Merge pull request #626 from OpenXiangShan/resolve-queue-align

Resolve Queue Alignment in Kunminghu-v3

Author: Yakkhini

src/cpu/o3/BaseO3CPU.py

@@ -239,6 +239,7 @@ def support_take_over(cls):
 
     branchPred = Param.BranchPredictor(DecoupledBPUWithBTB(),
                                        "Branch Predictor")
+    resolveQueueSize = Param.Unsigned(16, "Number of entries in the branch resolution queue")
     needsTSO = Param.Bool(False, "Enable TSO Memory model")
 
     scheduler = Param.Scheduler("")

src/cpu/o3/iew.cc

@@ -92,6 +92,7 @@ IEW::IEW(CPU *_cpu, const BaseO3CPUParams &params)
       wbWidth(params.wbWidth),
       enableStoreSetTrain(params.enable_storeSet_train),
       numThreads(params.numThreads),
+      resolveQueueSize(params.resolveQueueSize),
       iewStats(cpu)
 {
     if (wbWidth > MaxWidth)
@@ -179,6 +180,13 @@ IEW::IEWStats::IEWStats(CPU *cpu)
              "Number of branches that were predicted taken incorrectly"),
     ADD_STAT(predictedNotTakenIncorrect, statistics::units::Count::get(),
              "Number of branches that were predicted not taken incorrectly"),
+    ADD_STAT(resolveQueueFullCycles, statistics::units::Count::get(),
+             "Number of cycles the resolve queue is full"),
+    ADD_STAT(resolveQueueFullEvents, statistics::units::Count::get(),
+             "Number of events the resolve queue becomes full"),
+    ADD_STAT(resolveEnqueueFailEvent, statistics::units::Count::get(),
+             "Number of times an instruction could not be enqueued to the "
+             "resolve queue"),
     ADD_STAT(branchMispredicts, statistics::units::Count::get(),
              "Number of branch mispredicts detected at execute",
              predictedTakenIncorrect + predictedNotTakenIncorrect),
@@ -1573,11 +1581,21 @@ IEW::SquashCheckAfterExe(DynInstPtr inst)
         }
     }
 
-    if (!found) {
+    if (!found && resolveQueue.size() < resolveQueueSize) {
         ResolveQueueEntry newEntry;
         newEntry.resolvedFSQId = fsqId;
         newEntry.resolvedInstPC.push_back(pc);
         resolveQueue.push_back(newEntry);
+        if (resolveQueue.size() == resolveQueueSize) {
+            iewStats.resolveQueueFullEvents++;
+        }
+    }
+
+    if (resolveQueue.size() >= resolveQueueSize) {
+        if (!found) {
+            iewStats.resolveEnqueueFailEvent++;
+        }
+        iewStats.resolveQueueFullCycles++;
     }
 
     if (!fetchRedirect[tid] ||
@@ -1793,10 +1811,9 @@ IEW::executeInsts()
         }
     }
 
-    sortResolveQueue();
     if (!resolveQueue.empty()) {
-        ResolveQueueEntry entry = resolveQueue.back();
-        resolveQueue.pop_back();
+        ResolveQueueEntry entry = resolveQueue.front();
+        resolveQueue.erase(resolveQueue.begin());
         toFetch->iewInfo[tid].resolveQueue.push_back(entry);
     }
 

src/cpu/o3/iew.hh

@@ -41,6 +41,7 @@
 #ifndef __CPU_O3_IEW_HH__
 #define __CPU_O3_IEW_HH__
 
+#include <cstdint>
 #include <deque>
 #include <map>
 #include <queue>
@@ -494,13 +495,8 @@ class IEW
     /** Maximum size of the skid buffer. */
     unsigned skidBufferMax;
 
+    unsigned resolveQueueSize;
     std::vector<ResolveQueueEntry> resolveQueue;
-    static inline bool resolveQueueEntryCompare(const ResolveQueueEntry &a, const ResolveQueueEntry &b)
-    {
-        return a.resolvedFSQId > b.resolvedFSQId;
-    };
-    inline void sortResolveQueue() { std::sort(resolveQueue.begin(), resolveQueue.end(), resolveQueueEntryCompare); };
-
 
     struct IEWStats : public statistics::Group
     {
@@ -534,6 +530,12 @@ class IEW
         statistics::Scalar predictedTakenIncorrect;
         /** Stat for total number of incorrect predicted not taken branches. */
         statistics::Scalar predictedNotTakenIncorrect;
+        /** Stat for total cycles the resolve queue is full. */
+        statistics::Scalar resolveQueueFullCycles;
+        /** Stat for total events of the resolve queue becomes full. */
+        statistics::Scalar resolveQueueFullEvents;
+        /** Stat for total number of enqueue fail events. */
+        statistics::Scalar resolveEnqueueFailEvent;
         /** Stat for total number of mispredicted branches detected at
          *  execute. */
         statistics::Formula branchMispredicts;