From ba4d97ddc2133c905e668c2f916cf3b14be4e35d Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Sat, 5 Sep 2020 17:09:16 +0200
Subject: add sub instruction together with bench

---
 Makefile                                    |  3 ++-
 design/stack_machine.v                      | 10 +++++++++-
 tclasm.tcl                                  |  5 +++++
 tests/stack_machine_sub/instructions.s.tcl  | 24 ++++++++++++++++++++++++
 tests/stack_machine_sub/test.v              |  1 +
 tests/stack_machine_sub/words_to_verify.mem |  6 ++++++
 6 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100755 tests/stack_machine_sub/instructions.s.tcl
 create mode 120000 tests/stack_machine_sub/test.v
 create mode 100644 tests/stack_machine_sub/words_to_verify.mem

diff --git a/Makefile b/Makefile
index 6f2227f..c0c2a17 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,8 @@ STACK_MACHINE_TESTS := \
 	load_store \
 	multiinstructions_load_store \
 	tee \
-	add
+	add \
+	sub
 
 # Add other tests here if You need
 TESTS := \
diff --git a/design/stack_machine.v b/design/stack_machine.v
index d79a136..868a103 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -200,6 +200,11 @@ module stack_machine_new
    assign instr_add = !set_im && !use_im && stack_shrinks_by_1 &&
 		      instruction[11:0] == 12'd0;
 
+   wire 	      instr_sub;
+   assign instr_sub = !set_im && !use_im && stack_shrinks_by_1 &&
+		      instruction[11:0] == 12'd1;
+
+
    reg 		      halt; /* Set once a halt instruction is encountered */
    assign finished = halt;
 
@@ -446,7 +451,10 @@ module stack_machine_new
 
 	      /* Instructions, that shrink stack */
 	      if (instr_add && first_execution_tick)
-		r1 <= r1 + r0;
+		r1 <= r0 + r1;
+
+	      if (instr_sub && first_execution_tick)
+		r1 <= r0 - r1;
 	   end // case: STEP_EXECUTING
 	 endcase // case (step)
       end // else: !if(RST_I)
diff --git a/tclasm.tcl b/tclasm.tcl
index f5646a2..c86a3e7 100644
--- a/tclasm.tcl
+++ b/tclasm.tcl
@@ -101,6 +101,11 @@ proc add {} {
 }
 
 
+proc sub {} {
+    puts 0011000000000001
+}
+
+
 proc _store {address_part} {
     puts 011111100[__to_binary $address_part 7]
 }
diff --git a/tests/stack_machine_sub/instructions.s.tcl b/tests/stack_machine_sub/instructions.s.tcl
new file mode 100755
index 0000000..e8485ee
--- /dev/null
+++ b/tests/stack_machine_sub/instructions.s.tcl
@@ -0,0 +1,24 @@
+#!/usr/bin/env tclsh
+
+source tclasm.tcl
+
+### store 2 values to memory, load them back,
+### substract them and store the result
+
+set_sp 0
+
+const 68996288
+store h1EEE0
+const 540904416
+store h1EEE4
+
+const 8
+
+load h1EEE0
+load h1EEE4
+# substracting 540904416 from 68996288 should yield -471908128
+sub
+# will write to h1EEE0 + 8 = h1EEE8
+store+ h1EEE0
+
+halt
diff --git a/tests/stack_machine_sub/test.v b/tests/stack_machine_sub/test.v
new file mode 120000
index 0000000..f5b6a59
--- /dev/null
+++ b/tests/stack_machine_sub/test.v
@@ -0,0 +1 @@
+../stack_machine_store/test.v
\ No newline at end of file
diff --git a/tests/stack_machine_sub/words_to_verify.mem b/tests/stack_machine_sub/words_to_verify.mem
new file mode 100644
index 0000000..10c15db
--- /dev/null
+++ b/tests/stack_machine_sub/words_to_verify.mem
@@ -0,0 +1,6 @@
+// address  value
+   1EEE0    41CCCC0  // 68996288 in hex is 41CCCC0
+
+   1EEE4    203D8BE0  // 540904416 in hex is 203D8BE0
+
+   1EEE8    E3DF40E0  // -471908128 in hex is E3DF40E0
-- 
cgit v1.2.3