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.

2 files changed, 2 insertions, 2 deletions

diff --git a/src/cpu/testers/memtest/memtest.cc b/src/cpu/testers/memtest/memtest.cc
index 642af4677..f8a8b66bd 100644
--- a/src/cpu/testers/memtest/memtest.cc
+++ b/src/cpu/testers/memtest/memtest.cc
@@ -246,7 +246,7 @@ void
 MemTest::tick()
 {
     if (!tickEvent.scheduled())
-        schedule(tickEvent, curTick() + ticks(1));
+        schedule(tickEvent, clockEdge(1));
 
     if (++noResponseCycles >= 500000) {
         if (issueDmas) {
diff --git a/src/cpu/testers/networktest/networktest.cc b/src/cpu/testers/networktest/networktest.cc
index 5d0e8e0c9..05568b3c0 100644
--- a/src/cpu/testers/networktest/networktest.cc
+++ b/src/cpu/testers/networktest/networktest.cc
@@ -165,7 +165,7 @@ NetworkTest::tick()
         exitSimLoop("Network Tester completed simCycles");
     else {
         if (!tickEvent.scheduled())
-            schedule(tickEvent, curTick() + ticks(1));
+            schedule(tickEvent, clockEdge(1));
     }
 }