[Bug target/117599] LoongArch support for BitInt

[yangyujie at loongson dot cn via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117599

--- Comment #11 from Yang Yujie <yangyujie at loongson dot cn> ---
Sorry for only testing with --enable-checking=release.

Here's a patch.