[llvm] AMDGPU: Migrate more tests away from undef (PR #131314)

[Pierre van Houtryve via llvm-commits]

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@@ -538,7 +538,8 @@ if.then:                                          ; preds = %entry
   ret void
 
 if.then9:                                         ; preds = %entry
-  br i1 undef, label %sw.bb18, label %sw.bb
+  %undef = freeze i1 poison
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Pierre-vh wrote:

Just for my own curiosity, when do you use `poison` vs `freeze poison`?
Is it because a branch with `poison` can be optimize out, but it can't be with `freeze poison`?

https://github.com/llvm/llvm-project/pull/131314