py: Optimise types for common case where type has a single parent type.
The common cases for inheritance are 0 or 1 parent types, for both built-in
types (eg built-in exceptions) as well as user defined types. So it makes
sense to optimise the case of 1 parent type by storing just the type and
not a tuple of 1 value (that value being the single parent type).
This patch makes such an optimisation. Even though there is a bit more
code to handle the two cases (either a single type or a tuple with 2 or
more values) it helps reduce overall code size because it eliminates the
need to create a static tuple to hold single parents (eg for the built-in
exceptions). It also helps reduce RAM usage for user defined types that
only derive from a single parent.
Changes in code size (in bytes) due to this patch:
bare-arm: -16
minimal (x86): -176
unix (x86-64): -320
unix nanbox: -384
stmhal: -64
cc3200: -32
esp8266: -108
diff --git a/py/objdict.c b/py/objdict.c
index f6929d2..12ba61b 100644
--- a/py/objdict.c
+++ b/py/objdict.c
@@ -577,8 +577,6 @@
};
#if MICROPY_PY_COLLECTIONS_ORDEREDDICT
-STATIC const mp_rom_obj_tuple_t ordereddict_base_tuple = {{&mp_type_tuple}, 1, {MP_ROM_PTR(&mp_type_dict)}};
-
const mp_obj_type_t mp_type_ordereddict = {
{ &mp_type_type },
.name = MP_QSTR_OrderedDict,
@@ -588,7 +586,7 @@
.binary_op = dict_binary_op,
.subscr = dict_subscr,
.getiter = dict_getiter,
- .bases_tuple = (mp_obj_tuple_t*)(mp_rom_obj_tuple_t*)&ordereddict_base_tuple,
+ .parent = &mp_type_dict,
.locals_dict = (mp_obj_dict_t*)&dict_locals_dict,
};
#endif