added branch predictor 2 bit table + SRAM model. The SRAM model is only approximate, but it does correctly model the read and write pipelined behavior.

wally-pipelined/src/ifu/SramModel.sv

@@ -0,0 +1,96 @@
+///////////////////////////////////////////
+// SRAM2P1R1W
+//
+// Written: Ross Thomposn
+// Email: ross1728@gmail.com
+// Created: February 14, 2021
+// Modified: 
+//
+// Purpose: Hacky two port SRAM model.
+// 
+// A component of the Wally configurable RISC-V project.
+// 
+// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
+// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
+// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
+// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+///////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module SRAM2P1R1W
+  #(parameter int Depth = 10,
+    parameter int Width = 2
+    ) 
+  (input clk,
+    
+   // port 1 is read only
+   input logic [Depth-1:0]  RA1,
+   output logic [Width-1:0] RD1,
+   input logic 		    REN1,
+  
+   // port 2 is write only
+   input logic [Depth-1:0]  WA1,
+   input logic [Width-1:0]  WD1,
+   input logic 		    WEN1
+   );
+  
+  
+
+
+
+  logic [Depth-1:0] 	    RA1Q, WA1Q;
+  logic 		    WEN1Q;
+  logic [Width-1:0] 	    WD1Q;
+
+  logic [2**Depth-1:0] [Width-1:0] memory;
+  
+  
+  // SRAMs address busses are always registered first.
+
+  flopenr #(Depth) RA1Reg(.clk(clk),
+			  .reset(1'b0),
+			  .en(REN1),
+			  .d(RA1),
+			  .q(RA1Q));
+  
+
+  flopenr #(Depth) WA1Reg(.clk(clk),
+			  .reset(1'b0),
+			  .en(REN1),
+			  .d(WA1),
+			  .q(WA1Q));
+
+  flopenr #(1) WEN1Reg(.clk(clk),
+		       .reset(1'b0),
+		       .en(1'b1),
+		       .d(WEN1),
+		       .q(WEN1Q));
+  
+  flopenr #(Width) WD1Reg(.clk(clk),
+			  .reset(1'b0),
+			  .en(REN1),
+			  .d(WD1),
+			  .q(WD1Q));
+  // read port
+  assign RD1 = memory[RA1Q];
+  
+  // write port
+  always_ff @ (posedge clk) begin
+    if (WEN1Q) begin
+      memory[WA1Q] = WD1Q;
+    end
+  end
+
+endmodule  
+
+

wally-pipelined/src/ifu/bpred.sv

@@ -91,8 +91,8 @@ module bpred
 
   assign SelBPPredF = ((InstrClassF[0] & BPPredF[1]) | 
 		       InstrClassF[3] |
-		       (InstrClassF[2]) | 
+		       (InstrClassF[2] & BTBValidF) | 
-		       InstrClassF[1]) & BTBValidF;
+		       InstrClassF[1]) ;
 
 
   // Part 3 Branch target address prediction
@@ -163,8 +163,4 @@ module bpred
 			  .OldState(BPPredE),
 			  .NewState(UpdateBPPredE));
 
-  
+endmodule
-  
-  
-
-  

wally-pipelined/src/ifu/twoBitPredictor.sv

@@ -0,0 +1,53 @@
+///////////////////////////////////////////
+// twoBitPredictor.sv
+//
+// Written: Ross Thomposn
+// Email: ross1728@gmail.com
+// Created: February 14, 2021
+// Modified: 
+//
+// Purpose: 2 bit saturating counter predictor with parameterized table depth.
+// 
+// A component of the Wally configurable RISC-V project.
+// 
+// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
+// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
+// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
+// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+///////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module twoBitPredictor
+  #(parameter int Depth = 10
+    )
+  (input clk,
+   input [`XLEN-1:0] LookUpPC,
+   output [1:0]      Prediction,
+   // update
+   input [`XLEN-1:0] UpdatePC,
+   input 	     UpdateEN,
+   input [1:0] 	     UpdatePrediction
+   );
+
+  SRAM2P1R1W #(Depth, 2) memory(.clk(clk),
+				.RA1(LookUpPC),
+				.RD1(PredictionMemory),
+				.REN1(1'b1),
+				.WA1(UpdatePC),
+				.WD1(UpdatePrediction),
+				.WEN1(UpdateEN));
+
+  // need to forward when updating to the same address as reading.
+  assign Prediction = (UpdatePC == LookUpPC) ? UpdatePrediction : PredictionMemory;
+  
+endmodule