btb.cc revision 6226:f1076450ab2b
112855Sgabeblack@google.com/* 212855Sgabeblack@google.com * Copyright (c) 2004-2005 The Regents of The University of Michigan 312855Sgabeblack@google.com * All rights reserved. 412855Sgabeblack@google.com * 512855Sgabeblack@google.com * Redistribution and use in source and binary forms, with or without 612855Sgabeblack@google.com * modification, are permitted provided that the following conditions are 712855Sgabeblack@google.com * met: redistributions of source code must retain the above copyright 812855Sgabeblack@google.com * notice, this list of conditions and the following disclaimer; 912855Sgabeblack@google.com * redistributions in binary form must reproduce the above copyright 1012855Sgabeblack@google.com * notice, this list of conditions and the following disclaimer in the 1112855Sgabeblack@google.com * documentation and/or other materials provided with the distribution; 1212855Sgabeblack@google.com * neither the name of the copyright holders nor the names of its 1312855Sgabeblack@google.com * contributors may be used to endorse or promote products derived from 1412855Sgabeblack@google.com * this software without specific prior written permission. 1512855Sgabeblack@google.com * 1612855Sgabeblack@google.com * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 1712855Sgabeblack@google.com * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 1812855Sgabeblack@google.com * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 1912855Sgabeblack@google.com * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 2012855Sgabeblack@google.com * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 2112855Sgabeblack@google.com * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 2212855Sgabeblack@google.com * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2312855Sgabeblack@google.com * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2412855Sgabeblack@google.com * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 2512855Sgabeblack@google.com * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 2612855Sgabeblack@google.com * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 2712855Sgabeblack@google.com * 2812855Sgabeblack@google.com * Authors: Kevin Lim 2912855Sgabeblack@google.com */ 3012855Sgabeblack@google.com 3112855Sgabeblack@google.com#include "base/intmath.hh" 3212855Sgabeblack@google.com#include "base/trace.hh" 3312855Sgabeblack@google.com#include "cpu/pred/btb.hh" 3412855Sgabeblack@google.com 3512855Sgabeblack@google.comDefaultBTB::DefaultBTB(unsigned _numEntries, 3612855Sgabeblack@google.com unsigned _tagBits, 3712855Sgabeblack@google.com unsigned _instShiftAmt) 3812855Sgabeblack@google.com : numEntries(_numEntries), 3912855Sgabeblack@google.com tagBits(_tagBits), 4012855Sgabeblack@google.com instShiftAmt(_instShiftAmt) 4112855Sgabeblack@google.com{ 4212855Sgabeblack@google.com DPRINTF(Fetch, "BTB: Creating BTB object.\n"); 4312855Sgabeblack@google.com 4412855Sgabeblack@google.com if (!isPowerOf2(numEntries)) { 4512855Sgabeblack@google.com fatal("BTB entries is not a power of 2!"); 4612855Sgabeblack@google.com } 4712855Sgabeblack@google.com 4812855Sgabeblack@google.com btb.resize(numEntries); 4912855Sgabeblack@google.com 5012855Sgabeblack@google.com for (int i = 0; i < numEntries; ++i) { 5112855Sgabeblack@google.com btb[i].valid = false; 5212855Sgabeblack@google.com } 5312855Sgabeblack@google.com 5412855Sgabeblack@google.com idxMask = numEntries - 1; 5512855Sgabeblack@google.com 5612855Sgabeblack@google.com tagMask = (1 << tagBits) - 1; 5712855Sgabeblack@google.com 5812855Sgabeblack@google.com tagShiftAmt = instShiftAmt + floorLog2(numEntries); 5912855Sgabeblack@google.com} 6012855Sgabeblack@google.com 6112855Sgabeblack@google.comvoid 6212855Sgabeblack@google.comDefaultBTB::reset() 6312855Sgabeblack@google.com{ 6412855Sgabeblack@google.com for (int i = 0; i < numEntries; ++i) { 65 btb[i].valid = false; 66 } 67} 68 69inline 70unsigned 71DefaultBTB::getIndex(const Addr &inst_PC) 72{ 73 // Need to shift PC over by the word offset. 74 return (inst_PC >> instShiftAmt) & idxMask; 75} 76 77inline 78Addr 79DefaultBTB::getTag(const Addr &inst_PC) 80{ 81 return (inst_PC >> tagShiftAmt) & tagMask; 82} 83 84bool 85DefaultBTB::valid(const Addr &inst_PC, ThreadID tid) 86{ 87 unsigned btb_idx = getIndex(inst_PC); 88 89 Addr inst_tag = getTag(inst_PC); 90 91 assert(btb_idx < numEntries); 92 93 if (btb[btb_idx].valid 94 && inst_tag == btb[btb_idx].tag 95 && btb[btb_idx].tid == tid) { 96 return true; 97 } else { 98 return false; 99 } 100} 101 102// @todo Create some sort of return struct that has both whether or not the 103// address is valid, and also the address. For now will just use addr = 0 to 104// represent invalid entry. 105Addr 106DefaultBTB::lookup(const Addr &inst_PC, ThreadID tid) 107{ 108 unsigned btb_idx = getIndex(inst_PC); 109 110 Addr inst_tag = getTag(inst_PC); 111 112 assert(btb_idx < numEntries); 113 114 if (btb[btb_idx].valid 115 && inst_tag == btb[btb_idx].tag 116 && btb[btb_idx].tid == tid) { 117 return btb[btb_idx].target; 118 } else { 119 return 0; 120 } 121} 122 123void 124DefaultBTB::update(const Addr &inst_PC, const Addr &target, ThreadID tid) 125{ 126 unsigned btb_idx = getIndex(inst_PC); 127 128 assert(btb_idx < numEntries); 129 130 btb[btb_idx].tid = tid; 131 btb[btb_idx].valid = true; 132 btb[btb_idx].target = target; 133 btb[btb_idx].tag = getTag(inst_PC); 134} 135