add lut2bmux

tests/techmap/lut2bmux.ys

@@ -0,0 +1,22 @@
+read_rtlil << EOT
+module \top
+  wire width 4 input 0 \A
+  wire output 1 \Y
+
+  cell $lut $0
+    parameter \WIDTH 4
+    parameter \LUT 16'b0110100110010110
+    connect \A \A
+    connect \Y \Y
+  end
+end
+EOT
+
+hierarchy -auto-top
+
+# Prove lut2bmux preserves behavior
+equiv_opt -assert lut2bmux
+
+# And check the structural rewrite happened
+select -assert-count 0 t:$lut
+select -assert-count 1 t:$bmux r:WIDTH=1 r:S_WIDTH=4 %i