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Updated global history predictor.

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This commit is contained in:
Ross Thompson 2023-02-17 15:53:15 -06:00
parent 0d271130b9
commit df4a27a2e3
1 changed files with 13 additions and 7 deletions
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20
src/ifu/bpred/speculativeglobalhistory.sv
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@ -28,7 +28,7 @@
`include "wally-config.vh"
module speculativeglobalhistory #(parameter int k = 10 ) (
module speculativegshare #(parameter int k = 10 ) (
input logic clk,
input logic reset,
input logic StallF, StallD, StallE, StallM, StallW,
@ -57,9 +57,9 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
logic FlushDOrDirWrong;
assign IndexNextF = GHRNextF;
assign IndexF = GHRF;
assign IndexD = GHRD;
assign IndexE = GHRE;
assign IndexF = GHRF ;
assign IndexD = GHRD[k-1:0] ;
assign IndexE = GHRE[k-1:0] ;
ram2p1r1wbe #(2**k, 2) PHT(.clk(clk),
.ce1(~StallF | reset), .ce2(~StallM & ~FlushM),
@ -100,9 +100,16 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
// If the front end is flushed or the direction prediction is wrong, reset to
// most recent valid GHR. For a BP wrong this is GHRD with the correct prediction shifted in.
// For FlushE this is GHRE. GHRNextE is both.
logic [k-1:0] GHRClassWrongAndPredF;
logic [k-1:0] GHRClassWrong;
mux2 #(k) GHRClassWrongAndPredFMux({DirPredictionF[1], DirPredictionD[1], GHRF[k-1:2]}, {DirPredictionF[1], GHRF[k-2:0]}, ~InstrClassD[0], GHRClassWrongAndPredF);
assign FlushDOrDirWrong = FlushD | DirPredictionWrongE;
mux3 #(k) GHRFMux(GHRF, {DirPredictionF[1], GHRF[k-1:1]}, GHRNextE[k-1:0],
{FlushDOrDirWrong, PredInstrClassF[0]}, GHRNextF);
// mux3 #(k) GHRFMux(GHRF, {DirPredictionF[1], GHRF[k-1:1]}, GHRNextE[k-1:0],
// {FlushDOrDirWrong, PredInstrClassF[0]}, GHRNextF);
mux5 #(k) GHRFMux(GHRF, {DirPredictionF[1], GHRF[k-1:1]}, GHRClassWrong, GHRClassWrongAndPredF, GHRNextE[k-1:0],
{FlushDOrDirWrong, WrongPredInstrClassD[0], PredInstrClassF[0]}, GHRNextF);
// Need 1 extra bit to store the shifted out GHRF if repair needs to back shift.
flopenr #(k) GHRFReg(clk, reset, ~StallF | FlushDOrDirWrong, GHRNextF, GHRF);
@ -111,7 +118,6 @@ module speculativeglobalhistory #(parameter int k = 10 ) (
// With instruction class prediction, the class could be wrong and is checked in Decode.
// If it is wrong and branch does exist then shift right and insert the prediction.
// If the branch does not exist then shift left and use GHRLastF to restore the LSB.
logic [k-1:0] GHRClassWrong;
mux2 #(k) GHRClassWrongMux({DirPredictionD[1], GHRF[k-1:1]}, {GHRF[k-2:0], GHRLastF}, ~InstrClassD[0], GHRClassWrong);
// As with GHRF FlushD and wrong direction prediction flushes the pipeline and restores to GHRNextE.
mux3 #(k) GHRDMux(GHRF, GHRClassWrong, GHRNextE, {FlushDOrDirWrong, WrongPredInstrClassD[0]}, GHRNextD);