Move formats, entities, and immediates to the base package.

- base.formats defines instruction formats.
- base.entities defines kinds of entity references.
- base.immediates defines kinds of imediate operands.

lib/cretonne/meta/base/entities.py

@@ -0,0 +1,29 @@
+"""
+The `cretonne.entities` module predefines all the Cretonne entity reference
+operand types. There are corresponding definitions in the `cretonne.entities`
+Rust module.
+"""
+from __future__ import absolute_import
+from cdsl.operands import EntityRefKind
+
+
+#: A reference to an extended basic block in the same function.
+#: This is primarliy used in control flow instructions.
+ebb = EntityRefKind(
+        'ebb', 'An extended basic block in the same function.',
+        default_member='destination')
+
+#: A reference to a stack slot declared in the function preamble.
+stack_slot = EntityRefKind('stack_slot', 'A stack slot.')
+
+#: A reference to a function sugnature declared in the function preamble.
+#: Tbis is used to provide the call signature in an indirect call instruction.
+sig_ref = EntityRefKind('sig_ref', 'A function signature.')
+
+#: A reference to an external function declared in the function preamble.
+#: This is used to provide the callee and signature in a call instruction.
+func_ref = EntityRefKind('func_ref', 'An external function.')
+
+#: A reference to a jump table declared in the function preamble.
+jump_table = EntityRefKind(
+        'jump_table', 'A jump table.', default_member='table')