diff --git a/lib/opcodes.py b/lib/opcodes.py
index 8bf6c778e5d3bc6d671ff742a445bab855178157..74ebe9c5f0720a5a55e33c0d68385550bbec3d99 100644
--- a/lib/opcodes.py
+++ b/lib/opcodes.py
@@ -245,17 +245,16 @@ DEPEND_ATTR = "depends"
 COMMENT_ATTR = "comment"
 
 
-def _NameToId(name):
-  """Convert an opcode class name to an OP_ID.
+def _NameComponents(name):
+  """Split an opcode class name into its components
 
   @type name: string
   @param name: the class name, as OpXxxYyy
-  @rtype: string
-  @return: the name in the OP_XXXX_YYYY format
+  @rtype: array of strings
+  @return: the components of the name
 
   """
-  if not name.startswith("Op"):
-    return None
+  assert name.startswith("Op")
   # Note: (?<=[a-z])(?=[A-Z]) would be ideal, since it wouldn't
   # consume any input, and hence we would just have all the elements
   # in the list, one by one; but it seems that split doesn't work on
@@ -263,7 +262,36 @@ def _NameToId(name):
   # bit
   name = _OPID_RE.sub(r"\1,\2", name)
   elems = name.split(",")
-  return "_".join(n.upper() for n in elems)
+  return elems
+
+
+def _NameToId(name):
+  """Convert an opcode class name to an OP_ID.
+
+  @type name: string
+  @param name: the class name, as OpXxxYyy
+  @rtype: string
+  @return: the name in the OP_XXXX_YYYY format
+
+  """
+  if not name.startswith("Op"):
+    return None
+  return "_".join(n.upper() for n in _NameComponents(name))
+
+
+def NameToReasonSrc(name):
+  """Convert an opcode class name to a source string for the reason trail
+
+  @type name: string
+  @param name: the class name, as OpXxxYyy
+  @rtype: string
+  @return: the name in the OP_XXXX_YYYY format
+
+  """
+  if not name.startswith("Op"):
+    return None
+  return "%s:%s" % (constants.OPCODE_REASON_SRC_OPCODE,
+                    "_".join(n.lower() for n in _NameComponents(name)))
 
 
 def _GenerateObjectTypeCheck(obj, fields_types):