[llvm] [gsymutil] Add `--statistics` option (PR #186495)

[Roy Shi via llvm-commits]

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@@ -435,6 +438,158 @@ void GsymReader::dump(raw_ostream &OS) {
   }
 }
 
+void GsymReader::dumpStatistics(StringRef GSYMPath, raw_ostream &OS,
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royitaqi wrote:

Clarification question about some uncovered bytes:
1. The `Size` and `Name` at the beginning of the `FunctionInfo` will not be covered. Where do you want to put them?  In my implementation, they are covered by `function_info_data.breakdown.overhead`.
2. The `Count` and the `FnSize` in the `MergedFunctionsInfo` will not be covered. Where do you want to put them?  In my implementation, they are covered by `merged_func_info.breakdown.overhead`.

FWIW, that's why I called them "overhead", because they not only cover end-of-list, but also those fields -  I used "overhead" for the lack of a better word.

https://github.com/llvm/llvm-project/pull/186495