1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
/*
* Copyright (c) 2011, 2014 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Copyright (c) 2004-2006 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.
*
* Authors: Kevin Lim
* Timothy M. Jones
*/
#ifndef __CPU_PRED_2BIT_LOCAL_PRED_HH__
#define __CPU_PRED_2BIT_LOCAL_PRED_HH__
#include <vector>
#include "base/sat_counter.hh"
#include "base/types.hh"
#include "cpu/pred/bpred_unit.hh"
#include "params/LocalBP.hh"
/**
* Implements a local predictor that uses the PC to index into a table of
* counters. Note that any time a pointer to the bp_history is given, it
* should be NULL using this predictor because it does not have any branch
* predictor state that needs to be recorded or updated; the update can be
* determined solely by the branch being taken or not taken.
*/
class LocalBP : public BPredUnit
{
public:
/**
* Default branch predictor constructor.
*/
LocalBP(const LocalBPParams *params);
virtual void uncondBranch(ThreadID tid, Addr pc, void * &bp_history);
/**
* Looks up the given address in the branch predictor and returns
* a true/false value as to whether it is taken.
* @param branch_addr The address of the branch to look up.
* @param bp_history Pointer to any bp history state.
* @return Whether or not the branch is taken.
*/
bool lookup(ThreadID tid, Addr branch_addr, void * &bp_history);
/**
* Updates the branch predictor to Not Taken if a BTB entry is
* invalid or not found.
* @param branch_addr The address of the branch to look up.
* @param bp_history Pointer to any bp history state.
* @return Whether or not the branch is taken.
*/
void btbUpdate(ThreadID tid, Addr branch_addr, void * &bp_history);
/**
* Updates the branch predictor with the actual result of a branch.
* @param branch_addr The address of the branch to update.
* @param taken Whether or not the branch was taken.
*/
void update(ThreadID tid, Addr branch_addr, bool taken, void *bp_history,
bool squashed, const StaticInstPtr & inst, Addr corrTarget);
void squash(ThreadID tid, void *bp_history)
{ assert(bp_history == NULL); }
private:
/**
* Returns the taken/not taken prediction given the value of the
* counter.
* @param count The value of the counter.
* @return The prediction based on the counter value.
*/
inline bool getPrediction(uint8_t &count);
/** Calculates the local index based on the PC. */
inline unsigned getLocalIndex(Addr &PC);
/** Size of the local predictor. */
const unsigned localPredictorSize;
/** Number of bits of the local predictor's counters. */
const unsigned localCtrBits;
/** Number of sets. */
const unsigned localPredictorSets;
/** Array of counters that make up the local predictor. */
std::vector<SatCounter> localCtrs;
/** Mask to get index bits. */
const unsigned indexMask;
};
#endif // __CPU_PRED_2BIT_LOCAL_PRED_HH__
|
