[llvm] [Coroutines] fix coroutines + std::unique_ptr with async exceptions validation errors (PR #149691)

[Weibo He via llvm-commits]

================
@@ -973,6 +975,178 @@ static StructType *buildFrameType(Function &F, coro::Shape &Shape,
   return FrameTy;
 }
 
+// This function assumes that it is being called on basic block in reversed
+// post-order, meaning predecessors are visited before successors failing to do
+// so will cause VMap to be non-valid and will cause instructions to fail
+// mapping to their corresponding clones
+static void finalizeBasicBlockCloneAndTrackSuccessors(
+    BasicBlock *InitialBlock, BasicBlock *ClonedBlock, ValueToValueMapTy &VMap,
+    SmallSet<BasicBlock *, 20> &SuccessorBlocksSet) {
----------------
NewSigma wrote:

We could use `SmallSetImpl` to avoid explicitly passing `20`.

https://github.com/llvm/llvm-project/pull/149691