Add a newmixintype op

A form of `newtype` that sets a flag saying that this type can be the
target of a mixin. Added as a new op used at type creation time so that
we can easily reason about a type always having that property for its
lifetime, rather than any timing worries about it being set later. This
alone doesn't do anything useful; the useful part will be when we start
to enforce its usage and then introduce new ops that avoid the whole
"look at real_data" dance in P6opaque attribute access, which it seems
can save us around 4 CPU instructions per attribute read/write. Which,
given we do a lot of those - Perl 6 is full of objects - is potentially
going to be a measurable improvement.

lib/MAST/Ops.nqp

@@ -2628,7 +2628,7 @@ BEGIN {
     65,
     58,
     57,
-    65,
+    66,
     65,
     57,
     66,
@@ -4125,7 +4125,7 @@ BEGIN {
     'popcompsc', 411,
     'scgetdesc', 412,
     'loadbytecode', 413,
-    'DEPRECATED_1', 414,
+    'newmixintype', 414,
     'DEPRECATED_2', 415,
     'iscompunit', 416,
     'compunitmainline', 417,
@@ -4944,7 +4944,7 @@ BEGIN {
     'popcompsc',
     'scgetdesc',
     'loadbytecode',
-    'DEPRECATED_1',
+    'newmixintype',
     'DEPRECATED_2',
     'iscompunit',
     'compunitmainline',
@@ -8563,7 +8563,7 @@ BEGIN {
         my uint $index0 := nqp::unbox_u($op0); nqp::writeuint($bytecode, nqp::add_i($elems, 2), $index0, 5);
         my uint $index1 := nqp::unbox_u($op1); nqp::writeuint($bytecode, nqp::add_i($elems, 4), $index1, 5);
     },
-    'DEPRECATED_1', sub ($op0, $op1, $op2) {
+    'newmixintype', sub ($op0, $op1, $op2) {
         my $bytecode := $*MAST_FRAME.bytecode;
         my uint $elems := nqp::elems($bytecode);
         nqp::writeuint($bytecode, $elems, 414, 5);

src/6model/6model.h

@@ -371,6 +371,10 @@ struct MVMSTable {
     /* If this STable is currently in the process of being repossessed. Used
      * to trigger clearup of memory pre-repossession. */
     MVMuint8 being_repossessed;
+
+    /* If this STable represents a type that can be the target of a
+     * change_type - that is to say, it's been mixed in to. */
+    MVMuint8 is_mixin_type;
 };
 
 /* The representation operations table. Note that representations are not

src/6model/serialization.c

@@ -10,7 +10,7 @@
 
 /* Version of the serialization format that we are currently at and lowest
  * version we support. */
-#define CURRENT_VERSION 20
+#define CURRENT_VERSION 21
 #define MIN_VERSION     16
 
 /* Various sizes (in bytes). */
@@ -1172,6 +1172,7 @@ static void serialize_stable(MVMThreadContext *tc, MVMSerializationWriter *write
     }
 
     MVM_serialization_write_cstr(tc, writer, MVM_6model_get_stable_debug_name(tc, st));
+    MVM_serialization_write_int(tc, writer, st->is_mixin_type);
 
     /* Store offset we save REPR data at. */
     write_int32(writer->root.stables_table, offset + 8, writer->stables_data_offset);
@@ -2713,7 +2714,10 @@ static void deserialize_stable(MVMThreadContext *tc, MVMSerializationReader *rea
     if (reader->root.version >= 18) {
         st->debug_name = MVM_serialization_read_cstr(tc, reader);
     } else {
-        st->debug_name = 0;
+        st->debug_name = NULL;
+    }
+    if (reader->root.version >= 21) {
+        st->is_mixin_type = MVM_serialization_read_int(tc, reader);
     }
 
     /* If the REPR has a function to deserialize representation data, call it. */

src/core/interp.c

@@ -3211,6 +3211,16 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
                 MVM_load_bytecode(tc, filename);
                 goto NEXT;
             }
+            OP(newmixintype): {
+                MVMObject *how = GET_REG(cur_op, 2).o;
+                MVMString *repr_name = GET_REG(cur_op, 4).s;
+                const MVMREPROps *repr = MVM_repr_get_by_name(tc, repr_name);
+                MVMObject *type = repr->type_object_for(tc, how);
+                STABLE(type)->is_mixin_type = 1;
+                GET_REG(cur_op, 0).o = type;
+                cur_op += 6;
+                goto NEXT;
+            }
             OP(iscompunit): {
                 MVMObject *maybe_cu = GET_REG(cur_op, 2).o;
                 GET_REG(cur_op, 0).i64 = REPR(maybe_cu)->ID == MVM_REPR_ID_MVMCompUnit;
@@ -6342,7 +6352,6 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
             }
             /* The compiler compiles faster if all deprecated are together and at the end
              * even though the op numbers are technically out of order. */
-            OP(DEPRECATED_1):
             OP(DEPRECATED_2):
                 MVM_exception_throw_adhoc(tc, "The mastto* ops were removed in MoarVM 2018.01.");
             OP(DEPRECATED_4):

src/core/oplabels.h

@@ -415,7 +415,7 @@ static const void * const LABELS[] = {
     &&OP_popcompsc,
     &&OP_scgetdesc,
     &&OP_loadbytecode,
-    &&OP_DEPRECATED_1,
+    &&OP_newmixintype,
     &&OP_DEPRECATED_2,
     &&OP_iscompunit,
     &&OP_compunitmainline,

src/core/oplist

@@ -471,7 +471,7 @@ pushcompsc          r(obj)
 popcompsc           w(obj)
 scgetdesc           w(str) r(obj)
 loadbytecode        w(str) r(str) :invokish :maycausedeopt :noinline
-DEPRECATED_1        r(obj) r(obj) r(str)
+newmixintype        w(obj) r(obj) r(str)
 DEPRECATED_2        w(obj) r(obj) r(obj) :invokish :maycausedeopt
 iscompunit          w(int64) r(obj) :pure
 compunitmainline    w(obj) r(obj)

src/core/ops.c

@@ -6208,8 +6208,8 @@ static const MVMOpInfo MVM_op_infos[] = {
         { MVM_operand_write_reg | MVM_operand_str, MVM_operand_read_reg | MVM_operand_str }
     },
     {
-        MVM_OP_DEPRECATED_1,
-        "DEPRECATED_1",
+        MVM_OP_newmixintype,
+        "newmixintype",
         "  ",
         3,
         0,
@@ -6220,7 +6220,7 @@ static const MVMOpInfo MVM_op_infos[] = {
         0,
         0,
         0,
-        { MVM_operand_read_reg | MVM_operand_obj, MVM_operand_read_reg | MVM_operand_obj, MVM_operand_read_reg | MVM_operand_str }
+        { MVM_operand_write_reg | MVM_operand_obj, MVM_operand_read_reg | MVM_operand_obj, MVM_operand_read_reg | MVM_operand_str }
     },
     {
         MVM_OP_DEPRECATED_2,

src/core/ops.h

@@ -415,7 +415,7 @@
 #define MVM_OP_popcompsc 411
 #define MVM_OP_scgetdesc 412
 #define MVM_OP_loadbytecode 413
-#define MVM_OP_DEPRECATED_1 414
+#define MVM_OP_newmixintype 414
 #define MVM_OP_DEPRECATED_2 415
 #define MVM_OP_iscompunit 416
 #define MVM_OP_compunitmainline 417