Add counter module and simplify board design for shift instructions.

1 files changed, 2 insertions, 2 deletions

diff --git a/sim/alu.sv b/sim/alu.sv
index 407b083..5583492 100644
--- a/sim/alu.sv
+++ b/sim/alu.sv
@@ -49,8 +49,8 @@ assign cmp_result = {{(BUS_BITS-6){1'b0}},
     abus > dbus,
     abus == dbus,
     abus < dbus};
-assign lshift_result = (dbus >= BUS_BITS) ? 0 : (abus << dbus);
-assign rshift_result = (dbus >= BUS_BITS) ? 0 : (abus >> dbus);
+assign lshift_result = {dbus[BUS_BITS-2:0], abus[0]};
+assign rshift_result = {abus[BUS_BITS-1], dbus[BUS_BITS-1:1]};
 
 bit [BUS_BITS-1:0] newx;
 assign newx =