[llvm] [Bolt] Add a new hidden option to perf2bolt for testing purpose (PR #163785)

[Amir Ayupov via llvm-commits]

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@@ -440,6 +440,32 @@ class DataAggregator : public DataReader {
   /// B 4b196f 4b19e0 2 0
   void parsePreAggregated();
 
+  /// Detect whether the parsed line is an mmap event or not.
+  bool isMMapEvent(StringRef Line);
+
+  /// Coordinate reading and parsing a hybrid perf-script trace created by
+  /// the following Linux perf script command:
+  /// 'perf script --show-mmap-events -F pid,brstack --itrace=bl -i perf.data'
+  ///
+  /// Note:
+  /// The original perf.data should be profiled with '-b' or 'Arm Spe'.
----------------
aaupov wrote:

```suggestion
  /// The original perf.data should contain brstacks: either natively (with `-b` or `-j` flags), or synthesized with `--itrace` from trace sources.
```

https://github.com/llvm/llvm-project/pull/163785