From 63a80179f45f34a203417dff2ff00fd5b2fb8996 Mon Sep 17 00:00:00 2001
From: Yan Yue <1131531947@qq.com>
Date: Wed, 28 Jan 2026 10:23:41 +0800
Subject: [PATCH 1/3] bpu: sc: test sc again

Change-Id: Ifd14d575e4d45744a2582d42d903904f4f77d1d6
---
 configs/example/kmhv3.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configs/example/kmhv3.py b/configs/example/kmhv3.py
index 71844d9478..c5cad62a29 100644
--- a/configs/example/kmhv3.py
+++ b/configs/example/kmhv3.py
@@ -105,7 +105,7 @@ def setKmhV3Params(args, system):
             cpu.branchPred.mbtb.enabled = True
             cpu.branchPred.tage.enabled = True
             cpu.branchPred.ittage.enabled = True
-            cpu.branchPred.mgsc.enabled = False
+            cpu.branchPred.mgsc.enabled = True
             cpu.branchPred.ras.enabled = True
 
         # l1 cache per core

From 5871427e72c5e30a65c3ed6cd23e2850924b2ddf Mon Sep 17 00:00:00 2001
From: Yan Yue <1131531947@qq.com>
Date: Tue, 27 Jan 2026 14:52:50 +0800
Subject: [PATCH 2/3] bpu: sc: try to use bigger threshold

from max 1024 to max 4096

Change-Id: Ic303d37dabcf4d4ee37dc8f8093cb65ad83de32a
---
 src/cpu/pred/BranchPredictor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/cpu/pred/BranchPredictor.py b/src/cpu/pred/BranchPredictor.py
index a5132f48af..c79ffa47f5 100644
--- a/src/cpu/pred/BranchPredictor.py
+++ b/src/cpu/pred/BranchPredictor.py
@@ -1126,7 +1126,7 @@ class BTBMGSC(TimedBaseBTBPredictor):
     thresholdTablelogSize = Param.Unsigned(6,
         "Log size of update threshold counters tables")
 
-    updateThresholdWidth = Param.Unsigned(12,
+    updateThresholdWidth = Param.Unsigned(14,
         "Number of bits for the update threshold counter")
 
     pUpdateThresholdWidth = Param.Unsigned(8,

From 34f1ac8af9822b8ce60eedc745255dd3cf552f6a Mon Sep 17 00:00:00 2001
From: Yan Yue <1131531947@qq.com>
Date: Tue, 27 Jan 2026 14:57:15 +0800
Subject: [PATCH 3/3] bpu: sc: ensure threadhold is positive

Change-Id: I9aa1d222463d6411b7481d3c93e7fd4fec17a039
---
 src/cpu/pred/btb/btb_mgsc.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/cpu/pred/btb/btb_mgsc.cc b/src/cpu/pred/btb/btb_mgsc.cc
index 694bb0b3c1..50c5ae1397 100755
--- a/src/cpu/pred/btb/btb_mgsc.cc
+++ b/src/cpu/pred/btb/btb_mgsc.cc
@@ -413,6 +413,9 @@ BTBMGSC::generateSinglePrediction(const BTBEntry &btb_entry, const Addr &startPC
     int p_update_thres = enablePCThreshold ? findThreshold(pUpdateThreshold, btb_entry.pc) : 0;
 
     int total_thres = (updateThreshold / 8) + p_update_thres;
+    // Threshold is used as a confidence gate; avoid negative values which
+    // effectively disable the gate (abs(sum) > negative is almost always true).
+    total_thres = std::max(total_thres, 0);
 
     bool use_sc_pred = forceUseSC;  // Force use SC if configured
     if (!use_sc_pred) {
@@ -656,6 +659,11 @@ void
 BTBMGSC::updateGlobalThreshold(Addr pc, bool update_direction)
 {
     updateCounter(update_direction, updateThresholdWidth, updateThreshold);
+    // Keep global threshold non-negative; negative thresholds make SC gating
+    // degenerate and can cause overuse of SC.
+    if (updateThreshold < 0) {
+        updateThreshold = 0;
+    }
 }
 
 void