lib/codegen-meta moved into lib/codegen. (#423)

* lib/codegen-meta moved into lib/codegen.

* Renamed codegen-meta and existing meta.

lib/codegen/meta-python/base/predicates.py

@@ -0,0 +1,42 @@
+"""
+Cranelift predicates that consider `Function` fields.
+"""
+from cdsl.predicates import FieldPredicate
+from .formats import UnaryGlobalValue, InstructionFormat
+
+try:
+    from typing import TYPE_CHECKING
+    if TYPE_CHECKING:
+        from cdsl.formats import InstructionFormat, FormatField  # noqa
+except ImportError:
+    pass
+
+
+class IsColocatedFunc(FieldPredicate):
+    """
+    An instruction predicate that checks the referenced function is colocated.
+    """
+
+    def __init__(self, field):
+        # type: (FormatField) -> None
+        super(IsColocatedFunc, self).__init__(
+            field, 'is_colocated_func', ('func',))
+
+
+class IsColocatedData(FieldPredicate):
+    """
+    An instruction predicate that checks the referenced data object is
+    colocated.
+    """
+
+    def __init__(self):
+        # type: () -> None
+        super(IsColocatedData, self).__init__(
+            UnaryGlobalValue.global_value, 'is_colocated_data', ('func',))
+
+
+class LengthEquals(FieldPredicate):
+    def __init__(self, iform, num):
+        # type: (InstructionFormat, int) -> None
+        super(LengthEquals, self).__init__(
+            iform.args(), 'has_length_of', (num, 'func'))