ManagerCFG.cpp

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// standard headers

#ifdef NO_STD_CHEADERS
# include <stdlib.h>
# include <string.h>
# include <assert.h>
#else
# include <cstdlib>
# include <cstring>
# include <cassert>
using namespace std; // For compatibility with non-std C headers
#endif

#include <iostream>
using std::ostream;
using std::endl;
using std::cout;
using std::cerr;
#include <list>
#include <set>
#include <map>

// Mint headers
#include "ManagerCFG.hpp"


namespace OA {
  namespace CFG {

static bool debug = false;

  ManagerCFGStandard::ManagerCFGStandard (OA_ptr<CFGIRInterface> _ir,
                                bool _build_stmt_level_cfg /* = false */ )
        : mIR(_ir), mBuildStmtLevelCFG(_build_stmt_level_cfg)
        {
 
       
             OA_DEBUG_CTRL_MACRO("DEBUG_ManagerCFG:ALL", debug);
             mFallThrough.clear();
        }


  OA_ptr<CFG::CFG> ManagerCFGStandard::performAnalysis(ProcHandle proc)
  {
    // get information from the ir interface
    bool return_statements_allowed = mIR->returnStatementsAllowed();
    // create a CFG that just has an entry and an exit node
    mCFG = new CFG();
    OA_ptr<NodesIteratorInterface> nodes_iter;
    // Create the unique entry node.
    OA_ptr<Node> entry; 
    entry = new Node();
    mCFG->setEntry(entry);
    mCFG->addNode(entry);

    // Create the actual start node where the first statements wil be added.
    OA_ptr<Node> r; r = new Node();
    mCFG->addNode(r);
    mCFG->connect (mCFG->getEntry(), r, FALLTHROUGH_EDGE);
    CFG::NodeLabelList exit_nodes;
    // some NodeLabelList's are OA_ptr's instead of passed around by reference
    // because some of the logic looks to see if the list is NULL
    OA_ptr<CFG::NodeLabelList> return_nodes;
    return_nodes = new CFG::NodeLabelList;
    OA_ptr<IRRegionStmtIterator> stmt_iterptr = mIR->procBody(proc);
    OA_ptr<CFG::NodeLabelList> nullList; nullList = NULL;

    if (return_statements_allowed) {
      build_block(r, stmt_iterptr, exit_nodes, nullList, return_nodes, nullList);
    } else {
      build_block(r, stmt_iterptr, exit_nodes, nullList, nullList, nullList);
    }

    // create unique exit node
    OA_ptr<Node> final; final = new Node();
    mCFG->addNode(final);
    mCFG->setExit(final);
    // connect the exit nodes to the final node
    mCFG->connect(exit_nodes, final);
    // return nodes also lead to the exit node of the sub-program
    mCFG->connect(*return_nodes, final);
    // finalize control flow for unstructured constructs
    HandleDelayedBranches();
    return mCFG;

  }


  //--------------------------------------------------------------------
  IRStmtType
  ManagerCFGStandard::build_block (OA_ptr<Node> prev_node,
                                OA_ptr<IRRegionStmtIterator> si_ptr,
                                std::list<CFG::NodeLabel>& exit_nodes,
                                OA_ptr<std::list<CFG::NodeLabel> > break_nodes,
                                OA_ptr<std::list<CFG::NodeLabel> > return_nodes,
                                OA_ptr<std::list<CFG::NodeLabel> > continue_nodes)
  {
      std::list<CFG::NodeLabel> x_nodes;

      IRStmtType prev_statement = SIMPLE;
      while (si_ptr->isValid()) {
        StmtHandle stmt = si_ptr->current();
        if (debug) { std::cout << mIR->toString(stmt) << std::endl; }
       
        if (mIR->getLabel(stmt)) {
            StmtLabel lab = mIR->getLabel(stmt);
            OA_ptr<Node> new_node;
         
            if (mCFG->isLabelMappedToNode(lab)) {
                new_node = mCFG->node_from_label(lab);
            } else if (! prev_node->empty()) {
                new_node = new Node();
                mCFG->addNode(new_node);
                if(debug) {
                    cout << "\nCFG Node";
                    new_node->dump(cout , mIR);
                    cout << "\n";
                }
                mCFG->mapLabelToNode(lab,new_node);

            } else {
                mCFG->mapLabelToNode(lab,prev_node);
                new_node = prev_node;
            }

            if (prev_statement != SIMPLE && !new_node.ptrEqual(prev_node)) {
                mCFG->connect(x_nodes, new_node);
            } else if (!prev_node.ptrEqual(NULL)
                     && !new_node.ptrEqual(prev_node))
            {
                mCFG->connect(prev_node, new_node, FALLTHROUGH_EDGE);
            }
            x_nodes.clear();
            prev_node = new_node;
      
                  
         } else if (mBuildStmtLevelCFG) {
            if (!prev_node->empty()) {
                OA_ptr<Node> new_node;
                new_node = new Node();
                mCFG->addNode(new_node);
                if(debug) {
                    cout << "\n CFG Node";
                    new_node->dump(cout , mIR);
                    cout << "\n";
                }

               
                if (prev_statement == SIMPLE) {
                    mCFG->connect(prev_node, new_node, FALLTHROUGH_EDGE);
                } else {
                   mCFG->connect(x_nodes, new_node);
                }
                prev_node = new_node;
            }  
            x_nodes.clear();

         } else if (prev_statement != SIMPLE) {
            // now we need to create a new CFG node
            prev_node = new Node();
            mCFG->addNode(prev_node);
            if(debug) {
                 cout << "\n CFG Node";
                 prev_node->dump(cout , mIR);
                 cout << "\n";
            }


            mCFG->connect(x_nodes, prev_node);
            x_nodes.clear();
         }
         prev_statement = build_stmt(prev_node, stmt, x_nodes, break_nodes,
                                                      return_nodes, continue_nodes);
         ++(*si_ptr);
      }  

       
      if (prev_statement == SIMPLE) {
        exit_nodes.push_back(CFG::NodeLabel(prev_node,
                         FALLTHROUGH_EDGE));
      } else {
        CFG::NodeLabelListIterator x_nodes_iter(x_nodes);
        while (x_nodes_iter.isValid()) {
          exit_nodes.push_back(x_nodes_iter.current());
          ++x_nodes_iter;
        }
      }
      
      return NONE;
  }


  //--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_stmt (OA_ptr<Node> prev_node,
    OA::StmtHandle stmt,
    std::list<CFG::NodeLabel>& exit_nodes,
    OA_ptr<std::list<CFG::NodeLabel> > break_nodes,
    OA_ptr<std::list<CFG::NodeLabel> > return_nodes,
    OA_ptr<std::list<CFG::NodeLabel> > continue_nodes)
{
    switch (mIR->getCFGStmtType(stmt)) {
       case SIMPLE:
         {
            prev_node->add(stmt);
            if (debug) { std::cout << mIR->toString(stmt) << std::endl; }
            return SIMPLE;
         }
       case COMPOUND:
         {
            build_block(prev_node, mIR->getFirstInCompound(stmt), exit_nodes,
            break_nodes, return_nodes, continue_nodes);
            return COMPOUND;
         }
       case BREAK:
         {
            prev_node->add(stmt);
            if (break_nodes.ptrEqual(0)) {
               //  throw Unexpected_Break();
            } else {
               break_nodes->push_back(CFG::NodeLabel(prev_node,
                               BREAK_EDGE));
            }
            return BREAK;
         }
       case RETURN:
         {
            prev_node->add(stmt);
            if (return_nodes.ptrEqual(0)) {
               //throw Unexpected_Return();
            } else {
              return_nodes->push_back(CFG::NodeLabel(prev_node,
                                RETURN_EDGE));
            }
           return RETURN;
         }
       case LOOP:
       {
           return build_CFG_loop (prev_node, stmt, exit_nodes, return_nodes);
       }
 
       case STRUCT_TWOWAY_CONDITIONAL:
       {
           return build_CFG_twoway_branch (prev_node, stmt, exit_nodes, break_nodes,
                                      return_nodes, continue_nodes);
       }

       case STRUCT_MULTIWAY_CONDITIONAL:
       {
            if (mIR->isBreakImplied(stmt)) {
                return build_CFG_multiway_branch (prev_node, stmt, exit_nodes,
                                          break_nodes, return_nodes,
                                          continue_nodes);
            }else {
                return build_CFG_multiway_branch_with_fallthrough (prev_node, stmt,                                           exit_nodes, return_nodes, continue_nodes);
            }
            
       } 

       case END_TESTED_LOOP:
       {
            return build_CFG_end_tested_loop (prev_node, stmt, exit_nodes, return_nodes);
       }
      
       case LOOP_CONTINUE:
       {
            prev_node->add(stmt);
            if (continue_nodes.ptrEqual(0)) {
      //         throw Unexpected_Continue();
            } else {
                 continue_nodes->push_back(CFG::NodeLabel(prev_node,
                                  CONTINUE_EDGE));
            }
            return LOOP_CONTINUE;
       }
       //
       // These unstructured constructs have the possibility of being
       // delayed branches (depending on the underlying machine). Those
       // without delay slots are handled now.  Those with delay slots
       // are just added as simple statements.  A post-processing step
       // will finalize control flow for them.
       //
       case UNCONDITIONAL_JUMP:
       {
            if (mIR->numberOfDelaySlots(stmt) == 0) {
                return build_CFG_unconditional_jump (prev_node, stmt);
            } else {
                prev_node->add(stmt);
                return SIMPLE;
            }
       }
       case USTRUCT_TWOWAY_CONDITIONAL_T:
       case USTRUCT_TWOWAY_CONDITIONAL_F:
       {
             if (mIR->numberOfDelaySlots(stmt) == 0) {
                return build_CFG_ustruct_twoway_branch (prev_node, stmt, exit_nodes);
             } else {
                prev_node->add(stmt);
                return SIMPLE;
             }
       }
      case UNCONDITIONAL_JUMP_I:
       {
            if (mIR->numberOfDelaySlots(stmt) == 0) {
                return build_CFG_unconditional_jump_i (prev_node, stmt);
            } else {
                prev_node->add(stmt);
                return SIMPLE;
            }
       }
      case USTRUCT_MULTIWAY_CONDITIONAL:
       {    
           // Currently assume multiways don't have delay slots.
           assert(mIR->numberOfDelaySlots(stmt) == 0);
           return build_CFG_ustruct_multiway_branch (prev_node, stmt);
       }
           // FIXME: Unimplemented.
      case ALTERNATE_PROC_ENTRY:
       {
           cout << "FIXME: ALTERNATE_PROC_ENTRY not yet implemented" << endl;
           assert (0);
           return ALTERNATE_PROC_ENTRY;
       }
    default:
       {
           assert (0);
       }

 
    }
}


IRStmtType
ManagerCFGStandard::build_CFG_loop(OA_ptr<Node> prev_node,
                                StmtHandle th,
                                std::list<CFG::NodeLabel>& exit_nodes,
                                OA_ptr<std::list<CFG::NodeLabel> > return_nodes)
{
    // If there is a header, (as in a "for" loop), it is assimilated in the
  // previous (prev_node) CFG node.  The condition needs a separate CFG node.
  // So, unless prev_node is empty (in which case that can become the
  // condition node) a new CFG node must be allocated for the loop condition.
  OA_ptr<Node> c;

  StmtHandle header = mIR->loopHeader(th);
  if (header) {
    prev_node->add(header);
  }

  // To handle C and Fortran loops in the simplest way we take the following
  // measures:
  //
  // If the number of loop iterations is defined
  // at loop entry (i.e. Fortran semantics), we add the loop statement
  // representative to the header node so that definitions from inside
  // the loop don't reach the condition and increment specifications
  // in the loop statement.
  //
  // On the other hand, if the number of iterations is not defined at
  // entry (i.e. C semantics), we add the loop statement to a node that
  // is inside the loop in the CFG so definitions inside the loop will
  // reach uses in the conditional test. for C style semantics, the
  // increment itself may be a separate statement. if so, it will appear
  // explicitly at the bottom of the loop.

  bool definedAtEntry =  mIR->loopIterationsDefinedAtEntry(th);
  if (definedAtEntry) {
    prev_node->add(th);
  }
  if (prev_node->empty()) {
    prev_node->add(th);
    c = prev_node;
  }
  else {
    c = new Node(th);
    mCFG->addNode(c);
    mCFG->connect(prev_node, c, FALLTHROUGH_EDGE);
  }
  exit_nodes.push_back(CFG::NodeLabel(c, FALSE_EDGE));

  // allocate a new CFG node for the loop body and recur
  std::list<CFG::NodeLabel> x_nodes;
  OA_ptr<IRRegionStmtIterator> body = mIR->loopBody(th);
  if (body->isValid() && body->current()) {
    OA_ptr<Node> b; 
    b = new Node();
    mCFG->addNode(b);

    if(debug)
    {
                 cout << "\n CFG Node";
                 b->dump(cout , mIR);
                 cout << "\n";
    }

 

    
    OA_ptr<std::list<CFG::NodeLabel> > break_statements, continue_statements;
    break_statements = new std::list<CFG::NodeLabel>;
    continue_statements = new std::list<CFG::NodeLabel>;
    if (build_block(b, body, x_nodes, break_statements, return_nodes,
                    continue_statements) == SIMPLE)
    {
      x_nodes.push_back(CFG::NodeLabel(b, FALLTHROUGH_EDGE));
    }

    mCFG->connect(c, b, TRUE_EDGE);
    CFG::NodeLabelListIterator break_iter(*break_statements);
    while (break_iter.isValid()) {
      exit_nodes.push_back(break_iter.current());
      ++break_iter;
    }

    CFG::NodeLabelListIterator continue_iter(*continue_statements);
    while (continue_iter.isValid()) {
      x_nodes.push_back(continue_iter.current());
      ++continue_iter;
    }
  }  else {// empty body
    x_nodes.push_back(CFG::NodeLabel(c, TRUE_EDGE));
  }

  // allocate a new CFG node for the increment part, if needed
  StmtHandle incr = mIR->getLoopIncrement(th);
  if (incr) {
    OA_ptr<Node> li; 
    li = new Node(incr);
    mCFG->addNode(li);
    mCFG->connect(x_nodes, li);
    mCFG->connect(li, c, FALLTHROUGH_EDGE);
  }
  else {
    mCFG->connect(x_nodes, c);
  }

  return LOOP;

 
}


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_twoway_branch (OA_ptr<Node> prev_node,
        StmtHandle th, std::list<CFG::NodeLabel>& exit_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > break_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > return_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > continue_nodes)
{

  if(debug)
  {
      std::cout << "Inside CFG::build_CFG_twoway_branch" << endl;
  }
 // add the if statement itself to the previous block. it represents
  // the conditional branch terminating the block.
  prev_node->add(th);

  // construct the CFG for the true block
  OA_ptr<Node> b;
  OA_ptr<IRRegionStmtIterator> true_body = mIR->trueBody(th);
  if (true_body->isValid() && true_body->current()) {
    b = new Node();

    if(debug)
    {
        std::cout << "True branch" << std::endl;
    }

    if(debug)
   {
       std::cout << "In CFG addNode" << std::endl;
       b->dump(cout , mIR);
   }

   mCFG->addNode(b);

   if(debug)
   {
       std::cout << "CFG addNode ends" << std::endl;
   }

    
    if (build_block(b, true_body, exit_nodes, break_nodes, return_nodes, continue_nodes) == SIMPLE)
      exit_nodes.push_back(CFG::NodeLabel(b, FALLTHROUGH_EDGE));

    mCFG->connect(prev_node, b, TRUE_EDGE);
  }
  else {
    // the body is empty
    b = 0;
    exit_nodes.push_back(CFG::NodeLabel(prev_node, TRUE_EDGE));
  }

 // handle the false block
  OA_ptr<IRRegionStmtIterator> false_body = mIR->elseBody(th);
  if (false_body->isValid() && false_body->current()) {
    OA_ptr<Node> c_body; c_body = new Node();
    if(debug)
    {
        std::cout << "false branch" << std::endl;
    }

    if(debug)
    {
       std::cout << "In CFG addNode" << std::endl;
       c_body->dump(cout , mIR);
    }

    mCFG->addNode(c_body);

    if(debug)
    {
      std::cout << "CFG addNode ends" << std::endl;
    }

    
    if (build_block(c_body, false_body, exit_nodes, break_nodes, return_nodes, continue_nodes) == SIMPLE)
      exit_nodes.push_back(CFG::NodeLabel(c_body, FALLTHROUGH_EDGE));

    mCFG->connect(prev_node, c_body, FALSE_EDGE);
  }
  else if (!b.ptrEqual(0)) // if b is 0 then the "condition" node has already been added to exit_nodes
    exit_nodes.push_back(CFG::NodeLabel(prev_node, FALSE_EDGE));

  return STRUCT_TWOWAY_CONDITIONAL;

  if(debug)
  {
      std::cout << "*****  CFG::build_CFG_twoway_branch *****" << endl;
  }
  
}


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_multiway_branch (OA_ptr<Node> prev_node,
        StmtHandle th, std::list<CFG::NodeLabel>& exit_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > break_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > return_nodes,
        OA_ptr<std::list<CFG::NodeLabel> > continue_nodes)
{
   // add the switch statement to the previous block. the switch statement
  // represents the multi-way conditional branch terminating the block.
  prev_node->add(th);

  bool direct_drop = false;    // should there be a direct edge from the condition to exit?
  bool default_cond = false;   // is there a default case?

  // iterate over the multi-branches
  for (int bridx = 0; bridx < mIR->numMultiCases(th); bridx++) {
    OA_ptr<IRRegionStmtIterator> body = mIR->multiBody(th, bridx);

    // if there is an empty body then just make a direct drop, this is correct since
    // break is always implied
    if (body->isValid() && body->current()) {
      OA_ptr<Node> c; c = new Node();
      mCFG->addNode(c);

 if(debug)
                {
                 cout << "\n build_CFG_multiway_branch CFG Node";
                 c->dump(cout , mIR);
                 cout << "\n";
                }


      if (build_block(c, body, exit_nodes, break_nodes, return_nodes, continue_nodes) == SIMPLE)
      {
        exit_nodes.push_back(CFG::NodeLabel(c, FALLTHROUGH_EDGE));
      }

       // check if this is the catch all case
       if (mIR->isCatchAll(th,bridx)) {
           default_cond = true;
           mCFG->connect(prev_node, c, MULTIWAY_EDGE);
       } else {
           ExprHandle multiCond = mIR->getSMultiCondition(th, bridx);
           mCFG->connect(prev_node, c, MULTIWAY_EDGE, multiCond);
       }
       
       // there is an empty body with an implied break
     } else {
           direct_drop = true;
     }
  
   } /* for */

   // if we didn't find a catchall then there should be a direct drop
   if (default_cond == false) {
       direct_drop = true;
   }
   
   // direct drop is true iff there is not catchall or at least one multi-branch body is null
   if (direct_drop) {
       exit_nodes.push_back(CFG::NodeLabel(prev_node, FALLTHROUGH_EDGE));
   }
   
   return STRUCT_MULTIWAY_CONDITIONAL;

}


//--------------------------------------------------------------------


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_multiway_branch_with_fallthrough (
       OA_ptr<Node> prev_node,
       StmtHandle th, std::list<CFG::NodeLabel>& exit_nodes,
       OA_ptr<std::list<CFG::NodeLabel> > return_nodes,
       OA_ptr<std::list<CFG::NodeLabel> > continue_nodes)
{
     // add the switch statement to the previous block. the switch statement
     // represents the multi-way conditional branch terminating the block.
     prev_node->add(th);
     
     //bool direct_drop = true;   // should there be a direct edge from the condition to exit?
     bool empty_cond = false;     // is there an empty case?
     bool default_cond = false;   // is there a default case
    
    // We must create a new list of break statements since any breaks seen
    // in subtrees of this statement will exit this switch, not some other
    // enclosing construct.
    OA_ptr<std::list<CFG::NodeLabel> > break_switch_statements;
    break_switch_statements = new std::list<CFG::NodeLabel>;

   // Track the last case body processed so that fall-through
   // connections can be made This will be non-null whenever the
   // previous case falls through (i.e., did not end in a break
   // statement).  the case_exit_nodes list will contain all the exits
   // from the previous case block
   OA_ptr<Node> prev_case_node;
   prev_case_node = 0;
   std::list<CFG::NodeLabel> case_exit_nodes;

   // iterate over the multi-branches
   for (int bridx = 0; bridx < mIR->numMultiCases(th); bridx++) {

    OA_ptr<IRRegionStmtIterator> body = mIR->multiBody(th, bridx);
    //if (body->isValid() && body->current()) {
    OA_ptr<Node> c; c = new Node();
    mCFG->addNode(c);

 if(debug)
                {
                 cout << "\n Add CFG multiway branch with_Fallthrough CFG Node";
                 c->dump(cout , mIR);
                 cout << "\n";
                }


    
    break_switch_statements->clear();
    // If a previous case falls-through, connect all of its exit nodes
    // to the current case node.
    if (!prev_case_node.ptrEqual(NULL)) {
      mCFG->connect(case_exit_nodes, c);
      case_exit_nodes.clear();
      prev_case_node = 0;
    }

   // if there are statements in the case body then look for break
    if (body->isValid() && body->current()) {
      // A placeholder for exit nodes.  We don't want the case body to
      // be an exit from the switch construct unless there is a break.
      // Either the body will have a break statement that collects
      // exits or the exits will all be connected the next case node
      IRStmtType prev_case_statement = build_block(c, body, case_exit_nodes,
                                                   break_switch_statements,
                                                   return_nodes, continue_nodes);

      // if there wasn't a break statement then update case_exit_nodes
      if ( break_switch_statements->size() == 0 ) {
        prev_case_node = c;
        if (prev_case_statement == SIMPLE) {
          case_exit_nodes.push_back(CFG::NodeLabel(prev_case_node, FALLTHROUGH_EDGE));
        }

      // if we did see a break then this case node will not fall through to next case node
      } else {
        prev_case_node = 0;

        // There should only be one break, but iterate anyway.
        CFG::NodeLabelListIterator
            break_stmt_iter(*break_switch_statements);
        while (break_stmt_iter.isValid()) {
          exit_nodes.push_back(break_stmt_iter.current());
          ++break_stmt_iter;
        }
        //IMPROVEME: if the body only has a break than we can simplify
        //the CFG by adding a direct_drop edge and removing this CFG
        //node, if figure out how to do this just need to set
        //empty_cond to true

      }

    // if have an empty block, still have a CFG node because break is not implied
    } else {
      prev_case_node = c;
      case_exit_nodes.push_back(CFG::NodeLabel(prev_case_node, FALLTHROUGH_EDGE));
    }

    // check if this is the catch all case
    if (mIR->isCatchAll(th,bridx)) {
      default_cond = true;
      mCFG->connect(prev_node, c, MULTIWAY_EDGE);
    } else {
      ExprHandle multiCond = mIR->getSMultiCondition(th, bridx);
      mCFG->connect(prev_node, c, MULTIWAY_EDGE, multiCond);
    }

  } /* for */

  // if last condition didn't have a break then it won't be on
  // the exit_nodes stack and should be added
  if (!prev_case_node.ptrEqual(NULL)) {
    exit_nodes.push_back(CFG::NodeLabel(prev_case_node, FALLTHROUGH_EDGE));
  }

  // direct drop is true iff there is not catchall or at least one multi-branch body is null
  if ( !default_cond || empty_cond ) {
    exit_nodes.push_back(CFG::NodeLabel(prev_node, FALLTHROUGH_EDGE));
  }

  return STRUCT_MULTIWAY_CONDITIONAL;
           
}


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_end_tested_loop (OA_ptr<Node> prev_node,
                StmtHandle th, std::list<CFG::NodeLabel>& exit_nodes,
                        OA_ptr<std::list<CFG::NodeLabel> > return_nodes)
{
  // FIXME: New construct, partially tested.
  // New CFG nodes must be allocated for both the body and loop condition (we can re-use
  // prev_node for the body if it is empty).
  OA_ptr<Node> b; b = NULL;
  OA_ptr<Node> c; c = NULL;

 // Process the loop body.
  std::list<CFG::NodeLabel> x_nodes;
  OA_ptr<IRRegionStmtIterator> body = mIR->loopBody(th);
  if (body->isValid() && body->current()) {
    if (prev_node->empty()) {
      b = prev_node;
    } else {
      b = new Node();
      mCFG->addNode(b);
      mCFG->connect(prev_node, b, FALLTHROUGH_EDGE);
    }
    OA_ptr<std::list<CFG::NodeLabel> > break_statements, continue_statements;
    break_statements = new std::list<CFG::NodeLabel>;
    continue_statements = new std::list<CFG::NodeLabel>;
    if (build_block(b, body, x_nodes, break_statements, return_nodes, continue_statements) == SIMPLE) {
      x_nodes.push_back(CFG::NodeLabel(b, FALLTHROUGH_EDGE));
    }

    CFG::NodeLabelListIterator break_iter(*break_statements);
    while (break_iter.isValid()) {
      exit_nodes.push_back(break_iter.current());
      ++break_iter;
    }

    CFG::NodeLabelListIterator continue_iter(*continue_statements);
    while (continue_iter.isValid()) {
      x_nodes.push_back(continue_iter.current());
      ++continue_iter;
    }
  }
  else { // empty body
    // FIXME: c is NULL at this point...
    x_nodes.push_back(CFG::NodeLabel(c, TRUE_EDGE));
  }

  // Allocate a node for the condition and make the proper connections.
  c = new Node(th);
  mCFG->addNode(c);
  exit_nodes.push_back(CFG::NodeLabel(c, FALSE_EDGE));
  mCFG->connect(c, b, TRUE_EDGE);
  mCFG->connect(x_nodes, c);

  return END_TESTED_LOOP;

}

IRStmtType
ManagerCFGStandard::build_CFG_unconditional_jump (
        OA_ptr<Node> prev_node,
        StmtHandle stmt)
{
  // FIXME: New construct, partially tested.
  StmtLabel lab = mIR->getTargetLabel(stmt, 0);
  prev_node->add(stmt);
  mCFG->connect(prev_node, mCFG->node_from_label(lab), FALLTHROUGH_EDGE);
  return UNCONDITIONAL_JUMP;
}


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_ustruct_twoway_branch (OA_ptr<Node>
        prev_node, StmtHandle stmt,  std::list<CFG::NodeLabel>& exit_nodes)
{
  // FIXME: New construct, partially untested.
  StmtLabel lab = mIR->getTargetLabel(stmt, 0);
  bool branch_on_true = (mIR->getCFGStmtType(stmt) == USTRUCT_TWOWAY_CONDITIONAL_T);
  prev_node->add(stmt);
  mCFG->connect(prev_node, mCFG->node_from_label(lab), (branch_on_true ? TRUE_EDGE : FALSE_EDGE));

  // This is so that the branch block will get connected to the fall-through block.
  exit_nodes.push_back(CFG::NodeLabel(prev_node, FALLTHROUGH_EDGE));  

  return mIR->getCFGStmtType(stmt);
}
//--------------------------------------------------------------------


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_unconditional_jump_i (
        OA_ptr<Node> prev_node,
        StmtHandle stmt)
{
  // Every label must be seen before all the edges can be added.
  // Just add this to the list of indirect jumps, which will have their
  // edges added later.
  cout << "FIXME: UNCONDITIONAL_JUMP_I not yet implemented" << endl;
  assert(0);
  return UNCONDITIONAL_JUMP_I;
}
//--------------------------------------------------------------------


//--------------------------------------------------------------------
IRStmtType
ManagerCFGStandard::build_CFG_ustruct_multiway_branch (OA_ptr<Node>
        prev_node, StmtHandle stmt)
{
  // FIXME: New construct, partially tested.
  // Add the multi-way statement to the previous block. It represents
  // the multi-way branch terminating the block (which holds the selector
  // expression).
  prev_node->add(stmt);

  // Connect the branch to each of its targets.
  for (int br = 0; br < mIR->numUMultiTargets(stmt); br++) {
    StmtLabel target_lab = mIR->getUMultiTargetLabel(stmt, br);
    ExprHandle cond_expr = mIR->getUMultiCondition(stmt, br);
    mCFG->connect(prev_node, mCFG->node_from_label(target_lab),
                  MULTIWAY_EDGE, cond_expr );
  }

  // If there is a default target, make the proper connections.
  StmtLabel default_lab = mIR->getUMultiCatchallLabel(stmt);
  if (default_lab) {
    mCFG->connect(prev_node, mCFG->node_from_label(default_lab),
                  MULTIWAY_EDGE /* , multiCond */);
  }

  return USTRUCT_MULTIWAY_CONDITIONAL;
}


//*****************************************************************************


//*****************************************************************************
//*****************************************************************************

//*****************************************************************************
// Refine the CFG to split blocks as necessary to handle delay slots, along
// with branches and labels in delay slots
//*****************************************************************************
void
ManagerCFGStandard::HandleDelayedBranches ()
{
  //
  // Preconditions:
  //
  // On input to this routine, all nodes and edges resulting from
  // structured control flow are already present.  In addition, all
  // nodes and edges induced by labels are present. To be finalized
  // here are the unstructured control flow contructs.
  //

  //
  // Create the "basic" CFG.  This adds control flow for the first
  // branch in a block (after its 'k' delay slots).
  //
  createBasicCFG();

#if 0 // FIXME: Disabled until its fixed.
  //
  // Finally, perform Waterman's worklist algorithm to finalize
  // control flow for the cases where branches are contained in
  // the delay slots of other branches.
  //

  // Place the start block of the procedure on the worklist
  Counterlist* emptyCounterList = new Counterlist;
  the_worklist->copyCountersToWorklist(Entry(), emptyCounterList);

  while (! the_worklist->isEmpty()) {
    for (i:NodesIterator nodes_iter(*this);
         (bool)nodes_iter && !the_worklist->isEmpty(); ++nodes_iter) {
      CFG::Node *node = dynamic_cast<CFG::Node*>((DGraph::Node*)nodes_iter);
      processBlock(node);
    }
  }
#endif
}


void
ManagerCFGStandard::createBasicCFG()
{
  // Create and populate the block_list.
  // PLM I have to modify this
  std::set<OA_ptr<Node> > block_list;
 
  OA_ptr<DGraph::NodesIteratorInterface> nodes_iter = mCFG->getNodesIterator();
  for( ; nodes_iter->isValid(); ++(*nodes_iter))
  {
    OA_ptr<DGraph::NodeInterface> dnode = nodes_iter->current();  
    OA_ptr<Node> node = dnode.convert<Node>();   

    block_list.insert(node);
  }
  
/*  for (NodesIterator nodes_iter(*mCFG); nodes_iter.isValid();
       ++nodes_iter)
  {
    OA_ptr<Node> node = nodes_iter.current();
    block_list.insert(node);
  }
*/

 // Process the blocks.
  while (block_list.size() > 0) {
    bool branch_found = false;
    int countdown = 0;
    StmtHandle stmt = 0;
    OA_ptr<Node> node = *block_list.begin();
    int numRemoved = block_list.erase(node);
    assert(numRemoved > 0);

    // Find first unstructured branch statement in this block.
   NodeStatementsIterator si(*node);
    for ( ; si.isValid(); ++si) {
      stmt = si.current();
      IRStmtType ty = mIR->getCFGStmtType(stmt);
      assert(ty != UNCONDITIONAL_JUMP_I);  // FIXME: Add support.
      if (ty == USTRUCT_TWOWAY_CONDITIONAL_T
          || ty == USTRUCT_TWOWAY_CONDITIONAL_F
          || ty == UNCONDITIONAL_JUMP) {
        branch_found = true;
        countdown = mIR->numberOfDelaySlots(stmt);
        break;
      } // if ty == branch
    } // For statements.



  // Only do this if countdown > 0, non-delayed branches are already
    // done in the main build routine.
    if (branch_found == true && countdown > 0) {
      // Move to end of this branch's delay slots.
      for ( ; si.isValid() && countdown > 0; ++si) {
        // FIXME: Need to check ParallelWithSuccessor, etc.
        --countdown;
      }


 if (countdown == 0) {
        //
        // Split the block just past its final delay slot.
        // Add the new block (the second piece of the original block) to
        // the block_list.
        // Add edges from the current block to the target(s) of the branch.
        //
        // FIXME: But before trying to do the split, check if the split point is
        // already at the end of the block.  This could happen if there
        // is a label just after the branch's final delay slot.
        //
        ++si;
        if (1 /* (bool)si == true */) {
          StmtHandle val = (si.isValid()) ? si.current() : (StmtHandle)0;
          OA_ptr<Node> newnode = mCFG->splitBlock (node, val);
          mFallThrough[node] = newnode;
          block_list.insert(newnode);
          IRStmtType ty = mIR->getCFGStmtType(stmt);
          if (ty == USTRUCT_TWOWAY_CONDITIONAL_T
              || ty == USTRUCT_TWOWAY_CONDITIONAL_F) {
            mCFG->connect(node, mCFG->getLabelBlock(mIR->getTargetLabel(stmt, 0)),
                    ty == USTRUCT_TWOWAY_CONDITIONAL_T ? TRUE_EDGE : FALSE_EDGE);
            mCFG->connect(node, newnode, FALLTHROUGH_EDGE);
          } else if (ty == UNCONDITIONAL_JUMP) {
            StmtLabel label = mIR->getTargetLabel(stmt, 0);
            OA_ptr<Node> nodeTmp = mCFG->getLabelBlock(label);
            mCFG->connect(node, nodeTmp, FALLTHROUGH_EDGE);
          } else {
            assert(0);
          }
        } // if (si)
      } // if (countdown == 0)


    } // if branch_found.

 if (branch_found == false || countdown > 0) {
      // ??? Add fall-thru edge from b (fixme, should already be there?).
      // Note, countdown > 0 can only happen if there was a label
      // in a delay slot.
    }

    
   } // While block_list.
}
  
  
  } // end of namespace CFG
} //end of namespace OA