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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 VMCore
11 // library.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Constants.h"
16 #include "llvm/GlobalVariable.h"
17 #include "llvm/GlobalAlias.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Module.h"
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/LeakDetector.h"
23 using namespace llvm;
24 
25 //===----------------------------------------------------------------------===//
26 //                            GlobalValue Class
27 //===----------------------------------------------------------------------===//
28 
isMaterializable() const29 bool GlobalValue::isMaterializable() const {
30   return getParent() && getParent()->isMaterializable(this);
31 }
isDematerializable() const32 bool GlobalValue::isDematerializable() const {
33   return getParent() && getParent()->isDematerializable(this);
34 }
Materialize(std::string * ErrInfo)35 bool GlobalValue::Materialize(std::string *ErrInfo) {
36   return getParent()->Materialize(this, ErrInfo);
37 }
Dematerialize()38 void GlobalValue::Dematerialize() {
39   getParent()->Dematerialize(this);
40 }
41 
42 /// Override destroyConstant to make sure it doesn't get called on
43 /// GlobalValue's because they shouldn't be treated like other constants.
destroyConstant()44 void GlobalValue::destroyConstant() {
45   llvm_unreachable("You can't GV->destroyConstant()!");
46 }
47 
48 /// copyAttributesFrom - copy all additional attributes (those not needed to
49 /// create a GlobalValue) from the GlobalValue Src to this one.
copyAttributesFrom(const GlobalValue * Src)50 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
51   setAlignment(Src->getAlignment());
52   setSection(Src->getSection());
53   setVisibility(Src->getVisibility());
54   setUnnamedAddr(Src->hasUnnamedAddr());
55 }
56 
setAlignment(unsigned Align)57 void GlobalValue::setAlignment(unsigned Align) {
58   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
59   assert(Align <= MaximumAlignment &&
60          "Alignment is greater than MaximumAlignment!");
61   Alignment = Log2_32(Align) + 1;
62   assert(getAlignment() == Align && "Alignment representation error!");
63 }
64 
isDeclaration() const65 bool GlobalValue::isDeclaration() const {
66   // Globals are definitions if they have an initializer.
67   if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
68     return GV->getNumOperands() == 0;
69 
70   // Functions are definitions if they have a body.
71   if (const Function *F = dyn_cast<Function>(this))
72     return F->empty();
73 
74   // Aliases are always definitions.
75   assert(isa<GlobalAlias>(this));
76   return false;
77 }
78 
79 //===----------------------------------------------------------------------===//
80 // GlobalVariable Implementation
81 //===----------------------------------------------------------------------===//
82 
GlobalVariable(Type * Ty,bool constant,LinkageTypes Link,Constant * InitVal,const Twine & Name,ThreadLocalMode TLMode,unsigned AddressSpace)83 GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link,
84                                Constant *InitVal, const Twine &Name,
85                                ThreadLocalMode TLMode, unsigned AddressSpace)
86   : GlobalValue(PointerType::get(Ty, AddressSpace),
87                 Value::GlobalVariableVal,
88                 OperandTraits<GlobalVariable>::op_begin(this),
89                 InitVal != 0, Link, Name),
90     isConstantGlobal(constant), threadLocalMode(TLMode) {
91   if (InitVal) {
92     assert(InitVal->getType() == Ty &&
93            "Initializer should be the same type as the GlobalVariable!");
94     Op<0>() = InitVal;
95   }
96 
97   LeakDetector::addGarbageObject(this);
98 }
99 
GlobalVariable(Module & M,Type * Ty,bool constant,LinkageTypes Link,Constant * InitVal,const Twine & Name,GlobalVariable * Before,ThreadLocalMode TLMode,unsigned AddressSpace)100 GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant,
101                                LinkageTypes Link, Constant *InitVal,
102                                const Twine &Name,
103                                GlobalVariable *Before, ThreadLocalMode TLMode,
104                                unsigned AddressSpace)
105   : GlobalValue(PointerType::get(Ty, AddressSpace),
106                 Value::GlobalVariableVal,
107                 OperandTraits<GlobalVariable>::op_begin(this),
108                 InitVal != 0, Link, Name),
109     isConstantGlobal(constant), threadLocalMode(TLMode) {
110   if (InitVal) {
111     assert(InitVal->getType() == Ty &&
112            "Initializer should be the same type as the GlobalVariable!");
113     Op<0>() = InitVal;
114   }
115 
116   LeakDetector::addGarbageObject(this);
117 
118   if (Before)
119     Before->getParent()->getGlobalList().insert(Before, this);
120   else
121     M.getGlobalList().push_back(this);
122 }
123 
setParent(Module * parent)124 void GlobalVariable::setParent(Module *parent) {
125   if (getParent())
126     LeakDetector::addGarbageObject(this);
127   Parent = parent;
128   if (getParent())
129     LeakDetector::removeGarbageObject(this);
130 }
131 
removeFromParent()132 void GlobalVariable::removeFromParent() {
133   getParent()->getGlobalList().remove(this);
134 }
135 
eraseFromParent()136 void GlobalVariable::eraseFromParent() {
137   getParent()->getGlobalList().erase(this);
138 }
139 
replaceUsesOfWithOnConstant(Value * From,Value * To,Use * U)140 void GlobalVariable::replaceUsesOfWithOnConstant(Value *From, Value *To,
141                                                  Use *U) {
142   // If you call this, then you better know this GVar has a constant
143   // initializer worth replacing. Enforce that here.
144   assert(getNumOperands() == 1 &&
145          "Attempt to replace uses of Constants on a GVar with no initializer");
146 
147   // And, since you know it has an initializer, the From value better be
148   // the initializer :)
149   assert(getOperand(0) == From &&
150          "Attempt to replace wrong constant initializer in GVar");
151 
152   // And, you better have a constant for the replacement value
153   assert(isa<Constant>(To) &&
154          "Attempt to replace GVar initializer with non-constant");
155 
156   // Okay, preconditions out of the way, replace the constant initializer.
157   this->setOperand(0, cast<Constant>(To));
158 }
159 
setInitializer(Constant * InitVal)160 void GlobalVariable::setInitializer(Constant *InitVal) {
161   if (InitVal == 0) {
162     if (hasInitializer()) {
163       Op<0>().set(0);
164       NumOperands = 0;
165     }
166   } else {
167     assert(InitVal->getType() == getType()->getElementType() &&
168            "Initializer type must match GlobalVariable type");
169     if (!hasInitializer())
170       NumOperands = 1;
171     Op<0>().set(InitVal);
172   }
173 }
174 
175 /// copyAttributesFrom - copy all additional attributes (those not needed to
176 /// create a GlobalVariable) from the GlobalVariable Src to this one.
copyAttributesFrom(const GlobalValue * Src)177 void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) {
178   assert(isa<GlobalVariable>(Src) && "Expected a GlobalVariable!");
179   GlobalValue::copyAttributesFrom(Src);
180   const GlobalVariable *SrcVar = cast<GlobalVariable>(Src);
181   setThreadLocal(SrcVar->isThreadLocal());
182 }
183 
184 
185 //===----------------------------------------------------------------------===//
186 // GlobalAlias Implementation
187 //===----------------------------------------------------------------------===//
188 
GlobalAlias(Type * Ty,LinkageTypes Link,const Twine & Name,Constant * aliasee,Module * ParentModule)189 GlobalAlias::GlobalAlias(Type *Ty, LinkageTypes Link,
190                          const Twine &Name, Constant* aliasee,
191                          Module *ParentModule)
192   : GlobalValue(Ty, Value::GlobalAliasVal, &Op<0>(), 1, Link, Name) {
193   LeakDetector::addGarbageObject(this);
194 
195   if (aliasee)
196     assert(aliasee->getType() == Ty && "Alias and aliasee types should match!");
197   Op<0>() = aliasee;
198 
199   if (ParentModule)
200     ParentModule->getAliasList().push_back(this);
201 }
202 
setParent(Module * parent)203 void GlobalAlias::setParent(Module *parent) {
204   if (getParent())
205     LeakDetector::addGarbageObject(this);
206   Parent = parent;
207   if (getParent())
208     LeakDetector::removeGarbageObject(this);
209 }
210 
removeFromParent()211 void GlobalAlias::removeFromParent() {
212   getParent()->getAliasList().remove(this);
213 }
214 
eraseFromParent()215 void GlobalAlias::eraseFromParent() {
216   getParent()->getAliasList().erase(this);
217 }
218 
setAliasee(Constant * Aliasee)219 void GlobalAlias::setAliasee(Constant *Aliasee) {
220   assert((!Aliasee || Aliasee->getType() == getType()) &&
221          "Alias and aliasee types should match!");
222 
223   setOperand(0, Aliasee);
224 }
225 
getAliasedGlobal() const226 const GlobalValue *GlobalAlias::getAliasedGlobal() const {
227   const Constant *C = getAliasee();
228   if (C == 0) return 0;
229 
230   if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
231     return GV;
232 
233   const ConstantExpr *CE = cast<ConstantExpr>(C);
234   assert((CE->getOpcode() == Instruction::BitCast ||
235           CE->getOpcode() == Instruction::GetElementPtr) &&
236          "Unsupported aliasee");
237 
238   return cast<GlobalValue>(CE->getOperand(0));
239 }
240 
resolveAliasedGlobal(bool stopOnWeak) const241 const GlobalValue *GlobalAlias::resolveAliasedGlobal(bool stopOnWeak) const {
242   SmallPtrSet<const GlobalValue*, 3> Visited;
243 
244   // Check if we need to stop early.
245   if (stopOnWeak && mayBeOverridden())
246     return this;
247 
248   const GlobalValue *GV = getAliasedGlobal();
249   Visited.insert(GV);
250 
251   // Iterate over aliasing chain, stopping on weak alias if necessary.
252   while (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV)) {
253     if (stopOnWeak && GA->mayBeOverridden())
254       break;
255 
256     GV = GA->getAliasedGlobal();
257 
258     if (!Visited.insert(GV))
259       return 0;
260   }
261 
262   return GV;
263 }
264