diff options
Diffstat (limited to 'src/cpu/pred/2bit_local.hh')
| -rw-r--r-- | src/cpu/pred/2bit_local.hh | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/src/cpu/pred/2bit_local.hh b/src/cpu/pred/2bit_local.hh new file mode 100644 index 000000000..8b7bb8463 --- /dev/null +++ b/src/cpu/pred/2bit_local.hh @@ -0,0 +1,110 @@ +/* + * Copyright (c) 2004-2006 The Regents of The University of Michigan + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution; + * neither the name of the copyright holders nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * Authors: Kevin Lim + */ + +#ifndef __CPU_O3_2BIT_LOCAL_PRED_HH__ +#define __CPU_O3_2BIT_LOCAL_PRED_HH__ + +#include <vector> + +#include "base/types.hh" +#include "cpu/o3/sat_counter.hh" + +/** + * Implements a local predictor that uses the PC to index into a table of + * counters. Note that any time a pointer to the bp_history is given, it + * should be NULL using this predictor because it does not have any branch + * predictor state that needs to be recorded or updated; the update can be + * determined solely by the branch being taken or not taken. + */ +class LocalBP +{ + public: + /** + * Default branch predictor constructor. + * @param localPredictorSize Size of the local predictor. + * @param localCtrBits Number of bits per counter. + * @param instShiftAmt Offset amount for instructions to ignore alignment. + */ + LocalBP(unsigned localPredictorSize, unsigned localCtrBits, + unsigned instShiftAmt); + + /** + * Looks up the given address in the branch predictor and returns + * a true/false value as to whether it is taken. + * @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. + */ + bool lookup(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. + */ + void update(Addr &branch_addr, bool taken, void *bp_history); + + void squash(void *bp_history) + { assert(bp_history == NULL); } + + void reset(); + + private: + /** + * Returns the taken/not taken prediction given the value of the + * counter. + * @param count The value of the counter. + * @return The prediction based on the counter value. + */ + inline bool getPrediction(uint8_t &count); + + /** Calculates the local index based on the PC. */ + inline unsigned getLocalIndex(Addr &PC); + + /** Array of counters that make up the local predictor. */ + std::vector<SatCounter> localCtrs; + + /** Size of the local predictor. */ + unsigned localPredictorSize; + + /** Number of sets. */ + unsigned localPredictorSets; + + /** Number of bits of the local predictor's counters. */ + unsigned localCtrBits; + + /** Number of bits to shift the PC when calculating index. */ + unsigned instShiftAmt; + + /** Mask to get index bits. */ + unsigned indexMask; +}; + +#endif // __CPU_O3_2BIT_LOCAL_PRED_HH__ |