Execute: fix rdiff

[firearm.git] / Fetch.v

diff --git a/Fetch.v b/Fetch.v
index 0a18b31e6e9a4c68cc5b83112257e5ea58c1a7d2..2a9d69d735afae91ee6f89338e555b931b5545a0 100644 (file)
--- a/Fetch.v
+++ b/Fetch.v
@@ -10,32 +10,51 @@ module Fetch(
        input stall,
        input jmp,
        input [31:0] jmppc,
-       output wire bubble,
-       output wire [31:0] insn,
-       output reg [31:0] pc);
-
-       reg [31:0] prevpc;
-       initial
-               prevpc = 32'hFFFFFFFC;  /* ugh... the first pc we request will be this +4 */
-       always @(negedge Nrst)
-               prevpc <= 32'hFFFFFFFC;
+       output reg bubble = 1,
+       output reg [31:0] insn = 0,
+       output reg [31:0] pc = 32'hFFFFFFFC);
+       
+       reg qjmp = 0;   /* A jump has been queued up while we were waiting. */
+       reg [31:0] qjmppc;
+       always @(posedge clk)
+               if ((rd_wait || stall) && jmp && !qjmp)
+                       {qjmp,qjmppc} <= {jmp, jmppc};
+               else if (!rd_wait && !stall && qjmp)    /* It has already been intoed. */
+                       {qjmp,qjmppc} <= {1'b0, 32'hxxxxxxxx};
        
+       reg [31:0] reqpc;
        always @(*)
-               if (!Nrst)
-                       pc = 32'hFFFFFFFC;
-               else if (stall) /* don't change any internal state */
-                       pc = prevpc;
+               if (stall)
+                       reqpc = pc;
+               else if (qjmp)
+                       reqpc = qjmppc;
                else if (jmp)
-                       pc = jmppc;
+                       reqpc = jmppc;
                else
-                       pc = prevpc + 32'h4;
+                       reqpc = pc + 4;
+       
+       assign rd_addr = reqpc;
+       assign rd_req = 1;
+       
+       always @(negedge Nrst)
+       begin
+               pc <= 32'hFFFFFFFC;
+               qjmp <= 0;
+               bubble <= 1;
+       end
        
-       assign bubble = stall | rd_wait;
-       assign rd_addr = pc;
-       assign rd_req = !stall;
-       assign insn = rd_data;
-                       
        always @(posedge clk)
-               if (!rd_wait || !Nrst)
-                       prevpc <= pc;
+       begin
+               if (!Nrst) begin
+                       pc <= 32'hFFFFFFFC;
+                       qjmp <= 0;
+                       bubble <= 1;
+               end else if (!stall)
+               begin
+                       bubble <= rd_wait;
+                       insn <= rd_data;
+                       if (!rd_wait)
+                               pc <= reqpc;
+               end
+       end
 endmodule