From 8412c80bf488ad5c5b796bf4ea639b6f5f3957bf Mon Sep 17 00:00:00 2001
From: RossTheRoss <mstrapp@protonmail.com>
Date: Fri, 18 Dec 2020 19:13:58 -0600
Subject: ew

---
 ee4363/mp2/mipspipe_mp2.v | 81 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 55 insertions(+), 26 deletions(-)

(limited to 'ee4363')

diff --git a/ee4363/mp2/mipspipe_mp2.v b/ee4363/mp2/mipspipe_mp2.v
index 2e8b98b..303522a 100644
--- a/ee4363/mp2/mipspipe_mp2.v
+++ b/ee4363/mp2/mipspipe_mp2.v
@@ -10,12 +10,12 @@ module mipspipe_mp2 (clock);
              IFIDIR, IDEXA, IDEXB, IDEXIR, EXMEMIR, EXMEMB, // pipeline latches
              EXMEMALUOut, MEMWBValue, MEMWBIR;
 
-  wire [4:0] IDEXrs, IDEXrt, EXMEMrd, MEMWBrd, MEMWBrt; // hold register fields
-  wire [5:0] EXMEMop, MEMWBop, IDEXop; // hold opcodes
+  wire [4:0] IDEXrs, IDEXrt, EXMEMrd, MEMWBrd, MEMWBrt, IFIDrt, IFIDrs; // hold register fields
+  wire [5:0] EXMEMop, MEMWBop, IDEXop, IFIDop; // hold opcodes
   wire [31:0] Ain, Bin; // ALU inputs
 
   // declare the bypass signals
-  wire bypassAfromMEM, bypassAfromALUinWB, bypassBfromMEM, bypassBfromALUinWB, bypassAfromLWinWB, bypassBfromLWinWB;
+  wire bypassAfromMEM, bypassAfromALUinWB, bypassBfromMEM, bypassBfromALUinWB, bypassAfromLWinWB, bypassBfromLWinWB, bypassIDEXAfromWB, bypassIDEXBfromWB, STALL;
 
    // Define fields of pipeline latches
    assign IDEXrs = IDEXIR[25:21]; // rs field
@@ -26,6 +26,9 @@ module mipspipe_mp2 (clock);
    assign EXMEMop = EXMEMIR[31:26]; // opcode
    assign MEMWBop = MEMWBIR[31:26]; // opcode
    assign IDEXop = IDEXIR[31:26]; // opcode
+   assign IFIDrs = IFIDIR[25:21];
+   assign IFIDrt = IFIDIR[20:16];
+   assign IFIDop = IFIDIR[31:26]; 
 
 
   // The bypass to input A from the MEM stage for an ALU operation
@@ -40,18 +43,30 @@ module mipspipe_mp2 (clock);
   assign bypassAfromLWinWB = (IDEXrs == MEMWBIR[20:16]) & (IDEXrs!=0) & (MEMWBop==LW);
   // The bypass to input B from the WB stage for an LW operation
   assign bypassBfromLWinWB = 0;
-
+  //Stall in case of WB
+  assign bypassIDEXAfromWB = ((MEMWBIR != nop) & (IFIDIR != nop) & (IFIDrs == MEMWBrt) & (MEMWBop == LW)) | 
+    ((MEMWBop == ALUop) & (MEMWBrd == IFIDrs)); 
+  assign bypassIDEXBfromWB = ((MEMWBIR != nop) & (IFIDIR != nop) & (IFIDrt == MEMWBrt) & (MEMWBop == LW)) | 
+    ((MEMWBop == ALUop) & (MEMWBrd == IFIDrt)); 
   // The A input to the ALU is bypassed from MEM if there is a bypass there,
   // Otherwise from WB if there is a bypass there, and otherwise comes from the IDEX register
   assign Ain = bypassAfromMEM? EXMEMALUOut : (bypassAfromALUinWB | bypassAfromLWinWB)? MEMWBValue : IDEXA;
 
   // The B input to the ALU is bypassed from MEM if there is a bypass there,
   // Otherwise from WB if there is a bypass there, and otherwise comes from the IDEX register
-  assign Bin = IDEXB;
+  // Ripped off of above just replacing "A" with "B"
+  assign Bin = bypassBfromMEM? EXMEMALUOut : (bypassBfromALUinWB | bypassBfromLWinWB)? MEMWBValue : IDEXB;
 
 
   reg [5:0] i; // used to initialize latches
   reg [10:0] j,k; // used to initialize memories
+
+  // Make the Big Stall
+  assign STALL = (IDEXop == LW) && 
+    //All of this is anded with the above (Lisp would be proud)
+    (((IFIDop == LW) && (IFIDrs == IDEXrt)) |
+    ((IFIDop == ALUop) && ((IFIDrs == IDEXrt) | (IFIDrt == IDEXrt))) |
+    ((IFIDop == SW) && ((IFIDrs == IDEXrt) | (IFIDrt == IDEXrt))));
   
   initial begin
     PC = 0;
@@ -62,16 +77,16 @@ module mipspipe_mp2 (clock);
   
     for (i = 0;i<=31;i = i+1) Regs[i] = i; // initialize latches
   
-    IMemory[0] = 32'h00412820;
-    IMemory[1] = 32'h8ca30004;
-    IMemory[2] = 32'haca70005;
-    IMemory[3] = 32'h00602020;
-    IMemory[4] = 32'h01093020;
-    IMemory[5] = 32'hac06000c;  
-    IMemory[6] = 32'h00c05020;
-    IMemory[7] = 32'h8c0b0010;
-    IMemory[8] = 32'h00000020;  
-    IMemory[9] = 32'h002b6020;
+    IMemory[0] = 32'h00412820; // ADD $5, $2, $1
+    IMemory[1] = 32'h8ca30004; // LW $3, 4($5)
+    IMemory[2] = 32'haca70005; // SW $7, 5($5)
+    IMemory[3] = 32'h00602020; // ADD $4, $3, $0
+    IMemory[4] = 32'h01093020; // ADD $6, $8, $9
+    IMemory[5] = 32'hac06000c; // SW $6, $12($0)
+    IMemory[6] = 32'h00c05020; // ADD $10, $6, $0
+    IMemory[7] = 32'h8c0b0010; // LW $11, 32($0)
+    IMemory[8] = 32'h00000020; // ADD $0, $0, $0
+    IMemory[9] = 32'h002b6020; // ADD $12, $1, $11
     for (j=10; j<=1023; j=j+1) IMemory[j] = nop;
     
     DMemory[0] = 32'h00000000;
@@ -82,17 +97,31 @@ module mipspipe_mp2 (clock);
     for (k=5; k<=1023; k=k+1) DMemory[k] = 0;
   end
 
-  always @ (posedge clock) 
-  begin
-    
-	// FETCH: Fetch instruction & update PC
-    IFIDIR <= IMemory[PC>>2];
-    PC <= PC + 4;
-
-    // DECODE: Read registers
-    IDEXA <= Regs[IFIDIR[25:21]]; 
-    IDEXB <= Regs[IFIDIR[20:16]];
-    IDEXIR <= IFIDIR; 
+  always @ (posedge clock) begin
+    if (~STALL) begin
+	  // FETCH: Fetch instruction & update PC
+      IFIDIR <= IMemory[PC>>2];
+      PC <= PC + 4;
+
+      // DECODE: Read registers
+      if (~bypassIDEXAfromWB) begin
+        IDEXA <= Regs[IFIDIR[25:21]]; 
+      end 
+       else begin
+          IDEXA <= MEMWBValue;
+      end
+
+      if (~bypassIDEXBfromWB) begin
+        IDEXB <= Regs[IFIDIR[20:16]];
+      end 
+       else begin
+        IDEXB <= MEMWBValue;
+      end
+        IDEXIR <= IFIDIR; 
+    end 
+     else begin //IF (STALL)
+        IDEXIR <= nop;
+    end
 
     // EX: Address calculation or ALU operation
     if ((IDEXop==LW) |(IDEXop==SW)) // address calculation & copy B
-- 
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