[llvm] [Analysis] Avoid repeated hash lookups (NFC) (PR #126011)

[Nikita Popov via llvm-commits]

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@@ -1143,14 +1143,15 @@ void BlockFrequencyInfoImpl<BT>::calculate(const FunctionT &F,
 template <class BT>
 void BlockFrequencyInfoImpl<BT>::setBlockFreq(const BlockT *BB,
                                               BlockFrequency Freq) {
-  if (Nodes.count(BB))
+  auto [It, Inserted] = Nodes.try_emplace(BB);
+  if (!Inserted)
     BlockFrequencyInfoImplBase::setBlockFreq(getNode(BB), Freq);
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nikic wrote:

The getNode here is also a lookup in Nodes.

https://github.com/llvm/llvm-project/pull/126011