From 543efd5ca687782028fad8873099ad38eeb64085 Mon Sep 17 00:00:00 2001 From: Andrew Lukefahr Date: Tue, 15 Sep 2015 08:14:07 -0500 Subject: [PATCH] cpu: pred: Local Predictor Reset in Tournament Predictor When a branch gets squashed, it's speculative branch predictor state should get rolled back in squash(). However, only the globalHistory state was being rolled back. This patch adds (at least some) support for rolling back the local predictor state also. Committed by: Nilay Vaish --- src/cpu/pred/tournament.cc | 7 +++++++ src/cpu/pred/tournament.hh | 1 + 2 files changed, 8 insertions(+) diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc index 1d4fe037e..ea6be46fa 100644 --- a/src/cpu/pred/tournament.cc +++ b/src/cpu/pred/tournament.cc @@ -217,6 +217,7 @@ TournamentBP::lookup(Addr branch_addr, void * &bp_history) history->localPredTaken = local_prediction; history->globalPredTaken = global_prediction; history->globalUsed = choice_prediction; + history->localHistoryIdx = local_history_idx; history->localHistory = local_predictor_idx; bp_history = (void *)history; @@ -256,6 +257,7 @@ TournamentBP::uncondBranch(Addr pc, void * &bp_history) history->localPredTaken = true; history->globalPredTaken = true; history->globalUsed = true; + history->localHistoryIdx = invalidPredictorIndex; history->localHistory = invalidPredictorIndex; bp_history = static_cast(history); @@ -371,6 +373,11 @@ TournamentBP::squash(void *bp_history) // Restore global history to state prior to this branch. globalHistory = history->globalHistory; + // Restore local history + if (history->localHistoryIdx != invalidPredictorIndex) { + localHistoryTable[history->localHistoryIdx] = history->localHistory; + } + // Delete this BPHistory now that we're done with it. delete history; } diff --git a/src/cpu/pred/tournament.hh b/src/cpu/pred/tournament.hh index d46175610..8fb5b515c 100644 --- a/src/cpu/pred/tournament.hh +++ b/src/cpu/pred/tournament.hh @@ -167,6 +167,7 @@ class TournamentBP : public BPredUnit static int newCount; #endif unsigned globalHistory; + unsigned localHistoryIdx; unsigned localHistory; bool localPredTaken; bool globalPredTaken; -- 2.30.2