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/Module.h"
  20 #include "llvm/ADT/SmallPtrSet.h"
  21 #include "llvm/Support/LeakDetector.h"
  22 using namespace llvm;
  23
  24 //===----------------------------------------------------------------------===//
  25 //                            GlobalValue Class
  26 //===----------------------------------------------------------------------===//
  27
  28 /// removeDeadUsersOfConstant - If the specified constantexpr is dead, remove
  29 /// it.  This involves recursively eliminating any dead users of the
  30 /// constantexpr.
  31 static bool removeDeadUsersOfConstant(const Constant *C) {
  32   if (isa<GlobalValue>(C)) return false; // Cannot remove this
  33
  34   while (!C->use_empty()) {
  35     const Constant *User = dyn_cast<Constant>(C->use_back());
  36     if (!User) return false; // Non-constant usage;
  37     if (!removeDeadUsersOfConstant(User))
  38       return false; // Constant wasn't dead
  39   }
  40
  41   const_cast<Constant*>(C)->destroyConstant();
  42   return true;
  43 }
  44
  45 /// removeDeadConstantUsers - If there are any dead constant users dangling
  46 /// off of this global value, remove them.  This method is useful for clients
  47 /// that want to check to see if a global is unused, but don't want to deal
  48 /// with potentially dead constants hanging off of the globals.
  49 void GlobalValue::removeDeadConstantUsers() const {
  50   Value::use_const_iterator I = use_begin(), E = use_end();
  51   Value::use_const_iterator LastNonDeadUser = E;
  52   while (I != E) {
  53     if (const Constant *User = dyn_cast<Constant>(*I)) {
  54       if (!removeDeadUsersOfConstant(User)) {
  55         // If the constant wasn't dead, remember that this was the last live use
  56         // and move on to the next constant.
  57         LastNonDeadUser = I;
  58         ++I;
  59       } else {
  60         // If the constant was dead, then the iterator is invalidated.
  61         if (LastNonDeadUser == E) {
  62           I = use_begin();
  63           if (I == E) break;
  64         } else {
  65           I = LastNonDeadUser;
  66           ++I;
  67         }
  68       }
  69     } else {
  70       LastNonDeadUser = I;
  71       ++I;
  72     }
  73   }
  74 }
  75
  76 /// Override destroyConstant to make sure it doesn't get called on
  77 /// GlobalValue's because they shouldn't be treated like other constants.
  78 void GlobalValue::destroyConstant() {
  79   assert(0 && "You can't GV->destroyConstant()!");
  80   abort();
  81 }
  82
  83 /// copyAttributesFrom - copy all additional attributes (those not needed to
  84 /// create a GlobalValue) from the GlobalValue Src to this one.
  85 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) {
  86   setAlignment(Src->getAlignment());
  87   setSection(Src->getSection());
  88   setVisibility(Src->getVisibility());
  89 }
  90
  91
  92 //===----------------------------------------------------------------------===//
  93 // GlobalVariable Implementation
  94 //===----------------------------------------------------------------------===//
  95
  96 GlobalVariable::GlobalVariable(const Type *Ty, bool constant, LinkageTypes Link,
  97                                Constant *InitVal, const std::string &Name,
  98                                Module *ParentModule, bool ThreadLocal,
  99                                unsigned AddressSpace)
 100   : GlobalValue(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
 101                 OperandTraits<GlobalVariable>::op_begin(this),
 102                 InitVal != 0, Link, Name),
 103     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
 104   if (InitVal) {
 105     assert(InitVal->getType() == Ty &&
 106            "Initializer should be the same type as the GlobalVariable!");
 107     Op<0>() = InitVal;
 108   }
 109
 110   LeakDetector::addGarbageObject(this);
 111
 112   if (ParentModule)
 113     ParentModule->getGlobalList().push_back(this);
 114 }
 115
 116 GlobalVariable::GlobalVariable(const Type *Ty, bool constant, LinkageTypes Link,
 117                                Constant *InitVal, const std::string &Name,
 118                                GlobalVariable *Before, bool ThreadLocal,
 119                                unsigned AddressSpace)
 120   : GlobalValue(PointerType::get(Ty, AddressSpace), Value::GlobalVariableVal,
 121                 OperandTraits<GlobalVariable>::op_begin(this),
 122                 InitVal != 0, Link, Name),
 123     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
 124   if (InitVal) {
 125     assert(InitVal->getType() == Ty &&
 126            "Initializer should be the same type as the GlobalVariable!");
 127     Op<0>() = InitVal;
 128   }
 129
 130   LeakDetector::addGarbageObject(this);
 131
 132   if (Before)
 133     Before->getParent()->getGlobalList().insert(Before, this);
 134 }
 135
 136 void GlobalVariable::setParent(Module *parent) {
 137   if (getParent())
 138     LeakDetector::addGarbageObject(this);
 139   Parent = parent;
 140   if (getParent())
 141     LeakDetector::removeGarbageObject(this);
 142 }
 143
 144 void GlobalVariable::removeFromParent() {
 145   getParent()->getGlobalList().remove(this);
 146 }
 147
 148 void GlobalVariable::eraseFromParent() {
 149   getParent()->getGlobalList().erase(this);
 150 }
 151
 152 void GlobalVariable::replaceUsesOfWithOnConstant(Value *From, Value *To,
 153                                                  Use *U) {
 154   // If you call this, then you better know this GVar has a constant
 155   // initializer worth replacing. Enforce that here.
 156   assert(getNumOperands() == 1 &&
 157          "Attempt to replace uses of Constants on a GVar with no initializer");
 158
 159   // And, since you know it has an initializer, the From value better be
 160   // the initializer :)
 161   assert(getOperand(0) == From &&
 162          "Attempt to replace wrong constant initializer in GVar");
 163
 164   // And, you better have a constant for the replacement value
 165   assert(isa<Constant>(To) &&
 166          "Attempt to replace GVar initializer with non-constant");
 167
 168   // Okay, preconditions out of the way, replace the constant initializer.
 169   this->setOperand(0, cast<Constant>(To));
 170 }
 171
 172 /// copyAttributesFrom - copy all additional attributes (those not needed to
 173 /// create a GlobalVariable) from the GlobalVariable Src to this one.
 174 void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) {
 175   assert(isa<GlobalVariable>(Src) && "Expected a GlobalVariable!");
 176   GlobalValue::copyAttributesFrom(Src);
 177   const GlobalVariable *SrcVar = cast<GlobalVariable>(Src);
 178   setThreadLocal(SrcVar->isThreadLocal());
 179 }
 180
 181
 182 //===----------------------------------------------------------------------===//
 183 // GlobalAlias Implementation
 184 //===----------------------------------------------------------------------===//
 185
 186 GlobalAlias::GlobalAlias(const Type *Ty, LinkageTypes Link,
 187                          const std::string &Name, Constant* aliasee,
 188                          Module *ParentModule)
 189   : GlobalValue(Ty, Value::GlobalAliasVal, &Op<0>(), 1, Link, Name) {
 190   LeakDetector::addGarbageObject(this);
 191
 192   if (aliasee)
 193     assert(aliasee->getType() == Ty && "Alias and aliasee types should match!");
 194   Op<0>() = aliasee;
 195
 196   if (ParentModule)
 197     ParentModule->getAliasList().push_back(this);
 198 }
 199
 200 void GlobalAlias::setParent(Module *parent) {
 201   if (getParent())
 202     LeakDetector::addGarbageObject(this);
 203   Parent = parent;
 204   if (getParent())
 205     LeakDetector::removeGarbageObject(this);
 206 }
 207
 208 void GlobalAlias::removeFromParent() {
 209   getParent()->getAliasList().remove(this);
 210 }
 211
 212 void GlobalAlias::eraseFromParent() {
 213   getParent()->getAliasList().erase(this);
 214 }
 215
 216 bool GlobalAlias::isDeclaration() const {
 217   const GlobalValue* AV = getAliasedGlobal();
 218   if (AV)
 219     return AV->isDeclaration();
 220   else
 221     return false;
 222 }
 223
 224 void GlobalAlias::setAliasee(Constant *Aliasee)
 225 {
 226   if (Aliasee)
 227     assert(Aliasee->getType() == getType() &&
 228            "Alias and aliasee types should match!");
 229
 230   setOperand(0, Aliasee);
 231 }
 232
 233 const GlobalValue *GlobalAlias::getAliasedGlobal() const {
 234   const Constant *C = getAliasee();
 235   if (C) {
 236     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
 237       return GV;
 238     else {
 239       const ConstantExpr *CE = 0;
 240       if ((CE = dyn_cast<ConstantExpr>(C)) &&
 241           (CE->getOpcode() == Instruction::BitCast ||
 242            CE->getOpcode() == Instruction::GetElementPtr))
 243         return dyn_cast<GlobalValue>(CE->getOperand(0));
 244       else
 245         assert(0 && "Unsupported aliasee");
 246     }
 247   }
 248   return 0;
 249 }
 250
 251 const GlobalValue *GlobalAlias::resolveAliasedGlobal(bool stopOnWeak) const {
 252   SmallPtrSet<const GlobalValue*, 3> Visited;
 253
 254   // Check if we need to stop early.
 255   if (stopOnWeak && mayBeOverridden())
 256     return this;
 257
 258   const GlobalValue *GV = getAliasedGlobal();
 259   Visited.insert(GV);
 260
 261   // Iterate over aliasing chain, stopping on weak alias if necessary.
 262   while (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV)) {
 263     if (stopOnWeak && GA->mayBeOverridden())
 264       break;
 265
 266     GV = GA->getAliasedGlobal();
 267
 268     if (!Visited.insert(GV))
 269       return NULL;
 270   }
 271
 272   return GV;
 273 }