ops.h: update OP_ARYDUP instruction and rename to OP_ARYSPLAT.

Transforms the value of a splat inside a return statement (similar
to an array). For example, `return *nil` should return `nil.to_a`,
while `return *1` should return `[1]`

src/codedump.c

@@ -476,8 +476,8 @@ codedump(mrb_state *mrb, const mrb_irep *irep)
       printf("ARYPUSH\tR%d\t%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ARYDUP, B):
-      printf("ARYDUP\tR%d\t", a);
+    CASE(OP_ARYSPLAT, B):
+      printf("ARYSPLAT\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
     CASE(OP_AREF, BBB):

src/vm.c

@@ -2748,15 +2748,10 @@ RETRY_TRY_BLOCK:
       NEXT;
     }
 
-    CASE(OP_ARYDUP, B) {
-      mrb_value ary = regs[a];
-      if (mrb_array_p(ary)) {
-        ary = mrb_ary_new_from_values(mrb, RARRAY_LEN(ary), RARRAY_PTR(ary));
-      }
-      else {
-        ary = mrb_ary_new_from_values(mrb, 1, &ary);
-      }
+    CASE(OP_ARYSPLAT, B) {
+      mrb_value ary = mrb_ary_splat(mrb, regs[a]);
       regs[a] = ary;
+      mrb_gc_arena_restore(mrb, ai);
       NEXT;
     }