[llvm] [RISCV] Add vector hasAndNot to enable optimizations (PR #132438)

[Piotr Fusik via llvm-commits]

pfusik wrote:

> Non blocking for this patch, but make sure you check the codegen for the fixed vector case too. We sometimes hit different lowering paths for fixed and scalable and I only see a scalable test changing here.

Thanks for pointing that out! Indeed there's a problem with fixed vectors here:

```
+define <8 x i8> @not_signbit_mask_v8i8(<8 x i8> %a, <8 x i8> %b) {
+; CHECK-LABEL: not_signbit_mask_v8i8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli zero, 8, e8, mf2, ta, ma
+; CHECK-NEXT:    vmsgt.vi v0, v8, -1
+; CHECK-NEXT:    vmv.v.i v8, 0
+; CHECK-NEXT:    vmerge.vvm v8, v8, v9, v0
+; CHECK-NEXT:    ret
+;
+; CHECK-ZVKB-LABEL: not_signbit_mask_v8i8:
+; CHECK-ZVKB:       # %bb.0:
+; CHECK-ZVKB-NEXT:    vsetivli zero, 8, e8, mf2, ta, ma
+; CHECK-ZVKB-NEXT:    vsra.vi v8, v8, 7
+; CHECK-ZVKB-NEXT:    vnot.v v8, v8
+; CHECK-ZVKB-NEXT:    vand.vv v8, v8, v9
+; CHECK-ZVKB-NEXT:    ret
+  %cond = icmp sgt <8 x i8> %a, splat (i8 -1)
+  %r = select <8 x i1> %cond, <8 x i8> %b, <8 x i8> zeroinitializer
+  ret <8 x i8> %r
+}
```

I'll debug it tomorrow.

I don't see any fixed vector tests for `vandn`. Is `vandn-sdnode.ll` the right file to add these in?

https://github.com/llvm/llvm-project/pull/132438