Clock: Rework clocks to avoid tick-to-cycle transformations

This patch introduces the notion of a clock update function that aims
to avoid costly divisions when turning the current tick into a
cycle. Each clocked object advances a private (hidden) cycle member
and a tick member and uses these to implement functions for getting
the tick of the next cycle, or the tick of a cycle some time in the
future.

In the different modules using the clocks, changes are made to avoid
counting in ticks only to later translate to cycles. There are a few
oddities in how the O3 and inorder CPU count idle cycles, as seen by a
few locations where a cycle is subtracted in the calculation. This is
done such that the regression does not change any stats, but should be
revisited in a future patch.

Another, much needed, change that is not done as part of this patch is
to introduce a new typedef uint64_t Cycle to be able to at least hint
at the unit of the variables counting Ticks vs Cycles. This will be
done as a follow-up patch.

As an additional follow up, the thread context still uses ticks for
the book keeping of last activate and last suspend and this should
probably also be changed into cycles as well.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/dev/i8254xGBe.cc b/src/dev/i8254xGBe.cc
index f7f6a1178..3ba140bce 100644
--- a/src/dev/i8254xGBe.cc
+++ b/src/dev/i8254xGBe.cc
@@ -2052,7 +2052,7 @@ IGbE::restartClock()
 {
     if (!tickEvent.scheduled() && (rxTick || txTick || txFifoTick) &&
         getState() == SimObject::Running)
-        schedule(tickEvent, (curTick() / ticks(1)) * ticks(1) + ticks(1));
+        schedule(tickEvent, clockEdge(1));
 }
 
 unsigned int
@@ -2434,7 +2434,7 @@ IGbE::tick()
 
 
     if (rxTick || txTick || txFifoTick)
-        schedule(tickEvent, curTick() + ticks(1));
+        schedule(tickEvent, curTick() + clockPeriod());
 }
 
 void