gem5/cpu/o3/bpred_unit_impl.hh
Nathan Binkert 13c005a8af shuffle files around for new directory structure
--HG--
rename : cpu/base_cpu.cc => cpu/base.cc
rename : cpu/base_cpu.hh => cpu/base.hh
rename : cpu/beta_cpu/2bit_local_pred.cc => cpu/o3/2bit_local_pred.cc
rename : cpu/beta_cpu/2bit_local_pred.hh => cpu/o3/2bit_local_pred.hh
rename : cpu/beta_cpu/alpha_full_cpu.cc => cpu/o3/alpha_cpu.cc
rename : cpu/beta_cpu/alpha_full_cpu.hh => cpu/o3/alpha_cpu.hh
rename : cpu/beta_cpu/alpha_full_cpu_builder.cc => cpu/o3/alpha_cpu_builder.cc
rename : cpu/beta_cpu/alpha_full_cpu_impl.hh => cpu/o3/alpha_cpu_impl.hh
rename : cpu/beta_cpu/alpha_dyn_inst.cc => cpu/o3/alpha_dyn_inst.cc
rename : cpu/beta_cpu/alpha_dyn_inst.hh => cpu/o3/alpha_dyn_inst.hh
rename : cpu/beta_cpu/alpha_dyn_inst_impl.hh => cpu/o3/alpha_dyn_inst_impl.hh
rename : cpu/beta_cpu/alpha_impl.hh => cpu/o3/alpha_impl.hh
rename : cpu/beta_cpu/alpha_params.hh => cpu/o3/alpha_params.hh
rename : cpu/beta_cpu/bpred_unit.cc => cpu/o3/bpred_unit.cc
rename : cpu/beta_cpu/bpred_unit.hh => cpu/o3/bpred_unit.hh
rename : cpu/beta_cpu/bpred_unit_impl.hh => cpu/o3/bpred_unit_impl.hh
rename : cpu/beta_cpu/btb.cc => cpu/o3/btb.cc
rename : cpu/beta_cpu/btb.hh => cpu/o3/btb.hh
rename : cpu/beta_cpu/comm.hh => cpu/o3/comm.hh
rename : cpu/beta_cpu/commit.cc => cpu/o3/commit.cc
rename : cpu/beta_cpu/commit.hh => cpu/o3/commit.hh
rename : cpu/beta_cpu/commit_impl.hh => cpu/o3/commit_impl.hh
rename : cpu/beta_cpu/full_cpu.cc => cpu/o3/cpu.cc
rename : cpu/beta_cpu/full_cpu.hh => cpu/o3/cpu.hh
rename : cpu/beta_cpu/cpu_policy.hh => cpu/o3/cpu_policy.hh
rename : cpu/beta_cpu/decode.cc => cpu/o3/decode.cc
rename : cpu/beta_cpu/decode.hh => cpu/o3/decode.hh
rename : cpu/beta_cpu/decode_impl.hh => cpu/o3/decode_impl.hh
rename : cpu/beta_cpu/fetch.cc => cpu/o3/fetch.cc
rename : cpu/beta_cpu/fetch.hh => cpu/o3/fetch.hh
rename : cpu/beta_cpu/fetch_impl.hh => cpu/o3/fetch_impl.hh
rename : cpu/beta_cpu/free_list.cc => cpu/o3/free_list.cc
rename : cpu/beta_cpu/free_list.hh => cpu/o3/free_list.hh
rename : cpu/beta_cpu/iew.cc => cpu/o3/iew.cc
rename : cpu/beta_cpu/iew.hh => cpu/o3/iew.hh
rename : cpu/beta_cpu/iew_impl.hh => cpu/o3/iew_impl.hh
rename : cpu/beta_cpu/inst_queue.cc => cpu/o3/inst_queue.cc
rename : cpu/beta_cpu/inst_queue.hh => cpu/o3/inst_queue.hh
rename : cpu/beta_cpu/inst_queue_impl.hh => cpu/o3/inst_queue_impl.hh
rename : cpu/beta_cpu/mem_dep_unit.cc => cpu/o3/mem_dep_unit.cc
rename : cpu/beta_cpu/mem_dep_unit.hh => cpu/o3/mem_dep_unit.hh
rename : cpu/beta_cpu/mem_dep_unit_impl.hh => cpu/o3/mem_dep_unit_impl.hh
rename : cpu/beta_cpu/ras.cc => cpu/o3/ras.cc
rename : cpu/beta_cpu/ras.hh => cpu/o3/ras.hh
rename : cpu/beta_cpu/regfile.hh => cpu/o3/regfile.hh
rename : cpu/beta_cpu/rename.cc => cpu/o3/rename.cc
rename : cpu/beta_cpu/rename.hh => cpu/o3/rename.hh
rename : cpu/beta_cpu/rename_impl.hh => cpu/o3/rename_impl.hh
rename : cpu/beta_cpu/rename_map.cc => cpu/o3/rename_map.cc
rename : cpu/beta_cpu/rename_map.hh => cpu/o3/rename_map.hh
rename : cpu/beta_cpu/rob.cc => cpu/o3/rob.cc
rename : cpu/beta_cpu/rob.hh => cpu/o3/rob.hh
rename : cpu/beta_cpu/rob_impl.hh => cpu/o3/rob_impl.hh
rename : cpu/beta_cpu/sat_counter.cc => cpu/o3/sat_counter.cc
rename : cpu/beta_cpu/sat_counter.hh => cpu/o3/sat_counter.hh
rename : cpu/beta_cpu/store_set.cc => cpu/o3/store_set.cc
rename : cpu/beta_cpu/store_set.hh => cpu/o3/store_set.hh
rename : cpu/beta_cpu/tournament_pred.cc => cpu/o3/tournament_pred.cc
rename : cpu/beta_cpu/tournament_pred.hh => cpu/o3/tournament_pred.hh
rename : cpu/ooo_cpu/ooo_cpu.cc => cpu/ozone/cpu.cc
rename : cpu/ooo_cpu/ooo_cpu.hh => cpu/ozone/cpu.hh
rename : cpu/ooo_cpu/ooo_impl.hh => cpu/ozone/cpu_impl.hh
rename : cpu/ooo_cpu/ea_list.cc => cpu/ozone/ea_list.cc
rename : cpu/ooo_cpu/ea_list.hh => cpu/ozone/ea_list.hh
rename : cpu/simple_cpu/simple_cpu.cc => cpu/simple/cpu.cc
rename : cpu/simple_cpu/simple_cpu.hh => cpu/simple/cpu.hh
rename : cpu/full_cpu/smt.hh => cpu/smt.hh
rename : cpu/full_cpu/op_class.hh => encumbered/cpu/full/op_class.hh
extra : convert_revision : c4a891d8d6d3e0e9e5ea56be47d851da44d8c032
2005-06-04 20:50:10 -04:00

274 lines
8.4 KiB
C++

/*
* 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/trace.hh"
#include "base/traceflags.hh"
#include "cpu/o3/bpred_unit.hh"
template<class Impl>
TwobitBPredUnit<Impl>::TwobitBPredUnit(Params &params)
: BP(params.local_predictor_size,
params.local_ctr_bits,
params.instShiftAmt),
BTB(params.BTBEntries,
params.BTBTagSize,
params.instShiftAmt),
RAS(params.RASSize)
{
}
template <class Impl>
void
TwobitBPredUnit<Impl>::regStats()
{
lookups
.name(name() + ".BPredUnit.lookups")
.desc("Number of BP lookups")
;
condPredicted
.name(name() + ".BPredUnit.condPredicted")
.desc("Number of conditional branches predicted")
;
condIncorrect
.name(name() + ".BPredUnit.condIncorrect")
.desc("Number of conditional branches incorrect")
;
BTBLookups
.name(name() + ".BPredUnit.BTBLookups")
.desc("Number of BTB lookups")
;
BTBHits
.name(name() + ".BPredUnit.BTBHits")
.desc("Number of BTB hits")
;
BTBCorrect
.name(name() + ".BPredUnit.BTBCorrect")
.desc("Number of correct BTB predictions (this stat may not "
"work properly.")
;
usedRAS
.name(name() + ".BPredUnit.usedRAS")
.desc("Number of times the RAS was used.")
;
RASIncorrect
.name(name() + ".BPredUnit.RASInCorrect")
.desc("Number of incorrect RAS predictions.")
;
}
template <class Impl>
bool
TwobitBPredUnit<Impl>::predict(DynInstPtr &inst, Addr &PC)
{
// See if branch predictor predicts taken.
// If so, get its target addr either from the BTB or the RAS.
// Once that's done, speculatively update the predictor?
// Save off record of branch stuff so the RAS can be fixed
// up once it's done.
bool pred_taken = false;
Addr target;
++lookups;
if (inst->isUncondCtrl()) {
DPRINTF(Fetch, "BranchPred: Unconditional control.\n");
pred_taken = true;
} else {
++condPredicted;
pred_taken = BPLookup(PC);
DPRINTF(Fetch, "BranchPred: Branch predictor predicted %i for PC %#x"
"\n", pred_taken, inst->readPC());
}
PredictorHistory predict_record(inst->seqNum, PC, pred_taken);
// Now lookup in the BTB or RAS.
if (pred_taken) {
if (inst->isReturn()) {
++usedRAS;
// If it's a function return call, then look up the address
// in the RAS.
target = RAS.top();
// Record the top entry of the RAS, and its index.
predict_record.usedRAS = true;
predict_record.RASIndex = RAS.topIdx();
predict_record.RASTarget = target;
RAS.pop();
DPRINTF(Fetch, "BranchPred: Instruction %#x is a return, RAS "
"predicted target: %#x, RAS index: %i.\n",
inst->readPC(), target, predict_record.RASIndex);
} else {
++BTBLookups;
if (inst->isCall()) {
RAS.push(PC+sizeof(MachInst));
// Record that it was a call so that the top RAS entry can
// be popped off if the speculation is incorrect.
predict_record.wasCall = true;
DPRINTF(Fetch, "BranchPred: Instruction %#x was a call, "
"adding %#x to the RAS.\n",
inst->readPC(), PC+sizeof(MachInst));
}
if (BTB.valid(PC)) {
++BTBHits;
//If it's anything else, use the BTB to get the target addr.
target = BTB.lookup(PC);
DPRINTF(Fetch, "BranchPred: Instruction %#x predicted target "
"is %#x.\n", inst->readPC(), target);
} else {
DPRINTF(Fetch, "BranchPred: BTB doesn't have a valid entry."
"\n");
pred_taken = false;
}
}
}
if (pred_taken) {
// Set the PC and the instruction's predicted target.
PC = target;
inst->setPredTarg(target);
} else {
PC = PC + sizeof(MachInst);
inst->setPredTarg(PC);
}
predHist.push_front(predict_record);
assert(!predHist.empty());
return pred_taken;
}
template <class Impl>
void
TwobitBPredUnit<Impl>::update(const InstSeqNum &done_sn)
{
DPRINTF(Fetch, "BranchPred: Commiting branches until sequence number "
"%i.\n", done_sn);
while (!predHist.empty() && predHist.back().seqNum <= done_sn) {
assert(!predHist.empty());
// Update the branch predictor with the correct results of branches.
BP.update(predHist.back().PC, predHist.back().predTaken);
predHist.pop_back();
}
}
template <class Impl>
void
TwobitBPredUnit<Impl>::squash(const InstSeqNum &squashed_sn)
{
while (!predHist.empty() && predHist.front().seqNum > squashed_sn) {
if (predHist.front().usedRAS) {
DPRINTF(Fetch, "BranchPred: Restoring top of RAS to: %i, "
"target: %#x.\n",
predHist.front().RASIndex,
predHist.front().RASTarget);
RAS.restore(predHist.front().RASIndex,
predHist.front().RASTarget);
} else if (predHist.front().wasCall) {
DPRINTF(Fetch, "BranchPred: Removing speculative entry added "
"to the RAS.\n");
RAS.pop();
}
predHist.pop_front();
}
}
template <class Impl>
void
TwobitBPredUnit<Impl>::squash(const InstSeqNum &squashed_sn,
const Addr &corr_target,
const bool actually_taken)
{
// Now that we know that a branch was mispredicted, we need to undo
// all the branches that have been seen up until this branch and
// fix up everything.
++condIncorrect;
DPRINTF(Fetch, "BranchPred: Squashing from sequence number %i, "
"setting target to %#x.\n",
squashed_sn, corr_target);
while (!predHist.empty() && predHist.front().seqNum > squashed_sn) {
if (predHist.front().usedRAS) {
DPRINTF(Fetch, "BranchPred: Restoring top of RAS to: %i, "
"target: %#x.\n",
predHist.front().RASIndex,
predHist.front().RASTarget);
RAS.restore(predHist.front().RASIndex,
predHist.front().RASTarget);
} else if (predHist.front().wasCall) {
DPRINTF(Fetch, "BranchPred: Removing speculative entry added "
"to the RAS.\n");
RAS.pop();
}
predHist.pop_front();
}
predHist.front().predTaken = actually_taken;
if (predHist.front().usedRAS) {
++RASIncorrect;
}
BP.update(predHist.front().PC, actually_taken);
BTB.update(predHist.front().PC, corr_target);
}