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

[Michael Maitland via llvm-commits]

michaelmaitland 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!

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