[llvm] [RISCV] Remove setJumpIsExpensive(). (PR #74647)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

> > How about adding it to `RISCVSubtarget` and changing it to something like:
> > ```c
> > setJumpIsExpensive(Subtarget.isJumpExpensive())
> > ```
> > So that processors can tune it.
> 
> Do you have a target where you actively want to support that configuration? I agree this is something that could be made configurable, but we're probably best off focusing our efforts around a smaller set of configuration options unless we know there's a case where we really need to diverge.
No, I don't have actually, but some downstream optimizations are based on the assumption that we have `setJumpIsExpensive(true)`. I'm not opposed to this change, it just makes me nervous about the breakage of some previous optimizations.

https://github.com/llvm/llvm-project/pull/74647