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Diffstat (limited to 'src/cpu/o3/2bit_local_pred.hh')
-rw-r--r-- | src/cpu/o3/2bit_local_pred.hh | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/src/cpu/o3/2bit_local_pred.hh b/src/cpu/o3/2bit_local_pred.hh new file mode 100644 index 000000000..97433e542 --- /dev/null +++ b/src/cpu/o3/2bit_local_pred.hh @@ -0,0 +1,86 @@ +/* + * Copyright (c) 2004-2005 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. + */ + +#ifndef __CPU_O3_CPU_2BIT_LOCAL_PRED_HH__ +#define __CPU_O3_CPU_2BIT_LOCAL_PRED_HH__ + +// For Addr type. +#include "arch/isa_traits.hh" +#include "cpu/o3/sat_counter.hh" + +class DefaultBP +{ + public: + /** + * Default branch predictor constructor. + */ + DefaultBP(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. + * @return Whether or not the branch is taken. + */ + bool lookup(Addr &branch_addr); + + /** + * 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); + + private: + + /** Returns the taken/not taken prediction given the value of the + * counter. + */ + 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. */ + SatCounter *localCtrs; + + /** Size of the local predictor. */ + unsigned localPredictorSize; + + /** 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_CPU_2BIT_LOCAL_PRED_HH__ |