From 2c528314ebe29a1c94b6c03fd1b0e2668ee25dff Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Sat, 5 Sep 2020 17:58:56 +0200
Subject: add div instruction together with bench

---
 design/stack_machine.v | 49 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

(limited to 'design')

diff --git a/design/stack_machine.v b/design/stack_machine.v
index 0ccc1c6..4313713 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -208,10 +208,43 @@ module stack_machine_new
    assign instr_sub = !set_im && !use_im && stack_shrinks_by_1 &&
 		      instruction[11:0] == 12'd1;
 
+   wire 	      instr_udiv;
+   assign instr_udiv = !set_im && !use_im && stack_shrinks_by_1 &&
+		       instruction[11:0] == 12'd2;
+
 
    reg 		      halt; /* Set once a halt instruction is encountered */
    assign finished = halt;
 
+
+   /* module for division */
+   wire [31:0] 	      div_quotient;
+   wire [31:0] 	      div_remainder;
+   wire 	      div_done;
+
+   div
+     #(
+       .WIDTH(32)
+       ) div
+   (
+    .clock(CLK_I),
+    .start(step == STEP_EXECUTING && first_execution_tick),
+    .dividend(r0),
+    .divisor(r1),
+
+    .quotient(div_quotient),
+    .remainder(div_remainder),
+    .done(div_done)
+    );
+
+
+   reg 		      arithmetic_uncompleted;
+   wire 	      arithmetic_completes;
+   assign arithmetic_completes = instr_udiv ? div_done :
+				 instr_halt ? 0 :
+				 1;
+
+
    always @*
      I_ADR_O = pc / 2;
 
@@ -284,6 +317,8 @@ module stack_machine_new
 		 I_CYC_O <= 0;
 	      end
 
+	      arithmetic_uncompleted <= 1;
+
 	      first_execution_tick <= 1;
 	      load_store_unrequested <= 0;
 	      stack_transfer_unrequested <= 2'b0;
@@ -293,12 +328,17 @@ module stack_machine_new
 	   STEP_EXECUTING : begin
 	      first_execution_tick <= 0;
 
+	      if (arithmetic_completes)
+		arithmetic_uncompleted <= 0;
+
 	      if (((stack_grows || stack_shrinks || load || store) &&
 		   first_execution_tick) ||
 		  (load_store_uncompleted &&
 		   !data_command_completes) ||
 		  (stack_transfer_uncompleted[1] &&
-		   !stack_transfer_completes[1]) || halt) begin
+		   !stack_transfer_completes[1]) ||
+		  (arithmetic_uncompleted &&
+		   !arithmetic_completes)) begin
 		 step <= STEP_EXECUTING; /* Remain where we are */
 	      end else begin
 		 step <= STEP_LOADING_INSTRUCTION;
@@ -457,11 +497,14 @@ module stack_machine_new
 		r1 <= im_effective;
 
 	      /* Instructions, that shrink stack */
-	      if (instr_add && first_execution_tick)
+	      if (instr_add && arithmetic_uncompleted)
 		r1 <= r0 + r1;
 
-	      if (instr_sub && first_execution_tick)
+	      if (instr_sub && arithmetic_uncompleted)
 		r1 <= r0 - r1;
+
+	      if (instr_udiv && arithmetic_uncompleted)
+		r1 <= div_quotient;
 	   end // case: STEP_EXECUTING
 	 endcase // case (step)
       end // else: !if(RST_I)
-- 
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