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Partial improvement.

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This commit is contained in:
Ross Thompson 2023-02-13 17:10:24 -06:00
parent f4af38a004
commit 717cba270c
1 changed files with 5 additions and 6 deletions
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11
src/ifu/bpred/bpred.sv
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@ -220,9 +220,7 @@ module bpred (
end else begin
assign PredInstrClassF = BTBPredInstrClassF;
assign SelBPPredF = (PredInstrClassF[0] & DirPredictionF[1] & PredValidF) |
PredInstrClassF[2] |
(PredInstrClassF[1] & PredValidF) |
(PredInstrClassF[3] & PredValidF);
PredInstrClassF[1] & PredValidF;
end
// Part 3 RAS
@ -232,17 +230,18 @@ module bpred (
assign BPPredPCF = PredInstrClassF[2] ? RASPCF : PredPCF;
/* -----\/----- EXCLUDED -----\/-----
assign InstrClassD[0] = BranchD;
assign InstrClassD[1] = JumpD ;
assign InstrClassD[2] = JumpD & (InstrD[19:15] & 5'h1B) == 5'h01; // return must return to ra or x5
assign InstrClassD[3] = JumpD & (InstrD[11:7] & 5'h1B) == 5'h01; // jal(r) must link to ra or x5
-----/\----- EXCLUDED -----/\----- */
/* -----\/----- EXCLUDED -----\/-----
assign InstrClassD[3] = (InstrD[6:0] & 7'h77) == 7'h67 & (InstrD[11:07] & 5'h1B) == 5'h01; // jal(r) must link to ra or x5
assign InstrClassD[2] = InstrD[6:0] == 7'h67 & (InstrD[19:15] & 5'h1B) == 5'h01; // return must return to ra or r5
assign InstrClassD[1] = (InstrD[6:0] == 7'h67 & (InstrD[19:15] & 5'h1B) != 5'h01 & (InstrD[11:7] & 5'h1B) != 5'h01) | // jump register, but not return
(InstrD[6:0] == 7'h6F & (InstrD[11:7] & 5'h1B) != 5'h01); // jump, RD != x1 or x5
assign InstrClassD[0] = InstrD[6:0] == 7'h63; // branch
-----/\----- EXCLUDED -----/\----- */
@ -274,7 +273,7 @@ module bpred (
assign AnyWrongPredInstrClassD = |WrongPredInstrClassD;
// branch is wrong only if the PC does not match and both the Decode and Fetch stages have valid instructions.
assign BPPredWrongE = (PredictionPCWrongE & |InstrClassE) | (AnyWrongPredInstrClassE & ~|InstrClassE);
assign BPPredWrongE = (PredictionPCWrongE & |InstrClassE | (AnyWrongPredInstrClassE & ~|InstrClassE));
//assign BPPredWrongE = PredictionPCWrongE & InstrValidE & InstrValidD;
// Output the predicted PC or corrected PC on miss-predict.