Remove mp_obj_type_t.methods entry and use .locals_dict instead.

Originally, .methods was used for methods in a ROM class, and
locals_dict for methods in a user-created class.  That distinction is
unnecessary, and we can use locals_dict for ROM classes now that we have
ROMable maps.

This removes an entry in the bloated mp_obj_type_t struct, saving a word
for each ROM object and each RAM object.  ROM objects that have a
methods table (now a locals_dict) need an extra word in total (removed
the methods pointer (1 word), no longer need the sentinel (2 words), but
now need an mp_obj_dict_t wrapper (4 words)).  But RAM objects save a
word because they never used the methods entry.

Overall the ROM usage is down by a few hundred bytes, and RAM usage is
down 1 word per user-defined type/class.

There is less code (no need to check 2 tables), and now consistent with
the way ROM modules have their tables initialised.

Efficiency is very close to equivaluent.

1 files changed, 10 insertions, 8 deletions

diff --git a/stm/i2c.c b/stm/i2c.c
index 4d726c9593..b3d06df147 100644
--- a/stm/i2c.c
+++ b/stm/i2c.c
@@ -7,6 +7,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 
 typedef enum {
     PYB_I2C_1 = 0,
@@ -325,20 +326,21 @@ static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_read_obj, i2c_obj_read);
 static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_readAndStop_obj, i2c_obj_readAndStop);
 static MP_DEFINE_CONST_FUN_OBJ_1(i2c_obj_stop_obj, i2c_obj_stop);
 
-static const mp_method_t i2c_methods[] = {
-    { MP_QSTR_start, &i2c_obj_start_obj },
-    { MP_QSTR_write, &i2c_obj_write_obj },
-    { MP_QSTR_read, &i2c_obj_read_obj },
-    { MP_QSTR_readAndStop, &i2c_obj_readAndStop_obj },
-    { MP_QSTR_stop, &i2c_obj_stop_obj },
-    { MP_QSTR_NULL, NULL },
+STATIC const mp_map_elem_t i2c_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_start), (mp_obj_t)&i2c_obj_start_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&i2c_obj_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&i2c_obj_read_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readAndStop), (mp_obj_t)&i2c_obj_readAndStop_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_stop), (mp_obj_t)&i2c_obj_stop_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(i2c_locals_dict, i2c_locals_dict_table);
+
 static const mp_obj_type_t i2c_obj_type = {
     { &mp_type_type },
     .name = MP_QSTR_I2C,
     .print = i2c_obj_print,
-    .methods = i2c_methods,
+    .locals_dict = (mp_obj_t)&i2c_locals_dict,
 };
 
 // create the I2C object