codegen.c: peephole optimize `OP_MOVE` after `OP_ARRAY` or `OP_HASH`.

When the length operand is zero, we don't need `OP_MOVE` but adjust the
destination operand instead.

mrbgems/mruby-compiler/core/codegen.c

@@ -594,6 +594,9 @@ gen_move(codegen_scope *s, uint16_t dst, uint16_t src, int nopeep)
       rewind_pc(s);
       genop_1(s, data.insn, dst);
       return;
+    case OP_HASH: case OP_ARRAY:
+      if (data.b != 0) goto normal;
+      /* fall through */
     case OP_LOADI: case OP_LOADINEG:
     case OP_LOADL: case OP_LOADSYM:
     case OP_GETGV: case OP_GETSV: case OP_GETIV: case OP_GETCV: