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Partial fix for gshare bugs from the last two weeks.

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This commit is contained in:
Ross Thompson 2023-02-13 11:57:25 -06:00
parent 58749a8c57
commit 1d74663f42
2 changed files with 10 additions and 7 deletions
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2
src/ifu/bpred/bpred.sv
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@ -118,7 +118,7 @@ module bpred (
end else if (`BPRED_TYPE == "BPSPECULATIVEGSHARE") begin:Predictor
speculativegshare #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.PCNextF, .PCF, .PCD, .PCE, .DirPredictionF, .DirPredictionWrongE,
.PredInstrClassF, .InstrClassD, .InstrClassE, .WrongPredInstrClassD, .PCSrcE);
.PredInstrClassF, .InstrClassD, .InstrClassE, .InstrClassM, .WrongPredInstrClassD, .PCSrcE);
end else if (`BPRED_TYPE == "BPLOCALPAg") begin:Predictor
// *** Fix me

15
src/ifu/bpred/speculativegshare.sv
View File

@ -38,7 +38,7 @@ module speculativegshare #(parameter int k = 10 ) (
// update
input logic [`XLEN-1:0] PCNextF, PCF, PCD, PCE,
input logic [2:0] PredInstrClassF,
input logic [3:0] InstrClassD, InstrClassE,
input logic [3:0] InstrClassD, InstrClassE, InstrClassM,
input logic [2:0] WrongPredInstrClassD,
input logic PCSrcE
);
@ -49,9 +49,9 @@ module speculativegshare #(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;
@ -113,15 +113,18 @@ module speculativegshare #(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];