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/**CFile****************************************************************
FileName [abcSeqRetime.c]
SystemName [ABC: Logic synthesis and verification system.]
PackageName [Network and node package.]
Synopsis [Peforms retiming for optimal clock cycle.]
Author [Alan Mishchenko]
Affiliation [UC Berkeley]
Date [Ver. 1.0. Started - June 20, 2005.]
Revision [$Id: abcSeqRetime.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
***********************************************************************/
#include "abcs.h"
////////////////////////////////////////////////////////////////////////
/// DECLARATIONS ///
////////////////////////////////////////////////////////////////////////
// storing arrival times in the nodes
static inline int Abc_NodeReadLValue( Abc_Obj_t * pNode ) { return Vec_IntEntry( (pNode)->pNtk->pData, (pNode)->Id ); }
static inline void Abc_NodeSetLValue( Abc_Obj_t * pNode, int Value ) { Vec_IntWriteEntry( (pNode)->pNtk->pData, (pNode)->Id, (Value) ); }
//static inline int Abc_NodeGetLag( int LValue, int Fi ) { return LValue/Fi - (int)(LValue % Fi == 0); }
static inline int Abc_NodeGetLag( int LValue, int Fi ) { return (LValue + 256*Fi)/Fi - 256 - (int)(LValue % Fi == 0); }
// the internal procedures
static int Abc_NtkRetimeSearch_rec( Abc_Ntk_t * pNtk, int FiMin, int FiMax, int fVerbose );
static int Abc_NtkRetimeForPeriod( Abc_Ntk_t * pNtk, int Fi, int fVerbose );
static int Abc_NodeUpdateLValue( Abc_Obj_t * pObj, int Fi );
// node status after updating its arrival time
enum { ABC_UPDATE_FAIL, ABC_UPDATE_NO, ABC_UPDATE_YES };
static void Abc_RetimingExperiment( Abc_Ntk_t * pNtk, Vec_Str_t * vLags );
////////////////////////////////////////////////////////////////////////
/// FUNCTION DEFITIONS ///
////////////////////////////////////////////////////////////////////////
/**Function*************************************************************
Synopsis [Retimes AIG for optimal delay.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
Vec_Str_t * Abc_NtkSeqRetimeDelayLags( Abc_Ntk_t * pNtk, int fVerbose )
{
Vec_Str_t * vLags;
Abc_Obj_t * pNode;
int i, FiMax, FiBest, RetValue;
assert( Abc_NtkIsSeq( pNtk ) );
// start storage for sequential arrival times
assert( pNtk->pData == NULL );
pNtk->pData = Vec_IntAlloc( 0 );
// get the upper bound on the clock period
// FiMax = Abc_NtkNodeNum(pNtk);
FiMax = 0;
Abc_AigForEachAnd( pNtk, pNode, i )
if ( FiMax < (int)pNode->Level )
FiMax = pNode->Level;
FiMax += 2;
// make sure this clock period is feasible
assert( Abc_NtkRetimeForPeriod( pNtk, FiMax, fVerbose ) );
// search for the optimal clock period between 0 and nLevelMax
FiBest = Abc_NtkRetimeSearch_rec( pNtk, 0, FiMax, fVerbose );
// recompute the best LValues
RetValue = Abc_NtkRetimeForPeriod( pNtk, FiBest, fVerbose );
assert( RetValue );
// print the result
if ( fVerbose )
printf( "The best clock period is %3d.\n", FiBest );
// convert to lags
vLags = Vec_StrStart( Abc_NtkObjNumMax(pNtk) );
Abc_AigForEachAnd( pNtk, pNode, i )
Vec_StrWriteEntry( vLags, i, (char)Abc_NodeGetLag(Abc_NodeReadLValue(pNode), FiBest) );
/*
printf( "LValues : " );
Abc_AigForEachAnd( pNtk, pNode, i )
printf( "%d=%d ", i, Abc_NodeReadLValue(pNode) );
printf( "\n" );
printf( "Lags : " );
Abc_AigForEachAnd( pNtk, pNode, i )
if ( Vec_StrEntry(vLags,i) != 0 )
printf( "%d=%d(%d)(%d) ", i, Vec_StrEntry(vLags,i), Abc_NodeReadLValue(pNode), Abc_NodeReadLValue(pNode) - FiBest * Vec_StrEntry(vLags,i) );
printf( "\n" );
*/
// free storage
Vec_IntFree( pNtk->pData );
pNtk->pData = NULL;
return vLags;
}
/**Function*************************************************************
Synopsis [Performs binary search for the optimal clock period.]
Description [Assumes that FiMin is infeasible while FiMax is feasible.]
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeSearch_rec( Abc_Ntk_t * pNtk, int FiMin, int FiMax, int fVerbose )
{
int Median;
assert( FiMin < FiMax );
if ( FiMin + 1 == FiMax )
return FiMax;
Median = FiMin + (FiMax - FiMin)/2;
if ( Abc_NtkRetimeForPeriod( pNtk, Median, fVerbose ) )
return Abc_NtkRetimeSearch_rec( pNtk, FiMin, Median, fVerbose ); // Median is feasible
else
return Abc_NtkRetimeSearch_rec( pNtk, Median, FiMax, fVerbose ); // Median is infeasible
}
/**Function*************************************************************
Synopsis [Returns 1 if retiming with this clock period is feasible.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeForPeriod2( Abc_Ntk_t * pNtk, int Fi )
{
Vec_Ptr_t * vFrontier;
Abc_Obj_t * pObj, * pFanout;
char * pReason = "";
int RetValue, i, k;
int Limit;
// set l-values of all nodes to be minus infinity
Vec_IntFill( pNtk->pData, Abc_NtkObjNumMax(pNtk), -ABC_INFINITY );
// start the frontier by setting PI l-values to 0 and including PI fanouts
vFrontier = Vec_PtrAlloc( 100 );
pObj = Abc_NtkObj( pNtk, 0 );
if ( Abc_ObjFanoutNum(pObj) > 0 )
{
Abc_NodeSetLValue( pObj, 0 );
Abc_ObjForEachFanout( pObj, pFanout, k )
if ( pFanout->fMarkA == 0 )
{
Vec_PtrPush( vFrontier, pFanout );
pFanout->fMarkA = 1;
}
}
Abc_NtkForEachPi( pNtk, pObj, i )
{
Abc_NodeSetLValue( pObj, 0 );
Abc_ObjForEachFanout( pObj, pFanout, k )
if ( pFanout->fMarkA == 0 )
{
Vec_PtrPush( vFrontier, pFanout );
pFanout->fMarkA = 1;
}
}
// iterate until convergence
Limit = Abc_NtkObjNumMax(pNtk) * 20;
Vec_PtrForEachEntry( vFrontier, pObj, i )
{
pObj->fMarkA = 0;
RetValue = Abc_NodeUpdateLValue( pObj, Fi );
if ( RetValue == ABC_UPDATE_FAIL )
break;
if ( i == Limit )
{
RetValue = ABC_UPDATE_FAIL;
pReason = "(timeout)";
break;
}
if ( RetValue == ABC_UPDATE_NO )
continue;
assert( RetValue == ABC_UPDATE_YES );
// arrival times have changed - add fanouts to the frontier
Abc_ObjForEachFanout( pObj, pFanout, k )
if ( pFanout->fMarkA == 0 && pFanout != pObj )
{
Vec_PtrPush( vFrontier, pFanout );
pFanout->fMarkA = 1;
}
}
// clean the nodes
Vec_PtrForEachEntryStart( vFrontier, pObj, k, i )
pObj->fMarkA = 0;
// report the results
if ( RetValue == ABC_UPDATE_FAIL )
printf( "Period = %3d. Updated nodes = %6d. Infeasible %s\n", Fi, vFrontier->nSize, pReason );
else
printf( "Period = %3d. Updated nodes = %6d. Feasible\n", Fi, vFrontier->nSize );
Vec_PtrFree( vFrontier );
return RetValue != ABC_UPDATE_FAIL;
}
/**Function*************************************************************
Synopsis [Returns 1 if retiming with this clock period is feasible.]
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetimeForPeriod( Abc_Ntk_t * pNtk, int Fi, int fVerbose )
{
Abc_Obj_t * pObj;
int i, c, RetValue, fChange, Counter;
char * pReason = "";
// set l-values of all nodes to be minus infinity
Vec_IntFill( pNtk->pData, Abc_NtkObjNumMax(pNtk), -ABC_INFINITY );
// set l-values for the constant and PIs
pObj = Abc_NtkObj( pNtk, 0 );
Abc_NodeSetLValue( pObj, 0 );
Abc_NtkForEachPi( pNtk, pObj, i )
Abc_NodeSetLValue( pObj, 0 );
// update all values iteratively
Counter = 0;
for ( c = 0; c < 20; c++ )
{
fChange = 0;
Abc_NtkForEachObj( pNtk, pObj, i )
{
if ( Abc_ObjIsPi(pObj) )
continue;
if ( Abc_ObjFaninNum(pObj) == 0 )
continue;
RetValue = Abc_NodeUpdateLValue( pObj, Fi );
Counter++;
if ( RetValue == ABC_UPDATE_FAIL )
break;
if ( RetValue == ABC_UPDATE_NO )
continue;
fChange = 1;
}
if ( RetValue == ABC_UPDATE_FAIL )
break;
if ( fChange == 0 )
break;
}
if ( c == 20 )
{
RetValue = ABC_UPDATE_FAIL;
pReason = "(timeout)";
}
// report the results
if ( fVerbose )
{
if ( RetValue == ABC_UPDATE_FAIL )
printf( "Period = %3d. Iterations = %3d. Updates = %6d. Infeasible %s\n", Fi, c, Counter, pReason );
else
printf( "Period = %3d. Iterations = %3d. Updates = %6d. Feasible\n", Fi, c, Counter );
}
return RetValue != ABC_UPDATE_FAIL;
}
/**Function*************************************************************
Synopsis [Computes the l-value of the node.]
Description [The node can be internal or a PO.]
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NodeUpdateLValue( Abc_Obj_t * pObj, int Fi )
{
int lValueNew, lValueOld, lValue0, lValue1;
assert( !Abc_ObjIsPi(pObj) );
assert( Abc_ObjFaninNum(pObj) > 0 );
lValue0 = Abc_NodeReadLValue(Abc_ObjFanin0(pObj)) - Fi * Abc_ObjFaninL0(pObj);
if ( Abc_ObjIsPo(pObj) )
return (lValue0 > Fi)? ABC_UPDATE_FAIL : ABC_UPDATE_NO;
if ( Abc_ObjFaninNum(pObj) == 2 )
lValue1 = Abc_NodeReadLValue(Abc_ObjFanin1(pObj)) - Fi * Abc_ObjFaninL1(pObj);
else
lValue1 = -ABC_INFINITY;
lValueNew = 1 + ABC_MAX( lValue0, lValue1 );
lValueOld = Abc_NodeReadLValue(pObj);
// if ( lValueNew == lValueOld )
if ( lValueNew <= lValueOld )
return ABC_UPDATE_NO;
Abc_NodeSetLValue( pObj, lValueNew );
return ABC_UPDATE_YES;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_RetimingPrint_rec( Abc_Obj_t * pObj )
{
Abc_Obj_t * pFanin0, * pFanin1;
int Depth0, Depth1;
if ( Abc_ObjIsPi(pObj) )
{
printf( "%d -> ", pObj->Id );
return 0;
}
pFanin0 = Abc_ObjFanin0(pObj);
pFanin1 = Abc_ObjFanin1(pObj);
if ( Abc_ObjFaninL0(pObj) == 0 && Abc_ObjFaninL1(pObj) > 0 )
Abc_RetimingPrint_rec( pFanin0 );
else if ( Abc_ObjFaninL1(pObj) == 0 && Abc_ObjFaninL0(pObj) > 0 )
Abc_RetimingPrint_rec( pFanin1 );
else if ( Abc_ObjFaninL0(pObj) == 0 && Abc_ObjFaninL1(pObj) == 0 )
{
Depth0 = (int)pFanin0->pCopy;
Depth1 = (int)pFanin1->pCopy;
if ( Depth0 > Depth1 )
Abc_RetimingPrint_rec( pFanin0 );
else
Abc_RetimingPrint_rec( pFanin1 );
}
printf( "%d (%d) -> ", pObj->Id, (int)pObj->pCopy );
return 0;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_Retiming_rec( Abc_Obj_t * pObj )
{
int Depth0, Depth1, Depth;
if ( Abc_ObjIsPi(pObj) )
{
pObj->pCopy = 0;
return 0;
}
// if this node is already visited, skip
if ( Abc_NodeIsTravIdCurrent( pObj ) )
return (int)pObj->pCopy;
// mark the node as visited
Abc_NodeSetTravIdCurrent( pObj );
if ( Abc_ObjFaninL0(pObj) == 0 )
Depth0 = Abc_Retiming_rec( Abc_ObjFanin0(pObj) );
else
Depth0 = 0;
if ( Abc_ObjFaninL1(pObj) == 0 )
Depth1 = Abc_Retiming_rec( Abc_ObjFanin1(pObj) );
else
Depth1 = 0;
Depth = 1 + ABC_MAX( Depth0, Depth1 );
pObj->pCopy = (void *)Depth;
return Depth;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
int Abc_NtkRetiming( Abc_Ntk_t * pNtk )
{
Abc_Obj_t * pObj;
int i, Depth;
Abc_NtkForEachObj( pNtk, pObj, i )
{
if ( Abc_ObjFaninNum(pObj) != 2 )
continue;
if ( Abc_ObjFaninL0(pObj) > 0 )
{
Abc_NtkIncrementTravId(pNtk);
Depth = Abc_Retiming_rec( Abc_ObjFanin0(pObj) );
if ( Depth > 30 )
{
printf( "Depth is %d. ", Depth );
Abc_RetimingPrint_rec( Abc_ObjFanin0(pObj) );
printf( "\n\n" );
}
}
if ( Abc_ObjFaninL1(pObj) > 0 )
{
Abc_NtkIncrementTravId(pNtk);
Depth = Abc_Retiming_rec( Abc_ObjFanin1(pObj) );
if ( Depth > 30 )
{
printf( "Depth is %d. ", Depth );
Abc_RetimingPrint_rec( Abc_ObjFanin1(pObj) );
printf( "\n\n" );
}
}
}
return 0;
}
/**Function*************************************************************
Synopsis []
Description []
SideEffects []
SeeAlso []
***********************************************************************/
void Abc_RetimingExperiment( Abc_Ntk_t * pNtk, Vec_Str_t * vLags )
{
Abc_Obj_t * pObj;
char Lag;
int i;
Vec_StrForEachEntry( vLags, Lag, i )
{
if ( Lag == 0 )
continue;
pObj = Abc_NtkObj( pNtk, i );
if ( Lag < 0 )
Abc_ObjRetimeForwardTry( pObj, -Lag );
else
Abc_ObjRetimeBackwardTry( pObj, Lag );
}
// make sure there are no negative latches
Abc_NtkForEachObj( pNtk, pObj, i )
{
if ( Abc_ObjFaninNum(pObj) == 0 )
continue;
assert( Abc_ObjFaninL0(pObj) >= 0 );
if ( Abc_ObjFaninNum(pObj) == 1 )
continue;
assert( Abc_ObjFaninL1(pObj) >= 0 );
// printf( "%d=(%d,%d) ", i, Abc_ObjFaninL0(pObj), Abc_ObjFaninL1(pObj) );
}
// printf( "\n" );
Abc_NtkRetiming( pNtk );
Vec_StrForEachEntry( vLags, Lag, i )
{
if ( Lag == 0 )
continue;
pObj = Abc_NtkObj( pNtk, i );
if ( Lag < 0 )
Abc_ObjRetimeBackwardTry( pObj, -Lag );
else
Abc_ObjRetimeForwardTry( pObj, Lag );
}
// Abc_NtkSeqRetimeDelayLags( pNtk );
}
////////////////////////////////////////////////////////////////////////
/// END OF FILE ///
////////////////////////////////////////////////////////////////////////
|
