[llvm] [RISCV][GlobalISel] Legalize G_ADD, G_SUB, G_AND, G_OR, G_XOR on RISC-V Vector Extension (PR #71400)

[Craig Topper via llvm-commits]

topperc wrote:

> > Given different conditions
> > > nxv1s64, nxv2s64, nxv4s64, nxv8s64 require hasVInstructionsI64 instead of hasVInstructions
> > 
> > 
> > > nxv1s8, nxv1s16, nxv1s32 require Subtarget.getELen() == 64
> > 
> > 
> > I have this literal implementation locally:
> > ```c++
> > getActionDefinitionsBuilder({G_ADD, G_SUB, G_AND, G_OR, G_XOR})
> >         .legalFor({s32, sXLen})
> >         .legalFor(ST.hasVInstructions()
> >                       ? std::initializer_list<LLT>{nxv2s8, nxv4s8, nxv8s8,
> >                                                    nxv16s8, nxv32s8, nxv64s8,
> >                                                    nxv2s16, nxv4s16, nxv8s16,
> >                                                    nxv16s16, nxv32s16, nxv2s32,
> >                                                    nxv4s32, nxv8s32, nxv16s32}
> >                       : std::initializer_list<LLT>())
> >         .legalFor(
> >             ST.hasVInstructionsI64()
> >                 ? std::initializer_list<LLT>{nxv1s64, nxv2s64, nxv4s64, nxv8s64}
> >                 : std::initializer_list<LLT>())
> >         .legalFor(ST.getELen() == 64
> >                       ? std::initializer_list<LLT>{nxv1s8, nxv1s16, nxv1s32}
> >                       : std::initializer_list<LLT>())
> >         .widenScalarToNextPow2(0)
> >         .clampScalar(0, s32, sXLen);
> > ```
> > 
> > 
> >     
> >       
> >     
> > 
> >       
> >     
> > 
> >     
> >   
> > Please point out any issue this code snippet has.
> 
> This LGTM.
> 
> > In addition, it has to have fragments of `AllVecTys`, so I was wondering, as per @michaelmaitland 's review:
> > > In any case, I'd like to have AllVecTys exist so it can be reused by future patches.
> > 
> > 
> > Shall we still be declaring `AllVecTys`? It's good to declare it because it's likely to be reused, what if future patches also need the aforementioned condition checking so it won't be reused as a whole, is it still worth it?
> 
> Since we are not using AllVecTys, I think we should not include this variable. The compiler would emit a warning for an unused variable, and we don't want that. I think you should make this change and bring this PR out of draft, marking it ready for review!

Something like this could work.

```
.legalFor([=, &ST](const LegalityQuery &Query) {
  return Subtarget.hasVInstruction() && typeInSet(0, AllVecTys)(Query) &&
             (Query.Types[0].getScalarSize() != 64 || Subtarget.hasVInstruction64()) &&
             (Query.Types[0].getElementCount().getKnownMinValue() != 1 || Subtarget.getELEN() == 64));
}
```

https://github.com/llvm/llvm-project/pull/71400