#include "AST.h"
#include "compiler.h"
#include "optimize-monitors.h"


struct MonitorStats
{
  unsigned unchanged;
  unsigned simplified;
  unsigned eliminated;

  // If PR #327 ever gets fixed, remove the "eliminated" field
  
  MonitorStats()
    : unchanged( 0 ),
      simplified( 0 ),
      eliminated( 0 )
  {
  }
};


bool opt_monitors = false; // DOB: off by default because it's unsafe
bool stat_monitors = false;


////////////////////////////////////////////////////////////////////////
//
//  some monitors can never be contested
//


bool MonitorFetchClassNode::superfluous() const
{
  // If PR #327 ever gets fixed, change this to "false".
  return true;
}


bool MonitorFetchInstanceNode::superfluous() const
{
  const TypeNode &exprType = *expr()->type();
  return exprType.isLocal() && exprType.sharing() == Nonshared;
}


bool MonitorUseNode::superfluous() const
{
  return fetcher()->superfluous();
}


////////////////////////////////////////////////////////////////////////
//
//  eliminate superfluous monitor operations
//


TreeNode *MonitorFetchClassNode::optimizeMonitors( MonitorStats &stats )
{
  // If PR #327 ever gets fixed, remove this method entirely.
  
  if (superfluous())
    {
      ++stats.eliminated;
      return new EmptyStmtNode();
    }
  else
    {
      ++stats.unchanged;
      return TreeNode::optimizeMonitors( stats );
    }
}


TreeNode *MonitorFetchInstanceNode::optimizeMonitors( MonitorStats &stats )
{
  if (superfluous())
    {
      ++stats.simplified;
      return new CheckNullNode(expr());
    }
  else
    {
      ++stats.unchanged;
      return TreeNode::optimizeMonitors( stats );
    }
}


TreeNode *MonitorUseNode::optimizeMonitors( MonitorStats &stats )
{
  return superfluous()
    ? new EmptyStmtNode()
    : TreeNode::optimizeMonitors( stats );
}


////////////////////////////////////////////////////////////////////////
//
//  generic traversal
//


TreeNode *ClassDeclNode::optimizeMonitors( MonitorStats &stats )
{
  return selectedForCodeGen( false )
    ? TreeNode::optimizeMonitors( stats )
    : this;
}


TreeNode *CompileUnitNode::optimizeMonitors( MonitorStats &stats )
{
  return selectedForCodeGen( false )
    ? TreeNode::optimizeMonitors( stats )
    : this;
}


TreeNode *TemplateDeclNode::optimizeMonitors( MonitorStats &stats )
{
  return this;
}


TreeNode *TreeNode::optimizeMonitors( MonitorStats &stats )
{
  const int count = arity();
  
  for (int sweep = 0; sweep < count; ++sweep)
    child( sweep, child(sweep)->optimizeMonitors( stats ) );

  return this;
}


////////////////////////////////////////////////////////////////////////
//
//  published interface
//

void optimizeMonitors()
{
  if (opt_monitors)
    {
      MonitorStats stats;
  
      foreach (file, llist< CompileUnitNode * >, *allFiles)
	(*file)->optimizeMonitors( stats );

      if (stat_monitors)
	cerr << "monitor optimization statistics: "
	     << stats.eliminated << " eliminated, "
	     << stats.simplified << " simplified, "
	     << stats.unchanged << " unchanged"
	     << endl;
    }
}