py/emitnative: Put None/False/True in global native const table.

So these constant objects can be loaded by dereferencing the REG_FUN_TABLE
pointer instead of loading immediate values.  This reduces the size of
generated native code (when such constants are used), and means that
pointers to these constants are no longer stored in the assembly code.

py/emitnative.c

@@ -250,6 +250,10 @@ void EXPORT_FUN(free)(emit_t *emit) {
 
 STATIC void emit_call_with_imm_arg(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val, int arg_reg);
 
+STATIC void emit_native_mov_reg_const(emit_t *emit, int reg_dest, int const_val) {
+    ASM_LOAD_REG_REG_OFFSET(emit->as, reg_dest, REG_FUN_TABLE, const_val);
+}
+
 STATIC void emit_native_mov_state_reg(emit_t *emit, int local_num, int reg_src) {
     if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
         ASM_STORE_REG_REG_OFFSET(emit->as, reg_src, REG_GENERATOR_STATE, local_num);
@@ -710,15 +714,11 @@ STATIC vtype_kind_t load_reg_stack_imm(emit_t *emit, int reg_dest, const stack_i
         if (si->vtype == VTYPE_PYOBJ) {
             ASM_MOV_REG_IMM(emit->as, reg_dest, si->data.u_imm);
         } else if (si->vtype == VTYPE_BOOL) {
-            if (si->data.u_imm == 0) {
-                ASM_MOV_REG_IMM(emit->as, reg_dest, (mp_uint_t)mp_const_false);
-            } else {
-                ASM_MOV_REG_IMM(emit->as, reg_dest, (mp_uint_t)mp_const_true);
-            }
+            emit_native_mov_reg_const(emit, reg_dest, MP_F_CONST_FALSE_OBJ + si->data.u_imm);
         } else if (si->vtype == VTYPE_INT || si->vtype == VTYPE_UINT) {
             ASM_MOV_REG_IMM(emit->as, reg_dest, (uintptr_t)MP_OBJ_NEW_SMALL_INT(si->data.u_imm));
         } else if (si->vtype == VTYPE_PTR_NONE) {
-            ASM_MOV_REG_IMM(emit->as, reg_dest, (mp_uint_t)mp_const_none);
+            emit_native_mov_reg_const(emit, reg_dest, MP_F_CONST_NONE_OBJ);
         } else {
             mp_raise_NotImplementedError("conversion to object");
         }
@@ -1917,7 +1917,7 @@ STATIC void emit_native_unwind_jump(emit_t *emit, mp_uint_t label, mp_uint_t exc
             ASM_MOV_REG_PCREL(emit->as, REG_RET, label & ~MP_EMIT_BREAK_FROM_FOR);
             ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_RET);
             // Cancel any active exception (see also emit_native_pop_except)
-            ASM_MOV_REG_IMM(emit->as, REG_RET, (mp_uint_t)mp_const_none);
+            emit_native_mov_reg_const(emit, REG_RET, MP_F_CONST_NONE_OBJ);
             ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_RET);
             // Jump to the innermost active finally
             label = first_finally->label;
@@ -2013,7 +2013,7 @@ STATIC void emit_native_with_cleanup(emit_t *emit, mp_uint_t label) {
     ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit)); // get exc
 
     // Check if exc is None and jump to non-exc handler if it is
-    ASM_MOV_REG_IMM(emit->as, REG_ARG_2, (mp_uint_t)mp_const_none);
+    emit_native_mov_reg_const(emit, REG_ARG_2, MP_F_CONST_NONE_OBJ);
     ASM_JUMP_IF_REG_EQ(emit->as, REG_ARG_1, REG_ARG_2, *emit->label_slot + 2);
 
     ASM_LOAD_REG_REG_OFFSET(emit->as, REG_ARG_2, REG_ARG_1, 0); // get type(exc)
@@ -2036,7 +2036,7 @@ STATIC void emit_native_with_cleanup(emit_t *emit, mp_uint_t label) {
 
     // Replace exception with None
     emit_native_label_assign(emit, *emit->label_slot);
-    ASM_MOV_REG_IMM(emit->as, REG_TEMP0, (mp_uint_t)mp_const_none);
+    emit_native_mov_reg_const(emit, REG_TEMP0, MP_F_CONST_NONE_OBJ);
     ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_TEMP0);
 
     // end of with cleanup nlr_catch block
@@ -2121,7 +2121,7 @@ STATIC void emit_native_pop_block(emit_t *emit) {
 
 STATIC void emit_native_pop_except(emit_t *emit) {
     // Cancel any active exception so subsequent handlers don't see it
-    ASM_MOV_REG_IMM(emit->as, REG_TEMP0, (mp_uint_t)mp_const_none);
+    emit_native_mov_reg_const(emit, REG_TEMP0, MP_F_CONST_NONE_OBJ);
     ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_TEMP0);
 }
 
@@ -2359,8 +2359,7 @@ STATIC void emit_native_build_slice(emit_t *emit, mp_uint_t 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_uint_t)mp_const_none, REG_ARG_3); // arg3 = step
-        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+        emit_native_mov_reg_const(emit, REG_ARG_3, MP_F_CONST_NONE_OBJ); // arg3 = step
     } else {
         assert(n_args == 3);
         vtype_kind_t vtype_start, vtype_stop, vtype_step;
@@ -2368,9 +2367,9 @@ STATIC void emit_native_build_slice(emit_t *emit, mp_uint_t n_args) {
         assert(vtype_start == VTYPE_PYOBJ);
         assert(vtype_stop == VTYPE_PYOBJ);
         assert(vtype_step == VTYPE_PYOBJ);
-        emit_call(emit, MP_F_NEW_SLICE);
-        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
     }
+    emit_call(emit, MP_F_NEW_SLICE);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
 #endif
 
@@ -2545,7 +2544,7 @@ STATIC void emit_native_return_value(emit_t *emit) {
         if (peek_vtype(emit, 0) == VTYPE_PTR_NONE) {
             emit_pre_pop_discard(emit);
             if (return_vtype == VTYPE_PYOBJ) {
-                ASM_MOV_REG_IMM(emit->as, REG_RET, (mp_uint_t)mp_const_none);
+                emit_native_mov_reg_const(emit, REG_RET, MP_F_CONST_NONE_OBJ);
             } else {
                 ASM_MOV_REG_IMM(emit->as, REG_ARG_1, 0);
             }

py/nativeglue.c

@@ -174,7 +174,10 @@ STATIC bool mp_native_yield_from(mp_obj_t gen, mp_obj_t send_value, mp_obj_t *re
 }
 
 // these must correspond to the respective enum in runtime0.h
-void *const mp_fun_table[MP_F_NUMBER_OF] = {
+const void *const mp_fun_table[MP_F_NUMBER_OF] = {
+    &mp_const_none_obj,
+    &mp_const_false_obj,
+    &mp_const_true_obj,
     mp_convert_obj_to_native,
     mp_convert_native_to_obj,
     mp_native_swap_globals,

py/runtime0.h

@@ -147,7 +147,10 @@ typedef enum {
 } mp_binary_op_t;
 
 typedef enum {
-    MP_F_CONVERT_OBJ_TO_NATIVE = 0,
+    MP_F_CONST_NONE_OBJ = 0,
+    MP_F_CONST_FALSE_OBJ,
+    MP_F_CONST_TRUE_OBJ,
+    MP_F_CONVERT_OBJ_TO_NATIVE,
     MP_F_CONVERT_NATIVE_TO_OBJ,
     MP_F_NATIVE_SWAP_GLOBALS,
     MP_F_LOAD_NAME,
@@ -201,6 +204,6 @@ typedef enum {
     MP_F_NUMBER_OF,
 } mp_fun_kind_t;
 
-extern void *const mp_fun_table[MP_F_NUMBER_OF];
+extern const void *const mp_fun_table[MP_F_NUMBER_OF];
 
 #endif // MICROPY_INCLUDED_PY_RUNTIME0_H