[llvm] [ADT] Add computeNumBuckets to DenseMap (NFC) (PR #168301)

[Sergei Barannikov via llvm-commits]

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@@ -1106,10 +1112,14 @@ class SmallDenseMap
     new (getLargeRep()) LargeRep{nullptr, 0};
   }
 
-  void grow(unsigned AtLeast) {
-    if (AtLeast > InlineBuckets)
-      AtLeast = std::max<unsigned>(64, NextPowerOf2(AtLeast - 1));
+  static unsigned computeNumBuckets(unsigned NumBuckets) {
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s-barannikov wrote:

Maybe rename the parameter to MinNumBuckets (or to AtLeast, the original name, not sure which one conveys the intent clearer)?

https://github.com/llvm/llvm-project/pull/168301