Python InstructionFormat refactoring.

Make some changes that will make it easier to get rid of the
'value_operands' and 'members' fields in the Python InstructionFormat
class. This is necessary to be able to combine instruction formats that
all use a value list representation, but with different fixed value
operands. The goal is to eventually identify formats by a new signature:

   (multiple_results, imm_kinds, num_value_operands)

Start by adding new fields:

- imm_members and imm_kinds are lists describing the format operands,
  excluding any values and variable_args operands.
- num_value_operands is the number of fixed value operands, or None in a
  has_value-list format.

Use these new members in preference to the old ones where possible.

lib/cretonne/meta/cdsl/formats.py

@@ -57,16 +57,23 @@ class InstructionFormat(object):
         self.has_value_list = kwargs.get('value_list', False)
         self.boxed_storage = kwargs.get('boxed_storage', False)
         self.members = list()  # type: List[str]
+
+        # Struct member names for the immediate operands. All other instruction
+        # operands are values or variable argument lists. They are all handled
+        # specially.
+        self.imm_members = list()  # type: List[str]
+        # Operand kinds for the immediate operands.
+        self.imm_kinds = list()  # type: List[OperandKind]
+        # The number of value operands stored in the format, or `None` when
+        # `has_value_list` is set.
+        self.num_value_operands = 0
+
         self.kinds = tuple(self._process_member_names(kinds))
 
         # Which of self.kinds are `value`?
         self.value_operands = tuple(
                 i for i, k in enumerate(self.kinds) if k is VALUE)
 
-        # We require a value list for storage of variable arguments.
-        if VARIABLE_ARGS in self.kinds:
-            assert self.has_value_list, "Need a value list for variable args"
-
         # The typevar_operand argument must point to a 'value' operand.
         self.typevar_operand = kwargs.get('typevar_operand', None)  # type: int
         if self.typevar_operand is not None:
@@ -102,6 +109,17 @@ class InstructionFormat(object):
                 k = arg
             else:
                 member, k = arg
+
+            # We define 'immediate' as not a value or variable arguments.
+            if k is VALUE:
+                self.num_value_operands += 1
+            elif k is VARIABLE_ARGS:
+                # We require a value list for storage of variable arguments.
+                assert self.has_value_list, "Need a value list"
+            else:
+                self.imm_kinds.append(k)
+                self.imm_members.append(member)
+
             self.members.append(member)
             yield k
 

lib/cretonne/meta/gen_instr.py

@@ -84,20 +84,11 @@ def gen_arguments_method(fmt, is_mut):
                         .format(n, mut, mut, as_slice))
                     continue
 
-                has_varargs = cdsl.operands.VARIABLE_ARGS in f.kinds
-                # Formats with both fixed and variable arguments delegate to
-                # the data struct. We need to work around borrow checker quirks
-                # when extracting two mutable references.
-                if has_varargs and len(f.value_operands) > 0:
-                    fmt.line(
-                        '{} {{ ref {}data, .. }} => data.{}(),'
-                        .format(n, mut, method))
-                    continue
                 # Fixed args.
-                if len(f.value_operands) == 0:
+                if f.num_value_operands == 0:
                     arg = '&{}[]'.format(mut)
                     capture = ''
-                elif len(f.value_operands) == 1:
+                elif f.num_value_operands == 1:
                     if f.boxed_storage:
                         capture = 'ref {}data, '.format(mut)
                         arg = '{}(&{}data.arg)'.format(rslice, mut)
@@ -111,16 +102,9 @@ def gen_arguments_method(fmt, is_mut):
                     else:
                         capture = 'ref {}args, '.format(mut)
                         arg = 'args'
-                # Varargs.
-                if cdsl.operands.VARIABLE_ARGS in f.kinds:
-                    varg = '&{}data.varargs'.format(mut)
-                    capture = 'ref {}data, '.format(mut)
-                else:
-                    varg = '&{}[]'.format(mut)
-
                 fmt.line(
-                        '{} {{ {} .. }} => [{}, {}],'
-                        .format(n, capture, arg, varg))
+                        '{} {{ {} .. }} => [{}, &{}[]],'
+                        .format(n, capture, arg, mut))
 
 
 def gen_instruction_data_impl(fmt):
@@ -219,7 +203,7 @@ def gen_instruction_data_impl(fmt):
                         fmt.line(
                                 '{} {{ ref args, .. }} => '
                                 'args.get({}, pool),'.format(n, i))
-                    elif len(f.value_operands) == 1:
+                    elif f.num_value_operands == 1:
                         # We have a single value operand called 'arg'.
                         if f.boxed_storage:
                             fmt.line(
@@ -564,9 +548,9 @@ def gen_member_inits(iform, fmt):
     if iform.has_value_list:
         # Value-list formats put *all* arguments in the list.
         fmt.line('args: vlist,')
-    elif len(iform.value_operands) == 1:
+    elif iform.num_value_operands == 1:
         fmt.line('arg: op{},'.format(iform.value_operands[0]))
-    elif len(iform.value_operands) > 1:
+    elif iform.num_value_operands > 1:
         fmt.line('args: [{}],'.format(
             ', '.join('op{}'.format(i) for i in iform.value_operands)))
 

lib/cretonne/meta/gen_legalizer.py

@@ -46,8 +46,7 @@ def unwrap_inst(iref, node, fmt):
             fmt.line('ref data,')
         else:
             # Fields are encoded directly.
-            for m in iform.members:
-                if m:
+            for m in iform.imm_members:
                 fmt.line('{},'.format(m))
             if nvops == 1:
                 fmt.line('arg,')