Adding barrier buffers.

9 files changed, 445 insertions, 38 deletions

diff --git a/src/base/abc/abc.h b/src/base/abc/abc.h
index 8d72cd5e..2c371ce6 100644
--- a/src/base/abc/abc.h
+++ b/src/base/abc/abc.h
@@ -171,6 +171,7 @@ struct Abc_Ntk_t_
     int nObjCounts[ABC_OBJ_NUMBER];  // the number of objects by type
     int               nObjs;         // the number of live objs
     int               nConstrs;      // the number of constraints
+    int               nBarBufs;      // the number of barrier buffers
     // the backup network and the step number
     Abc_Ntk_t *       pNetBackup;    // the pointer to the previous backup network
     int               iStep;         // the generation number for the given network
@@ -330,6 +331,7 @@ static inline Vec_Int_t * Abc_ObjFaninVec( Abc_Obj_t * pObj )        { return &p
 static inline Vec_Int_t * Abc_ObjFanoutVec( Abc_Obj_t * pObj )       { return &pObj->vFanouts;          }
 static inline Abc_Obj_t * Abc_ObjCopy( Abc_Obj_t * pObj )            { return pObj->pCopy;              }
 static inline Abc_Ntk_t * Abc_ObjNtk( Abc_Obj_t * pObj )             { return pObj->pNtk;               }
+static inline Abc_Ntk_t * Abc_ObjModel( Abc_Obj_t * pObj )           { assert( pObj->Type == ABC_OBJ_WHITEBOX ); return (Abc_Ntk_t *)pObj->pData;   }
 static inline void *      Abc_ObjData( Abc_Obj_t * pObj )            { return pObj->pData;              }
 static inline Abc_Obj_t * Abc_ObjEquiv( Abc_Obj_t * pObj )           { return (Abc_Obj_t *)pObj->pData; }
 static inline Abc_Obj_t * Abc_ObjCopyCond( Abc_Obj_t * pObj )        { return Abc_ObjRegular(pObj)->pCopy? Abc_ObjNotCond(Abc_ObjRegular(pObj)->pCopy, Abc_ObjIsComplement(pObj)) : NULL;  }
@@ -552,6 +554,9 @@ extern ABC_DLL void               Abc_AigUpdateStop( Abc_Aig_t * pMan );
 extern ABC_DLL void               Abc_AigUpdateReset( Abc_Aig_t * pMan );
 /*=== abcAttach.c ==========================================================*/
 extern ABC_DLL int                Abc_NtkAttach( Abc_Ntk_t * pNtk );
+/*=== abcBarBuf.c ==========================================================*/
+extern ABC_DLL Abc_Ntk_t *        Abc_NtkToBarBufs( Abc_Ntk_t * pNtk );
+extern ABC_DLL Abc_Ntk_t *        Abc_NtkFromBarBufs( Abc_Ntk_t * pNtkBase, Abc_Ntk_t * pNtk );
 /*=== abcBlifMv.c ==========================================================*/
 extern ABC_DLL void               Abc_NtkStartMvVars( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkFreeMvVars( Abc_Ntk_t * pNtk );
@@ -945,12 +950,14 @@ extern ABC_DLL int                Abc_NtkGetFaninMax( Abc_Ntk_t * pNtk );
 extern ABC_DLL int                Abc_NtkGetFanoutMax( Abc_Ntk_t * pNtk );
 extern ABC_DLL int                Abc_NtkGetTotalFanins( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkCleanCopy( Abc_Ntk_t * pNtk );
+extern ABC_DLL void               Abc_NtkCleanCopy_rec( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkCleanData( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkFillTemp( Abc_Ntk_t * pNtk );
 extern ABC_DLL int                Abc_NtkCountCopy( Abc_Ntk_t * pNtk );
 extern ABC_DLL Vec_Ptr_t *        Abc_NtkSaveCopy( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkLoadCopy( Abc_Ntk_t * pNtk, Vec_Ptr_t * vCopies );
 extern ABC_DLL void               Abc_NtkCleanNext( Abc_Ntk_t * pNtk );
+extern ABC_DLL void               Abc_NtkCleanNext_rec( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkCleanMarkA( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkCleanMarkB( Abc_Ntk_t * pNtk );
 extern ABC_DLL void               Abc_NtkCleanMarkC( Abc_Ntk_t * pNtk );
diff --git a/src/base/abc/abcBarBuf.c b/src/base/abc/abcBarBuf.c
new file mode 100644
index 00000000..856b9f96
--- /dev/null
+++ b/src/base/abc/abcBarBuf.c
@@ -0,0 +1,353 @@
+/**CFile****************************************************************
+
+  FileName    [abcHie.c]
+
+  SystemName  [ABC: Logic synthesis and verification system.]
+
+  PackageName [Network and node package.]
+
+  Synopsis    [Procedures to handle hierarchy.]
+
+  Author      [Alan Mishchenko]
+  
+  Affiliation [UC Berkeley]
+
+  Date        [Ver. 1.0. Started - June 20, 2005.]
+
+  Revision    [$Id: abcHie.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
+
+***********************************************************************/
+
+#include "abc.h"
+
+ABC_NAMESPACE_IMPL_START
+
+
+////////////////////////////////////////////////////////////////////////
+///                        DECLARATIONS                              ///
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+///                     FUNCTION DEFINITIONS                         ///
+////////////////////////////////////////////////////////////////////////
+
+/**Function*************************************************************
+
+  Synopsis    [Checks the the hie design has no duplicated networks.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+int Abc_NtkCheckSingleInstance( Abc_Ntk_t * pNtk )
+{
+    Abc_Ntk_t * pTemp, * pModel;
+    Abc_Obj_t * pBox;
+    int i, k, RetValue = 1;
+    if ( pNtk->pDesign == NULL )
+        return 1;
+    Vec_PtrForEachEntry( Abc_Ntk_t *, pNtk->pDesign->vModules, pTemp, i )
+        pTemp->fHieVisited = 0;
+    Vec_PtrForEachEntry( Abc_Ntk_t *, pNtk->pDesign->vModules, pTemp, i )
+        Abc_NtkForEachBox( pTemp, pBox, k )
+        {
+            pModel = (Abc_Ntk_t *)pBox->pData;
+            if ( pModel == NULL )
+                continue;
+            if ( Abc_NtkLatchNum(pModel) > 0 )
+            {
+                printf( "Network \"%s\" contains %d flops.\n",                     
+                    Abc_NtkName(pNtk), Abc_NtkLatchNum(pModel) );
+                RetValue = 0;
+            }
+            if ( pModel->fHieVisited )
+            {
+                printf( "Network \"%s\" contains box \"%s\" whose model \"%s\" is instantiated more than once.\n", 
+                    Abc_NtkName(pNtk), Abc_ObjName(pBox), Abc_NtkName(pModel) );
+                RetValue = 0;
+            }
+            pModel->fHieVisited = 1;
+        }
+    Vec_PtrForEachEntry( Abc_Ntk_t *, pNtk->pDesign->vModules, pTemp, i )
+        pTemp->fHieVisited = 0;
+    return RetValue;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Collect PIs and POs of internal networks in the topo order.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkCollectPiPos_rec( Abc_Obj_t * pNet, Vec_Ptr_t * vPiPos )
+{
+    extern void Abc_NtkCollectPiPos_int( Abc_Ntk_t * pNtk, Vec_Ptr_t * vPiPos, int fAdd );
+    Abc_Obj_t * pObj, * pFanin; int i;
+    assert( Abc_ObjIsNet(pNet) );
+    if ( Abc_NodeIsTravIdCurrent( pNet ) )
+        return;
+    Abc_NodeSetTravIdCurrent( pNet );
+    pObj = Abc_ObjFanin0(pNet);
+    assert( Abc_ObjIsNode(pObj) || Abc_ObjIsBox(pObj) );
+    Abc_ObjForEachFanin( pObj, pFanin, i )
+        Abc_NtkCollectPiPos_rec( pFanin, vPiPos );
+    if ( Abc_ObjIsBox(pObj) )
+        Abc_NtkCollectPiPos_int( (Abc_Ntk_t *)pObj->pData, vPiPos, 1 );
+}
+void Abc_NtkCollectPiPos_int( Abc_Ntk_t * pNtk, Vec_Ptr_t * vPiPos, int fAdd )
+{
+    Abc_Obj_t * pObj; int i;
+    // mark primary inputs
+    Abc_NtkIncrementTravId( pNtk );
+    Abc_NtkForEachPi( pNtk, pObj, i )
+        Abc_NodeSetTravIdCurrent( Abc_ObjFanout0(pObj) );
+    // add primary inputs
+    if ( fAdd )
+    Abc_NtkForEachPi( pNtk, pObj, i )
+        Vec_PtrPush( vPiPos, pObj );
+    // visit primary outputs
+    Abc_NtkForEachPo( pNtk, pObj, i )
+        Abc_NtkCollectPiPos_rec( Abc_ObjFanin0(pObj), vPiPos );
+    // add primary outputs
+    if ( fAdd )
+    Abc_NtkForEachPo( pNtk, pObj, i )
+        Vec_PtrPush( vPiPos, pObj );
+}
+Vec_Ptr_t * Abc_NtkCollectPiPos( Abc_Ntk_t * pNtk )
+{
+    Vec_Ptr_t * vPiPos = Vec_PtrAlloc( 1000 );
+    Abc_NtkCollectPiPos_int( pNtk, vPiPos, 0 );
+    return vPiPos;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Derives logic network while introducing barbufs.]
+
+  Description []
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+void Abc_NtkToBarBufs_rec( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pNet )
+{
+    Abc_Ntk_t * pModel;
+    Abc_Obj_t * pObj, * pFanin, * pFanout, * pLatch;
+    int i;
+    assert( Abc_ObjIsNet(pNet) );
+    if ( pNet->pCopy )
+        return;
+    pObj = Abc_ObjFanin0(pNet);
+    assert( Abc_ObjIsNode(pObj) || Abc_ObjIsBox(pObj) );
+    Abc_ObjForEachFanin( pObj, pFanin, i )
+        Abc_NtkToBarBufs_rec( pNtkNew, pFanin );
+    // create and connect object
+    if ( Abc_ObjIsNode(pObj) )
+    {
+        pNet->pCopy = Abc_NtkDupObj( pNtkNew, pObj, 0 );
+        Abc_ObjForEachFanin( pObj, pFanin, i )
+            Abc_ObjAddFanin( pObj->pCopy, pFanin->pCopy );
+        return;
+    }
+    pModel = Abc_ObjModel(pObj);
+    Abc_NtkCleanCopy( pModel );
+    Abc_ObjForEachFanin( pObj, pFanin, i )
+    {
+        pLatch = Abc_NtkAddLatch( pNtkNew, pFanin->pCopy, ABC_INIT_ZERO );
+        Abc_ObjFanout0(Abc_NtkPi(pModel, i))->pCopy = Abc_ObjFanout0(pLatch);
+    }
+    Abc_NtkForEachPo( pModel, pObj, i )
+        Abc_NtkToBarBufs_rec( pNtkNew, Abc_ObjFanin0(pObj) );
+    Abc_ObjForEachFanout( pObj, pFanout, i )
+    {
+        pLatch = Abc_NtkAddLatch( pNtkNew, Abc_ObjFanin0(Abc_NtkPo(pModel, i))->pCopy, ABC_INIT_ZERO );
+        pFanout->pCopy = Abc_ObjFanout0(pLatch);
+    }
+}
+Abc_Ntk_t * Abc_NtkToBarBufs( Abc_Ntk_t * pNtk )
+{
+    Abc_Ntk_t * pNtkNew;
+    Abc_Obj_t * pObj;
+    int i;
+    assert( Abc_NtkIsNetlist(pNtk) );
+    if ( !Abc_NtkCheckSingleInstance(pNtk) )
+        return NULL;
+    Abc_NtkCleanCopy( pNtk );
+    // start the network
+    pNtkNew = Abc_NtkAlloc( ABC_NTK_LOGIC, pNtk->ntkFunc, 1 );
+    pNtkNew->pName = Extra_UtilStrsav(pNtk->pName);
+    pNtkNew->pSpec = Extra_UtilStrsav(pNtk->pSpec);
+    // clone CIs/CIs/boxes
+    Abc_NtkForEachPi( pNtk, pObj, i )
+        Abc_ObjFanout0(pObj)->pCopy = Abc_NtkDupObj( pNtkNew, pObj, 1 );
+    Abc_NtkForEachPo( pNtk, pObj, i )
+        Abc_NtkDupObj( pNtkNew, pObj, 1 );
+    // create logic 
+    Abc_NtkForEachPo( pNtk, pObj, i )
+    {
+        Abc_NtkToBarBufs_rec( pNtkNew, Abc_ObjFanin0(pObj) );
+        Abc_ObjAddFanin( pObj->pCopy, Abc_ObjFanin0(pObj)->pCopy );
+    }
+    pNtkNew->nBarBufs = Abc_NtkLatchNum(pNtkNew);
+    return pNtkNew;
+}
+
+/**Function*************************************************************
+
+  Synopsis    [Converts the logic with barbufs into a hierarchical network.]
+
+  Description [The base network is the original hierarchical network. The
+  second argument is the optimized network with barbufs.  This procedure
+  reconstructs the original hierarcical network which adding logic from
+  the optimized network.  It is assumed that the PIs/POs of the original
+  network one-to-one mapping with the flops of the optimized network.]
+               
+  SideEffects []
+
+  SeeAlso     []
+
+***********************************************************************/
+Abc_Obj_t * Abc_NtkFromBarBufs_rec( Abc_Ntk_t * pNtkNew, Abc_Obj_t * pObj )
+{
+    Abc_Obj_t * pFanin; int i;
+    if ( pObj->pCopy )
+        return pObj->pCopy;
+    Abc_NtkDupObj( pNtkNew, pObj, 0 );
+    Abc_ObjForEachFanin( pObj, pFanin, i )
+        Abc_ObjAddFanin( pObj->pCopy, Abc_NtkFromBarBufs_rec(pNtkNew, pFanin) );
+    return pObj->pCopy;
+}
+Abc_Ntk_t * Abc_NtkFromBarBufsInt( Abc_Ntk_t * pNtkBase, Abc_Ntk_t * pNtk, int fRoot )
+{
+    Abc_Ntk_t * pNtkNew;
+    Abc_Obj_t * pObj, * pTerm, * pLatch, * pNet;
+    int i, k;
+    // start the network
+    pNtkNew = Abc_NtkAlloc( pNtk->ntkType, pNtk->ntkFunc, 1 );
+    // clone CIs/CIs/boxes
+    if ( fRoot )
+    {
+        pNtkNew->pName = Extra_UtilStrsav(pNtk->pName);
+        pNtkNew->pSpec = Extra_UtilStrsav(pNtk->pSpec);
+        Abc_NtkCleanCopy( pNtk );
+        Abc_NtkForEachCi( pNtk, pObj, i )
+            Abc_NtkDupObj( pNtkNew, pObj, 1 );
+        Abc_NtkForEachCo( pNtk, pObj, i )
+            Abc_NtkDupObj( pNtkNew, pObj, 1 );
+    }
+    else
+    {
+        pNtkNew->pName = Extra_UtilStrsav(pNtkBase->pName);
+        pNtkNew->pSpec = Extra_UtilStrsav(pNtkBase->pSpec);
+        Abc_NtkForEachCi( pNtkBase, pObj, i )
+            Abc_NtkDupObj( pNtkNew, pObj, 1 );
+        Abc_NtkForEachCo( pNtkBase, pObj, i )
+            Abc_NtkDupObj( pNtkNew, pObj, 1 );
+    }
+    Abc_NtkForEachBox( pNtkBase, pObj, i )
+    {
+        Abc_NtkDupObj( pNtkNew, pObj, 1 );
+        Abc_ObjForEachFanout( pObj, pTerm, k )
+        {
+            pNet = Abc_ObjFanout0(pTerm);
+            assert( Abc_ObjIsNet(pNet) );
+            Abc_NtkDupObj( pNtkNew, pNet, 0 );
+            pLatch = Abc_NtkCi( Abc_ObjModel(pObj), k )->pNext;
+            assert( Abc_ObjIsLatch(pLatch) );
+            assert( Abc_ObjIsCi(Abc_ObjFanout0(pLatch)->pCopy) );
+            Abc_ObjAddFanin( Abc_ObjFanout0(pLatch)->pCopy, pObj->pCopy );
+            Abc_ObjAddFanin( pNet->pCopy, Abc_ObjFanout0(pLatch)->pCopy );
+            assert( Abc_ObjFanout0(Abc_ObjFanout0(pLatch))->pCopy == NULL );
+            Abc_ObjFanout0(Abc_ObjFanout0(pLatch))->pCopy = pNet->pCopy;
+        }
+    }
+    Abc_NtkForEachLatch( pNtk, pObj, i )
+        assert( Abc_ObjFanout0(Abc_ObjFanout0(pLatch))->pCopy != NULL );
+    // build PO cones
+    if ( fRoot )
+    {
+        Abc_NtkForEachPo( pNtk, pObj, i )
+            Abc_ObjAddFanin( pObj->pCopy, Abc_NtkFromBarBufs_rec(pNtkNew, Abc_ObjFanin0(pObj)) );
+    }
+    else
+    {
+        Abc_NtkForEachPo( pNtkBase, pObj, i )
+        {
+            pLatch = pObj->pNext;
+            assert( Abc_ObjIsLatch(pLatch) );
+            Abc_ObjAddFanin( pObj->pCopy, Abc_ObjFanin0(pLatch)->pCopy );
+            Abc_ObjAddFanin( Abc_ObjFanin0(pLatch)->pCopy, Abc_NtkFromBarBufs_rec(pNtkNew, Abc_ObjFanin0(Abc_ObjFanin0(pLatch))) );
+        }
+    }
+    // build BI cones
+    Abc_NtkForEachBox( pNtkBase, pObj, i )
+    {
+        Abc_ObjForEachFanin( pObj, pTerm, k )
+        {
+            pNet = Abc_ObjFanin0(pTerm);
+            assert( Abc_ObjIsNet(pNet) );
+            pLatch = Abc_NtkCo( Abc_ObjModel(pObj), k )->pNext;
+            assert( Abc_ObjIsLatch(pLatch) );
+            assert( Abc_ObjIsCo(Abc_ObjFanin0(pLatch)->pCopy) );
+            Abc_ObjAddFanin( pObj->pCopy, Abc_ObjFanin0(pLatch)->pCopy );
+            Abc_ObjAddFanin( Abc_ObjFanin0(pLatch)->pCopy, Abc_NtkFromBarBufs_rec(pNtkNew, Abc_ObjFanin0(Abc_ObjFanin0(pLatch))) );
+        }
+    }
+    return (pNtkBase->pCopy = pNtkNew);
+}
+Abc_Ntk_t * Abc_NtkFromBarBufs( Abc_Ntk_t * pNtkBase, Abc_Ntk_t * pNtk )
+{
+    Abc_Ntk_t * pNtkNew, * pTemp;
+    Vec_Ptr_t * vPiPos;
+    Abc_Obj_t * pObj;
+    int i, k;
+    assert( pNtkBase->pDesign != NULL );
+    assert( Abc_NtkIsNetlist(pNtk) );
+    assert( Abc_NtkIsNetlist(pNtkBase) );
+    assert( Abc_NtkLatchNum(pNtkBase) == 0 );
+    assert( Abc_NtkLatchNum(pNtk) == pNtk->nBarBufs );
+    assert( Abc_NtkCiNum(pNtk) == Abc_NtkCiNum(pNtkBase) );
+    assert( Abc_NtkCoNum(pNtk) == Abc_NtkCoNum(pNtkBase) );
+    // annotate PIs/POs of base with flops from optimized network
+    vPiPos = Abc_NtkCollectPiPos( pNtkBase );
+    assert( Vec_PtrSize(vPiPos) == Abc_NtkLatchNum(pNtk) );
+    Abc_NtkCleanCopy_rec( pNtkBase );
+    Abc_NtkCleanNext_rec( pNtkBase );
+    Vec_PtrForEachEntry( Abc_Obj_t *, vPiPos, pObj, i )
+        pObj->pNext = Abc_NtkBox( pNtk, i );
+    Vec_PtrFree( vPiPos );
+    // duplicate the networks
+    pNtkNew = Abc_NtkFromBarBufsInt( pNtkBase, pNtk, 1 );
+    pNtkNew->pDesign = Abc_LibCreate( pNtkBase->pDesign->pName );
+    Abc_LibAddModel( pNtkNew->pDesign, pNtkNew );
+    Vec_PtrPush( pNtkNew->pDesign->vTops, pNtkNew );
+    Vec_PtrForEachEntry( Abc_Ntk_t *, pNtkBase->pDesign->vModules, pTemp, i )
+        if ( pTemp != pNtkBase )
+        {
+            pTemp = Abc_NtkFromBarBufsInt( pTemp, pNtk, 0 );
+            Abc_LibAddModel( pNtkNew->pDesign, pTemp );
+        }
+    // set node models
+    Vec_PtrForEachEntry( Abc_Ntk_t *, pNtkBase->pDesign->vModules, pTemp, i )
+        Abc_NtkForEachBox( pTemp, pObj, k )
+            pObj->pCopy->pData = Abc_ObjModel(pObj)->pCopy;
+    return pNtkNew;
+}
+
+////////////////////////////////////////////////////////////////////////
+///                       END OF FILE                                ///
+////////////////////////////////////////////////////////////////////////
+
+
+ABC_NAMESPACE_IMPL_END
+
diff --git a/src/base/abc/abcUtil.c b/src/base/abc/abcUtil.c
index 6a3ae282..7b805386 100644
--- a/src/base/abc/abcUtil.c
+++ b/src/base/abc/abcUtil.c
@@ -509,6 +509,14 @@ void Abc_NtkCleanCopy( Abc_Ntk_t * pNtk )
     Abc_NtkForEachObj( pNtk, pObj, i )
         pObj->pCopy = NULL;
 }
+void Abc_NtkCleanCopy_rec( Abc_Ntk_t * pNtk )
+{
+    Abc_Obj_t * pObj; 
+    int i;
+    Abc_NtkCleanCopy( pNtk );
+    Abc_NtkForEachBox( pNtk, pObj, i )
+        Abc_NtkCleanCopy_rec( Abc_ObjModel(pObj) );
+}
 
 /**Function*************************************************************
 
@@ -630,6 +638,14 @@ void Abc_NtkCleanNext( Abc_Ntk_t * pNtk )
     Abc_NtkForEachObj( pNtk, pObj, i )
         pObj->pNext = NULL;
 }
+void Abc_NtkCleanNext_rec( Abc_Ntk_t * pNtk )
+{
+    Abc_Obj_t * pObj; 
+    int i;
+    Abc_NtkCleanNext( pNtk );
+    Abc_NtkForEachBox( pNtk, pObj, i )
+        Abc_NtkCleanNext_rec( Abc_ObjModel(pObj) );
+}
 
 /**Function*************************************************************
 
@@ -1451,7 +1467,7 @@ int Abc_NtkPrepareTwoNtks( FILE * pErr, Abc_Ntk_t * pNtk, char ** argv, int argc
         else
             fclose( pFile );
         pNtk1 = Abc_NtkDup(pNtk);
-        pNtk2 = Io_Read( pNtk->pSpec, Io_ReadFileType(pNtk->pSpec), fCheck );
+        pNtk2 = Io_Read( pNtk->pSpec, Io_ReadFileType(pNtk->pSpec), fCheck, 0 );
         if ( pNtk2 == NULL )
             return 0;
         *pfDelete1 = 1;
@@ -1465,7 +1481,7 @@ int Abc_NtkPrepareTwoNtks( FILE * pErr, Abc_Ntk_t * pNtk, char ** argv, int argc
             return 0;
         }
         pNtk1 = Abc_NtkDup(pNtk);
-        pNtk2 = Io_Read( argv[util_optind], Io_ReadFileType(argv[util_optind]), fCheck );
+        pNtk2 = Io_Read( argv[util_optind], Io_ReadFileType(argv[util_optind]), fCheck, 0 );
         if ( pNtk2 == NULL )
             return 0;
         *pfDelete1 = 1;
@@ -1473,10 +1489,10 @@ int Abc_NtkPrepareTwoNtks( FILE * pErr, Abc_Ntk_t * pNtk, char ** argv, int argc
     }
     else if ( argc == util_optind + 2 ) 
     {
-        pNtk1 = Io_Read( argv[util_optind], Io_ReadFileType(argv[util_optind]), fCheck );
+        pNtk1 = Io_Read( argv[util_optind], Io_ReadFileType(argv[util_optind]), fCheck, 0 );
         if ( pNtk1 == NULL )
             return 0;
-        pNtk2 = Io_Read( argv[util_optind+1], Io_ReadFileType(argv[util_optind+1]), fCheck );
+        pNtk2 = Io_Read( argv[util_optind+1], Io_ReadFileType(argv[util_optind+1]), fCheck, 0 );
         if ( pNtk2 == NULL )
         {
             Abc_NtkDelete( pNtk1 );
diff --git a/src/base/abc/module.make b/src/base/abc/module.make
index d5f55cae..e7c6345d 100644
--- a/src/base/abc/module.make
+++ b/src/base/abc/module.make
@@ -1,4 +1,5 @@
 SRC +=    src/base/abc/abcAig.c \
+    src/base/abc/abcBarBuf.c \
     src/base/abc/abcBlifMv.c \
     src/base/abc/abcCheck.c \
     src/base/abc/abcDfs.c \
diff --git a/src/base/abci/abc.c b/src/base/abci/abc.c
index 7b7ab854..f42b2aab 100644
--- a/src/base/abci/abc.c
+++ b/src/base/abci/abc.c
@@ -7268,7 +7268,7 @@ int Abc_CommandAppend( Abc_Frame_t * pAbc, int argc, char ** argv )
 
     // read the second network
     FileName = argv[globalUtilOptind];
-    pNtk2 = Io_Read( FileName, Io_ReadFileType(FileName), 1 );
+    pNtk2 = Io_Read( FileName, Io_ReadFileType(FileName), 1, 0 );
     if ( pNtk2 == NULL )
         return 1;
 
@@ -7360,7 +7360,7 @@ int Abc_CommandPutOnTop( Abc_Frame_t * pAbc, int argc, char ** argv )
 
     // read the second network
     FileName = argv[globalUtilOptind];
-    pNtk2 = Io_Read( FileName, Io_ReadFileType(FileName), 1 );
+    pNtk2 = Io_Read( FileName, Io_ReadFileType(FileName), 1, 0 );
     if ( pNtk2 == NULL )
         return 1;
 
@@ -9031,7 +9031,7 @@ int Abc_CommandExdcSet( Abc_Frame_t * pAbc, int argc, char ** argv )
     fclose( pFile );
 
     // set the new network
-    pNtkNew = Io_Read( FileName, Io_ReadFileType(FileName), 1 );
+    pNtkNew = Io_Read( FileName, Io_ReadFileType(FileName), 1, 0 );
     if ( pNtkNew == NULL )
     {
         Abc_Print( -1, "Reading network from file has failed.\n" );
@@ -9115,7 +9115,7 @@ int Abc_CommandCareSet( Abc_Frame_t * pAbc, int argc, char ** argv )
     fclose( pFile );
 
     // set the new network
-    pNtkNew = Io_Read( FileName, Io_ReadFileType(FileName), 1 );
+    pNtkNew = Io_Read( FileName, Io_ReadFileType(FileName), 1, 0 );
     if ( pNtkNew == NULL )
     {
         Abc_Print( -1, "Reading network from file has failed.\n" );
@@ -13321,7 +13321,7 @@ int Abc_CommandFraigDress( Abc_Frame_t * pAbc, int argc, char ** argv )
     pFileName = (argc == globalUtilOptind + 1) ? argv[globalUtilOptind] : Abc_NtkSpec(pNtk);
     // modify the current network
 //    Abc_NtkDress( pNtk, pFileName, fVerbose );
-    pNtk2 = Io_Read( pFileName, Io_ReadFileType(pFileName), 1 );
+    pNtk2 = Io_Read( pFileName, Io_ReadFileType(pFileName), 1, 0 );
     Abc_NtkDress2( pNtk, pNtk2, nConfs, fVerbose );
     Abc_NtkDelete( pNtk2 );
     return 0;
@@ -18949,7 +18949,7 @@ int Abc_CommandClockGate( Abc_Frame_t * pAbc, int argc, char ** argv )
 
     if ( argc == globalUtilOptind + 1 )
     {
-        pNtkCare = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1 );
+        pNtkCare = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1, 0 );
         if ( pNtkCare == NULL )
         {
             Abc_Print( -1, "Reading care network has failed.\n" );
@@ -19171,7 +19171,7 @@ int Abc_CommandInsWin( Abc_Frame_t * pAbc, int argc, char ** argv )
         Abc_Print( -1, "Not enough command-line arguments.\n" );
         return 1;
     }
-    pNtkCare = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1 );
+    pNtkCare = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1, 0 );
     if ( pNtkCare == NULL )
     {
         Abc_Print( -1, "Reading care network has failed.\n" );
@@ -20032,7 +20032,7 @@ int Abc_CommandDProve( Abc_Frame_t * pAbc, int argc, char ** argv )
     {
         char FileName[100];
         sprintf(FileName, "sm%02d.aig", pSecPar->nSMnumber );
-        pNtk = Io_Read( FileName, Io_ReadFileType(FileName), 1 );
+        pNtk = Io_Read( FileName, Io_ReadFileType(FileName), 1, 0 );
         if ( pNtk == NULL )
             Abc_Print( -1, "Cannot read back unsolved reduced sequential miter \"%s\",\n", FileName );
         else
@@ -20128,7 +20128,7 @@ int Abc_CommandAbSec( Abc_Frame_t * pAbc, int argc, char ** argv )
 
     if ( fMiter )
     {
-//        pNtk = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1 );
+//        pNtk = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1, 0 );
         if ( argc == globalUtilOptind + 1 )
         {
             Abc_Print( -1, "The miter cannot be given on the command line. Use \"read\".\n" );
@@ -23627,10 +23627,10 @@ int Abc_CommandReconcile( Abc_Frame_t * pAbc, int argc, char ** argv )
     if ( argc == globalUtilOptind + 2 )
     {
         // derive networks
-        pNtk1 = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1 );
+        pNtk1 = Io_Read( argv[globalUtilOptind], Io_ReadFileType(argv[globalUtilOptind]), 1, 0 );
         if ( pNtk1 == NULL )
             return 1;
-        pNtk2 = Io_Read( argv[globalUtilOptind+1], Io_ReadFileType(argv[globalUtilOptind+1]), 1 );
+        pNtk2 = Io_Read( argv[globalUtilOptind+1], Io_ReadFileType(argv[globalUtilOptind+1]), 1, 0 );
         if ( pNtk2 == NULL )
         {
             Abc_NtkDelete( pNtk1 );
diff --git a/src/base/cmd/cmd.c b/src/base/cmd/cmd.c
index 9f087585..2ec318d1 100644
--- a/src/base/cmd/cmd.c
+++ b/src/base/cmd/cmd.c
@@ -1731,7 +1731,7 @@ int CmdCommandSis( Abc_Frame_t * pAbc, int argc, char **argv )
     fclose( pFile );
 
     // set the new network
-    pNtkNew = Io_Read( "_sis_out.blif", IO_FILE_BLIF, 1 );
+    pNtkNew = Io_Read( "_sis_out.blif", IO_FILE_BLIF, 1, 0 );
     // set the original spec of the new network
     if ( pNtk->pSpec )
     {
@@ -1873,7 +1873,7 @@ int CmdCommandMvsis( Abc_Frame_t * pAbc, int argc, char **argv )
     fclose( pFile );
 
     // set the new network
-    pNtkNew = Io_Read( "_mvsis_out.blif", IO_FILE_BLIF, 1 );
+    pNtkNew = Io_Read( "_mvsis_out.blif", IO_FILE_BLIF, 1, 0 );
     // set the original spec of the new network
     if ( pNtk->pSpec )
     {
diff --git a/src/base/io/io.c b/src/base/io/io.c
index b4fc1a00..ef17c8fd 100644
--- a/src/base/io/io.c
+++ b/src/base/io/io.c
@@ -172,12 +172,13 @@ int IoCommandRead( Abc_Frame_t * pAbc, int argc, char ** argv )
     char Command[1000];
     Abc_Ntk_t * pNtk;
     char * pFileName, * pTemp;
-    int c, fCheck;
+    int c, fCheck, fBarBufs;
 
     fCheck = 1;
+    fBarBufs = 0;
     glo_fMapped = 0;
     Extra_UtilGetoptReset();
-    while ( ( c = Extra_UtilGetopt( argc, argv, "mch" ) ) != EOF )
+    while ( ( c = Extra_UtilGetopt( argc, argv, "mcbh" ) ) != EOF )
     {
         switch ( c )
         {
@@ -187,6 +188,9 @@ int IoCommandRead( Abc_Frame_t * pAbc, int argc, char ** argv )
             case 'c':
                 fCheck ^= 1;
                 break;
+            case 'b':
+                fBarBufs ^= 1;
+                break;
             case 'h':
                 goto usage;
             default:
@@ -230,7 +234,7 @@ int IoCommandRead( Abc_Frame_t * pAbc, int argc, char ** argv )
         return 0;
     }
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, Io_ReadFileType(pFileName), fCheck );
+    pNtk = Io_Read( pFileName, Io_ReadFileType(pFileName), fCheck, fBarBufs );
     if ( pNtk == NULL )
         return 0;
     if ( Abc_NtkPiNum(pNtk) == 0 )
@@ -245,12 +249,13 @@ int IoCommandRead( Abc_Frame_t * pAbc, int argc, char ** argv )
     return 0;
 
 usage:
-    fprintf( pAbc->Err, "usage: read [-mch] <file>\n" );
+    fprintf( pAbc->Err, "usage: read [-mcbh] <file>\n" );
     fprintf( pAbc->Err, "\t         replaces the current network by the network read from <file>\n" );
     fprintf( pAbc->Err, "\t         by calling the parser that matches the extension of <file>\n" );
     fprintf( pAbc->Err, "\t         (to read a hierarchical design, use \"read_hie\")\n" );
     fprintf( pAbc->Err, "\t-m     : toggle reading mapped Verilog [default = %s]\n", glo_fMapped? "yes":"no" );
     fprintf( pAbc->Err, "\t-c     : toggle network check after reading [default = %s]\n", fCheck? "yes":"no" );
+    fprintf( pAbc->Err, "\t-b     : toggle reading barrier buffers [default = %s]\n", fBarBufs? "yes":"no" );
     fprintf( pAbc->Err, "\t-h     : prints the command summary\n" );
     fprintf( pAbc->Err, "\tfile   : the name of a file to read\n" );
     return 1;
@@ -294,7 +299,7 @@ int IoCommandReadAiger( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_AIGER, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_AIGER, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -349,7 +354,7 @@ int IoCommandReadBaf( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_BAF, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_BAF, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -404,7 +409,7 @@ int IoCommandReadBblif( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_BBLIF, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_BBLIF, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -473,7 +478,7 @@ int IoCommandReadBlif( Abc_Frame_t * pAbc, int argc, char ** argv )
     if ( fReadAsAig )
         pNtk = Io_ReadBlifAsAig( pFileName, fCheck );
     else if ( fUseNewParser )
-        pNtk = Io_Read( pFileName, IO_FILE_BLIF, fCheck );
+        pNtk = Io_Read( pFileName, IO_FILE_BLIF, fCheck, 0 );
     else
     {
         Abc_Ntk_t * pTemp;
@@ -541,7 +546,7 @@ int IoCommandReadBlifMv( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_BLIFMV, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_BLIFMV, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -597,7 +602,7 @@ int IoCommandReadBench( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_BENCH, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_BENCH, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -714,7 +719,7 @@ int IoCommandReadEdif( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_EDIF, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_EDIF, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -769,7 +774,7 @@ int IoCommandReadEqn( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_EQN, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_EQN, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -910,7 +915,7 @@ int IoCommandReadPla( Abc_Frame_t * pAbc, int argc, char ** argv )
         Abc_NtkDelete( pTemp );
     }
     else
-        pNtk = Io_Read( pFileName, IO_FILE_PLA, fCheck );
+        pNtk = Io_Read( pFileName, IO_FILE_PLA, fCheck, 0 );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -1015,13 +1020,14 @@ int IoCommandReadVerilog( Abc_Frame_t * pAbc, int argc, char ** argv )
 {
     Abc_Ntk_t * pNtk;
     char * pFileName;
-    int fCheck;
+    int fCheck, fBarBufs;
     int c;
 
     fCheck = 1;
+    fBarBufs = 0;
     glo_fMapped = 0;
     Extra_UtilGetoptReset();
-    while ( ( c = Extra_UtilGetopt( argc, argv, "mch" ) ) != EOF )
+    while ( ( c = Extra_UtilGetopt( argc, argv, "mcbh" ) ) != EOF )
     {
         switch ( c )
         {
@@ -1031,6 +1037,9 @@ int IoCommandReadVerilog( Abc_Frame_t * pAbc, int argc, char ** argv )
             case 'c':
                 fCheck ^= 1;
                 break;
+            case 'b':
+                fBarBufs ^= 1;
+                break;
             case 'h':
                 goto usage;
             default:
@@ -1042,7 +1051,7 @@ int IoCommandReadVerilog( Abc_Frame_t * pAbc, int argc, char ** argv )
     // get the input file name
     pFileName = argv[globalUtilOptind];
     // read the file using the corresponding file reader
-    pNtk = Io_Read( pFileName, IO_FILE_VERILOG, fCheck );
+    pNtk = Io_Read( pFileName, IO_FILE_VERILOG, fCheck, fBarBufs );
     if ( pNtk == NULL )
         return 1;
     // replace the current network
@@ -1051,10 +1060,11 @@ int IoCommandReadVerilog( Abc_Frame_t * pAbc, int argc, char ** argv )
     return 0;
 
 usage:
-    fprintf( pAbc->Err, "usage: read_verilog [-mch] <file>\n" );
+    fprintf( pAbc->Err, "usage: read_verilog [-mcbh] <file>\n" );
     fprintf( pAbc->Err, "\t         reads the network in Verilog (IWLS 2002/2005 subset)\n" );
     fprintf( pAbc->Err, "\t-m     : toggle reading mapped Verilog [default = %s]\n", glo_fMapped? "yes":"no" );
     fprintf( pAbc->Err, "\t-c     : toggle network check after reading [default = %s]\n", fCheck? "yes":"no" );
+    fprintf( pAbc->Err, "\t-b     : toggle reading barrier buffers [default = %s]\n", fBarBufs? "yes":"no" );
     fprintf( pAbc->Err, "\t-h     : prints the command summary\n" );
     fprintf( pAbc->Err, "\tfile   : the name of a file to read\n" );
     return 1;
diff --git a/src/base/io/ioAbc.h b/src/base/io/ioAbc.h
index efac1212..f20f5c3d 100644
--- a/src/base/io/ioAbc.h
+++ b/src/base/io/ioAbc.h
@@ -136,7 +136,7 @@ extern void               Io_WriteVerilog( Abc_Ntk_t * pNtk, char * FileName );
 extern Io_FileType_t      Io_ReadFileType( char * pFileName );
 extern Io_FileType_t      Io_ReadLibType( char * pFileName );
 extern Abc_Ntk_t *        Io_ReadNetlist( char * pFileName, Io_FileType_t FileType, int fCheck );
-extern Abc_Ntk_t *        Io_Read( char * pFileName, Io_FileType_t FileType, int fCheck );
+extern Abc_Ntk_t *        Io_Read( char * pFileName, Io_FileType_t FileType, int fCheck, int fBarBufs );
 extern void               Io_Write( Abc_Ntk_t * pNtk, char * pFileName, Io_FileType_t FileType );
 extern void               Io_WriteHie( Abc_Ntk_t * pNtk, char * pBaseName, char * pFileName );
 extern Abc_Obj_t *        Io_ReadCreatePi( Abc_Ntk_t * pNtk, char * pName );
diff --git a/src/base/io/ioUtil.c b/src/base/io/ioUtil.c
index 0044f5fd..685fcf73 100644
--- a/src/base/io/ioUtil.c
+++ b/src/base/io/ioUtil.c
@@ -223,7 +223,7 @@ void updateLtlStoreOfNtk( Abc_Ntk_t *pNtk, Vec_Ptr_t *tempLtlStore )
   SeeAlso     []
 
 ***********************************************************************/
-Abc_Ntk_t * Io_Read( char * pFileName, Io_FileType_t FileType, int fCheck )
+Abc_Ntk_t * Io_Read( char * pFileName, Io_FileType_t FileType, int fCheck, int fBarBufs )
 {
     Abc_Ntk_t * pNtk, * pTemp;
     Vec_Ptr_t * vLtl;
@@ -234,6 +234,14 @@ Abc_Ntk_t * Io_Read( char * pFileName, Io_FileType_t FileType, int fCheck )
     vLtl = temporaryLtlStore( pNtk );
     if ( !Abc_NtkIsNetlist(pNtk) )
         return pNtk;
+    // derive barbufs
+    if ( fBarBufs )
+    {
+        pNtk = Abc_NtkToBarBufs( pTemp = pNtk );
+        Abc_NtkDelete( pTemp );
+        assert( Abc_NtkIsLogic(pNtk) );
+        return pNtk;
+    }
     // flatten logic hierarchy
     assert( Abc_NtkIsNetlist(pNtk) );
     if ( Abc_NtkWhiteboxNum(pNtk) > 0 )
@@ -481,13 +489,22 @@ void Io_WriteHie( Abc_Ntk_t * pNtk, char * pBaseName, char * pFileName )
     if ( Abc_NtkWhiteboxNum(pNtkBase) > 0 )
     {
         pNtkBase = Abc_NtkFlattenLogicHierarchy( pNtkTemp = pNtkBase );
+        Abc_NtkDelete( pNtkTemp );
         if ( pNtkBase == NULL )
             return;
-        Abc_NtkDelete( pNtkTemp );
     }
 
     // reintroduce the boxes into the netlist
-    if ( Io_ReadFileType(pBaseName) == IO_FILE_BLIFMV ) 
+    if ( pNtk->nBarBufs > 0 )
+    {
+        // derive the netlist
+        pNtkResult = Abc_NtkToNetlist( pNtk );
+        pNtkResult = Abc_NtkFromBarBufs( pNtkBase, pNtkTemp = pNtkResult );
+        Abc_NtkDelete( pNtkTemp );
+        if ( pNtkResult )
+            printf( "Hierarchy writer reintroduced %d barbufs.\n", pNtk->nBarBufs );
+    }
+    else if ( Io_ReadFileType(pBaseName) == IO_FILE_BLIFMV ) 
     {
         if ( Abc_NtkBlackboxNum(pNtkBase) > 0 )
         {
@@ -499,7 +516,10 @@ void Io_WriteHie( Abc_Ntk_t * pNtk, char * pBaseName, char * pFileName )
         assert( !Abc_NtkIsNetlist(pNtk) );
         pNtkResult = Abc_NtkToNetlist( pNtk );
         if ( !Abc_NtkConvertToBlifMv( pNtkResult ) )
+        {
+            Abc_NtkDelete( pNtkBase );
             return;
+        }
         // reintroduce the network
         pNtkResult = Abc_NtkInsertBlifMv( pNtkBase, pNtkTemp = pNtkResult );
         Abc_NtkDelete( pNtkTemp );