[llvm] [ConstraintElim] LSHR x, n <= x when n< bitwidth (PR #209583)

[Florian Hahn via llvm-commits]

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fhahn wrote:

```suggestion
  br i1 %inrange, label %guarded, label %out
  
guarded:
  %h = lshr i64 %x, 1
  %chk = icmp ult i64 %h, %n
  ret i1 %chk
  
out:
```

nit: please add newlines between basic blocks.

You could also use llvm.assume o establish the precondition and avoid multiple blocks

https://github.com/llvm/llvm-project/pull/209583