Making 'fold' and 'unfold' skip constant POs.

src/aig/saig/saigConstr.c

@@ -283,6 +283,8 @@ Aig_Man_t * Saig_ManDupUnfoldConstrs( Aig_Man_t * pAig )
     vConsAll = Vec_PtrAlloc( Saig_ManPoNum(pAig) );
     Saig_ManForEachPo( pAig, pObj, i )
     {
+        if ( Aig_ObjFanin0(pObj) == Aig_ManConst1(pAig) )
+            continue;
         RetValue = Saig_ManDetectConstr( pAig, i, &vOuts, &vCons );
         if ( RetValue == 0 )
         {
@@ -392,6 +394,8 @@ Aig_Man_t * Saig_ManDupFoldConstrs( Aig_Man_t * pAig, Vec_Int_t * vConstrs )
     // create primary output
     Saig_ManForEachPo( pAig, pObj, i )
     {
+        if ( Aig_ObjFanin0(pObj) == Aig_ManConst1(pAig) )
+            continue;
         pMiter = Aig_And( pAigNew, Aig_ObjChild0Copy(pObj), Aig_Not(pFlopIn) );
         Aig_ObjCreateCo( pAigNew, pMiter );
     }