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29 #include "base/intmath.hh"
30 #include "base/trace.hh"
31 #include "cpu/o3/btb.hh"
33 using namespace TheISA
;
35 DefaultBTB::DefaultBTB(unsigned _numEntries
,
37 unsigned _instShiftAmt
)
38 : numEntries(_numEntries
),
40 instShiftAmt(_instShiftAmt
)
42 // @todo Check to make sure num_entries is valid (a power of 2)
44 DPRINTF(Fetch
, "BTB: Creating BTB object.\n");
46 btb
= new BTBEntry
[numEntries
];
48 for (int i
= 0; i
< numEntries
; ++i
)
53 idxMask
= numEntries
- 1;
55 tagMask
= (1 << tagBits
) - 1;
57 tagShiftAmt
= instShiftAmt
+ floorLog2(numEntries
);
62 DefaultBTB::getIndex(const Addr
&inst_PC
)
64 // Need to shift PC over by the word offset.
65 return (inst_PC
>> instShiftAmt
) & idxMask
;
70 DefaultBTB::getTag(const Addr
&inst_PC
)
72 return (inst_PC
>> tagShiftAmt
) & tagMask
;
76 DefaultBTB::valid(const Addr
&inst_PC
)
78 unsigned btb_idx
= getIndex(inst_PC
);
80 Addr inst_tag
= getTag(inst_PC
);
82 assert(btb_idx
< numEntries
);
84 if (btb
[btb_idx
].valid
&& inst_tag
== btb
[btb_idx
].tag
) {
91 // @todo Create some sort of return struct that has both whether or not the
92 // address is valid, and also the address. For now will just use addr = 0 to
93 // represent invalid entry.
95 DefaultBTB::lookup(const Addr
&inst_PC
)
97 unsigned btb_idx
= getIndex(inst_PC
);
99 Addr inst_tag
= getTag(inst_PC
);
101 assert(btb_idx
< numEntries
);
103 if (btb
[btb_idx
].valid
&& inst_tag
== btb
[btb_idx
].tag
) {
104 return btb
[btb_idx
].target
;
111 DefaultBTB::update(const Addr
&inst_PC
, const Addr
&target
)
113 unsigned btb_idx
= getIndex(inst_PC
);
115 assert(btb_idx
< numEntries
);
117 btb
[btb_idx
].valid
= true;
118 btb
[btb_idx
].target
= target
;
119 btb
[btb_idx
].tag
= getTag(inst_PC
);