[llvm-branch-commits] [libcxx] [libc] [flang] [llvm] [clang] [compiler-rt] [RISCV] Support select optimization (PR #80124)

[Wang Pengcheng via llvm-branch-commits]

https://github.com/wangpc-pp created https://github.com/llvm/llvm-project/pull/80124

AArch64 has enabled this in https://reviews.llvm.org/D138990, and
the measurement data still stands for RISCV.

And, similar optimization like #77284 is added too.