/* * Copyright (c) 2004, 2005 * The Regents of The University of Michigan * All Rights Reserved * * This code is part of the M5 simulator, developed by Nathan Binkert, * Erik Hallnor, Steve Raasch, and Steve Reinhardt, with contributions * from Ron Dreslinski, Dave Greene, Lisa Hsu, Kevin Lim, Ali Saidi,  * and Andrew Schultz. * * Permission is granted to use, copy, create derivative works and * redistribute this software and such derivative works for any * purpose, so long as the copyright notice above, this grant of * permission, and the disclaimer below appear in all copies made; and * so long as the name of The University of Michigan is not used in * any advertising or publicity pertaining to the use or distribution * of this software without specific, written prior authorization. * * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION FROM THE * UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY PURPOSE, AND * WITHOUT WARRANTY BY THE UNIVERSITY OF MICHIGAN OF ANY KIND, EITHER * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE. THE REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE * LIABLE FOR ANY DAMAGES, INCLUDING DIRECT, SPECIAL, INDIRECT, * INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM * ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF SUCH * DAMAGES. */#include "base/intmath.hh"#include "base/trace.hh"#include "cpu/o3/btb.hh"DefaultBTB::DefaultBTB(unsigned _numEntries,                       unsigned _tagBits,                       unsigned _instShiftAmt)    : numEntries(_numEntries),      tagBits(_tagBits),      instShiftAmt(_instShiftAmt){    // @todo Check to make sure num_entries is valid (a power of 2)    DPRINTF(Fetch, "BTB: Creating BTB object.\n");    btb = new BTBEntry[numEntries];        for (int i = 0; i < numEntries; ++i)    {        btb[i].valid = false;    }    idxMask = numEntries - 1;    tagMask = (1 << tagBits) - 1;    tagShiftAmt = instShiftAmt + FloorLog2(numEntries);}inlineunsignedDefaultBTB::getIndex(const Addr &inst_PC){    // Need to shift PC over by the word offset.    return (inst_PC >> instShiftAmt) & idxMask;}inlineAddrDefaultBTB::getTag(const Addr &inst_PC){    return (inst_PC >> tagShiftAmt) & tagMask;}boolDefaultBTB::valid(const Addr &inst_PC){    unsigned btb_idx = getIndex(inst_PC);        Addr inst_tag = getTag(inst_PC);    assert(btb_idx < numEntries);    if (btb[btb_idx].valid && inst_tag == btb[btb_idx].tag) {        return true;    } else {        return false;    }}// @todo Create some sort of return struct that has both whether or not the// address is valid, and also the address.  For now will just use addr = 0 to// represent invalid entry.AddrDefaultBTB::lookup(const Addr &inst_PC){    unsigned btb_idx = getIndex(inst_PC);    Addr inst_tag = getTag(inst_PC);    assert(btb_idx < numEntries);     if (btb[btb_idx].valid && inst_tag == btb[btb_idx].tag) {        return btb[btb_idx].target;    } else {        return 0;    }}voidDefaultBTB::update(const Addr &inst_PC, const Addr &target){    unsigned btb_idx = getIndex(inst_PC);    assert(btb_idx < numEntries);        btb[btb_idx].valid = true;    btb[btb_idx].target = target;    btb[btb_idx].tag = getTag(inst_PC);}