py/emitnative: Simplify layout and loading of native function prelude.

Now native functions and native generators have similar behaviour: the
first machine-word of their code is an index to get to the prelude.  This
simplifies the handling of these types of functions, and also reduces the
size of the emitted native machine code by no longer requiring special code
at the start of the function to load a pointer to the prelude.

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

1 files changed, 4 insertions, 13 deletions

diff --git a/py/objgenerator.c b/py/objgenerator.c
index 7786b1fc8..e4acd5e49 100644
--- a/py/objgenerator.c
+++ b/py/objgenerator.c
@@ -101,13 +101,7 @@ STATIC mp_obj_t native_gen_wrap_call(mp_obj_t self_in, size_t n_args, size_t n_k
     mp_obj_fun_bc_t *self_fun = MP_OBJ_TO_PTR(self_in);
 
     // Determine start of prelude.
-    uintptr_t prelude_ptr_index = ((uintptr_t *)self_fun->bytecode)[0];
-    const uint8_t *prelude_ptr;
-    if (prelude_ptr_index == 0) {
-        prelude_ptr = (void *)self_fun->child_table;
-    } else {
-        prelude_ptr = (void *)self_fun->child_table[prelude_ptr_index];
-    }
+    const uint8_t *prelude_ptr = mp_obj_fun_native_get_prelude_ptr(self_fun);
 
     // Extract n_state from the prelude.
     const uint8_t *ip = prelude_ptr;
@@ -119,17 +113,14 @@ STATIC mp_obj_t native_gen_wrap_call(mp_obj_t self_in, size_t n_args, size_t n_k
     // Parse the input arguments and set up the code state
     o->pend_exc = mp_const_none;
     o->code_state.fun_bc = self_fun;
-    o->code_state.ip = prelude_ptr;
     o->code_state.n_state = n_state;
-    o->code_state.sp = &o->code_state.state[0] - 1;
     mp_setup_code_state_native(&o->code_state, n_args, n_kw, args);
 
     // Indicate we are a native function, which doesn't use this variable
     o->code_state.exc_sp_idx = MP_CODE_STATE_EXC_SP_IDX_SENTINEL;
 
     // Prepare the generator instance for execution
-    uintptr_t start_offset = ((uintptr_t *)self_fun->bytecode)[1];
-    o->code_state.ip = MICROPY_MAKE_POINTER_CALLABLE((void *)(self_fun->bytecode + start_offset));
+    o->code_state.ip = mp_obj_fun_native_get_generator_start(self_fun);
 
     return MP_OBJ_FROM_PTR(o);
 }
@@ -208,9 +199,9 @@ mp_vm_return_kind_t mp_obj_gen_resume(mp_obj_t self_in, mp_obj_t send_value, mp_
 
     #if MICROPY_EMIT_NATIVE
     if (self->code_state.exc_sp_idx == MP_CODE_STATE_EXC_SP_IDX_SENTINEL) {
-        // A native generator, with entry point 2 words into the "bytecode" pointer
+        // A native generator.
         typedef uintptr_t (*mp_fun_native_gen_t)(void *, mp_obj_t);
-        mp_fun_native_gen_t fun = MICROPY_MAKE_POINTER_CALLABLE((const void *)(self->code_state.fun_bc->bytecode + 2 * sizeof(uintptr_t)));
+        mp_fun_native_gen_t fun = mp_obj_fun_native_get_generator_resume(self->code_state.fun_bc);
         ret_kind = fun((void *)&self->code_state, throw_value);
     } else
     #endif