lib/VMCore/Globals.cpp

   1 //===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by the LLVM research group and is distributed under
   6 // the University of Illinois Open Source 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/Support/LeakDetector.h"
  21 using namespace llvm;
  22
  23 //===----------------------------------------------------------------------===//
  24 //                            GlobalValue Class
  25 //===----------------------------------------------------------------------===//
  26
  27 /// removeDeadUsersOfConstant - If the specified constantexpr is dead, remove
  28 /// it.  This involves recursively eliminating any dead users of the
  29 /// constantexpr.
  30 static bool removeDeadUsersOfConstant(Constant *C) {
  31   if (isa<GlobalValue>(C)) return false; // Cannot remove this
  32
  33   while (!C->use_empty()) {
  34     Constant *User = dyn_cast<Constant>(C->use_back());
  35     if (!User) return false; // Non-constant usage;
  36     if (!removeDeadUsersOfConstant(User))
  37       return false; // Constant wasn't dead
  38   }
  39
  40   C->destroyConstant();
  41   return true;
  42 }
  43
  44 /// removeDeadConstantUsers - If there are any dead constant users dangling
  45 /// off of this global value, remove them.  This method is useful for clients
  46 /// that want to check to see if a global is unused, but don't want to deal
  47 /// with potentially dead constants hanging off of the globals.
  48 void GlobalValue::removeDeadConstantUsers() {
  49   Value::use_iterator I = use_begin(), E = use_end();
  50   Value::use_iterator LastNonDeadUser = E;
  51   while (I != E) {
  52     if (Constant *User = dyn_cast<Constant>(*I)) {
  53       if (!removeDeadUsersOfConstant(User)) {
  54         // If the constant wasn't dead, remember that this was the last live use
  55         // and move on to the next constant.
  56         LastNonDeadUser = I;
  57         ++I;
  58       } else {
  59         // If the constant was dead, then the iterator is invalidated.
  60         if (LastNonDeadUser == E) {
  61           I = use_begin();
  62           if (I == E) break;
  63         } else {
  64           I = LastNonDeadUser;
  65           ++I;
  66         }
  67       }
  68     } else {
  69       LastNonDeadUser = I;
  70       ++I;
  71     }
  72   }
  73 }
  74
  75 /// Override destroyConstant to make sure it doesn't get called on
  76 /// GlobalValue's because they shouldn't be treated like other constants.
  77 void GlobalValue::destroyConstant() {
  78   assert(0 && "You can't GV->destroyConstant()!");
  79   abort();
  80 }
  81
  82 //===----------------------------------------------------------------------===//
  83 // GlobalVariable Implementation
  84 //===----------------------------------------------------------------------===//
  85
  86 GlobalVariable::GlobalVariable(const Type *Ty, bool constant, LinkageTypes Link,
  87                                Constant *InitVal, const std::string &Name,
  88                                Module *ParentModule, bool ThreadLocal)
  89   : GlobalValue(PointerType::get(Ty), Value::GlobalVariableVal,
  90                 &Initializer, InitVal != 0, Link, Name),
  91     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
  92   if (InitVal) {
  93     assert(InitVal->getType() == Ty &&
  94            "Initializer should be the same type as the GlobalVariable!");
  95     Initializer.init(InitVal, this);
  96   } else {
  97     Initializer.init(0, this);
  98   }
  99
 100   LeakDetector::addGarbageObject(this);
 101
 102   if (ParentModule)
 103     ParentModule->getGlobalList().push_back(this);
 104 }
 105
 106 GlobalVariable::GlobalVariable(const Type *Ty, bool constant, LinkageTypes Link,
 107                                Constant *InitVal, const std::string &Name,
 108                                GlobalVariable *Before, bool ThreadLocal)
 109   : GlobalValue(PointerType::get(Ty), Value::GlobalVariableVal,
 110                 &Initializer, InitVal != 0, Link, Name),
 111     isConstantGlobal(constant), isThreadLocalSymbol(ThreadLocal) {
 112   if (InitVal) {
 113     assert(InitVal->getType() == Ty &&
 114            "Initializer should be the same type as the GlobalVariable!");
 115     Initializer.init(InitVal, this);
 116   } else {
 117     Initializer.init(0, this);
 118   }
 119
 120   LeakDetector::addGarbageObject(this);
 121
 122   if (Before)
 123     Before->getParent()->getGlobalList().insert(Before, this);
 124 }
 125
 126 void GlobalVariable::setParent(Module *parent) {
 127   if (getParent())
 128     LeakDetector::addGarbageObject(this);
 129   Parent = parent;
 130   if (getParent())
 131     LeakDetector::removeGarbageObject(this);
 132 }
 133
 134 void GlobalVariable::removeFromParent() {
 135   getParent()->getGlobalList().remove(this);
 136 }
 137
 138 void GlobalVariable::eraseFromParent() {
 139   getParent()->getGlobalList().erase(this);
 140 }
 141
 142 void GlobalVariable::replaceUsesOfWithOnConstant(Value *From, Value *To,
 143                                                  Use *U) {
 144   // If you call this, then you better know this GVar has a constant
 145   // initializer worth replacing. Enforce that here.
 146   assert(getNumOperands() == 1 &&
 147          "Attempt to replace uses of Constants on a GVar with no initializer");
 148
 149   // And, since you know it has an initializer, the From value better be
 150   // the initializer :)
 151   assert(getOperand(0) == From &&
 152          "Attempt to replace wrong constant initializer in GVar");
 153
 154   // And, you better have a constant for the replacement value
 155   assert(isa<Constant>(To) &&
 156          "Attempt to replace GVar initializer with non-constant");
 157
 158   // Okay, preconditions out of the way, replace the constant initializer.
 159   this->setOperand(0, cast<Constant>(To));
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 // GlobalAlias Implementation
 164 //===----------------------------------------------------------------------===//
 165
 166 GlobalAlias::GlobalAlias(const Type *Ty, LinkageTypes Link,
 167                          const std::string &Name, Constant* aliasee,
 168                          Module *ParentModule)
 169   : GlobalValue(Ty, Value::GlobalAliasVal, &Aliasee, 1, Link, Name) {
 170   LeakDetector::addGarbageObject(this);
 171
 172   if (aliasee)
 173     assert(aliasee->getType() == Ty && "Alias and aliasee types should match!");
 174   Aliasee.init(aliasee, this);
 175
 176   if (ParentModule)
 177     ParentModule->getAliasList().push_back(this);
 178 }
 179
 180 void GlobalAlias::setParent(Module *parent) {
 181   if (getParent())
 182     LeakDetector::addGarbageObject(this);
 183   Parent = parent;
 184   if (getParent())
 185     LeakDetector::removeGarbageObject(this);
 186 }
 187
 188 void GlobalAlias::removeFromParent() {
 189   getParent()->getAliasList().remove(this);
 190 }
 191
 192 void GlobalAlias::eraseFromParent() {
 193   getParent()->getAliasList().erase(this);
 194 }
 195
 196 bool GlobalAlias::isDeclaration() const {
 197   const GlobalValue* AV = getAliasedGlobal();
 198   if (AV)
 199     return AV->isDeclaration();
 200   else
 201     return false;
 202 }
 203
 204 void GlobalAlias::setAliasee(Constant *Aliasee)
 205 {
 206   if (Aliasee)
 207     assert(Aliasee->getType() == getType() &&
 208            "Alias and aliasee types should match!");
 209
 210   setOperand(0, Aliasee);
 211 }
 212
 213 const GlobalValue *GlobalAlias::getAliasedGlobal() const {
 214   const Constant *C = getAliasee();
 215   if (C) {
 216     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
 217       return GV;
 218     else {
 219       const ConstantExpr *CE = 0;
 220       if ((CE = dyn_cast<ConstantExpr>(C)) &&
 221           (CE->getOpcode() == Instruction::BitCast ||
 222            CE->getOpcode() == Instruction::GetElementPtr))
 223         return dyn_cast<GlobalValue>(CE->getOperand(0));
 224       else
 225         assert(0 && "Unsupported aliasee");
 226     }
 227   }
 228   return 0;
 229 }
 230