Hi,

This is a partial optimization for PR103855.

Initially, I looked into optimizing RTL generation or a more complex
GIMPLE transformation so that we could optimize other cases as well,
such as ((unsigned long long) short / int).

However, that is a bit too complex for now. While I continue to look
into that change, I've decided to implement this simpler match.pd
transformation.

Greatly appreciate any feedback on this patch or guidance for
implementing the more advanced optimizations!

Thanks,
Zhao Wei