py: Store bytecode arg names in bytecode (were in own array).

This saves a lot of RAM for 2 reasons:

1. For functions that don't have default values, var args or var kw
args (which is a large number of functions in the general case), the
mp_obj_fun_bc_t type now fits in 1 GC block (previously needed 2 because
of the extra pointer to point to the arg_names array).  So this saves 16
bytes per function (32 bytes on 64-bit machines).

2. Combining separate memory regions generally saves RAM because the
unused bytes at the end of the GC block are saved for 1 of the blocks
(since that block doesn't exist on its own anymore).  So generally this
saves 8 bytes per function.

Tested by importing lots of modules:

- 64-bit Linux gave about an 8% RAM saving for 86k of used RAM.
- pyboard gave about a 6% RAM saving for 31k of used RAM.

1 files changed, 3 insertions, 0 deletions

diff --git a/py/objgenerator.c b/py/objgenerator.c
index 9d16d2bee0..ce26cbce26 100644
--- a/py/objgenerator.c
+++ b/py/objgenerator.c
@@ -62,6 +62,9 @@ STATIC mp_obj_t gen_wrap_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw
     mp_uint_t code_info_size = mp_decode_uint(&code_info);
     const byte *ip = self_fun->bytecode + code_info_size;
 
+    // bytecode prelude: skip arg names
+    ip += (self_fun->n_pos_args + self_fun->n_kwonly_args) * sizeof(mp_obj_t);
+
     // bytecode prelude: get state size and exception stack size
     mp_uint_t n_state = mp_decode_uint(&ip);
     mp_uint_t n_exc_stack = mp_decode_uint(&ip);