lib/VMCore/Value.cpp

   1 //===-- Value.cpp - Implement the Value 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 Value and User classes.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Constant.h"
  15 #include "llvm/DerivedTypes.h"
  16 #include "llvm/InstrTypes.h"
  17 #include "llvm/Module.h"
  18 #include "llvm/SymbolTable.h"
  19 #include "llvm/Support/LeakDetector.h"
  20 #include <algorithm>
  21 #include <iostream>
  22 using namespace llvm;
  23
  24 //===----------------------------------------------------------------------===//
  25 //                                Value Class
  26 //===----------------------------------------------------------------------===//
  27
  28 static inline const Type *checkType(const Type *Ty) {
  29   assert(Ty && "Value defined with a null type: Error!");
  30   return Ty;
  31 }
  32
  33 Value::Value(const Type *ty, unsigned scid, const std::string &name)
  34   : SubclassID(scid), SubclassData(0), Ty(checkType(ty)),
  35     UseList(0), Name(name) {
  36   if (!isa<Constant>(this) && !isa<BasicBlock>(this))
  37     assert((Ty->isFirstClassType() || Ty == Type::VoidTy ||
  38            isa<OpaqueType>(ty)) &&
  39            "Cannot create non-first-class values except for constants!");
  40   if (ty == Type::VoidTy)
  41     assert(name.empty() && "Cannot have named void values!");
  42 }
  43
  44 Value::~Value() {
  45 #ifndef NDEBUG      // Only in -g mode...
  46   // Check to make sure that there are no uses of this value that are still
  47   // around when the value is destroyed.  If there are, then we have a dangling
  48   // reference and something is wrong.  This code is here to print out what is
  49   // still being referenced.  The value in question should be printed as
  50   // a <badref>
  51   //
  52   if (use_begin() != use_end()) {
  53     std::cerr << "While deleting: " << *Ty << " %" << Name << "\n";
  54     for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
  55       std::cerr << "Use still stuck around after Def is destroyed:"
  56                 << **I << "\n";
  57   }
  58 #endif
  59   assert(use_begin() == use_end() && "Uses remain when a value is destroyed!");
  60
  61   // There should be no uses of this object anymore, remove it.
  62   LeakDetector::removeGarbageObject(this);
  63 }
  64
  65 /// hasNUses - Return true if this Value has exactly N users.
  66 ///
  67 bool Value::hasNUses(unsigned N) const {
  68   use_const_iterator UI = use_begin(), E = use_end();
  69
  70   for (; N; --N, ++UI)
  71     if (UI == E) return false;  // Too few.
  72   return UI == E;
  73 }
  74
  75 /// hasNUsesOrMore - Return true if this value has N users or more.  This is
  76 /// logically equivalent to getNumUses() >= N.
  77 ///
  78 bool Value::hasNUsesOrMore(unsigned N) const {
  79   use_const_iterator UI = use_begin(), E = use_end();
  80
  81   for (; N; --N, ++UI)
  82     if (UI == E) return false;  // Too few.
  83
  84   return true;
  85 }
  86
  87
  88 /// getNumUses - This method computes the number of uses of this Value.  This
  89 /// is a linear time operation.  Use hasOneUse or hasNUses to check for specific
  90 /// values.
  91 unsigned Value::getNumUses() const {
  92   return (unsigned)std::distance(use_begin(), use_end());
  93 }
  94
  95
  96 void Value::setName(const std::string &name) {
  97   if (Name == name) return;   // Name is already set.
  98
  99   // Get the symbol table to update for this object.
 100   SymbolTable *ST = 0;
 101   if (Instruction *I = dyn_cast<Instruction>(this)) {
 102     if (BasicBlock *P = I->getParent())
 103       if (Function *PP = P->getParent())
 104         ST = &PP->getSymbolTable();
 105   } else if (BasicBlock *BB = dyn_cast<BasicBlock>(this)) {
 106     if (Function *P = BB->getParent()) ST = &P->getSymbolTable();
 107   } else if (GlobalValue *GV = dyn_cast<GlobalValue>(this)) {
 108     if (Module *P = GV->getParent()) ST = &P->getSymbolTable();
 109   } else if (Argument *A = dyn_cast<Argument>(this)) {
 110     if (Function *P = A->getParent()) ST = &P->getSymbolTable();
 111   } else {
 112     assert(isa<Constant>(this) && "Unknown value type!");
 113     return;  // no name is setable for this.
 114   }
 115
 116   if (!ST)  // No symbol table to update?  Just do the change.
 117     Name = name;
 118   else if (hasName()) {
 119     if (!name.empty()) {    // Replacing name.
 120       ST->changeName(this, name);
 121     } else {                // Transitioning from hasName -> noname.
 122       ST->remove(this);
 123       Name.clear();
 124     }
 125   } else {                  // Transitioning from noname -> hasName.
 126     Name = name;
 127     ST->insert(this);
 128   }
 129 }
 130
 131 // uncheckedReplaceAllUsesWith - This is exactly the same as replaceAllUsesWith,
 132 // except that it doesn't have all of the asserts.  The asserts fail because we
 133 // are half-way done resolving types, which causes some types to exist as two
 134 // different Type*'s at the same time.  This is a sledgehammer to work around
 135 // this problem.
 136 //
 137 void Value::uncheckedReplaceAllUsesWith(Value *New) {
 138   while (!use_empty()) {
 139     Use &U = *UseList;
 140     // Must handle Constants specially, we cannot call replaceUsesOfWith on a
 141     // constant!
 142     if (Constant *C = dyn_cast<Constant>(U.getUser())) {
 143       if (!isa<GlobalValue>(C))
 144         C->replaceUsesOfWithOnConstant(this, New, &U);
 145       else
 146         U.set(New);
 147     } else {
 148       U.set(New);
 149     }
 150   }
 151 }
 152
 153 void Value::replaceAllUsesWith(Value *New) {
 154   assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
 155   assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
 156   assert(New->getType() == getType() &&
 157          "replaceAllUses of value with new value of different type!");
 158
 159   uncheckedReplaceAllUsesWith(New);
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 //                                 User Class
 164 //===----------------------------------------------------------------------===//
 165
 166 // replaceUsesOfWith - Replaces all references to the "From" definition with
 167 // references to the "To" definition.
 168 //
 169 void User::replaceUsesOfWith(Value *From, Value *To) {
 170   if (From == To) return;   // Duh what?
 171
 172   assert(!isa<Constant>(this) || isa<GlobalValue>(this) &&
 173          "Cannot call User::replaceUsesofWith on a constant!");
 174
 175   for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
 176     if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
 177       // The side effects of this setOperand call include linking to
 178       // "To", adding "this" to the uses list of To, and
 179       // most importantly, removing "this" from the use list of "From".
 180       setOperand(i, To); // Fix it now...
 181     }
 182 }
 183