid type for global variable");
344 setThreadLocalMode(TLMode);
346 assert(InitVal->getType() == Ty &&
347 "Initializer should be the same type as the GlobalVariable!");
352 GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant,
353 LinkageTypes Link, Constant *InitVal,
354 const Twine &Name, GlobalVariable *Before,
355 ThreadLocalMode TLMode, unsigned AddressSpace,
356 bool isExternallyInitialized)
357 : GlobalObject(Ty, Value::GlobalVariableVal,
358 OperandTraits<GlobalVariable>::op_begin(this),
359 InitVal != nullptr, Link, Name, AddressSpace),
360 isConstantGlobal(constant),
361 isExternallyInitializedConstant(isExternallyInitialized) {
362 assert(!Ty->isFunctionTy() && PointerType::isValidElementType(Ty) &&
363 "invalid type for global variable");
364 setThreadLocalMode(TLMode);
366 assert(InitVal->getType() == Ty &&
367 "Initializer should be the same type as the GlobalVariable!");
372 Before->getParent()->getGlobalList().insert(Before->getIterator(), this);
374 M.getGlobalList().push_back(this);
377 void GlobalVariable::removeFromParent() {
378 getParent()->getGlobalList().remove(getIterator());
381 void GlobalVariable::eraseFromParent() {
382 getParent()->getGlobalList().erase(getIterator());
385 void GlobalVariable::setInitializer(Constant *InitVal) {
387 if (hasInitializer()) {
388 // Note, the num operands is used to compute the offset of the operand, so
389 // the order here matters. Clearing the operand then clearing the num
390 // operands ensures we have the correct offset to the operand.
391 Op<0>().set(nullptr);
392 setGlobalVariableNumOperands(0);
395 assert(InitVal->getType() == getValueType() &&
396 "Initializer type must match GlobalVariable type");
397 // Note, the num operands is used to compute the offset of the operand, so
398 // the order here matters. We need to set num operands to 1 first so that
399 // we get the correct offset to the first operand when we set it.
400 if (!hasInitializer())
401 setGlobalVariableNumOperands(1);
402 Op<0>().set(InitVal);
406 /// Copy all additional attributes (those not needed to create a GlobalVariable)
407 /// from the GlobalVariable Src to this one.
408 void GlobalVariable::copyAttributesFrom(const GlobalVariable *Src) {
409 GlobalObject::copyAttributesFrom(Src);
410 setExternallyInitialized(Src->isExternallyInitialized());
411 setAttributes(Src->getAttributes());
414 void GlobalVariable::dropAllReferences() {
415 User::dropAllReferences();
419 //===----------------------------------------------------------------------===//
420 // GlobalIndirectSymbol Implementation
421 //===----------------------------------------------------------------------===//
423 GlobalIndirectSymbol::GlobalIndirectSymbol(Type *Ty, ValueTy VTy,
424 unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name,
426 : GlobalValue(Ty, VTy, &Op<0>(), 1, Linkage, Name, AddressSpace) {
430 static const GlobalObject *
431 findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
432 if (auto *GO = dyn_cast<GlobalObject>(C))
434 if (auto *GA = dyn_cast<GlobalAlias>(C))
435 if (Aliases.insert(GA).second)
436 return findBaseObject(GA->getOperand(0), Aliases);
437 if (auto *CE = dyn_cast<ConstantExpr>(C)) {
438 switch (CE->getOpcode()) {
439 case Instruction::Add: {
440 auto *LHS = findBaseObject(CE->getOperand(0), Aliases);
441 auto *RHS = findBaseObject(CE->getOperand(1), Aliases);
444 return LHS ? LHS : RHS;
446 case Instruction::Sub: {
447 if (findBaseObject(CE->getOperand(1), Aliases))
449 return findBaseObject(CE->getOperand(0), Aliases);
451 case Instruction::IntToPtr:
452 case Instruction::PtrToInt:
453 case Instruction::BitCast:
454 case Instruction::GetElementPtr:
455 return findBaseObject(CE->getOperand(0), Aliases);
463 const GlobalObject *GlobalIndirectSymbol::getBaseObject() const {
464 DenseSet<const GlobalAlias *> Aliases;
465 return findBaseObject(getOperand(0), Aliases);
468 //===----------------------------------------------------------------------===//
469 // GlobalAlias Implementation
470 //===----------------------------------------------------------------------===//
472 GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
473 const Twine &Name, Constant *Aliasee,
474 Module *ParentModule)
475 : GlobalIndirectSymbol(Ty, Value::GlobalAliasVal, AddressSpace, Link, Name,
478 ParentModule->getAliasList().push_back(this);
481 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
482 LinkageTypes Link, const Twine &Name,
483 Constant *Aliasee, Module *ParentModule) {
484 return new GlobalAlias(Ty, AddressSpace, Link, Name, Aliasee, ParentModule);
487 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
488 LinkageTypes Linkage, const Twine &Name,
490 return create(Ty, AddressSpace, Linkage, Name, nullptr, Parent);
493 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
494 LinkageTypes Linkage, const Twine &Name,
495 GlobalValue *Aliasee) {
496 return create(Ty, AddressSpace, Linkage, Name, Aliasee, Aliasee->getParent());
499 GlobalAlias *GlobalAlias::create(LinkageTypes Link, const Twine &Name,
500 GlobalValue *Aliasee) {
501 PointerType *PTy = Aliasee->getType();
502 return create(PTy->getElementType(), PTy->getAddressSpace(), Link, Name,
506 GlobalAlias *GlobalAlias::create(const Twine &Name, GlobalValue *Aliasee) {
507 return create(Aliasee->getLinkage(), Name, Aliasee);
510 void GlobalAlias::removeFromParent() {
511 getParent()->getAliasList().remove(getIterator());
514 void GlobalAlias::eraseFromParent() {
515 getParent()->getAliasList().erase(getIterator());
518 void GlobalAlias::setAliasee(Constant *Aliasee) {
519 assert((!Aliasee || Aliasee->getType() == getType()) &&
520 "Alias and aliasee types should match!");
521 setIndirectSymbol(Aliasee);
524 //===----------------------------------------------------------------------===//
525 // GlobalIFunc Implementation
526 //===----------------------------------------------------------------------===//
528 GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
529 const Twine &Name, Constant *Resolver,
530 Module *ParentModule)
531 : GlobalIndirectSymbol(Ty, Value::GlobalIFuncVal, AddressSpace, Link, Name,
534 ParentModule->getIFuncList().push_back(this);
537 GlobalIFunc *GlobalIFunc::create(Type *Ty, unsigned AddressSpace,
538 LinkageTypes Link, const Twine &Name,
539 Constant *Resolver, Module *ParentModule) {
540 return new GlobalIFunc(Ty, AddressSpace, Link, Name, Resolver, ParentModule);
543 void GlobalIFunc::removeFromParent() {
544 getParent()->getIFuncList().remove(getIterator());
547 void GlobalIFunc::eraseFromParent() {
548 getParent()->getIFuncList().erase(getIterator());