diff --git a/py/asmthumb.c b/py/asmthumb.c
index a015994544..75ce168f73 100644
--- a/py/asmthumb.c
+++ b/py/asmthumb.c
@@ -496,17 +496,14 @@ void asm_thumb_bl_ind(asm_thumb_t *as, void *fun_ptr, uint fun_id, uint reg_temp
     asm_thumb_op16(as, 0x4780 | (REG_R9 << 3)); // blx reg
     */
 
-    if (0) {
-        // load ptr to function into register using immediate, then branch
-        // not relocatable
-        asm_thumb_mov_reg_i32(as, reg_temp, (mp_uint_t)fun_ptr);
-        asm_thumb_op16(as, OP_BLX(reg_temp));
-    } else if (1) {
+    if (fun_id < 32) {
+        // load ptr to function from table, indexed by fun_id (must be in range 0-31); 4 bytes
         asm_thumb_op16(as, OP_FORMAT_9_10(ASM_THUMB_FORMAT_9_LDR | ASM_THUMB_FORMAT_9_WORD_TRANSFER, reg_temp, REG_R7, fun_id));
         asm_thumb_op16(as, OP_BLX(reg_temp));
     } else {
-        // use SVC
-        asm_thumb_op16(as, OP_SVC(fun_id));
+        // load ptr to function into register using immediate; 6 bytes
+        asm_thumb_mov_reg_i32(as, reg_temp, (mp_uint_t)fun_ptr);
+        asm_thumb_op16(as, OP_BLX(reg_temp));
     }
 }
 
diff --git a/py/emitnative.c b/py/emitnative.c
index 87329808e9..8385f99055 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -530,55 +530,55 @@ STATIC void emit_post_push_reg_reg_reg_reg(emit_t *emit, vtype_kind_t vtypea, in
     emit_post_push_reg(emit, vtyped, regd);
 }
 
-STATIC void emit_call(emit_t *emit, mp_fun_kind_t fun_kind, void *fun) {
+STATIC void emit_call(emit_t *emit, mp_fun_kind_t fun_kind) {
     need_reg_all(emit);
 #if N_X64
-    asm_x64_call_ind(emit->as, fun, REG_RAX);
+    asm_x64_call_ind(emit->as, mp_fun_table[fun_kind], REG_RAX);
 #elif N_THUMB
     asm_thumb_bl_ind(emit->as, mp_fun_table[fun_kind], fun_kind, REG_R3);
 #endif
 }
 
-STATIC void emit_call_with_imm_arg(emit_t *emit, mp_fun_kind_t fun_kind, void *fun, mp_int_t arg_val, int arg_reg) {
+STATIC void emit_call_with_imm_arg(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val, int arg_reg) {
     need_reg_all(emit);
     ASM_MOV_IMM_TO_REG(arg_val, arg_reg);
 #if N_X64
-    asm_x64_call_ind(emit->as, fun, REG_RAX);
+    asm_x64_call_ind(emit->as, mp_fun_table[fun_kind], REG_RAX);
 #elif N_THUMB
     asm_thumb_bl_ind(emit->as, mp_fun_table[fun_kind], fun_kind, REG_R3);
 #endif
 }
 
 // the first arg is stored in the code aligned on a mp_uint_t boundary
-STATIC void emit_call_with_imm_arg_aligned(emit_t *emit, mp_fun_kind_t fun_kind, void *fun, mp_int_t arg_val, int arg_reg) {
+STATIC void emit_call_with_imm_arg_aligned(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val, int arg_reg) {
     need_reg_all(emit);
     ASM_MOV_ALIGNED_IMM_TO_REG(arg_val, arg_reg);
 #if N_X64
-    asm_x64_call_ind(emit->as, fun, REG_RAX);
+    asm_x64_call_ind(emit->as, mp_fun_table[fun_kind], REG_RAX);
 #elif N_THUMB
     asm_thumb_bl_ind(emit->as, mp_fun_table[fun_kind], fun_kind, REG_R3);
 #endif
 }
 
-STATIC void emit_call_with_2_imm_args(emit_t *emit, mp_fun_kind_t fun_kind, void *fun, mp_int_t arg_val1, int arg_reg1, mp_int_t arg_val2, int arg_reg2) {
+STATIC void emit_call_with_2_imm_args(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val1, int arg_reg1, mp_int_t arg_val2, int arg_reg2) {
     need_reg_all(emit);
     ASM_MOV_IMM_TO_REG(arg_val1, arg_reg1);
     ASM_MOV_IMM_TO_REG(arg_val2, arg_reg2);
 #if N_X64
-    asm_x64_call_ind(emit->as, fun, REG_RAX);
+    asm_x64_call_ind(emit->as, mp_fun_table[fun_kind], REG_RAX);
 #elif N_THUMB
     asm_thumb_bl_ind(emit->as, mp_fun_table[fun_kind], fun_kind, REG_R3);
 #endif
 }
 
 // the first arg is stored in the code aligned on a mp_uint_t boundary
-STATIC void emit_call_with_3_imm_args_and_first_aligned(emit_t *emit, mp_fun_kind_t fun_kind, void *fun, mp_int_t arg_val1, int arg_reg1, mp_int_t arg_val2, int arg_reg2, mp_int_t arg_val3, int arg_reg3) {
+STATIC void emit_call_with_3_imm_args_and_first_aligned(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val1, int arg_reg1, mp_int_t arg_val2, int arg_reg2, mp_int_t arg_val3, int arg_reg3) {
     need_reg_all(emit);
     ASM_MOV_ALIGNED_IMM_TO_REG(arg_val1, arg_reg1);
     ASM_MOV_IMM_TO_REG(arg_val2, arg_reg2);
     ASM_MOV_IMM_TO_REG(arg_val3, arg_reg3);
 #if N_X64
-    asm_x64_call_ind(emit->as, fun, REG_RAX);
+    asm_x64_call_ind(emit->as, mp_fun_table[fun_kind], REG_RAX);
 #elif N_THUMB
     asm_thumb_bl_ind(emit->as, mp_fun_table[fun_kind], fun_kind, REG_R3);
 #endif
@@ -631,7 +631,7 @@ STATIC void emit_get_stack_pointer_to_reg_for_pop(emit_t *emit, mp_uint_t reg_de
         if (si->vtype != VTYPE_PYOBJ) {
             mp_uint_t local_num = emit->stack_start + emit->stack_size - 1 - i;
             ASM_MOV_LOCAL_TO_REG(local_num, REG_ARG_1);
-            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, mp_convert_native_to_obj, si->vtype, REG_ARG_2); // arg2 = type
+            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, si->vtype, REG_ARG_2); // arg2 = type
             ASM_MOV_REG_TO_LOCAL(REG_RET, local_num);
             si->vtype = VTYPE_PYOBJ;
         }
@@ -684,7 +684,7 @@ STATIC void emit_native_import_name(emit_t *emit, qstr qst) {
     emit_pre_pop_reg_reg(emit, &vtype_fromlist, REG_ARG_2, &vtype_level, REG_ARG_3); // arg2 = fromlist, arg3 = level
     assert(vtype_fromlist == VTYPE_PYOBJ);
     assert(vtype_level == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_IMPORT_NAME, mp_import_name, qst, REG_ARG_1); // arg1 = import name
+    emit_call_with_imm_arg(emit, MP_F_IMPORT_NAME, qst, REG_ARG_1); // arg1 = import name
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -694,7 +694,7 @@ STATIC void emit_native_import_from(emit_t *emit, qstr qst) {
     vtype_kind_t vtype_module;
     emit_access_stack(emit, 1, &vtype_module, REG_ARG_1); // arg1 = module
     assert(vtype_module == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_IMPORT_FROM, mp_import_from, qst, REG_ARG_2); // arg2 = import name
+    emit_call_with_imm_arg(emit, MP_F_IMPORT_FROM, qst, REG_ARG_2); // arg2 = import name
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -703,7 +703,7 @@ STATIC void emit_native_import_star(emit_t *emit) {
     vtype_kind_t vtype_module;
     emit_pre_pop_reg(emit, &vtype_module, REG_ARG_1); // arg1 = module
     assert(vtype_module == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_IMPORT_ALL, mp_import_all);
+    emit_call(emit, MP_F_IMPORT_ALL);
     emit_post(emit);
 }
 
@@ -745,14 +745,14 @@ STATIC void emit_native_load_const_int(emit_t *emit, qstr qst) {
     DEBUG_printf("load_const_int %s\n", qstr_str(st));
     // for viper: load integer, check fits in 32 bits
     emit_native_pre(emit);
-    emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_INT, mp_load_const_int, qst, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_INT, qst, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
 STATIC void emit_native_load_const_dec(emit_t *emit, qstr qstr) {
     // for viper, a float/complex is just a Python object
     emit_native_pre(emit);
-    emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_DEC, mp_load_const_dec, qstr, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_DEC, qstr, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -765,9 +765,9 @@ STATIC void emit_native_load_const_str(emit_t *emit, qstr qstr, bool bytes) {
         emit_post_push_imm(emit, VTYPE_PTR, (mp_uint_t)qstr_str(qstr));
     } else {
         if (bytes) {
-            emit_call_with_imm_arg(emit, 0, mp_load_const_bytes, qstr, REG_ARG_1); // TODO need to add function to runtime table
+            emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_BYTES, qstr, REG_ARG_1);
         } else {
-            emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_STR, mp_load_const_str, qstr, REG_ARG_1);
+            emit_call_with_imm_arg(emit, MP_F_LOAD_CONST_STR, qstr, REG_ARG_1);
         }
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     }
@@ -815,13 +815,13 @@ STATIC void emit_native_load_deref(emit_t *emit, qstr qstr, int local_num) {
 
 STATIC void emit_native_load_name(emit_t *emit, qstr qstr) {
     emit_native_pre(emit);
-    emit_call_with_imm_arg(emit, MP_F_LOAD_NAME, mp_load_name, qstr, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_LOAD_NAME, qstr, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
 STATIC void emit_native_load_global(emit_t *emit, qstr qstr) {
     emit_native_pre(emit);
-    emit_call_with_imm_arg(emit, MP_F_LOAD_GLOBAL, mp_load_global, qstr, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_LOAD_GLOBAL, qstr, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -833,7 +833,7 @@ STATIC void emit_native_load_attr(emit_t *emit, qstr qstr) {
     vtype_kind_t vtype_base;
     emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
     assert(vtype_base == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_LOAD_ATTR, mp_load_attr, qstr, REG_ARG_2); // arg2 = attribute name
+    emit_call_with_imm_arg(emit, MP_F_LOAD_ATTR, qstr, REG_ARG_2); // arg2 = attribute name
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -842,12 +842,12 @@ STATIC void emit_native_load_method(emit_t *emit, qstr qstr) {
     emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
     assert(vtype_base == VTYPE_PYOBJ);
     emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, 2); // arg3 = dest ptr
-    emit_call_with_imm_arg(emit, MP_F_LOAD_METHOD, mp_load_method, qstr, REG_ARG_2); // arg2 = method name
+    emit_call_with_imm_arg(emit, MP_F_LOAD_METHOD, qstr, REG_ARG_2); // arg2 = method name
 }
 
 STATIC void emit_native_load_build_class(emit_t *emit) {
     emit_native_pre(emit);
-    emit_call(emit, MP_F_LOAD_BUILD_CLASS, mp_load_build_class);
+    emit_call(emit, MP_F_LOAD_BUILD_CLASS);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -855,7 +855,7 @@ STATIC void emit_native_load_subscr(emit_t *emit) {
     vtype_kind_t vtype_lhs, vtype_rhs;
     emit_pre_pop_reg_reg(emit, &vtype_rhs, REG_ARG_2, &vtype_lhs, REG_ARG_1);
     if (vtype_lhs == VTYPE_PYOBJ && vtype_rhs == VTYPE_PYOBJ) {
-        emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, mp_obj_subscr, (mp_uint_t)MP_OBJ_SENTINEL, REG_ARG_3);
+        emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, (mp_uint_t)MP_OBJ_SENTINEL, REG_ARG_3);
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     } else {
         printf("ViperTypeError: can't do subscr of types %d and %d\n", vtype_lhs, vtype_rhs);
@@ -906,7 +906,7 @@ STATIC void emit_native_store_name(emit_t *emit, qstr qstr) {
     vtype_kind_t vtype;
     emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
     assert(vtype == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_STORE_NAME, mp_store_name, qstr, REG_ARG_1); // arg1 = name
+    emit_call_with_imm_arg(emit, MP_F_STORE_NAME, qstr, REG_ARG_1); // arg1 = name
     emit_post(emit);
 }
 
@@ -916,10 +916,10 @@ STATIC void emit_native_store_global(emit_t *emit, qstr qstr) {
         emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
     } else {
         emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
-        emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, mp_convert_native_to_obj, vtype, REG_ARG_2); // arg2 = type
+        emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, vtype, REG_ARG_2); // arg2 = type
         ASM_MOV_REG_TO_REG(REG_RET, REG_ARG_2);
     }
-    emit_call_with_imm_arg(emit, MP_F_STORE_GLOBAL, mp_store_global, qstr, REG_ARG_1); // arg1 = name
+    emit_call_with_imm_arg(emit, MP_F_STORE_GLOBAL, qstr, REG_ARG_1); // arg1 = name
     emit_post(emit);
 }
 
@@ -928,7 +928,7 @@ STATIC void emit_native_store_attr(emit_t *emit, qstr qstr) {
     emit_pre_pop_reg_reg(emit, &vtype_base, REG_ARG_1, &vtype_val, REG_ARG_3); // arg1 = base, arg3 = value
     assert(vtype_base == VTYPE_PYOBJ);
     assert(vtype_val == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_STORE_ATTR, mp_store_attr, qstr, REG_ARG_2); // arg2 = attribute name
+    emit_call_with_imm_arg(emit, MP_F_STORE_ATTR, qstr, REG_ARG_2); // arg2 = attribute name
     emit_post(emit);
 }
 
@@ -942,7 +942,7 @@ STATIC void emit_native_store_subscr(emit_t *emit) {
     assert(vtype_index == VTYPE_PYOBJ);
     assert(vtype_base == VTYPE_PYOBJ);
     assert(vtype_value == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_OBJ_SUBSCR, mp_obj_subscr);
+    emit_call(emit, MP_F_OBJ_SUBSCR);
 }
 
 STATIC void emit_native_delete_fast(emit_t *emit, qstr qstr, int local_num) {
@@ -972,7 +972,7 @@ STATIC void emit_native_delete_attr(emit_t *emit, qstr qstr) {
     vtype_kind_t vtype_base;
     emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
     assert(vtype_base == VTYPE_PYOBJ);
-    emit_call_with_2_imm_args(emit, MP_F_STORE_ATTR, mp_store_attr, qstr, REG_ARG_2, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3); // arg2 = attribute name, arg3 = value (null for delete)
+    emit_call_with_2_imm_args(emit, MP_F_STORE_ATTR, qstr, REG_ARG_2, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3); // arg2 = attribute name, arg3 = value (null for delete)
     emit_post(emit);
 }
 
@@ -981,7 +981,7 @@ STATIC void emit_native_delete_subscr(emit_t *emit) {
     emit_pre_pop_reg_reg(emit, &vtype_index, REG_ARG_2, &vtype_base, REG_ARG_1); // index, base
     assert(vtype_index == VTYPE_PYOBJ);
     assert(vtype_base == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, mp_obj_subscr, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3);
+    emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3);
 }
 
 STATIC void emit_native_dup_top(emit_t *emit) {
@@ -1035,7 +1035,7 @@ STATIC void emit_native_jump_helper(emit_t *emit, uint label, bool pop) {
         }
     } else if (vtype == VTYPE_PYOBJ) {
         emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
-        emit_call(emit, MP_F_OBJ_IS_TRUE, mp_obj_is_true);
+        emit_call(emit, MP_F_OBJ_IS_TRUE);
         if (!pop) {
             emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
         }
@@ -1119,7 +1119,7 @@ STATIC void emit_native_setup_except(emit_t *emit, uint label) {
     // need to commit stack because we may jump elsewhere
     need_stack_settled(emit);
     emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_1, sizeof(nlr_buf_t) / sizeof(mp_uint_t)); // arg1 = pointer to nlr buf
-    emit_call(emit, 0, nlr_push); // TODO need to add function to runtime table
+    emit_call(emit, MP_F_NLR_PUSH);
 #if N_X64
     asm_x64_test_r8_with_r8(emit->as, REG_RET, REG_RET);
     asm_x64_jcc_label(emit->as, JCC_JNZ, label);
@@ -1145,7 +1145,7 @@ STATIC void emit_native_get_iter(emit_t *emit) {
     vtype_kind_t vtype;
     emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
     assert(vtype == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_GETITER, mp_getiter);
+    emit_call(emit, MP_F_GETITER);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -1154,7 +1154,7 @@ STATIC void emit_native_for_iter(emit_t *emit, uint label) {
     vtype_kind_t vtype;
     emit_access_stack(emit, 1, &vtype, REG_ARG_1);
     assert(vtype == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_ITERNEXT, mp_iternext);
+    emit_call(emit, MP_F_ITERNEXT);
     ASM_MOV_IMM_TO_REG((mp_uint_t)MP_OBJ_STOP_ITERATION, REG_TEMP1);
 #if N_X64
     asm_x64_cmp_r64_with_r64(emit->as, REG_RET, REG_TEMP1);
@@ -1175,7 +1175,7 @@ STATIC void emit_native_for_iter_end(emit_t *emit) {
 
 STATIC void emit_native_pop_block(emit_t *emit) {
     emit_native_pre(emit);
-    emit_call(emit, 0, nlr_pop); // TODO need to add function to runtime table
+    emit_call(emit, MP_F_NLR_POP);
     adjust_stack(emit, -(mp_int_t)(sizeof(nlr_buf_t) / sizeof(mp_uint_t)));
     emit_post(emit);
 }
@@ -1183,7 +1183,7 @@ STATIC void emit_native_pop_block(emit_t *emit) {
 STATIC void emit_native_pop_except(emit_t *emit) {
     /*
     emit_native_pre(emit);
-    emit_call(emit, 0, nlr_pop); // TODO need to add function to runtime table
+    emit_call(emit, MP_F_NLR_POP);
     adjust_stack(emit, -(mp_int_t)(sizeof(nlr_buf_t) / sizeof(mp_uint_t)));
     emit_post(emit);
     */
@@ -1197,7 +1197,7 @@ STATIC void emit_native_unary_op(emit_t *emit, mp_unary_op_t op) {
         vtype_kind_t vtype;
         emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
         assert(vtype == VTYPE_PYOBJ);
-        emit_call_with_imm_arg(emit, MP_F_UNARY_OP, mp_unary_op, op, REG_ARG_1);
+        emit_call_with_imm_arg(emit, MP_F_UNARY_OP, op, REG_ARG_1);
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     }
 }
@@ -1230,7 +1230,7 @@ STATIC void emit_native_binary_op(emit_t *emit, mp_binary_op_t op) {
             assert(0);
         }
     } else if (vtype_lhs == VTYPE_PYOBJ && vtype_rhs == VTYPE_PYOBJ) {
-        emit_call_with_imm_arg(emit, MP_F_BINARY_OP, mp_binary_op, op, REG_ARG_1);
+        emit_call_with_imm_arg(emit, MP_F_BINARY_OP, op, REG_ARG_1);
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     } else {
         printf("ViperTypeError: can't do binary op between types %d and %d\n", vtype_lhs, vtype_rhs);
@@ -1243,14 +1243,14 @@ STATIC void emit_native_build_tuple(emit_t *emit, int n_args) {
     //   if wrapped in byte_array, or something, allocates memory and fills it
     emit_native_pre(emit);
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_2, n_args); // pointer to items
-    emit_call_with_imm_arg(emit, MP_F_BUILD_TUPLE, mp_obj_new_tuple, n_args, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_BUILD_TUPLE, n_args, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // new tuple
 }
 
 STATIC void emit_native_build_list(emit_t *emit, int n_args) {
     emit_native_pre(emit);
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_2, n_args); // pointer to items
-    emit_call_with_imm_arg(emit, MP_F_BUILD_LIST, mp_obj_new_list, n_args, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_BUILD_LIST, n_args, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // new list
 }
 
@@ -1261,13 +1261,13 @@ STATIC void emit_native_list_append(emit_t *emit, int list_index) {
     emit_access_stack(emit, list_index, &vtype_list, REG_ARG_1);
     assert(vtype_list == VTYPE_PYOBJ);
     assert(vtype_item == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_LIST_APPEND, mp_obj_list_append);
+    emit_call(emit, MP_F_LIST_APPEND);
     emit_post(emit);
 }
 
 STATIC void emit_native_build_map(emit_t *emit, int n_args) {
     emit_native_pre(emit);
-    emit_call_with_imm_arg(emit, MP_F_BUILD_MAP, mp_obj_new_dict, n_args, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_BUILD_MAP, n_args, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // new map
 }
 
@@ -1277,7 +1277,7 @@ STATIC void emit_native_store_map(emit_t *emit) {
     assert(vtype_key == VTYPE_PYOBJ);
     assert(vtype_value == VTYPE_PYOBJ);
     assert(vtype_map == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_STORE_MAP, mp_obj_dict_store);
+    emit_call(emit, MP_F_STORE_MAP);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // map
 }
 
@@ -1289,14 +1289,14 @@ STATIC void emit_native_map_add(emit_t *emit, int map_index) {
     assert(vtype_map == VTYPE_PYOBJ);
     assert(vtype_key == VTYPE_PYOBJ);
     assert(vtype_value == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_STORE_MAP, mp_obj_dict_store);
+    emit_call(emit, MP_F_STORE_MAP);
     emit_post(emit);
 }
 
 STATIC void emit_native_build_set(emit_t *emit, int n_args) {
     emit_native_pre(emit);
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_2, n_args); // pointer to items
-    emit_call_with_imm_arg(emit, MP_F_BUILD_SET, mp_obj_new_set, n_args, REG_ARG_1);
+    emit_call_with_imm_arg(emit, MP_F_BUILD_SET, n_args, REG_ARG_1);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // new set
 }
 
@@ -1307,7 +1307,7 @@ STATIC void emit_native_set_add(emit_t *emit, int set_index) {
     emit_access_stack(emit, set_index, &vtype_set, REG_ARG_1);
     assert(vtype_set == VTYPE_PYOBJ);
     assert(vtype_item == VTYPE_PYOBJ);
-    emit_call(emit, MP_F_STORE_SET, mp_obj_set_store);
+    emit_call(emit, MP_F_STORE_SET);
     emit_post(emit);
 }
 
@@ -1318,7 +1318,7 @@ STATIC void emit_native_build_slice(emit_t *emit, int n_args) {
         emit_pre_pop_reg_reg(emit, &vtype_stop, REG_ARG_2, &vtype_start, REG_ARG_1); // arg1 = start, arg2 = stop
         assert(vtype_start == VTYPE_PYOBJ);
         assert(vtype_stop == VTYPE_PYOBJ);
-        emit_call_with_imm_arg(emit, MP_F_NEW_SLICE, mp_obj_new_slice, (mp_uint_t)mp_const_none, REG_ARG_3); // arg3 = step
+        emit_call_with_imm_arg(emit, MP_F_NEW_SLICE, (mp_uint_t)mp_const_none, REG_ARG_3); // arg3 = step
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     } else {
         assert(n_args == 3);
@@ -1327,7 +1327,7 @@ STATIC void emit_native_build_slice(emit_t *emit, int n_args) {
         assert(vtype_start == VTYPE_PYOBJ);
         assert(vtype_stop == VTYPE_PYOBJ);
         assert(vtype_step == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_NEW_SLICE, mp_obj_new_slice);
+        emit_call(emit, MP_F_NEW_SLICE);
         emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     }
 }
@@ -1338,7 +1338,7 @@ STATIC void emit_native_unpack_sequence(emit_t *emit, int n_args) {
     emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = seq
     assert(vtype_base == VTYPE_PYOBJ);
     emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, n_args); // arg3 = dest ptr
-    emit_call_with_imm_arg(emit, MP_F_UNPACK_SEQUENCE, mp_unpack_sequence, n_args, REG_ARG_2); // arg2 = n_args
+    emit_call_with_imm_arg(emit, MP_F_UNPACK_SEQUENCE, n_args, REG_ARG_2); // arg2 = n_args
 }
 
 STATIC void emit_native_unpack_ex(emit_t *emit, int n_left, int n_right) {
@@ -1347,20 +1347,20 @@ STATIC void emit_native_unpack_ex(emit_t *emit, int n_left, int n_right) {
     emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = seq
     assert(vtype_base == VTYPE_PYOBJ);
     emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, n_left + n_right + 1); // arg3 = dest ptr
-    emit_call_with_imm_arg(emit, MP_F_UNPACK_EX, mp_unpack_ex, n_left | (n_right << 8), REG_ARG_2); // arg2 = n_left + n_right
+    emit_call_with_imm_arg(emit, MP_F_UNPACK_EX, n_left | (n_right << 8), REG_ARG_2); // arg2 = n_left + n_right
 }
 
 STATIC void emit_native_make_function(emit_t *emit, scope_t *scope, uint n_pos_defaults, uint n_kw_defaults) {
     // call runtime, with type info for args, or don't support dict/default params, or only support Python objects for them
     emit_native_pre(emit);
     if (n_pos_defaults == 0 && n_kw_defaults == 0) {
-        emit_call_with_3_imm_args_and_first_aligned(emit, MP_F_MAKE_FUNCTION_FROM_RAW_CODE, mp_make_function_from_raw_code, (mp_uint_t)scope->raw_code, REG_ARG_1, (mp_uint_t)MP_OBJ_NULL, REG_ARG_2, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3);
+        emit_call_with_3_imm_args_and_first_aligned(emit, MP_F_MAKE_FUNCTION_FROM_RAW_CODE, (mp_uint_t)scope->raw_code, REG_ARG_1, (mp_uint_t)MP_OBJ_NULL, REG_ARG_2, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3);
     } else {
         vtype_kind_t vtype_def_tuple, vtype_def_dict;
         emit_pre_pop_reg_reg(emit, &vtype_def_dict, REG_ARG_3, &vtype_def_tuple, REG_ARG_2);
         assert(vtype_def_tuple == VTYPE_PYOBJ);
         assert(vtype_def_dict == VTYPE_PYOBJ);
-        emit_call_with_imm_arg_aligned(emit, MP_F_MAKE_FUNCTION_FROM_RAW_CODE, mp_make_function_from_raw_code, (mp_uint_t)scope->raw_code, REG_ARG_1);
+        emit_call_with_imm_arg_aligned(emit, MP_F_MAKE_FUNCTION_FROM_RAW_CODE, (mp_uint_t)scope->raw_code, REG_ARG_1);
     }
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
@@ -1380,20 +1380,20 @@ STATIC void emit_native_call_function(emit_t *emit, int n_positional, int n_keyw
         vtype_kind_t vtype_fun;
         emit_pre_pop_reg(emit, &vtype_fun, REG_ARG_1); // the function
         assert(vtype_fun == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_CALL_FUNCTION_0, mp_call_function_0);
+        emit_call(emit, MP_F_CALL_FUNCTION_0);
     } else if (n_positional == 1) {
         vtype_kind_t vtype_fun, vtype_arg1;
         emit_pre_pop_reg_reg(emit, &vtype_arg1, REG_ARG_2, &vtype_fun, REG_ARG_1); // the single argument, the function
         assert(vtype_fun == VTYPE_PYOBJ);
         assert(vtype_arg1 == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_CALL_FUNCTION_1, mp_call_function_1);
+        emit_call(emit, MP_F_CALL_FUNCTION_1);
     } else if (n_positional == 2) {
         vtype_kind_t vtype_fun, vtype_arg1, vtype_arg2;
         emit_pre_pop_reg_reg_reg(emit, &vtype_arg2, REG_ARG_3, &vtype_arg1, REG_ARG_2, &vtype_fun, REG_ARG_1); // the second argument, the first argument, the function
         assert(vtype_fun == VTYPE_PYOBJ);
         assert(vtype_arg1 == VTYPE_PYOBJ);
         assert(vtype_arg2 == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_CALL_FUNCTION_2, mp_call_function_2);
+        emit_call(emit, MP_F_CALL_FUNCTION_2);
     } else {
     */
 
@@ -1404,7 +1404,7 @@ STATIC void emit_native_call_function(emit_t *emit, int n_positional, int n_keyw
     vtype_kind_t vtype_fun;
     emit_pre_pop_reg(emit, &vtype_fun, REG_ARG_1); // the function
     assert(vtype_fun == VTYPE_PYOBJ);
-    emit_call_with_imm_arg(emit, MP_F_NATIVE_CALL_FUNCTION_N_KW, mp_native_call_function_n_kw, n_positional | (n_keyword << 8), REG_ARG_2);
+    emit_call_with_imm_arg(emit, MP_F_NATIVE_CALL_FUNCTION_N_KW, n_positional | (n_keyword << 8), REG_ARG_2);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -1417,20 +1417,20 @@ STATIC void emit_native_call_method(emit_t *emit, int n_positional, int n_keywor
         emit_pre_pop_reg_reg(emit, &vtype_self, REG_ARG_2, &vtype_meth, REG_ARG_1); // the self object (or NULL), the method
         assert(vtype_meth == VTYPE_PYOBJ);
         assert(vtype_self == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_CALL_METHOD_1, mp_call_method_1);
+        emit_call(emit, MP_F_CALL_METHOD_1);
     } else if (n_positional == 1) {
         vtype_kind_t vtype_meth, vtype_self, vtype_arg1;
         emit_pre_pop_reg_reg_reg(emit, &vtype_arg1, REG_ARG_3, &vtype_self, REG_ARG_2, &vtype_meth, REG_ARG_1); // the first argument, the self object (or NULL), the method
         assert(vtype_meth == VTYPE_PYOBJ);
         assert(vtype_self == VTYPE_PYOBJ);
         assert(vtype_arg1 == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_CALL_METHOD_2, mp_call_method_2);
+        emit_call(emit, MP_F_CALL_METHOD_2);
     } else {
     */
 
     emit_native_pre(emit);
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 2 + n_positional + 2 * n_keyword); // pointer to items, including meth and self
-    emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, mp_call_method_n_kw, n_positional, REG_ARG_1, n_keyword, REG_ARG_2);
+    emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, n_positional, REG_ARG_1, n_keyword, REG_ARG_2);
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 
@@ -1467,7 +1467,7 @@ STATIC void emit_native_raise_varargs(emit_t *emit, int n_args) {
         printf("ViperTypeError: must raise an object\n");
     }
     // TODO probably make this 1 call to the runtime (which could even call convert, native_raise(obj, type))
-    emit_call(emit, MP_F_NATIVE_RAISE, mp_native_raise);
+    emit_call(emit, MP_F_NATIVE_RAISE);
 }
 
 STATIC void emit_native_yield_value(emit_t *emit) {
diff --git a/py/runtime.c b/py/runtime.c
index caaf795ef9..8dbdac9d92 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -1192,13 +1192,14 @@ NORETURN void mp_native_raise(mp_obj_t o) {
     nlr_raise(mp_make_raise_obj(o));
 }
 
-// these must correspond to the respective enum
+// these must correspond to the respective enum in runtime0.h
 void *const mp_fun_table[MP_F_NUMBER_OF] = {
     mp_convert_obj_to_native,
     mp_convert_native_to_obj,
     mp_load_const_int,
     mp_load_const_dec,
     mp_load_const_str,
+    mp_load_const_bytes,
     mp_load_name,
     mp_load_global,
     mp_load_build_class,
@@ -1225,6 +1226,8 @@ void *const mp_fun_table[MP_F_NUMBER_OF] = {
     mp_call_method_n_kw,
     mp_getiter,
     mp_iternext,
+    nlr_push,
+    nlr_pop,
     mp_native_raise,
     mp_import_name,
     mp_import_from,
diff --git a/py/runtime0.h b/py/runtime0.h
index 8ae8afacc7..7bb16545f7 100644
--- a/py/runtime0.h
+++ b/py/runtime0.h
@@ -107,6 +107,7 @@ typedef enum {
     MP_F_LOAD_CONST_INT,
     MP_F_LOAD_CONST_DEC,
     MP_F_LOAD_CONST_STR,
+    MP_F_LOAD_CONST_BYTES,
     MP_F_LOAD_NAME,
     MP_F_LOAD_GLOBAL,
     MP_F_LOAD_BUILD_CLASS,
@@ -133,9 +134,11 @@ typedef enum {
     MP_F_CALL_METHOD_N_KW,
     MP_F_GETITER,
     MP_F_ITERNEXT,
+    MP_F_NLR_PUSH,
+    MP_F_NLR_POP,
     MP_F_NATIVE_RAISE,
     MP_F_IMPORT_NAME,
-    MP_F_IMPORT_FROM, // = 31 XXX this is the limit for thumb code...
+    MP_F_IMPORT_FROM,
     MP_F_IMPORT_ALL,
 #if MICROPY_PY_BUILTINS_SLICE
     MP_F_NEW_SLICE,