[llvm] [ADT] Fix the initial size calculation of SmallDenseMap (PR #158458)

[Jakub Kuderski via llvm-commits]

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@@ -905,7 +901,7 @@ class SmallDenseMap
 
   template <typename InputIt>
   SmallDenseMap(const InputIt &I, const InputIt &E) {
-    init(NextPowerOf2(std::distance(I, E)));
+    init(std::distance(I, E));
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kuhar wrote:

BTW, this is potentially expensive for forward iterators... Nothing to do with this PR though 

https://github.com/llvm/llvm-project/pull/158458