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Updated global history predictor.

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This commit is contained in:
Ross Thompson 2023-02-13 18:07:32 -06:00
parent 9f25b53b36
commit bbc6095260
1 changed files with 15 additions and 10 deletions
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25
src/ifu/bpred/speculativeglobalhistory.sv
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@ -1,5 +1,5 @@
///////////////////////////////////////////
// speculativeglobalhistory.sv
// gsharePredictor.sv
//
// Written: Shreya Sanghai
// Email: ssanghai@hmc.edu
@ -36,8 +36,10 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
output logic [1:0] DirPredictionF,
output logic DirPredictionWrongE,
// update
input logic [3:0] InstrClassD, InstrClassE,
input logic [2:0] PredInstrClassF, WrongPredInstrClassD,
input logic [`XLEN-1:0] PCNextF, PCF, PCD, PCE,
input logic [3:0] PredInstrClassF,
input logic [3:0] InstrClassD, InstrClassE, InstrClassM,
input logic [3:0] WrongPredInstrClassD,
input logic PCSrcE
);
@ -47,9 +49,9 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
logic [1:0] TableDirPredictionF, DirPredictionD, DirPredictionE;
logic [1:0] NewDirPredictionE;
logic [k-1:0] GHRF, GHRD, GHRE;
logic [k-1:0] GHRF, GHRD, GHRE, GHRM;
logic GHRLastF;
logic [k-1:0] GHRNextF, GHRNextD, GHRNextE;
logic [k-1:0] GHRNextF, GHRNextD, GHRNextE, GHRNextM;
logic [k-1:0] IndexNextF, IndexF, IndexD, IndexE;
logic [1:0] ForwardNewDirPrediction, ForwardDirPredictionF;
@ -57,8 +59,8 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
assign IndexNextF = GHRNextF;
assign IndexF = GHRF;
assign IndexD = GHRD[k-1:0];
assign IndexE = GHRE[k-1:0];
assign IndexD = GHRD;
assign IndexE = GHRE;
ram2p1r1wbe #(2**k, 2) PHT(.clk(clk),
.ce1(~StallF | reset), .ce2(~StallM & ~FlushM),
@ -111,15 +113,18 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
// If it is wrong and branch does exist then shift right and insert the prediction.
// If the branch does not exist then shift left and use GHRLastF to restore the LSB.
logic [k-1:0] GHRClassWrong;
mux2 #(k) GHRClassWrongMux({DirPredictionD[1], GHRF[k-1:1]}, {GHRF[k-2:0], GHRLastF}, InstrClassD[0], GHRClassWrong);
mux2 #(k) GHRClassWrongMux({DirPredictionD[1], GHRF[k-1:1]}, {GHRF[k-2:0], GHRLastF}, ~InstrClassD[0], GHRClassWrong);
// As with GHRF FlushD and wrong direction prediction flushes the pipeline and restores to GHRNextE.
mux3 #(k) GHRDMux(GHRF, GHRClassWrong, GHRNextE, {FlushDOrDirWrong, WrongPredInstrClassD[0]}, GHRNextD);
flopenr #(k) GHRDReg(clk, reset, ~StallD | FlushDOrDirWrong, GHRNextD, GHRD);
mux3 #(k) GHREMux(GHRD, GHRE, {PCSrcE, GHRD[k-2:0]}, {InstrClassE[0] & ~FlushM, FlushE}, GHRNextE);
mux3 #(k) GHREMux(GHRD, GHRNextM, {PCSrcE, GHRD[k-2:0]}, {InstrClassE[0] & ~FlushM, FlushE}, GHRNextE);
flopenr #(k) GHREReg(clk, reset, ((InstrClassE[0] & ~FlushM) & ~StallE) | FlushE, GHRNextE, GHRE);
flopenr #(k) GHREReg(clk, reset, (~StallE) | FlushE, GHRNextE, GHRE);
assign GHRNextM = FlushM ? GHRM : GHRE;
flopenr #(k) GHRMReg(clk, reset, (InstrClassM[0] & ~StallM) | FlushM, GHRNextM, GHRM);
assign DirPredictionWrongE = PCSrcE != DirPredictionE[1] & InstrClassE[0];