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, 1 insertions, 1 deletions

diff --git a/src/cpu/o3/inst_queue_impl.hh b/src/cpu/o3/inst_queue_impl.hh
index ae5f93c38..b6c3bd239 100644
--- a/src/cpu/o3/inst_queue_impl.hh
+++ b/src/cpu/o3/inst_queue_impl.hh
@@ -828,7 +828,7 @@ InstructionQueue<Impl>::scheduleReadyInsts()
                 FUCompletion *execution = new FUCompletion(issuing_inst,
                                                            idx, this);
 
-                cpu->schedule(execution, curTick() + cpu->ticks(op_latency - 1));
+                cpu->schedule(execution, cpu->clockEdge(op_latency - 1));
 
                 // @todo: Enforce that issue_latency == 1 or op_latency
                 if (issue_latency > 1) {