[llvm] [RISCV] Add TuneJumpIsExpensive (PR #191374)

[Craig Topper via llvm-commits]

topperc wrote:

> > > > What is the advantage of a tuning flag given that we already have `-mllvm -jump-is-expensive`?
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> > > using `-mllvm <whatever>` flags does not interact well with LTO, it would be better to have this as a feature or some other kind of attribute.
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> > For LTO, we can pass options via `clang -flto -Wl,-mllvm,-<llvm-backend-option> ...`.
> 
> This applies the setting to the whole link, with a feature it can be on a per-function/per-file basis, even during linking.

Does clang allow tune features on a function or just extensions?

https://github.com/llvm/llvm-project/pull/191374