[llvm] [ADT] Add a helper function to create iterators in DenseMap (NFC) (PR #155133)

[Kazu Hirata via llvm-commits]

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@@ -257,22 +257,13 @@ class DenseMapBase : public DebugEpochBase {
   std::pair<iterator, bool> try_emplace(KeyT &&Key, Ts &&...Args) {
     BucketT *TheBucket;
     if (LookupBucketFor(Key, TheBucket))
-      return std::make_pair(makeIterator(TheBucket,
-                                         shouldReverseIterate<KeyT>()
-                                             ? getBuckets()
-                                             : getBucketsEnd(),
-                                         *this, true),
+      return std::make_pair(makeInsertIterator(TheBucket),
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kazutakahirata wrote:

Ack.  Thank you for the review as always!  I'll create a follow-up PR.

https://github.com/llvm/llvm-project/pull/155133