[llvm] [SimplifyCFG] Hoist common code when succ is unreachable block (PR #165570)

[Kunqiu Chen via llvm-commits]

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@@ -1866,10 +1866,19 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(Instruction *TI,
   // If either of the blocks has it's address taken, then we can't do this fold,
   // because the code we'd hoist would no longer run when we jump into the block
   // by it's address.
-  for (auto *Succ : successors(BB))
-    if (Succ->hasAddressTaken() || !Succ->getSinglePredecessor())
+  for (auto *Succ : successors(BB)) {
+    if (Succ->hasAddressTaken())
       return false;
-
+    if (Succ->getSinglePredecessor())
----------------
Camsyn wrote:

Moreover, should us relax this condition to support mutl-cases destination in `switch`?

```suggestion
    if (Succ->getUniqPredecessor())
```

https://github.com/llvm/llvm-project/pull/165570