2bit_local.cc (8842:a02932e2e73d) 2bit_local.cc (9480:d059f8a95a42)
1/*
2 * Copyright (c) 2004-2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;

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29 */
30
31#include "base/intmath.hh"
32#include "base/misc.hh"
33#include "base/trace.hh"
34#include "cpu/pred/2bit_local.hh"
35#include "debug/Fetch.hh"
36
1/*
2 * Copyright (c) 2004-2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;

--- 20 unchanged lines hidden (view full) ---

29 */
30
31#include "base/intmath.hh"
32#include "base/misc.hh"
33#include "base/trace.hh"
34#include "cpu/pred/2bit_local.hh"
35#include "debug/Fetch.hh"
36
37LocalBP::LocalBP(unsigned _localPredictorSize,
38 unsigned _localCtrBits,
39 unsigned _instShiftAmt)
40 : localPredictorSize(_localPredictorSize),
41 localCtrBits(_localCtrBits),
42 instShiftAmt(_instShiftAmt)
37LocalBP::LocalBP(const Params *params)
38 : BPredUnit(params),
39 localPredictorSize(params->localPredictorSize),
40 localCtrBits(params->localCtrBits),
41 instShiftAmt(params->instShiftAmt)
43{
44 if (!isPowerOf2(localPredictorSize)) {
45 fatal("Invalid local predictor size!\n");
46 }
47
48 localPredictorSets = localPredictorSize / localCtrBits;
49
50 if (!isPowerOf2(localPredictorSets)) {
51 fatal("Invalid number of local predictor sets! Check localCtrBits.\n");
52 }
53
54 // Setup the index mask.
55 indexMask = localPredictorSets - 1;
56
42{
43 if (!isPowerOf2(localPredictorSize)) {
44 fatal("Invalid local predictor size!\n");
45 }
46
47 localPredictorSets = localPredictorSize / localCtrBits;
48
49 if (!isPowerOf2(localPredictorSets)) {
50 fatal("Invalid number of local predictor sets! Check localCtrBits.\n");
51 }
52
53 // Setup the index mask.
54 indexMask = localPredictorSets - 1;
55
57 DPRINTF(Fetch, "Branch predictor: index mask: %#x\n", indexMask);
56 DPRINTF(Fetch, "index mask: %#x\n", indexMask);
58
59 // Setup the array of counters for the local predictor.
60 localCtrs.resize(localPredictorSets);
61
62 for (unsigned i = 0; i < localPredictorSets; ++i)
57
58 // Setup the array of counters for the local predictor.
59 localCtrs.resize(localPredictorSets);
60
61 for (unsigned i = 0; i < localPredictorSets; ++i)
63 localCtrs[i].setBits(_localCtrBits);
62 localCtrs[i].setBits(localCtrBits);
64
63
65 DPRINTF(Fetch, "Branch predictor: local predictor size: %i\n",
64 DPRINTF(Fetch, "local predictor size: %i\n",
66 localPredictorSize);
67
65 localPredictorSize);
66
68 DPRINTF(Fetch, "Branch predictor: local counter bits: %i\n", localCtrBits);
67 DPRINTF(Fetch, "local counter bits: %i\n", localCtrBits);
69
68
70 DPRINTF(Fetch, "Branch predictor: instruction shift amount: %i\n",
69 DPRINTF(Fetch, "instruction shift amount: %i\n",
71 instShiftAmt);
72}
73
74void
75LocalBP::reset()
76{
77 for (unsigned i = 0; i < localPredictorSets; ++i) {
78 localCtrs[i].reset();
79 }
80}
81
82void
70 instShiftAmt);
71}
72
73void
74LocalBP::reset()
75{
76 for (unsigned i = 0; i < localPredictorSets; ++i) {
77 localCtrs[i].reset();
78 }
79}
80
81void
83LocalBP::BTBUpdate(Addr &branch_addr, void * &bp_history)
82LocalBP::btbUpdate(Addr branch_addr, void * &bp_history)
84{
85// Place holder for a function that is called to update predictor history when
86// a BTB entry is invalid or not found.
87}
88
89
90bool
83{
84// Place holder for a function that is called to update predictor history when
85// a BTB entry is invalid or not found.
86}
87
88
89bool
91LocalBP::lookup(Addr &branch_addr, void * &bp_history)
90LocalBP::lookup(Addr branch_addr, void * &bp_history)
92{
93 bool taken;
94 uint8_t counter_val;
95 unsigned local_predictor_idx = getLocalIndex(branch_addr);
96
91{
92 bool taken;
93 uint8_t counter_val;
94 unsigned local_predictor_idx = getLocalIndex(branch_addr);
95
97 DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n",
96 DPRINTF(Fetch, "Looking up index %#x\n",
98 local_predictor_idx);
99
100 counter_val = localCtrs[local_predictor_idx].read();
101
97 local_predictor_idx);
98
99 counter_val = localCtrs[local_predictor_idx].read();
100
102 DPRINTF(Fetch, "Branch predictor: prediction is %i.\n",
101 DPRINTF(Fetch, "prediction is %i.\n",
103 (int)counter_val);
104
105 taken = getPrediction(counter_val);
106
107#if 0
108 // Speculative update.
109 if (taken) {
102 (int)counter_val);
103
104 taken = getPrediction(counter_val);
105
106#if 0
107 // Speculative update.
108 if (taken) {
110 DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n");
109 DPRINTF(Fetch, "Branch updated as taken.\n");
111 localCtrs[local_predictor_idx].increment();
112 } else {
110 localCtrs[local_predictor_idx].increment();
111 } else {
113 DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n");
112 DPRINTF(Fetch, "Branch updated as not taken.\n");
114 localCtrs[local_predictor_idx].decrement();
115 }
116#endif
117
118 return taken;
119}
120
121void
113 localCtrs[local_predictor_idx].decrement();
114 }
115#endif
116
117 return taken;
118}
119
120void
122LocalBP::update(Addr &branch_addr, bool taken, void *bp_history)
121LocalBP::update(Addr branch_addr, bool taken, void *bp_history, bool squashed)
123{
124 assert(bp_history == NULL);
125 unsigned local_predictor_idx;
126
127 // Update the local predictor.
128 local_predictor_idx = getLocalIndex(branch_addr);
129
122{
123 assert(bp_history == NULL);
124 unsigned local_predictor_idx;
125
126 // Update the local predictor.
127 local_predictor_idx = getLocalIndex(branch_addr);
128
130 DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n",
131 local_predictor_idx);
129 DPRINTF(Fetch, "Looking up index %#x\n", local_predictor_idx);
132
133 if (taken) {
130
131 if (taken) {
134 DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n");
132 DPRINTF(Fetch, "Branch updated as taken.\n");
135 localCtrs[local_predictor_idx].increment();
136 } else {
133 localCtrs[local_predictor_idx].increment();
134 } else {
137 DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n");
135 DPRINTF(Fetch, "Branch updated as not taken.\n");
138 localCtrs[local_predictor_idx].decrement();
139 }
140}
141
142inline
143bool
144LocalBP::getPrediction(uint8_t &count)
145{
146 // Get the MSB of the count
147 return (count >> (localCtrBits - 1));
148}
149
150inline
151unsigned
152LocalBP::getLocalIndex(Addr &branch_addr)
153{
154 return (branch_addr >> instShiftAmt) & indexMask;
155}
136 localCtrs[local_predictor_idx].decrement();
137 }
138}
139
140inline
141bool
142LocalBP::getPrediction(uint8_t &count)
143{
144 // Get the MSB of the count
145 return (count >> (localCtrBits - 1));
146}
147
148inline
149unsigned
150LocalBP::getLocalIndex(Addr &branch_addr)
151{
152 return (branch_addr >> instShiftAmt) & indexMask;
153}
154
155void
156LocalBP::uncondBranch(void *&bp_history)
157{
158}