Mercurial > pygar
annotate modules/bluespec/Pygar/core/BranchPred.bsv @ 15:a1833d9f6e3d pygar svn.16
[svn r16] Recent
| author | punk |
|---|---|
| date | Tue, 27 Apr 2010 13:11:45 -0400 |
| parents | 74716e9a81cc |
| children |
| rev | line source |
|---|---|
| rlm@8 | 1 import RegFile::*; |
| rlm@8 | 2 import ProcTypes::*; |
| rlm@8 | 3 import FIFO::*; |
| rlm@8 | 4 |
| rlm@8 | 5 typedef Maybe#(Addr) BrPred; |
| rlm@8 | 6 typedef Bit#(4) BPindx; |
| rlm@8 | 7 |
| rlm@8 | 8 typedef struct {Addr brpc; Addr nextpc;} BrPair deriving (Bits,Eq); |
| rlm@8 | 9 |
| rlm@8 | 10 typedef union tagged |
| rlm@8 | 11 { |
| rlm@8 | 12 BrPair Valid; |
| rlm@8 | 13 void Invalid; |
| rlm@8 | 14 } CBranchPath deriving(Bits, Eq); // have the cache start out invalid and add valid values. |
| rlm@8 | 15 |
| rlm@8 | 16 interface BranchPred; |
| rlm@8 | 17 method BrPred get(Addr pres); //returns a maybe type that is invalid if no predition |
| rlm@8 | 18 method Action upd(Addr pres, Addr next); |
| rlm@8 | 19 endinterface |
| rlm@8 | 20 |
| rlm@8 | 21 module mkBranchPred(BranchPred); |
| rlm@8 | 22 |
| rlm@8 | 23 //state variables |
| rlm@8 | 24 RegFile#(BPindx, CBranchPath) bcache <- mkRegFileFull(); // cache to hold 16 (based on BPindx) |
| rlm@8 | 25 |
| rlm@8 | 26 method Action upd(Addr pres, Addr next); |
| rlm@8 | 27 BrPair brp; |
| rlm@8 | 28 brp = BrPair {brpc:pres, nextpc:next}; |
| rlm@8 | 29 bcache.upd(pres[5:2], tagged Valid brp); |
| rlm@8 | 30 endmethod |
| rlm@8 | 31 |
| rlm@8 | 32 method BrPred get(Addr prespc); |
| rlm@8 | 33 BPindx rd = prespc[5:2]; |
| rlm@8 | 34 let cbp = bcache.sub(rd); |
| rlm@8 | 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 |
| rlm@8 | 36 return tagged Valid bp.nextpc; |
| rlm@8 | 37 else return Invalid; |
| rlm@8 | 38 endmethod |
| rlm@8 | 39 |
| rlm@8 | 40 endmodule |
| rlm@8 | 41 |