mirror of https://github.com/YosysHQ/abc.git
Fixing combinational loop problem in choice computation
This commit is contained in:
Alan Mishchenko
parent
cdcbd60b39
commit
a2e2661e1f
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@ -272,6 +272,165 @@ Aig_Man_t * Dch_DeriveChoiceAig_old( Aig_Man_t * pAig )
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}
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/**Function*************************************************************
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Synopsis [Checks for combinational loops in the AIG.]
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Description [Returns 1 if combinational loop is detected.]
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SideEffects []
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SeeAlso []
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***********************************************************************/
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int Aig_ManCheckAcyclic_rec( Aig_Man_t * p, Aig_Obj_t * pNode, int fVerbose )
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{
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Aig_Obj_t * pFanin;
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int fAcyclic;
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if ( Aig_ObjIsPi(pNode) || Aig_ObjIsConst1(pNode) )
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return 1;
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assert( Aig_ObjIsNode(pNode) );
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// make sure the node is not visited
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assert( !Aig_ObjIsTravIdPrevious(p, pNode) );
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// check if the node is part of the combinational loop
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if ( Aig_ObjIsTravIdCurrent(p, pNode) )
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{
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if ( fVerbose )
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Abc_Print( 1, "Network \"%s\" contains combinational loop!\n", p->pSpec? p->pSpec : NULL );
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if ( fVerbose )
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Abc_Print( 1, "Node \"%d\" is encountered twice on the following path to the COs:\n", Aig_ObjId(pNode) );
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return 0;
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}
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// mark this node as a node on the current path
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Aig_ObjSetTravIdCurrent( p, pNode );
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// visit the transitive fanin
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pFanin = Aig_ObjFanin0(pNode);
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// check if the fanin is visited
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if ( !Aig_ObjIsTravIdPrevious(p, pFanin) )
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{
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// traverse the fanin's cone searching for the loop
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if ( !(fAcyclic = Aig_ManCheckAcyclic_rec(p, pFanin, fVerbose)) )
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{
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// return as soon as the loop is detected
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if ( fVerbose )
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Abc_Print( 1, " %d ->", Aig_ObjId(pFanin) );
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return 0;
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}
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}
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// visit the transitive fanin
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pFanin = Aig_ObjFanin1(pNode);
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// check if the fanin is visited
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if ( !Aig_ObjIsTravIdPrevious(p, pFanin) )
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{
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// traverse the fanin's cone searching for the loop
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if ( !(fAcyclic = Aig_ManCheckAcyclic_rec(p, pFanin, fVerbose)) )
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{
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// return as soon as the loop is detected
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if ( fVerbose )
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Abc_Print( 1, " %d ->", Aig_ObjId(pFanin) );
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return 0;
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}
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}
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// visit choices
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if ( Aig_ObjRepr(p, pNode) == NULL && Aig_ObjEquiv(p, pNode) != NULL )
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{
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for ( pFanin = Aig_ObjEquiv(p, pNode); pFanin; pFanin = Aig_ObjEquiv(p, pFanin) )
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{
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// check if the fanin is visited
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if ( Aig_ObjIsTravIdPrevious(p, pFanin) )
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continue;
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// traverse the fanin's cone searching for the loop
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if ( (fAcyclic = Aig_ManCheckAcyclic_rec(p, pFanin, fVerbose)) )
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continue;
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// return as soon as the loop is detected
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if ( fVerbose )
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Abc_Print( 1, " %d", Aig_ObjId(pFanin) );
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if ( fVerbose )
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Abc_Print( 1, " (choice of %d) -> ", Aig_ObjId(pNode) );
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return 0;
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}
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}
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// mark this node as a visited node
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Aig_ObjSetTravIdPrevious( p, pNode );
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return 1;
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}
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/**Function*************************************************************
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Synopsis [Checks for combinational loops in the AIG.]
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Description [Returns 1 if there is no combinational loops.]
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SideEffects []
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SeeAlso []
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***********************************************************************/
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int Aig_ManCheckAcyclic( Aig_Man_t * p, int fVerbose )
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{
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Aig_Obj_t * pNode;
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int fAcyclic;
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int i;
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// set the traversal ID for this DFS ordering
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Aig_ManIncrementTravId( p );
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Aig_ManIncrementTravId( p );
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// pNode->TravId == pNet->nTravIds means "pNode is on the path"
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// pNode->TravId == pNet->nTravIds - 1 means "pNode is visited but is not on the path"
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// pNode->TravId < pNet->nTravIds - 1 means "pNode is not visited"
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// traverse the network to detect cycles
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fAcyclic = 1;
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Aig_ManForEachPo( p, pNode, i )
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{
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pNode = Aig_ObjFanin0(pNode);
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if ( Aig_ObjIsTravIdPrevious(p, pNode) )
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continue;
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// traverse the output logic cone
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if ( (fAcyclic = Aig_ManCheckAcyclic_rec(p, pNode, fVerbose)) )
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continue;
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// stop as soon as the first loop is detected
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if ( fVerbose )
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Abc_Print( 1, " CO %d\n", i );
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break;
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}
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return fAcyclic;
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}
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/**Function*************************************************************
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Synopsis [Removes combinational loop.]
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Description []
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SideEffects []
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SeeAlso []
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***********************************************************************/
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void Aig_ManFixLoopProblem( Aig_Man_t * p, int fVerbose )
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{
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Aig_Obj_t * pObj;
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int i, Counter = 0, Counter2 = 0;
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Aig_ManForEachObj( p, pObj, i )
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{
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if ( !Aig_ObjIsTravIdCurrent(p, pObj) )
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continue;
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Counter2++;
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if ( Aig_ObjRepr(p, pObj) == NULL && Aig_ObjEquiv(p, pObj) != NULL )
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{
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Aig_ObjSetEquiv(p, pObj, NULL);
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Counter++;
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}
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}
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if ( fVerbose )
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Abc_Print( 1, "Fixed %d choice nodes on the path with %d objects.\n", Counter, Counter2 );
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}
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/**Function*************************************************************
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Synopsis [Derives the AIG with choices from representatives.]
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@ -320,12 +479,20 @@ Aig_Man_t * Dch_DeriveChoiceAigInt( Aig_Man_t * pAig )
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***********************************************************************/
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Aig_Man_t * Dch_DeriveChoiceAig( Aig_Man_t * pAig )
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{
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extern int Aig_ManCheckAcyclic( Aig_Man_t * pAig, int fVerbose );
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Aig_Man_t * pChoices, * pTemp;
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int fVerbose = 0;
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pChoices = Dch_DeriveChoiceAigInt( pAig );
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// pChoices = Dch_DeriveChoiceAigInt( pTemp = pChoices );
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// Aig_ManStop( pTemp );
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// there is no need for cleanup
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ABC_FREE( pChoices->pReprs );
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while ( !Aig_ManCheckAcyclic( pChoices, fVerbose ) )
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{
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if ( fVerbose )
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Abc_Print( 1, "There is a loop!\n" );
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Aig_ManFixLoopProblem( pChoices, fVerbose );
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}
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pChoices = Aig_ManDupDfs( pTemp = pChoices );
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Aig_ManStop( pTemp );
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return pChoices;
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