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Changes BTA to BPBTA.

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This commit is contained in:
Ross Thompson 2023-03-12 14:36:46 -05:00
parent e233b63752
commit ede9d49ce4
2 changed files with 23 additions and 23 deletions
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18
src/ifu/bpred/bpred.sv
View File

@ -71,7 +71,7 @@ module bpred (
logic [1:0] BPDirPredF;
logic [`XLEN-1:0] BTAF, RASPCF;
logic [`XLEN-1:0] BPBTAF, RASPCF;
logic BPPCWrongE;
logic IClassWrongE;
logic BPDirPredWrongE;
@ -85,7 +85,7 @@ module bpred (
logic BTBTargetWrongE;
logic RASTargetWrongE;
logic [`XLEN-1:0] BTAD;
logic [`XLEN-1:0] BPBTAD;
logic BTBCallF, BTBReturnF, BTBJumpF, BTBBranchF;
logic BPBranchF, BPJumpF, BPReturnF, BPCallF;
@ -95,7 +95,7 @@ module bpred (
logic BranchM, JumpM, ReturnM, CallM;
logic BranchW, JumpW, ReturnW, CallW;
logic BPReturnWrongD;
logic [`XLEN-1:0] BTAE;
logic [`XLEN-1:0] BPBTAE;
@ -150,7 +150,7 @@ module bpred (
btb #(`BTB_SIZE)
TargetPredictor(.clk, .reset, .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
.PCNextF, .PCF, .PCD, .PCE, .PCM,
.BTAF, .BTAD, .BTAE,
.BPBTAF, .BPBTAD, .BPBTAE,
.BTBIClassF({BTBCallF, BTBReturnF, BTBJumpF, BTBBranchF}),
.IClassWrongM, .IClassWrongE,
.IEUAdrE, .IEUAdrM,
@ -181,7 +181,7 @@ module bpred (
// Output the predicted PC or corrected PC on miss-predict.
assign BPPCSrcF = (BPBranchF & BPDirPredF[1]) | BPJumpF;
mux2 #(`XLEN) pcmuxbp(BTAF, RASPCF, BPReturnF, BPPCF);
mux2 #(`XLEN) pcmuxbp(BPBTAF, RASPCF, BPReturnF, BPPCF);
// Selects the BP or PC+2/4.
mux2 #(`XLEN) pcmux0(PCPlus2or4F, BPPCF, BPPCSrcF, PC0NextF);
// If the prediction is wrong select the correct address.
@ -196,7 +196,7 @@ module bpred (
if(`ZICOUNTERS_SUPPORTED) begin
logic [`XLEN-1:0] RASPCD, RASPCE;
logic BTBPredPCWrongE, RASPredPCWrongE;
logic BTAWrongE, RASPredPCWrongE;
// performance counters
// 1. class (class wrong / minstret) (IClassWrongM / csr) // Correct now
// 2. target btb (btb target wrong / class[0,1,3]) (btb target wrong / (br + j + jal)
@ -207,14 +207,14 @@ module bpred (
// 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.
// **** use BTAWrongM from BTB.
assign BTBPredPCWrongE = (BTAE != IEUAdrE) & (BranchE | JumpE & ~ReturnE) & PCSrcE;
// **** use BPBTAWrongM from BTB.
assign BTAWrongE = (BPBTAE != IEUAdrE) & (BranchE | JumpE & ~ReturnE) & PCSrcE;
assign RASPredPCWrongE = (RASPCE != IEUAdrE) & ReturnE & PCSrcE;
flopenrc #(`XLEN) RASTargetDReg(clk, reset, FlushD, ~StallD, RASPCF, RASPCD);
flopenrc #(`XLEN) RASTargetEReg(clk, reset, FlushE, ~StallE, RASPCD, RASPCE);
flopenrc #(3) BPPredWrongRegM(clk, reset, FlushM, ~StallM,
{BPDirPredWrongE, BTBPredPCWrongE, RASPredPCWrongE},
{BPDirPredWrongE, BTAWrongE, RASPredPCWrongE},
{BPDirPredWrongM, BTAWrongM, RASPredPCWrongM});
end else begin

28
src/ifu/bpred/btb.sv
View File

@ -35,9 +35,9 @@ 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] BTAF, // BTB's guess at PC
output logic [`XLEN-1:0] BTAD,
output logic [`XLEN-1:0] BTAE,
output logic [`XLEN-1:0] BPBTAF, // BTB's guess at PC
output logic [`XLEN-1:0] BPBTAD,
output logic [`XLEN-1:0] BPBTAE,
output logic [3:0] BTBIClassF, // BTB's guess at instruction class
// update
input logic IClassWrongM, // BTB's instruction class guess was wrong
@ -57,8 +57,8 @@ module btb #(parameter Depth = 10 ) (
logic [`XLEN+3:0] TableBTBPredF;
logic [`XLEN-1:0] IEUAdrW;
logic [`XLEN-1:0] PCW;
logic BTBWrongE, BTAWrongE;
logic BTBWrongM, BTAWrongM;
logic BTBWrongE, BPBTAWrongE;
logic BTBWrongM, BPBTAWrongM;
// hashing function for indexing the PC
@ -84,12 +84,12 @@ module btb #(parameter Depth = 10 ) (
assign MatchW = PCFIndex == PCWIndex;
assign MatchX = MatchD | MatchE | MatchM | MatchW;
assign ForwardBTBPredictionF = MatchD ? {InstrClassD, BTAD} :
assign ForwardBTBPredictionF = MatchD ? {InstrClassD, BPBTAD} :
MatchE ? {InstrClassE, IEUAdrE} :
MatchM ? {InstrClassM, IEUAdrM} :
{InstrClassW, IEUAdrW} ;
assign {BTBIClassF, BTAF} = MatchX ? ForwardBTBPredictionF : {TableBTBPredF};
assign {BTBIClassF, BPBTAF} = MatchX ? ForwardBTBPredictionF : {TableBTBPredF};
// An optimization may be using a PC relative address.
@ -97,16 +97,16 @@ module btb #(parameter Depth = 10 ) (
.clk, .ce1(~StallF | reset), .ra1(PCNextFIndex), .rd1(TableBTBPredF),
.ce2(~StallW & ~FlushW), .wa2(PCMIndex), .wd2({InstrClassM, IEUAdrM}), .we2(BTBWrongM), .bwe2('1));
flopenrc #(`XLEN) BTBD(clk, reset, FlushD, ~StallD, BTAF, BTAD);
flopenrc #(`XLEN) BTBD(clk, reset, FlushD, ~StallD, BPBTAF, BPBTAD);
// BTAE is not strickly necessary. However it is used by two parts of wally.
// BPBTAE is not strickly necessary. However it is used by two parts of wally.
// 1. It gates updates to the BTB when the prediction does not change. This save power.
// 2. BTAWrongE is used by the performance counters to track when the BTB's BTA or instruction class is wrong.
flopenrc #(`XLEN) BTBTargetEReg(clk, reset, FlushE, ~StallE, BTAD, BTAE);
assign BTAWrongE = (BTAE != IEUAdrE) & (InstrClassE[0] | InstrClassE[1] & ~InstrClassE[2]);
// 2. BPBTAWrongE is used by the performance counters to track when the BTB's BPBTA or instruction class is wrong.
flopenrc #(`XLEN) BTBTargetEReg(clk, reset, FlushE, ~StallE, BPBTAD, BPBTAE);
assign BPBTAWrongE = (BPBTAE != IEUAdrE) & (InstrClassE[0] | InstrClassE[1] & ~InstrClassE[2]);
flopenrc #(1) BTAWrongMReg(clk, reset, FlushM, ~StallM, BTAWrongE, BTAWrongM);
assign BTBWrongM = BTAWrongM | IClassWrongM;
flopenrc #(1) BPBTAWrongMReg(clk, reset, FlushM, ~StallM, BPBTAWrongE, BPBTAWrongM);
assign BTBWrongM = BPBTAWrongM | IClassWrongM;
flopenr #(`XLEN) PCWReg(clk, reset, ~StallW, PCM, PCW);
flopenr #(`XLEN) IEUAdrWReg(clk, reset, ~StallW, IEUAdrM, IEUAdrW);