diff options
Diffstat (limited to 'src/cpu/pred')
| -rw-r--r-- | src/cpu/pred/2bit_local.cc | 8 | ||||
| -rw-r--r-- | src/cpu/pred/2bit_local.hh | 21 | ||||
| -rw-r--r-- | src/cpu/pred/tournament.cc | 86 | ||||
| -rw-r--r-- | src/cpu/pred/tournament.hh | 28 |
4 files changed, 108 insertions, 35 deletions
diff --git a/src/cpu/pred/2bit_local.cc b/src/cpu/pred/2bit_local.cc index dc8cf50b7..4d18c419b 100644 --- a/src/cpu/pred/2bit_local.cc +++ b/src/cpu/pred/2bit_local.cc @@ -79,6 +79,14 @@ LocalBP::reset() } } +void +LocalBP::BTBUpdate(Addr &branch_addr, void * &bp_history) +{ +// Place holder for a function that is called to update predictor history when +// a BTB entry is invalid or not found. +} + + bool LocalBP::lookup(Addr &branch_addr, void * &bp_history) { diff --git a/src/cpu/pred/2bit_local.hh b/src/cpu/pred/2bit_local.hh index 8b7bb8463..01a0b64db 100644 --- a/src/cpu/pred/2bit_local.hh +++ b/src/cpu/pred/2bit_local.hh @@ -1,4 +1,16 @@ /* + * Copyright (c) 2011 ARM Limited + * All rights reserved + * + * The license below extends only to copyright in the software and shall + * not be construed as granting a license to any other intellectual + * property including but not limited to intellectual property relating + * to a hardware implementation of the functionality of the software + * licensed hereunder. You may use the software subject to the license + * terms below provided that you ensure that this notice is replicated + * unmodified and in its entirety in all distributions of the software, + * modified or unmodified, in source code or in binary form. + * * Copyright (c) 2004-2006 The Regents of The University of Michigan * All rights reserved. * @@ -65,6 +77,15 @@ class LocalBP bool lookup(Addr &branch_addr, void * &bp_history); /** + * Updates the branch predictor to Not Taken if a BTB entry is + * invalid or not found. + * @param branch_addr The address of the branch to look up. + * @param bp_history Pointer to any bp history state. + * @return Whether or not the branch is taken. + */ + void BTBUpdate(Addr &branch_addr, void * &bp_history); + + /** * Updates the branch predictor with the actual result of a branch. * @param branch_addr The address of the branch to update. * @param taken Whether or not the branch was taken. diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc index 9608dc011..3adafb608 100644 --- a/src/cpu/pred/tournament.cc +++ b/src/cpu/pred/tournament.cc @@ -1,4 +1,16 @@ /* + * Copyright (c) 2011 ARM Limited + * All rights reserved + * + * The license below extends only to copyright in the software and shall + * not be construed as granting a license to any other intellectual + * property including but not limited to intellectual property relating + * to a hardware implementation of the functionality of the software + * licensed hereunder. You may use the software subject to the license + * terms below provided that you ensure that this notice is replicated + * unmodified and in its entirety in all distributions of the software, + * modified or unmodified, in source code or in binary form. + * * Copyright (c) 2004-2006 The Regents of The University of Michigan * All rights reserved. * @@ -146,6 +158,18 @@ TournamentBP::updateLocalHistNotTaken(unsigned local_history_idx) (localHistoryTable[local_history_idx] << 1); } + +void +TournamentBP::BTBUpdate(Addr &branch_addr, void * &bp_history) +{ + unsigned local_history_idx = calcLocHistIdx(branch_addr); + //Update Global History to Not Taken + globalHistory = globalHistory & (globalHistoryMask - 1); + //Update Local History to Not Taken + localHistoryTable[local_history_idx] = + localHistoryTable[local_history_idx] & (localPredictorMask - 1); +} + bool TournamentBP::lookup(Addr &branch_addr, void * &bp_history) { @@ -174,6 +198,7 @@ TournamentBP::lookup(Addr &branch_addr, void * &bp_history) history->localPredTaken = local_prediction; history->globalPredTaken = global_prediction; history->globalUsed = choice_prediction; + history->localHistory = local_predictor_idx; bp_history = (void *)history; assert(globalHistory < globalPredictorSize && @@ -184,30 +209,22 @@ TournamentBP::lookup(Addr &branch_addr, void * &bp_history) // all histories. if (choice_prediction) { if (global_prediction) { -// updateHistoriesTaken(local_history_idx); -// globalCtrs[globalHistory].increment(); -// localCtrs[local_history_idx].increment(); updateGlobalHistTaken(); + updateLocalHistTaken(local_history_idx); return true; } else { -// updateHistoriesNotTaken(local_history_idx); -// globalCtrs[globalHistory].decrement(); -// localCtrs[local_history_idx].decrement(); updateGlobalHistNotTaken(); + updateLocalHistNotTaken(local_history_idx); return false; } } else { if (local_prediction) { -// updateHistoriesTaken(local_history_idx); -// globalCtrs[globalHistory].increment(); -// localCtrs[local_history_idx].increment(); updateGlobalHistTaken(); + updateLocalHistTaken(local_history_idx); return true; } else { -// updateHistoriesNotTaken(local_history_idx); -// globalCtrs[globalHistory].decrement(); -// localCtrs[local_history_idx].decrement(); updateGlobalHistNotTaken(); + updateLocalHistNotTaken(local_history_idx); return false; } } @@ -222,16 +239,18 @@ TournamentBP::uncondBr(void * &bp_history) history->localPredTaken = true; history->globalPredTaken = true; history->globalUsed = true; + history->localHistory = invalidPredictorIndex; bp_history = static_cast<void *>(history); updateGlobalHistTaken(); } void -TournamentBP::update(Addr &branch_addr, bool taken, void *bp_history) +TournamentBP::update(Addr &branch_addr, bool taken, void *bp_history, + bool squashed) { unsigned local_history_idx; - unsigned local_predictor_idx; + unsigned local_predictor_idx M5_VAR_USED; unsigned local_predictor_hist; // Get the local predictor's current prediction @@ -259,33 +278,34 @@ TournamentBP::update(Addr &branch_addr, bool taken, void *bp_history) // resolution of the branch. Global history is updated // speculatively and restored upon squash() calls, so it does not // need to be updated. + unsigned old_local_pred_index = history->localHistory + & localPredictorMask; if (taken) { - localCtrs[local_predictor_idx].increment(); globalCtrs[history->globalHistory].increment(); - - updateLocalHistTaken(local_history_idx); + if (old_local_pred_index != invalidPredictorIndex) { + localCtrs[old_local_pred_index].increment(); + } } else { - localCtrs[local_predictor_idx].decrement(); globalCtrs[history->globalHistory].decrement(); - - updateLocalHistNotTaken(local_history_idx); + if (old_local_pred_index != invalidPredictorIndex) { + localCtrs[old_local_pred_index].decrement(); + } } - bool mispredict = false; - - //global predictor used and mispredicted - if (history->globalUsed && history->globalPredTaken != taken) - mispredict = true; - //local predictor used and mispredicted - else if (!history->globalUsed && history->localPredTaken != taken) - mispredict = true; - - if (mispredict) { + if (squashed) { if (taken) { - globalHistory = globalHistory | 1; + globalHistory = (history->globalHistory << 1) | 1; + globalHistory = globalHistory & globalHistoryMask; + if (history->localHistory != invalidPredictorIndex) + localHistoryTable[local_history_idx] = + (history->localHistory << 1) | 1; } else { - unsigned mask = globalHistoryMask - 1; - globalHistory = globalHistory & mask; + globalHistory = (history->globalHistory << 1); + globalHistory = globalHistory & globalHistoryMask; + if (history->localHistory != invalidPredictorIndex) { + localHistoryTable[local_history_idx] = + history->localHistory << 1; + } } } diff --git a/src/cpu/pred/tournament.hh b/src/cpu/pred/tournament.hh index 96bd43ed6..f9df2a61d 100644 --- a/src/cpu/pred/tournament.hh +++ b/src/cpu/pred/tournament.hh @@ -1,4 +1,16 @@ /* + * Copyright (c) 2011 ARM Limited + * All rights reserved + * + * The license below extends only to copyright in the software and shall + * not be construed as granting a license to any other intellectual + * property including but not limited to intellectual property relating + * to a hardware implementation of the functionality of the software + * licensed hereunder. You may use the software subject to the license + * terms below provided that you ensure that this notice is replicated + * unmodified and in its entirety in all distributions of the software, + * modified or unmodified, in source code or in binary form. + * * Copyright (c) 2004-2006 The Regents of The University of Michigan * All rights reserved. * @@ -79,15 +91,24 @@ class TournamentBP * @param bp_history Pointer that will be set to the BPHistory object. */ void uncondBr(void * &bp_history); - + /** + * Updates the branch predictor to Not Taken if a BTB entry is + * invalid or not found. + * @param branch_addr The address of the branch to look up. + * @param bp_history Pointer to any bp history state. + * @return Whether or not the branch is taken. + */ + void BTBUpdate(Addr &branch_addr, void * &bp_history); /** * Updates the branch predictor with the actual result of a branch. * @param branch_addr The address of the branch to update. * @param taken Whether or not the branch was taken. * @param bp_history Pointer to the BPHistory object that was created * when the branch was predicted. + * @param squashed is set when this function is called during a squash + * operation. */ - void update(Addr &branch_addr, bool taken, void *bp_history); + void update(Addr &branch_addr, bool taken, void *bp_history, bool squashed); /** * Restores the global branch history on a squash. @@ -149,11 +170,14 @@ class TournamentBP static int newCount; #endif unsigned globalHistory; + unsigned localHistory; bool localPredTaken; bool globalPredTaken; bool globalUsed; }; + /** Flag for invalid predictor index */ + static const int invalidPredictorIndex = -1; /** Local counters. */ std::vector<SatCounter> localCtrs; |