[llvm] [RISCV][GISEL] instruction-select for G_SPLAT_VECTOR (PR #111193)

[Craig Topper via llvm-commits]

================
@@ -67,7 +67,428 @@ define <vscale x 64 x i1> @splat_zero_nxv64i1() {
   ret <vscale x 64 x i1> zeroinitializer
 }
 
+define <vscale x 1 x i8> @splat_zero_nxv1i8() {
----------------
topperc wrote:

So it should be this combine

```
def extract_vector_element_not_const : GICombineRule<                            
   (defs root:$root),                                                            
   (match (G_INSERT_VECTOR_ELT $src, $x, $value, $idx),                          
          (G_EXTRACT_VECTOR_ELT $root, $src, $idx)),                             
   (apply (GIReplaceReg $root, $value))>
```

https://github.com/llvm/llvm-project/pull/111193