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31 #include "base/intmath.hh"
32 #include "base/trace.hh"
33 #include "cpu/pred/btb.hh"
35 DefaultBTB::DefaultBTB(unsigned _numEntries
,
37 unsigned _instShiftAmt
)
38 : numEntries(_numEntries
),
40 instShiftAmt(_instShiftAmt
)
42 DPRINTF(Fetch
, "BTB: Creating BTB object.\n");
44 if (!isPowerOf2(numEntries
)) {
45 fatal("BTB entries is not a power of 2!");
48 btb
.resize(numEntries
);
50 for (int i
= 0; i
< numEntries
; ++i
) {
54 idxMask
= numEntries
- 1;
56 tagMask
= (1 << tagBits
) - 1;
58 tagShiftAmt
= instShiftAmt
+ floorLog2(numEntries
);
64 for (int i
= 0; i
< numEntries
; ++i
) {
71 DefaultBTB::getIndex(const Addr
&inst_PC
)
73 // Need to shift PC over by the word offset.
74 return (inst_PC
>> instShiftAmt
) & idxMask
;
79 DefaultBTB::getTag(const Addr
&inst_PC
)
81 return (inst_PC
>> tagShiftAmt
) & tagMask
;
85 DefaultBTB::valid(const Addr
&inst_PC
, ThreadID tid
)
87 unsigned btb_idx
= getIndex(inst_PC
);
89 Addr inst_tag
= getTag(inst_PC
);
91 assert(btb_idx
< numEntries
);
93 if (btb
[btb_idx
].valid
94 && inst_tag
== btb
[btb_idx
].tag
95 && btb
[btb_idx
].tid
== tid
) {
102 // @todo Create some sort of return struct that has both whether or not the
103 // address is valid, and also the address. For now will just use addr = 0 to
104 // represent invalid entry.
106 DefaultBTB::lookup(const Addr
&inst_PC
, ThreadID tid
)
108 unsigned btb_idx
= getIndex(inst_PC
);
110 Addr inst_tag
= getTag(inst_PC
);
112 assert(btb_idx
< numEntries
);
114 if (btb
[btb_idx
].valid
115 && inst_tag
== btb
[btb_idx
].tag
116 && btb
[btb_idx
].tid
== tid
) {
117 return btb
[btb_idx
].target
;
124 DefaultBTB::update(const Addr
&inst_PC
, const Addr
&target
, ThreadID tid
)
126 unsigned btb_idx
= getIndex(inst_PC
);
128 assert(btb_idx
< numEntries
);
130 btb
[btb_idx
].tid
= tid
;
131 btb
[btb_idx
].valid
= true;
132 btb
[btb_idx
].target
= target
;
133 btb
[btb_idx
].tag
= getTag(inst_PC
);