llvm help

hi, comrades,

I was raising two questions:
1)ependence loop in SelectionDAG.

there is no loop in a DAG,but i did meet a situation there was a loop.

an example is a BR node targets a node after it in the chain.

to the BR node . the target node is an operand .
to the target node, the BR node is in the "Chain" pointed to by operand 0.

is it wro

2) Chain
in some nodes, operand 0 is a Chain.