cpu: Fix incorrect speculative branch predictor behavior

When a branch mispredicted gem5 would squash all history after and including
the mispredicted branch.  However, the mispredicted branch is still speculative
and its history is required to rollback state if another, older, branch
mispredicts.  This leads to things like RAS corruption.

1 files changed, 11 insertions, 4 deletions

diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc
index e471d08f5..c6514b6ad 100644
--- a/src/cpu/pred/tournament.cc
+++ b/src/cpu/pred/tournament.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011 ARM Limited
+ * Copyright (c) 2011, 2014 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -346,10 +346,10 @@ TournamentBP::update(Addr branch_addr, bool taken, void *bp_history,
                 }
              }
 
+        } else {
+            // We're done with this history, now delete it.
+            delete history;
         }
-        // We're done with this history, now delete it.
-        delete history;
-
     }
 
     assert(local_history_idx < localHistoryTableSize);
@@ -358,6 +358,13 @@ TournamentBP::update(Addr branch_addr, bool taken, void *bp_history,
 }
 
 void
+TournamentBP::retireSquashed(void *bp_history)
+{
+    BPHistory *history = static_cast<BPHistory *>(bp_history);
+    delete history;
+}
+
+void
 TournamentBP::squash(void *bp_history)
 {
     BPHistory *history = static_cast<BPHistory *>(bp_history);