[llvm] [PGO] Supporting code for always instrumenting loop entries (PR #116789)

[Christian Ulmann via llvm-commits]

================
@@ -52,10 +53,14 @@ template <class Edge, class BBInfo> class CFGMST {
 
   BranchProbabilityInfo *const BPI;
   BlockFrequencyInfo *const BFI;
+  LoopInfo *const LI;
 
   // If function entry will be always instrumented.
   const bool InstrumentFuncEntry;
 
+  // If true loop entries will be always instrumented.
----------------
Dinistro wrote:

```suggestion
  /// If true loop entries will be always instrumented.
```

I'm aware that other parts of this file do not follow the style guide, so maybe it's better to stay consistent instead. 

https://github.com/llvm/llvm-project/pull/116789