Beispiel #1
0
/// OptimizeGlobals - This method uses information taken from DSA to optimize
/// global variables.
///
bool DSOpt::OptimizeGlobals(Module &M) {
  DSGraph* GG = TD->getGlobalsGraph();
  const DSGraph::ScalarMapTy &SM = GG->getScalarMap();
  bool Changed = false;

  for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
    if (!I->isDeclaration()) { // Loop over all of the non-external globals...
      // Look up the node corresponding to this global, if it exists.
      DSNode *GNode = 0;
      DSGraph::ScalarMapTy::const_iterator SMI = SM.find(I);
      if (SMI != SM.end()) GNode = SMI->second.getNode();

      if (GNode == 0 && I->hasInternalLinkage()) {
        // If there is no entry in the scalar map for this global, it was never
        // referenced in the program.  If it has internal linkage, that means we
        // can delete it.  We don't ACTUALLY want to delete the global, just
        // remove anything that references the global: later passes will take
        // care of nuking it.
        if (!I->use_empty()) {
          I->replaceAllUsesWith(ConstantPointerNull::get(I->getType()));
          ++NumGlobalsIsolated;
        }
      } else if (GNode && GNode->NodeType.isCompleteNode()) {

        // If the node has not been read or written, and it is not externally
        // visible, kill any references to it so it can be DCE'd.
        if (!GNode->NodeType.isModifiedNode() && !GNode->NodeType.isReadNode() &&I->hasInternalLinkage()){
          if (!I->use_empty()) {
            I->replaceAllUsesWith(ConstantPointerNull::get(I->getType()));
            ++NumGlobalsIsolated;
          }
        }

        // We expect that there will almost always be a node for this global.
        // If there is, and the node doesn't have the M bit set, we can set the
        // 'constant' bit on the global.
        if (!GNode->NodeType.isModifiedNode() && !I->isConstant()) {
          I->setConstant(true);
          ++NumGlobalsConstanted;
          Changed = true;
        }
      }
    }
  return Changed;
}
Beispiel #2
0
bool StripExternals::runOnModule(Module &M) {
  bool Changed = false;

  for (Module::iterator I = M.begin(); I != M.end(); ) {
    if (I->hasAvailableExternallyLinkage()) {
      assert(!I->isDeclaration()&&"Declarations can't be available_externally");
      Changed = true;
      ++NumFunctions;
      if (I->use_empty()) {
        DEBUG(errs() << "Deleting function: " << *I);
        Module::iterator todelete = I;
        ++I;
        todelete->eraseFromParent();
        continue;
      } else {
        I->deleteBody();
        DEBUG(errs() << "Deleted function body: " << *I);
      }
    }
    ++I;
  }

  for (Module::global_iterator I = M.global_begin();
       I != M.global_end(); ) {
    if (I->hasAvailableExternallyLinkage()) {
      assert(!I->isDeclaration()&&"Declarations can't be available_externally");
      Changed = true;
      ++NumVariables;
      if (I->use_empty()) {
        DEBUG(errs() << "Deleting global: " << *I);
        Module::global_iterator todelete = I;
        ++I;
        todelete->eraseFromParent();
        continue;
      } else {
        I->setInitializer(0);
        I->setLinkage(GlobalValue::ExternalLinkage);
        DEBUG(errs() << "Deleted initializer: " << *I);
      }
    }
    ++I;
  }

  return Changed;
}