[Bug target/123838] riscv: Optimize int shift left by (31 - n).

[law at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123838

--- Comment #1 from Jeffrey A. Law <law at gcc dot gnu.org> ---
I'm not aware of a bug for this on riscv.  It feels like this should be
addressed in simplify-rtx if we can given it's generic enough.