Add support for 512B instruction cache.
tree4acc8fc4cf44b5e5d6d958114abf933fa37d5f4f
drwxr-xr-x - bench
drwxr-xr-x - doc
drwxr-xr-x - lib
drwxr-xr-x - lint
drwxr-xr-x - rtl
drwxr-xr-x - sim
drwxr-xr-x - syn