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Updated global history branch predictcor with the gshare improvements.

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This commit is contained in:
Ross Thompson 2023-01-29 16:26:44 -06:00
parent a9a7054e2f
commit 392716a608
2 changed files with 42 additions and 40 deletions
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21
pipelined/src/ifu/bpred/bpred.sv
View File

@ -85,41 +85,37 @@ module bpred (
logic [3:0] WrongPredInstrClassD;
//************ new resolve issues
logic BTBTargetWrongE;
logic RASTargetWrongE;
logic JumpOrTakenBranchE;
logic [`XLEN-1:0] PredPCD, PredPCE, RASPCD, RASPCE;
// Part 1 branch direction prediction
// look into the 2 port Sram model. something is wrong.
if (`BPRED_TYPE == "BPTWOBIT") begin:Predictor
twoBitPredictor DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
twoBitPredictor #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
.PCNextF, .PCM, .DirPredictionF, .DirPredictionWrongE,
.BranchInstrE(InstrClassE[0]), .BranchInstrM(InstrClassM[0]), .PCSrcE);
end else if (`BPRED_TYPE == "BPGLOBAL") begin:Predictor
globalhistory DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
globalhistory #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
.PCNextF, .PCM, .DirPredictionF, .DirPredictionWrongE,
.BranchInstrE(InstrClassE[0]), .BranchInstrM(InstrClassM[0]), .PCSrcE);
end else if (`BPRED_TYPE == "BPSPECULATIVEGLOBAL") begin:Predictor
speculativeglobalhistory #(10) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.PCNextF, .PCF, .PCD, .PCE, .PCM, .DirPredictionF, .DirPredictionWrongE,
speculativeglobalhistory #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.DirPredictionF, .DirPredictionWrongE,
.BranchInstrF(PredInstrClassF[0]), .BranchInstrD(InstrClassD[0]), .BranchInstrE(InstrClassE[0]), .BranchInstrM(InstrClassM[0]),
.BranchInstrW(InstrClassW[0]), .WrongPredInstrClassD, .PCSrcE);
end else if (`BPRED_TYPE == "BPGSHARE") begin:Predictor
gshare DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
gshare #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .FlushD, .FlushE, .FlushM,
.PCNextF, .PCE, .DirPredictionF, .DirPredictionWrongE,
.BranchInstrE(InstrClassE[0]), .BranchInstrM(InstrClassM[0]), .PCSrcE);
end else if (`BPRED_TYPE == "BPSPECULATIVEGSHARE") begin:Predictor
speculativegshare DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
speculativegshare #(`BPRED_SIZE) DirPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.PCNextF, .PCF, .PCD, .PCE, .PCM, .DirPredictionF, .DirPredictionWrongE,
.BranchInstrF(PredInstrClassF[0]), .BranchInstrD(InstrClassD[0]), .BranchInstrE(InstrClassE[0]), .BranchInstrM(InstrClassM[0]),
.BranchInstrW(InstrClassW[0]), .WrongPredInstrClassD, .PCSrcE);
@ -139,7 +135,6 @@ module bpred (
-----/\----- EXCLUDED -----/\----- */
end
// this predictor will have two pieces of data,
// 1) A direction (1 = Taken, 0 = Not Taken)
// 2) Any information which is necessary for the predictor to build its next state.
@ -260,7 +255,6 @@ module bpred (
// branch class prediction wrong.
assign WrongPredInstrClassD = PredInstrClassD ^ InstrClassD;
// Selects the BP or PC+2/4.
mux2 #(`XLEN) pcmux0(PCPlus2or4F, BPPredPCF, SelBPPredF, PCNext0F);
// If the prediction is wrong select the correct address.
@ -292,8 +286,5 @@ module bpred (
flopenrc #(`XLEN) RASTargetDReg(clk, reset, FlushD, ~StallD, RASPCF, RASPCD);
flopenrc #(`XLEN) RASTargetEReg(clk, reset, FlushE, ~StallE, RASPCD, RASPCE);
endmodule

61
pipelined/src/ifu/bpred/speculativeglobalhistory.sv
View File

@ -1,5 +1,5 @@
///////////////////////////////////////////
// globalHistoryPredictor.sv
// speculativeglobalhistory.sv
//
// Written: Shreya Sanghai
// Email: ssanghai@hmc.edu
@ -28,7 +28,7 @@
`include "wally-config.vh"
module speculativeglobalhistory #(parameter k = 10) (
module speculativeglobalhistory #(parameter int k = 10 ) (
input logic clk,
input logic reset,
input logic StallF, StallD, StallE, StallM, StallW,
@ -36,7 +36,6 @@ module speculativeglobalhistory #(parameter k = 10) (
output logic [1:0] DirPredictionF,
output logic DirPredictionWrongE,
// update
input logic [`XLEN-1:0] PCNextF, PCF, PCD, PCE, PCM,
input logic BranchInstrF, BranchInstrD, BranchInstrE, BranchInstrM, BranchInstrW,
input logic [3:0] WrongPredInstrClassD,
input logic PCSrcE
@ -49,14 +48,14 @@ module speculativeglobalhistory #(parameter k = 10) (
logic [1:0] NewDirPredictionF, NewDirPredictionD, NewDirPredictionE;
logic [k-1:0] GHRF;
logic [k:0] GHRD, OldGHRE, GHRE, GHRM, GHRW;
logic [k-1:0] GHRNextF;
logic [k:-1] GHRNextD, OldGHRD;
logic [k:0] GHRNextE, GHRNextM, GHRNextW;
logic GHRExtraF;
logic [k-1:0] GHRD, GHRE, GHRM, GHRW;
logic [k-1:0] GHRNextF;
logic [k-1:0] GHRNextD;
logic [k-1:0] GHRNextE, GHRNextM, GHRNextW;
logic [k-1:0] IndexNextF, IndexF;
logic [k-1:0] IndexD, IndexE;
logic [`XLEN-1:0] PCW;
logic [1:0] ForwardNewDirPrediction, ForwardDirPredictionF;
@ -102,30 +101,42 @@ module speculativeglobalhistory #(parameter k = 10) (
satCounter2 BPDirUpdateE(.BrDir(PCSrcE), .OldState(DirPredictionE), .NewState(NewDirPredictionE));
// GHR pipeline
assign GHRNextF = FlushD ? GHRNextD[k:1] :
BranchInstrF ? {DirPredictionF[1], GHRF[k-1:1]} :
GHRF;
// this version fails the regression test do to pessimistic x propagation.
// assign GHRNextF = FlushD | DirPredictionWrongE ? GHRNextD[k-1:0] :
// BranchInstrF ? {DirPredictionF[1], GHRF[k-1:1]} :
// GHRF;
flopenr #(k) GHRFReg(clk, reset, (~StallF) | FlushD, GHRNextF, GHRF);
assign GHRNextD = FlushD ? {GHRNextE, GHRNextE[0]} : {DirPredictionF[1], GHRF, GHRF[0]};
flopenr #(k+2) GHRDReg(clk, reset, (~StallD) | FlushD, GHRNextD, OldGHRD);
assign GHRD = WrongPredInstrClassD[0] & BranchInstrD ? {DirPredictionD[1], OldGHRD[k:1]} : // shift right
WrongPredInstrClassD[0] & ~BranchInstrD ? OldGHRD[k-1:-1] : // shift left
OldGHRD[k:0];
always_comb begin
if(FlushD | DirPredictionWrongE) begin
GHRNextF = GHRNextD[k-1:0];
end else if(BranchInstrF) GHRNextF = {DirPredictionF[1], GHRF[k-1:1]};
else GHRNextF = GHRF;
end
assign GHRNextE = FlushE ? GHRNextM : GHRD;
flopenr #(k+1) GHREReg(clk, reset, (~StallE) | FlushE, GHRNextE, OldGHRE);
assign GHRE = BranchInstrE ? {PCSrcE, OldGHRE[k-1:0]} : OldGHRE;
flopenr #(k) GHRFReg(clk, reset, (~StallF) | FlushD, GHRNextF, GHRF);
flopenr #(1) GHRFExtraReg(clk, reset, (~StallF) | FlushD, GHRF[0], GHRExtraF);
// use with out instruction class prediction
//assign GHRNextD = FlushD ? GHRNextE[k-1:0] : GHRF[k-1:0];
// with instruction class prediction
assign GHRNextD = (FlushD | DirPredictionWrongE) ? GHRNextE[k-1:0] :
WrongPredInstrClassD[0] & BranchInstrD ? {DirPredictionD[1], GHRF[k-1:1]} : // shift right
WrongPredInstrClassD[0] & ~BranchInstrD ? {GHRF[k-2:0], GHRExtraF}: // shift left
GHRF[k-1:0];
flopenr #(k) GHRDReg(clk, reset, (~StallD) | FlushD, GHRNextD, GHRD);
assign GHRNextE = BranchInstrE & ~FlushM ? {PCSrcE, GHRD[k-2:0]} : // if the branch is not flushed
FlushE ? GHRNextM : // branch is flushed
GHRD;
flopenr #(k) GHREReg(clk, reset, (~StallE) | FlushE, GHRNextE, GHRE);
assign GHRNextM = FlushM ? GHRNextW : GHRE;
flopenr #(k+1) GHRMReg(clk, reset, (~StallM) | FlushM, GHRNextM, GHRM);
flopenr #(k) GHRMReg(clk, reset, (~StallM) | FlushM, GHRNextM, GHRM);
assign GHRNextW = FlushW ? GHRW : GHRM;
flopenr #(k+1) GHRWReg(clk, reset, (BranchInstrM & ~StallW) | FlushW, GHRNextW, GHRW);
flopenr #(k) GHRWReg(clk, reset, (BranchInstrW & ~StallW) | FlushW, GHRNextW, GHRW);
assign DirPredictionWrongE = PCSrcE != DirPredictionE[1] & BranchInstrE;
flopenr #(`XLEN) PCWReg(clk, reset, ~StallW, PCM, PCW);
endmodule