Revert "Refactor to reduce "swap" instruction of pattern matching"

This reverts commit 3a4be42.

To fix following warning:

```
compiling ../compile.c
../compile.c:6336:20: warning: variable 'line' is uninitialized when used here [-Wuninitialized]
    ADD_INSN(head, line, putnil); /* allocate stack for cached #deconstruct value */
                   ^~~~
../compile.c:220:57: note: expanded from macro 'ADD_INSN'
  ADD_ELEM((seq), (LINK_ELEMENT *) new_insn_body(iseq, (line), BIN(insn), 0))
                                                        ^~~~
../compile.c:6327:13: note: initialize the variable 'line' to silence this warning
    int line;
            ^
             = 0
1 warning generated.
```

compile.c

@@ -6333,7 +6333,6 @@ compile_case3(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const orig_no
     INIT_ANCHOR(body_seq);
     INIT_ANCHOR(cond_seq);
 
-    ADD_INSN(head, line, putnil); /* allocate stack for cached #deconstruct value */
     CHECK(COMPILE(head, "case base", node->nd_head));
 
     branches = decl_branch_base(iseq, node, "case");
@@ -6346,6 +6345,8 @@ compile_case3(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const orig_no
     endlabel = NEW_LABEL(line);
     elselabel = NEW_LABEL(line);
 
+    ADD_INSN(head, line, putnil); /* allocate stack for cached #deconstruct value */
+    ADD_INSN(head, line, swap);
     ADD_SEQ(ret, head);	/* case VAL */
 
     while (type == NODE_IN) {