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-rw-r--r--cpu/o3/btb.cc120
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diff --git a/cpu/o3/btb.cc b/cpu/o3/btb.cc
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-/*
- * 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.
- */
-
-#include "base/intmath.hh"
-#include "base/trace.hh"
-#include "cpu/o3/btb.hh"
-
-using namespace TheISA;
-
-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);
-}
-
-inline
-unsigned
-DefaultBTB::getIndex(const Addr &inst_PC)
-{
- // Need to shift PC over by the word offset.
- return (inst_PC >> instShiftAmt) & idxMask;
-}
-
-inline
-Addr
-DefaultBTB::getTag(const Addr &inst_PC)
-{
- return (inst_PC >> tagShiftAmt) & tagMask;
-}
-
-bool
-DefaultBTB::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.
-Addr
-DefaultBTB::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;
- }
-}
-
-void
-DefaultBTB::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);
-}