[ADT] Inline InsertIntoBucket and InsertIntoBucketWithLookup into their callers (NFC) (#155550)

InsertIntoBucket and InsertIntoBucketWithLookup each has exactly one
caller.  This patch inlines them into their respective sole callers,
reducing the line count.

While we are at it, this patch renames InsertIntoBucketImpl to
findBucketForInsertion to better reflect its purpose now that
InsertIntoBucket is being removed.

Author: kazutakahirata

llvm/include/llvm/ADT/DenseMap.h

@@ -279,8 +279,9 @@ class DenseMapBase : public DebugEpochBase {
       return {makeInsertIterator(TheBucket), false}; // Already in map.
 
     // Otherwise, insert the new element.
-    TheBucket = InsertIntoBucketWithLookup(TheBucket, std::move(KV.first),
-                                           std::move(KV.second), Val);
+    TheBucket = findBucketForInsertion(Val, TheBucket);
+    TheBucket->getFirst() = std::move(KV.first);
+    ::new (&TheBucket->getSecond()) ValueT(std::move(KV.second));
     return {makeInsertIterator(TheBucket), true};
   }
 
@@ -482,8 +483,9 @@ class DenseMapBase : public DebugEpochBase {
       return {makeInsertIterator(TheBucket), false}; // Already in the map.
 
     // Otherwise, insert the new element.
-    TheBucket = InsertIntoBucket(TheBucket, std::forward<KeyArgT>(Key),
-                                 std::forward<Ts>(Args)...);
+    TheBucket = findBucketForInsertion(Key, TheBucket);
+    TheBucket->getFirst() = std::forward<KeyArgT>(Key);
+    ::new (&TheBucket->getSecond()) ValueT(std::forward<Ts>(Args)...);
     return {makeInsertIterator(TheBucket), true};
   }
 
@@ -561,28 +563,9 @@ class DenseMapBase : public DebugEpochBase {
 
   void shrink_and_clear() { static_cast<DerivedT *>(this)->shrink_and_clear(); }
 
-  template <typename KeyArg, typename... ValueArgs>
-  BucketT *InsertIntoBucket(BucketT *TheBucket, KeyArg &&Key,
-                            ValueArgs &&...Values) {
-    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
-
-    TheBucket->getFirst() = std::forward<KeyArg>(Key);
-    ::new (&TheBucket->getSecond()) ValueT(std::forward<ValueArgs>(Values)...);
-    return TheBucket;
-  }
-
-  template <typename LookupKeyT>
-  BucketT *InsertIntoBucketWithLookup(BucketT *TheBucket, KeyT &&Key,
-                                      ValueT &&Value, LookupKeyT &Lookup) {
-    TheBucket = InsertIntoBucketImpl(Lookup, TheBucket);
-
-    TheBucket->getFirst() = std::move(Key);
-    ::new (&TheBucket->getSecond()) ValueT(std::move(Value));
-    return TheBucket;
-  }
-
   template <typename LookupKeyT>
-  BucketT *InsertIntoBucketImpl(const LookupKeyT &Lookup, BucketT *TheBucket) {
+  BucketT *findBucketForInsertion(const LookupKeyT &Lookup,
+                                  BucketT *TheBucket) {
     incrementEpoch();
 
     // If the load of the hash table is more than 3/4, or if fewer than 1/8 of