From 92206c93690c5658928c9f8b1324e1a455e1a453 Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Sat, 5 Sep 2020 18:57:00 +0200
Subject: add cond_jump instruction together with bench

---
 Makefile                                          |  3 +-
 design/stack_machine.v                            | 11 ++++++++
 tclasm.tcl                                        |  9 ++++++
 tests/stack_machine_cond_jump/instructions.s.tcl  | 34 +++++++++++++++++++++++
 tests/stack_machine_cond_jump/test.v              |  1 +
 tests/stack_machine_cond_jump/words_to_verify.mem |  6 ++++
 6 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100755 tests/stack_machine_cond_jump/instructions.s.tcl
 create mode 120000 tests/stack_machine_cond_jump/test.v
 create mode 100644 tests/stack_machine_cond_jump/words_to_verify.mem

diff --git a/Makefile b/Makefile
index 454b499..73a6aff 100644
--- a/Makefile
+++ b/Makefile
@@ -42,7 +42,8 @@ STACK_MACHINE_TESTS := \
 	sub \
 	div \
 	mul \
-	jump
+	jump \
+	cond_jump
 
 # Add other tests here if You need
 TESTS := \
diff --git a/design/stack_machine.v b/design/stack_machine.v
index 150f6c7..b6c2706 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -220,6 +220,10 @@ module stack_machine_new
    assign instr_mul = !set_im && !use_im && stack_shrinks_by_1 &&
 		      instruction[11:0] == 12'd3;
 
+   wire 	      instr_cond_jump;
+   assign instr_cond_jump = use_im && stack_shrinks_by_1 &&
+			    instruction[11:7] == 5'd1;
+
 
    reg 		      halt; /* Set once a halt instruction is encountered */
    assign finished = halt;
@@ -519,6 +523,13 @@ module stack_machine_new
 
 	      if (instr_mul && arithmetic_uncompleted)
 		r1 <= r0 * r1;
+
+	      if (instr_cond_jump && arithmetic_uncompleted) begin
+		 r1 <= r0;
+
+		 if (r1)
+		   `SET_PC(im_effective);
+	      end
 	   end // case: STEP_EXECUTING
 	 endcase // case (step)
       end // else: !if(RST_I)
diff --git a/tclasm.tcl b/tclasm.tcl
index 1f716ee..cafe99f 100644
--- a/tclasm.tcl
+++ b/tclasm.tcl
@@ -195,3 +195,12 @@ proc div {} {
 proc mul {} {
     puts 0011000000000011
 }
+
+
+proc _cond_jump {address_part} {
+    puts 011100001[__to_binary $address_part 7]
+}
+
+proc cond_jump {address} {
+    _with_im _cond_jump $address
+}
diff --git a/tests/stack_machine_cond_jump/instructions.s.tcl b/tests/stack_machine_cond_jump/instructions.s.tcl
new file mode 100755
index 0000000..d1d5809
--- /dev/null
+++ b/tests/stack_machine_cond_jump/instructions.s.tcl
@@ -0,0 +1,34 @@
+#!/usr/bin/env tclsh
+
+source tclasm.tcl
+
+## also look at stack_machine_jump test 
+
+## we're going to write numbers from 0 to 7 to addresses h400 - h41C
+
+# this will translate to 1 16-bit instruction
+set_sp 0
+
+## set up the counter (1 16-bit instruction)
+const 0
+
+## this is the point we later jump to, address 4
+tee
+tee
+## compute address:  counter * 4 + h400 and save counter to it
+const 4
+mul
+swap
+store+ h400
+
+## increase counter by 1
+const 1
+add
+## compare value of counter to 8
+tee
+const 8
+sub
+## loop if counter != 8
+cond_jump 4
+
+halt
diff --git a/tests/stack_machine_cond_jump/test.v b/tests/stack_machine_cond_jump/test.v
new file mode 120000
index 0000000..f5b6a59
--- /dev/null
+++ b/tests/stack_machine_cond_jump/test.v
@@ -0,0 +1 @@
+../stack_machine_store/test.v
\ No newline at end of file
diff --git a/tests/stack_machine_cond_jump/words_to_verify.mem b/tests/stack_machine_cond_jump/words_to_verify.mem
new file mode 100644
index 0000000..aa047b5
--- /dev/null
+++ b/tests/stack_machine_cond_jump/words_to_verify.mem
@@ -0,0 +1,6 @@
+// address  value
+   00400    0     // verify the first number written
+
+   00408    2     // verify a number in the middle
+
+   0041C    7     // verify the last number
-- 
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