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authorNathan Binkert <binkertn@umich.edu>2005-06-04 20:50:10 -0400
committerNathan Binkert <binkertn@umich.edu>2005-06-04 20:50:10 -0400
commit13c005a8af79a8481879ce099b45a1f98faae165 (patch)
tree3125dfe10539270433981b39119dd727295c255c /cpu/o3/bpred_unit_impl.hh
parent5a94e6f2cc6ed8480063da68d20274ced2930925 (diff)
downloadgem5-13c005a8af79a8481879ce099b45a1f98faae165.tar.xz
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
Diffstat (limited to 'cpu/o3/bpred_unit_impl.hh')
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1 files changed, 274 insertions, 0 deletions
diff --git a/cpu/o3/bpred_unit_impl.hh b/cpu/o3/bpred_unit_impl.hh
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+++ b/cpu/o3/bpred_unit_impl.hh
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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/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);
+}