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/base/geometry.py

@@ -86,8 +86,14 @@ class geometry:
         elif mirror == "XY":
             ll = ll.scale(-1, -1)
             ur = ur.scale(-1, -1)
+        elif mirror == "" or mirror == "R0":
+            pass
+        else:
+            debug.error("Invalid mirroring: {}".format(mirror), -1)
 
-        if rotate == 90:
+        if rotate == 0:
+            pass
+        elif rotate == 90:
             ll = ll.rotate_scale(-1, 1)
             ur = ur.rotate_scale(-1, 1)
         elif rotate == 180:
@@ -96,6 +102,8 @@ class geometry:
         elif rotate == 270:
             ll = ll.rotate_scale(1, -1)
             ur = ur.rotate_scale(1, -1)
+        else:
+            debug.error("Invalid rotation: {}".format(rotate), -1)
 
         self.boundary = [offset + ll, offset + ur]
         self.normalize()
@@ -139,6 +147,10 @@ class geometry:
     def cy(self):
         """ Return the center y """
         return 0.5 * (self.boundary[0].y + self.boundary[1].y)
+
+    def center(self):
+        """ Return the center coordinate """
+        return vector(self.cx(), self.cy())
     
 
 class instance(geometry):