[llvm] [SimplifyCFG][NFC] Improve compile time for TryToSimplifyUncondBranchFromEmptyBlock optimization. (PR #110715)

[Nikita Popov via llvm-commits]

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@@ -1175,13 +1173,14 @@ bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
 
   // Even if we can not fold BB into Succ, we may be able to redirect the
   // predecessors of BB to Succ.
-  bool BBPhisMergeable =
-      BBKillable ||
-      CanRedirectPredsOfEmptyBBToSucc(BB, Succ, BBPreds, SuccPreds, CommonPred);
+  bool BBPhisMergeable = BBKillable || CanRedirectPredsOfEmptyBBToSucc(
+                                           BB, Succ, BBPreds, CommonPred);
 
   if ((!BBKillable && !BBPhisMergeable) || introduceTooManyPhiEntries(BB, Succ))
     return false;
 
+  SmallPtrSet<BasicBlock *, 16> SuccPreds(pred_begin(Succ), pred_end(Succ));
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nikic wrote:

I'd move this further down to where it's actually needed now.

https://github.com/llvm/llvm-project/pull/110715