cpu-o3: enable2Taken configure option

Change-Id: Id8896d4c28af5c11e71e3ef453068cd84231e468

Author: Yakkhini

configs/example/idealkmhv3.py

@@ -86,6 +86,7 @@ def setKmhV3IdealParams(args, system):
             cpu.branchPred.ftq_size = 64
             cpu.branchPred.fsq_size = 64
             # cpu.branchPred.microtage.enabled = False
+            cpu.branchPred.enable2Taken = True
             cpu.branchPred.enable2Fetch = True
 
         # l1 cache per core

configs/example/kmhv3.py

@@ -112,6 +112,7 @@ def setKmhV3Params(args, system):
             cpu.branchPred.ittage.enabled = True
             cpu.branchPred.mgsc.enabled = True
             cpu.branchPred.ras.enabled = True
+            cpu.branchPred.enable2Taken = True
             cpu.branchPred.enable2Fetch = True
 
             # RTL alignment: only enable bias + path + IMLI tables, disable PC threshold

src/cpu/pred/BranchPredictor.py

@@ -1207,5 +1207,6 @@ class DecoupledBPUWithBTB(BranchPredictor):
     bpDBSwitches = VectorParam.String([], "Enable which traces in the form of database")
     resolveBlockThreshold = Param.Unsigned(8, "Consecutive resolve dequeue failures before blocking prediction once")
 
+    enable2Taken = Param.Bool(True, "Enable 2taken feature")
     enable2Fetch = Param.Bool(False, "Enable 2fetch feature")
     maxFetchBytesPerCycle = Param.Unsigned(64, "Maximum fetch bytes per cycle for 2fetch")

src/cpu/pred/btb/decoupled_bpred.cc

@@ -48,6 +48,7 @@ DecoupledBPUWithBTB::DecoupledBPUWithBTB(const DecoupledBPUWithBTBParams &p)
       ftq(2, p.ftq_size),
       historyManager(16), // TODO: fix this
       resolveBlockThreshold(p.resolveBlockThreshold),
+      enable2Taken(p.enable2Taken),
       enable2Fetch(p.enable2Fetch),
       maxFetchBytesPerCycle(p.maxFetchBytesPerCycle),
       dbpBtbStats(this, p.numStages, p.fsq_size, maxInstsNum)
@@ -145,7 +146,7 @@ DecoupledBPUWithBTB::tick()
         return;
     }
 
-    int predsRemainsToBeMade = enableTwoTaken ? 2 : 1;
+    int predsRemainsToBeMade = enable2Taken ? 2 : 1;
     while (predsRemainsToBeMade > 0) {
         // 1. Request new prediction if FSQ not full and we are idle
         if (!threads[curTid].validprediction && !ftq.full(curTid)) {

src/cpu/pred/btb/decoupled_bpred.hh

@@ -146,12 +146,11 @@ class DecoupledBPUWithBTB : public BPredUnit
     const unsigned resolveBlockThreshold;
 
     ThreadID scheduleThread() { return 0; }
+    const bool enable2Taken;
     const bool enable2Fetch;
     const unsigned maxFetchBytesPerCycle;
 
     void processNewPrediction(ThreadID tid);
-    bool enableTwoTaken{true};
-
     FetchTarget createFetchTargetEntry(ThreadID tid);
 
     void updateHistoryForPrediction(FetchTarget &entry);