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Possible fix to btb performance issue.

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This commit is contained in:
Ross Thompson 2023-02-24 18:36:41 -06:00
parent ea8cb7dd78
commit 4031b89f18
2 changed files with 5 additions and 6 deletions
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2
src/ifu/bpred/bpred.sv
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@ -285,7 +285,7 @@ module bpred (
// **** Fix me
assign InstrClassM = {JalM, RetM, JumpM, BranchM};
flopenr #(`XLEN) PCWReg(clk, reset, ~StallW, PCM, PCW);
flopenrc #(`XLEN) IEUAdrWReg(clk, reset, FlushW, ~StallW, IEUAdrM, IEUAdrW);
flopenr #(`XLEN) IEUAdrWReg(clk, reset, ~StallW, IEUAdrM, IEUAdrW);
endmodule

9
src/ifu/bpred/btb.sv
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@ -51,7 +51,7 @@ module btb #(parameter Depth = 10 ) (
logic [Depth-1:0] PCNextFIndex, PCFIndex, PCDIndex, PCEIndex, PCMIndex, PCWIndex;
logic [`XLEN-1:0] ResetPC;
logic MatchF, MatchD, MatchE, MatchM, MatchW, MatchX;
logic MatchD, MatchE, MatchM, MatchW, MatchX;
logic [`XLEN+3:0] ForwardBTBPrediction, ForwardBTBPredictionF;
logic [`XLEN+3:0] TableBTBPredictionF;
logic UpdateEn;
@ -73,7 +73,6 @@ module btb #(parameter Depth = 10 ) (
assign ResetPC = `RESET_VECTOR;
assign PCNextFIndex = reset ? ResetPC[Depth+1:2] : {PCNextF[Depth+1] ^ PCNextF[1], PCNextF[Depth:2]};
assign MatchF = PCNextFIndex == PCFIndex;
assign MatchD = PCFIndex == PCDIndex;
assign MatchE = PCFIndex == PCEIndex;
assign MatchM = PCFIndex == PCMIndex;
@ -81,9 +80,9 @@ module btb #(parameter Depth = 10 ) (
assign MatchX = MatchD | MatchE | MatchM | MatchW;
assign ForwardBTBPredictionF = MatchD ? {InstrClassD, BTAD} :
MatchE ? {InstrClassE, IEUAdrE} :
MatchM ? {InstrClassM, IEUAdrM} :
{InstrClassW, IEUAdrW} ;
MatchE ? {InstrClassE, IEUAdrE} :
MatchM ? {InstrClassM, IEUAdrM} :
{InstrClassW, IEUAdrW} ;
assign {BTBPredInstrClassF, BTAF} = MatchX ? ForwardBTBPredictionF : {TableBTBPredictionF};