Implements stage 5

bench/addi.s

@@ -0,0 +1,18 @@
+# expected: dead0000, dead0001, fffff800, ffffffff, 00000000
+    .text
+_start:
+    lui x2, 0xdead0
+    lui x3, 0x0
+
+    # Add 0
+    addi x31, x2, 0x0
+
+    # Basic addition
+    addi x31, x2, 0x1
+
+    # Sign extension
+    addi x31, x3, -2048
+    addi x31, x3, -1
+
+    # Overflow
+    addi x31, x31, 0x1