From 65f63e7b69cdd906e1fc48056bb365bd687c3e44 Mon Sep 17 00:00:00 2001
From: Daniel Gerzhoy <daniel.gerzhoy@gmail.com>
Date: Tue, 3 Nov 2020 15:28:18 -0500
Subject: [PATCH] cpu-o3: Fixed halt assertion failure

Halting the O3 CPU would cause an assertion failure because
instructions were not finished being squashed in the ROB.

Change-Id: I8b8c375d0e520861af3657249de987de2451b6f1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/37676
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/cpu/o3/cpu.cc      | 18 ++++++++++++++++++
 src/cpu/o3/rob_impl.hh | 12 +++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/cpu/o3/cpu.cc b/src/cpu/o3/cpu.cc
index c910cc487..4068b306d 100644
--- a/src/cpu/o3/cpu.cc
+++ b/src/cpu/o3/cpu.cc
@@ -717,6 +717,15 @@ FullO3CPU<Impl>::haltContext(ThreadID tid)
     deactivateThread(tid);
     removeThread(tid);
 
+    // If this was the last thread then unschedule the tick event.
+    if (activeThreads.size() == 0) {
+        if (tickEvent.scheduled())
+        {
+            unscheduleTickEvent();
+        }
+        lastRunningCycle = curCycle();
+        _status = Idle;
+    }
     updateCycleCounters(BaseCPU::CPU_STATE_SLEEP);
 }
 
@@ -795,6 +804,15 @@ FullO3CPU<Impl>::removeThread(ThreadID tid)
     rename.clearStates(tid);
     iew.clearStates(tid);
 
+    // Flush out any old data from the time buffers.
+    for (int i = 0; i < timeBuffer.getSize(); ++i) {
+        timeBuffer.advance();
+        fetchQueue.advance();
+        decodeQueue.advance();
+        renameQueue.advance();
+        iewQueue.advance();
+    }
+
     // at this step, all instructions in the pipeline should be already
     // either committed successfully or squashed. All thread-specific
     // queues in the pipeline must be empty.
diff --git a/src/cpu/o3/rob_impl.hh b/src/cpu/o3/rob_impl.hh
index d4a02b598..73c8a4bff 100644
--- a/src/cpu/o3/rob_impl.hh
+++ b/src/cpu/o3/rob_impl.hh
@@ -338,8 +338,18 @@ ROB<Impl>::doSquash(ThreadID tid)
 
     bool robTailUpdate = false;
 
+    unsigned int numInstsToSquash = squashWidth;
+
+    // If the CPU is exiting, squash all of the instructions
+    // it is told to, even if that exceeds the squashWidth.
+    // Set the number to the number of entries (the max).
+    if (cpu->isThreadExiting(tid))
+    {
+        numInstsToSquash = numEntries;
+    }
+
     for (int numSquashed = 0;
-         numSquashed < squashWidth &&
+         numSquashed < numInstsToSquash &&
          squashIt[tid] != instList[tid].end() &&
          (*squashIt[tid])->seqNum > squashedSeqNum[tid];
          ++numSquashed)
-- 
2.30.2