[libclc] [libclc] Optimize ceil/fabs/floor/rint/trunc (PR #119596)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> which in its header uses this strange __asm__ method of calling LLVM intrinsics directly.

That's something that's always surprised me it works. It's rather unsafe (you can bypass immarg validation for instance). Plus asm callsites get infected with overly conservative attributes (like convergent, which you can't remove)

https://github.com/llvm/llvm-project/pull/119596