[llvm] [WebAssembly] Demote PHIs in catchswitch BB only (PR #81570)

[Heejin Ahn via llvm-commits]

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@@ -245,7 +246,6 @@ bb.true:                                          ; preds = %entry
 bb.true.0:                                        ; preds = %bb.true
   br label %merge
 
-; CHECK:      bb.false
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aheejin wrote:

This was deleted because, in `llc` tests many passes run before `WinEHPrepare` and `WasmEHPrepare`, and some of them did some simplification of the CFG, removing this BB.

https://github.com/llvm/llvm-project/pull/81570