gem5 v24.1.0.1
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tage.hh
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1/*
2 * Copyright (c) 2022-2023 The University of Edinburgh
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2014 The University of Wisconsin
15 *
16 * Copyright (c) 2006 INRIA (Institut National de Recherche en
17 * Informatique et en Automatique / French National Research Institute
18 * for Computer Science and Applied Mathematics)
19 *
20 * All rights reserved.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions are
24 * met: redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer;
26 * redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution;
29 * neither the name of the copyright holders nor the names of its
30 * contributors may be used to endorse or promote products derived from
31 * this software without specific prior written permission.
32 *
33 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
34 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
35 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
36 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
37 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
38 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
39 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
40 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
41 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
42 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
43 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44 */
45
46/* @file
47 * Implementation of a TAGE branch predictor. TAGE is a global-history based
48 * branch predictor. It features a PC-indexed bimodal predictor and N
49 * partially tagged tables, indexed with a hash of the PC and the global
50 * branch history. The different lengths of global branch history used to
51 * index the partially tagged tables grow geometrically. A small path history
52 * is also used in the hash.
53 *
54 * All TAGE tables are accessed in parallel, and the one using the longest
55 * history that matches provides the prediction (some exceptions apply).
56 * Entries are allocated in components using a longer history than the
57 * one that predicted when the prediction is incorrect.
58 */
59
60#ifndef __CPU_PRED_TAGE_HH__
61#define __CPU_PRED_TAGE_HH__
62
63#include <vector>
64
65#include "base/random.hh"
66#include "base/types.hh"
68#include "cpu/pred/tage_base.hh"
69#include "params/TAGE.hh"
70
71namespace gem5
72{
73
74namespace branch_prediction
75{
76
77class TAGE: public BPredUnit
78{
79 protected:
81
83
85 {
87
89 {}
90
92 {
93 delete tageBranchInfo;
94 }
95 };
96
97 virtual bool predict(ThreadID tid, Addr branch_pc, bool cond_branch,
98 void* &b);
99
100 public:
101
102 TAGE(const TAGEParams &params);
103
104 // Base class methods.
105 bool lookup(ThreadID tid, Addr pc, void* &bp_history) override;
106 void updateHistories(ThreadID tid, Addr pc, bool uncond, bool taken,
107 Addr target, void * &bp_history) override;
108 void update(ThreadID tid, Addr pc, bool taken,
109 void * &bp_history, bool squashed,
110 const StaticInstPtr & inst, Addr target) override;
111 virtual void squash(ThreadID tid, void * &bp_history) override;
112};
113
114} // namespace branch_prediction
115} // namespace gem5
116
117#endif // __CPU_PRED_TAGE_HH__
Defines global host-dependent types: Counter, Tick, and (indirectly) {int,uint}{8,...
std::shared_ptr< Random > RandomPtr
Definition random.hh:65
static RandomPtr genRandom()
Definition random.hh:68
Basically a wrapper class to hold both the branch predictor and the BTB.
Definition bpred_unit.hh:71
Random::RandomPtr rng
Definition tage.hh:82
bool lookup(ThreadID tid, Addr pc, void *&bp_history) override
Looks up a given conditional branch PC of in the BP to see if it is taken or not taken.
Definition tage.cc:119
void updateHistories(ThreadID tid, Addr pc, bool uncond, bool taken, Addr target, void *&bp_history) override
Ones done with the prediction this function updates the path and global history.
Definition tage.cc:129
virtual bool predict(ThreadID tid, Addr branch_pc, bool cond_branch, void *&b)
Definition tage.cc:111
virtual void squash(ThreadID tid, void *&bp_history) override
Definition tage.cc:102
void update(ThreadID tid, Addr pc, bool taken, void *&bp_history, bool squashed, const StaticInstPtr &inst, Addr target) override
Updates the BP with taken/not taken information.
Definition tage.cc:71
const Params & params() const
Bitfield< 7 > b
Bitfield< 4 > pc
Copyright (c) 2024 Arm Limited All rights reserved.
Definition binary32.hh:36
int16_t ThreadID
Thread index/ID type.
Definition types.hh:235
uint64_t Addr
Address type This will probably be moved somewhere else in the near future.
Definition types.hh:147
TAGEBase::BranchInfo * tageBranchInfo
Definition tage.hh:86

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