[clang] [llvm] [SimplifyCFG] Hoist common code for switch multi-case destinations (PR #165700)

[Nikita Popov via cfe-commits]

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@@ -2156,9 +2164,13 @@ bool SimplifyCFGOpt::hoistSuccIdenticalTerminatorToSwitchOrIf(
       Updates.push_back({DominatorTree::Insert, TIParent, Succ});
   }
 
-  if (DTU)
-    for (BasicBlock *Succ : successors(TI))
+  if (DTU) {
+    // TI might be a switch with multi-cases destination, so we need to care for
+    // the duplication of successors.
+    SmallPtrSet<BasicBlock *, 4> UniqSuccs(llvm::from_range, successors(TI));
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nikic wrote:

Why can't we use the existing UniqSuccessors here and need to compute it again?

https://github.com/llvm/llvm-project/pull/165700