2bit_local.hh revision 1717
1/* 2 * Copyright (c) 2004-2005 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29#ifndef __CPU_BETA_CPU_2BIT_LOCAL_PRED_HH__ 30#define __CPU_BETA_CPU_2BIT_LOCAL_PRED_HH__ 31 32// For Addr type. 33#include "arch/alpha/isa_traits.hh" 34#include "cpu/o3/sat_counter.hh" 35 36class DefaultBP 37{ 38 public: 39 /** 40 * Default branch predictor constructor. 41 */ 42 DefaultBP(unsigned localPredictorSize, unsigned localCtrBits, 43 unsigned instShiftAmt); 44 45 /** 46 * Looks up the given address in the branch predictor and returns 47 * a true/false value as to whether it is taken. 48 * @param branch_addr The address of the branch to look up. 49 * @return Whether or not the branch is taken. 50 */ 51 bool lookup(Addr &branch_addr); 52 53 /** 54 * Updates the branch predictor with the actual result of a branch. 55 * @param branch_addr The address of the branch to update. 56 * @param taken Whether or not the branch was taken. 57 */ 58 void update(Addr &branch_addr, bool taken); 59 60 private: 61 62 /** Returns the taken/not taken prediction given the value of the 63 * counter. 64 */ 65 inline bool getPrediction(uint8_t &count); 66 67 /** Calculates the local index based on the PC. */ 68 inline unsigned getLocalIndex(Addr &PC); 69 70 /** Array of counters that make up the local predictor. */ 71 SatCounter *localCtrs; 72 73 /** Size of the local predictor. */ 74 unsigned localPredictorSize; 75 76 /** Number of bits of the local predictor's counters. */ 77 unsigned localCtrBits; 78 79 /** Number of bits to shift the PC when calculating index. */ 80 unsigned instShiftAmt; 81 82 /** Mask to get index bits. */ 83 unsigned indexMask; 84}; 85 86#endif // __CPU_BETA_CPU_2BIT_LOCAL_PRED_HH__ 87