edf9092fee
- A new abstract BTB class is created to enable different BTB implementations. The new BTB class gets its own parameter and stats. - An enum is added to differentiate branch instruction types. This enum is used to enhance statistics and BPU management. - The existing BTB is moved into `simple_btb` as default. - An additional function is added to store the static instruction in the BTB. This function is used for the decoupled front-end. - Update configs to match new BTB parameters. Change-Id: I99b29a19a1b57e59ea2b188ed7d62a8b79426529 Signed-off-by: David Schall <david.schall@ed.ac.uk>
131 lines
4.9 KiB
C++
131 lines
4.9 KiB
C++
/*
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* Copyright (c) 2022-2023 The University of Edinburgh
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* All rights reserved
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Copyright (c) 2004-2005 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __CPU_PRED_BTB_HH__
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#define __CPU_PRED_BTB_HH__
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#include "arch/generic/pcstate.hh"
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#include "base/statistics.hh"
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#include "cpu/pred/branch_type.hh"
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#include "cpu/static_inst.hh"
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#include "params/BranchTargetBuffer.hh"
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#include "sim/clocked_object.hh"
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namespace gem5
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{
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namespace branch_prediction
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{
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class BranchTargetBuffer : public ClockedObject
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{
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public:
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typedef BranchTargetBufferParams Params;
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typedef enums::BranchType BranchType;
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BranchTargetBuffer(const Params ¶ms);
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virtual void memInvalidate() override = 0;
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/** Checks if a branch address is in the BTB. Intended as a quick check
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* before calling lookup. Does not update statistics.
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* @param inst_PC The address of the branch to look up.
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* @return Whether or not the branch exists in the BTB.
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*/
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virtual bool valid(ThreadID tid, Addr instPC) = 0;
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/** Looks up an address in the BTB to get the target of the branch.
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* @param inst_PC The address of the branch to look up.
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* @param type Optional type of the branch to look up.
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* @return The target of the branch or nullptr if the branch is not
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* in the BTB.
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*/
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virtual const PCStateBase *lookup(ThreadID tid, Addr instPC,
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BranchType type = BranchType::NoBranch) = 0;
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/** Looks up an address in the BTB and return the instruction
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* information if existant. Does not update statistics.
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* @param inst_PC The address of the branch to look up.
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* @return Returns the target of the branch.
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*/
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virtual const StaticInstPtr getInst(ThreadID tid, Addr instPC) = 0;
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/** Updates the BTB with the target of a branch.
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* @param inst_pc The address of the branch being updated.
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* @param target_pc The target address of the branch.
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*/
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virtual void update(ThreadID tid, Addr inst_pc,
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const PCStateBase &target_pc,
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BranchType type = BranchType::NoBranch,
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StaticInstPtr inst = nullptr) = 0;
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/** Update BTB statistics
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*/
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virtual void incorrectTarget(Addr inst_pc,
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BranchType type = BranchType::NoBranch)
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{
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stats.mispredict[type]++;
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}
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protected:
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/** Number of the threads for which the branch history is maintained. */
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const unsigned numThreads;
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struct BranchTargetBufferStats : public statistics::Group
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{
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BranchTargetBufferStats(statistics::Group *parent);
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statistics::Vector lookups;
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statistics::Vector misses;
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statistics::Vector updates;
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statistics::Vector mispredict;
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statistics::Scalar evictions;
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} stats;
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};
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} // namespace branch_prediction
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} // namespace gem5
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#endif // __CPU_PRED_BTB_HH__
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