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Clarified gshare bp.

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This commit is contained in:
Ross Thompson 2023-01-27 16:40:20 -06:00
parent 121fbd9646
commit a953954909
1 changed files with 7 additions and 14 deletions
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21
pipelined/src/ifu/brpred/speculativegshare.sv
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@ -55,7 +55,7 @@ module speculativegshare
logic OldGHRExtraF;
logic [k:0] GHRD, OldGHRE, GHRE, GHRM, GHRW;
logic [k-1:0] GHRNextF;
logic [k:-1] GHRNextD, OldGHRD;
logic [k:0] GHRNextD;
logic [k:0] GHRNextE, GHRNextM, GHRNextW;
logic [k-1:0] IndexNextF, IndexF;
logic [k-1:0] IndexD, IndexE;
@ -107,11 +107,9 @@ module speculativegshare
// GHR pipeline
// this version fails the regression test do to pessimistic x propagation.
/* -----\/----- EXCLUDED -----\/-----
assign GHRNextF = FlushD ? (BranchInstrE ? GHRNextD[k:1] : GHRNextD[k-1:0]) :
BranchInstrF ? {DirPredictionF[1], GHRF[k-1:1]} :
GHRF;
-----/\----- EXCLUDED -----/\----- */
// assign GHRNextF = FlushD ? (BranchInstrE ? GHRNextD[k:1] : GHRNextD[k-1:0]) :
// BranchInstrF ? {DirPredictionF[1], GHRF[k-1:1]} :
// GHRF;
always_comb begin
if(FlushD) begin
@ -121,20 +119,15 @@ module speculativegshare
else GHRNextF = GHRF;
end
flopenr #(k) GHRFReg(clk, reset, (~StallF) | FlushD, GHRNextF, OldGHRF);
flopenr #(1) GHRFExtraReg(clk, reset, (~StallF) | FlushD, GHRNextF[0], OldGHRExtraF);
assign GHRF = WrongPredInstrClassD[0] & BranchInstrD ? {DirPredictionD[1], OldGHRF[k-1:1]} : // shift right
WrongPredInstrClassD[0] & ~BranchInstrD ? {OldGHRF[k-2:0], OldGHRExtraF} : // shift left **** missing bit
WrongPredInstrClassD[0] & ~BranchInstrD ? {OldGHRF[k-2:0], OldGHRExtraF}: // shift left
OldGHRF[k-1:0];
assign GHRNextD = FlushD ? {GHRNextE, GHRNextE[0]} : {DirPredictionF[1], GHRF, GHRF[0]};
assign GHRNextD = FlushD ? {GHRNextE} : {DirPredictionF[1], GHRF};
flopenr #(k+2) GHRDReg(clk, reset, (~StallD) | FlushD, GHRNextD, OldGHRD);
//assign GHRD = WrongPredInstrClassD[0] & BranchInstrD ? {DirPredictionD[1], OldGHRD[k:1]} : // shift right
// WrongPredInstrClassD[0] & ~BranchInstrD ? OldGHRD[k-1:-1] : // shift left
// OldGHRD[k:0];
assign GHRD = OldGHRD[k:0];
flopenr #(k+1) GHRDReg(clk, reset, (~StallD) | FlushD, GHRNextD, GHRD);
assign GHRNextE = FlushE ? GHRNextM : GHRD;
flopenr #(k+1) GHREReg(clk, reset, (~StallE) | FlushE, GHRNextE, OldGHRE);