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

---
 Makefile                                    |  5 +--
 design/stack_machine.v                      | 49 +++++++++++++++++++++++++++--
 tclasm.tcl                                  |  5 +++
 tests/stack_machine_div/instructions.s.tcl  | 21 +++++++++++++
 tests/stack_machine_div/test.v              |  1 +
 tests/stack_machine_div/words_to_verify.mem |  6 ++++
 6 files changed, 82 insertions(+), 5 deletions(-)
 create mode 100755 tests/stack_machine_div/instructions.s.tcl
 create mode 120000 tests/stack_machine_div/test.v
 create mode 100644 tests/stack_machine_div/words_to_verify.mem

diff --git a/Makefile b/Makefile
index dfeb4f9..c7ab240 100644
--- a/Makefile
+++ b/Makefile
@@ -39,7 +39,8 @@ STACK_MACHINE_TESTS := \
 	tee \
 	swap \
 	add \
-	sub
+	sub \
+	div
 
 # Add other tests here if You need
 TESTS := \
@@ -168,7 +169,7 @@ tests/stack_machine_%/test.vvp : \
 		tests/stack_machine_%/words_to_verify.mem \
 		tests/stack_machine_%/instructions.mem \
 		tests/stack_machine_%/test.v models/slave.v \
-		design/stack_machine.v include/messages.vh
+		design/stack_machine.v design/div.v include/messages.vh
 	$(IV) $(IVFLAGS) -s stack_machine_test \
 		-DINSTRUCTIONS_COUNT=$(call FILE_LINES,$(filter %ions.mem,$^)) \
 		-DWORDS_TO_VERIFY_COUNT=$(call FILE_LINES,$<) \
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)
diff --git a/tclasm.tcl b/tclasm.tcl
index 17aa8aa..4293441 100644
--- a/tclasm.tcl
+++ b/tclasm.tcl
@@ -176,3 +176,8 @@ proc add {} {
 proc sub {} {
     puts 0011000000000001
 }
+
+
+proc div {} {
+    puts 0011000000000010
+}
diff --git a/tests/stack_machine_div/instructions.s.tcl b/tests/stack_machine_div/instructions.s.tcl
new file mode 100755
index 0000000..7f09f20
--- /dev/null
+++ b/tests/stack_machine_div/instructions.s.tcl
@@ -0,0 +1,21 @@
+#!/usr/bin/env tclsh
+
+source tclasm.tcl
+
+### store 2 values to memory, load them back, divide one by another and store
+### the result (quotient); this is analogous to addition and substraction tests
+
+set_sp 0
+
+const 777681520
+store h1EEE0
+const 3721
+store h1EEE4
+
+load h1EEE0
+load h1EEE4
+# dividing 777681520 by 3721 should yield 208997 r 3683
+div
+store h1EEE8
+
+halt
diff --git a/tests/stack_machine_div/test.v b/tests/stack_machine_div/test.v
new file mode 120000
index 0000000..f5b6a59
--- /dev/null
+++ b/tests/stack_machine_div/test.v
@@ -0,0 +1 @@
+../stack_machine_store/test.v
\ No newline at end of file
diff --git a/tests/stack_machine_div/words_to_verify.mem b/tests/stack_machine_div/words_to_verify.mem
new file mode 100644
index 0000000..2e6c6fa
--- /dev/null
+++ b/tests/stack_machine_div/words_to_verify.mem
@@ -0,0 +1,6 @@
+// address  value
+   1EEE0    2E5A7A70  // 777681520 in hex is 2E5A7A70
+
+   1EEE4    E89  // 3721 in hex is E89
+
+   1EEE8    33065  // 208997 in hex is 33065
-- 
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