add add instruction together with bench

1 files changed, 21 insertions, 7 deletions

diff --git a/design/stack_machine.v b/design/stack_machine.v
index 04b1285..d79a136 100644
--- a/design/stack_machine.v
+++ b/design/stack_machine.v
@@ -118,6 +118,9 @@ module stack_machine_new
    wire 	      stack_shrinks;
    assign stack_shrinks = instruction[13] == 1'b1 && !set_im;
 
+   wire 	      stack_shrinks_by_1;
+   assign stack_shrinks_by_1 = stack_shrinks && instruction[12] == 1'b1;
+
    wire 	      stack_shrinks_by_2;
    assign stack_shrinks_by_2 = stack_shrinks && instruction[12] == 1'b0;
 
@@ -193,7 +196,9 @@ module stack_machine_new
 			instruction[11:7] == 5'd0;
 
    /* Instructions, that shrink stack */
-   /* none now */
+   wire 	      instr_add;
+   assign instr_add = !set_im && !use_im && stack_shrinks_by_1 &&
+		      instruction[11:0] == 12'd0;
 
    reg 		      halt; /* Set once a halt instruction is encountered */
    assign finished = halt;
@@ -279,9 +284,6 @@ module stack_machine_new
 	   STEP_EXECUTING : begin
 	      first_execution_tick <= 0;
 
-	      if (instr_halt)
-		halt <= 1;
-
 	      if (((stack_grows || stack_shrinks || load || store) &&
 		   first_execution_tick) ||
 		  (load_store_uncompleted &&
@@ -425,14 +427,26 @@ module stack_machine_new
 	      else
 		im <= 32'bx;
 
-	      if (instr_const && first_execution_tick)
-		r1 <= im_effective;
+	      /* Instructions, that do not change stack size */
+	      if (instr_halt)
+		halt <= 1;
 
-	      if (instr_tee)
+	      if (instr_nop)
 		r1 <= r1;
 
 	      if (instr_set_sp)
 		`SET_SP(im_effective);
+
+	      /* Instructions, that grow stack */
+	      if (instr_tee)
+		r1 <= r1;
+
+	      if (instr_const && first_execution_tick)
+		r1 <= im_effective;
+
+	      /* Instructions, that shrink stack */
+	      if (instr_add && first_execution_tick)
+		r1 <= r1 + r0;
 	   end // case: STEP_EXECUTING
 	 endcase // case (step)
       end // else: !if(RST_I)