py: Add LOAD_NULL bytecode and use it to simplify function calls.

Adding this bytecode allows to remove 4 others related to
function/method calls with * and ** support.  Will also help with
bytecodes that make functions/closures with default positional and
keyword args.

6 files changed, 44 insertions, 130 deletions

diff --git a/py/bc0.h b/py/bc0.h
index 3d4b106d32..80a8248de7 100644
--- a/py/bc0.h
+++ b/py/bc0.h
@@ -11,6 +11,7 @@
 #define MP_BC_LOAD_CONST_ID      (0x17) // qstr
 #define MP_BC_LOAD_CONST_BYTES   (0x18) // qstr
 #define MP_BC_LOAD_CONST_STRING  (0x19) // qstr
+#define MP_BC_LOAD_NULL          (0x1a)
 
 #define MP_BC_LOAD_FAST_0        (0x20)
 #define MP_BC_LOAD_FAST_1        (0x21)
@@ -84,18 +85,14 @@
 #define MP_BC_YIELD_VALUE        (0x82)
 #define MP_BC_YIELD_FROM         (0x83)
 
-#define MP_BC_MAKE_FUNCTION      (0x90) // uint
-#define MP_BC_MAKE_CLOSURE       (0x91) // uint
-#define MP_BC_CALL_FUNCTION      (0x92) // uint
-#define MP_BC_CALL_FUNCTION_VAR  (0x93) // uint
-#define MP_BC_CALL_FUNCTION_KW   (0x94) // uint
-#define MP_BC_CALL_FUNCTION_VAR_KW   (0x95) // uint
-#define MP_BC_CALL_METHOD        (0x96) // uint
-#define MP_BC_CALL_METHOD_VAR    (0x97) // uint
-#define MP_BC_CALL_METHOD_KW     (0x98) // uint
-#define MP_BC_CALL_METHOD_VAR_KW (0x99) // uint
-#define MP_BC_MAKE_FUNCTION_DEFARGS  (0x9a) // uint
-#define MP_BC_MAKE_CLOSURE_DEFARGS   (0x9b) // uint
+#define MP_BC_MAKE_FUNCTION         (0x90) // uint
+#define MP_BC_MAKE_FUNCTION_DEFARGS (0x91) // uint
+#define MP_BC_MAKE_CLOSURE          (0x92) // uint
+#define MP_BC_MAKE_CLOSURE_DEFARGS  (0x93) // uint
+#define MP_BC_CALL_FUNCTION         (0x94) // uint
+#define MP_BC_CALL_FUNCTION_VAR_KW  (0x95) // uint
+#define MP_BC_CALL_METHOD           (0x96) // uint
+#define MP_BC_CALL_METHOD_VAR_KW    (0x97) // uint
 
 #define MP_BC_IMPORT_NAME        (0xe0) // qstr
 #define MP_BC_IMPORT_FROM        (0xe1) // qstr
diff --git a/py/emitbc.c b/py/emitbc.c
index a149582c0d..595c7ac196 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -399,6 +399,11 @@ STATIC void emit_bc_load_const_verbatim_str(emit_t *emit, const char *str) {
     assert(0);
 }
 
+STATIC void emit_bc_load_null(emit_t *emit) {
+    emit_bc_pre(emit, 1);
+    emit_write_byte_code_byte(emit, MP_BC_LOAD_NULL);
+};
+
 STATIC void emit_bc_load_fast(emit_t *emit, qstr qstr, int local_num) {
     assert(local_num >= 0);
     emit_bc_pre(emit, 1);
@@ -748,56 +753,30 @@ STATIC void emit_bc_make_closure(emit_t *emit, scope_t *scope, uint n_pos_defaul
     }
 }
 
-STATIC void emit_bc_call_function(emit_t *emit, int n_positional, int n_keyword, bool have_star_arg, bool have_dbl_star_arg) {
-    int s = 0;
-    if (have_star_arg) {
-        s += 1;
-    }
-    if (have_dbl_star_arg) {
-        s += 1;
-    }
-    emit_bc_pre(emit, -n_positional - 2 * n_keyword - s);
-    int op;
-    if (have_star_arg) {
-        if (have_dbl_star_arg) {
-            op = MP_BC_CALL_FUNCTION_VAR_KW;
-        } else {
-            op = MP_BC_CALL_FUNCTION_VAR;
+STATIC void emit_bc_call_function_method_helper(emit_t *emit, int stack_adj, uint bytecode_base, int n_positional, int n_keyword, bool have_star_arg, bool have_dbl_star_arg) {
+    if (have_star_arg || have_dbl_star_arg) {
+        if (!have_star_arg) {
+            // load dummy entry for non-existent pos_seq
+            emit_bc_load_null(emit);
+            emit_bc_rot_two(emit);
+        } else if (!have_dbl_star_arg) {
+            // load dummy entry for non-existent kw_dict
+            emit_bc_load_null(emit);
         }
+        emit_bc_pre(emit, stack_adj - n_positional - 2 * n_keyword - 2);
+        emit_write_byte_code_byte_uint(emit, bytecode_base + 1, (n_keyword << 8) | n_positional); // TODO make it 2 separate uints?
     } else {
-        if (have_dbl_star_arg) {
-            op = MP_BC_CALL_FUNCTION_KW;
-        } else {
-            op = MP_BC_CALL_FUNCTION;
-        }
+        emit_bc_pre(emit, stack_adj - n_positional - 2 * n_keyword);
+        emit_write_byte_code_byte_uint(emit, bytecode_base, (n_keyword << 8) | n_positional); // TODO make it 2 separate uints?
     }
-    emit_write_byte_code_byte_uint(emit, op, (n_keyword << 8) | n_positional); // TODO make it 2 separate uints
+}
+
+STATIC void emit_bc_call_function(emit_t *emit, int n_positional, int n_keyword, bool have_star_arg, bool have_dbl_star_arg) {
+    emit_bc_call_function_method_helper(emit, 0, MP_BC_CALL_FUNCTION, n_positional, n_keyword, have_star_arg, have_dbl_star_arg);
 }
 
 STATIC void emit_bc_call_method(emit_t *emit, int n_positional, int n_keyword, bool have_star_arg, bool have_dbl_star_arg) {
-    int s = 0;
-    if (have_star_arg) {
-        s += 1;
-    }
-    if (have_dbl_star_arg) {
-        s += 1;
-    }
-    emit_bc_pre(emit, -1 - n_positional - 2 * n_keyword - s);
-    int op;
-    if (have_star_arg) {
-        if (have_dbl_star_arg) {
-            op = MP_BC_CALL_METHOD_VAR_KW;
-        } else {
-            op = MP_BC_CALL_METHOD_VAR;
-        }
-    } else {
-        if (have_dbl_star_arg) {
-            op = MP_BC_CALL_METHOD_KW;
-        } else {
-            op = MP_BC_CALL_METHOD;
-        }
-    }
-    emit_write_byte_code_byte_uint(emit, op, (n_keyword << 8) | n_positional); // TODO make it 2 separate uints
+    emit_bc_call_function_method_helper(emit, -1, MP_BC_CALL_METHOD, n_positional, n_keyword, have_star_arg, have_dbl_star_arg);
 }
 
 STATIC void emit_bc_return_value(emit_t *emit) {
diff --git a/py/runtime.c b/py/runtime.c
index 4898864962..7e02879455 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -505,7 +505,7 @@ mp_obj_t mp_call_method_n_kw(uint n_args, uint n_kw, const mp_obj_t *args) {
     return mp_call_function_n_kw(args[0], n_args + adjust, n_kw, args + 2 - adjust);
 }
 
-mp_obj_t mp_call_method_n_kw_var(bool have_self, uint n_args_n_kw, const mp_obj_t *args, mp_obj_t pos_seq, mp_obj_t kw_dict) {
+mp_obj_t mp_call_method_n_kw_var(bool have_self, uint n_args_n_kw, const mp_obj_t *args) {
     mp_obj_t fun = *args++;
     mp_obj_t self = MP_OBJ_NULL;
     if (have_self) {
@@ -513,6 +513,8 @@ mp_obj_t mp_call_method_n_kw_var(bool have_self, uint n_args_n_kw, const mp_obj_
     }
     uint n_args = n_args_n_kw & 0xff;
     uint n_kw = (n_args_n_kw >> 8) & 0xff;
+    mp_obj_t pos_seq = args[n_args + 2 * n_kw]; // map be MP_OBJ_NULL
+    mp_obj_t kw_dict = args[n_args + 2 * n_kw + 1]; // map be MP_OBJ_NULL
 
     DEBUG_OP_printf("call method var (fun=%p, self=%p, n_args=%u, n_kw=%u, args=%p, seq=%p, dict=%p)\n", fun, self, n_args, n_kw, args, pos_seq, kw_dict);
 
diff --git a/py/runtime.h b/py/runtime.h
index f79cb2e306..d71e045b01 100644
--- a/py/runtime.h
+++ b/py/runtime.h
@@ -43,7 +43,7 @@ mp_obj_t mp_call_function_2(mp_obj_t fun, mp_obj_t arg1, mp_obj_t arg2);
 mp_obj_t mp_call_function_n_kw_for_native(mp_obj_t fun_in, uint n_args_kw, const mp_obj_t *args);
 mp_obj_t mp_call_function_n_kw(mp_obj_t fun, uint n_args, uint n_kw, const mp_obj_t *args);
 mp_obj_t mp_call_method_n_kw(uint n_args, uint n_kw, const mp_obj_t *args);
-mp_obj_t mp_call_method_n_kw_var(bool have_self, uint n_args_n_kw, const mp_obj_t *args, mp_obj_t pos_seq, mp_obj_t kw_dict);
+mp_obj_t mp_call_method_n_kw_var(bool have_self, uint n_args_n_kw, const mp_obj_t *args);
 
 mp_obj_t mp_build_tuple(int n_args, mp_obj_t *items);
 mp_obj_t mp_build_list(int n_args, mp_obj_t *items);
diff --git a/py/showbc.c b/py/showbc.c
index 10b3e7490d..823769c0ef 100644
--- a/py/showbc.c
+++ b/py/showbc.c
@@ -399,16 +399,6 @@ void mp_byte_code_print(const byte *ip, int len) {
                 printf("CALL_FUNCTION n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
                 break;
 
-            case MP_BC_CALL_FUNCTION_VAR:
-                DECODE_UINT;
-                printf("CALL_FUNCTION_VAR n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
-                break;
-
-            case MP_BC_CALL_FUNCTION_KW:
-                DECODE_UINT;
-                printf("CALL_FUNCTION_KW n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
-                break;
-
             case MP_BC_CALL_FUNCTION_VAR_KW:
                 DECODE_UINT;
                 printf("CALL_FUNCTION_VAR_KW n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
@@ -419,16 +409,6 @@ void mp_byte_code_print(const byte *ip, int len) {
                 printf("CALL_METHOD n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
                 break;
 
-            case MP_BC_CALL_METHOD_VAR:
-                DECODE_UINT;
-                printf("CALL_METHOD_VAR n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
-                break;
-
-            case MP_BC_CALL_METHOD_KW:
-                DECODE_UINT;
-                printf("CALL_METHOD_KW n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
-                break;
-
             case MP_BC_CALL_METHOD_VAR_KW:
                 DECODE_UINT;
                 printf("CALL_METHOD_VAR_KW n=" UINT_FMT " nkw=" UINT_FMT, unum & 0xff, (unum >> 8) & 0xff);
diff --git a/py/vm.c b/py/vm.c
index edcad39565..599a1d862e 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -220,6 +220,10 @@ dispatch_loop:
                         PUSH(mp_load_const_str(qst));
                         break;
 
+                    case MP_BC_LOAD_NULL:
+                        PUSH(MP_OBJ_NULL);
+                        break;
+
                     case MP_BC_LOAD_FAST_0:
                         PUSH(fastn[0]);
                         break;
@@ -671,38 +675,14 @@ unwind_jump:
                         SET_TOP(mp_call_function_n_kw(*sp, unum & 0xff, (unum >> 8) & 0xff, sp + 1));
                         break;
 
-                    case MP_BC_CALL_FUNCTION_VAR:
-                        DECODE_UINT;
-                        // unum & 0xff == n_positional
-                        // (unum >> 8) & 0xff == n_keyword
-                        // We have folowing stack layout here:
-                        // fun arg0 arg1 ... kw0 val0 kw1 val1 ... seq <- TOS
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe);
-                        SET_TOP(mp_call_method_n_kw_var(false, unum, sp, obj1, MP_OBJ_NULL));
-                        break;
-
-                    case MP_BC_CALL_FUNCTION_KW:
-                        DECODE_UINT;
-                        // unum & 0xff == n_positional
-                        // (unum >> 8) & 0xff == n_keyword
-                        // We have folowing stack layout here:
-                        // fun arg0 arg1 ... kw0 val0 kw1 val1 ... dict <- TOS
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe);
-                        SET_TOP(mp_call_method_n_kw_var(false, unum, sp, MP_OBJ_NULL, obj1));
-                        break;
-
                     case MP_BC_CALL_FUNCTION_VAR_KW:
                         DECODE_UINT;
                         // unum & 0xff == n_positional
                         // (unum >> 8) & 0xff == n_keyword
                         // We have folowing stack layout here:
                         // fun arg0 arg1 ... kw0 val0 kw1 val1 ... seq dict <- TOS
-                        obj2 = POP();
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe);
-                        SET_TOP(mp_call_method_n_kw_var(false, unum, sp, obj1, obj2));
+                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 2;
+                        SET_TOP(mp_call_method_n_kw_var(false, unum, sp));
                         break;
 
                     case MP_BC_CALL_METHOD:
@@ -713,38 +693,14 @@ unwind_jump:
                         SET_TOP(mp_call_method_n_kw(unum & 0xff, (unum >> 8) & 0xff, sp));
                         break;
 
-                    case MP_BC_CALL_METHOD_VAR:
-                        DECODE_UINT;
-                        // unum & 0xff == n_positional
-                        // (unum >> 8) & 0xff == n_keyword
-                        // We have folowing stack layout here:
-                        // fun self arg0 arg1 ... kw0 val0 kw1 val1 ... seq <- TOS
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 1;
-                        SET_TOP(mp_call_method_n_kw_var(true, unum, sp, obj1, MP_OBJ_NULL));
-                        break;
-
-                    case MP_BC_CALL_METHOD_KW:
-                        DECODE_UINT;
-                        // unum & 0xff == n_positional
-                        // (unum >> 8) & 0xff == n_keyword
-                        // We have folowing stack layout here:
-                        // fun self arg0 arg1 ... kw0 val0 kw1 val1 ... dict <- TOS
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 1;
-                        SET_TOP(mp_call_method_n_kw_var(true, unum, sp, MP_OBJ_NULL, obj1));
-                        break;
-
                     case MP_BC_CALL_METHOD_VAR_KW:
                         DECODE_UINT;
                         // unum & 0xff == n_positional
                         // (unum >> 8) & 0xff == n_keyword
                         // We have folowing stack layout here:
                         // fun self arg0 arg1 ... kw0 val0 kw1 val1 ... seq dict <- TOS
-                        obj2 = POP();
-                        obj1 = POP();
-                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 1;
-                        SET_TOP(mp_call_method_n_kw_var(true, unum, sp, obj1, obj2));
+                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 3;
+                        SET_TOP(mp_call_method_n_kw_var(true, unum, sp));
                         break;
 
                     case MP_BC_RETURN_VALUE: