1. An MtoL (behavioral model to layout information) method for converting an RTL (register transfer level) behavioral model in the form of an RTL module tree including a plurality of hierarchical RTL modules representing the logic structure and functionality of an integrated circuit, into MtoL layout information for use in a block router, comprising the steps: assigning to selected ones of the RTL modules MtoL macros that define corresponding geometric and terminal information; extracting these MtoL macros along with the RTL modules for inclusion in the MtoL extract tree; extracting from the RTL module tree the hierarchical RTL modules to create a corresponding hierarchical MtoL extract tree; performing a flattening transformation of the hierarchical Mtol extract tree to provide a non-hierarchical representation including a terminal interconnection netlist, said performing said flattening transformation accomplished by the substeps of performing a breadth first traversal through the hierarchical MtoL extract tree to create a linked list of all leaf nodes, which correspond to layout style blocks or intermediate blocks designated as leaf nodes, and performing a depth first search of the Mtol extract tree to generate a netlist that describes a routine network; and using the non-hierarchical representation and terminal interconnect netlist, generating MtoL layout information.