py/emitglue: Reorder and resize members of mp_raw_code_t.

The mp_raw_code_t struct has been reordered and some members resized.  The
`n_pos_args` member is renamed to `asm_n_pos_args`, and `type_sig` renamed
to `asm_type_sig` to indicate that these are used only for the inline-asm
emitters.  These two members are also grouped together in the struct.

The justifications for resizing the members are:
- `fun_data_len` can be 32-bits without issue
- `n_children` is already limited to 16-bits by
  `mp_emit_common_t::ct_cur_child`
- `scope_flags` is already limited to 16-bits by `scope_t::scope_flags`
- `prelude_offset` is already limited to 16-bits by the argument to
  `mp_emit_glue_assign_native()`
- it's reasonable to limit the maximim number of inline-asm arguments to 12
  (24 bits for `asm_type_sig` divided by 2)

This change helps to reduce frozen code size (and in some cases RAM usage)
in the following cases:
- 64-bit targets
- builds with MICROPY_PY_SYS_SETTRACE enabled
- builds with MICROPY_EMIT_MACHINE_CODE enabled but MICROPY_EMIT_INLINE_ASM
  disabled

With this change, unix 64-bit builds are -4080 bytes in size.  Bare-metal
ports like rp2 are unchanged (because mp_raw_code_t is still 32 bytes on
those 32-bit targets).

Signed-off-by: Damien George <damien@micropython.org>

py/emitglue.h

@@ -49,34 +49,38 @@ typedef enum {
     MP_CODE_NATIVE_ASM,
 } mp_raw_code_kind_t;
 
+// This mp_raw_code_t struct holds static information about a non-instantiated function.
+// A function object is created from this information, and that object can then be executed.
+//
+// This struct appears in the following places:
 // compiled bytecode: instance in RAM, referenced by outer scope, usually freed after first (and only) use
 // mpy file: instance in RAM, created when .mpy file is loaded (same comments as above)
 // frozen: instance in ROM
 typedef struct _mp_raw_code_t {
-    mp_uint_t kind : 3; // of type mp_raw_code_kind_t
-    mp_uint_t scope_flags : 7;
-    mp_uint_t n_pos_args : 11;
+    uint32_t kind : 3; // of type mp_raw_code_kind_t
+    uint32_t scope_flags : 7;
     const void *fun_data;
-    #if MICROPY_PERSISTENT_CODE_SAVE || MICROPY_DEBUG_PRINTERS
-    size_t fun_data_len; // so mp_raw_code_save and mp_bytecode_print work
-    #endif
     struct _mp_raw_code_t **children;
+    #if MICROPY_PERSISTENT_CODE_SAVE || MICROPY_DEBUG_PRINTERS
+    uint32_t fun_data_len; // so mp_raw_code_save and mp_bytecode_print work
+    #endif
     #if MICROPY_PERSISTENT_CODE_SAVE
-    size_t n_children;
+    uint16_t n_children;
+    #if MICROPY_EMIT_MACHINE_CODE
+    uint16_t prelude_offset;
+    #endif
     #if MICROPY_PY_SYS_SETTRACE
-    mp_bytecode_prelude_t prelude;
     // line_of_definition is a Python source line where the raw_code was
     // created e.g. MP_BC_MAKE_FUNCTION. This is different from lineno info
     // stored in prelude, which provides line number for first statement of
     // a function. Required to properly implement "call" trace event.
-    mp_uint_t line_of_definition;
-    #endif
-    #if MICROPY_EMIT_MACHINE_CODE
-    uint16_t prelude_offset;
+    uint32_t line_of_definition;
+    mp_bytecode_prelude_t prelude;
     #endif
     #endif
-    #if MICROPY_EMIT_MACHINE_CODE
-    mp_uint_t type_sig; // for viper, compressed as 2-bit types; ret is MSB, then arg0, arg1, etc
+    #if MICROPY_EMIT_INLINE_ASM
+    uint32_t asm_n_pos_args : 8;
+    uint32_t asm_type_sig : 24; // compressed as 2-bit types; ret is MSB, then arg0, arg1, etc
     #endif
 } mp_raw_code_t;
 
@@ -88,17 +92,17 @@ void mp_emit_glue_assign_bytecode(mp_raw_code_t *rc, const byte *code,
     #endif
     mp_raw_code_t **children,
     #if MICROPY_PERSISTENT_CODE_SAVE
-    size_t n_children,
+    uint16_t n_children,
     #endif
-    mp_uint_t scope_flags);
+    uint16_t scope_flags);
 
 void mp_emit_glue_assign_native(mp_raw_code_t *rc, mp_raw_code_kind_t kind, void *fun_data, mp_uint_t fun_len,
     mp_raw_code_t **children,
     #if MICROPY_PERSISTENT_CODE_SAVE
-    size_t n_children,
+    uint16_t n_children,
     uint16_t prelude_offset,
     #endif
-    mp_uint_t scope_flags, mp_uint_t n_pos_args, mp_uint_t type_sig);
+    uint16_t scope_flags, uint32_t asm_n_pos_args, uint32_t asm_type_sig);
 
 mp_obj_t mp_make_function_from_raw_code(const mp_raw_code_t *rc, const mp_module_context_t *context, const mp_obj_t *def_args);
 mp_obj_t mp_make_closure_from_raw_code(const mp_raw_code_t *rc, const mp_module_context_t *context, mp_uint_t n_closed_over, const mp_obj_t *args);