lib/VMCore/Globals.cpp

   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/LLVMContext.h"
  20 #include "llvm/Module.h"
  21 #include "llvm/ADT/SmallPtrSet.h"
  22 #include "llvm/Support/ErrorHandling.h"
  23 #include "llvm/Support/LeakDetector.h"
  24 using namespace llvm;
  25
  26 //===----------------------------------------------------------------------===//
  27 //                            GlobalValue Class
  28 //===----------------------------------------------------------------------===//
  29
  30 /// removeDeadUsersOfConstant - If the specified constantexpr is dead, remove
  31 /// it.  This involves recursively eliminating any dead users of the
  32 /// constantexpr.
  33 static bool removeDeadUsersOfConstant(const Constant *C) {
  34   if (isa<GlobalValue>(C)) return false; // Cannot remove this
  35
  36   while (!C->use_empty()) {
  37     const Constant *User = dyn_cast<Constant>(C->use_back());
  38     if (!User) return false; // Non-constant usage;
  39     if (!removeDeadUsersOfConstant(User))
  40       return false; // Constant wasn't dead
  41   }
  42
  43   const_cast<Constant*>(C)->destroyConstant();
  44   return true;
  45 }
  46
  47 /// removeDeadConstantUsers - If there are any dead constant users dangling
  48 /// off of this global value, remove them.  This method is useful for clients
  49 /// that want to check to see if a global is unused, but don't want to deal
  50 /// with potentially dead constants hanging off of the globals.
  51 void GlobalValue::removeDeadConstantUsers() const {
  52   Value::use_const_iterator I = use_begin(), E = use_end();
  53   Value::use_const_iterator LastNonDeadUser = E;
  54   while (I != E) {
  55     if (const Constant *User = dyn_cast<Constant>(*I)) {
  56       if (!removeDeadUsersOfConstant(User)) {
  57         // If the constant wasn't dead, remember that this was the last live use
  58         // and move on to the next constant.
  59         LastNonDeadUser = I;
  60         ++I;
  61       } else {
  62         // If the constant was dead, then the iterator is invalidated.
  63         if (LastNonDeadUser == E) {
  64           I = use_begin();
  65           if (I == E) break;
  66         } else {
  67           I = LastNonDeadUser;
  68           ++I;
  69         }
  70       }
  71     } else {
  72       LastNonDeadUser = I;
  73       ++I;
  74     }
  75   }
  76 }
  77
  78 /// Override destroyConstant to make sure it doesn't get called on
  79 /// GlobalValue's because they shouldn't be treated like other constants.
  80 void GlobalValue::destroyConstant() {
  81   llvm_unreachable("You can't GV->destroyConstant()!");
  82 }
  83
  84 /// copyAttributesFrom - copy all additional attributes (those not needed to
  85 /// create a GlobalValue) from the GlobalValue Src to this one.
  86 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
  87   setAlignment(Src->getAlignment());
  88   setSection(Src->getSection());
  89   setVisibility(Src->getVisibility());
  90 }
  91
  92
  93 //===----------------------------------------------------------------------===//
  94 // GlobalVariable Implementation
  95 //===----------------------------------------------------------------------===//
  96
  97 GlobalVariable::GlobalVariable(LLVMContext &Context, const Type *Ty,
  98                                bool constant, LinkageTypes Link,
  99                                Constant *InitVal, const Twine &Name,
 100                                bool ThreadLocal, unsigned AddressSpace)
 101   : GlobalValue(PointerType::get(Ty, AddressSpace),
 102                 Value::GlobalVariableVal,
 103                 OperandTraits<GlobalVariable>::op_begin(this),
 104                 InitVal != 0, Link, Name),
 105     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
 106   if (InitVal) {
 107     assert(InitVal->getType() == Ty &&
 108            "Initializer should be the same type as the GlobalVariable!");
 109     Op<0>() = InitVal;
 110   }
 111
 112   LeakDetector::addGarbageObject(this);
 113 }
 114
 115 GlobalVariable::GlobalVariable(Module &M, const Type *Ty, bool constant,
 116                                LinkageTypes Link, Constant *InitVal,
 117                                const Twine &Name,
 118                                GlobalVariable *Before, bool ThreadLocal,
 119                                unsigned AddressSpace)
 120   : GlobalValue(PointerType::get(Ty, AddressSpace),
 121                 Value::GlobalVariableVal,
 122                 OperandTraits<GlobalVariable>::op_begin(this),
 123                 InitVal != 0, Link, Name),
 124     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
 125   if (InitVal) {
 126     assert(InitVal->getType() == Ty &&
 127            "Initializer should be the same type as the GlobalVariable!");
 128     Op<0>() = InitVal;
 129   }
 130
 131   LeakDetector::addGarbageObject(this);
 132
 133   if (Before)
 134     Before->getParent()->getGlobalList().insert(Before, this);
 135   else
 136     M.getGlobalList().push_back(this);
 137 }
 138
 139 void GlobalVariable::setParent(Module *parent) {
 140   if (getParent())
 141     LeakDetector::addGarbageObject(this);
 142   Parent = parent;
 143   if (getParent())
 144     LeakDetector::removeGarbageObject(this);
 145 }
 146
 147 void GlobalVariable::removeFromParent() {
 148   getParent()->getGlobalList().remove(this);
 149 }
 150
 151 void GlobalVariable::eraseFromParent() {
 152   getParent()->getGlobalList().erase(this);
 153 }
 154
 155 void GlobalVariable::replaceUsesOfWithOnConstant(Value *From, Value *To,
 156                                                  Use *U) {
 157   // If you call this, then you better know this GVar has a constant
 158   // initializer worth replacing. Enforce that here.
 159   assert(getNumOperands() == 1 &&
 160          "Attempt to replace uses of Constants on a GVar with no initializer");
 161
 162   // And, since you know it has an initializer, the From value better be
 163   // the initializer :)
 164   assert(getOperand(0) == From &&
 165          "Attempt to replace wrong constant initializer in GVar");
 166
 167   // And, you better have a constant for the replacement value
 168   assert(isa<Constant>(To) &&
 169          "Attempt to replace GVar initializer with non-constant");
 170
 171   // Okay, preconditions out of the way, replace the constant initializer.
 172   this->setOperand(0, cast<Constant>(To));
 173 }
 174
 175 /// copyAttributesFrom - copy all additional attributes (those not needed to
 176 /// create a GlobalVariable) from the GlobalVariable Src to this one.
 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
 189 GlobalAlias::GlobalAlias(const 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
 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
 211 void GlobalAlias::removeFromParent() {
 212   getParent()->getAliasList().remove(this);
 213 }
 214
 215 void GlobalAlias::eraseFromParent() {
 216   getParent()->getAliasList().erase(this);
 217 }
 218
 219 bool GlobalAlias::isDeclaration() const {
 220   const GlobalValue* AV = getAliasedGlobal();
 221   if (AV)
 222     return AV->isDeclaration();
 223   else
 224     return false;
 225 }
 226
 227 void GlobalAlias::setAliasee(Constant *Aliasee)
 228 {
 229   if (Aliasee)
 230     assert(Aliasee->getType() == getType() &&
 231            "Alias and aliasee types should match!");
 232
 233   setOperand(0, Aliasee);
 234 }
 235
 236 const GlobalValue *GlobalAlias::getAliasedGlobal() const {
 237   const Constant *C = getAliasee();
 238   if (C) {
 239     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
 240       return GV;
 241     else {
 242       const ConstantExpr *CE = 0;
 243       if ((CE = dyn_cast<ConstantExpr>(C)) &&
 244           (CE->getOpcode() == Instruction::BitCast ||
 245            CE->getOpcode() == Instruction::GetElementPtr))
 246         return dyn_cast<GlobalValue>(CE->getOperand(0));
 247       else
 248         llvm_unreachable("Unsupported aliasee");
 249     }
 250   }
 251   return 0;
 252 }
 253
 254 const GlobalValue *GlobalAlias::resolveAliasedGlobal(bool stopOnWeak) const {
 255   SmallPtrSet<const GlobalValue*, 3> Visited;
 256
 257   // Check if we need to stop early.
 258   if (stopOnWeak && mayBeOverridden())
 259     return this;
 260
 261   const GlobalValue *GV = getAliasedGlobal();
 262   Visited.insert(GV);
 263
 264   // Iterate over aliasing chain, stopping on weak alias if necessary.
 265   while (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV)) {
 266     if (stopOnWeak && GA->mayBeOverridden())
 267       break;
 268
 269     GV = GA->getAliasedGlobal();
 270
 271     if (!Visited.insert(GV))
 272       return NULL;
 273   }
 274
 275   return GV;
 276 }