Partial fix to RAS prediction accurracy.

pipelined/src/ifu/RAsPredictor.sv

@@ -35,6 +35,8 @@ module RASPredictor
    input logic 				reset,
    input logic 				PopF,
    output logic [`XLEN-1:0] RASPCF,
+   input logic [3:0] 		WrongPredInstrClassD,
+   input logic [3:0] 		InstrClassD,
    input logic 				PushE,
    input logic 				incr,
    input logic [`XLEN-1:0] 	PCLinkE
@@ -50,9 +52,9 @@ module RASPredictor
   logic [StackSize-1:0]     [`XLEN-1:0] memory;
   integer        index;
   
-  assign CounterEn = PopF | PushE | incr;
+  assign CounterEn = PopF | PushE | incr | WrongPredInstrClassD[2];
 
-  assign PtrD = PopF ? PtrM1 : PtrP1;
+  assign PtrD = PopF | InstrClassD[2] ? PtrM1 : PtrP1;
 
   assign PtrM1 = PtrQ - 1'b1;
   assign PtrP1 = PtrQ + 1'b1;

pipelined/src/ifu/bpred.sv

@@ -79,6 +79,7 @@ module bpred (
   logic                     BPPredWrongM;
   logic [`XLEN-1:0]         PCNext0F;
   logic [`XLEN-1:0] 		PCCorrectE;
+  logic [3:0] 				WrongPredInstrClassD;
   
   // Part 1 branch direction prediction
   // look into the 2 port Sram model. something is wrong. 
@@ -157,6 +158,8 @@ module bpred (
   RASPredictor RASPredictor(.clk(clk),
        .reset(reset),
        .PopF(PredInstrClassF[2] & ~StallF),
+							.WrongPredInstrClassD,
+							.InstrClassD,
        .RASPCF,
        .PushE(InstrClassE[3] & ~StallE),
        .incr(1'b0),
@@ -214,6 +217,9 @@ module bpred (
   // Finally if the real instruction class is non CFI but the predictor said it was we need to count.
   assign BPPredClassNonCFIWrongE = PredictionInstrClassWrongE & ~|InstrClassE;
 
+  // branch class prediction wrong.
+  assign WrongPredInstrClassD = PredInstrClassD ^ InstrClassD;
+  
   
   // Selects the BP or PC+2/4.
   mux2 #(`XLEN) pcmux0(PCPlus2or4F, BPPredPCF, SelBPPredF, PCNext0F);