mirror of https://github.com/YosysHQ/abc.git
227 lines
7.1 KiB
C
227 lines
7.1 KiB
C
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/**CFile****************************************************************
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FileName [seqRetIter.c]
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SystemName [ABC: Logic synthesis and verification system.]
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PackageName [Construction and manipulation of sequential AIGs.]
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Synopsis []
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Author [Alan Mishchenko]
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Affiliation [UC Berkeley]
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Date [Ver. 1.0. Started - June 20, 2005.]
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Revision [$Id: seqRetIter.c,v 1.00 2005/06/20 00:00:00 alanmi Exp $]
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***********************************************************************/
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#include "seqInt.h"
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////////////////////////////////////////////////////////////////////////
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/// DECLARATIONS ///
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////////////////////////////////////////////////////////////////////////
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// the internal procedures
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static int Seq_RetimeSearch_rec( Abc_Ntk_t * pNtk, int FiMin, int FiMax, int fVerbose );
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static int Seq_RetimeForPeriod( Abc_Ntk_t * pNtk, int Fi, int fVerbose );
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static int Seq_NodeUpdateLValue( Abc_Obj_t * pObj, int Fi );
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// node status after updating its arrival time
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enum { SEQ_UPDATE_FAIL, SEQ_UPDATE_NO, SEQ_UPDATE_YES };
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////////////////////////////////////////////////////////////////////////
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/// FUNCTION DEFINITIONS ///
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////////////////////////////////////////////////////////////////////////
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/**Function*************************************************************
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Synopsis [Retimes AIG for optimal delay using Pan's algorithm.]
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Description []
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SideEffects []
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SeeAlso []
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***********************************************************************/
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void Seq_NtkSeqRetimeDelayLags( Abc_Ntk_t * pNtk, int fVerbose )
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{
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Abc_Seq_t * p = pNtk->pManFunc;
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Abc_Obj_t * pNode;
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int i, FiMax, FiBest, RetValue;
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assert( Abc_NtkIsSeq( pNtk ) );
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// get the upper bound on the clock period
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// FiMax = Abc_NtkNodeNum(pNtk);
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FiMax = 0;
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Abc_AigForEachAnd( pNtk, pNode, i )
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if ( FiMax < (int)pNode->Level )
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FiMax = pNode->Level;
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FiMax += 2;
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// make sure this clock period is feasible
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assert( Seq_RetimeForPeriod( pNtk, FiMax, fVerbose ) );
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// search for the optimal clock period between 0 and nLevelMax
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FiBest = Seq_RetimeSearch_rec( pNtk, 0, FiMax, fVerbose );
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// recompute the best LValues
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RetValue = Seq_RetimeForPeriod( pNtk, FiBest, fVerbose );
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assert( RetValue );
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// write the retiming lags
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Vec_StrFill( p->vLags, p->nSize, 0 );
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Abc_AigForEachAnd( pNtk, pNode, i )
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Seq_NodeSetLag( pNode, (char)Seq_NodeComputeLag(Seq_NodeGetLValue(pNode), FiBest) );
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// print the result
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if ( fVerbose )
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printf( "The best clock period is %3d.\n", FiBest );
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/*
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printf( "LValues : " );
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Abc_AigForEachAnd( pNtk, pNode, i )
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printf( "%d=%d ", i, Seq_NodeGetLValue(pNode) );
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printf( "\n" );
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printf( "Lags : " );
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Abc_AigForEachAnd( pNtk, pNode, i )
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if ( Vec_StrEntry(p->vLags,i) != 0 )
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printf( "%d=%d(%d)(%d) ", i, Vec_StrEntry(p->vLags,i), Seq_NodeGetLValue(pNode), Seq_NodeGetLValue(pNode) - FiBest * Vec_StrEntry(p->vLags,i) );
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printf( "\n" );
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*/
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}
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/**Function*************************************************************
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Synopsis [Performs binary search for the optimal clock period.]
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Description [Assumes that FiMin is infeasible while FiMax is feasible.]
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SideEffects []
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SeeAlso []
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***********************************************************************/
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int Seq_RetimeSearch_rec( Abc_Ntk_t * pNtk, int FiMin, int FiMax, int fVerbose )
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{
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int Median;
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assert( FiMin < FiMax );
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if ( FiMin + 1 == FiMax )
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return FiMax;
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Median = FiMin + (FiMax - FiMin)/2;
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if ( Seq_RetimeForPeriod( pNtk, Median, fVerbose ) )
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return Seq_RetimeSearch_rec( pNtk, FiMin, Median, fVerbose ); // Median is feasible
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else
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return Seq_RetimeSearch_rec( pNtk, Median, FiMax, fVerbose ); // Median is infeasible
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}
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/**Function*************************************************************
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Synopsis [Returns 1 if retiming with this clock period is feasible.]
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Description []
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SideEffects []
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SeeAlso []
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***********************************************************************/
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int Seq_RetimeForPeriod( Abc_Ntk_t * pNtk, int Fi, int fVerbose )
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{
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Abc_Seq_t * p = pNtk->pManFunc;
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Abc_Obj_t * pObj;
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int i, c, RetValue, fChange, Counter;
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char * pReason = "";
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// set l-values of all nodes to be minus infinity
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Vec_IntFill( p->vLValues, p->nSize, -ABC_INFINITY );
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// set l-values for the constant and PIs
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pObj = Abc_NtkObj( pNtk, 0 );
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Seq_NodeSetLValue( pObj, 0 );
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Abc_NtkForEachPi( pNtk, pObj, i )
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Seq_NodeSetLValue( pObj, 0 );
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// update all values iteratively
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Counter = 0;
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for ( c = 0; c < 20; c++ )
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{
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fChange = 0;
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Abc_NtkForEachObj( pNtk, pObj, i )
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{
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if ( Abc_ObjIsPi(pObj) )
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continue;
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if ( Abc_ObjFaninNum(pObj) == 0 )
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continue;
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RetValue = Seq_NodeUpdateLValue( pObj, Fi );
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Counter++;
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if ( RetValue == SEQ_UPDATE_FAIL )
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break;
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if ( RetValue == SEQ_UPDATE_NO )
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continue;
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fChange = 1;
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}
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if ( RetValue == SEQ_UPDATE_FAIL )
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break;
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if ( fChange == 0 )
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break;
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}
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if ( c == 20 )
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{
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RetValue = SEQ_UPDATE_FAIL;
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pReason = "(timeout)";
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}
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// report the results
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if ( fVerbose )
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{
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if ( RetValue == SEQ_UPDATE_FAIL )
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printf( "Period = %3d. Iterations = %3d. Updates = %10d. Infeasible %s\n", Fi, c, Counter, pReason );
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else
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printf( "Period = %3d. Iterations = %3d. Updates = %10d. Feasible\n", Fi, c, Counter );
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}
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return RetValue != SEQ_UPDATE_FAIL;
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}
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/**Function*************************************************************
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Synopsis [Computes the l-value of the node.]
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Description [The node can be internal or a PO.]
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SideEffects []
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SeeAlso []
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***********************************************************************/
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int Seq_NodeUpdateLValue( Abc_Obj_t * pObj, int Fi )
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{
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int lValueNew, lValueOld, lValue0, lValue1;
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assert( !Abc_ObjIsPi(pObj) );
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assert( Abc_ObjFaninNum(pObj) > 0 );
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lValue0 = Seq_NodeGetLValue(Abc_ObjFanin0(pObj)) - Fi * Abc_ObjFaninL0(pObj);
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if ( Abc_ObjIsPo(pObj) )
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return (lValue0 > Fi)? SEQ_UPDATE_FAIL : SEQ_UPDATE_NO;
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if ( Abc_ObjFaninNum(pObj) == 2 )
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lValue1 = Seq_NodeGetLValue(Abc_ObjFanin1(pObj)) - Fi * Abc_ObjFaninL1(pObj);
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else
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lValue1 = -ABC_INFINITY;
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lValueNew = 1 + ABC_MAX( lValue0, lValue1 );
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lValueOld = Seq_NodeGetLValue(pObj);
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// if ( lValueNew == lValueOld )
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if ( lValueNew <= lValueOld )
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return SEQ_UPDATE_NO;
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Seq_NodeSetLValue( pObj, lValueNew );
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return SEQ_UPDATE_YES;
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}
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////////////////////////////////////////////////////////////////////////
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/// END OF FILE ///
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////////////////////////////////////////////////////////////////////////
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