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
129
130
131
|
/*
* Copyright (c) 2011 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/types.hh"
#include "cpu/pred/bpred_unit.hh"
#include "cpu/pred/sat_counter.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 Params *params);
virtual void uncondBranch(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(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(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(Addr branch_addr, bool taken, void *bp_history, bool squashed);
void squash(void *bp_history)
{ assert(bp_history == NULL); }
void reset();
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);
/** Array of counters that make up the local predictor. */
std::vector<SatCounter> localCtrs;
/** Size of the local predictor. */
unsigned localPredictorSize;
/** Number of sets. */
unsigned localPredictorSets;
/** Number of bits of the local predictor's counters. */
unsigned localCtrBits;
/** Number of bits to shift the PC when calculating index. */
unsigned instShiftAmt;
/** Mask to get index bits. */
unsigned indexMask;
};
#endif // __CPU_PRED_2BIT_LOCAL_PRED_HH__
|
