Thin-cell decoder changes.

Add hard decoder gates (nand, inv, pnan)
Add conditions for routing using LI layer in s8.
Generalize bus layers for decoders.
Move custom cells to own directory.
Fixed via directions, etc.
Add 4x16 hierarchical decoder and test case

compiler/modules/tri_gate.py

@@ -1,50 +0,0 @@
-# See LICENSE for licensing information.
-#
-# Copyright (c) 2016-2019 Regents of the University of California and The Board
-# of Regents for the Oklahoma Agricultural and Mechanical College
-# (acting for and on behalf of Oklahoma State University)
-# All rights reserved.
-#
-import debug
-import design
-import utils
-from tech import GDS,layer
-
-class tri_gate(design.design):
-    """
-    This module implements the tri gate cell used in the design forS
-    bit-line isolation. It is a hand-made cell, so the layout and
-    netlist should be available in the technology library.  
-    """
-
-    pin_names = ["in", "out", "en", "en_bar", "vdd", "gnd"]
-    type_list = ["INPUT", "OUTPUT", "INPUT", "INPUT", "POWER", "GROUND"]
-    (width,height) = utils.get_libcell_size("tri_gate", GDS["unit"], layer["boundary"])
-    pin_map = utils.get_libcell_pins(pin_names, "tri_gate", GDS["unit"])
-
-    unique_id = 1
-    
-    def __init__(self, name=""):
-        if name=="":
-            name = "tri{0}".format(tri_gate.unique_id)
-            tri_gate.unique_id += 1
-        design.design.__init__(self, name)
-        debug.info(2, "Create tri_gate")
-
-        self.width = tri_gate.width
-        self.height = tri_gate.height
-        self.pin_map = tri_gate.pin_map
-        self.add_pin_types(self.type_list)
-
-    def analytical_power(self, corner, load):
-        """Returns dynamic and leakage power. Results in nW"""
-        #Power in this module currently not defined. Returns 0 nW (leakage and dynamic).
-        total_power = self.return_power() 
-        return total_power
-
-    def get_cin(self):
-        return 9*spice["min_tx_gate_c"]
-
-    def build_graph(self, graph, inst_name, port_nets):        
-        """Adds edges based on inputs/outputs. Overrides base class function."""
-        self.add_graph_edges(graph, port_nets)