From a0e9d28f2a21cc42dff7ed2fce3e52cb04bc5170 Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Mon, 23 Nov 2020 11:22:19 +0100
Subject: add unsigned division remainder instruction

---
 design/stack_machine.v                      | 10 +++++++++-
 tclasm.tcl                                  |  4 ++++
 tests/stack_machine_rem/Makefile            |  1 +
 tests/stack_machine_rem/instructions.s.tcl  | 17 +++++++++++++++++
 tests/stack_machine_rem/test.v              |  1 +
 tests/stack_machine_rem/words_to_verify.mem |  6 ++++++
 6 files changed, 38 insertions(+), 1 deletion(-)
 create mode 120000 tests/stack_machine_rem/Makefile
 create mode 100644 tests/stack_machine_rem/instructions.s.tcl
 create mode 120000 tests/stack_machine_rem/test.v
 create mode 100644 tests/stack_machine_rem/words_to_verify.mem

diff --git a/design/stack_machine.v b/design/stack_machine.v
index f68421e..13e55c1 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -286,6 +286,10 @@ module stack_machine_new
    assign instr_uge = !set_im && !use_im && stack_shrinks_by_1 &&
 		       instruction[11:0] == 12'd15;
 
+   wire 	      instr_urem;
+   assign instr_urem = !set_im && !use_im && stack_shrinks_by_1 &&
+		       instruction[11:0] == 12'd16;
+
    wire 	      instr_ret;
    assign instr_ret = !set_im && !use_im && stack_shrinks_by_1 &&
 		      instruction[11:0] == 12'b000010000000;
@@ -326,7 +330,7 @@ module stack_machine_new
 
    reg 		      arithmetic_uncompleted;
    wire 	      arithmetic_completes;
-   assign arithmetic_completes = instr_udiv ? div_done :
+   assign arithmetic_completes = instr_udiv || instr_urem ? div_done :
 				 instr_halt ? 0 :
 				 1;
 
@@ -611,6 +615,9 @@ module stack_machine_new
 	      if (instr_udiv && arithmetic_uncompleted)
 		r1 <= div_quotient;
 
+	      if (instr_urem && arithmetic_uncompleted)
+		r1 <= div_remainder;
+
 	      if (instr_mul && arithmetic_uncompleted)
 		r1 <= r0 * r1;
 
@@ -687,6 +694,7 @@ module stack_machine_new
 		       instr_ugt         ? "ugt" :
 		       instr_ge          ? "ge" :
 		       instr_uge         ? "uge" :
+		       instr_urem        ? "urem" :
 		       instr_ret         ? "ret" :
 		       instr_cond_jump   ? "cond_jump" :
 		       instr_cond_jump_n ? "cond_jump_n" :
diff --git a/tclasm.tcl b/tclasm.tcl
index 90adda5..3fa53d2 100755
--- a/tclasm.tcl
+++ b/tclasm.tcl
@@ -376,6 +376,10 @@ proc uge {} {
     puts 0011000000001111
 }
 
+proc rem {} {
+    puts 0011000000010000
+}
+
 
 proc ret {} {
     puts 0011000010000000
diff --git a/tests/stack_machine_rem/Makefile b/tests/stack_machine_rem/Makefile
new file mode 120000
index 0000000..2c3c770
--- /dev/null
+++ b/tests/stack_machine_rem/Makefile
@@ -0,0 +1 @@
+../stack_machine_store/Makefile
\ No newline at end of file
diff --git a/tests/stack_machine_rem/instructions.s.tcl b/tests/stack_machine_rem/instructions.s.tcl
new file mode 100644
index 0000000..1376d51
--- /dev/null
+++ b/tests/stack_machine_rem/instructions.s.tcl
@@ -0,0 +1,17 @@
+### store 2 values to memory, load them back, divide one by another and store
+### the result (remainder); 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
+rem
+store h1EEE8
+
+halt
diff --git a/tests/stack_machine_rem/test.v b/tests/stack_machine_rem/test.v
new file mode 120000
index 0000000..f5b6a59
--- /dev/null
+++ b/tests/stack_machine_rem/test.v
@@ -0,0 +1 @@
+../stack_machine_store/test.v
\ No newline at end of file
diff --git a/tests/stack_machine_rem/words_to_verify.mem b/tests/stack_machine_rem/words_to_verify.mem
new file mode 100644
index 0000000..c11e8b5
--- /dev/null
+++ b/tests/stack_machine_rem/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    E63  // 3683 in hex is E63
-- 
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