py: Add load_const_obj to emitter, add LOAD_CONST_OBJ to bytecode.

This allows to directly load a Python object to the Python stack.  See
issue #722 for background.

py/bc0.h

@@ -38,6 +38,7 @@
 #define MP_BC_LOAD_CONST_DEC     (0x16) // qstr
 #define MP_BC_LOAD_CONST_BYTES   (0x17) // qstr
 #define MP_BC_LOAD_CONST_STRING  (0x18) // qstr
+#define MP_BC_LOAD_CONST_OBJ     (0x09) // ptr; TODO renumber to be in order
 #define MP_BC_LOAD_NULL          (0x19)
 
 #define MP_BC_LOAD_FAST_N        (0x1a) // uint

py/emit.h

@@ -80,6 +80,7 @@ typedef struct _emit_method_table_t {
     void (*load_const_int)(emit_t *emit, qstr qst);
     void (*load_const_dec)(emit_t *emit, qstr qst);
     void (*load_const_str)(emit_t *emit, qstr qst, bool bytes);
+    void (*load_const_obj)(emit_t *emit, void *obj);
     void (*load_null)(emit_t *emit);
     void (*load_fast)(emit_t *emit, qstr qst, mp_uint_t id_flags, mp_uint_t local_num);
     void (*load_deref)(emit_t *emit, qstr qst, mp_uint_t local_num);

py/emitbc.c

@@ -487,6 +487,11 @@ STATIC void emit_bc_load_const_str(emit_t *emit, qstr qst, bool bytes) {
     }
 }
 
+STATIC void emit_bc_load_const_obj(emit_t *emit, void *obj) {
+    emit_bc_pre(emit, 1);
+    emit_write_bytecode_byte_ptr(emit, MP_BC_LOAD_CONST_OBJ, obj);
+}
+
 STATIC void emit_bc_load_null(emit_t *emit) {
     emit_bc_pre(emit, 1);
     emit_write_bytecode_byte(emit, MP_BC_LOAD_NULL);
@@ -917,6 +922,7 @@ const emit_method_table_t emit_bc_method_table = {
     emit_bc_load_const_int,
     emit_bc_load_const_dec,
     emit_bc_load_const_str,
+    emit_bc_load_const_obj,
     emit_bc_load_null,
     emit_bc_load_fast,
     emit_bc_load_deref,

py/emitcpy.c

@@ -231,6 +231,15 @@ STATIC void emit_cpy_load_const_str(emit_t *emit, qstr qst, bool bytes) {
     }
 }
 
+STATIC void emit_cpy_load_const_obj(emit_t *emit, void *obj) {
+    emit_pre(emit, 1, 3);
+    if (emit->pass == MP_PASS_EMIT) {
+        printf("LOAD_CONST ");
+        mp_obj_print(obj, PRINT_REPR);
+        printf("\n");
+    }
+}
+
 STATIC void emit_cpy_load_null(emit_t *emit) {
     // unused for cpy
     assert(0);
@@ -833,6 +842,7 @@ const emit_method_table_t emit_cpython_method_table = {
     emit_cpy_load_const_int,
     emit_cpy_load_const_dec,
     emit_cpy_load_const_str,
+    emit_cpy_load_const_obj,
     emit_cpy_load_null,
     emit_cpy_load_fast,
     emit_cpy_load_deref,

py/emitnative.c

@@ -1172,6 +1172,12 @@ STATIC void emit_native_load_const_str(emit_t *emit, qstr qst, bool bytes) {
     }
 }
 
+STATIC void emit_native_load_const_obj(emit_t *emit, void *obj) {
+    emit_native_pre(emit);
+    ASM_MOV_ALIGNED_IMM_TO_REG(emit->as, (mp_uint_t)obj, REG_RET);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
 STATIC void emit_native_load_null(emit_t *emit) {
     emit_native_pre(emit);
     emit_post_push_imm(emit, VTYPE_PYOBJ, 0);
@@ -2274,6 +2280,7 @@ const emit_method_table_t EXPORT_FUN(method_table) = {
     emit_native_load_const_int,
     emit_native_load_const_dec,
     emit_native_load_const_str,
+    emit_native_load_const_obj,
     emit_native_load_null,
     emit_native_load_fast,
     emit_native_load_deref,

py/emitpass1.c

@@ -190,6 +190,7 @@ const emit_method_table_t emit_pass1_method_table = {
     (void*)emit_pass1_dummy,
     (void*)emit_pass1_dummy,
     (void*)emit_pass1_dummy,
+    (void*)emit_pass1_dummy,
     #if MICROPY_PY_BUILTINS_SET
     (void*)emit_pass1_dummy,
     (void*)emit_pass1_dummy,

py/vm.c

@@ -224,6 +224,12 @@ dispatch_loop:
                     DISPATCH();
                 }
 
+                ENTRY(MP_BC_LOAD_CONST_OBJ): {
+                    DECODE_PTR;
+                    PUSH(ptr);
+                    DISPATCH();
+                }
+
                 ENTRY(MP_BC_LOAD_NULL):
                     PUSH(MP_OBJ_NULL);
                     DISPATCH();

py/vmentrytable.h

@@ -40,6 +40,7 @@ static void* entry_table[256] = {
     [MP_BC_LOAD_CONST_DEC] = &&entry_MP_BC_LOAD_CONST_DEC,
     [MP_BC_LOAD_CONST_BYTES] = &&entry_MP_BC_LOAD_CONST_BYTES,
     [MP_BC_LOAD_CONST_STRING] = &&entry_MP_BC_LOAD_CONST_STRING,
+    [MP_BC_LOAD_CONST_OBJ] = &&entry_MP_BC_LOAD_CONST_OBJ,
     [MP_BC_LOAD_NULL] = &&entry_MP_BC_LOAD_NULL,
     [MP_BC_LOAD_FAST_N] = &&entry_MP_BC_LOAD_FAST_N,
     [MP_BC_LOAD_DEREF] = &&entry_MP_BC_LOAD_DEREF,