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Fixed forwarding bug in the BTB.

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This commit is contained in:
Ross Thompson 2023-02-20 16:18:04 -06:00
parent fdd007a903
commit d2b7047744
2 changed files with 5 additions and 5 deletions
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2
src/ifu/bpred/bpred.sv
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@ -148,7 +148,7 @@ module bpred (
.PCNextF, .PCF, .PCD, .PCE, .PCM,
.PredPCF,
.BTBPredInstrClassF,
.AnyWrongPredInstrClassE,
.PredictionInstrClassWrongM,
.IEUAdrE, .IEUAdrM,
.InstrClassD, .InstrClassE, .InstrClassM);

8
src/ifu/bpred/btb.sv
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@ -38,7 +38,7 @@ module btb #(parameter Depth = 10 ) (
output logic [`XLEN-1:0] PredPCF, // BTB's guess at PC
output logic [3:0] BTBPredInstrClassF, // BTB's guess at instruction class
// update
input logic AnyWrongPredInstrClassE, // BTB's instruction class guess was wrong
input logic PredictionInstrClassWrongM, // BTB's instruction class guess was wrong
input logic [`XLEN-1:0] IEUAdrE, // Branch/jump target address to insert into btb
input logic [`XLEN-1:0] IEUAdrM, // Branch/jump target address to insert into btb
input logic [3:0] InstrClassD, // Instruction class to insert into btb
@ -74,7 +74,7 @@ module btb #(parameter Depth = 10 ) (
assign MatchD = PCNextFIndex == PCDIndex;
assign MatchE = PCNextFIndex == PCEIndex;
assign MatchM = PCNextFIndex == PCMIndex;
assign MatchNextX = MatchF | MatchD | MatchE;
assign MatchNextX = MatchF | MatchD | MatchE | MatchM;
flopenr #(1) MatchReg(clk, reset, ~StallF, MatchNextX, MatchXF);
@ -88,12 +88,12 @@ module btb #(parameter Depth = 10 ) (
assign {BTBPredInstrClassF, PredPCF} = MatchXF ? ForwardBTBPredictionF : {TableBTBPredictionF};
assign UpdateEn = |InstrClassE | AnyWrongPredInstrClassE;
assign UpdateEn = |InstrClassM | PredictionInstrClassWrongM;
// An optimization may be using a PC relative address.
ram2p1r1wbe #(2**Depth, `XLEN+4) memory(
.clk, .ce1(~StallF | reset), .ra1(PCNextFIndex), .rd1(TableBTBPredictionF),
.ce2(~StallM & ~FlushM), .wa2(PCEIndex), .wd2({InstrClassE, IEUAdrE}), .we2(UpdateEn), .bwe2('1));
.ce2(~StallM & ~FlushM), .wa2(PCMIndex), .wd2({InstrClassM, IEUAdrM}), .we2(UpdateEn), .bwe2('1));
flopenrc #(`XLEN) BTBD(clk, reset, FlushD, ~StallD, PredPCF, PredPCD);