[llvm] BlockFrequencyInfo: Add PrintBlockFreq helper (PR #67512)

[Fangrui Song via llvm-commits]

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@@ -108,6 +101,9 @@ class BlockFrequencyInfo {
   void verifyMatch(BlockFrequencyInfo &Other) const;
 };
 
+Printable PrintBlockFreq(const BlockFrequencyInfo &BFI, BlockFrequency Freq);
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MaskRay wrote:

Use `functionName` for new functions.

https://github.com/llvm/llvm-project/pull/67512