9e1c781c58b84031e6b543603c22387d1a72ce1c
2 * Copyright (c) 2004-2006 The Regents of The University of Michigan
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14 * this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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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"
37 LocalBP::LocalBP(const LocalBPParams
*params
)
39 localPredictorSize(params
->localPredictorSize
),
40 localCtrBits(params
->localCtrBits
)
42 if (!isPowerOf2(localPredictorSize
)) {
43 fatal("Invalid local predictor size!\n");
46 localPredictorSets
= localPredictorSize
/ localCtrBits
;
48 if (!isPowerOf2(localPredictorSets
)) {
49 fatal("Invalid number of local predictor sets! Check localCtrBits.\n");
52 // Setup the index mask.
53 indexMask
= localPredictorSets
- 1;
55 DPRINTF(Fetch
, "index mask: %#x\n", indexMask
);
57 // Setup the array of counters for the local predictor.
58 localCtrs
.resize(localPredictorSets
);
60 for (unsigned i
= 0; i
< localPredictorSets
; ++i
)
61 localCtrs
[i
].setBits(localCtrBits
);
63 DPRINTF(Fetch
, "local predictor size: %i\n",
66 DPRINTF(Fetch
, "local counter bits: %i\n", localCtrBits
);
68 DPRINTF(Fetch
, "instruction shift amount: %i\n",
75 for (unsigned i
= 0; i
< localPredictorSets
; ++i
) {
81 LocalBP::btbUpdate(ThreadID tid
, Addr branch_addr
, void * &bp_history
)
83 // Place holder for a function that is called to update predictor history when
84 // a BTB entry is invalid or not found.
89 LocalBP::lookup(ThreadID tid
, Addr branch_addr
, void * &bp_history
)
93 unsigned local_predictor_idx
= getLocalIndex(branch_addr
);
95 DPRINTF(Fetch
, "Looking up index %#x\n",
98 counter_val
= localCtrs
[local_predictor_idx
].read();
100 DPRINTF(Fetch
, "prediction is %i.\n",
103 taken
= getPrediction(counter_val
);
106 // Speculative update.
108 DPRINTF(Fetch
, "Branch updated as taken.\n");
109 localCtrs
[local_predictor_idx
].increment();
111 DPRINTF(Fetch
, "Branch updated as not taken.\n");
112 localCtrs
[local_predictor_idx
].decrement();
120 LocalBP::update(ThreadID tid
, Addr branch_addr
, bool taken
, void *bp_history
,
123 assert(bp_history
== NULL
);
124 unsigned local_predictor_idx
;
126 // Update the local predictor.
127 local_predictor_idx
= getLocalIndex(branch_addr
);
129 DPRINTF(Fetch
, "Looking up index %#x\n", local_predictor_idx
);
132 DPRINTF(Fetch
, "Branch updated as taken.\n");
133 localCtrs
[local_predictor_idx
].increment();
135 DPRINTF(Fetch
, "Branch updated as not taken.\n");
136 localCtrs
[local_predictor_idx
].decrement();
142 LocalBP::getPrediction(uint8_t &count
)
144 // Get the MSB of the count
145 return (count
>> (localCtrBits
- 1));
150 LocalBP::getLocalIndex(Addr
&branch_addr
)
152 return (branch_addr
>> instShiftAmt
) & indexMask
;
156 LocalBP::uncondBranch(ThreadID tid
, Addr pc
, void *&bp_history
)
161 LocalBPParams::create()
163 return new LocalBP(this);