cpu-o3: fix rob head ready

Commit instruction after all instructions of head group becomes ready

Change-Id: I29c4927811e25c2e13ede8f640922b3228eae30b

src/cpu/o3/commit.cc

@@ -1109,6 +1109,10 @@ Commit::commitInsts()
 
     int commit_width = rob->numInstCanCommit(commitWidth);
 
+    if (commit_width >= 0) {
+        cpu->activityThisCycle();
+    }
+
     // Commit as many instructions as possible until the commit bandwidth
     // limit is reached, or it becomes impossible to commit any more.
     while (num_committed < commit_width) {

src/cpu/o3/rob.cc

@@ -357,7 +357,12 @@ ROB::isHeadReady(ThreadID tid)
     stats.reads++;
 
     if (!threadGroups[tid].empty() && threadGroups[tid].front() != 0) {
-        return instList[tid].front()->readyToCommit();
+        // check if all insts in the same head group are ready to commit
+        return std::all_of(
+            instList[tid].begin(),
+            std::next(instList[tid].begin(), threadGroups[tid].front()),
+            [] (DynInstPtr inst) { return inst->readyToCommit(); }
+        );
     }
 
     return false;

src/cpu/o3/rob.hh

@@ -161,7 +161,7 @@ class ROB
     /** Is the oldest instruction across all threads ready. */
 //    bool isHeadReady();
 
-    /** Is the oldest instruction across a particular thread ready. */
+    /** Is the oldest group of instructions across a particular thread ready. */
     bool isHeadReady(ThreadID tid);
 
     /** Is there any commitable head instruction across all threads ready. */