[llvm] [RISCV][GISel] Use libcalls for rint, nearbyint, trunc, round, and roundeven intrinsics. (PR #108779)

[Craig Topper via llvm-commits]

topperc wrote:

> I cannot say much, but the title slightly differs from what you actually legalize, but so what. 4 vs. 5 and some missing fs.

I wrote them in terms of their C and IR names rather than the mishmash we have in G_ node names.

https://github.com/llvm/llvm-project/pull/108779