Add PC tracing capability

This adds the --trace_pc option to dump the PC after each instruction to a file
called trace.bin

bench/servant_sim.v

@@ -1,8 +1,10 @@
 `default_nettype none
 module servant_sim
-  (input wire  wb_clk,
-   input wire  wb_rst,
-   output wire q);
+  (input wire	      wb_clk,
+   input wire	      wb_rst,
+   output wire [31:0] pc_adr,
+   output wire	      pc_vld,
+   output wire	      q);
 
    parameter memfile = "";
    parameter memsize = 8192;
@@ -26,4 +28,7 @@ module servant_sim
        .align    (align[0:0]))
    dut(wb_clk, wb_rst, q);
 
+   assign pc_adr = dut.wb_ibus_adr;
+   assign pc_vld = dut.wb_ibus_ack;
+
 endmodule

bench/servant_tb.cpp

@@ -1,3 +1,4 @@
+#include <fcntl.h>
 #include <stdint.h>
 #include <signal.h>
 
@@ -110,6 +111,11 @@ int main(int argc, char **argv, char **env)
 
   signal(SIGINT, INThandler);
 
+  int tf = 0;
+  const char *arg_trace_pc = Verilated::commandArgsPlusMatch("trace_pc=");
+  if (arg_trace_pc[0])
+    tf = open("trace.bin", O_WRONLY | O_CREAT | O_TRUNC, S_IRWXU);
+
   vluint64_t timeout = 0;
   const char *arg_timeout = Verilated::commandArgsPlusMatch("timeout=");
   if (arg_timeout[0])
@@ -137,6 +143,8 @@ int main(int argc, char **argv, char **env)
     } else {
       do_gpio(&gpio_context, top->q);
     }
+    if (tf && top->wb_clk && top->pc_vld)
+      write(tf, (void *)&top->pc_adr, 4);
     if (timeout && (main_time >= timeout)) {
       printf("Timeout: Exiting at time %lu\n", main_time);
       done = true;
@@ -146,6 +154,7 @@ int main(int argc, char **argv, char **env)
     main_time+=31.25;
 
   }
+  close(tf);
   if (tfp)
     tfp->close();
   exit(0);

bench/servant_tb.v

@@ -21,6 +21,11 @@ module servant_tb;
      #(.memfile  (memfile),
        .memsize  (memsize),
        .with_csr (with_csr))
-   dut(wb_clk, wb_rst, q);
+   dut
+     (.wb_clk (wb_clk),
+      .wb_rst (wb_rst),
+      .pc_adr (),
+      .pc_vld (),
+      .q      (q));
 
 endmodule

servant.core

@@ -512,6 +512,7 @@ targets:
       - memsize
       - signature
       - timeout
+      - trace_pc
       - uart_baudrate
       - vcd
       - vcd_start
@@ -587,6 +588,10 @@ parameters:
     datatype : int
     paramtype : plusarg
 
+  trace_pc:
+    datatype : bool
+    paramtype : plusarg
+
   uart_baudrate:
     datatype : int
     description : Treat q output as an UART with the specified baudrate (0 or omitted parameter disables UART decoding)