[llvm] Fix non-determinism in debuginfo (PR #68332)

[David Fang via llvm-commits]

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@@ -263,7 +265,8 @@ struct VarRecord {
 /// TODO: Backing storage shouldn't be limited to allocas only. Some local
 /// variables have their storage allocated by the calling function (addresses
 /// passed in with sret & byval parameters).
-using StorageToVarsMap = DenseMap<const AllocaInst *, SmallSet<VarRecord, 2>>;
+using StorageToVarsMap =
+    DenseMap<const AllocaInst *, SmallSetVector<VarRecord, 2>>;
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fangism wrote:

Can you add a comment explaining the choice of `SmallSetVector` and nondeterminism?  (Just so no one feels tempted to change it back.)

https://github.com/llvm/llvm-project/pull/68332