Mercurial > pygar
annotate core/src/BranchPred.bsv @ 3:5e0595db14f6 pygar svn.4
[svn r4] added bluespec manual to documents
| author | rlm |
|---|---|
| date | Tue, 20 Apr 2010 20:09:46 -0400 |
| parents | 91a1f76ddd62 |
| children |
| rev | line source |
|---|---|
| punk@1 | 1 import RegFile::*; |
| punk@1 | 2 import ProcTypes::*; |
| punk@1 | 3 import FIFO::*; |
| punk@1 | 4 |
| punk@1 | 5 typedef Maybe#(Addr) BrPred; |
| punk@1 | 6 typedef Bit#(4) BPindx; |
| punk@1 | 7 |
| punk@1 | 8 typedef struct {Addr brpc; Addr nextpc;} BrPair deriving (Bits,Eq); |
| punk@1 | 9 |
| punk@1 | 10 typedef union tagged |
| punk@1 | 11 { |
| punk@1 | 12 BrPair Valid; |
| punk@1 | 13 void Invalid; |
| punk@1 | 14 } CBranchPath deriving(Bits, Eq); // have the cache start out invalid and add valid values. |
| punk@1 | 15 |
| punk@1 | 16 interface BranchPred; |
| punk@1 | 17 method BrPred get(Addr pres); //returns a maybe type that is invalid if no predition |
| punk@1 | 18 method Action upd(Addr pres, Addr next); |
| punk@1 | 19 endinterface |
| punk@1 | 20 |
| punk@1 | 21 module mkBranchPred(BranchPred); |
| punk@1 | 22 |
| punk@1 | 23 //state variables |
| punk@1 | 24 RegFile#(BPindx, CBranchPath) bcache <- mkRegFileFull(); // cache to hold 16 (based on BPindx) |
| punk@1 | 25 |
| punk@1 | 26 method Action upd(Addr pres, Addr next); |
| punk@1 | 27 BrPair brp; |
| punk@1 | 28 brp = BrPair {brpc:pres, nextpc:next}; |
| punk@1 | 29 bcache.upd(pres[5:2], tagged Valid brp); |
| punk@1 | 30 endmethod |
| punk@1 | 31 |
| punk@1 | 32 method BrPred get(Addr prespc); |
| punk@1 | 33 BPindx rd = prespc[5:2]; |
| punk@1 | 34 let cbp = bcache.sub(rd); |
| punk@1 | 35 if (cbp matches tagged Valid .bp &&& bp.brpc == prespc) //make sure that the read value was actually put there and the full address matches |
| punk@1 | 36 return tagged Valid bp.nextpc; |
| punk@1 | 37 else return Invalid; |
| punk@1 | 38 endmethod |
| punk@1 | 39 |
| punk@1 | 40 endmodule |
| punk@1 | 41 |