[llvm] [GISel][RISCV] Legalize `G_FREM` to use fmod (PR #93063)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> > > > > It should be possible to test the scalarize case
> > > > 
> > > > 
> > > > I tried the following 4 variants, but no one works :(
> > > 
> > > 
> > > This is the case where MIR tests are useful because you don't have to bring up all the other parts
> > 
> > 
> > These MIR tests don't work:
> > ```
> > ---
> > name:            frem_v2f32
> > body:             |
> >   bb.0.entry:
> >     ; unable to legalize instruction: %3:_(s32), %4:_(s32) = G_UNMERGE_VALUES %0:_(<2 x s32>)
> > ```
> 
> If you use -global-isel-abort=0 or 2, you can check the partially legalized output

Done. Thank you!

https://github.com/llvm/llvm-project/pull/93063