misc: Add secondary dot output for DVFS domains

This patch adds a secondary dot output file which shows the DVFS domains. This
has been done separately for now to avoid cluttering the already existing
diagram. Due to the way that the clock domains are assigned to components in
gem5, this output must be generated after the C++ objects have been
instantiated. This further motivates the need to generate this file separately
to the current dot output, and not to replace it entirely.

src/python/m5/simulate.py

@@ -51,7 +51,7 @@ import stats
 import SimObject
 import ticks
 import objects
-from m5.util.dot_writer import do_dot
+from m5.util.dot_writer import do_dot, do_dvfs_dot
 from m5.internal.stats import updateEvents as updateStatEvents
 
 from util import fatal
@@ -126,6 +126,11 @@ def instantiate(ckpt_dir=None):
     # Do a fifth pass to connect probe listeners
     for obj in root.descendants(): obj.regProbeListeners()
 
+    # We want to generate the DVFS diagram for the system. This can only be
+    # done once all of the CPP objects have been created and initialised so
+    # that we are able to figure out which object belongs to which domain.
+    do_dvfs_dot(root, options.outdir, options.dot_dvfs_config)
+
     # We're done registering statistics.  Enable the stats package now.
     stats.enable()