From d5c877247834fc25689ca6cf7530cd8d1b870d3a Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Sat, 5 Sep 2020 17:20:38 +0200
Subject: add swap instruction together with bench

---
 Makefile                                     |  1 +
 design/stack_machine.v                       |  7 +++++++
 tclasm.tcl                                   |  5 +++++
 tests/stack_machine_swap/instructions.s.tcl  | 17 +++++++++++++++++
 tests/stack_machine_swap/test.v              |  1 +
 tests/stack_machine_swap/words_to_verify.mem |  3 +++
 6 files changed, 34 insertions(+)
 create mode 100755 tests/stack_machine_swap/instructions.s.tcl
 create mode 120000 tests/stack_machine_swap/test.v
 create mode 100644 tests/stack_machine_swap/words_to_verify.mem

diff --git a/Makefile b/Makefile
index c0c2a17..dfeb4f9 100644
--- a/Makefile
+++ b/Makefile
@@ -37,6 +37,7 @@ STACK_MACHINE_TESTS := \
 	load_store \
 	multiinstructions_load_store \
 	tee \
+	swap \
 	add \
 	sub
 
diff --git a/design/stack_machine.v b/design/stack_machine.v
index 868a103..0ccc1c6 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -182,6 +182,10 @@ module stack_machine_new
    assign instr_nop = !set_im && !use_im && stack_same_size &&
 		      instruction[11:0] == 12'd1;
 
+   wire 	      instr_swap;
+   assign instr_swap = !set_im && !use_im && stack_same_size &&
+		      instruction[11:0] == 12'd2;
+
    wire 	      instr_set_sp;
    assign instr_set_sp = use_im && stack_same_size &&
 			 instruction[11:7] == 5'd0;
@@ -439,6 +443,9 @@ module stack_machine_new
 	      if (instr_nop)
 		r1 <= r1;
 
+	      if (instr_swap)
+		{r0, r1} <= {r1, r0};
+
 	      if (instr_set_sp)
 		`SET_SP(im_effective);
 
diff --git a/tclasm.tcl b/tclasm.tcl
index c86a3e7..ed4ed8d 100644
--- a/tclasm.tcl
+++ b/tclasm.tcl
@@ -154,3 +154,8 @@ proc set_sp {address} {
 proc halt {} {
     puts 0000000000000000
 }
+
+
+proc swap {} {
+    puts 0000000000000010
+}
diff --git a/tests/stack_machine_swap/instructions.s.tcl b/tests/stack_machine_swap/instructions.s.tcl
new file mode 100755
index 0000000..a44ecf9
--- /dev/null
+++ b/tests/stack_machine_swap/instructions.s.tcl
@@ -0,0 +1,17 @@
+#!/usr/bin/env tclsh
+
+source tclasm.tcl
+
+set_sp 0
+
+const h0000DEAD
+const h0000BEEF
+
+swap
+
+## Because values were swapped, h0000DEAD should get written, first, at lower
+## address (h100) and h0000BEEF should be written next (at h200)
+store h000100
+store h000200
+
+halt
diff --git a/tests/stack_machine_swap/test.v b/tests/stack_machine_swap/test.v
new file mode 120000
index 0000000..f5b6a59
--- /dev/null
+++ b/tests/stack_machine_swap/test.v
@@ -0,0 +1 @@
+../stack_machine_store/test.v
\ No newline at end of file
diff --git a/tests/stack_machine_swap/words_to_verify.mem b/tests/stack_machine_swap/words_to_verify.mem
new file mode 100644
index 0000000..8557c9a
--- /dev/null
+++ b/tests/stack_machine_swap/words_to_verify.mem
@@ -0,0 +1,3 @@
+// address  value
+   00100    DEAD
+   00200    BEEF
-- 
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