[llvm] [llvm] Remove `br i1 undef` from regression tests (PR #117292)

[Lee Wei via llvm-commits]

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@@ -38,7 +42,7 @@ sw.bb:                                            ; preds = %entry
   unreachable
 
 sw.bb19:                                          ; preds = %entry
-  br i1 undef, label %if.then37, label %if.end50
+  br i1 false, label %if.then37, label %if.end50
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leewei05 wrote:

I saw that `%if.then27` is unreachable, so I replaced `undef` with `false`. Couldn't we do that since we already know that it cannot be branched to `%if.then27`? Do we usually leave the unreachable BB handle by the optimizer?

https://github.com/llvm/llvm-project/pull/117292