1 //===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the GlobalValue & GlobalVariable classes for the IR
11 // library.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/IR/Constants.h"
18 #include "llvm/IR/DerivedTypes.h"
19 #include "llvm/IR/GlobalAlias.h"
20 #include "llvm/IR/GlobalValue.h"
21 #include "llvm/IR/GlobalVariable.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/IR/Operator.h"
24 #include "llvm/Support/ErrorHandling.h"
25 using namespace llvm;
26
27 //===----------------------------------------------------------------------===//
28 // GlobalValue Class
29 //===----------------------------------------------------------------------===//
30
isMaterializable() const31 bool GlobalValue::isMaterializable() const {
32 if (const Function *F = dyn_cast<Function>(this))
33 return F->isMaterializable();
34 return false;
35 }
materialize()36 std::error_code GlobalValue::materialize() {
37 return getParent()->materialize(this);
38 }
39
40 /// Override destroyConstantImpl to make sure it doesn't get called on
41 /// GlobalValue's because they shouldn't be treated like other constants.
destroyConstantImpl()42 void GlobalValue::destroyConstantImpl() {
43 llvm_unreachable("You can't GV->destroyConstantImpl()!");
44 }
45
handleOperandChangeImpl(Value * From,Value * To)46 Value *GlobalValue::handleOperandChangeImpl(Value *From, Value *To) {
47 llvm_unreachable("Unsupported class for handleOperandChange()!");
48 }
49
50 /// copyAttributesFrom - copy all additional attributes (those not needed to
51 /// create a GlobalValue) from the GlobalValue Src to this one.
copyAttributesFrom(const GlobalValue * Src)52 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
53 setVisibility(Src->getVisibility());
54 setUnnamedAddr(Src->getUnnamedAddr());
55 setDLLStorageClass(Src->getDLLStorageClass());
56 }
57
getAlignment() const58 unsigned GlobalValue::getAlignment() const {
59 if (auto *GA = dyn_cast<GlobalAlias>(this)) {
60 // In general we cannot compute this at the IR level, but we try.
61 if (const GlobalObject *GO = GA->getBaseObject())
62 return GO->getAlignment();
63
64 // FIXME: we should also be able to handle:
65 // Alias = Global + Offset
66 // Alias = Absolute
67 return 0;
68 }
69 return cast<GlobalObject>(this)->getAlignment();
70 }
71
setAlignment(unsigned Align)72 void GlobalObject::setAlignment(unsigned Align) {
73 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
74 assert(Align <= MaximumAlignment &&
75 "Alignment is greater than MaximumAlignment!");
76 unsigned AlignmentData = Log2_32(Align) + 1;
77 unsigned OldData = getGlobalValueSubClassData();
78 setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
79 assert(getAlignment() == Align && "Alignment representation error!");
80 }
81
getGlobalObjectSubClassData() const82 unsigned GlobalObject::getGlobalObjectSubClassData() const {
83 unsigned ValueData = getGlobalValueSubClassData();
84 return ValueData >> GlobalObjectBits;
85 }
86
setGlobalObjectSubClassData(unsigned Val)87 void GlobalObject::setGlobalObjectSubClassData(unsigned Val) {
88 unsigned OldData = getGlobalValueSubClassData();
89 setGlobalValueSubClassData((OldData & GlobalObjectMask) |
90 (Val << GlobalObjectBits));
91 assert(getGlobalObjectSubClassData() == Val && "representation error");
92 }
93
copyAttributesFrom(const GlobalValue * Src)94 void GlobalObject::copyAttributesFrom(const GlobalValue *Src) {
95 GlobalValue::copyAttributesFrom(Src);
96 if (const auto *GV = dyn_cast<GlobalObject>(Src)) {
97 setAlignment(GV->getAlignment());
98 setSection(GV->getSection());
99 }
100 }
101
getGlobalIdentifier(StringRef Name,GlobalValue::LinkageTypes Linkage,StringRef FileName)102 std::string GlobalValue::getGlobalIdentifier(StringRef Name,
103 GlobalValue::LinkageTypes Linkage,
104 StringRef FileName) {
105
106 // Value names may be prefixed with a binary '1' to indicate
107 // that the backend should not modify the symbols due to any platform
108 // naming convention. Do not include that '1' in the PGO profile name.
109 if (Name[0] == '\1')
110 Name = Name.substr(1);
111
112 std::string NewName = Name;
113 if (llvm::GlobalValue::isLocalLinkage(Linkage)) {
114 // For local symbols, prepend the main file name to distinguish them.
115 // Do not include the full path in the file name since there's no guarantee
116 // that it will stay the same, e.g., if the files are checked out from
117 // version control in different locations.
118 if (FileName.empty())
119 NewName = NewName.insert(0, "<unknown>:");
120 else
121 NewName = NewName.insert(0, FileName.str() + ":");
122 }
123 return NewName;
124 }
125
getGlobalIdentifier() const126 std::string GlobalValue::getGlobalIdentifier() const {
127 return getGlobalIdentifier(getName(), getLinkage(),
128 getParent()->getSourceFileName());
129 }
130
getSection() const131 StringRef GlobalValue::getSection() const {
132 if (auto *GA = dyn_cast<GlobalAlias>(this)) {
133 // In general we cannot compute this at the IR level, but we try.
134 if (const GlobalObject *GO = GA->getBaseObject())
135 return GO->getSection();
136 return "";
137 }
138 return cast<GlobalObject>(this)->getSection();
139 }
140
getComdat()141 Comdat *GlobalValue::getComdat() {
142 if (auto *GA = dyn_cast<GlobalAlias>(this)) {
143 // In general we cannot compute this at the IR level, but we try.
144 if (const GlobalObject *GO = GA->getBaseObject())
145 return const_cast<GlobalObject *>(GO)->getComdat();
146 return nullptr;
147 }
148 // ifunc and its resolver are separate things so don't use resolver comdat.
149 if (isa<GlobalIFunc>(this))
150 return nullptr;
151 return cast<GlobalObject>(this)->getComdat();
152 }
153
setSection(StringRef S)154 void GlobalObject::setSection(StringRef S) {
155 Section = S;
156
157 // The C api requires this to be null terminated.
158 Section.c_str();
159 }
160
isDeclaration() const161 bool GlobalValue::isDeclaration() const {
162 // Globals are definitions if they have an initializer.
163 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
164 return GV->getNumOperands() == 0;
165
166 // Functions are definitions if they have a body.
167 if (const Function *F = dyn_cast<Function>(this))
168 return F->empty() && !F->isMaterializable();
169
170 // Aliases and ifuncs are always definitions.
171 assert(isa<GlobalIndirectSymbol>(this));
172 return false;
173 }
174
canIncreaseAlignment() const175 bool GlobalValue::canIncreaseAlignment() const {
176 // Firstly, can only increase the alignment of a global if it
177 // is a strong definition.
178 if (!isStrongDefinitionForLinker())
179 return false;
180
181 // It also has to either not have a section defined, or, not have
182 // alignment specified. (If it is assigned a section, the global
183 // could be densely packed with other objects in the section, and
184 // increasing the alignment could cause padding issues.)
185 if (hasSection() && getAlignment() > 0)
186 return false;
187
188 // On ELF platforms, we're further restricted in that we can't
189 // increase the alignment of any variable which might be emitted
190 // into a shared library, and which is exported. If the main
191 // executable accesses a variable found in a shared-lib, the main
192 // exe actually allocates memory for and exports the symbol ITSELF,
193 // overriding the symbol found in the library. That is, at link
194 // time, the observed alignment of the variable is copied into the
195 // executable binary. (A COPY relocation is also generated, to copy
196 // the initial data from the shadowed variable in the shared-lib
197 // into the location in the main binary, before running code.)
198 //
199 // And thus, even though you might think you are defining the
200 // global, and allocating the memory for the global in your object
201 // file, and thus should be able to set the alignment arbitrarily,
202 // that's not actually true. Doing so can cause an ABI breakage; an
203 // executable might have already been built with the previous
204 // alignment of the variable, and then assuming an increased
205 // alignment will be incorrect.
206
207 // Conservatively assume ELF if there's no parent pointer.
208 bool isELF =
209 (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatELF());
210 if (isELF && hasDefaultVisibility() && !hasLocalLinkage())
211 return false;
212
213 return true;
214 }
215
216 //===----------------------------------------------------------------------===//
217 // GlobalVariable Implementation
218 //===----------------------------------------------------------------------===//
219
GlobalVariable(Type * Ty,bool constant,LinkageTypes Link,Constant * InitVal,const Twine & Name,ThreadLocalMode TLMode,unsigned AddressSpace,bool isExternallyInitialized)220 GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link,
221 Constant *InitVal, const Twine &Name,
222 ThreadLocalMode TLMode, unsigned AddressSpace,
223 bool isExternallyInitialized)
224 : GlobalObject(Ty, Value::GlobalVariableVal,
225 OperandTraits<GlobalVariable>::op_begin(this),
226 InitVal != nullptr, Link, Name, AddressSpace),
227 isConstantGlobal(constant),
228 isExternallyInitializedConstant(isExternallyInitialized) {
229 setThreadLocalMode(TLMode);
230 if (InitVal) {
231 assert(InitVal->getType() == Ty &&
232 "Initializer should be the same type as the GlobalVariable!");
233 Op<0>() = InitVal;
234 }
235 }
236
GlobalVariable(Module & M,Type * Ty,bool constant,LinkageTypes Link,Constant * InitVal,const Twine & Name,GlobalVariable * Before,ThreadLocalMode TLMode,unsigned AddressSpace,bool isExternallyInitialized)237 GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant,
238 LinkageTypes Link, Constant *InitVal,
239 const Twine &Name, GlobalVariable *Before,
240 ThreadLocalMode TLMode, unsigned AddressSpace,
241 bool isExternallyInitialized)
242 : GlobalObject(Ty, Value::GlobalVariableVal,
243 OperandTraits<GlobalVariable>::op_begin(this),
244 InitVal != nullptr, Link, Name, AddressSpace),
245 isConstantGlobal(constant),
246 isExternallyInitializedConstant(isExternallyInitialized) {
247 setThreadLocalMode(TLMode);
248 if (InitVal) {
249 assert(InitVal->getType() == Ty &&
250 "Initializer should be the same type as the GlobalVariable!");
251 Op<0>() = InitVal;
252 }
253
254 if (Before)
255 Before->getParent()->getGlobalList().insert(Before->getIterator(), this);
256 else
257 M.getGlobalList().push_back(this);
258 }
259
setParent(Module * parent)260 void GlobalVariable::setParent(Module *parent) {
261 Parent = parent;
262 }
263
removeFromParent()264 void GlobalVariable::removeFromParent() {
265 getParent()->getGlobalList().remove(getIterator());
266 }
267
eraseFromParent()268 void GlobalVariable::eraseFromParent() {
269 getParent()->getGlobalList().erase(getIterator());
270 }
271
setInitializer(Constant * InitVal)272 void GlobalVariable::setInitializer(Constant *InitVal) {
273 if (!InitVal) {
274 if (hasInitializer()) {
275 // Note, the num operands is used to compute the offset of the operand, so
276 // the order here matters. Clearing the operand then clearing the num
277 // operands ensures we have the correct offset to the operand.
278 Op<0>().set(nullptr);
279 setGlobalVariableNumOperands(0);
280 }
281 } else {
282 assert(InitVal->getType() == getValueType() &&
283 "Initializer type must match GlobalVariable type");
284 // Note, the num operands is used to compute the offset of the operand, so
285 // the order here matters. We need to set num operands to 1 first so that
286 // we get the correct offset to the first operand when we set it.
287 if (!hasInitializer())
288 setGlobalVariableNumOperands(1);
289 Op<0>().set(InitVal);
290 }
291 }
292
293 /// Copy all additional attributes (those not needed to create a GlobalVariable)
294 /// from the GlobalVariable Src to this one.
copyAttributesFrom(const GlobalValue * Src)295 void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) {
296 GlobalObject::copyAttributesFrom(Src);
297 if (const GlobalVariable *SrcVar = dyn_cast<GlobalVariable>(Src)) {
298 setThreadLocalMode(SrcVar->getThreadLocalMode());
299 setExternallyInitialized(SrcVar->isExternallyInitialized());
300 }
301 }
302
dropAllReferences()303 void GlobalVariable::dropAllReferences() {
304 User::dropAllReferences();
305 clearMetadata();
306 }
307
308 //===----------------------------------------------------------------------===//
309 // GlobalIndirectSymbol Implementation
310 //===----------------------------------------------------------------------===//
311
GlobalIndirectSymbol(Type * Ty,ValueTy VTy,unsigned AddressSpace,LinkageTypes Linkage,const Twine & Name,Constant * Symbol)312 GlobalIndirectSymbol::GlobalIndirectSymbol(Type *Ty, ValueTy VTy,
313 unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name,
314 Constant *Symbol)
315 : GlobalValue(Ty, VTy, &Op<0>(), 1, Linkage, Name, AddressSpace) {
316 Op<0>() = Symbol;
317 }
318
319
320 //===----------------------------------------------------------------------===//
321 // GlobalAlias Implementation
322 //===----------------------------------------------------------------------===//
323
GlobalAlias(Type * Ty,unsigned AddressSpace,LinkageTypes Link,const Twine & Name,Constant * Aliasee,Module * ParentModule)324 GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
325 const Twine &Name, Constant *Aliasee,
326 Module *ParentModule)
327 : GlobalIndirectSymbol(Ty, Value::GlobalAliasVal, AddressSpace, Link, Name,
328 Aliasee) {
329 if (ParentModule)
330 ParentModule->getAliasList().push_back(this);
331 }
332
create(Type * Ty,unsigned AddressSpace,LinkageTypes Link,const Twine & Name,Constant * Aliasee,Module * ParentModule)333 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
334 LinkageTypes Link, const Twine &Name,
335 Constant *Aliasee, Module *ParentModule) {
336 return new GlobalAlias(Ty, AddressSpace, Link, Name, Aliasee, ParentModule);
337 }
338
create(Type * Ty,unsigned AddressSpace,LinkageTypes Linkage,const Twine & Name,Module * Parent)339 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
340 LinkageTypes Linkage, const Twine &Name,
341 Module *Parent) {
342 return create(Ty, AddressSpace, Linkage, Name, nullptr, Parent);
343 }
344
create(Type * Ty,unsigned AddressSpace,LinkageTypes Linkage,const Twine & Name,GlobalValue * Aliasee)345 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
346 LinkageTypes Linkage, const Twine &Name,
347 GlobalValue *Aliasee) {
348 return create(Ty, AddressSpace, Linkage, Name, Aliasee, Aliasee->getParent());
349 }
350
create(LinkageTypes Link,const Twine & Name,GlobalValue * Aliasee)351 GlobalAlias *GlobalAlias::create(LinkageTypes Link, const Twine &Name,
352 GlobalValue *Aliasee) {
353 PointerType *PTy = Aliasee->getType();
354 return create(PTy->getElementType(), PTy->getAddressSpace(), Link, Name,
355 Aliasee);
356 }
357
create(const Twine & Name,GlobalValue * Aliasee)358 GlobalAlias *GlobalAlias::create(const Twine &Name, GlobalValue *Aliasee) {
359 return create(Aliasee->getLinkage(), Name, Aliasee);
360 }
361
setParent(Module * parent)362 void GlobalAlias::setParent(Module *parent) {
363 Parent = parent;
364 }
365
removeFromParent()366 void GlobalAlias::removeFromParent() {
367 getParent()->getAliasList().remove(getIterator());
368 }
369
eraseFromParent()370 void GlobalAlias::eraseFromParent() {
371 getParent()->getAliasList().erase(getIterator());
372 }
373
setAliasee(Constant * Aliasee)374 void GlobalAlias::setAliasee(Constant *Aliasee) {
375 assert((!Aliasee || Aliasee->getType() == getType()) &&
376 "Alias and aliasee types should match!");
377 setIndirectSymbol(Aliasee);
378 }
379
380 //===----------------------------------------------------------------------===//
381 // GlobalIFunc Implementation
382 //===----------------------------------------------------------------------===//
383
GlobalIFunc(Type * Ty,unsigned AddressSpace,LinkageTypes Link,const Twine & Name,Constant * Resolver,Module * ParentModule)384 GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
385 const Twine &Name, Constant *Resolver,
386 Module *ParentModule)
387 : GlobalIndirectSymbol(Ty, Value::GlobalIFuncVal, AddressSpace, Link, Name,
388 Resolver) {
389 if (ParentModule)
390 ParentModule->getIFuncList().push_back(this);
391 }
392
create(Type * Ty,unsigned AddressSpace,LinkageTypes Link,const Twine & Name,Constant * Resolver,Module * ParentModule)393 GlobalIFunc *GlobalIFunc::create(Type *Ty, unsigned AddressSpace,
394 LinkageTypes Link, const Twine &Name,
395 Constant *Resolver, Module *ParentModule) {
396 return new GlobalIFunc(Ty, AddressSpace, Link, Name, Resolver, ParentModule);
397 }
398
setParent(Module * parent)399 void GlobalIFunc::setParent(Module *parent) {
400 Parent = parent;
401 }
402
removeFromParent()403 void GlobalIFunc::removeFromParent() {
404 getParent()->getIFuncList().remove(getIterator());
405 }
406
eraseFromParent()407 void GlobalIFunc::eraseFromParent() {
408 getParent()->getIFuncList().erase(getIterator());
409 }
410