Train ITTAGE at resolve stage (#630)

* cpu-o3: enable ITTAGE predictor

Change-Id: I6a01e4ecb12119e1d2040eff44f28ceeefb3886d

* cpu-o3: train ittage in resolve stage

Change-Id: Ie7812db8bc256535f019bd59e36d5688312122ef

* cpu-o3: filter not resolved btb entries in ittage resolve update

Change-Id: I13a7033fce6096dd2ad7a5e3c58f935486b28a63

* cpu-o3: only update ubtb & abtb when it enabled

Change-Id: If8ad467ec69fc727ce177a942ae3ebc10eceafbe

Author: Yakkhini

configs/example/kmhv3.py

@@ -97,13 +97,14 @@ def setKmhV3Params(args, system):
 
             cpu.branchPred.mbtb.resolvedUpdate = True
             cpu.branchPred.tage.resolvedUpdate = True
+            cpu.branchPred.ittage.resolvedUpdate = True
 
             cpu.branchPred.ubtb.enabled = True
             cpu.branchPred.abtb.enabled = True
             cpu.branchPred.microtage.enabled = False
             cpu.branchPred.mbtb.enabled = True
             cpu.branchPred.tage.enabled = True
-            cpu.branchPred.ittage.enabled = False
+            cpu.branchPred.ittage.enabled = True
             cpu.branchPred.mgsc.enabled = False
             cpu.branchPred.ras.enabled = False
 

src/cpu/pred/btb/btb_ittage.cc

@@ -219,10 +219,17 @@ BTBITTAGE::update(const FetchStream &stream)
         all_entries_to_update.push_back(stream.updateNewBTBEntry);
     }
 
-    // only update indirect branches that are not returns
-    auto remove_it = std::remove_if(all_entries_to_update.begin(), all_entries_to_update.end(),
-        [](const BTBEntry &e) { return !(e.isIndirect && !e.isReturn); });
-    all_entries_to_update.erase(remove_it, all_entries_to_update.end());
+    // // only update indirect branches that are not returns
+    if (getResolvedUpdate()) {
+        auto remove_it =
+            std::remove_if(all_entries_to_update.begin(), all_entries_to_update.end(),
+                           [](const BTBEntry &e) { return !(e.isIndirect && !e.isReturn && e.resolved); });
+        all_entries_to_update.erase(remove_it, all_entries_to_update.end());
+    } else {
+        auto remove_it = std::remove_if(all_entries_to_update.begin(), all_entries_to_update.end(),
+                                        [](const BTBEntry &e) { return !(e.isIndirect && !e.isReturn); });
+        all_entries_to_update.erase(remove_it, all_entries_to_update.end());
+    }
 
     // get tage predictions from meta
     // TODO: use component idx

src/cpu/pred/btb/decoupled_bpred.cc

@@ -251,15 +251,16 @@ DecoupledBPUWithBTB::generateFinalPredAndCreateBubbles()
 
     // update ubtb/abtb using final S3 prediction
     if (predsOfEachStage[numStages - 1].btbEntries.size() > 0) {
-        ubtb->updateUsingS3Pred(predsOfEachStage[numStages - 1]);
-        auto it = fetchStreamQueue.find(fsqId-1);
-        if (it != fetchStreamQueue.end()) {
+        if (ubtb->isEnabled()) {
+            ubtb->updateUsingS3Pred(predsOfEachStage[numStages - 1]);
+        }
+        auto it = fetchStreamQueue.find(fsqId - 1);
+        if (it != fetchStreamQueue.end() && abtb->isEnabled()) {
             auto previous_block_startpc = it->second.startPC;
             abtb->updateUsingS3Pred(predsOfEachStage[numStages - 1], previous_block_startpc);
-        } else {
+        } else if (abtb->isEnabled()) {
             abtb->updateUsingS3Pred(predsOfEachStage[numStages - 1], 0);
         }
-
     }
 
     // 4. Record override bubbles and update statistics