Run mem in simulator may be occurs segments fault. This cl to fix it.
If value of reg is small int, it should be smi.

Change-Id: I60b4eb8c959bc9f86ae28718ff6dd54ecf40a6ec
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3698757
Auto-Submit: Yahan Lu <yahan@iscas.ac.cn>
Commit-Queue: ji qiu <qiuji@iscas.ac.cn>
Reviewed-by: ji qiu <qiuji@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#81061}