llvm/lib/VMCore/Value.cpp

//===-- Value.cpp - Implement the Value class -----------------------------===//
//
// This file implements the Value and User classes. 
//
//===----------------------------------------------------------------------===//

#include "llvm/InstrTypes.h"
#include "llvm/SymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "Support/LeakDetector.h"
#include <algorithm>

//===----------------------------------------------------------------------===//
//                                Value Class
//===----------------------------------------------------------------------===//

static inline const Type *checkType(const Type *Ty) {
  assert(Ty && "Value defined with a null type: Error!");
  return Ty;
}

Value::Value(const Type *ty, ValueTy vty, const std::string &name)
  : Name(name), Ty(checkType(ty), this) {
  VTy = vty;
}

Value::~Value() {
#ifndef NDEBUG      // Only in -g mode...
  // Check to make sure that there are no uses of this value that are still
  // around when the value is destroyed.  If there are, then we have a dangling
  // reference and something is wrong.  This code is here to print out what is
  // still being referenced.  The value in question should be printed as 
  // a <badref>
  //
  if (Uses.begin() != Uses.end()) {
    std::cerr << "While deleting: " << Ty << "%" << Name << "\n";
    for (use_const_iterator I = Uses.begin(); I != Uses.end(); ++I)
      std::cerr << "Use still stuck around after Def is destroyed:"
                << **I << "\n";
  }
#endif
  assert(Uses.begin() == Uses.end());

  // There should be no uses of this object anymore, remove it.
  LeakDetector::removeGarbageObject(this);
}

void Value::replaceAllUsesWith(Value *D) {
  assert(D && "Value::replaceAllUsesWith(<null>) is invalid!");
  assert(D != this && "V->replaceAllUsesWith(V) is NOT valid!");
  assert(D->getType() == getType() &&
         "replaceAllUses of value with new value of different type!");
  while (!Uses.empty()) {
    User *Use = Uses.back();
#ifndef NDEBUG
    unsigned NumUses = Uses.size();
#endif
    Use->replaceUsesOfWith(this, D);

#ifndef NDEBUG      // only in -g mode...
    if (Uses.size() == NumUses)
      std::cerr << "Use: " << *Use << "replace with: " << *D;
#endif
    assert(Uses.size() != NumUses && "Didn't remove definition!");
  }
}

// refineAbstractType - This function is implemented because we use
// potentially abstract types, and these types may be resolved to more
// concrete types after we are constructed.  For the value class, we simply
// change Ty to point to the right type.  :)
//
void Value::refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
  assert(Ty.get() == OldTy && "Can't refine anything but my type!");
  if (OldTy == NewTy && !OldTy->isAbstract())
    Ty.removeUserFromConcrete();
  Ty = NewTy;
}

void Value::killUse(User *U) {
  if (U == 0) return;
  unsigned i;

  // Scan backwards through the uses list looking for the user.  We do this
  // because vectors like to be accessed on the end.  This is incredibly
  // important from a performance perspective.
  for (i = Uses.size()-1; Uses[i] != U; --i)
    /* empty */;

  assert(i < Uses.size() && "Use not in uses list!!");
  Uses.erase(Uses.begin()+i);
}

//===----------------------------------------------------------------------===//
//                                 User Class
//===----------------------------------------------------------------------===//

User::User(const Type *Ty, ValueTy vty, const std::string &name) 
  : Value(Ty, vty, name) {
}

// replaceUsesOfWith - Replaces all references to the "From" definition with
// references to the "To" definition.
//
void User::replaceUsesOfWith(Value *From, Value *To) {
  if (From == To) return;   // Duh what?

  for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
    if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
      // The side effects of this setOperand call include linking to
      // "To", adding "this" to the uses list of To, and
      // most importantly, removing "this" from the use list of "From".
      setOperand(i, To); // Fix it now...
    }
}