Tie-High/Tie-Low Cells

Removing Tie Cells
Use the remove_tie_cells cmd if you want to remove any tie cells, which are preexisting in the design or inserted by the tool. The cmd replaces the original tie cell connections with proper direct tie-off connections and removes the tie cells.

The syntax is:
remove_tie_cells [-use_default_tie_net] list_of_tie_cells

To reconnect a leaf pin and a hierachical pin to tie-off, the tie net to be created or reused by 

remove_tie_cells is a direct tie net. A tie-off net named SNPS_LOGIC1 or SNPS_LOGIC0 is a direct tie net and is written out by the verilog writer as 1'b1 or 1'b0, respectively.

To connect to a hierarchical port, the tie net to be created by remove_tie_cells is an indirect tie net. A tie net named other than SNPS_LOGIC1 or SNPS_LOGIC0 is an indirect tie net. If the hierarchical port name is Q, the indirect tie-high net name created by this cmd is Q_SNPS_LOGIC1.

Tie-off connection during remove_tie_cells