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Renamed PCPredX to BTAX.

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This commit is contained in:
Ross Thompson 2023-02-23 14:33:32 -06:00
parent f0d32a745a
commit ed91fc5ce3
2 changed files with 23 additions and 24 deletions
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15
src/ifu/bpred/bpred.sv
View File

@ -73,7 +73,7 @@ module bpred (
logic [1:0] DirPredictionF;
logic [3:0] BTBPredInstrClassF, PredInstrClassF, PredInstrClassD;
logic [`XLEN-1:0] PredPCF, RASPCF;
logic [`XLEN-1:0] BTAF, RASPCF;
logic PredictionPCWrongE;
logic AnyWrongPredInstrClassD, AnyWrongPredInstrClassE;
logic [3:0] InstrClassD;
@ -90,7 +90,7 @@ module bpred (
logic RASTargetWrongE;
logic JumpOrTakenBranchE;
logic [`XLEN-1:0] PredPCD, PredPCE, RASPCD, RASPCE;
logic [`XLEN-1:0] BTAD, BTAE, RASPCD, RASPCE;
// Part 1 branch direction prediction
// look into the 2 port Sram model. something is wrong.
@ -142,7 +142,7 @@ module bpred (
btb #(`BTB_SIZE)
TargetPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.PCNextF, .PCF, .PCD, .PCE, .PCM,
.PredPCF,
.BTAF, .BTAD,
.BTBPredInstrClassF,
.PredictionInstrClassWrongM,
.IEUAdrE, .IEUAdrM,
@ -189,7 +189,7 @@ module bpred (
.PredInstrClassF, .InstrClassD, .InstrClassE,
.WrongPredInstrClassD, .RASPCF, .PCLinkE);
assign BPPredPCF = PredInstrClassF[2] ? RASPCF : PredPCF;
assign BPPredPCF = PredInstrClassF[2] ? RASPCF : BTAF;
assign InstrClassD[0] = BranchD;
assign InstrClassD[1] = JumpD ;
@ -249,19 +249,18 @@ module bpred (
// 3. target ras (ras target wrong / class[2])
// 4. direction (br dir wrong / class[0])
// Unforuantely we can't relay on PCD to infer the correctness of the BTB or RAS because the class prediction
// Unforuantely we can't use PCD to infer the correctness of the BTB or RAS because the class prediction
// could be wrong or the fall through address selected for branch predict not taken.
// By pipeline the BTB's PC and RAS address through the pipeline we can measure the accuracy of
// both without the above inaccuracies.
assign BTBPredPCWrongE = (PredPCE != IEUAdrE) & (InstrClassE[0] | InstrClassE[1] & ~InstrClassE[2]) & PCSrcE;
assign BTBPredPCWrongE = (BTAE != IEUAdrE) & (InstrClassE[0] | InstrClassE[1] & ~InstrClassE[2]) & PCSrcE;
assign RASPredPCWrongE = (RASPCE != IEUAdrE) & InstrClassE[2] & PCSrcE;
assign JumpOrTakenBranchE = (InstrClassE[0] & PCSrcE) | InstrClassE[1];
flopenrc #(1) JumpOrTakenBranchMReg(clk, reset, FlushM, ~StallM, JumpOrTakenBranchE, JumpOrTakenBranchM);
flopenrc #(`XLEN) BTBTargetDReg(clk, reset, FlushD, ~StallD, PredPCF, PredPCD);
flopenrc #(`XLEN) BTBTargetEReg(clk, reset, FlushE, ~StallE, PredPCD, PredPCE);
flopenrc #(`XLEN) BTBTargetEReg(clk, reset, FlushE, ~StallE, BTAD, BTAE);
flopenrc #(`XLEN) RASTargetDReg(clk, reset, FlushD, ~StallD, RASPCF, RASPCD);
flopenrc #(`XLEN) RASTargetEReg(clk, reset, FlushE, ~StallE, RASPCD, RASPCE);

12
src/ifu/bpred/btb.sv
View File

@ -35,7 +35,8 @@ module btb #(parameter Depth = 10 ) (
input logic reset,
input logic StallF, StallD, StallE, StallM, StallW, FlushD, FlushE, FlushM, FlushW,
input logic [`XLEN-1:0] PCNextF, PCF, PCD, PCE, PCM, // PC at various stages
output logic [`XLEN-1:0] PredPCF, // BTB's guess at PC
output logic [`XLEN-1:0] BTAF, // BTB's guess at PC
output logic [`XLEN-1:0] BTAD,
output logic [3:0] BTBPredInstrClassF, // BTB's guess at instruction class
// update
input logic PredictionInstrClassWrongM, // BTB's instruction class guess was wrong
@ -51,7 +52,6 @@ module btb #(parameter Depth = 10 ) (
logic MatchF, MatchD, MatchE, MatchM, MatchNextX, MatchXF;
logic [`XLEN+3:0] ForwardBTBPrediction, ForwardBTBPredictionF;
logic [`XLEN+3:0] TableBTBPredictionF;
logic [`XLEN-1:0] PredPCD;
logic UpdateEn;
// hashing function for indexing the PC
@ -78,14 +78,14 @@ module btb #(parameter Depth = 10 ) (
flopenr #(1) MatchReg(clk, reset, ~StallF, MatchNextX, MatchXF);
assign ForwardBTBPrediction = MatchF ? {BTBPredInstrClassF, PredPCF} :
MatchD ? {InstrClassD, PredPCD} :
assign ForwardBTBPrediction = MatchF ? {BTBPredInstrClassF, BTAF} :
MatchD ? {InstrClassD, BTAD} :
MatchE ? {InstrClassE, IEUAdrE} :
{InstrClassM, IEUAdrM} ;
flopenr #(`XLEN+4) ForwardBTBPredicitonReg(clk, reset, ~StallF, ForwardBTBPrediction, ForwardBTBPredictionF);
assign {BTBPredInstrClassF, PredPCF} = MatchXF ? ForwardBTBPredictionF : {TableBTBPredictionF};
assign {BTBPredInstrClassF, BTAF} = MatchXF ? ForwardBTBPredictionF : {TableBTBPredictionF};
assign UpdateEn = |InstrClassM | PredictionInstrClassWrongM;
@ -95,6 +95,6 @@ module btb #(parameter Depth = 10 ) (
.clk, .ce1(~StallF | reset), .ra1(PCNextFIndex), .rd1(TableBTBPredictionF),
.ce2(~StallW & ~FlushW), .wa2(PCMIndex), .wd2({InstrClassM, IEUAdrM}), .we2(UpdateEn), .bwe2('1));
flopenrc #(`XLEN) BTBD(clk, reset, FlushD, ~StallD, PredPCF, PredPCD);
flopenrc #(`XLEN) BTBD(clk, reset, FlushD, ~StallD, BTAF, BTAD);
endmodule