cpu: Add drain check functionality to IEW

IEW did not check the instQueue and memDepUnit to ensure
they were drained.  This caused issues when drainSanityCheck()
did check those structures after asserting IEW was drained.

src/cpu/o3/iew_impl.hh

@@ -381,7 +381,7 @@ template <class Impl>
 bool
 DefaultIEW<Impl>::isDrained() const
 {
-    bool drained(ldstQueue.isDrained());
+    bool drained = ldstQueue.isDrained() && instQueue.isDrained();
 
     for (ThreadID tid = 0; tid < numThreads; tid++) {
         if (!insts[tid].empty()) {

src/cpu/o3/inst_queue.hh

@@ -145,6 +145,9 @@ class InstructionQueue
     /** Sets the global time buffer. */
     void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
 
+    /** Determine if we are drained. */
+    bool isDrained() const;
+
     /** Perform sanity checks after a drain. */
     void drainSanityCheck() const;
 

src/cpu/o3/inst_queue_impl.hh

@@ -440,6 +440,17 @@ InstructionQueue<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr)
     fromCommit = timeBuffer->getWire(-commitToIEWDelay);
 }
 
+template <class Impl>
+bool
+InstructionQueue<Impl>::isDrained() const
+{
+    bool drained = dependGraph.empty() && instsToExecute.empty();
+    for (ThreadID tid = 0; tid < numThreads; ++tid)
+        drained = drained && memDepUnit[tid].isDrained();
+
+    return drained;
+}
+
 template <class Impl>
 void
 InstructionQueue<Impl>::drainSanityCheck() const

src/cpu/o3/mem_dep_unit.hh

@@ -104,6 +104,9 @@ class MemDepUnit
     /** Registers statistics. */
     void regStats();
 
+    /** Determine if we are drained. */
+    bool isDrained() const;
+
     /** Perform sanity checks after a drain. */
     void drainSanityCheck() const;
 

src/cpu/o3/mem_dep_unit_impl.hh

@@ -127,6 +127,19 @@ MemDepUnit<MemDepPred, Impl>::regStats()
         .desc("Number of conflicting stores.");
 }
 
+template <class MemDepPred, class Impl>
+bool
+MemDepUnit<MemDepPred, Impl>::isDrained() const
+{
+    bool drained = instsToReplay.empty()
+                 && memDepHash.empty()
+                 && instsToReplay.empty();
+    for (int i = 0; i < Impl::MaxThreads; ++i)
+        drained = drained && instList[i].empty();
+
+    return drained;
+}
+
 template <class MemDepPred, class Impl>
 void
 MemDepUnit<MemDepPred, Impl>::drainSanityCheck() const