[llvm] [InstSimplify] Fix simplifyAndOrWithICmpEq with undef refinement (PR #98898)

[Nikita Popov via llvm-commits]

nikic wrote:

> re:
> 
> > Finally, make sure that places where AllowRefinement=false also use Q.getWithoutUndef(). I don't have a specific test case for this (the original one does not work because we don't simplify selects with constant condition in this mode in the first place) but this seems like the correct thing to do to be conservative.
> 
> What do you mean you don't have a test for this? Its a literal assert in the code? Do you mean you're not sure if this might trip?
> 
> Otherwise this seems sensible.

What I meant is that I don't have a test case what shows an undef miscompile for users of simplifyWithOpReplaced that use AllowRefinement=false.

https://github.com/llvm/llvm-project/pull/98898