[llvm] [CVP] Check whether the default case is reachable (PR #79993)

[Nikita Popov via llvm-commits]

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@@ -407,6 +408,35 @@ static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
 
       // Increment the case iterator since we didn't delete it.
       ++CI;
+      ++ReachableCaseCount;
+    }
+
+    BasicBlock *DefaultDest = SI->getDefaultDest();
+    if (!isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg())) {
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nikic wrote:

I think it would be best to avoid this code if we already determined the only destination above.

https://github.com/llvm/llvm-project/pull/79993