[llvm] [RISCV] Widen i1 AnyOf reductions (PR #134898)

[Philip Reames via llvm-commits]

preames wrote:

I think you have a missing simplification in your input.  Can't this:
```
%phi = phi <vscale x 4 x i1> [ zeroinitializer, %entry ], [ %rec, %loop ]
  %cmp = icmp ...                                                          
  %or = or <vscale x 4 x i1> %phi, %cmp                                    
  %rec = call <vscale x 4 x i1> @llvm.vp.merge(TrueMask, %or, %phi, %evl)   
```

Be simplified to:
```
%phi = phi <vscale x 4 x i1> [ zeroinitializer, %entry ], [ %rec, %loop ]
  %cmp = icmp ...                                                          
  %rec = call <vscale x 4 x i1> @llvm.vp.merge(%cmp, TrueMask, %phi, %evl)   
```

https://github.com/llvm/llvm-project/pull/134898