Load-op-Store fusion has an output edge from a non-root node
(i.e. from the Op). Users of this value may have a Id smaller than
some inputs (i.e. the store's chain) violating the topological
ordering of node ids (if both a node and it's operand have valid ids,
the operand's id will be strictly smaller) which we rely on for
pruning cycle detection. In such cases invalidate the ids of
successor nodes as necessary.