diff --git a/scripts/update_asm_instructions.py b/scripts/update_asm_instructions.py
index 5ac2244..6748f62 100755
--- a/scripts/update_asm_instructions.py
+++ b/scripts/update_asm_instructions.py
@@ -37,6 +37,15 @@ re_lookup = re.compile(
     r"(/\* @AUTOGEN_LOOKUP_BLOCK_START \*/\n*)(.*?)"
     r"(\n*/\* @AUTOGEN_LOOKUP_BLOCK_END \*/)", re.S)
 
+def _atoi(value):
+    """
+    Try to convert a string to an integer, supporting decimal and hexadecimal.
+    """
+    try:
+        return int(value)
+    except ValueError:
+        return int(value, 16)
+
 class Instruction(object):
     """
     Represent a single ASM instruction mnemonic.
@@ -56,7 +65,9 @@ class Instruction(object):
     def __init__(self, name, data):
         self._name = name
         self._data = data
+
         self._has_optional_args = False
+        self._step_state = {}
 
     def _get_arg_parse_mask(self, num):
         """
@@ -113,16 +124,12 @@ class Instruction(object):
         """
         if "." in cond:
             itype, value = cond.split(".", 1)
-            try:
-                value = int(value)
-            except ValueError:
-                value = int(value, 16)
             vtype = "sval" if itype.upper() in ["S8", "REL"] else "uval"
 
             test1 = "INST_IMM({0}).mask & IMM_{1}".format(num, itype.upper())
             if (itype.upper() == "U16"):
                 test1 += " && !INST_IMM({0}).is_label".format(num)
-            test2 = "INST_IMM({0}).{1} == {2}".format(num, vtype, value)
+            test2 = "INST_IMM({0}).{1} == {2}".format(num, vtype, _atoi(value))
             return "({0} && {1})".format(test1, test2)
 
         return "INST_IMM({0}).mask & IMM_{1}".format(num, cond.upper())
@@ -253,8 +260,19 @@ class Instruction(object):
 
                 elif byte.startswith("bit(") and byte.endswith(")"):
                     index = types.index("immediate")
-                    off = byte[4:-1]
-                    ret[i] = "{0} + 8 * INST_IMM({1}).uval".format(off, index)
+                    base = byte[4:-1]
+                    ret[i] = "{0} + 8 * INST_IMM({1}).uval".format(base, index)
+
+                elif byte.startswith("step(") and byte.endswith(")"):
+                    arg = byte[5:-1]
+                    if " " in arg:
+                        base, stride = map(_atoi, arg.split(" "))
+                    else:
+                        base, stride = _atoi(arg), 1
+                    if base not in self._step_state:
+                        self._step_state[base] = 0
+                    ret[i] = base + self._step_state[base] * stride
+                    self._step_state[base] += 1
 
                 else:
                     msg = "Unsupported return byte: {0}"
diff --git a/src/assembler/instructions.inc.c b/src/assembler/instructions.inc.c
index 5769fa9..e602d59 100644
--- a/src/assembler/instructions.inc.c
+++ b/src/assembler/instructions.inc.c
@@ -7,7 +7,7 @@
     `make` should trigger a rebuild when it is modified; if not, use:
     `python scripts/update_asm_instructions.py`.
 
-    @AUTOGEN_DATE Thu May 21 20:33:21 2015 UTC
+    @AUTOGEN_DATE Thu May 21 21:05:17 2015 UTC
 */
 
 /* @AUTOGEN_INST_BLOCK_START */
diff --git a/src/assembler/instructions.yml b/src/assembler/instructions.yml
index a324c3e..547f31d 100644
--- a/src/assembler/instructions.yml
+++ b/src/assembler/instructions.yml
@@ -17,26 +17,14 @@ adc:
           cases:
             - cond:   [a, a]
               return: [0x8F]
-            - cond:   [a, b]
-              return: [0x88]
-            - cond:   [a, c]
-              return: [0x89]
-            - cond:   [a, d]
-              return: [0x8A]
-            - cond:   [a, e]
-              return: [0x8B]
+            - cond:   [a, b|c|d|e]
+              return: [step(0x88)]
             - cond:   [a, h|ih]
               return: [0x8C]
             - cond:   [a, l|il]
               return: [0x8D]
-            - cond:   [hl, bc]
-              return: [0xED, 0x4A]
-            - cond:   [hl, de]
-              return: [0xED, 0x5A]
-            - cond:   [hl, hl]
-              return: [0xED, 0x6A]
-            - cond:   [hl, sp]
-              return: [0xED, 0x7A]
+            - cond:   [hl, bc|de|hl|sp]
+              return: [0xED, step(0x4A 0x10)]
         - type: [register, immediate]
           cases:
             - cond:   [a, u8]
@@ -53,14 +41,8 @@ add:
           cases:
             - cond:   [a, a]
               return: [0x87]
-            - cond:   [a, b]
-              return: [0x80]
-            - cond:   [a, c]
-              return: [0x81]
-            - cond:   [a, d]
-              return: [0x82]
-            - cond:   [a, e]
-              return: [0x83]
+            - cond:   [a, b|c|d|e]
+              return: [step(0x80)]
             - cond:   [a, h|ih]
               return: [0x84]
             - cond:   [a, l|il]
@@ -89,14 +71,8 @@ and:
           cases:
             - cond:   [a]
               return: [0xA7]
-            - cond:   [b]
-              return: [0xA0]
-            - cond:   [c]
-              return: [0xA1]
-            - cond:   [d]
-              return: [0xA2]
-            - cond:   [e]
-              return: [0xA3]
+            - cond:   [b|c|d|e]
+              return: [step(0xA0)]
             - cond:   [h|ih]
               return: [0xA4]
             - cond:   [l|il]
@@ -411,14 +387,8 @@ jr:
               return: [0x18, rel]
         - type: [condition, immediate]
           cases:
-            - cond:   [nz, rel]
-              return: [0x20, rel]
-            - cond:   [z, rel]
-              return: [0x28, rel]
-            - cond:   [nc, rel]
-              return: [0x30, rel]
-            - cond:   [c, rel]
-              return: [0x38, rel]
+            - cond:   [nz|z|nc|c, rel]
+              return: [step(0x20 0x08), rel]
 
 ld:
     args: yes