Track InstructionData member names.

Entity references in instruction format operands also have member names
in the InstructionData struct. Track them the same way we track immediate operand member names.

Value operands still go in the arg / args members.

meta/cretonne/__init__.py

@@ -293,6 +293,7 @@ class OperandKind(object):
     def __init__(self, name, doc):
         self.name = name
         self.__doc__ = doc
+        self.default_member = None
         # The camel-cased name of an operand kind is also the Rust type used to
         # represent it.
         self.camel_name = camel_case(name)
@@ -347,8 +348,7 @@ class ImmediateKind(OperandKind):
     """
 
     def __init__(self, name, doc, default_member='imm'):
-        self.name = name
-        self.__doc__ = doc
+        super(ImmediateKind, self).__init__(name, doc)
         self.default_member = default_member
 
     def __repr__(self):
@@ -362,9 +362,9 @@ class EntityRefKind(OperandKind):
     The kind of an entity reference instruction operand.
     """
 
-    def __init__(self, name, doc):
-        self.name = name
-        self.__doc__ = doc
+    def __init__(self, name, doc, default_member=None):
+        super(EntityRefKind, self).__init__(name, doc)
+        self.default_member = default_member or name
 
     def __repr__(self):
         return 'EntityRefKind({})'.format(self.name)
@@ -686,17 +686,17 @@ class InstructionFormat(object):
 
         Yields the operand kinds.
         """
+        self.members = list()
         for i, k in enumerate(kinds):
             if isinstance(k, tuple):
                 member, k = k
             else:
-                member = None
+                member = k.default_member
             yield k
+            self.members.append(member)
 
             # Create `FormatField` instances for the immediates.
             if isinstance(k, ImmediateKind):
-                if not member:
-                    member = k.default_member
                 assert not hasattr(self, member), "Duplicate member name"
                 field = FormatField(self, i, member)
                 setattr(self, member, field)