Baseline localhistory with speculative repair built.

src/ifu/bpred/bpred.sv

@@ -137,6 +137,11 @@ module bpred (
       .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
       .PCNextF, .PCM, .BPDirPredD(BPDirPredF), .BPDirPredWrongE,
       .BranchE, .BranchM, .PCSrcE);
+  end else if (`BPRED_TYPE == "BP_LOCAL_REPAIR") begin:Predictor
+    localreapirbp #(`BPRED_NUM_LHR, `BPRED_SIZE) DirPredictor(.clk, .reset, 
+      .StallF, .StallD, .StallE, .StallM, .StallW, .FlushD, .FlushE, .FlushM, .FlushW,
+      .PCNextF, .PCE, .PCM, .BPDirPredD(BPDirPredF), .BPDirPredWrongE,
+      .BranchD, .BranchE, .BranchM, .PCSrcE);
   end 
 
   // Part 2 Branch target address prediction

src/ifu/bpred/localrepairbp.sv

@@ -0,0 +1,137 @@
+///////////////////////////////////////////
+// gsharebasic.sv
+//
+// Written: Ross Thompson
+// Email: ross1728@gmail.com
+// Created: 16 March 2021
+// Adapted from ssanghai@hmc.edu (Shreya Sanghai) global history predictor implementation.
+// Modified: 20 February 2023 
+//
+// Purpose: Global History Branch predictor with parameterized global history register
+// 
+// A component of the CORE-V-WALLY configurable RISC-V project.
+// 
+// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
+//
+// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
+//
+// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file 
+// except in compliance with the License, or, at your option, the Apache License version 2.0. You 
+// may obtain a copy of the License at
+//
+// https://solderpad.org/licenses/SHL-2.1/
+//
+// Unless required by applicable law or agreed to in writing, any work distributed under the 
+// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+// either express or implied. See the License for the specific language governing permissions 
+// and limitations under the License.
+////////////////////////////////////////////////////////////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module localreapirbp #(parameter m = 6, // 2^m = number of local history branches 
+                      parameter k = 10) ( // number of past branches stored
+  input logic             clk,
+  input logic             reset,
+  input logic             StallF, StallD, StallE, StallM, StallW,
+  input logic             FlushD, FlushE, FlushM, FlushW,
+  output logic [1:0]      BPDirPredD, 
+  output logic            BPDirPredWrongE,
+  // update
+  input logic [`XLEN-1:0] PCNextF, PCE, PCM,
+  input logic             BranchD, BranchE, BranchM, PCSrcE
+);
+
+  //logic [1:0]             BPDirPredD, BPDirPredE;
+  logic [1:0]             BPDirPredE;
+  logic [1:0]             BPDirPredM;
+  logic [1:0]             NewBPDirPredE, NewBPDirPredM, NewBPDirPredW;
+
+  logic [k-1:0]           LHRF, LHRD, LHRE, LHRM, LHRW, LHRNextF;
+  logic [k-1:0]           LHRNextW;
+  logic                   PCSrcM;
+  logic [2**m-1:0][k-1:0] LHRArray;
+  logic [m-1:0]           IndexLHRNextF, IndexLHRM;
+  logic [`XLEN-1:0]       PCW;
+
+  logic [k-1:0]           LHRCommittedF, LHRSpeculativeF;
+  logic [m-1:0]           IndexLHRD;
+  logic [k-1:0]           LHRNextE;
+  logic                   SpeculativeFlushedF;
+  
+  
+  ram2p1r1wbe #(2**k, 2) PHT(.clk(clk),
+    .ce1(~StallD), .ce2(~StallW & ~FlushW),
+    .ra1(LHRF),
+    .rd1(BPDirPredD),
+    .wa2(LHRW),
+    .wd2(NewBPDirPredW),
+    .we2(BranchM),
+    .bwe2(1'b1));
+
+  //flopenrc #(2) PredictionRegD(clk, reset,  FlushD, ~StallD, BPDirPredF, BPDirPredD);
+  flopenrc #(2) PredictionRegE(clk, reset,  FlushE, ~StallE, BPDirPredD, BPDirPredE);
+  flopenrc #(2) PredictionRegM(clk, reset,  FlushM, ~StallM, BPDirPredE, BPDirPredM);
+
+  satCounter2 BPDirUpdateE(.BrDir(PCSrcE), .OldState(BPDirPredM), .NewState(NewBPDirPredM));
+  //flopenrc #(2) NewPredictionRegM(clk, reset,  FlushM, ~StallM, NewBPDirPredE, NewBPDirPredM);
+  flopenrc #(2) NewPredictionRegW(clk, reset,  FlushW, ~StallW, NewBPDirPredM, NewBPDirPredW);
+
+  assign BPDirPredWrongE = PCSrcE != BPDirPredM[1] & BranchE;
+
+  // This is the main difference between global and local history basic implementations. In global, 
+  // the ghr wraps back into itself directly without
+  // being pipelined.  I.E. GHR is not read in F and then pipelined to M where it is updated.  Instead
+  // GHR is both read and update in M.  GHR is still pipelined so that the PHT is updated with the correct
+  // GHR.  Local history in contrast must pipeline the specific history register read during F and then update
+  // that same one in M.  This implementation does not forward if a branch matches in the D, E, or M stages.
+  assign LHRNextW = BranchM ? {PCSrcM, LHRW[k-1:1]} : LHRW;
+
+  // this is local history
+  assign IndexLHRM = {PCW[m+1] ^ PCW[1], PCW[m:2]};
+  assign IndexLHRNextF = {PCNextF[m+1] ^ PCNextF[1], PCNextF[m:2]};
+
+  ram2p1r1wbe #(2**m, k) BHT(.clk(clk),
+    .ce1(~StallF), .ce2(~StallW & ~FlushW),
+    .ra1(IndexLHRNextF),
+    .rd1(LHRCommittedF),
+    .wa2(IndexLHRM),
+    .wd2(LHRNextW),
+    .we2(BranchM),
+    .bwe2('1));
+
+  assign IndexLHRD = {PCE[m+1] ^ PCE[1], PCE[m:2]};
+  assign LHRNextE = BranchD ? {BPDirPredD[1], LHRE[k-1:1]} : LHRE;
+  // *** replace with a small CAM
+  ram2p1r1wbe #(2**m, k) SHB(.clk(clk),
+    .ce1(~StallF), .ce2(~StallE & ~FlushE),
+    .ra1(IndexLHRNextF),
+    .rd1(LHRSpeculativeF),
+    .wa2(IndexLHRD),
+    .wd2(LHRNextE),
+    .we2(BranchD),
+    .bwe2('1));
+  // **** replace with small CAM
+  logic [2**m-1:0]        FlushedBits;
+  always_ff @(posedge clk) begin // Valid bit array,
+    SpeculativeFlushedF <= #1 FlushedBits[IndexLHRNextF];
+    if (reset | FlushD) FlushedBits        <= #1 '1;
+    if(BranchD & ~StallE & ~FlushE) begin
+      FlushedBits[IndexLHRD] <= #1 '0;
+    end
+  end
+
+  mux2 #(k) LHRMux(LHRSpeculativeF, LHRCommittedF, SpeculativeFlushedF, LHRF);
+
+  flopenrc #(1) PCSrcMReg(clk, reset, FlushM, ~StallM, PCSrcE, PCSrcM);
+    
+  //flopenrc #(k) LHRFReg(clk, reset, FlushD, ~StallF, LHRNextF, LHRF);
+  //assign LHRF = LHRNextF;
+  flopenrc #(k) LHRDReg(clk, reset, FlushD, ~StallD, LHRF, LHRD);
+  flopenrc #(k) LHREReg(clk, reset, FlushE, ~StallE, LHRD, LHRE);
+  flopenrc #(k) LHRMReg(clk, reset, FlushM, ~StallM, LHRE, LHRM);
+  flopenrc #(k) LHRWReg(clk, reset, FlushW, ~StallW, LHRM, LHRW);
+
+  flopenr #(`XLEN) PCWReg(clk, reset, ~StallW, PCM, PCW);
+
+endmodule

testbench/testbench.sv

@@ -537,7 +537,7 @@ module testbench;
     integer adrindex;
 
     // local history only
-    if (`BPRED_TYPE == "BP_LOCAL_AHEAD") begin
+    if (`BPRED_TYPE == "BP_LOCAL_AHEAD" | `BPRED_TYPE == "BP_LOCAL_REPAIR") begin
       always @(*) begin
         if(reset) begin
           for(adrindex = 0; adrindex < 2**`BPRED_NUM_LHR; adrindex++) begin